Invasion of the leptomeninges by tumour: the differential diagnosis from tuberculous meningitis.

Published accounts of tuberculous meningitis usually include intracranial tumour in the differential diagnosis. However, the two conditions are only likely to be confused when tuberculous meningitis is complicated by a tuberculoma or when there is diffuse infiltration of the subarachnoid space by malignant cells. As the latter causes an increase in both the cell and protein content of the cerebrospinal fluid, the resemblance to tuberculous meningitis may be striking (Russell, 1939) since signs and symptoms of raised intracranial pressure and of meningeal irritation, together with a wide variety of focal neurological signs, are common to both conditions. Diffuse infiltration of the leptomeninges by tumour is not excessively rare, as Polmeteer and Kernohan (1947) described 42 cases of meningeal gliomatosis while Fischer-Williams, Bosanquet, and Daniel (1955) referred to more than 50 cases of meningeal carcinomatosis. Such cases are likely to be referred to specialized neurological or neurosurgical centres, and during a period of two years, at a time when we were working with the Tuberculous Meningitis Unit of the United Oxford Hospitals, we encountered two cases of meningeal gliomatosis and two of meningeal carcinomatosis. To these we are permitted, through the courtesy of Mr. Wylie McKissock, to add a third case of meningeal carcinomatosis. In all five cases tuberculous meningitis was at some time suspected and it was only after intensive investigation, including contrast encephalography, cytological examination of the cerebrospinal fluid, and the bromide test, that the correct diagnosis was established in three before death. These cases are reported here because early and correct differentiation of the two conditions is of considerable importance: tuberculous meningitis is eminently treatable and radiotherapy may relieve symptoms in