n806 and ct head

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CT radiologyCT anatomyGlossary of termsClinical indicationsSystematic interpretationHead traumaStrokeTumor

Intracranial Pathology and Computerized Tomography of the Head

CT Contrast Indications

Brain mets/tumorInfection/abscessNodes/massesPulmonary embolismAbdomen/pelvis

Ventriculomegaly

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

Glossary of TermsTerms beginning with A MTerms beginning with N - Z

Glossary of Terms: A - MAmnesiaArachnoid granulationsArachnoid membraneBasal gangliaBasilar ArteryCalvariumCaudate (see basal ganglia)CerebellumCerebral cortexChoroid plexusCircle of Willis

Cistern(s)Corpus callosumDorsum SellaeDura materFalx cerebriGlobus pallidus (see basal ganglia)GyrusHerniationInsula/insullar ribbonInternal capsuleLentiform nuclei (see basal ganglia)MedullaMidbrain

Herniation (Brain)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 tentoriumSymptoms include headache, decreased consciousness, pupillary dilation and may progress to extensor posturing and death Cerebellar herniation (rare)Cerebellar tonsils are pushed into the foramen magnumSimilar symptoms as transtentorial herniation

Cerebrum and cerebral cortexThe 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 cerebrumThe outer layer of the cerebrum (cortex) is gray matter (lacks myelin)

Amnesia: Anterograde vs. RetrogradeAnterograde 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.

Arachnoid granulations

From the Greek arakhnoeids, (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

Arachnoid membraneA 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.

Basal gangliaThe basasl ganglia consists of three gray matter structures (caudate, putamen, and globus pallidus) deep within cerebral hemispheresLentiform nuclei = putamen and globus pallidusFunctions as motor relay stationsPathology in the basal ganglia results in purposeless movements (Parkinsons disease)

Basilar ArteryThe 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.

Circle of WillisThe 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

Calvarium

The bony roof of the skull; also know as the skull cap.

Cerebellum

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

Choroid plexus

Ventricluar tissue (ependyma) that produces cerebral spinal fluid (CSF).

Cistern(s)

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 WillisQuadrigeminal - W-shaped at top of midbrain

Corpus callosumThe corpus callosum is the structure that connects the left and right cerebral hemispheres.

Dorsum Sellae

The dorsum sellae is the square shaped part of the sphenoid bone that forms the posterior boundary of the pitutary fossa.

Dorsum sellae

Dura mater

Latin (hard mother)The outer, fibrous portion of the meninges.

Dura MaterEpidural hematoma

Brain

Falx cerebiA reflexion of the dura mater located between the cerebral hemispheres. Function is to provide support to the cerebral hemispheres.

Gyrus

The rounded, elevated convolutions on the surfaces of the cerebral hemispheres.

Insula/insullar ribbon

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.

Internal capsule

Collection of axons that carry sensory information to the cortex and motor information to the cord. The internal capsule is very sensitive to stroke

Medulla

Aka medulla oblongataLocated 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.

Brain stemIncludes the midbrain, pons, and medulla. Major function is survival (breathing, digestion, heart rate, blood pressure) and for arousal (being awake and alert).

Glossary of Terms: N - ZOccipital lobeParenchymaParietal lobePineal glandPneumocephalusPonsPosterior fossaPutamen (see globus pallidus)Sagittal sinus

Septum pellucidumSulcusSuture(s)Temporal lobeTentorium cerebelliThalamusUncusVentricle(s)

PneumocephalusPneumocephalus (see red arrow) is the presence of air (or gas) within the cranial cavity and is usually associated with a basilar skull fracture

Suture(s)

Suture(s)The sutures are fibrous connections between bones of the skullSutures allow for some flexibility of the craniumFontanelles (aka soft spots) are unfused areas where sutures meetSutures ossify at various times throughout life

PonsThe pons sits between the brainstem and medulla Controls rate and depth of breathingRelays impulse from medulla to cerebrumClinical pathology results in:Bilateral, fixed, pinpoint pupils (comatose patient)Cheyne-Stokes breathing Hyperventialtion followed by apnea

