a clinical and radiological correlation ofthe lesions produced by

J. Neurol. Neurosurg. Psychiat., 1959, 22, 1.

A CLINICAL AND RADIOLOGICAL CORRELATION OF THELESIONS PRODUCED BY CHEMOPALLIDECTOMY

AND THALAMECTOMY*BY

GONZALO J. BRAVO and IRVING S. COOPERFrom the St. Barnabas Hospital for Chronic Diseases, New York

The purpose of this paper is to present the clinicaland radiological correlation of 360 intracerebrallesions placed in 300 patients who underwent surgeryfor the treatment of Parkinson's disease. These casesrepresent a consecutive series of patients, part of atotal of more than 800 basal ganglia operations per-formed on our service since 1952. Details of thesurgical technique employed have already beenreported (St. Barnabas Symposium on "SurgicalTherapy of Extrapyramidal Disorders", 1956;Cooper, 1956; Cooper and Bravo, 1958a).The cases selected for this study have been those

operated on by using the balloon cannula technique(Bravo and Cooper, 1957) which allows testing ofthe physiological effects of a temporary lesion beforethe injection of alcohol and, by creating a smallcavity, facilitates the production of a well-circum-scribed alcohol lesion (Cooper and Bravo, 1958b).Such lesions, when the alcohol has been mixed withpantopaque, can be visualized radiographically.

In an earlier report we presented the anatomicalevidence and the corresponding radiological land-marks obtained as a result of a study carried out in65 cadaver brains (Bravo and Cooper, 1958). Inthat report we studied the anatomical location of120 intracerebral lesions visualized radiographicallyand confirmed by anatomical studies of each brain.The conclusions of that paper regarding the radio-logical and anatomical correlations of certain lesionshave been confirmed by other investigators (Amador,personal communication). The results of ouranatomical study are also in essential agreementwith the data that can be obtained from some of theavailable brain atlases (Stelmasiak, 1956; Spiegeland Wycis, 1952).The surgical target in the present series of patients

was the globus pallidus and/or the thalamus. In our

anatomical studies we were also concerned with theradiological projection of these structures andestimation of limits of safety according to shapeand size of the skull, size of the ventricles, andrelative position of the foramen of Monro and pinealgland. As a result of continuing investigations aseries of intracerebral structures have been radio-graphically outlined (Figs. 1 and 2) and the land-marks for the two surgical targets, namely the mesialglobus pallidus and ventrolateral thalamus, wereestablished (Cooper, Bravo, Riklan, Davidson, andGorek, 1958). The results of the earlier studiescan now be related to radiographically visualizedlesions in patients.

In this paper we are going to consider the radio-logical location of these lesions in terms of theneurological results which they produced. With theinformation obtained from the cadaver study it ispossible to correlate, with a fair degree of accuracy,the anatomical site of these lesions with the observedeffects. However, until definite anatomical proof ofthe structures involved can be shown, when and ifthe brains of those patients come to post-mortemexamination, we should limit ourselves to an evalua-tion of the clinical and radiological data.

Material and MethodsThree hundred consecutive patients, all of whom have

been operated on by the balloon-cannula alcohol method,are included in this report. The follow-up period rangesfrom six to 18 months. We have excluded four patientswho died in the immediate post-operative period as aresult of intracerebral haemorrhage.

Altogether 360 lesions have been plotted in severalstandard x-ray tracings of the skull. For the dimensionsof that skull and for the placement of the foramen ofMonro and the pineal gland within it we have used amodel made with a geometrical mean of the radiographsof all the patients considered. The lesions have beenplaced in those maps according to their relative position,in terms of the "foramen-pineal line" and in terms of thebase line of the skull. The reason why we have chosen

1

This work has been supported in part by a grant from the SisterKenney Foundation, Foundation for Neuromuscular Diseases, andthe Office of Vocational Rehabilitation of the Department of Health,Education and Welfare.

GONZALO J. BRAVO AND IRVING S. COOPER

FIG. 1.-Cannula with inflated balloon placedwithin the standard radiological landmarksfor the globus pallidus. Lesion in thecorresponding anatomical specimen appearsin the mesial globus pallidus.

FIG. 2.-Cannula with inflated balloon placedwithin the standard radiological landmarksfor the ventrolateral thalamus. Lesion inthe corresponding anatomical specimenappears in the ventro-lateral thalmic area

(retouched).

2

...........

..............

