Fig. 23.7 Cerebralinfarction.(A)Sectionofthebrainshowingalarge,discolored,focallyhemorrhagicregionintheleftmiddlecerebralarterydistribution(hemorrhagic,orred,infarction).(B)Aninfarctwithpunctatehemorrhages,consistentwithischemia-reperfusioninjury,ispresentinthetemporallobe.(C)Oldcysticinfarctshowsdestructionofcortexandsur-roundinggliosis.
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Fig. 23.8 Cerebralhemorrhage.Massivehypertensivehemorrhagerupturingintoalateralventricle.
MORPHOLOGYInacuteintracerebralhemorrhage,theextravasatedbloodcompressestheadjacentparenchyma.Withtime,hemorrhagesareconvertedtoacavitywithabrown,discoloredrim.Onmicroscopicexamination,earlylesionsconsistofclottedbloodsurroundedbyedematousbraintissuecontainingneuronsandgliadisplayingmorphologicchangestypicalofanoxicinjury.Eventuallytheedemaresolves,pigment-andlipid-ladenmacrophagesappear,andproliferationofreactiveastrocytesbecomesvisibleattheperipheryofthelesion.Thecellulareventsthenfollowthesametimecourseobservedaftercerebralinfarction.
Cerebral amyloid angiopathy (CAA) is a disease in which the same amyloidogenic peptides as those found in Alzheimer disease (discussed later) deposit in the walls of medium-and small-caliber meningeal and cortical vessels. The amyloid confers a rigid, pipe-like appearance and stains with Congo red. Amyloid deposition weakens vessel walls and increases the risk for hemorrhages, which differ in distribution from those associated with hypertension. CAA-associated hemorrhages often occur in the lobes of the cerebral cortex (lobar hemorrhages). In addition to these symptomatic hemorrhages, CAA also results in small (<1 mm) cortical hemorrhages (microhemorrhages).
The most frequent cause of clinically significant nontraumatic subarachnoid hemorrhage is rupture of a saccular (berry) aneurysm. Hemorrhage into the subarachnoid space also may result from vascular malformation, trauma, rupture of an intracerebral hemorrhage into the ventricular system, coagulopathies, and tumors.
In about one-third of cases, rupture of a saccular aneurysm occurs at the time of an acute increase in intra-cranial pressure, such as occurs with straining at stool or sexual orgasm. Blood under arterial pressure is forced into the subarachnoid space, and the patient is stricken with sudden, excruciating headache (known as a thunderclap headache, often described as “the worst headache I’ve ever had”) and rapidly loses consciousness. Between 25% and 50% of affected individuals die from the first bleed, and recurrent bleeds are common in survivors. Not surprisingly, the prognosis worsens with each bleeding episode.
About 90% of saccular aneurysms occur in the anterior circulation near major arterial branch points (
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