n806 and ct head
TRANSCRIPT
CT radiology CT anatomy Glossary of terms Clinical indications Systematic interpretation Head trauma Stroke Tumor
Brain mets/tumor Infection/abscess Nodes/masses Pulmonary embolism Abdomen/pelvis
Patient BPatient A
Note how the subdural bleed (left side) has compressed the ipsilateral
ventricle resulting in a compensetory expansion of the contralateral
ventricle.
Used with permission by the CRASH Trials with credit to Mr. J. Wasserberg and Mr. B. Mitchell
Terms beginning with A – M Terms beginning with N - Z
Amnesia Arachnoid granulations Arachnoid membrane Basal ganglia Basilar Artery Calvarium Caudate (see basal
ganglia) Cerebellum Cerebral cortex Choroid plexus Circle of Willis
Cistern(s) Corpus callosum Dorsum Sellae Dura mater Falx cerebri Globus pallidus (see basal
ganglia) Gyrus Herniation Insula/insullar ribbon Internal capsule Lentiform nuclei (see basal
ganglia) Medulla Midbrain
Process where by increased intracranial pressure forces brain parenchyma through a fixed opening.
Clinical scenarios: Transtentorial herniation (aka “uncal” herniation)
▪ Medial temporal lobes (uncus) and brainstem are forced through the tentorium
▪ Symptoms include headache, decreased consciousness, pupillary dilation and may progress to extensor posturing and death
Cerebellar herniation (rare)▪ Cerebellar tonsils are “pushed” into the foramen magnum
▪ Similar symptoms as transtentorial herniation
The cerebrum is the largest part of the brain and is responsible for thought and abstraction.
The cerebrum is divided in four “lobes”. Some authors include the insula as the fifth “lobe” of the cerebrum
The outer layer of the cerebrum (cortex) is gray matter (lacks myelin)
Anterograde amnesia = Loss of memory for an event or events immediately following a head injury.
Retrograde amnesia = Loss of memory for an event or events preceeding a head injury.
From the Greek arakhnoeid’s, (cobweblike)
Villous projects of the pia-arachnoid membrane whose function is to absorb CSF and return it to the venous circulation via the superior saggital sinus.
Arachnoid granulations
A thin membrane adherent to the dura mater.
The arachnoid membrane is the middle layer of the three meningial layers (dura mater, arachnoid membrane, and pia mater) that surround the brain and spinal cord.
The basasl ganglia consists of three gray matter structures (caudate, putamen, and globus pallidus) deep within cerebral hemispheres
Lentiform nuclei = putamen and globus pallidus
Functions as motor relay stations Pathology in the basal ganglia results in
purposeless movements (Parkinson’s disease)
The basilar artery provides blood to the posterior aspect of the Circle of Willis and is formed from the paired vertebral arteries. Supplies blood to the pons, cerebellum, and posterior cerebrum.
The circle of Willis is a term used to describe the arterial supply for the brain. The circle is derived from the two internal carotid arteries as well as the basilar artery, the latter being the continuation of the two vertebral arteries.
Vertebral arteries
Vertebral arteries
The bony “roof” of the skull; also know as the “skull cap”.
The cerebellum is that portion of the brain that is involved with coordination of voluntary movement, balance, and muscle tone.
Connects the brainstem with the forebrain and is involved in the control of sensory processing
Ventricluar tissue (ependyma) that produces cerebral spinal fluid (CSF).
From Latin (“box”). A well defined collection of CSF within the
subarachnoid space (located between the pia and arachnoid membranes).
Several cisterns are generally described and two are of importance in the CT head:
Suprasellar - (Star-shaped) Location of the Circle of Willis
Quadrigeminal - W-shaped at top of midbrain
The corpus callosum is the structure that connects the left and right cerebral hemispheres.
The dorsum sellae is the square shaped part of the sphenoid bone that forms the posterior boundary of the pitutary fossa.
Dorsum sellae
Latin (“hard mother”)
The outer, fibrous portion of the meninges.
Dura Mater Epidural hematomaBrain
A reflexion of the dura mater located between the cerebral hemispheres. Function is to provide support to the cerebral hemispheres.
The rounded, elevated convolutions on the surfaces of the cerebral hemispheres.
