the classical pathways of occipital lobe epileptic ...822232/fulltext01.pdf · researcharticle the...

Research ArticleThe Classical Pathways of Occipital Lobe Epileptic PropagationRevised in the Light of White Matter Dissection

Francesco Latini1 Mats Hjortberg2 Haringkan Aldskogius3 and Mats Ryttlefors1

1Department of Neuroscience Section of Neurosurgery Uppsala University Hospital 75185 Uppsala Sweden2Department of Medical Cell Biology Uppsala University Uppsala Sweden3Department of Neuroscience Regenerative Neurobiology Uppsala University Uppsala Sweden

Correspondence should be addressed to Francesco Latini francescolatinineurouuse

Received 12 March 2015 Accepted 20 April 2015

Academic Editor Francesco Pisani

Copyright copy 2015 Francesco Latini et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

The clinical evidences of variable epileptic propagation in occipital lobe epilepsy (OLE) have been demonstrated by several studiesHowever the exact localization of the epileptic focus sometimes represents a problem because of the rapid propagation to frontalparietal or temporal regions Each white matter pathway close to the supposed initial focus can lead the propagation towards aspecific direction explaining the variable semiology of these rare epilepsy syndromes Some new insights in occipital white matteranatomy are herein described by means of white matter dissection and compared to the classical epileptic patterns mostly basedon the central position of the primary visual cortex The dissections showed a complex white matter architecture composed byvertical and longitudinal bundles which are closely interconnected and segregated and are able to support specific high orderfunctions with parallel bidirectional propagation of the electric signalThe same sublobar lesions may hyperactivate different whitematter bundles reemphasizing the importance of the ictal semiology as a specific clinical demonstration of the subcortical networksrecruited Merging semiology white matter anatomy and electrophysiologymay lead us to a better understanding of these complexsyndromes and tailored therapeutic options based on individual white matter connectivity

1 Introduction

Firstly described in 1879 in a patient with a parieto-occipitaltumour [1] occipital lobe epilepsy (OLE) is still nowadaysconsidered a rare condition that represents less than 2ndash13of extratemporal epilepsies [2ndash5]

Typical symptoms of OLE are visual auras andor ele-mentary visual hallucinations (EVHs) ictal blindness con-tralateral eye and head deviation eye movement sensationsblinking and eyelid fluttering [6ndash9] Despite this commonlyaccepted semiology the diagnosis remains a problem in somecases The seizure onset in the posterior cortex (parietaloccipital and posterior temporal lobe) may be difficult toprove with surface electroencephalographic techniques Theepileptic propagation tends to spread rapidly to other regionsin the brain up to 50 of the cases [10 11] especially towardstemporal and frontal areas [7 12 13] and for this reason (thesemiology) is sometimes misinterpreted

For a definitive discrimination of OLE invasive video-EEG monitoring using intracranial subdural andor depthelectrodes is often necessary [9 14ndash16]

Decision making for surgical treatment of drug-resistantOLE patients depends mainly on the existence of a structurallesion visible on magnetic resonance imaging (MRI) Goodresults are also reported with partial resection of dysplasticlesions and in some cases a favourable outcome is describedin patients with a normalMRIwho underwent surgical resec-tions guided by intracranial electrodes monitoring [11 17 18]The white matter connectivity seems to play a crucial role inboth epileptic patterns and tailored therapeutic options

A crucial role of the primary visual cortex has beenemphasized for a long time in OLE and the relationshipbetween the localization of the epileptic focus and thecalcarine fissure seemed to determine the site and type ofseizure spread [11 13 19] The inferior longitudinal fasci-culus (ILF) and inferior fronto-occipital fasciculus (IFOF)

Hindawi Publishing CorporationBehavioural NeurologyVolume 2015 Article ID 872645 10 pageshttpdxdoiorg1011552015872645

2 Behavioural Neurology

are still classically described as the two main white matterbundles responsible for facilitating the epileptic propagationin OLE because of their close spatial relationship withthe optic radiation and the primary visual cortex (V1)[18 20]

For this reason the most common concern in occipitallobe surgery is aggravation of existing or creation of newvisual field defects so despite the successful results achievedwith epilepsy surgery in both adults and children [11 21ndash24]reports of such resections in the literature are rare (lt5 ofpatients) [17 25ndash27]

Encouraging data from tailored resection in OLE seem tohave important implications for the decision making and theexpected quantitative damage to the visual pathways [9 2324 28] It seems that a more specific sublobar categorizationof the resection within the occipital lobe may support a moreselective disconnection of the segregated and hyperactivatedbundles underlying the occipital area

The aim of this paper is to discuss the classical path-ways of occipital epileptic propagation in the light of newinsight in white matter (WM) connectivity in order tobetter understand the complex hierarchical segregation of theoccipital white matter and the different direction of epilepticpropagation with its crucial surgical implications

2 Methods

Ten cerebral hemispheres obtained from human cadaversdonated to the Department of Medical Cell Biology Sectionfor Anatomy studies at Uppsala University were enrolled inthis study All individuals donating had given written consentfor use of the whole cadaver for biomedical research andeducation in a testimonial donation letterThe study protocolwas filed with the application for ethical vetting of researchinvolving humans to the local ethical review board inUppsala(Dnr 2014468)

Each brain was fixed with intra-arterial injection of12 formalin solution within the first week after deathusing a perfusion device After this procedure the brainswere then carefully extracted and put in 10 formalin forat least 24 hours The pia mater arachnoid membraneand vascular structures were then carefully removed undermicroscopic magnification and the hemispheres were frozenat minus15∘Cndashminus20∘C for 6ndash10 days and then slowly defrostedfor 12 hours Before the start of dissection the superficialanatomy of the sulci and gyri was studied in detail Thespecimens were dissected in a stepwise manner from lateralsurface to the medial structures and from mesial and basalsurface to the ventricle with a modified fiber dissectiontechnique with respect to the technique described by Latini[29] Microscopic metal dissectors and thin wooden spatulaswere used in the initial steps of the dissection to split orpartially peel away the brain cortex preserving the mostsuperficial intracortical and subcortical fibres of the lateralbasal and mesial surface of the brain Subcortical intralobarassociative and projection fibres were exposed until the opticradiation (OR) on lateral and basal dissection and until thecallosal-tapetal fibres on the mesial surface of the occipitallobe in each specimen The dissections were performed

under microscopic magnification (up to 4x) Between eachdissection session the specimens were placed in 5 formalin

