بسم الله الرحمن بسم الله الرحمن الرحيمالرحيم

BRAIN CT BRAIN CT IN EMERGENCYIN EMERGENCY

Lecture Objectives:Lecture Objectives:

• Normal anatomy of brain CT• Trumatic brain injury• Subarachnoid hemorrhage• Intraparenchymal hemorrhage• Stroke• Brain edema• Cerebral herniation

A. OrbitB. Sphenoid SinusC. Temporal LobeD.Externa Auditory CanalE. Mastoid Air CellsF. Cerebellar Hemisphere

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. 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 Sinus

CT SCAN..CT SCAN..

fractureBone window

CT SCAN..CT SCAN..

Contrast enhanced CT:IV injection of contrast medium is often given because the abnormality not seen in pre contrast scans may be rendered visible following contrast enhancement (consequence of breakdown of blood brain barrier allowing contrast to enter the lesion particularly in neoplasm, infection, inflammation and certain stage of ischemia).

Also it is helpful in demonstrating blood vessels

MCAACA

Basilar arteryStraight sinus

Superior sagittal sinus

Contrast enhanced CT

CT SCAN..CT SCAN..

Sagittal reconstruction Coronal reconstruction

Computer reconstructions Computer reconstructions can in selected circumstances can in selected circumstances

be made from the axial be made from the axial sections which then sections which then provide images in coronal provide images in coronal or sagittal planes.or sagittal planes.

CT SCAN..CT SCAN..

CTA

CT angiography is helpful in diagnosis of vascular diseases and abnormalities such as stenosis, occlusion or vascular malformation

Occlusion of left middle cerebral artery

Computed Tomographic Cerebral Venography (CTV)

CTVCan be reliably assess intracranial venous

system

Comparable to MR angiographic techniques

Rapid and readily available

Avoids many patient contraindications that may prevent MR evaluation

Using iodinated contrast material, requires complex post processing to remove bony structures from reconstructed images

CT SCAN..CT SCAN..

CT PERFUSION

cerebral blood volume cerebral blood flow

CT SCAN..CT SCAN..

In acute stroke, very early cranial CT may be normal. Perfusion CT shows great promise in refining the selection of patients suitable for thrombolysis, as it can accurately determine infarct core from potentially salvageable ischaemic penumbra.

Some cerebral tumours are associated with angiogenesis and a breakdown of the blood-brain barrier. Angiogenesis can be detected as an increase in flow and volume parameters, and blood-brain barrier breakdown can be quantified as contrast accumulates in the interstitial space. Such aggressive features can distinguish malignant from benign tumours when standard imaging may not.

CT PERFUSION

Traumatic brain injury:Traumatic brain injury:

• Primary:Primary:

• Extraaxial hemorrhage:Extraaxial hemorrhage:

- Epidural hematoma

- Subdural hematoma

- Subarachnoid hemorrhage

• Intraaxial lesions:Intraaxial lesions:

- Diffuse axonal injury

- Cortical contusion

- Deep gray matter injury

- Brainstem injury

- IVH

• Secondary:Secondary:

- Brain herniation

- Traumatic ischemia

- Diffuse cerebral edema

- Hypoxic brain injury

Epidural hematomaEpidural hematoma

• 90% is arterial (middle meningeal artery)

• Temporoparietal

• Biconvex, lenticular

• Does not cross suture lines, crosses dural reflections

• Commonly associated with skull fractures

CT SCAN..CT SCAN..

Acute extradural hemorrhage

Bone window Brain window

fracture

The window settings are selected for The window settings are selected for the brain, but may be altered to shows the brain, but may be altered to shows the bones. the bones.

Subdural hematomaSubdural hematoma

• Tear of cortical bridging veins

• Cresentric along the brain surface

• Crosses suture lines, does not cross dural reflections

• Common in infants (child abuse) and in the elderly

Subarachnoid hemorrhageSubarachnoid hemorrhage

• Hyperdense CSF in the basal cisterns, sylvian fissure and subarachnoid space

• Aneurysm rupture is the most common cause in non trauma patient

• Patients present with the worst headache of their life

Subarachnoid hemorrhageSubarachnoid hemorrhage

Subarachnoid hemorrhageSubarachnoid hemorrhage

• The pattern of hemorrhage may give a clue to the location of the ruptured aneurysm:

• A-com aneurysm ⇒ interhemispheric fissure• P-com aneurysm ⇒ ipsilateral basal cisterns• MCA trifurcation ⇒ sylvian fissure

• Basilar tip ⇒ interpeduncular cistern, intraventricular

• PICA ⇒ posterior fossa cisterns,

intraventricular

Pseudo-subarachnoid Pseudo-subarachnoid hemorrhagehemorrhage

• Symmetric increased density in the basal cisterns with no sulcal density

• 30-40 HU

• Assoaciated with generalized brain edema

• History of recent cardiopulmonary resuscitation

Diffuse axonal injuryDiffuse axonal injury

• Axonal disruption from shearing forces of acceleration/deceleration

• Patients are unconscious with severe head injury

• Common locations:

- Lobar gray/white matter junction

- Corpus callosum

- Dorsolateral brain stem

Diffuse axonal injuryDiffuse axonal injury

• Initial CT is often normal. Petechial hemorrhage develops later.

