[Cerebral magnetic resonance imaging (MRI) in the diagnosis of leptomeningeal carcinomatosis in melanoma patients].

OBJECTIVE: Meningeal involvement is frequent in metastatic melanoma, approximately 30% in autopsy series. Functional signs may be misleading and the neurological examination may be normal. Certain diagnosis requires identification of tumor cells in the cerebrospinal fluid. CSF cytology is however sometimes negative and magnetic resonance imaging (MRI) with gadolinium injection may provide the diagnosis. The aim of this retrospective study was to assess the role of imaging in the diagnosis of leptomeningeal carcinomatosis.

PATIENTS AND METHODS: The diagnosis of leptomeningeal carcinomatosis was made in 8 patients between 1992 and 1998. All had signs of neurological function impairment, but the neurology examination was abnormal in only 2.

RESULTS: Cytology examination of the cerebrospinal fluid provided the diagnosis 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 these three cases, the brain CT did not provide any diagnostic element while the brain MRI with gadolinium injection confirmed the diagnosis of leptomeningeal carcinomatosis.

DISCUSSION: Forty-one percent of patients with autopsy proven leptomeningeal carcinomatosis have a normal ante mortem spinal tap. Brain MRI with gadolinium injection has better sensitivity than brain CT scan. All patients with nonspecific neurological signs and a normal spinal tap should be explored with a brain MRI.