Basic 101 on CT Neuroimaging(from neurology point of view)

Dr Ahmad Shahir MawardiNeurology Department Hospital Kuala Lumpur25th May 2016

Content

• Basics of CT Neuroimaging • Neuro anatomy on CT• Common neurological conditions

Expectation(s)

• Able to – do on-call confidently– intreprete important CT findings

What not to expect(s)

• interprets CT scan like a 'pro'• pass medical examination with flying colours

The Eyes Don't See What the Mind Don't Know

CT scan Intrepretation (Abnormal)

1. Lesion(s) (hyperdense/Hypodense)2. Location3. Age of lesion (acute/subcute/chronic)4. + Cause, + complications

e.g• Acute infact at the left internal capsule• Acute communicating hydrocephalus

Pitfalls

• Pt name (make sure you have the right pt!)

• Age• Date• CT (brain)• Plane/View• Plain vs contrast• Findings

Part I

Basic of CT Neuroimaging

Basics of CT Neuroimaging

• Orientation• Region/Planes• Windows• Density• Slice thickness• Contrast enhancement

Basics of CT Neuroimaging: Orientation

Basics of CT Neuroimaging: Orientation

Basics of CT Neuroimaging: SYMMETRYMIRROR IMAGE

CT brain – 2 identical half

Basics of CT Neuroimaging: Planes

Basics of CT Neuroimaging: Planes

A

S

C

Basics of CT Neuroimaging: Window

Basics of CT Neuroimaging: Density

• Hypodense• Hyperdense• Isodense

Basics of CT Neuroimaging: Density

HYPERDENSITIES

Most common:•Blood•Calcification•Exception to the rule:

– Pineal gland– Choroid plexus

Left temporal epidural haematoma

HYPODENSITY

Most common:

•Infarction•Fluid

– edema, infection, tumour

•Hydrocephalus•Air

Basics of CT Neuroimaging: Density

The Density of Blood Changes with Time!

Basics of CT Neuroimaging: slice thickness

• Scanogram– Plane used for

scanning– Anatomic extent of

series of scans

• Slice thickness may vary (5-10 mm)

CT brain: Contract vs non-contrast

• Contrast:– Vascular lesion– Tumor– Sites of infection

• CTA (stenosis)• CTV (CVT)• Leptomenigeal

enhancement (meningitis)

• Ring enhancing lesion

Ring enhancing lesion

• Tumour – Primary (GBM, lymphoma) – Metastasis

• Infections:– Abscess– HIV associated:

toxoplasma, crytococcus– TB/ tuberculoma– Neurocysticercosis

• Resolving hematoma (10-21 days)

• Radiation necrosis• Postoperative change• Aneurysm • Multiple sclerosis/ADEM (MRI)

Ring enhancing lesion

Part II

NeuroAnatomy

Identification of structures

Lateral View of Brain

Ventricular System

Cross-sectional Anatomy

• Grey/White interface, Subcortical white matter

Cross-sectional Anatomy

• Paired of crescent-shape = Twin bananas

Cross-sectional Anatomy

Basal ganglia

Cross-sectional Anatomy

• Third ventricle, Basal ganglia, Superior cerebellar cistern

Physiologic Calcification

Brain Anatomy

Cross-sectional Anatomy

• Third ventricle, Smiley face

Cross-sectional Anatomy

• Midbrain, Interpeduncular cistern

Cross-sectional Anatomy

• Star shape ~ Circle of Willis, • Fourth ventricle, Temporal horn ~ slit

Cross-sectional Anatomy

• Base of skull, Midline bony prominence, • Prepontine cistern, Pretrous bone, Frontal sinus

Cross-sectional Anatomy

• Orbits, Ethmoid air cell

Part III

Common neuropathological findings

Common neuropathological findings

• Stroke• Haemorrhage• Hydrocephalus• Leptomeningeal enhancement• CNS infections

Ischemic stroke

• Location:– Cortical infarction– Lacunar infarction– Watershed / Borderzone infarction

• Timing:– Hyperacute changes– Early changes– Established changes

• Complications:– Haemorrhagic transformation– Cerebral oedema

Cortical signs

• Aphasia• Neglect (may be spatial, sensory, visual, auditory)• Alteration of consciousness• Visual field cut