CLINICAL AND RADIOLOGICAL CORRELATION OF INTRACEREBRAL LESIONS 3

these reference points, and why we think that relativemeasurements in relation to them are valid, have beenreported elsewhere (Bravo and Cooper, 1958). New datawhich consider the geometrical positions of the foramenof Monro and the pineal gland as related to the bonystructures and relative dimensions of the skull will be theobject of a later report.

In order to simplify the presentation, we have chosen asour reference point for the charts the geometrically centralarea of the lesion, although in some cases the actual lesionextended beyond the boundaries of the circles representedin the accompanying charts. Each point in the chartsrepresents a minimum of three patients with some pointscorresponding to as many as 43 patients.

It is evident that, as had been intended at the time ofsurgery, the lesions fall into two main groups: thosedirected at the globus pallidus and efferent pallidal path-ways, and those aimed at the ventrolateral area of thethalamus. In addition, it became evident that there wereseveral points which showed a fairly constant radiologicaland clinical correlation outside of the standard limits ofthe surgical targets. In certain cases, lesions in theseadjacent areas produced undesirable results; in othercases, temporary neurological effects with or withoutaccompanying relief of tremor and rigidity were observed.

ResultsThe findings of this study have been summarized

in five charts. Fig. 5 includes those lesions whichaffect primarily the globus pallidus and/or itsefferent fibres. Fig. 6 includes those lesions whichinvolve different areas of the thalamus and/or efferentor afferent thalamic tracts. We have summarized inFig. 7 those areas from which serious undesirableeffects were obtained. It should be noted that someof those points are based on a very small number ofcases and that the complications were, with rareexceptions, temporary. But because of the constantand close relationship between each of those pointsand the corresponding clinical side-effect, it was con-sidered worthwhile to call attention to it. In Fig. 8we have isolated the distribution of those lesionscausing motor weakness or sensory changes. Insome instances the motor weakness was a transitoryphenomenon observed in the operating room afterinflating the balloon or inserting the cannula. Quickrecovery followed the deflation of the balloon or thewithdrawal of the cannula and most of these patientswere successfully operated on at a later date. Inonly two instances the lesion thus produced left aresidual motor deficit.Two facts should also be mentioned in relation to

the occasional motor deficit associated with chemo-pallidectomy or chemothalamectomy. (1) The lesionproduced by the insertion of the needle or by inflat-ing the balloon, even if incorrectly located, affectsonly a very small segment of the internal capsuleand consequently only transient and temporary

FIG. 3.-Lesion produced in the internal capsule by theinflated balloon.

Pt

FIG. 4.-Lesion produced by the balloon plus injection of0-5 ml. of alcohol into the ventrolateral thalamus. Thelesion is sharply outlined against the internal capsulebut it does not spread macroscopically among thefibres of the capsule.

effects should be expected to occur (Fig. 3). (2)When the inflated balloon itself does not produce amotor deficit, it has never resulted in our experiencefrom subsequent injections of alcohol into the samearea unless some bleeding occurred. The explanationfor this apparently lies in the fact that when thealcohol is deposited in the most lateral area of thethalamus, the thick fibre layers of the capsule at thatlevel constitute a natural barrier and the alcoholnecrosis appears to occur medialward into the softthalamic tissue (Fig. 4).

Fig. 9 corresponds to the lesions in patient No.297. This single patient summarizes some of thefavourable and unfavourable effects produced bythree different radiologically visualized lesions.

Pallidal Lesions.-The five different lesions repre-sented in Fig. 5, which includes a total of 67 patients,correspond to the area of the globus pallidus and itsefferent fibres. Although some other projectionsystems will also be involved with most of theselesions, we have to assume, at the present time, that


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the effectiveness of these lesions in relieving Parkin-sonian symptoms is due to destruction involving theglobus pallidus and its efferent fibres, particularlythe ansa and fasciculus lenticularis. Lesion No. I

corresponds to the mesial part of the globus pallidusand it may extend from 10 to 18 mm. from the mid-line in the antero-posterior radiological projection(Fig. 1). In the lateral view, this lesion may extendfrom the level of the anterior commissure or anteriorborder of the foramen of Monro to 4 or 5 mm.behind the posterior margin of the foramen. Itshould be remembered that as we move posteriorly,part I of the globus pallidus moves away from themidline, so that the mesial globus is not in the samesagittal plane at the level of the anterior commissure,that it is 3 mm. behind the posterior margin of theforamen, but at both levels a pure pallidal lesion canbe produced.

