To describe imaging characteristics in diagnosing chronic meningitis secondary to malignancy

Chronic meningitis is an uncommon neurological disorder wherein an etiology is often difficult to delineate. This can be divided into three main etiologies: neoplastic, infectious, and autoimmune (in addition to idiopathic). These include primary CNS malignancies as well as metastatic disease, most often from breast, lung, and hematologic primaries. It has not previously been studied what the typical imaging pattern of neoplastic chronic meningitis is, or how much this depends on the primary malignancy.

Cases were identified through retrospective review from our electronic medical record from 2004-2018, and were identified by having either two consecutive lumbar punctures with > 5 WBC/mL3 over 4 weeks, or by having 4 weeks of meningismus and one lumbar puncture with > 5 WBC/mL3. Patients were then selected with neoplasm as etiology. The study was approved by the institutional review board.

34 patients were identified with chronic neoplastic meningitis. Of these patients, 61.3% had MRI abnormalities, either meningeal enhancement (45.0%) or a mass lesion (51.6%). In patients with meningeal involvement, leptomeningeal enhancement was more common than pachymeningeal enhancement (71.4% vs 35.7%), except in lymphoma (60% pachymeningeal). When mass lesions were present, they were primarily in brain parenchyma (93.8%) rather than in bone (6.3%). The most common etiologies were lymphoma (16), followed by breast (8) and lung (6).

In our cohort of patients, imaging was more likely to reveal a mass lesion in the CNS than it was to show meningeal enhancement. Magnetic resonance imaging was not highly sensitive but it does compare favorably to reported sensitivity for lumbar puncture given the need for repeat large volume taps to achieve high sensitivity. Pachymeningeal enhancement is less common but when present is suggestive of lymphomatous source.