Pons

UncusThe uncus is the medial (innermost) portion of the temporal lobeUnder high intracranial pressure (ICP) the uncus can be involved in a transtentorial herniation syndromeICP pushes the uncus through the tentorium cerebelli which results in compression of the brainstem

The brain squeezes under the falx cerebri in cingulate herniationThe brainstem herniates caudallyThe uncus and the hippocampal gyrus herniate into the tentorial notchThe cerebellar tonsils herniate through the foramen magnum in tonsillar herniation Brain Herniation Syndromes

VentriclesThe 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

ThalamusThe thalamus is the central relay station for sensory fibers (except olfactory)Cerebral cortex communicates with thalamusResponsible for primitive emotional responsesFearPleasant vs. unpleasant stimuli

Temporal LobeThe temporal lobes are one of the five cortical lobesThe temporal lobes are responsible for hearing, speech, and some emotional and memory functions

SulcusLain groove or trenchPleural sulci (sul-sigh)The small cracks or dimples on the surface of the brain

Septum PellucidumThe septum pellucidum is a thin midline structural membraneThe septum runs vertically between the lateral ventricles as well as inferiorly from the corpus callosum

Sagittal SinusAka superior sagittal sinusLarge collection of venous blood above and behind the brainAttached to the falx cerebriReceives CSF from the arachnoid granulations

Posterior FossaThe posterior fossa is an area within the intracranial cavity bound by the tentorium cerebelli above and foramen magnum belowThe posterior fossa contains the cerebellum and brainstem structures

Pineal glandAka pineal bodyThe pineal glad is an endocrine gland that produces melatonin and is important in sleep-wake cycles

Parietal LobeThe parietal lobe is the cortical lobe responsible for sensation (cutaneous and muscular)Responsible for integration of thoughts and feelings

ParenchymaThe functional tissue(s) (key elements) of an organ

Occipital LobeThe occipital lobe is the cortical lobe responsible for visionIntegration areas for visual images with sensory experiences.Dura matter (tentorium cerebelli) separates the occipital lobe from the cerebellum

PutamenThe putamen is part of the basasl gangliaThe basals ganglia consists of three gray matter structures (caudate, putamen, and globus pallidus) deep within cerebral hemispheresLentiform nuclei = putamen and globus pallidusFunctions as motor relay stationsPathology in the basal ganglia results in purposeless movements (Parkinsons disease)

StrokeCT head is currently the procedure of choice for evaluation of suspected strokeStokes 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 agentsThe CT can reliably serve to rule out intracranial hemorrhageThe CT is examined for evidence of vascular occlusion (clots), edema, and hemorrhage

StrokeGeneral considerationsStroke anatomyHemorrhagic CVA Nonhemorrhagic (ischemic) CVA

Stroke Anatomy

Cerebral vascular supply (Circle of Willis)The motor and sensory HomunculusArterial supply and brain function

Nonhemorrhagic (ischemic) CVAGeneral considerations CT findings

Hemorrhagic StrokeGeneral considerationsCT scan of hemorrhagic CVAsBasal ganglia locationCerebellar location Gross pathology of cortical CVA

Hypertensive hemorrhage in the basil ganglia

CT of Hemorrhagic Stroke

Hemorrhagic CVAHemorrhagic strokes are due to rupture of a cerebral blood vessel Bleeding can occur into or around the brainBlood may extend into the ventricular system Hemorrhagic strokes account for 16% of all strokesHypertensive hemorrhage accounts for approximately 70-90% of non-traumatic primary intracerebral hemorrhages

Stroke: IschemicEtiologies include thrombus, embolism, or hypoperfusionIschemic brain tissue becomes edematous Edematous tissue will appear hypodense on noncontrast CT Hypodensity begins as early as 1h post-CVAEarliest sign of CVA is loss of gray-white differentiation (the "insular ribbon" sign)Hypodensity is completely manifest by 12-24 hours post-CVA

CT Evidence of Ischemic CVAObscuration of the lentiform nucleiHypoattenuation of the insular ribbon Sulcal effacement and cortical hypodensityHyperdense vessel signs

