Midline Shift on CT Brain — Key Radiological Features (Concise)
1. Septum Pellucidum Displacement (Most sensitive marker)
- Shift from midline (measured at level of foramen of Monro)
- Quantified in mm (clinically significant ≥5 mm)
2. Third Ventricle Shift
- Deviated from midline
- Often compressed or slit-like
3. Pineal Gland Displacement
- Normally midline → shift indicates deep central displacement
- Useful when calcified (acts as a marker)
4. Lateral Ventricle Asymmetry
- Ipsilateral ventricle: compressed
- Contralateral ventricle: dilated (± obstructive hydrocephalus)
5. Effacement of Sulci
- Loss of cortical sulci on affected side due to mass effect
6. Subfalcine Herniation (Cingulate Shift)
- Cingulate gyrus displaced under falx cerebri
- Often accompanies significant MLS
7. Basal Cistern Compression
- Indicates raised ICP and possible transtentorial progression
Measurement (Standard)
- Distance between:
- Ideal midline (line through falx)
- Actual septum pellucidum position
Clinical Correlation Thresholds
- <5 mm → mild
- 5–10 mm → moderate (often surgical consideration)
- >10 mm → severe, high risk of herniation
Quick Mnemonic
“3 S + V + H”
- Septum shift
- Sulcal effacement
- Side ventricle asymmetry
- Ventricle (3rd) deviation
- Herniation (subfalcine)