3 Results

31 Dissection of the Lateral Surface The dissection of thelateral surface started with the exposure of the indirect(vertical) component of the superior longitudinal fasciculus(vSLF) (Figure 1(a))This bundle which connects the angulargyrus (AG) to the region of the temporo-occipital junction onthe lateral surface was considered the anterior and superficialedge to the occipital connectivity in our dissections Medialto the vSLF the arcuate fasciculus (AF) was exposed withits c-shaped course connecting the infero-lateral temporo-occipital (T-O) region to the perisylvian region and frontallobe (Figure 1(b)) Posterior to vSLF and AF the verticaloccipital fasciculus (VO) was exposed (Figures 1(a)-1(b))This bundle runs from the superior occipital gyrus with anoblique and caudal direction to the fusiform gyrus Deeperand more posterior with respect to the vertical occipitalfasciculus the dorsal terminations of the inferior longitudinalfasciculus (dILF) were exposed at the level of the dorsolateraloccipital cortex (DLOC) and just below the parieto-occipitalsulcus (POS) in the cuneal region This portion of the ILFcomplex runs lateral and inferior to the sagittal stratumof Sachs (SSS) until the infero-lateral part of the temporalpole partially overlapping at this level with arcuate fasciculusterminations [29ndash31] (Figure 1(c)) At the level of cuneal area(Cu) the dILF fibres cover part of the posterior terminationsof the middle longitudinal fasciculus (MLF) which runsfrom the parieto-occipital sulcus region within the SSS andmedially to the AF to the white matter underneath thesuperior temporal gyrus [32] Medial to the MLF at the levelof the external capsule (ExC) the inferior fronto-occipitalfasciculus (IFOF) was isolated as classically described [3133 34] (Figure 2(a)) Medial to the IFOF within the sagittalstratum of Sachs and caudal to the temporal portion oflateral ventricle the optic radiation (OR) and the Meyerrsquosloop (MeL) were exposed completely until the visual cortexposteriorly (Figure 2(b))

32 Dissection of the Ventral Surface Once the ldquoUrdquo fibreshave been removed from the fusiform subcortical region atthe level of collateral sulcus a ventral branch of inferiorlongitudinal fasciculus (vILF) was isolated (Figure 3(a))These fibres arising from the posterior occipito-temporalgyrus are located inferiorly and medially to the dILF IFOFand sagittal stratumpreviously describedThis ventral branchruns from posterior and basal occipital region forward andslightly laterally until the temporal pole following the courseof lateral ventricleThis ventral pathway represents the infero-lateral wall of lateral ventricle for its entire course andbeyond the temporal horn it reaches the subcortical regionof parahippocampal gyrus (PHG) and then into the temporalpole (TP)

Deeper and more medial to the vILF the lingula-amygdaloid (Li-Am) bundle was exposed From the lingualcortex these fibres describe an arch-shaped bundle that follow

Behavioural Neurology 3

POS

hSLF

vSLF

VO

(a)

POS

VO AF

hSLF

(b)

POSAF

SSSdILF

Cu

DLOC

Ins

(c)

POS AF

MLF

SSS

dILF

Cu

DLOCTP

STG

M1

(d)

Figure 1 (a) Lateral view of a right hemisphere after the dissection of the superficial white matter layers of temporo-parieto-occipitalregion The first bundle identified is the vertical component of the superior longitudinal fasciculus (vSLFdark blue) which connects thesupramarginal gyrus and angular gyrus to the temporo-occipital junction Posterior to the vSLF the vertical occipital fasciculus (VOlightblue) connects the superior occipital gyrus to the fusiform gyrus At the level of the supramarginal gyrus the vSLF partially overlaps withthe horizontal component of SLF (hSLFpurple) which runs from the parietal region to the frontal region (b) After vSLF has been removedthe arcuate fasciculus (AFcyan) is exposed running from the frontal region through the perisylvian region with white matter terminationsunderneath the temporo-occipital junction and it ends at the level of the middle and inferior temporal gyrus (c) The temporal terminationsof the AF are overlapping with the temporal portion of the dorsal inferior longitudinal fasciculus (dILFlight blue)The AF has been retractedcompletely exposing the course of dILF The cuneal (Cu) branch and the dorsolateral occipital cortex portion (DLOC) run in one bundle(dILF) at the level of the temporo-occipital junction lateral to the SSS and straight to the temporal pole area (d) Medial to the AF the middlelongitudinal fasciculus (MLForange) is exposed at the connection between the posterior insular cortex (Ins) and the superior temporal gyrus(STG) This bundle runs from the superior temporal gyrus within the sagittal stratum of Sachs (SSS) to the parieto-occipital sulcus region(POS) At the level of the cuneal region (Cu) the dILF terminations are partially overlapping theMLF terminationsM1 primary motor cortex(precentral gyrus) Ins insula TP temporal pole

the other ventral pathway until the temporal horn whereit turns around the tip of the temporal horn reaching thebasolateral portion of the amygdaloid region (Figure 3(b))[29] Deeper with respect to the Li-Am the optic radiationcan be completely exposed on its ventral view until theprimary visual cortex (V1) (Figure 3(c))

33 Dissection of the Medial Surface Removing the cortexsubcortex and short fibres of the cingulate gyrus exposes agroup of fibres projecting in a longitudinal direction paralleland above the corpus callosum that forms the cingulum(Ci) At the level of the isthmus where the commissuralfibres of the forceps major cross in front of the cingulumfibres a horizontal component of the cingulum runs straightto cuneal-precuneal medial region (Figure 4(a)) Below thislevel the cingulum courses near the most anterior part ofthe optic radiations and covers the inferior lip of the anterior

part of the calcarine sulcus Removal of the cingulum exposesthe corpus callosum from the genu and rostrum anteriorlyto the splenium posteriorly At the level of the spleniumthe fibres take a posterior oblique direction forming theforceps major which interconnects the parieto-occipital andcalcarine regions (Figure 4(b)) The more lateral componentof the callosal fibres represents the lateral wall of the trigoneand atrium reaching in a curvy shape the medial occipitalsurface cranial and anteriorwith respect to the optic radiationcourse (Figure 4(c))

4 Discussion

The clinical evidences of variable epileptic propagation inOLE have been demonstrated in several studies with neuro-physiological [36ndash39] and metabolic data (positron emissiontomography (PET)) [9 17 40] According to some recent


POSAF

IFOFCu

PreCu

OPLi

ExC

M1

(a)

AF

SSS

ORIC

V1V2V3

(b)

Figure 2 (a) Lateral view of the right hemisphere once the MLF and the insular cortex have been resected The Inferior fronto-occipitalfasciculus (IFOF) is completely exposed at the level of the external capsule (ExC) The posterior originating branches run from precuneus(PreCu) cuneus (Cu) occipital pole (OP) region and lingula (Li) within the sagittal stratum of Sachs (SSS) towards the frontal lobe Lightblue dotted lines represent the spatial distribution of the posterior termination of the IFOF (b) After the resection of the IFOF on the lateralsurface of the brain the optic radiation (OR) is exposed within the deep part of the SSS According to Alvarez et al [35] the dark blue linerepresents the anterior margin of the dorsal component of the OR which will end at the level of the dorsal portion of extrastriate visualcortices (V2 and V3) The orange dotted line represents the anterior margin of the ventral component of the OR fibres that runs inferiorlyand lateral with respect to the lateral ventricle to end at the level of primary visual cortex (V1)M1 primary motor cortex (precentral gyrus)IC internal capsule AF arcuate fasciculus fibres left as superficial landmark