Ischemic CVA: Obscuration of the Lentiform Nuclei

Lentiform nuclei = globbus palladus and putamen (parts of the basal ganglia)Edema from ischemia produces hypodenity of basasl ganglia structures within hours of eventRed arrows denotes hypodensity of the basal ganglia structures (compare to opposite side)

Ischemic CVA: Hyperdense Vessels(s)An occluded vessel (thrombus) may appear dark on CT The red arrow denotes a dense basilar artery

Ischemic CVA: Sulcal Effacement & Cortical Hypodensity

Red arrows point to hypodensity and sulcal effacement. Note the generalized edematous appearance of the tissues within the middle cerebral artery distribution

Head Injury and CT: RecommendationsModerate - severe head trauma is an indication for a CT head scanSome controversy exists as to when a CT should be obtained for a minor head injury in adults:Canadian CT recommendationsNew Orleans CriteriaFor infants and children:ConsiderationsGeneral recommendations

Things to Think AboutInterpretation MnemonicsOrder of Evaluation (basic)Bone windowsBlood (intracranial hemorrhage)Brain parenchymaVentriclesCisterns

Systematic Interpretation

VentriclesIntroductionCT considerations and clinical importanceDiagramsVentricular anatomyCSF circulationCT imagesNormal lateral ventriclesNormal third ventricleVentriculomegalyVentricular compression and enlargement

ParenchymaBrain parenchyma = brain tissueThe brain parenchyma is symmetricalGray and white matter should be well definedEdema results in poor delineationMidline structures (falx cerebri, third and fourth ventricles) should not be deviatedDeviated midline structures is evidence of mass effect = edema, bleeding, tumorCheck the parenchyma for evidence of blood

ParenchymaGeneral considerationsCT imagesNormal midline structuresMidline shiftCerebral 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

CT Head: Standard ProtocolNoncontrast study is standardA contrast study will be so designated on the CT imagesMost scanners are now ultrafast and can perform a head CT in less than one minuteScan 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)

CT Head: IndicationsEvaluation of head traumaCerebral hemorrhagesSkull fractureSuspected cerebrovascular accident (CVA)Suspected brain tumor Hydrocephalus

CT Head: IndicationsClinical syndromesCT indications versus MRI

CT Indications: Signs & SymptomsProgressive headaches associated with:Vomiting (especially early AM)Behavior changes

CT vs. MRI: ConsiderationsCTFast, easy, available, and relatively cheapStudy of choice for suspected brain bleedGenerally good for solid organs and bleedsGood study for chest, abdomen, and pelvis pathologyRadiation exposure

MRISlower and more expensiveSoft tissue and jointsSpine and spinal cord Posterior fossa and orbitsBetter for CNS developmental applicationsCant be used with certain pacemakers and (metal) implants

CT: RadiologyRelative Density (Attenuation)Radiation ExposureCT protocols Noncontrast (standard)With contrast (enhanced)

CT Head: Contrast StudyIV contrast general considerationsClinical indicationsContraindications

I.V. contrast is given to differentiate blood vessels from soft tissue and organs Blood and falx appear white with contrastOriginal 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 iodineRisk related to IV contrast:Anaphylaxis ~ 1:10,000Death ~ 1:40,000 100,000NPO X 4 hours before administration of IV contrastDepends on urgency of exam

IV Contrast: Considerations

CT Head

QuickEasyAvailableInexpensive (fairly)Standard of care for closed head injury evaluationShows bony calvarium wellBone windows can show fractures easily

CT Head: What to Look AtThe five BsBloodBrainBoneBalloons (ventricles)Boxes (cisterns)

Blood Can Be Very BadBlood = bloodCan = cisternsBe = brainVery = ventriclesBad = bone

CT Physics: Hounsfield UnitsJust 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)

Relative DensityStructureHounsfield UnitsBone + 1,000Blood + 50-100Gray matter + 32 - 46 White matter + 22 - 36CSF+ 4 - 10Water0Air -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.

CT PhysicsThe 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 other360 degree movement around the patientVery thin x-ray beams are utilizedThe CT computer integrates the assembled x-ray information and produces a relative density map that we view as a gray-scale image.