The insula is one of the five cerebral cortices (frontal, parietal, temporal, occipital, insular) and is located deep to the frontal, parietal, and temporal lobes. Function is to integrate autonomic functions.
Collection of axons that carry sensory information to the cortex and motor information to the cord.
The internal capsule is very sensitive to stroke
Aka “medulla oblongata” Located in the brain stem and sits below the
pons and in front of the cerebellum. Functions to help control autonomic function,
especially heart rate and breathing.
Includes the midbrain, pons, and medulla. Major function is survival (breathing, digestion, heart rate, blood pressure) and for arousal (being awake and alert).
Occipital lobe Parenchyma Parietal lobe Pineal gland Pneumocephalus Pons Posterior fossa Putamen (see globus
pallidus) Sagittal sinus
Septum pellucidum Sulcus Suture(s) Temporal lobe Tentorium cerebelli Thalamus Uncus Ventricle(s)
Pneumocephalus (see red arrow) is the presence of air (or gas) within the cranial cavity and is usually associated with a basilar skull fracture
The sutures are fibrous connections between bones of the skull
Sutures allow for some flexibility of the cranium
Fontanelles (aka “soft spots”) are unfused areas where sutures meet
Sutures ossify at various times throughout life
The pons sits between the brainstem and medulla
Controls rate and depth of breathing Relays impulse from medulla to cerebrum Clinical pathology results in:
Bilateral, fixed, pinpoint pupils (comatose patient)
Cheyne-Stokes breathing
▪ Hyperventialtion followed by apnea
The uncus is the medial (innermost) portion of the temporal lobe
Under high intracranial pressure (ICP) the uncus can be involved in a transtentorial herniation syndrome
ICP pushes the uncus through the tentorium cerebelli which results in compression of the brainstem
1. The brain squeezes under the falx cerebri in cingulate herniation
2. The brainstem herniates caudally
3. The uncus and the hippocampal gyrus herniate into the tentorial notch
4. The cerebellar tonsils herniate through the foramen magnum in tonsillar herniation
The ventricles are CSF-containing cavities Provides a protective cushion (buoys the
brain) CSF produced in roof of ventricles (choroid
plexes) Circulation of CSF through ventricles and
around the brain (subarachnoid space) and cord (central canal) with reabsorption in arachnoid villi
The thalamus is the central relay station for sensory fibers (except olfactory)
Cerebral cortex communicates with thalamus Responsible for primitive emotional responses
Fear
Pleasant vs. unpleasant stimuli
The temporal lobes are one of the five cortical lobes
The temporal lobes are responsible for hearing, speech, and some emotional and memory functions
Lain – “groove” or “trench” Pleural – “sulci” (sul-sigh) The small cracks or dimples on the surface of the
brain
The septum pellucidum is a thin midline structural membrane
The septum runs vertically between the lateral ventricles as well as inferiorly from the corpus callosum
Aka “superior sagittal sinus” Large collection of venous blood above and behind the
brain Attached to the falx cerebri Receives CSF from the arachnoid granulations
The posterior fossa is an area within the intracranial cavity bound by the tentorium cerebelli above and foramen magnum below
The posterior fossa contains the cerebellum and brainstem structures
Aka “pineal body” The pineal glad is an endocrine gland that
produces melatonin and is important in sleep-wake cycles
The parietal lobe is the cortical lobe responsible for sensation (cutaneous and muscular)
Responsible for integration of thoughts and feelings
The functional tissue(s) (key elements) of an organ
The occipital lobe is the cortical lobe responsible for vision
Integration areas for visual images with sensory experiences.