Fu

AF

vILF

SSSdILF

OPLi

DLOC

BS

PHG

Un

(a)

HB

AFLiAmSSS

OPLi

HHBS

Am TPTa

(b)

V1

AF

IC

OR

SSS

MeLHH

(c)

Figure 3 (a) Basal view of the right hemisphere showing the ventral portion of the ILF (vILF) with its double originating branches fromthe fusiform gyrus (Fu) and superficial lingual gyrus (Li) The bundle connects these two posterior basal regions to the parahippocampalgyrus (PHG) (b) Basal view of a right hemisphere after the removal of the dILF and vILF The lingual-amygdala bundle (Li-Amgreen)is completely exposed and its relationship with the ventricle and the sagittal stratum of Sachs (SSS) cranially is demonstrated The Li-Amconnects the lingual gyrus (Li) in an arch shaped bundle which follows the wall of the lateral ventricle and at the level of the tip of thetemporal horn turns medial to terminate in the inferolateral portion of the amygdala (Am) (c) Inferolateral view of a right hemisphere withthe optic radiation (OR) completely exposedThe temporal loop of Meyer (MeL) is prominent anteriorly with respect to the other fibres Theoptic radiation fibres run within the internal layer of the sagittal stratum of Sachs (SSS) inferior and lateral to the lateral ventricle and turnmedially to end at the level of the primary visual cortex (V1) The arcuate fasciculus (AF) and the internal capsule (IC) can be consideredas superficial and deep landmarks respectively AF arcuate fasciculus BS brain stem HB hippocampus body HH hippocampus head OPoccipital pole Ta tapetal fibres TP temporal pole Un uncus


POS

CF

Ci-FMSpFo

Pc

CcCi

CiR

Ac

PreCu

Li

Tha

Mb BSUn

PHG

Cu

(a)

POS

CF

CaRSp

FoPc

FM

vILFORChP

Li

TPDeGy

Cu

OP

(b)

POS

CFFMSp

TaOR

Li OP

ChP

Cu

(c)

Figure 4 (a)Medial view of a right hemisphere after the initial dissection of cortex of the cingulate gyrusThewhole cingulum (Ci) is exposedwith its extension from the subcallosal area to the parahippocampal gyrus (PHG) as the radiation of cingulum (CiR) until the region of theuncus Posterior with respect to the splenium (Sp) of the corpus callosum (CC) a posterior component of the Ci reaches the cuneal andprecuneal cortices forming the most medial part of the forceps major (FM) (b) After the removal of the Ci and further dissection of theCC the radiating callosal fibres (CaR) can be demonstrated Once the hippocampus and the PHG have been removed the lateral ventricle isopened with choroid plexus (ChP) shown at the medial portion of the trigone The medial wall of the trigone is composed of callosal fibresof the FM which end close to the optic radiation (OR) fibres on both sides of the calcarine fissure (CF) (c) The medial wall of the ventricleis opened cutting the FM fibres in order to expose the tapetal callosal fibres which run within the lateral wall of the ventricle composingthe deepest layer of the sagittal stratum of Sachs (SSS) The tapetal fibres end following the OR fibres on the medial surface of the cunealand lingual regions partially overlapped with the dorsal component of OR Fo fornix Ac anterior commissure Pc posterior commissureMb mammillary body BS brain stem Tha thalamus TP temporal pole Un uncus DeGy dentate gyrus POS parieto-occipital sulcus CFcalcarine fissure PreCu precuneus Cu cuneus Li lingula OP occipital pole

series on surgical treatment of OLE the position within theoccipital lobe of an epileptic onset or the presence of a discretelesion results in a specific pattern and semiology [9ndash18 20 2324 41]

Even if visual aura is one of the hallmarks of OLEdescribed in up to 69 of the cases in some series [9 23 2426 41ndash43] there is a significant spatial correlationwith lateraland basal lesions with respect to the medial ones Accordingto the literature elementary visual symptoms either positive(flashes and phosphenes) or negative (scotoma hemianopsiaand amaurosis) are usually considered due to the stimulationor inhibition of the primary visual cortex and optic radiation[20 44 45] The more the surrounding cortices are involvedin the epileptic pattern the visual symptoms usually becomemore complex with hallucinations illusions and delusions[8 46 47]

If we try to interpret the semiology of the OL seizuresthrough the common reported patterns types we may arguethat partial seizures with only occipital symptoms (such asseeing flashing lights or presented amaurosis) are basically

restricted to the hyperactivation of the occipital intralobarconnectivity Dialeptic seizures altered awareness associatedto manual andor alimentary automatisms with or withoutepigastric aura reflect the temporal spread of the epilepticpropagation Early motor semiology such as tonic activity orhyperactive automatisms secondary generalized tonic-clonicconvulsions or rapid eye blinking or eyelid fluttering andorsensation of eye movement without any other movement areoften reported as manifestation of seizure with frontal lobeinvolvement [8 9 23 24 41]

41 The Classical Pathways Revised In the past the differentdirection of the occipital epileptic patterns was classicallyrelated to the spatial relationship with the calcarine sulcusFor instance medial occipital electric activity arising abovethe calcarine fissure usually propagates to the frontal lobewhile medial occipital electric activity arising below thecalcarine fissure can propagate to the mesial temporal lobe[11 19 20] Lateral occipital seizures would spread accordingto this theory to the parietal and lateral temporal lobes [13]


The functional connectivity of the occipital lobe issupported by projection pathways which work in a serialactivation and associative and commissural bundles thatwork in parallel networks

The optic radiation is the prominent projection pathwayin the visual system conveying information from the lateralgeniculate nucleus (LGN) with a specific direction towardsthe occipital region Recent insights in tractographic segmen-tation of the optic radiation confirm in humans the existenceof straight connection from LGN not only to V1 but also tothe dorsal portion of the extrastriate visual corticesV2 andV3[35] This organization could explain the important numberof elementary visual hallucinations (EVHs) like flashinglights or amaurosis due to the involvement of optic radiationeven in just the dorsal portion of V2 and V3 [17 20 23] Evenif more detailed in the hierarchical segregation of the opticradiation fibres however the emphasized position of V1 canonly partially confirm the classical description of the otherOLE patterns

From an anatomical point of view the inferior longitu-dinal fasciculus and the inferior fronto-occipital fasciculushave been classically considered the two major associativepathways responsible for the epileptic propagation in OLEto temporal and frontal areas probably because of theirclose relationship with the optic radiation within the sagittalstratum of Sachs (Figure 5) However from a functionalpoint of view several other white matter bundles may beresponsible for the variable semiology of OLE

Our dissection confirmed that the white matter connec-tivity of the occipital region is based on a very complexarchitecture with several longitudinal and vertical bundlesclosely interconnected on themesial lateral and basal surfacewith a hierarchical segregation that may support the differentdirections of the epileptic propagation

