Editing Head injury (section)

====Extra-axial bleeding====
{{Epidural vs. subdural hematoma}}

Extra-axial hemorrhage, bleeding that occurs within the skull but outside of the brain tissue, falls into three subtypes:
* [[Epidural hemorrhage]] (extradural hemorrhage)  which occur between the [[dura mater]] (the outermost [[meninx]]) and the skull, is caused by trauma.  It may result from laceration of an artery, most commonly the [[middle meningeal artery]]. This is a very dangerous type of injury because the bleed is from a high-pressure system and deadly increases in [[intracranial pressure]] can result rapidly. However, it is the least common type of meningeal bleeding and is seen in 1% to 3% cases of head injury.
** Patients have a loss of consciousness (LOC), then a [[lucid interval]], then sudden deterioration (vomiting, restlessness, LOC)
** Head CT shows lenticular (convex) deformity.
* [[Subdural hemorrhage]] results from tearing of the bridging veins in the [[subdural space]] between the [[dura mater|dura]] and [[arachnoid mater]].
** Head CT shows crescent-shaped deformity
* [[Subarachnoid hemorrhage]], which occur between the arachnoid and [[pia mater|pia]] meningeal layers, like intraparenchymal hemorrhage, can result either from trauma or from ruptures of [[aneurysm]]s or [[arteriovenous malformation]]s.  Blood is seen layering into the brain along [[sulcus (neuroanatomy)|sulci]] and [[fissure (anatomy)|fissure]]s, or filling [[Cistern (neuroanatomy)|cistern]]s (most often the [[suprasellar cistern]] because of the presence of the [[blood vessel|vessel]]s of the [[circle of Willis]] and their branch points within that space). The classic presentation of subarachnoid hemorrhage is the sudden onset of a severe headache (a [[thunderclap headache]]). This can be a very dangerous entity and requires emergent neurosurgical evaluation and sometimes urgent intervention.