Dura matter (tentorium cerebelli) separates the occipital lobe from the cerebellum
The putamen is part of the basasl ganglia The basals ganglia consists of three gray matter
structures (caudate, putamen, and globus pallidus) deep within cerebral hemispheres
Lentiform nuclei = putamen and globus pallidus
Functions as motor relay stations Pathology in the basal ganglia results in
purposeless movements (Parkinson’s disease)
CT head is currently the procedure of choice for evaluation of suspected stroke
Stokes are either hemorrhagic (minority) or nonhemorrhagic (vast majority of cases)
Nonhemorrhagic strokes = “ischemic” strokes The latter, if diagnosed quickly, can (potentially) be
treated with thrombolytic agents
The CT can reliably serve to rule out intracranial hemorrhage
The CT is examined for evidence of vascular occlusion (clots), edema, and hemorrhage
General considerations
Stroke anatomy
Hemorrhagic CVA Nonhemorrhagic (ischemic) CVA
Cerebral vascular supply (Circle of Willis) The motor and sensory Homunculus Arterial supply and brain function
General considerations CT findings
General considerations CT scan of hemorrhagic CVAs
Basal ganglia location
Cerebellar location
Gross pathology of cortical CVA
Hypertensive hemorrhage
in the basil ganglia
Hemorrhagic strokes are due to rupture of a cerebral blood vessel
Bleeding can occur into or around the brain
Blood may extend into the ventricular system
Hemorrhagic strokes account for 16% of all strokes
Hypertensive hemorrhage accounts for approximately 70-90% of non-traumatic primary intracerebral hemorrhages
Etiologies include thrombus, embolism, or hypoperfusion
Ischemic brain tissue becomes edematous Edematous tissue will appear hypodense on
noncontrast CT
Hypodensity begins as early as 1h post-CVA▪ Earliest sign of CVA is loss of gray-white differentiation (the "insular
ribbon" sign)
Hypodensity is completely manifest by 12-24 hours post-CVA
Obscuration of the lentiform nuclei Hypoattenuation of the insular ribbon Sulcal effacement and cortical hypodensity Hyperdense vessel signs
Lentiform nuclei = globbus palladus and putamen (parts of the basal ganglia)
Edema from ischemia produces hypodenity of basasl ganglia structures within hours of event
Red arrows denotes hypodensity of the basal ganglia structures (compare to opposite side)
An occluded vessel (thrombus) may appear ”dark” on CT
The red arrow denotes a dense basilar artery
Red arrows point to hypodensity and sulcal effacement.
Note the generalized edematous appearance of the tissues within the middle cerebral artery distribution
Moderate - severe head trauma is an indication for a CT head scan
Some controversy exists as to when a CT should be obtained for a “minor” head injury in adults:
Canadian CT recommendations
New Orleans Criteria
For infants and children:
Considerations
General recommendations
Things to Think About Interpretation Mnemonics Order of Evaluation (basic)
Bone windows
Blood (intracranial hemorrhage)
Brain parenchyma
Ventricles
Cisterns
Introduction CT considerations and clinical importance Diagrams
Ventricular anatomy
CSF circulation
CT images
Normal lateral ventricles
Normal third ventricle
Ventriculomegaly
Ventricular compression and enlargement
Brain parenchyma = brain “tissue” The brain parenchyma is symmetrical Gray and white matter should be well defined
Edema results in poor delineation
Midline structures (falx cerebri, third and fourth ventricles) should not be deviated
Deviated midline structures is evidence of mass effect = edema, bleeding, tumor
Check the parenchyma for evidence of blood
General considerations CT images
Normal midline structures
Midline shift
Cerebral edema
Notice the sharp difference between the large hypodense edematous (red arrows) tissue and the remaining “normal” cortical tissue
Used with permission by the CRASH Trials with credit to Mr. J. Wasserberg and Mr. B. Mitchell
Noncontrast study is standard A contrast study will be so designated on the CT images
Most scanners are now “ultrafast” and can perform a head CT in less than one minute
Scan spans from the base of the occiput to the top of the vertex in 5-mm increments
Three sets of data are derived from the primary scan: Bone windows (fractures)
Tissue windows (gray/white matter density)
Subdural windows (brain bleed)
Evaluation of head trauma
▪ Cerebral hemorrhages
▪ Skull fracture
Suspected cerebrovascular accident (CVA)
Suspected brain tumor
Hydrocephalus
Clinical syndromes CT indications versus MRI
Progressive headaches associated with:
Vomiting (especially early AM)
Behavior changes
CT Fast, easy, available, and
relatively cheap Study of choice for
suspected brain bleed Generally good for solid
organs and bleeds Good study for chest,
abdomen, and pelvis pathology
Radiation exposure
MRI Slower and more expensive Soft tissue and joints Spine and spinal cord Posterior fossa and orbits Better for CNS
developmental applications
Can’t be used with certain pacemakers and (metal) implants
Relative Density (Attenuation) Radiation Exposure CT protocols
Noncontrast (“standard”)
With contrast (“enhanced”)
IV contrast – general considerations Clinical indications Contraindications
I.V. contrast is given to differentiate blood vessels from soft tissue and organs Blood and falx appear white with contrast
Original ionic contrast agents have largely been replaced with nonionic agents (fewer reactions) Iodine reactions were actually responses to the carrier
molecule of the contrast rather than iodine Risk related to IV contrast: Anaphylaxis ~ 1:10,000 Death ~ 1:40,000 – 100,000
NPO X 4 hours before administration of IV contrast Depends on urgency of exam
Quick Easy Available Inexpensive (fairly) Standard of care for closed head injury
evaluation
Shows bony calvarium well
▪ Bone windows can show fractures easily
“The five B’s” Blood Brain Bone Balloons (ventricles) Boxes (cisterns)
“Blood Can Be Very Bad” Blood = blood Can = cisterns Be = brain Very = ventricles Bad = bone
Just like a standard X-ray, the CT shows dense objects (bone) as white and less dense objects (air) as black.