Lesion No. I has most commonly resulted inalleviation of rigidity and incomplete alleviation oftremor. Occasionally, complete relief of tremor isobtained. No ill effects follow this lesion. LesionNo. 2 affects the innermost part of globus I and theansa lenticularis. It is possible, also, that some of theanterior fibres of the fasciculus lenticularis might beinvolved. Lesion No. 2 has generally resulted in amore complete relief of rigidity than lesion No. I

and the relief of tremor is more often complete or

FIG. 5

almost complete. Regarding the relief of tremorobtained by this type of lesion, two additional pointsshould be mentioned: (1) In some instances therelieved tremor would transiently reappear understrain. (2) In five cases, in which the rigidity wasrelieved but with marked residual tremor, weobserved a gradual, progressive disappearance of thetremor, so that at the end ofthree months the patientswere free of symptoms. Lesion No. 3 involves theantero-ventral segment of the thalamus and thefibres of the fasciculus and ansa as they run into it.This type of lesion has been followed by essentiallythe same results as lesion No. 2. Lesions Nos. 4and 5 have in common the involvement of theanterior third of the posterior limb of the internalcapsule, through which the fibres of the fasciculusproject from the globus to the thalamus. At thatlevel the internal capsule carries fronto-pontine andfronto-bulbar fibres and the anterior segment of thecortico-spinal pyramidal tract. Lesion No. 4, prob-ably because of the involvement of the fasciculuslenticularis, had resulted in improvement of theParkinsonian symptoms. The results in the caseswith the lesion in area No. 5 have been consistentlypoor, and both lesions Nos. 4 and 5 have beenfollowed on occasion by transient dysphagia,dysarthria, and facial weakness. When a lesion ofthis type is placed bilaterally lasting dysphagia and

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THALAMIC MECHANISMS

7. DORSOLATERAL TWALAMUS

CD usual iMmediate reief of trernor &ri.qidifty Wiith eoriy recurrence.

C some cases with permonent reliefm some coses with no relief7 slqht temporarqi otaxia7 confusion

THERAPEUTIC RESULTS 0POSSIBLE SlD EFFECTS v

8. PROJECTION of BRACH. CONJ.VIA NUCLEUS RUBER

* comprete reliefof tremor&riqiditq(4cases)* hypotonusv moderte to severe ataxiav poor finger control (temporary)vsliqht to severe temporary confusion

6. VENTROLATERAL THIALAMUSFIG. 6 9 complete relief of trenvr &riqidity

3 full return of fine movementsif lesion isposterior 'babq"hand

7 if lesion correctly placed* none

dysarthria may occur. The only other undesirableeffects of this group of pallidal lesions have beendrowsiness and apathy of a temporary nature.

It should be noted that division within these areas,all of them included within little more than a cubiccentimetre of brain, is somewhat artificial. We arespeaking in terms of main localization of the lesionand of predominant symptoms. Some small lesionshave reproduced rather sharply the effects attributedto a certain localized area; larger destruction, on theother hand, will extend beyond the boundaries of onespecific area and the combined effects of lesions intwo or three of the described structures would follow.

Thalamic Lesions.-In Fig. 6 we have representedthose lesions, 183 in all, which we believe correspondto the ventrolateral region of the thalamus posteriorto the anteroventral nucleus. Area No. 6 includesthree points, all within the ventrolateral thalamusfrom which constant results regarding the relief oftremor and rigidity have been obtained. This areaseems to start at a point midway between the foramenof Monro and the pineal gland and to extend back-wards to a point 7 to 8 mm. in front of the pinealgland. In the antero-posterior projection of theradiograph the centre of the area occupies a point14 to 20 mm. lateral to the midline (Fig. 2). Details

as to the possible structures involved in this type oflesion have been given in a previous anatomicalpaper. It is not clear at this time if the small varia-tions in the radiological location of that point fromwhich specific response regarding relief of tremorand rigidity can be obtained are due to differencesin the radiological projection of the thalamus (due,in turn, to anatomical variations in that particularbrain) or if they are related to differences from caseto case regarding the physiological mechanismsresponsible for the tremor and the rigidity.