42 Dorsal Epileptic Pathways According to the classicaltheory of Williamson and Bancaud [11 19] an epileptic onsetabove the calcarine fissure from medial extrastriatal cortices(cuneal) would preferentially spread to frontal regions A rea-sonable propagated onset through the IFOF terminations tothe supplementarymotor area (SMA) dorsolateral prefrontalcortex (DLPFC) and orbitofrontal cortex (OFC) would leadto clonic andor tonic contraversion of the eyes and head oreyes only forced closure of the eyelids and palpebral jerksHowever the dissection of the cuneal region showed otherpotential pathways that can be recruited by similar lesions onboth medial and lateral portion On the medial surface thefibres of the cingulum at the level of the cuneal-precunealregion can lead the epileptic propagation both to bothfrontal and temporo-mesial regions The hyperactivation ofthis pathway with a frontal direction may explain the rapidsecondary generalization to tonic-clonic seizures while thetemporo-mesial spread would support the role of this bundlein memory retrieving (Jamais vu and deja vu) describedin patients with mesial-cuneal occipital lesions [20 23 41]Between the cingulum and the optic radiation the posteriorcommissural and the callosal fibres of the forceps majorrepresent a fast interhemispheric pathway able to propagatethe electric signal to the contralateral side with a subsequent

PreCu

Ag

CuCc

LiOp

Dloc

Figure 5 Artistic illustration of the white matter connectivityunderlying the occipital region The illustration shows a schematicreconstruction from a posterior coronal view the occipital regionwith all the major white matter bundles dissected and shown withdifferent colours through the cortical layer This illustration servesto summarize the complex subcortical organization which can besignificantly correlated to the semiology of the seizures involvingeach sublobar occipital region A lesion on the lateral surface of theoccipital lobe or at the temporo-occipitalparieto-occipital junctionwould probably spread to the parietal and frontal regions The ver-tical component of the superior longitudinal fasciculus (vSLFred)arcuate fasciculus or the horizontal superior longitudinal fasciculus(AFyellow hSLFlight green) and the vertical occipital fasciculus(VOgray) can support this direction of propagation Deep lesionsmay involve different pathways within the sagittal stratum of Sachs(SSS) such as inferior longitudinal fasciculus (ILForange) middlelongitudinal fasciculus (MLFpink) inferior fronto-occipital fasci-culus (IFOFlight blue) or even the optic radiation (ORdark green)According to the hierarchical segregation of the fibres the epilepticpropagation would spread to temporo-lateral areas temporo-mesialareas andor frontal lobe Moreover a possible epileptic lesionin a dorsal-mesial location with respect to the OR and calcarinefissure would involve fibres of the cingulum (Cidark red) andcallosal fibres of the forceps major-tapetum (Tadark blue) witha resultant ipsilateral andor contralateral epileptic propagationFinally ventral-mesial deep lesions located below the calcarinefissure can involve the ventral portion of the IFOF (light blue) witha fast propagation to the frontal lobe or can recruit the ventralportion of the ILF (orange) and Li-Am bundle (LiAmpurple) witha fast temporo-mesial involvement (see the text for the functionalconsiderations) Ag angular gyrus Cc corpus callosum Cu cuneusLi lingula PreCu precuneus Op occipital pole

possible secondary recruitment of temporal andor frontalregions The prolonged and abnormal activation of thesepathways may be responsible for the appearance of the so-called ldquomirror focusrdquo on the contralateral hemisphere inintractable epilepsy [48]

Lateral to the optic radiation and the inferior fronto-occipital fasciculus occipital terminations within the SSSthe middle longitudinal fasciculus (MLF) can be responsiblefor the fast epileptic spread to lateral temporal region


Reported symptoms like tinnitus vertigo and vertiginousvisual sensations can be due to the epileptic propagation tothe posterior portion of superior temporal gyrus through theMLF fibres More lateral and inferior with respect to the mid-dle longitudinal fasciculus cuneal terminations of the dILFcan support the onset with the visual aura reported in fewmedial lesions [9 20 23 24] The dILF with its double origin(cuneal and dorsolateral occipital cortex) may facilitate theconvergence of the spreading from both lateral and medialareas to the occipito-temporal lateral areas and temporal poleSimple illusions may be supported by this bundle withinthe temporo-occipital region Objects can be described asdistorted and eventually changed in size (macropsia ormicropsia) shape (metamorphopsia) illumination colouror clarity Lines may appear wavy (dysmorphopsia) objectsmay appear inclined (plagiopsia) and there may be a loss ofcolour (achromatopsia) [8 46 47]

43 Lateral Epileptic Pathways Lateral occipital epilepticonset with respect to the V1 was classically associated toparietal propagations [11 19 20] According to the whitematter connectivity of the parieto-occipital (PO) region wemay argue that this classical pattern is at least incomplete fortwo reasons

First a parietal recruitment can easily lead to a frontalpropagation with early sensory-motor semiology Frontalinvolvement can indeed occur in a parallel manner forboth medial and lateral occipital lesions [9 20 23 2441] Particularly in cases of associated numbness to thecontralateral hemibody [20] a perisylvian propagation canbe hypothesized trough the AFSLF complex which connectsthe extrastriate (V4-V5) lateral cortices through the parietalregion (angular gyrus (AG)) and then to premotor andmotorcortical areas In particular this pathways end in the frontaleye fields (FEF) the supplementary eye fields (SEF) andthe dorsolateral prefrontal cortex (DLPC) The facilitatedpropagation through this so-called dorsal visual stream theldquoWhererdquo stream [49] may be responsible for complex visualhallucinations and illusions or postictal negative symptomssuch as the inability to revisualize objects or scenes (disordersof mental imagery) strange or unreal visual experiences (de-realization) out-of-body experiences or motion hallucina-tions [46]

The second reason is that not only a lateral occipital onsetcan preferentially spread to parietal and then frontal areasbut also temporo-occipital basal lesions can show a parietalrecruitment during the epileptic propagation On this notethe vertical occipital fasciculus can represent a parallel hyper-activated pathway supporting the parietal propagation frommore basal onset involving the fusiform gyrus This addi-tional connection between basal and lateralparietal regioncould represent an anatomical-functional bridge betweenthe ldquoWhatrdquo ventral pathway and the ldquoWhere-Howrdquo dorsalpathways for vision [49] Hence complex hallucinations andillusions both involvingwords and images could be supportedby this white matter pathway [50]

