n806 and ct head

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