Lesions within this area, No. 6, especially in itsposterior part, have resulted in relief of tremor andrigidity in practically every case. It should also benoted that we have observed with this type of lesiona return of the fine voluntary movements of thefingers, usually within a period of minutes afterplacing the lesion. Lesions confined to the limits ofarea No. 6 have not resulted in any ill effects. Inseveral cases we have observed a certain spatialarrangement within this area, in such a way thatfollowing insertion of the needle the relief of theleg symptoms would be obtained from a pointpostero-caudal in relation to that point affective forthe relief of the arm symptoms.Area No. 7 occupies a zone immediately dorsal

and posterior to that of area No. 6. Anatomically, it


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seems to represent a different zone of the thalamusand, according to our own anatomical studies, areas

Nos. 6 and 7 affect different structures and cannotbe in the same thalamic nuclei, even if one takes intoaccount the widest possible margin of radiologicaland anatomical variations. Since the results in somecases with lesions at the level of area No. 7 have beenvery similar to those obtained at area No. 6, it mustbe assumed that either two different areas canrespond in a similar manner, or that we are inter-rupting the same pathway at two different levels.This also applies, with certain limitations, to pointNo. 8, discussed below, and if the concept is widenedit would similarly include the favourable pallidallesions.Area No. 8 seems to involve the posterior segment

of the most ventral part of the lateral thalamus,which receives fibres from Forels fields and, in part,the post-rubral radiation of the brachium con-

juntium. Lesions in this area have been followed byrelief of tremor and rigidity with a good return offine voluntary motion, accompanied by a variabledegree of temporary incoordination of the limbs,which is manifested by past-pointing, swaying of theraised limb, and a certain clumsiness in manipulation.These signs, minimal in most instances, have clearedwithin a period of three weeks with maintained reliefof tremor and rigidity. Usually, these "cerebellar"signs have been more marked in the medial part ofarea No. 8. It is possible that the lowermost segmentor area No. 8 may also involve projections to or

from the substantia nigra.The thalamic lesions at the indicated points have

consistently resulted in an immediate and complete

relief of tremor and rigidity. Except for the occur-rence of temporary incoordination at point No. 8,no ill effect seems to result from these lesions. Acomplete looseness or hypotonicity of the affectedlimbs, without weakness and with full range ofvoluntary motion, can be observed within seconds or

minutes after inflating the balloon in these sites. Itshould be noted, however, that the exact point ofspecific response seems to vary a few millimetresfrom patient to patient, and that careful, persistenttesting is necessary before considering a placementas final.

Areas of Serious Complications.-Points marked9 in Fig. 7 are based on the radiographs of seven

patients who developed weakness of the contralateralextremities when the needle reached that particularlevel or when the balloon was inflated in that region.The motor impairment varied from a weakness ofgrip and heaviness of the arm and leg to a completeflaccid paralysis. All of these patients but one

recovered within a period of two to four weeks. Infour of the cases, recovery has been complete. Twoshow residual signs, namely, increased deep tendonreflexes, slight weakness of the hand, and somelimitation in the fine movements of the fingers. Theremaining patient still has a moderate hemiparesisnine months after surgery. Every one of thesepatients developed an immediate contralateral signof Babinski and three of them with lesions inthe dominant hemisphere had language difficultieswhich followed the same favourable evolution as thehemiparesis. It is to be noted that these patientswith presumably localized capsular lesions remained

01( .'

FIG. 7

6


FIG. 8

alert and fully conscious in contrast to those patientswho developed motor deficits as a result of intra-cerebral haemorrhage.

This area 9 is immediately lateral to area 6 in our

charts. The internal capsule curves at that levelaround the lateral and caudal aspects of the thalamus.According to our clinical experience, the motor fibres,the lesion of which would cause a hemiparesis, are

concentrated in a narrow band behind the mid-pointin the foramen-pineal line.

There have been two additional cases in which a

hemiparesis was produced on the operating table.These two patients had had previous surgery at thelevel of point 4, that is, involving the pallido-fugalfibres and the anterior third of the posterior limbof the internal capsule. No motor deficit resultedat that time, but the symptoms (Parkinsoniantremor and rigidity in one case, and dystonia muscu-lorum deformans in the other) eventually recurred.The patients were operated on again and in bothcases the needle entered area No. 9. The hemiparesiswhich resulted was not of the flaccid type. On thecontrary, spasticity developed within a matter ofminutes. The hand of the patient could be seen

closing and acquiring the posture of a long-standinghemiparetic limb. Both patients improved a greatdeal with the passing of time, but residual spasticityremained. Whether this phenomenon was due to a

double lesion affecting pyramidal and parapyramidalfibres remains open to speculation.

