A Rare Case of Hypertrophic Pachymeningitis after Surgery for Chronic Subdural Hemorrhage: A Case Report

Hypertrophic pachymeningitis (HP) is a rare type of inflammatory fibrosis characterized by diffuse thickening of the dura mater, which may cause a compressive effect or vascular compromise. Progressively worsening headache is the usual symptom, along with ataxia and various cranial nerve palsies. This article describes a rare case of HP after burr hole trephination for a chronic subdural hemorrhage (CSDH). A 64-year-old man was admitted to the emergency room with a headache that had started approximately 2 weeks prior. After the diagnosis of CSDH on imaging, burr hole trephination was performed. Six months later, the patient visited the hospital again with a headache. He was diagnosed with a recurrence of CSDH, and a craniotomy was performed. A solid subdural granuloma was suspected and a pathological examination revealed acute and chronic inflammation. Tissue biopsy and laboratory blood tests did not reveal any abnormalities. Three months later, he visited the hospital again with a severe headache. Magnetic resonance imaging showed no significant difference in the area of the previous operation; however, focal venous congestion and localized venous ischemic or inflammatory changes were observed in the tentorium. A craniotomy was performed for biopsy, and the dura mater was very thick. The pathology was diagnosed as HP. After taking steroids and immunosuppressive agents, the patient's symptoms improved. HP is a rare chronic inflammatory condition of the dura mater that causes neurological deficits. If the diagnosis is not definitively established based on an imaging examination, it should be made through a surgical biopsy. Steroid and immunosuppressive agents can improve the prognosis after diagnosis. Key words: Headache disorders; Hematoma, subdural, chronic; Hypertrophy; Immunosuppressive agents; Meningitis; Steroids