INTRODUCTION TO CT HEAD

FOR THE ADVANCED

PRACTICE PROVIDER

Ervin Lowther, MDMedical Director of Neuroradiology

Prisma Health - Upstate

Obligatory Picture #1

Obligatory Picture #2

Can’t miss 4 H’s on a head CT

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Name 3 CT Signs of Early Infarction

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4 Types Intracranial Hemorrhage

Outline

• CT concepts

– Density

• Concepts in brain imaging

– Gray-white differentiation

– Types of cerebral edema

– Sulci

CT

FDA Website, 6/28/13

Sir Walter Hounsfield

1972

CT Attenuation

– Density of tissue Gray scale

• air black

• fat darker gray

• CSF gray

• brain lighter gray

• acute blood, contrast white

• bone very white

CT HU In The Brain

• HU of grey matter (GM) and (WM)

– GM ~ 40

– WM ~ 30

• HU of hemorrhage

– Hyperacute ~ Hct

– Acute ~60-80

– Subacute ~ 40

– Chronic ~ 0-20

Relevant CT Anatomy

Important CT concepts in

Brain Imaging

• Attenuation

• Gray-white differentiation• Types of cerebral edema

– Determine stroke versus stroke mimic

• Sulci

Grey-White Differentiation

Types of Cerebral Edema

Cytotoxic• Brain cells die

• Influx of water into GM

• Lose GM-WM

differentiation

Vasogenic• Something irritates the

brain

• Influx of water in WM

• Accentuates GM-WM

differentiation

GM is the key!

Types of Cerebral Edema

Cytotoxic Vasogenic

WM Edema

Edema

WM

GM WM

WM

Edema

WM

Causes of Cerebral Edema

Cytotoxic

• Anything that causes the

cells to die

• Infarcts/Ischemia

• Necrotizing infection

Vasogenic

• Anything that disrupts the

blood brain barrier

• Neoplasm

• Infection

• Tumefactive demyelination

Stroke

• Death of brain cells due to lack of oxygen– Caused by blockage of blood flow or rupture of a blood

vessel

• Stroke is a clinical diagnosis

• We see infarcts on imaging

CT Signs of Infarction

• 3 early signs of infarction

– Loss of grey-white matter differentiation

• Loss of insular ribbon

– Sulcal effacement

– Hyperdense vessel sign

Baseline CT < 3 hrs

Case

Day 3 CT s/p t-PA

Case

Identify Vascular Territory

• Must identify vascular distribution

– Middle cerebral artery (MCA)

– Posterior cerebral artery (PCA)

– Anterior cerebral artery (ACA)

– Basilar artery (BA)

– Cerebellar arteries

• Superior cerebellar artery (SCA)

• Anterior inferior cerebellar artery (AICA)

• Posterior inferior cerebellar artery (PICA)

Vascular Territories

http://rad.desk.nl/en/p484b8328cb6b2

Bilateral ACA Infarcts And Cerebral

Edema

Day 3 CT s/p TPA

MCA infarct with hemorrhage

diffuse anoxic injury

How ‘bout this one?

Can’t Miss 4 H’s

• Hemorrhage

• Hydrocephalus

• Herpes

• Herniation

Intracranial Hemorrhage

• Intraparenchymal

• Subarachnoid

• Subdural

• Epidural

• Intraventricular

Hypertensive Hemorrhage

• Most common sites– Basal ganglia

• Most common site

– Thalamus

– Brainstem (pons)

– Cerebellum

HTN Bleed

Subarachnoid Hemorrhage

• Within the subarachnoid spaces

– Cisterns

– Fissures

– Sulci

• Most common cause of SAH?

– Trauma

Acute SAH

Subdural Hemorrhage

• Between the dura and arachnoid

• Crescentic

• Can cross suture lines– Cannot cross the midline

• Superior sagittal sinus

• Not necessarily associated with a frx– But you’d better still look

Subdural Hemorrhage

What about this one?

Epidural Hemorrhage

• Between the skull and dura

• Lenticular

• Does not cross the sutures– Dura is tightly adherent at sutures

• Highly associated with a fracture

HEMORRHAGE

IPH SAH SDH EDH

Gratuitous Picture

Which One of the 4 H’s?

Hydrocephalus

• Enlargement of the ventricles due to

alteration of CSF flow

• Communicating or non-communicating

(obstructive)

• Look for enlargement of the temporal horns

and rounding of the third ventricle!

Hydrocephalus on MRI

Gratuitous Picture

Infarct or One of the 4 H’s?

Vascular Territories

http://rad.desk.nl/en/p484b8328cb6b2

Infarct or One of the 4 H’s?

Infarct or One of the 4 H’s?

Herpes encephalitis

Herpes Encephalitis

• HSV causes necrotizing encephalitis

– Usu HSV-1

• Limbic system

– Temporal lobes, insula, hippocampus,

subfrontal area, cingulate gyrus

• Can be symmetric or asymmetric

• Can be hemorrhagic

– Necrotizing hemorrhagic encephalitis

Herniation

• Many different types but most commonly

– Uncal

– Subfalcine

– Tonsillar

– Transtentorial

1. Inferior displacement of

sylvian fissure

2. Subfalcine herniation

3. Entrapment of lateral ventricle

4. Compression of ACA

5. Midbrain contusion

6. Duret (midbrain) hemorrhage

7. Descending transtentorial

herniation

8. Compression of PCA

9. Widening of ipsilateral CPA

10. Descending tonsillar

herniation

CEREBRAL HERNIATIONS

Uncal Herniation Subfalcine Herniation

Wrap It Up!

HEMORRHAGE

IPH SAH SDH EDH

Can’t Miss 4 H’s

• Hemorrhage

• Hydrocephalus

• Herpes

• Herniation

Name 3 CT Signs of Early Infarction

• Loss of gray-white differentiation

• Sulcal effacement

• Hyperdense vessel sign

Take Home Points

• Stroke remains a clinical diagnosis

• Best initial test = noncontrast head CT

• GM is the key to differentiating types of edema

Take Home Points

• Look at insular ribbon for early MCA

infarcts

• Look at temporal horns for early hydro

• Check the interpeduncular fossa for SAH