CNS magnetic resonance imaging in the diagnosis of leptomeningeal carcinomatosis in melanoma patients.

Objective. Meningeal involvement is frequent in metastatic melanoma, approx imately 30% in autopsy series. Functional signs may be misleading and the n eurological examination may be normal. Certain diagnosis requires identific ation of tumor cells in the cerebrospinal fluid. CSF cytology is however so metimes negative and magnetic resonance imaging (MRI) with gadolinium injec tion may provide the diagnosis. The aim of this retrospective study was to assess the role of imaging in the diagnosis of leptomeningeal carcinomatosi s. Patients and methods. The diagnosis of leptomeningeal carcinomatosis was ma de in 8 patients between 1992 and 1998. All had signs of neurological funct ion impairment, but the neurology examination was abnormal in only 2. Results. Cytology examination of the cerebrospinal fluid provided the diagn osis of leptomeningeal carcinomatosis in 5 patients. One out of 5 brain CT scans were positive, showing meningeal enhancement confirmed by brain MRI. The spinal tap was not contributive in 2 cases and was not done in 1. In th ese three cases, the brain CT did not provide any diagnostic element while the brain MRI with gadolinium injection confirmed the diagnosis of leptomen ingeal carcinomatosis. Discussion. Forty-one percent of patients with autopsy proven leptomeningea l carcinomatosis have a normal ante mortem spinal tap. Brain MRI with gadol inium injection has better sensitivity than brain CT scan. All patients wit h nonspecific neurological signs and a normal spinal tap should be explored with a brain MRI.