CT RadiationType of ExposureDosage (mSv)Background radiation3 mSv/yearCXR0.1 mSvCT head2 mSvCT chest8 mSvCT abdomen and pelvis20mSv

Caveat: A CT head is the equivalent of 20 CXRs, while a CT abdomen & pelvis equals 200 CXRs! Yikes!

CisternsGeneral considerationsCT DescriptionCT imagesNormal supracellar cisternNormal quadrigeminal cisternCompression of supracellar cistern (early)

Notice how the right uncus is pushing into the supracellar cistern. Dx: Early uncal herniation from increased intracranial pressure

Cisterns: General ConsiderationsFrom 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 bloodCompressionIncreased intracranial pressure (herniation symndrome)Mass effect (tumor)

Cisterns: CT DescriptionSeveral cisterns are described but two are of importance in the CT head:Supracellar cisternStar-shaped (super star) Location = Circle of WillisQuadrigeminal cisternW-shaped (looks like a babys bottom)Location = Level of tentorium cerebelli

A. Falx CerebriB. Frontal LobeC. Anterior Horn of Lateral VentricleD. Third VentricleE. Quadrigemina CisternF. Cerebellum

Can you visualize the babys bottom?

Notice how the falx is deviated (white arrow) due to a space filling lesion (red outline)

Canadian CT Head RulesDeveloped 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.

Canadian CT Head CriteriaObtain CT Head if patient has > one the following seven:GCS score lower than 15 two hours after injurySuspected open or depressed skull fractureAny sign of basal skull fracture Two or more episodes of vomitingAge 65 years or olderRetrograde amnesia > 30 minutesDangerous mechanismMotor vehicle involvedFall from a height of at least three ft or five stairs

CT is needed if the patient > one of the following:HeadacheVomitingAge older than 60 yearsDrug or alcohol intoxicationPersistent anterograde amnesia (deficits in short-term memory)Visible trauma above the clavicleSeizure

*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.

New Orleans Criteria: Head CT and Minor Head Injury*

Evaluate the significance of the injury by physical findings AND mechanism of injuryKids 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

Pediatric Head Trauma: Considerations

CT Head: PediatricsAll moderate and severe head traumaAny 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 fontanellePersistent irritability after head injurySeizure following head injuryRecurrent vomiting after injury

CT Head: Order of EvaluationBone windows for fractures Brain tissueHemorrhage or massesSymmetryMidline shiftEdemaVentriclesCompression, blood, or hydrocephalusSubarachnoid cistern compression

Interpretation: Things to RememberThe head contains four things (skull, brain, blood, spinal fluid) The CT is reviewed to make sure all four are in the right amount and locationThe brain is symmetrical; asymmetry is abnormalThe cerebral hemispheres are mirror image structures - what is on the left should be on the right

CT Contrast: ContraindicationsPrior contrast reaction (iodine allergy)Poor renal functionCreatinine > 2.0Lack of consentSuspend breast feedings for 24 hours following I.V. contrast

Shellfish and/or Betadyne allergies are not contraindications

Orbit E. Mastoid Air CellsSphenoid SinusF. Cerebellar HemisphereTemporal LobeD. External Auditory CanalA. OrbitB. Sphenoid SinusC. Temporal LobeD. External Auditory CanalE. Mastoid Air CellsF. Cerebellar Hemisphere

Used with permission University of Virginia Health Sciences Center

A. Frontal LobeB. Frontal Bone (Superior Surface of Orbit)C. Dorsum SellaeD. Basilar ArteryE. Temporal LobeF. Mastoid Air CellsG. Cerebellar Hemisphere


A. Frontal LobeB. Sylvian FissureC. Temporal LobeD. Suprasellar CisternE. MidbrainF. Fourth VentricleG. Cerebellar Hemisphere


Frontal LobeFalx CerebriAnterior Horn of Lateral VentricleThird VentricleQuadrigeminal Plate CisternCerebellum


