Is MRI as sensitive as cerebrospinal-fluid cytology for the diagnosis of neoplastic meningitis?

Background: Although CSF cytology and MRI are standard methods for the diagnosis of neoplastic meningitis (NM), this complication of malignancies still remains to be difficult to detect in some cases. We therefore re-evaluated the sensitivity of gadolinium(GD)-enhanced MRI and cerebrospinal-fluid (CSF)-cytology for the diagnosis of LM differenzially for solid and haematological malignancies and for normal or elevated cell counts.

Methods: We identified retrospectively 101 cases of NM diagnosed in our CSF laboratory since 1990 with complete data of both MRI and CSF-cytology. 34 had haematological, 67 solid neoplasms. CSF-cell counts were increased in 63 and normal in 35 patients.

Results: For haematological neoplasms, MRI was positive in 53%. CSF cytology was positive in 97%. In solid tumours, we found MRI-sensitivity of 0.81 and cytological sensitivity of 0.76. With normal CSF-cell-counts, MRI was positive in 63%, (0,57 haematological, 0,75 solid malignancies), CSF-cytology in 78%, (0,9 in haematological, 0,64 in solid neoplasms). In cases of increased cell-counts, MRI-sensitivity was 0.75 (0,52 for haematological, 0,87 for solid malignancies), and sensitivity of CSF-cytology was 0.89 (1,0 for haematological and 0,82 for solid neoplasms).

23 patients were treated with intrathecal MTX or Ara-C, 16 patients with liposomal Ara-C. 62 patients were not treated intrathecally.

Conclusions: We confirmed here the high overall sensitivity of MRI for the diagnosis of neoplastic meningitis. The best sensitivity, however, was seen in solid tumours and elevated cell counts. In haematological malignancies, a markedly lower sensitivity of MRI was seen. Of note, we consider the very high sensitivity of cytology in haematological malignancies to be artificial due to methodological reasons of this retrospective study. We conclude that MRI is a very sensitive method to detect NM especially in solid tumours and elevated cell counts. With normal cell counts and haematological neoplasms, CSF-cytology remains to be superior to radiological methods.