The concept of relative density is known as attenuation and is measured in Hounsfield Units (HU)
Structure Hounsfield Units Bone + 1,000 Blood + 50-100 Gray matter + 32 - 46 White matter + 22 - 36 CSF + 4 - 10 Water 0 Air -1,000
Clincal caveat: The radioglogist can place the computer cursor on any part of the CT image and determine the exact HU density – a real time way to differentiate blood from abscess from CSF, etc.
The CT scan is a sophisticated x-ray that literally takes a continuous x-ray as it moves around the patient (tomogram)
The X-ray source and detector unit are situated opposite of each other 360 degree movement around the patient Very thin x-ray beams are utilized
The CT computer integrates the assembled x-ray information and produces a “relative density” map that we view as a gray-scale image.
Type of Exposure Dosage (mSv) Background radiation 3 mSv/year CXR 0.1 mSv CT head 2 mSv CT chest 8 mSv CT abdomen and pelvis 20mSv
Caveat: A CT head is the equivalent of 20 CXRs, while a CT abdomen & pelvis equals 200 CXRs! Yikes!
General considerations CT Description CT images
Normal supracellar cistern
Normal quadrigeminal cistern
Compression of supracellar cistern (early)
Notice how the right uncus is pushing into the supracellar cistern.
Dx: Early uncal herniation from increased intracranial pressure
From Latin (“box”) Collections of CSF within the subarachnoid space
(between the pia and arachnoid membranes) Cistern pathology is usually seen on CT as
compression or presence of blood
Compression
▪ Increased intracranial pressure (herniation symndrome)
▪ Mass effect (tumor)
Several cisterns are described but two are of importance in the CT head:
Supracellar cistern▪ Star-shaped (“super star”)
▪ Location = Circle of Willis
Quadrigeminal cistern▪ W-shaped (looks like a baby’s bottom)
▪ Location = Level of tentorium cerebelli
A. Falx Cerebri
B. Frontal Lobe
C. Anterior Horn of Lateral Ventricle
D. Third Ventricle
E. Quadrigemina Cistern
F. Cerebellum
Can you visualize the
“baby’s bottom”?
Notice how the falx is deviated (white arrow) due to a space filling lesion (red outline)
Developed from a series of patients ( > 16 years-of-age) presenting with minor head injury (defined as GCS score of 13-15 after loss of consciousness, definite amnesia, or witnessed disorientation from trauma)
Clinical criteria consist of five high-risk and two moderate-risk factors.
Obtain CT Head if patient has > one the following seven:
GCS score lower than 15 two hours after injury Suspected open or depressed skull fracture Any sign of basal skull fracture Two or more episodes of vomiting Age 65 years or older Retrograde amnesia > 30 minutes Dangerous mechanism Motor vehicle involved
Fall from a height of at least three ft or five stairs
CT is needed if the patient > one of the following:
Headache
Vomiting
Age older than 60 years
Drug or alcohol intoxication
Persistent anterograde amnesia (deficits in short-term memory)
Visible trauma above the clavicle
Seizure
*Applicable for adults with a normal Glasgow Coma Scale score of 15 and blunt
head trauma that occurred within the previous 24 hours that caused loss of consciousness, definite amnesia, or witnessed disorientation.