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A. Anterior Horn of the Lateral VentricleB. Caudate NucleusC. Anterior Limb of the Internal CapsuleD. Putamen and Globus PallidusE. Posterior Limb of the Internal CapsuleF. Third VentricleG. Quadrigeminal Plate CisternH. Cerebellar VermisI. Occipital Lobe


A. Genu of the Corpus CallosumB. Anterior Horn of the Lateral VentricleC. Internal CapsuleD. ThalamusE. Pineal GlandF. Choroid PlexusG. Straight Sinus


A. Falx CerebriB. Frontal LobeC. Body of the Lateral VentricleD. Splenium of the Corpus CallosumE. Parietal LobeF. Occipital LobeG. Superior Sagittal Sinus


A. Falx CerebriB. SulcusC. GyrusD. Superior Sagittal SinusUsed with permission University of Virginia Health Sciences Center

Supracellar cisterrn (can you visualize the star shape)F = frontal lobesU = uncus (medial temporal lobes)Po = PonsFourth Ventricle

Dura (retracted)

Bridging vein(s)

Subdural bleed

1 - Anterior Fossa 2- Posterior Fossa 3- Frontal Sinus4- Esphenoid Sinus 5- Tentorium Cerebelli

Majority are due to aneurysms or arterioventricular malformations (AVM)Bleeding is into the CSF spaceAbility to diagnose with CT decreases with time: 95% positive at 12 hours80% positive at 3 days30% positive at two weeks

Subarachnoid Hemorrhage

Berry aneurysm

Below the dura but above the arachnoidUsually venous in origin Commonly a ruptured bridging vein (dural drainage) Cresent or sickle shaped pattern on CTCan cross suture linesCommon in elderly or anti-coagulatedDensity of blood determines the age of the bleed:AcuteChronic

Subdural

Intrparenchymal Hemorrhageaka intracerebral hemorrhageCan follow hypertensive strokeCan follow deceleration (contusion) injuriesCan extend into the ventricles (intracerebral extension)

Intraventricular HemorrhageHemorrhage into the ventricular systemCan be an extension of an intraparenchymal or subarachnoid bleedCan be secondary to trauma (poor outcome)Not uncommon in extremely premature infantsObstructive hydrocephalus can be a complication

Epidural (Above the Dura)Arterial bloodUsually secondary to a linear skull fracture through an arterial channel (like the middle meningeal artery)Biconvex shape (lens shaped)Bleeding may cross the midlineBleeding wont cross suture linesA subdural and an epidural may occur together Epi vs. sub doesnt matter but volume does> 5 mm or > 10 mm in adults = surgical evacuation

ICP: Signs and SymptomsEarly ICP FindingsHeadacheVomitingVision distortionDecreased sensoriumPapilledema possible

Late ICP FindingsCushings triadHypertensionBradycardiaFlexor/extensor posturingPupillary 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

Bone WindowsBasic propertiesSkull fracturesSuture lines versus fracture linesBasilar skull fractureChild abuse and skull fractures

Skull Fx and Risk of Child AbuseFracture in any location other than parietal locationNon-linear fractureLinear fracture length exceeding 6 cmFracture crossing suture lines

Bone WindowsThe bone windows information is part of the routine CT head and is ideal for viewing fracturesSinuses can be seen well with bone windowsThe scout film of the CT scan is roughly the equivalent of a lateral skull x-ray film so look at it tooRemember to look at the overlying soft tissue for swelling as it may point to an underlying skull fracture

Skull FracturesSkull fractures may be classified as either linear or comminuted Inwardly displaced comminuted = depressed skull fxA depressed skull fracture requires immediate neurosurgical evaluationCranial sutures can be confused with linear fractures

Suture Lines vs. FracturesSutureFractureCharacteristic locationsUsually temperoparietal

Symmetrical line on other side Asymmetrical

Same size throughoutWidest at the center/ narrow at the end

Graceful curvy linesStraight lines with angular turns

Basilar Skull FractureA fracture of the orbital roof, sphenoid bone, or mastoid portion of temporal boneUsually resolve on their own but can be:DisplacedCranial nerve damage (II, VII, VIII)CSF leak (otorhea or rhinorhea)Classic clinical findings may (or may not) be present