44 Ventral Epileptic Pathways Based on the surgical resultsfor lesions involving the infero-lateral surface the specific

epileptic propagation to the anterior and lateral temporalregions could be supported by the segregated longitudinalWM architecture of this area [9 20 23 24 41] Not inall the cases the mesial areas are involved by the epilepticpropagation differently from classical theory regarding therelationship with the calcarine fissure [11 19] The analysisof seizures semiology in this area so rich in specializedcortical regions (lateral infero-temporal multimodal area(LIMA) [51] visual word form area (VWFA) [52 53] corticesactivated by several visual inputs such as face (fusiform facearea (FFA)) object (visual object form area (VOFA)) housesanimals (lateral occipital LO and V3ndashV7) [54]) can giveus important information about the intrinsic white matterconnections involved in the temporal propagation patternFor instance face hallucinations and illusions characterizedby distorted facial features (prosopometamorphopsia) arelikely to relate to a region specialized for face features onthe lateral convexity of the occipital lobe (occipital facearea subserved by the dILF) while hallucinations of normalfaces or facial intermetamorphosis (a change in the visuallyperceived identity of a face) are likely to relate to activitywithin an area specialized for faces on the ventral occipito-temporal surface (fusiform face area subserved by the vILF)[55] In our opinion simple illusions like macropsia ormicropsia metamorphopsia illumination colour or clar-ity dysmorphopsia plagiopsia and achromatopsia may beexplained by the loss of balance of this longitudinal temporo-occipital network On the other hand a propagation fromthe basal region to the lateral occipital and parietal region(through the VO vSLF and AF) would create complexillusions like objects that appear disorientated in distance(macroproxiopia microtelepsia) or be distant and minute(teleopsia) or that have a loss or enhancement of stereoscopicvision or even persistent or recurrent (palinopsia) (see [6ndash8]for reviews)

However if the seizure spreads to the mesial temporallobe such as the parahippocampal gyrus (PHG) automatismsand impaired awareness may occur [8 38] and according tothe white matter architecture of this area the vILF may beresponsible for this semiology More medial and deeper tothe vILF the Li-Am bundle represents a direct connectionbetween the lingual gyrus and the basolateral portion of theamygdaloid region Confirming the already reported dataabout the fast activation of amygdaloid region and extras-triatal visual cortices [36 37] this fast and short connectionmay explainwhymanypatients [20 56]with lesions involvingthe lingual gyrus experience an ictal semiology of fear andanxiety

To summarize this paper supports the description ofa very complex white matter architecture underneath theoccipital region Considering each possible direction of elec-tric propagation we describe different anatomical pathwayswhich may support in parallel the spread from extrastriatalcortices to frontal parietal or temporal regions All thisconnectivity is supported by white matter bundles that areclosely interconnected with partially overlapping termina-tions Moreover each pathway except the OR represents abidirectional network and for this reason able to repropagatethe epileptic signal back to the other extrastriate cortices On


this note according to the incredible number of patients withvisual aura and to the absence of this phenomenon withinthe primary visual cortex we may claim that visual auracan be facilitated by the hyperactivation of the associativepathways once the epileptic propagation is directed back tothe occipital region andor enhanced by the short intralobarfiber systems This mechanism may be valuable also inexplaining the visual symptoms (either simple or complex)reported in patients with a confirmed extraoccipital epilepticfocus (frontal temporal or parietal) [26 57ndash61]

Fort this reason even if complex the possibility to predictor specifically localize theway of epileptic propagation shouldalways be based on the match between the semiology and theunderlying white matter pathways

Further studies should merge clinical neurophysiologi-cal neuroradiological and anatomical data in order to definethe best therapeutic options minimizing complications inpatients with OLE

5 Conclusion

New insights into the occipital white matter architecturesupport a more complex functional connectivity based onboth vertical and longitudinal bundles which are specializedsegregated and interconnected and are able to propagatethe electric signal bidirectionally A more comprehensiveunderstanding of the occipital white matter connectivitymerged with neuroradiological functional and neurophysi-ological studies may better clarify the incredible variability ofsymptoms related to an epileptic onset in the occipital region

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

The authors thank Dr Roberta Schivalocchi (neurosurgeonand artist affiliated with the Department of Neurosciencesand Rehabilitation at S Anna University-Hospital FerraraItaly) for the tireless and enthusiastic support and for theextreme courtesy in providing the exceptional artistic illus-tration shown in the paper

References

[1] W R Gowers ldquoCases of cerebral tumour illustrating diagnosisand localisationrdquo The Lancet vol 113 no 2898 pp 363ndash3651879

[2] P Loiseau B Duche and J Loiseau ldquoClassification of epilepsiesand epileptic syndromes in two different samples of patientsrdquoEpilepsia vol 32 no 3 pp 303ndash309 1991

[3] M Manford Y M Hart J W A S Sander and S D ShorvonldquoNational General Practice Study of Epilepsy (NGPSE) partialseizure patterns in a general populationrdquoNeurology vol 42 no10 pp 1911ndash1917 1992

[4] A T Berg S Shinnar S R Levy and F M Testa ldquoNewly diag-nosed epilepsy in children presentation at diagnosisrdquo Epilepsiavol 40 no 4 pp 445ndash452 1999

[5] P Jallon P Loiseau and J Loiseau ldquoNewly diagnosed unpro-voked epileptic seizures presentation at diagnosis in CAROLEstudyrdquo Epilepsia vol 42 no 4 pp 464ndash475 2001

[6] F E Dreifuss ldquoProposal for classification of epilepsies andepileptic syndromes Commission on classification and termi-nology of the international league against epilepsyrdquo Epilepsiavol 26 pp 268ndash278 1985

[7] S Sveinbjornsdottir and J S Duncan ldquoParietal and occipitallobe epilepsy a reviewrdquo Epilepsia vol 34 no 3 pp 493ndash5211993

[8] I Taylor I E Scheffer and S F Berkovic ldquoOccipital epilepsiesidentification of specific and newly recognized syndromesrdquoBrain vol 126 no 4 pp 753ndash769 2003

[9] P F Yang Y Z Jia Q Lin et al ldquoIntractable occipital lobeepilepsy clinical characteristics surgical treatment and a sys-tematic review of the literaturerdquo Acta Neurochirurgica (Wien)vol 157 no 1 pp 63ndash75 2015

[10] V Salanova F Andermann A Olivier T Rasmussen and LF Quesney ldquoOccipital lobe epilepsy electroclinical manifesta-tions electrocorticography cortical stimulation and outcome in42 patients treated between 1930 and 1991 surgery of occipitallobe epilepsyrdquo Brain vol 115 no 6 pp 1655ndash1680 1992

[11] P DWilliamson V MThadani T M Darcey D D Spencer SS Spencer and R H Mattson ldquoOccipital lobe epilepsy clinicalcharacteristics seizure spread patterns and results of surgeryrdquoAnnals of Neurology vol 31 no 1 pp 3ndash13 1992

[12] F Boesebeck R Schulz T May and A Ebner ldquoLateralizingsemiology predicts the seizure outcome after epilepsy surgeryin the posterior cortexrdquo Brain vol 125 no 10 pp 2320ndash23312002

[13] P D Williamson ldquoSeizures with origin in the occipital orparietal lobesrdquo in Epileptic Seizures and Syndromes P Wolf Edpp 383ndash390 John Libbey 1994

[14] H Clusmann T Kral and J Schramm ldquoPresent practiceand perspective of evaluation and surgery for temporal lobeepilepsyrdquo Zentralblatt fur Neurochirurgie vol 67 no 4 pp 165ndash182 2006