Evaluate the significance of the injury by physical findings AND mechanism of injury
Kids have heavy heads and weak necks
Younger children are less likely to be symptomatic
Signs of significant head injury can be subtle (persistent irritability)
Scalp hematomas in infants and toddlers suggest significant injury
All moderate and severe head trauma Any loss of consciousness Age under 3 months
Skull fracture (intracranial injury in 15-30%)
Scalp hematoma predicts fracture (>80% sensitivity) Depressed mental status Focal neurologic deficits Bulging fontanelle Persistent irritability after head injury Seizure following head injury Recurrent vomiting after injury
Bone windows for fractures Brain tissue
Hemorrhage or masses
Symmetry
Midline shift
Edema
Ventricles
Compression, blood, or hydrocephalus
Subarachnoid cistern compression
The head contains four things (skull, brain, blood, spinal fluid)
The CT is reviewed to make sure all four are in the right amount and location
The brain is symmetrical; asymmetry is abnormal
The cerebral hemispheres are mirror image structures - what is on the left should be on the right
Prior contrast reaction (“iodine allergy”) Poor renal function
Creatinine > 2.0
Lack of consent Suspend breast feedings for 24 hours
following I.V. contrast
Shellfish and/or Betadyne allergies are not contraindications
A. Orbit E. Mastoid Air Cells
B. Sphenoid Sinus F. Cerebellar Hemisphere
C.Temporal Lobe
D. External Auditory Canal
A. Orbit
B. Sphenoid Sinus
C. Temporal Lobe
D. External Auditory Canal
E. Mastoid Air Cells
F. Cerebellar Hemisphere
Used with permission University of Virginia Health Sciences Center
A. Frontal Lobe
B. Frontal Bone
(Superior Surface of Orbit)
C. Dorsum Sellae
D. Basilar Artery
E. Temporal Lobe
F. Mastoid Air Cells
G. Cerebellar Hemisphere
Used with permission University of Virginia Health Sciences Center
A. Frontal Lobe
B. Sylvian Fissure
C. Temporal Lobe
D. Suprasellar Cistern
E. Midbrain
F. Fourth Ventricle
G. Cerebellar Hemisphere
Used with permission University of Virginia Health Sciences Center
A. Frontal Lobe
B. Falx Cerebri
C.Anterior Horn of Lateral
Ventricle
D.Third Ventricle
E. Quadrigeminal Plate
Cistern
F. Cerebellum
Used with permission University of Virginia Health Sciences Center
A. Anterior Horn of the Lateral Ventricle
B. Caudate Nucleus
C. Anterior Limb of the Internal Capsule
D. Putamen and Globus Pallidus
E. Posterior Limb of the Internal Capsule
F. Third Ventricle
G. Quadrigeminal Plate Cistern
H. Cerebellar Vermis
I. Occipital Lobe
Used with permission University of Virginia Health Sciences Center
A. Genu of the Corpus Callosum
B. Anterior Horn of the Lateral Ventricle
C. Internal Capsule
D. Thalamus
E. Pineal Gland
F. Choroid Plexus
G. Straight Sinus
Used with permission University of Virginia Health Sciences Center
A. Falx Cerebri
B. Frontal Lobe
C. Body of the Lateral Ventricle
D. Splenium of the Corpus Callosum
E. Parietal Lobe
F. Occipital Lobe
G. Superior Sagittal Sinus
Used with permission University of Virginia Health Sciences Center
A. Falx Cerebri
B. Sulcus
C. Gyrus
D. Superior Sagittal Sinus
Used with permission University of Virginia Health Sciences Center
Supracellar cisterrn
(can you visualize the “star” shape)
F = frontal lobes
U = uncus (medial temporal lobes)
Po = Pons
Fourth Ventricle
Dura (retracted)Bridging vein(s)
Subdural bleed
1 - Anterior Fossa
2- Posterior Fossa
3- Frontal Sinus
4- Esphenoid Sinus
5- Tentorium Cerebelli
Majority are due to aneurysms or arterioventricular malformations (AVM)
Bleeding is into the CSF space Ability to diagnose with CT decreases with
time: ▪ 95% positive at 12 hours
▪ 80% positive at 3 days
▪ 30% positive at two weeks
Berry aneurysm
Below the dura but above the arachnoid Usually venous in origin
Commonly a ruptured bridging vein (dural drainage)
Cresent or sickle shaped pattern on CT
Can cross suture lines Common in elderly or anti-coagulated Density of blood determines the age of the bleed:
Acute
Chronic
