Brain CT Recognition Pattern

Systematic approach to interpreting non-contrast head CT scans with key anatomical landmarks and emergency findings

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1. Basic Principles

A. Standard Windows

• Brain window:
  - WW 80, WL 40
  - Assess parenchyma, ventricles
• Bone window:
  - WW 2000, WL 500
  - Skull fractures, sinuses
• Subdural window:
  - WW 200, WL 80
  - Subtle extra-axial blood

B. Anatomical Planes

• Axial:
  - Standard viewing plane
  - From foramen magnum to vertex
• Coronal:
  - Pituitary fossa evaluation
  - Temporal lobes

2. ABCDEF Systematic Approach

Step

Assessment

Key Elements

A

Airways/Artifacts

Motion, beam hardening

B

Blood

Hemorrhage, SDH/EDH/SAH

C

Cisterns

Basal, Sylvian, quadrigeminal

D

Densities

Gray-white differentiation

E

Edges

Midline shift, herniation

F

Fractures/Fluid

Skull fractures, sinus fluid

3. Hemorrhage Patterns

A. Extra-axial Hemorrhage

Type

Location

Key Features

EDH

Dura vs skull

Biconvex, doesn't cross sutures

SDH

Dura vs arachnoid

Crescentic, crosses sutures

SAH

Subarachnoid space

Fills cisterns, sulci

B. Intra-axial Hemorrhage

• Intraparenchymal:
  - Hypertensive (basal ganglia)
  - Trauma (contusions)
  - Amyloid (lobar in elderly)
• Intraventricular:
  - Extension from parenchyma
  - Isolated (AVM, trauma)

4. Ischemia Patterns

A. Early Signs (<6 hours)

• Hyperdense artery sign:
  - MCA, basilar artery
• Insular ribbon sign:
  - Loss of gray-white in insula
• Sulcal effacement:
  - Early edema

B. Vascular Territories

Artery

Territory

ACA

Frontal lobes, medial surface

MCA

Lateral hemispheres

PCA

Occipital lobes

PICA

Posteroinferior cerebellum

5. Mass Effect & Herniation

A. Herniation Types

• Subfalcine:
  - ACA compression
  - Cingulate gyrus under falx
• Uncal:
  - CN III palsy
  - Temporal lobe through tentorium
• Tonsillar:
  - Cerebellar tonsils through FM
  - "Coning"

B. Measurements

• Midline shift:
  - Measure at septum pellucidum
  - ≥5mm significant
• Basal cisterns:
  - Effacement = ICP concern

6. Head CT Reporting Template

1. Technique: Non-contrast, slice thickness
2. Blood:
   - Presence/location of hemorrhage
   - Volume estimation
3. Parenchyma:
   - Gray-white differentiation
   - Hypodensities (territory)
4. Ventricles:
   - Size (Evans ratio)
   - Intraventricular blood
5. Cisterns:
   - Basal cistern patency
   - SAH presence
6. Bone:
   - Fractures (depressed)
   - Sinus opacification

Always correlate with clinical history and neurological exam. For trauma patients, review all images in both brain and bone windows. In stroke evaluation, assess ASPECTS score when appropriate. Document midline shift measurements and any herniation signs urgently. Follow up suspicious findings with MRI when indicated.

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