[15] T Kral H Clusmann J Urbach et al ldquoPreoperative evaluationfor epilepsy surgery (Bonn algorithm)rdquo Zentralblatt fur Neu-rochirurgie vol 63 no 3 pp 106ndash110 2002

[16] A Palmini F Andermann F Dubeau et al ldquoOccipitotemporalepilepsies evaluation of selected patients requiring depth elec-trodes studies and rationale for surgical approachesrdquo Epilepsiavol 34 no 1 pp 84ndash96 1993

[17] S K Lee S Y Lee DW Kim and et al ldquoOccipital lobe epilepsyclinical characteristics surgical outcome and role of diagnosticmodalitiesrdquo Epilepsia vol 46 no 5 pp 688ndash695 2005

[18] W T Blume S E Whiting and J P Girvin ldquoEpilepsy surgeryin the posterior cortexrdquo Annals of Neurology vol 29 no 6 pp638ndash645 1991

[19] J Bancaud ldquoEpileptic crises of occipital origin (stereo-electroencephalographic study)rdquo Revue drsquoOto-Neuro-Ophthalmologie vol 41 no 6 pp 299ndash314 1969

[20] W T Blume S Wiebe and L M Tapsell ldquoOccipital epilepsylateral versus mesialrdquo Brain vol 128 no 5 pp 1209ndash1225 2005

[21] D K Binder M Von Lehe T Kral et al ldquoSurgical treatment ofoccipital lobe epilepsyrdquo Journal of Neurosurgery vol 109 no 1pp 57ndash69 2008


[22] B C Jobst P D Williamson V M Thadani et al ldquoIntractableoccipital lobe epilepsy clinical characteristics and surgicaltreatmentrdquo Epilepsia vol 51 no 11 pp 2334ndash2337 2010

[23] N Tandon A V Alexopoulos A Warbel I M Najm andW E Bingaman ldquoOccipital epilepsy spatial categorization andsurgical managementrdquo Journal of Neurosurgery vol 110 no 2pp 306ndash318 2009

[24] A Liava R Mai L Tassi et al ldquoPaediatric epilepsy surgery inthe posterior cortex a study of 62 casesrdquo Epileptic Disorders vol16 no 2 pp 141ndash164 2014

[25] R Kuzniecky F Gilliam R Morawetz E Faught C Palmerand L Black ldquoOccipital lobe developmental malformations andepilepsy clinical spectrum treatment and outcomerdquo Epilepsiavol 38 no 2 pp 175ndash181 1997

[26] CG Bien FO BenningerHUrbach J SchrammMKurthenand C E Elger ldquoLocalizing value of epileptic visual aurasrdquoBrain vol 123 no 2 pp 244ndash253 2000

[27] T Rasmussen ldquoSurgery for epilepsy arising in regions otherthan the temporal and frontal lobesrdquoAdvances inNeurology vol8 pp 207ndash226 1975

[28] M Ono S Kubik and C D Abernathy Atlas of Cerebral SulciThieme Medical Publishers New York NY USA 1990

[29] F Latini ldquoNew insights in the limbic modulation of visualinputs the role of the inferior longitudinal fasciculus and theLi-Am bundlerdquoNeurosurgical Review vol 38 no 1 pp 179ndash1902015

[30] M Catani D K Jones R Donato andD H Ffytche ldquoOccipito-temporal connections in the human brainrdquo Brain vol 126 no9 pp 2093ndash2107 2003

[31] J C Fernamp119886119901119900119904 119886ndez-Miranda A L Rhoton Jr Jamp119886119901119900119904 119860lvarez-Linera Y Kakizawa C Choi and E P DeOliveira ldquoThree-dimensional microsurgical and tractographicanatomy of the white matter of the human brainrdquoNeurosurgeryvol 62 no 6 pp 989ndash1028 2008

[32] I L Maldonado N M de Champfleur S Velut C Destrieux IZemmoura and H Duffau ldquoEvidence of a middle longitudinalfasciculus in the human brain from fiber dissectionrdquo Journal ofAnatomy vol 223 no 1 pp 38ndash45 2013

[33] U TureMG Yasargil AH Friedman andOAl-Mefty ldquoFiberdissection technique lateral aspect of the brainrdquo Neurosurgeryvol 47 no 2 pp 417ndash427 2000

[34] J Martino F Vergani S G Robles and H Duffau ldquoNewinsights into the anatomic dissection of the temporal stem withspecial emphasis on the inferior fronto-occipital fasciculusimplications in surgical approach to left mesiotemporal andtemporoinsular structuresrdquo Neurosurgery vol 66 no 3 pp 4ndash12 2010

[35] I Alvarez D S Schwarzkopf andC A Clark ldquoExtrastriate pro-jections in human optic radiation revealed by fMRI-informedtractographyrdquo Brain Structure and Function 2014

[36] Y Hung M L Smith D J Bayle T Mills D Cheyne and MJ Taylor ldquoUnattended emotional faces elicit early lateralizedamygdala-frontal and fusiform activationsrdquo NeuroImage vol50 no 2 pp 727ndash733 2010

[37] C L Wilson T L Babb E Halgren and P H Crandall ldquoVisualreceptive fields and response properties of neurons in humantemporal lobe and visual pathwaysrdquo Brain vol 106 no 2 pp473ndash502 1983

[38] C Ajmone-Marsan and B Ralston The Epileptic Seizure ItsFunctional Morphology and Diagnostic Significance Charles CThomas Springfield Ill USA 1957

[39] A Takeda J Bancaud J Talairach A Bonis and M Bordas-Ferrer ldquoConcerning epileptic attacks of occipital originrdquo Elec-troencephalography and Clinical Neurophysiology vol 28 no 6pp 647ndash648 1970

[40] C H Wong A Mohamed L Wen et al ldquoMetabolic changes inoccipital lobe epilepsy with automatismsrdquo Frontiers in Neurol-ogy vol 5 article 135 2014

[41] A G Caicoya J Macarramp119886119901119900119904 119900n J Albamp119886119901119900119904 119894sua and J MSerratosa ldquoTailored resections in occipital lobe epilepsy surgeryguided by monitoring with subdural electrodes characteristicsand outcomerdquo Epilepsy Research vol 77 no 1 pp 1ndash10 2007

[42] C Aykut-Bingol R A Bronen J H Kim D D Spencer andS S Spencer ldquoSurgical outcome in occipital lobe epilepsyimplications for pathophysiologyrdquo Annals of Neurology vol 44no 1 pp 60ndash69 1998

[43] J W Sturm M R Newton Y Chinvarun S U Berlangieriand S F Berkovic ldquoIctal SPECT and interictal PET in thelocalization of occipital lobe epilepsyrdquo Epilepsia vol 41 no 4pp 463ndash466 2000

[44] O Forster ldquoBeitrage zur pathophysiologie der Sehbahn end derSehspharerdquo Journal fur Psychologie und Neurologie vol 39 pp463ndash485 1929