aka “intracerebral” hemorrhage Can follow hypertensive stroke Can follow deceleration (“contusion”) injuries Can extend into the ventricles (intracerebral
extension)
Hemorrhage into the ventricular system Can be an extension of an intraparenchymal
or subarachnoid bleed Can be secondary to trauma (poor outcome) Not uncommon in extremely premature
infants Obstructive hydrocephalus can be a
complication
Arterial blood Usually secondary to a linear skull fracture through an arterial
channel (like the middle meningeal artery)
Biconvex shape (lens shaped) Bleeding may cross the midline Bleeding won’t cross suture lines A subdural and an epidural may occur together Epi vs. sub doesn’t matter – but volume does
> 5 mm or > 10 mm in adults = surgical evacuation
Early ICP Findings Headache Vomiting Vision distortion Decreased sensorium Papilledema possible
Late ICP Findings Cushings triad
Hypertension
Bradycardia
Flexor/extensor posturing
Pupillary dysfunction
Haydel MJ, Preston CA, Mills TJ, Luber S, Blaudeau E, DeBlieux PM. Indications for computed tomography in patients with minor head injury. N Engl J Med. 2000;343:100-5.
Stiell IG, et al. Comparison of the Canadian CT Head Rule and the New Orleans Criteria in patients with minor head injury. JAMA. 2005;294:1511-8.
www.aafp.org/online/en/home/clinical/clinicalrecs/headinjurychild.html
Basic properties Skull fractures Suture lines versus fracture lines Basilar skull fracture Child abuse and skull fractures
Fracture in any
location other than
parietal location
Non-linear fracture
Linear fracture length
exceeding 6 cm
Fracture crossing
suture lines
The bone windows information is part of the routine CT head and is ideal for viewing fractures
Sinuses can be seen well with bone windows The scout film of the CT scan is roughly the equivalent of
a lateral skull x-ray film – so look at it too Remember to look at the overlying soft tissue for
swelling as it may point to an underlying skull fracture
Skull fractures may be classified as either linear or comminuted
Inwardly displaced comminuted = depressed skull fx
▪ A depressed skull fracture requires immediate neurosurgical evaluation
Cranial sutures can be confused with linear fractures
Suture Fracture
Characteristic locations Usually temperoparietal
Symmetrical line on other side Asymmetrical
Same size throughout Widest at the center/ narrow at the end
Graceful curvy lines Straight lines with angular turns
A fracture of the orbital roof, sphenoid bone, or mastoid portion of temporal bone
Usually resolve on their own but can be:
Displaced
Cranial nerve damage (II, VII, VIII)
CSF leak (otorhea or rhinorhea)
“Classic” clinical findings may (or may not) be present
Hemotympanum Periorbital bruising ("raccoon eyes“) Cerebrospinal fluid otorrhea or rhinorrhea Battle's sign (Mastoid eccymoses) Pneumocephalus
(Air and fluid/levels in sinuses)
Superior to inferior
Falx cerebri
Body of lateral ventricles
Internal capsule and thalamus
Caudate and third ventricle
3rd Ventricle and quadrigeminal cistern
Supracellar cistern and 4th ventricle
Extra-axial hemorrhage (outside the brain)
Epidural
Below the skull
“above” the dura
Subdural
Below the dura
Above the thin, spidery-like arachnoid membrane
Intra-axial hemorrhage (inside the brain)
Subarachnoid (SAH) Below the arachnoid membrane
On the surface of the brain
Intraparenchymal (IPH) Within the substance of the
brain
Intraventricular (IVH) Within the ventricles
CSF-filled balloons CSF is produced in the
choroid plexes, “circulates” through the ventricular system, percolates over the surface of the cord and brain, and is absorbed in the arachnoid granulations
CSF Direction of Flow:
Lateral ventricles
Foramen of Monroe
Third ventricle
Cerebral aqueduct
Fourth ventricle
Foramen (Magendie and Lushka)
Subarachnoid space
Arachnoid granulations
Venous circulation
Size Large = too much fluid or brain atrophy
Small = Compression (edema or mass) Symmetry Asymmetry = impingement from mass/edema, etc.
