Inflammatory processes involving blood vessels may compromise blood flow and cause cerebral dysfunction or infarction. Infectious arteritis of small and large vessels was previously seen mainly in association with syphilis and tuberculosis, but is now more often caused by opportunistic infections (such as aspergillosis, herpes zoster, or CMV) in the setting of immunosuppression. Some systemic forms of vasculitis, such as polyarteritis nodosa, may involve cerebral vessels and cause single or multiple infarcts. Primary angiitis of the CNS is a form of vasculitis that involves multiple small-to medium-sized parenchymal and subarachnoid vessels and is characterized by chronic inflammation, multinucleate giant cells (with or without granuloma formation), and destruction of vessel walls. Affected individuals present with a diffuse encephalopathy, often with cognitive dysfunction. Treatment consists of immunosuppressive agents.
Stroke istheclinicaltermforacute-onsetneurologicdeficitsresultingfromhemorrhagicorobstructivevascularlesions.
Cerebralinfarctionfollowslossofbloodsupplyandcanbewidespreadorfocal,oraffectregionswiththeleastrobustvascularsupply(“watershed”infarcts).
Focalcerebralinfarctsaremostcommonlyembolic;withsubsequentdissolutionoftheembolusandreperfusion,anonhemorrhagicinfarctcanbecomehemorrhagic.
Primaryintraparenchymalhemorrhagestypicallyareduetoeitherhypertension(mostcommonlyinwhitematter,deepgraymatter,orposteriorfossacontents)orcerebralamyloidangiopathy(cerebralcortex).
Spontaneoussubarachnoidhemorrhageusuallyiscausedbyastructuralvascularabnormality,suchasananeurysmorarteriovenousmalformation.
Trauma to the brain and spinal cord is a significant cause of death and disability. The severity and site of injury affect the outcome: injury of several cubic centimeters of brain parenchyma may be clinically silent (if in the frontal lobe), severely disabling (affecting the spinal cord), or fatal (involving the brain stem).
A blow to the head may be penetrating or blunt; it may cause an open or a closed injury. The magnitude and distribution of resulting traumatic brain lesions depend on the shape of the object causing the trauma, the force of impact, and whether the head is in motion at the time of injury. Severe brain damage can occur in the absence of external signs of head injury, and conversely, severe lacerations and even skull fractures do not necessarily indicate damage to the underlying brain. When the brain is damaged, the injuries may involve the parenchyma, the vasculature, or both.
When an object impacts the head, brain injury may occur at the site of impact—a coup injury—or opposite the site of impact on the other side of the brain—a contrecoup injury. Both coup and contrecoup lesions are contusions, with comparable gross and microscopic appearances. A contusion is caused by rapid tissue displacement, disruption of vascular channels, and subsequent hemorrhage, tissue injury, and edema. Since they are closest to the skull, the crests of the gyri are the parts of the brain that are most susceptible to traumatic injury. Contusions are common in regions of the brain overlying rough and irregular inner skull surfaces, such as the orbitofrontal regions and the temporal lobe tips. Penetration of the brain by a projectile such as a bullet or a skull fragment from a fracture causes a laceration, with tissue tearing, vascular disruption, and hemorrhage.
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MORPHOLOGYContusionsarewedge-shaped,withthewidestaspectclosesttothepointofimpact(