Basilar Skull FractureHemotympanumPeriorbital bruising ("raccoon eyes) Cerebrospinal fluid otorrhea or rhinorrheaBattle's sign (Mastoid eccymoses) Pneumocephalus(Air and fluid/levels in sinuses)

CT Anatomy SlicesSuperior to inferiorFalx cerebriBody of lateral ventriclesInternal capsule and thalamusCaudate and third ventricle3rd Ventricle and quadrigeminal cisternSupracellar cistern and 4th ventricle

Head Bleeds: Location

Extra-axial hemorrhage (outside the brain)

Epidural Below the skull above the duraSubduralBelow the duraAbove the thin, spidery-like arachnoid membraneIntra-axial hemorrhage (inside the brain)

Subarachnoid (SAH)Below the arachnoid membraneOn the surface of the brainIntraparenchymal (IPH)Within the substance of the brainIntraventricular (IVH)Within the ventricles

CSF-filled balloonsCSF 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 granulationsCSF Direction of Flow:Lateral ventriclesForamen of Monroe Third ventricleCerebral aqueduct Fourth ventricleForamen (Magendie and Lushka)Subarachnoid spaceArachnoid granulationsVenous circulation

Ventricles

Ventricles: CT ConsiderationsSize Large = too much fluid or brain atrophySmall = Compression (edema or mass)Symmetry Asymmetry = impingement from mass/edema, etc.Presence of bloodIVH can lead to secondary hydrocephalusAnatomic landmarksLateral and 3rd ventricle are supratentorial3rd is located anterior to the pineal gland Looks like an exclamation point4th ventricle is infratentorial Looks like a pith helmet (roundish)

VentriclesConsiderationsVentricular systemCSF circulationCT images:HydrocephalusAsymmetry (impingement from tumor)IVH

Tentorium CerebelliA tough, fibrous structure separating the cerebrum above and the cerebellum and brain stem belowProvides support for the cerebrumStructures above the tentorium are known as supratentorial or anterior fossaStructures below the tentorium are known as infratentorial or posterior fossa

1 - Anterior Fossa 2- Posterior Fossa 3- Frontal Sinus4- Esphenoid Sinus 5- Tentorium Cerebelli

Frontal ParietalOccipitalTemporalCerebral Cortical Function

Note collection of blood above the dura mater

Dura mater

Ruptured berry aneurysm

Brain TumorsMajority can be visualized without contrastContrast is indicated if brain tumor is suspected and not see on noncontrast study Appear as edematous, low density, poorly-defined lesionsClassified as intraaxial (within the brain tissue) or extraaxialAdult tumors are usually supratentorial while pediatric tumors are usually infratentorialMany metastatic tumors will be located at the gray-white matter border(s)

Brain TumorsGeneral considerationsBrain tumorsMeningiomaAstrocytoma (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


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)

3rd and Lateral (Frontal Horns) Ventricles


A. Falx CerebriB. Frontal LobeC. Body of the Lateral VentricleD. Splenium of the Corpus CallosumE. Parietal LobeF. Occipital LobeG. Superior Sagittal Sinus


EdemaBlood

The darker gray areas represent edema while the white areas represent the intracerebral contrusion (bruise)

EdemaBlood


Subdural Hematoma


Epidural Hematoma

Small red arrows point to a biconvex epidural hematoma secondary to a skull fracture (large red arrow)


Subarachnoid HemorrhageRed arrows denote blood within the sulci of the right cerebral convexity


Intraventricular HemorrhageThe large red arrow points to blood within the ventricle while the smaller red arrows point to blood in the sulci (subarachnoid hemorrhage)


Linear Skull FractureLinear skull fracture (parietal location) found on bone windows image

Frontal ParietalOccipitalTemporalCerebral Cortical Function

The HomunculusThe 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.

Cerebral Arteries and Clinical DeficitsArteryLobes SuppliedDeficit

ACAFrontalLeg weakness

MCAFrontalSpeechLateral TemporalMotor and sensory Lateral Parietalto hand and arm PCATemporalVisual defectsOccipital

Patient MRINormal MRI

Circle of Willis

n806 and ct head

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