• Susceptibility-sensitive, gradient-echo MR sequences are most sensitive for detecting hemorrhagic shear injuries.

Diffuse axonal injuryDiffuse axonal injury

Cortical contusionsCortical contusions

• Focal hemorrhage/edema secondary to brain impacting on bone or dura

• Located 180 degrees from the site of direct impact (contrecoup)

• Characteristic locations:

- Anterior temporal

- Inferior frontal

- Parasagittal hemisphere

- Splenium of the corpus callosum

- Brainstem

Intra ventricular hemorrhageIntra ventricular hemorrhage

Intraparenchymal hemorrhageIntraparenchymal hemorrhage

• Causes: - Hypertension - Amyloid angiopathy - Vascular malformations - Coagulopathy - Trauma - Drug induced - Tumor hemorrhage

StrokeStroke

• Types:

- Ischemic stroke

- Hemorrhagic stroke

- Venous occlusion

Ischemic strokeIschemic stroke

• Nonenhanced CT is the initial investigation of choice

• Exclude hemorrhage and underlying mass or AVM

Imaging findings:• Normal in early stroke• Hyperdense clot in the affected artery• Insular ribbon sign• Sulcal effacement• Cytotoxic edema develops by 6 hours

Ischemic strokeIschemic stroke

• Acute infarction cannot be excluded on the basis of a negative CT.

• Diffusion weighted MRI is most sensitive for detecting acute infarction

• Hemorrhagic transformation can develop in the subacute stage (gradient echo MRI)

Insular Ribbon Sign

1st Day

2nd Day

Old CT

Recent CT

PICA Infarction

Dense basilar artery (arrow). Compare this to the normal internal carotid artery (arrowhead).

Cerebral Venous ThrombosisCerebral Venous Thrombosis

• Can involve the: dural sinuses, cortical veins or deep cerebral veins

Venous occlusionVenous occlusion

Spectrum of CT findings

• 10-30% of cases of CVT are negative on either unenhanced or

contrast-enhanced CT

• Highly suspicious cases should be furtherly evaluated with CT venography or MRI

• Unenhanced CT:

Direct signs of CVT “dense clot sign” seen only on 30% of cases.

Diffuse brain edema 20-50%

Venous infarction:

• Not conforming to a major arterial vascular territory, • Involving subcortical region • solitary or multiple isolated lesions • Hemorrhagic or non hemorrhagic.

• Unenhanced CT:

• Unenhanced CT:

Bilateral infarction at thalami, basal ganglia and internal capsules suggesting deep venous thrombosis

• Contrast-Enenhanced CT:

Direct evidence of CVT “Empty Delta Sign”

Indirect evidence of CVT may be seen as contrast enhancement of the adjacent dura or vascular engorgement

CT Venography: Allow direct visualization of

thrombus as filling defect

1st day

2nd day

Diagnostic Pitfalls

Pseudodelta sign

Normal variant of dense sinus

Unenhanced CT scans show subdural hemorrhage along falx and tentorium cerebelli, simulating sagittal and transverse sinus thrombosis.

Brain edemaBrain edema

• Cytotoxic: - Due to cellular swelling

- In the setting of cerebral ischemia

- Involves both gray and white matter

• Vasogenic: - Disruption of BBB and leakage of fluid

outside capillaries

- Associated with tumors and abscesses

- Involves only the white matter

Brain edemaBrain edema

Cytotoxic Vasogenic

Diffuse brain edemaDiffuse brain edema

• Causes include: ischemia and severe head injury

• High morbidity and mortality

• Effacement of the cortical sulci and basal cisterns

• Loss of gray/white matter interface

• White cerebellum sign

Cerebral herniationCerebral herniation

• Mechanical displacement of the brain secondary to mass effect

• Causes neurologic dysfunction and vascular compromise

• Types:

- Subfalcine

- Transtentorial (descending, ascending)

- Tonsillar

Cerebral herniationCerebral herniation

• Subfalcine herniation:

- The cingulate gyrus slips under the falx cerebri

- Compression of the ipsilateral ventricle and enlargement of the contralateral ventricle

- ACA ischemia

Cerebral herniationCerebral herniation

• Descending transtentorial herniation (uncal):

- The medial temporal lobe displaces through the tentorial notch

- Presents clinically with deteriorating level of consciousness, ipsilateral 3rd nerve palsy and contralateral motor deficit

- Effacement of the ipsilateral suprasellar cistern and enlargement of the ipsilateral CPA cistern

- The midbrain impacts the contralateral tentorium (Kernohan’s phenomenon, Duret hemorrhage)

- PCA ischemia

Cerebral herniationCerebral herniation