Cranial pachymeningitis: a rare neurological syndrome with heterogeneous aetiology.

Cranial pachymeningitis is a poorly understood syndrome, defined by leptomeningeal thickening and typical gadolinium enhanced MRI. The heterogeneous clinical and aetiological features of five patients with both focal and diffuse pachymeningitis are presented. The initial symptoms included headache (n=3), sensory Jackson seizures (n=1), hemiparesis (n=1), episodes of short lasting hemiataxia (n=1), hemihypaesthesia (n=1), aphasia (n=1) and confusion (n=2). MRI scans revealed focal (n=3) or diffuse (n=2) leptomeningeal gadolinium enhancement and cortical swelling (n=4). In addition, one case presented with a subarachnoid and a second with an intracerebral haemorraghe. CSF findings were variable and showed clear lymphomonocytic pleocytosis in 3/5 cases. Infectious diseases were extensively excluded in all cases. Leptomeningeal biopsies of two cases revealed perivascular inflammation, indicating central nervous system vasculitis. In the cases presented, pachymeningitis was caused by primary central nervous system vasculitis (n=2) and rheumatoid arthritis (n=2). In one case, the cause remained unclear.