Point No. 11 of this chart represents that area

from which sensory abnormalities have beenobserved. The changes have been in the form of a

hypaesthesia and hypalgesia affecting light touch,

pin prick, temperature, and pain threshold as mea-

sured by galvanic stimulation. These sensory changeshave been observed in a total of eight cases. In twoof them they were in the form of a hypaesthesia andhypalgesia affecting subjectively the entire contra-lateral half of the body. Objectively, the sensory

changes were more marked on the face and distalpart of the extremities. One of these patients has notbeen available for follow-up examination. The otherpatient, one year after surgery, still has subjectivehemisensory changes, but on objective examinationsonly patchy areas of hypaesthesia and hypalgesiacould be observed on the affected side of the body.The remaining five patients had sensory changes ofa similar nature, but limited to the perioral area andto the index finger in one case, and the tips of thesecond, third, and fourth fingers in the remainingfour patients. These changes subsided subjectivelyand objectively in a period of one to three weeksfollowing surgery.

There have been no cases in which position or

vibration senses have been affected.Lesions at the level of point 10 have resulted in

contralateral involuntary movements in 11 patients.These movements are difficult to describe as a

clinical entity and in some cases resemble hemi-ballistic movements, and in other cases they tookthe form of a choreoathetosis. The hand alone wasinvolved in five cases, the arm and the leg in threecases, and the entire contralateral side of the body inthree cases. Those cases with movements limited tothe hand cleared spontaneously in a maximum oftwo weeks. Those cases with movements in the armand leg cleared spontaneously between one to three

PROFILE OF INTERNAL CAPSULE

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weeks following the onset. Every one of these eightcases eventually had a complete relief of tremor andrigidity in the involved extremities.Of the three cases with severe choreoathetosis, two

of them occurred following bilateral operations, andone of them after a unilateral operation. One of thebilateral cases cleared totally after two weeks ofsevere choreoathetosis and resulted in completerelief of tremor, rigidity, and bradykinesia. Thesecond of the bilateral cases had mild involuntarymovements at the time of discharge from the hospitalsix weeks after surgery. One patient in this groupdeveloped a severe contralateral hemiballismus a fewhours after surgery. The involuntary movementsslowly subsided and had virtually disappeared withinfour months at which time the patient died as aresult of a carcinoma of the head of the pancreas.Post-mortem examination of the brain revealed asmall lesion affecting the fields of Forel and thelateral half of the subthalamic nucleus of Luys. Thisis probably the same area involved in the otherpatients with lesions at point 10. Radiologically,point 10 appears at a level 5 to 9 mm. below themiddle third of the foramen-pineal line and 4 to 10mm. from the midline.

This series of cases of surgically induced involun-tary movements will be the object of a detailed reportat a later date.

Point No. 12 in Fig 7 represents a region in which

surgery has resulted in ataxia, incoordination, andmarked hypotonus. These effects are not reallyserious complications. There has been a gradualrecovery in every case and the initially ataxic,hypotonic side has returned to normal function witha maintained relief of the tremor and rigidity.

In Fig. 8 we have summarized some of the pointsof the previous charts, those from which motor orsensory deficits have been produced, thus giving aradiological and clinical outline of the distributionof the fibres of the internal capsule. Basically thisoutline is in agreement with the known distributionof anatomical fibres. We have, however, found thatthose lesions that seem to be responsible for contra-lateral weakness of the limbs are distributed moreposteriorly than one would expect from the standarddescriptions in anatomical textbooks. That is, thosefibres carrying motor impulses to the contralateralextremities are affected only by lesions at least 15mm. behind the foramen of Monro at the level ofthe foramen-pineal line, well behind the so-calledgenu of the capsule. The question of level of depthof the lesion is important when one considers thedistribution of fibres in a sagittal plane because ofthe double curvature in the internal capsule. Thiscurvature is such that the so-called genu of thecapsule becomes displaced posteriorly as the fibresrun downward.As can be seen in Fig. 8, facial weakness has been

8


O AREAS CAPABLE OF RELIEVINGTREMOR & RIGIDITY

O INCONSTANT RESULTJS OBTAINED

FIG. 10

AREAS OF COMPLICATIONVS

obtained from the anterior segment of the posteriorlimb of the capsule. When a more posterior segmentof the capsule is affected by a lesion the arm willshow more marked deficit than the leg withoutevidence of a specific distribution of fibres. This isthe same phenomenon clinically observed aftercerebral vascular accidents.A similar finding of greater susceptibility of the

hand and facial fibres have been found at point 11from which sensory changes were obtained. In mostinstances the face and the hand, especially the indexand middle fingers, showed the more pronouncedsubjective and objective sensory deficits irrelevantof the special point of lesion.

