Teaching NeuroImages: Idiopathic hypertrophic spinal pachymeningitis mimicking epidural lymphoma.

A 41-year-old man presented with bilateral leg numbness and paraparesis for 3 months. MRI showed a circumferential long epidural mass extending from T2 to T4 level (figure 1). Histologic examination demonstrated dense fibrous tissue with inflammatory infiltrate (figure 2). By exclusion of trauma, infectious diseases, and autoimmune diseases, idiopathic hypertrophic spinal pachymeningitis (IHSP) was diagnosed. IHSP is a rare inflammatory disease characterized by hypertrophic inflammation of the dura mater. The typical MRI finding of IHSP is a long epidural mass of low T2 signal intensity with peripheral enhancement. Homogeneous enhancement is typical of and could be mistaken for epidural lymphoma.