[45] A Brodal ldquoThe optic systemrdquo in Neurological Anatomy inRelation to Clinical Medicine pp 578ndash601 Oxford UniversityPress Oxford UK 3rd edition 1981

[46] D H Ffytche ldquoThe hodology of hallucinationsrdquo Cortex vol 44no 8 pp 1067ndash1083 2008

[47] B S Kasper E M Kasper E Pauli and H Stefan ldquoPhe-nomenology of hallucinations illusions and delusions as partof seizure semiologyrdquo Epilepsy and Behavior vol 18 no 1-2 pp13ndash23 2010

[48] J Kim H K Shin K J Hwang et al ldquoMirror focus in a patientwith intractable occipital lobe epilepsyrdquo Journal of EpilepsyResearch vol 4 no 1 pp 34ndash37 2014

[49] L G Ungerleider and M Mishkin ldquoTwo cortical visualsystemsrdquo in Analysis of Visual Behavior D J Ingle M AGoodale and R J W Mansfield Eds pp 549ndash586 MIT PressCambridge Mass USA 1982

[50] R Schulz F GWoermann andA Ebner ldquoWhenwritten wordsbecome moving pictures complex visual hallucinations onstimulation of the lateral occipital loberdquo Epilepsy and Behaviorvol 11 no 1 pp 147ndash151 2007

[51] L Cohen A Jobert D Le Bihan and S Dehaene ldquoDistinctunimodal and multimodal regions for word processing in theleft temporal cortexrdquo NeuroImage vol 23 no 4 pp 1256ndash12702004

[52] L Cohen and S Dehaene ldquoSpecialization within the ventralstream the case for the visual word form areardquoNeuroImage vol22 no 1 pp 466ndash476 2004

[53] J D Yeatman A M Rauschecker and B AWandell ldquoAnatomyof the visual word form area adjacent cortical circuits and long-range white matter connectionsrdquo Brain and Language vol 125no 2 pp 146ndash155 2013

[54] K Grill-Spector ldquoThe neural basis of object perceptionrdquo Cur-rent Opinion in Neurobiology vol 13 no 2 pp 159ndash166 2003

[55] D H Ffytche and R J Howard ldquoThe perceptual consequencesof visual loss lsquopositive1015840 pathologies of visionrdquoBrain vol 122 no7 pp 1247ndash1260 1999

[56] B Oehl A Schulze-Bonhage M Lanz A Brandt and D-MAltenmuller ldquoOccipital lobe epilepsy with fear as leading ictalsymptomrdquo Epilepsy and Behavior vol 23 no 3 pp 379ndash3832012


[57] M Manford D R Fish and S D Shorvon ldquoAn analysis ofclinical seizure patterns and their localizing value in frontal andtemporal lobe epilepsiesrdquo Brain vol 119 no 1 pp 17ndash40 1996

[58] M Gonzalez-Cuevas M Toledo E Santamarina et al ldquoVisualepileptic seizures Signs and symptoms and clinical implica-tionsrdquo Revue Neurologique vol 60 no 6 pp 257ndash262 2015

[59] B J Ramsey ldquoFrontal lobe epilepsy presenting as a psychoticdisorder with delusions and hallucinations a case studyrdquoPediatric Neurology vol 35 pp 78ndash81 2006

[60] M la Vega-Talbot M Duchowny and P Jayakar ldquoOrbitofrontalseizures presenting with ictal visual hallucinations and interic-tal psychosisrdquo Epilepsia vol 48 pp 17ndash19 2007

[61] V Manfioli M Saladini and A Cagnin ldquoIctal visual halluci-nations due to frontal lobe epilepsy in a patient with bipolardisorderrdquo Epilepsy amp Behavior Case Reports vol 1 pp 146ndash1492013

Submit your manuscripts athttpwwwhindawicom

Stem CellsInternational

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014


MEDIATORSINFLAMMATION

of


Behavioural Neurology

EndocrinologyInternational Journal of



Disease Markers


BioMed Research International

OncologyJournal of



Oxidative Medicine and Cellular Longevity


PPAR Research

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Immunology ResearchHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

ObesityJournal of



Computational and Mathematical Methods in Medicine

OphthalmologyJournal of


Diabetes ResearchJournal of



Research and TreatmentAIDS


Gastroenterology Research and Practice


Parkinsonrsquos Disease

Evidence-Based Complementary and Alternative Medicine

Volume 2014Hindawi Publishing Corporationhttpwwwhindawicom


are still classically described as the two main white matterbundles responsible for facilitating the epileptic propagationin OLE because of their close spatial relationship withthe optic radiation and the primary visual cortex (V1)[18 20]

For this reason the most common concern in occipitallobe surgery is aggravation of existing or creation of newvisual field defects so despite the successful results achievedwith epilepsy surgery in both adults and children [11 21ndash24]reports of such resections in the literature are rare (lt5 ofpatients) [17 25ndash27]

Encouraging data from tailored resection in OLE seem tohave important implications for the decision making and theexpected quantitative damage to the visual pathways [9 2324 28] It seems that a more specific sublobar categorizationof the resection within the occipital lobe may support a moreselective disconnection of the segregated and hyperactivatedbundles underlying the occipital area

The aim of this paper is to discuss the classical path-ways of occipital epileptic propagation in the light of newinsight in white matter (WM) connectivity in order tobetter understand the complex hierarchical segregation of theoccipital white matter and the different direction of epilepticpropagation with its crucial surgical implications

2 Methods

Ten cerebral hemispheres obtained from human cadaversdonated to the Department of Medical Cell Biology Sectionfor Anatomy studies at Uppsala University were enrolled inthis study All individuals donating had given written consentfor use of the whole cadaver for biomedical research andeducation in a testimonial donation letterThe study protocolwas filed with the application for ethical vetting of researchinvolving humans to the local ethical review board inUppsala(Dnr 2014468)

Each brain was fixed with intra-arterial injection of12 formalin solution within the first week after deathusing a perfusion device After this procedure the brainswere then carefully extracted and put in 10 formalin forat least 24 hours The pia mater arachnoid membraneand vascular structures were then carefully removed undermicroscopic magnification and the hemispheres were frozenat minus15∘Cndashminus20∘C for 6ndash10 days and then slowly defrostedfor 12 hours Before the start of dissection the superficialanatomy of the sulci and gyri was studied in detail Thespecimens were dissected in a stepwise manner from lateralsurface to the medial structures and from mesial and basalsurface to the ventricle with a modified fiber dissectiontechnique with respect to the technique described by Latini[29] Microscopic metal dissectors and thin wooden spatulaswere used in the initial steps of the dissection to split orpartially peel away the brain cortex preserving the mostsuperficial intracortical and subcortical fibres of the lateralbasal and mesial surface of the brain Subcortical intralobarassociative and projection fibres were exposed until the opticradiation (OR) on lateral and basal dissection and until thecallosal-tapetal fibres on the mesial surface of the occipitallobe in each specimen The dissections were performed

under microscopic magnification (up to 4x) Between eachdissection session the specimens were placed in 5 formalin

