|In tuberculous meningitis there is a thick, gelatinous exudate around the sylvian fissures, basal cisterns, brainstem, and cerebellum. Hydrocephalus may occur as a consequence of obstruction of the basal cisterns, outflow of the fourth ventricle, or occlusion of the cerebral aqueduct. Hydrocephalus frequently develops in children and is associated with a poor prognosis. The basal exudates of tuberculosis are usually more severe in the vicinity of the circle of Willis, and produce a vasculitis-like syndrome. Cerebral infarctions are most common around the sylvian fissure and in the basal ganglion. Hemorrhagic transformation of infarcted tissue is not unusual.The most serious consequence of TBM, however, is the development of vasculitis in the vessels of the circle of Willis, the vertebrobasilar system, and the perforating branches of the middle cerebral artery, resulting in infarctions in the distribution of these vessels. Direct contact of the exudate with the brain surface causes a border zone reaction that damages the underlying brain tissue.