Stroke: Cortical Infarction

• Follows vascular territory– ACA– MCA– PCA– Mixed

• Wedge shape• May have complications

– Haemorrhagic transformation

– Cerebral oedema

• Usually embolic aetiology

Lacunar Infarction

• Sites (BITCP)– Basal Ganglia (Caudate, Putamen)– Internal capsule– Thalamus– Pons– Cerebellum

• 3-15 mm in diameter• Distal distribution of penetrating arteries

– Lenticulostriate– Thalamoperforators– Pontine perforators– Recurrent artery of Heubner

• Fibrinoid degeneration

Penetrating arteries/ perforators

Lacunar Infarction

Lacunar Infarction

Borderzone Infarction

• Cortical Borderzone

• Internal Borderzone

• Pathology / Occlusion of proximal vessels – ICA

Hyperacute changes

• Dense MCA sign• Dot sign• Loss of gray-white

differentiation• Loss of sulcation• NORMAL

• As early as 2-6 hours from onset

6 hours 24 hours 40 hours

ASPECTS score

What ASPECTS tell us

• Functional Outcome• Risk of bleeding

Intracerebral Haemorhage

• Typical hypertensive sites:– Lenticulostriate vessels

• Basal Ganglia (Caudate, Putamen)• Internal capsule• Thalamus (a/w intravent. Ext)• Pons• Cerebellum

– Complications:• Mass effect• Obstructive hydrocephalus

Intracerebral Haemorrhage• Atypical sites!!!:

– Cerebral Amyloid Angiopathy• 15% of ICH in pts > 60 yrs old

– AVMs• Intracerebral haemorrhage or SAH

• Ix: CTA

Venous Infarction

• Thrombosis of cerebral veins– Evidence of thrombosis – Dense cord sign,

Delta / Empty delta sign– Complications of CVT – SAH, Atypical infarcts.

Haemorrhage

Haemorrhage

Epidural Haematoma

• Biconvex• restricted by dural tethering at

the cranial sutures

Subdural Haematoma

• Crescent-shaped 

• They do not cross the midline because of the meningeal reflections

Subarachnoid haemorrhage

Subarachnoid haemorrhage

Hydrocephalus

Ventriculomegaly a/w raised ICP

•Communicating/Non-obstructive:– Impaired reabsorption of CSF fulid in the absence of any CSF flow

obstruction

•Non-Communicating/Obstructive:– CSF-flow obstruction

• Foramen of Monro• Aqueduct of Sylvius• Fourth Ventricle obstruction

Hydrocephalus

• Acute - “Ballooned” ventricles with periventricular low density “ halo”- 3rd ventricle - rounded

• Chronic – “Ballooned” ventricles without periventricular halo- 3rd ventricle – normal app

• Obstructive:– Basal cisterns, sulci compressed /

obliterated

Hydrocephalus Hydrocephalus ex-vacuo

Tuberculous Meningitis

1.Meningeal enhancement:

2. Infarction (20.5 – 30.8%):- thalamus, basal ganglia, internal capsule

3. Hydrocephalus

4. Tuberculomas -Infrequently seen except in miliary TB

5. Vascular changes-uniform narrowing of large segments -small segmental narrowing -irregular beaded appearance -complete occlusion.

Postgrad Med J 1999;75:133 140 doi:10.1136/pgmj.75.881.133

TB Meningitis: Tuberculomas

Contrast-enhanced CT•showing multiple tuberculomas in a patient with tuberculous meningitis

Postgrad Med J 1999;75:133 140 doi:10.1136/pgmj.75.881.133

Meningioma

Right Temporal Glioblastoma

High grade glioma – usually Glioblastoma

Brain Abscess

Herpes Encephalitis

• Predilection for limbic system:– Temporal lobes– Insular cortex– sub frontal area– cingulate gyri.

• Initially unilateral --> "sequential bilaterality" is highly suggestive of HSE1.

Toxoplasmosis Primary CNS Lymphoma

Thank You

Hydrocephalous

Subarachnoid hemorrhage