Cryptococcosis of the central nervous system

(1) A survey of cryptococcal infections of the nervous system in Queensland, Australia, revealed the nine year prevalence rate for the Australian aboriginal to be some 17 times greater than that of the white population. Uncommon in the first decade of life, the disease was developed by 79% of 29 patients between 20 and 59 years, males being affected twice as commonly as females. (2) Cryptococcosis appears to be more common in Australia than in the United Kingdom, and in Queensland the nine year incidence of neurological cryptococcosis was 4·7 per 100,000 in the tropical north compared with 1·8 per 100,000 in the southern parts of the State. Because of this, and since 20 of the 29 patients were regarded as having outdoor occupations, it is suggested that a high environmental exposure to the fungus may be associated with an animal reservoir and with dry, dusty conditions. It is also possible that geographical and occupational factors rather than racial predisposition account for the high incidence of the disease in the Australian aborigine. However, individual resistance and susceptibility are probably also important factors, since the clinical disease appears to be positively correlated with certain other diseases, or with steroid therapy, which would impair the immune responses of the body. (3) Headache is the outstanding symptom of neurological cryptococcosis and fever or evidence of meningeal reaction, though often present, may be absent. An awareness of the possibility of neurological cryptococcosis in the differential diagnosis of various intracranial disorders should lead to identification of the encapsulated C. neoformans in the cerebrospinal fluid. Although in eight of 26 patients the lumbar cerebrospinal fluid was sterile on repeated examination, in five cases C. neoformans was found on direct examination of cerebrospinal fluid obtained by ventricular puncture. The remaining three died before further investigations could be performed. (4) Before the introduction of amphotericin B, neurological cryptococcosis was almost invariably fatal. At the present time, the infection can be eradicated in some 80% of patients. Intravenous administration of amphotericin B is generally adequate, but the intrathecal route should be used for cases in relapse or in critically ill patients. In addition to the toxic effects of the drug, the possibility of later deterioration in the patient's condition due to meningeal reaction—for example, occult hydrocephalus—merits consideration and appropriate neurosurgical treatment.