<unk> s are aneurysms of the brain vasculature which occur in small blood vessels (less than 300 micrometers diameter). They should not be confused with saccular aneurysms (a.k.a. berry aneurysms), which occur in larger-sized blood vessels.<unk> s are most often located in the brainstem. They are associated with chronic hypertension.
As with any aneurysm, once formed they have a tendency to expand and eventually rupture, in keeping with the Law of Laplace. If a<unk>  ruptures, it will lead to an intracerebral hemorrhage, which can cause hemorrhagic stroke, typically experienced as a sudden focal paralysis or loss of sensation. In contrast, if a saccular aneurysm ruptures, it will lead to a subarachnoid hemorrhage, typically experienced as an extremely severe headache leading to loss of consciousness. Both situations are medical emergencies, but a subarachnoid hemorrhage is more dangerous, with mortality between 25 and 50%.<unk> s are named for the French physicians Jean-Martin<unk>  and Charles-Joseph<unk> . It was<unk>  who discovered these aneurysms during his doctoral research under<unk> . These aneurysms do not exist, they are an artifact from the primitive staining techniques employed by<unk>  and<unk> . The vast majority of hemmorages into the brainstem and basal ganglia are caused by lipohyalinosis of perforating arterioles.<unk> s are a common cause of stroke. They are aneurysms in the small penetrating blood vessels of the brainstem and midbrain.They are associated with hypertension. The common artery involved is lenticulostriate branch of middle cerebral artery. Other causes of intracranial hemorrhage include:
Saccular aneurysm (aka berry aneurysm)
Ateriovenous malformations
Charcot-Bouchard aneurysm
Pseudoaneurysm
Mycotic aneurysm
Cerebral aneurysm
Carotid artery dissection
Intracranial berry aneurysm
Takayasu's arteritis
Monckeberg's arteriosclerosis