Presence of blood IVH can lead to secondary hydrocephalus
Anatomic landmarks Lateral and 3rd ventricle are supratentorial
▪ 3rd is located anterior to the pineal gland
▪ Looks like an exclamation point
4th ventricle is infratentorial ▪ Looks like a pith helmet (roundish)
Considerations Ventricular system CSF circulation CT images:
Hydrocephalus
Asymmetry (impingement from tumor)
IVH
A tough, fibrous structure separating the cerebrum above and the cerebellum and brain stem below
Provides support for the cerebrum Structures above the tentorium are known as
supratentorial or anterior fossa Structures below the tentorium are known as
infratentorial or posterior fossa
1 - Anterior Fossa
2- Posterior Fossa
3- Frontal Sinus
4- Esphenoid Sinus
5- Tentorium Cerebelli
Frontal Parietal Occipital Temporal
Note collection of blood above the dura mater
Dura mater
Ruptured berry aneurysm
Majority can be visualized without contrast Contrast is indicated if brain tumor is suspected and
not see on noncontrast study Appear as edematous, low density, poorly-
defined lesions Classified as intraaxial (within the brain tissue) or
extraaxial Adult tumors are usually supratentorial while
pediatric tumors are usually infratentorial Many metastatic tumors will be located at the
gray-white matter border(s)
General considerations Brain tumors
Meningioma
Astrocytoma (pediatric)
Cystic mass in the midline of the cerebellum (red arrows)
Note early hydrocephalic changes secondary to tumor compression (yellow arrows)
Red arrow points to a large cerebellar hemorrhage
Used with permission University of Virginia Health Sciences Center
Cocaine induced hypertensive CVA
Note the large hemorrhagic lesion in the left cortical area as well as multiple smaller regions (redness) near the hippocampus and other cortical regions.
www.utsa.edu/tsi/assign/anat/neuropat.htm
Loss of the gray-white interface in the lateral margins of the insula
The cortex of the left insular ribbon is not visualized (arrow).
Right insular ribbon is outlined in yellow
Contrast enhanced CT of meningioma (most common extraxial brain tumor)
Used with permission by the CRASH Trials with credit to Mr. J. Wasserberg and Mr. B. Mitchell
A. Falx Cerebri
B. Frontal Lobe
C. Body of the Lateral
Ventricle
D. Splenium of the Corpus
Callosum
E. Parietal Lobe
F. Occipital Lobe
G. Superior Sagittal Sinus
Used with permission University of Virginia Health Sciences Center
Edema
Blood
The darker gray areas represent edema while the white areas represent the intracerebral contrusion (“bruise”)
Edema
Blood
Used with permission by the CRASH Trials with credit to Mr. J. Wasserberg and Mr. B. Mitchell
Used with permission by the CRASH Trials with credit to Mr. J. Wasserberg and Mr. B. Mitchell
Small red arrows point to a biconvex epidural hematoma secondary to a skull fracture (large red arrow)
Used with permission University of Virginia Health Sciences Center
Red arrows denote blood within the sulci of the right cerebral convexity
Used with permission University of Virginia Health Sciences Center
The large red arrow points to blood within the ventricle while the smaller red arrows point to blood in the sulci (subarachnoid hemorrhage)
Used with permission University of Virginia Health Sciences Center
Linear skull fracture (parietal location) found on bone windows image
Frontal Parietal Occipital Temporal
The cortical areas of the brain devoted to motor (frontal motor strip) and sensory (parietal sensory strip) function can be represented as an “upside” down person.
A disruption in cerebral blood flow to these areas will result in a corresponding sensory and/or motor deficit to the corresponding region.
Artery Lobes Supplied Deficit
ACA Frontal Leg weakness
MCA Frontal SpeechLateral Temporal Motor and sensory Lateral Parietal to hand and arm
PCA Temporal Visual defectsOccipital
Patient MRINormal MRI
