Extradural Haemorrhage:
Extradural haemorrhage is caused
almost exclusively due to trauma. At the moment of impact, the skull moves
relative to the dura beneath it and the dura is stripped from the bone. This
produces an empty extradural space at the site of trauma. A blood vessel may be
injured at the same time. The vessel injured depends upon the site of trauma.
1.
A blow over the lateral convexity of the head may
injure the middle meningel artery.
2.
A blow over forehead involves the anterior ethmoidal
artery.
3.
A blow over occiput or low behind the ear may tear the
transverse sigmoid sinus.
4.
A blow on the vertex may cause hge from sagittal sinus.
5.
Venous extradural hge accompanies fracture of the
skull.
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In 90% cases, the fracture is fissured type, but
sometimes depressed.
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The hematoma is directly under the site of
surface injury.
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Bellding from the main anterior branch of middle
meningeal artery covers the motor area of the brain & tends to run into the
middle fossa.
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The clot is sharply defined, passes the dura
inward & causes a localized concavity of the external surface of the brain.
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Causes of subdural haemorrhage:
- Rupture of parasagittal bridging or communicating veins.
- Rupture of inferior cerebral veins entering the sinuses at the base of skull.
- Rupture of dural venous sinuses.
- Injury to cortical veins.
- Lacerations or contusions of brain and dura.
- Laceration of the dura and middle meningial artery.
- Re-injury of old adhesion between the brain and the dura.
- Rupture of an aneurism or a superficial blood vessel malformation in the brain.
- Secondary to diseases e.g. cerebral tmour, cerebral aneurism or blood disorders.
- Drugs-Dicoumerol, warferin and heparin.
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Postmortem findings of subdural
haemorrhage:
·
Subdural haemorrhage is seen in some cases of
child abuse. It may occur if the child is violently shaken. In these cases
there may be no external marks of violence upon the child.
·
In old persons, chronic subdural haematoma mayo
be found at autopsy as an incidental finding, having being present for months
or even years with either no clinical signs or having caused neurological or
psychiatric symptoms which were wrongly attributed to a stroke or senile
dementia.
·
A fresh subdural haemorrhage is dark red in
colour, but after a few days begins to turn brown, with histological evidence
of haemosiderifl granules visible with Perl’s stain.
·
A gelatenous membrane forms around the
haematoma, which may harden into rubbery capsule in the chronic stages. From
above findings the ‘age’ of a subdural haematoma can be assessed.
