Imaging features of leptomeningeal metastases

AIM: To assess the range of appearances, and accuracy of various methods of diagnosing leptomeningeal metastases. MATERIALS AND METHODS: In a retrospective study, the notes and imaging of a ll patients with a radiological and/or CSF cytological diagnosis of leptome ningeal metastasis (LM) were identified, and assessed for the following: ag e and sex, primary tumour type, presenting symptoms, initial radiological a nd cytological diagnosis, radiological appearances and length of survival f ollowing diagnosis. Discordance between the CSF cytology and radiological d iagnosis of LM was also noted. RESULTS: 41 positive cases (36 female) of LM were identified over a 2.7 yea r period (diagnosis based on: imaging only - 19 cases, cytology only - 6, b oth - 16 cases). The average age was 48 years, and the most frequent primar y tumour was breast carcinoma (27/41). Two thirds of patients presented wit h at least one cranial or spinal nerve palsy. Where performed, contrast-enh anced CT was normal in 40% (10/25), with LM mistaken for parenchymal diseas e in a further 24% (6/25). CSF cytology was positive in 85% (22/26), Gadoli nium-enhanced CT was positive in all cases where it was performed (25/25). Pial enhancement and nodularity was the commonest finding (67%), but other manifestations included nodular disease, neural enhancement and white matte r changes. Prognosis was uniformly poor. CONCLUSION: Leptomeningeal metastatic disease has a poor prognosis, and tre atment regimen may differ from those of parenchymal CNS metastases. CT is n ormal or misleading in two thirds of patients, and CSF cytology may also be negative. Gadolinium-enhanced T1-weighted MRI complements CSF cytology, an d is the investigation of choice in patients with a non-haematological prim ary tumour and suspected LM. Collie, D. A., Brush, J. P., Lammie, G. A. et al. (1999) Clinical Radiology 54, 765-771. (C) 1999 The Royal College of Ra diologists.