Inflammatory diseases of the blood vessels that are of infectious origin and their effects upon the nervous system are considered in detail in Chap. 31. There it was pointed out that meningovascular syphilis, tuberculous meningitis, fungal meningitis, and the subacute (untreated or partially treated) forms of bacterial meningitis may be accompanied by inflammatory changes in the walls of vessels that pass through the subarachnoid space and result in occlusion of the arteries or veins. For example, a small deep stroke is the first clinical sign of chronic basilar meningitis, but more often it develops well after the meningeal symptoms are established. The nature of the cerebral vasculitis that may rarely accompany HIV is unclear. Independent of this possible mechanism, an increasing incidence of stroke in patients with HIV has drawn considerable attention, for example, the epidemiologic survey by Ovbiagele and Nath has indicated a 60 percent increase in hospitalizations for stroke in HIV patients over a recent decade. However, the autopsy study carried out by Connor and coworkers emphasized that the causes of stroke were of the mundane types seen in others and, while some nondescript vasculopathy was seen in small vessels, this was not related to vasculitis.
Typhus, schistosomiasis, mucormycosis, aspergillosis, malaria, and trichinosis are infrequent causes of inflammatory arterial disease, which, unlike the above-mentioned infections, are not secondary to meningeal infections. In typhus and other rickettsial diseases, capillary and arteriolar changes and perivascular inflammatory cells are found in the brain; presumably they are responsible for the seizures, acute psychoses, cerebellar syndromes, and coma characterizing the neurologic disorder in these diseases. The internal carotid artery may be secondarily occluded in diabetic patients as part of the orbital and cavernous sinus infections with mucormycosis. In trichinosis, the cause of the cerebral symptoms has not been clearly established. Parasites have been found in the brain; in one of our patients the cerebral lesions were produced by bland emboli arising in the heart and related to a severe myocarditis. In cerebral malaria, convulsions, coma, and, sometimes, focal symptoms appear to be due to the blockage of capillaries and precapillaries by masses of parasitized red blood corpuscles. Schistosomiasis may invade cerebral or spinal arteries.
In a separate category is the embolic bacterial embolus to various sized vessels in the cerebrum that causes a focal, sometimes necrotizing, vasculitis from within the vessel. Infarction, local hemorrhage, and mycotic aneurysms may result. In the past, bacterial endocarditis was the main cause but other various causes of bacteremia now predominate. These diseases are discussed further in Chap. 31.
Noninfectious Inflammatory Diseases of Cranial Arteries
Included under this heading is a diverse group of arteritides that have little in common except their tendency to involve the cerebral vasculature in a multifocal manner. One group involves the larger caliber vessels and includes the giant cell arteritides—extracranial (temporal) arteritis; granulomatous arteritis of the brain; and aortic branch arteritis, one form of which is known as Takayasu disease. A special case is infiltration of the vessels by lymphoma cells; intravascular lymphoma, considered below.