The nervous system is affected in approximately 30 percent of patients with Behçet disease (Chajek and Fainaru); the manifestations are recurrent meningoencephalitis, cranial nerve (particularly abducens) palsies, cerebellar ataxia, corticospinal tract signs, and venous occlusion disease. There may be episodes of diencephalic and brainstem dysfunction resembling minor strokes. A few postmortem examinations have related these small foci of necrosis to a vasculitis, including perivascular and meningeal infiltration of lymphocytes. There may also be cerebral venous thrombosis. The neurologic symptoms usually have an abrupt onset and are accompanied by a brisk spinal fluid pleocytosis (lymphocytes or neutrophils may predominate), along with elevated protein but normal glucose values (in one of our patients, 3,000 neutrophils per cubic millimeter were found at the onset of an acute meningitis). As a rule, neurologic symptoms clear completely in several weeks, but they have a tendency to recur, and some patients are left with persistent neurologic deficits. Rarely, the clinical picture is that of a progressive confusional state or dementia (see the reviews of Alema and of Lehner and Barnes for detailed accounts).
The cause of Behçet disease is unknown. A pathergy skin test—the formation of a sterile pustule at the site of a needle prick—is listed as an important diagnostic test by the International Study Group, but on the basis of admittedly limited U.S. experience, we and our colleagues have found it to be of questionable value. Administration of corticosteroids has been the usual treatment, on the assumption of an autoimmune etiology. Because the episodes of disease naturally subside and recur, evaluation of treatment is difficult.
Thrombosis of the cerebral venous sinuses, particularly of the superior sagittal or lateral sinus and the tributary cortical and deep veins, gives rise to a number of important neurologic syndromes. Cerebral vein thrombosis may develop in relation to infections of the adjacent ear and paranasal sinuses or to bacterial meningitis, as described in Chap. 31. More common is noninfectious venous occlusion resulting from one of the many hypercoagulable states discussed below.
Occlusion of cortical veins that are the tributaries of the dural sinuses takes the form of a venous infarctive stroke. It may be difficult to determine if the thrombus originated in the dural sinuses and propagates to the tributary cortical veins, or the reverse. The diagnosis is difficult except in certain clinical settings known to favor the occurrence of venous thrombosis, such as the taking of birth control pills or postpartum and postoperative states, which are often characterized by thrombocytosis and hyperfibrinogenemia. Hypercoagulable conditions also occur in cancer (particularly of the pancreas and colon and other adenocarcinomas), cyanotic congenital heart disease; cachexia in infants; sickle cell disease; antiphospholipid antibody syndrome, the aforementioned Behçet disease, factor V Leiden mutation, protein S or C deficiency, antithrombin III deficiency, resistance to activated protein C; primary or secondary polycythemia and thrombocythemia; and paroxysmal nocturnal hemoglobinuria.
The administration of drugs such as tamoxifen, bevacizumab, and erythropoietin, and even the hypercoagulable reaction to heparin that is associated with thrombocytopenia have all been cited as risks for cerebral venous thrombosis.