3 Results

31 Dissection of the Lateral Surface The dissection of thelateral surface started with the exposure of the indirect(vertical) component of the superior longitudinal fasciculus(vSLF) (Figure 1(a))This bundle which connects the angulargyrus (AG) to the region of the temporo-occipital junction onthe lateral surface was considered the anterior and superficialedge to the occipital connectivity in our dissections Medialto the vSLF the arcuate fasciculus (AF) was exposed withits c-shaped course connecting the infero-lateral temporo-occipital (T-O) region to the perisylvian region and frontallobe (Figure 1(b)) Posterior to vSLF and AF the verticaloccipital fasciculus (VO) was exposed (Figures 1(a)-1(b))This bundle runs from the superior occipital gyrus with anoblique and caudal direction to the fusiform gyrus Deeperand more posterior with respect to the vertical occipitalfasciculus the dorsal terminations of the inferior longitudinalfasciculus (dILF) were exposed at the level of the dorsolateraloccipital cortex (DLOC) and just below the parieto-occipitalsulcus (POS) in the cuneal region This portion of the ILFcomplex runs lateral and inferior to the sagittal stratumof Sachs (SSS) until the infero-lateral part of the temporalpole partially overlapping at this level with arcuate fasciculusterminations [29ndash31] (Figure 1(c)) At the level of cuneal area(Cu) the dILF fibres cover part of the posterior terminationsof the middle longitudinal fasciculus (MLF) which runsfrom the parieto-occipital sulcus region within the SSS andmedially to the AF to the white matter underneath thesuperior temporal gyrus [32] Medial to the MLF at the levelof the external capsule (ExC) the inferior fronto-occipitalfasciculus (IFOF) was isolated as classically described [3133 34] (Figure 2(a)) Medial to the IFOF within the sagittalstratum of Sachs and caudal to the temporal portion oflateral ventricle the optic radiation (OR) and the Meyerrsquosloop (MeL) were exposed completely until the visual cortexposteriorly (Figure 2(b))

32 Dissection of the Ventral Surface Once the ldquoUrdquo fibreshave been removed from the fusiform subcortical region atthe level of collateral sulcus a ventral branch of inferiorlongitudinal fasciculus (vILF) was isolated (Figure 3(a))These fibres arising from the posterior occipito-temporalgyrus are located inferiorly and medially to the dILF IFOFand sagittal stratumpreviously describedThis ventral branchruns from posterior and basal occipital region forward andslightly laterally until the temporal pole following the courseof lateral ventricleThis ventral pathway represents the infero-lateral wall of lateral ventricle for its entire course andbeyond the temporal horn it reaches the subcortical regionof parahippocampal gyrus (PHG) and then into the temporalpole (TP)

Deeper and more medial to the vILF the lingula-amygdaloid (Li-Am) bundle was exposed From the lingualcortex these fibres describe an arch-shaped bundle that follow


POS

hSLF

vSLF

VO

(a)

POS

VO AF

hSLF

(b)

POSAF

SSSdILF

Cu

DLOC

Ins

(c)

POS AF

MLF

SSS

dILF

Cu

DLOCTP

STG

M1

(d)





4 Discussion



POSAF

IFOFCu

PreCu

OPLi

ExC

M1

(a)

AF

SSS

ORIC

V1V2V3

(b)


Fu

AF

vILF

SSSdILF

OPLi

DLOC

BS

PHG

Un

(a)

HB

AFLiAmSSS

OPLi

HHBS

Am TPTa

(b)

V1

AF

IC

OR

SSS

MeLHH

(c)



POS

CF

Ci-FMSpFo

Pc

CcCi

CiR

Ac

PreCu

Li

Tha

Mb BSUn

PHG

Cu

(a)

POS

CF

CaRSp

FoPc

FM

vILFORChP

Li

TPDeGy

Cu

OP

(b)

POS

CFFMSp

TaOR

Li OP

ChP

Cu

(c)













PreCu

Ag

CuCc

LiOp

Dloc

















5 Conclusion




Acknowledgment


References





































































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of

















POS

hSLF

vSLF

VO

(a)

POS

VO AF

hSLF

(b)

POSAF

SSSdILF

Cu

DLOC

Ins

(c)

POS AF

MLF

SSS

dILF

Cu

DLOCTP

STG

M1

(d)





4 Discussion



POSAF

IFOFCu

PreCu

OPLi

ExC

M1

(a)

AF

SSS

ORIC

V1V2V3

(b)


Fu

AF

vILF

SSSdILF

OPLi

DLOC

BS

PHG

Un

(a)

HB

AFLiAmSSS

OPLi

HHBS

Am TPTa

(b)

V1

AF

IC

OR

SSS

MeLHH

(c)



POS

CF

Ci-FMSpFo

Pc

CcCi

CiR

Ac

PreCu

Li

Tha

Mb BSUn

PHG

Cu

(a)

POS

CF

CaRSp

FoPc

FM

vILFORChP

Li

TPDeGy

Cu

OP

(b)

POS

CFFMSp

TaOR

Li OP

ChP

Cu

(c)













PreCu

Ag

CuCc

LiOp

Dloc

















5 Conclusion




Acknowledgment


References





































































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of

















POSAF

IFOFCu

PreCu

OPLi

ExC

M1

(a)

AF

SSS

ORIC

V1V2V3

(b)


Fu

AF

vILF

SSSdILF

OPLi

DLOC

BS

PHG

Un

(a)

HB

AFLiAmSSS

OPLi

HHBS

Am TPTa

(b)

V1

AF

IC

OR

SSS

MeLHH

(c)



POS

CF

Ci-FMSpFo

Pc

CcCi

CiR

Ac

PreCu

Li

Tha

Mb BSUn

PHG

Cu

(a)

POS

CF

CaRSp

FoPc

FM

vILFORChP

Li

TPDeGy

Cu

OP

(b)

POS

CFFMSp

TaOR

Li OP

ChP

Cu

(c)













PreCu

Ag

CuCc

LiOp

Dloc

















5 Conclusion




Acknowledgment


References





































































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of

















POS

CF

Ci-FMSpFo

Pc

CcCi

CiR

Ac

PreCu

Li

Tha

Mb BSUn

PHG

Cu

(a)

POS

CF

CaRSp

FoPc

FM

vILFORChP

Li

TPDeGy

Cu

OP

(b)

POS

CFFMSp

TaOR

Li OP

ChP

Cu

(c)













PreCu

Ag

CuCc

LiOp

Dloc

















5 Conclusion




Acknowledgment


References





































































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of






















PreCu

Ag

CuCc

LiOp

Dloc

















5 Conclusion




Acknowledgment


References





































































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of





























5 Conclusion




Acknowledgment


References





































































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of































































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of
















the classical pathways of occipital lobe epileptic ...822232/fulltext01.pdf · researcharticle the...

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