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Duret haemorrhage

Duret haemorrhage (also spelled, Duret hemorrhages) are small areas of bleeding in the ventral and paramedian parts of the upper brainstem, (midbrain and pons). They are secondary to raised intracranial pressure with formation of a transtentorial pressure cone involving the cerebral peduncles [crus cerebri] and other midbrain structures caused by raised pressure above the tentorium. Kernohan’s notch is a groove in the cerebral peduncle caused by this displacement of the brainstem against the incisura of the tentorium ~~in some cases~~. The resulting ipsilateral hemiparesis is a false localising sign (Collier 1904), known as the Kernohan-Woltman syndrome. This may succeed or accompany temporal lobe (uncal) herniation and subfalcian herniation secondary to a supratentorial mass.

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Causes

The common causes are an acute haematoma, oedema following trauma, abscess, or tumour. The Duret haemorrhage is demonstrated at CT or MRI. It usually indicates a fatal outcome. The mechanism is uncertain but is probably caused by the displacement of the brainstem stretching and lacerating pontine perforating branches of the basilar artery; venous infarction may play a role.

Sources

Collier, J. The false localizing signs of intracranial tumour. Brain 27:490-508, 1904.
J. W. Kernohan JW, Woltman HW. Incisura of the crus due to contralateral brain tumor. Archives of Neurology and Psychiatry, Chicago, 1929, 21: 274–287.
Fisher, C.M. Brain herniation: a revision of classical concepts. Can J Neurol Sci. 1995, 22(2):83-91