Fig. 9 emphasizes some of the points of Fig. 6 inrelation to the clinical evolution of case No. 297,Mrs. C. C. This 61-year-old woman with Parkin-sonism manifested primarily by tremor and rigidityin the right extremities underwent a left transfrontalchemopallidectomy with placing of a well localizedlesion at point No. 1 of Fig. 9. Complete relief ofrigidity with recurrence of the tremor 10 days aftersurgery resulted. There were no neurological deficits.Re-operation was decided upon, and the needle wasinserted and the balloon inflated at point No. 2 ofFig. 9. Immediately right flaccid paralysis and motoraphasia resulted. The balloon was at once deflatedand the needle withdrawn. Progressive recovery ofthe motor symptoms and aphasis followed and at theend of two weeks the patient was in the same state asbefore her second operation, tremor included. Thethird operation was carried out four weeks later.This time the lesion was successfully placed at pointNo. 3 of Fig. 9 with immediate relief of the tremorand no signs of neurological deficits. This patient

has been followed for over one year and has remainedfree of tremor and rigidity in the right extremitieswith normal function of the hand and no signs ofinvolvement of the pyramidal tract.*

Fig. 10 is a composite drawing of the favourable,unfavourable, and "neutral" lesions as they appearin the radiographs. Areas from which good clinicalresults have been obtained without neurological ill-effects are represented in green. Lesions which haveresulted in neurological complications are repre-sented in red. And finally, those "in-between" areaswhere results have been inconstant or temporary andthe side-effects, for the most part, negligible, arerepresented in blue.Two things should be emphasized: first that there

is no sharp limit between the green and blue areas,although there seems to be a narrow margin ofsafety between blue or green and red areas, especiallyat posterior-external and posterior-inferior levels.Second, that we are dealing with tri-dimensionalstructures that are represented here in two dimen-sions, and consequently, there is a superimposition ofareas which cannot be shown in the figures. For therepresentation, preference has been given to the redin both antero-posterior and lateral projections; anylesion which falls within a red area either in theantero-posterior or in the lateral view is likely to bewithout clinical benefit and result in a neurologicalcomplication.

ConclusionsThe most constant and complete relief of both

alternating tremor and rigidity is obtained from a

*Since this paper was submitted the same patient has been success-fully operated on for her other side.


lesion in the region of the ventrolateral nucleus of thethalamus. No abnormal sensory, motor, intellectual,or psychological abnormalities result from such a

lesion. This lesion is the one of choice for treatmentof both tremor and rigidity.

Involvement of cerebellar pathways to the ventro-lateral thalamus undoubtedly contributes in some

measure to the effectiveness of this lesion in alleviat-ing Parkinsonian tremor and rigidity.

Lesions of the mesial globus pallidus, the efferentpallidal pathways, and the antero-ventral thalamusprovide good relief of rigidity but less consistentrelief of tremor. However, in some cases, tremor,which was incompletely relieved by a lesion in thiscomplex, will gradually disappear completely withintwo or three months.The areas responsible for neurological complica-

tions are distributed in a predictable manner, in

such a way that those complications can be pre-vented-or when they occur be explained-in termsof the radiological placing of the lesion.

REFERENCESBravo, G., and Cooper, 1. S. (1957). J. Amer. Geriat. Soc., 5, 651.

(1958). Anatomical and Radiological Correlations in Relationto the Placement of Therapeutic Lesions into the Basal Ganglia.Presented at the New York University Symposium on extra-pyramidal disorders on May 15, 1958. To be published.

Cooper, I. S. (1956). The Neurosurgical Alleviation of Parkinsonism.Charles C. Thomas, Springfield, Illinois.and Bravo, G. (1958a). J. Neurosurg., 15, 244.

(1958b). Neurology, 8, 344.Riklan, M., Davidson, N. W., and Gorek, E. A. (1958).

Geriatrics, 13, 127.St. Barnabas Symposium on Surgical Therapy of Extrapyramidal

Disorders (1956). J. Amer. Geriat. Soc., Vol. IV, Number 12,pp. 1171-1319.

Spiegel, E. A., and Wycis, H. T. (1952). Stereoencephalotomy.Part I: Methods and Stereotaxic Atlas of the Human Brain.Grune and Stratton, New York.

Stelnasiak, M. (1956). Anatomical Atlas of the Human Brain andSpinal Cord. Polish State Medical Publishers, Warsaw.

10

a clinical and radiological correlation ofthe lesions produced by

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