Midline shift (summary)

Changed by Daniel J Bell, 19 Jun 2017

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Midline shift is a finding described on transverse (axial) slices from CT and MRI studies. It describes the situation where the midline of the intracranial anatomy is no longer in the midline and is the result of pushing or pulling forces within either side of the intracranial compartment.

Reference article

This is a summary article; read more in our article on midline shift.

Summary

pathophysiology
- the midline is either pushed or pulled out of place
  - extra-axial collection causing mass effect
  - parenchymal tumour causing mass effect
  - stroke with associated oedema causing mass effect
investigation
- CT head
  - best initial test, especially in an unwell patient
- MRI brain

Radiographic features

CT

On an axial (transverse) slice from a CT scan, the midline structures should be in the midline:

falx cerebri
septum pellucidum
3rd ventricle
interpeduncular cistern
4th ventricle

If the midline structures are not in the midline, there may be pathology that is causing the shift - this is usually a collection, mass or oedema causing mass effect in one hemisphere.

In the supratentorial compartment, midline shift results in the cerebral parenchyma being forced under the static fibrous falx and can cause significant parenchymal injury.

Midline shift may cause obstruction of the foramen of ~~Munroe~~Monro and contralateral hydrocephalus.

~~-<li>falx</li>~~
+<li>falx cerebri</li>
-</ul>If the midline structures are not in the midline, there may be pathology that is causing the shift - this is usually a collection, mass or oedema causing mass effect in one hemisphere.In the supratentorial compartment, midline shift results in the cerebral parenchyma being forced under the static fibrous falx and can cause significant parenchymal injury.Midline shift may cause obstruction of the foramen of Munroe and contralateral hydrocephalus.
+</ul>If the midline structures are not in the midline, there may be pathology that is causing the shift - this is usually a collection, mass or oedema causing mass effect in one hemisphere.In the supratentorial compartment, midline shift results in the cerebral parenchyma being forced under the static fibrous falx and can cause significant parenchymal injury.Midline shift may cause obstruction of the foramen of Monro and contralateral hydrocephalus.