Clinical, imaging features and treatment response of idiopathic hypertrophic pachymeningitis

Background: Idiopathic hypertrophic pachymeningitis (IHP) is a rare inflammatory disease that causes focal or diffuse thickening of the dura mater. However, longitudinal follow up studies are still lacking for these patients. Objective: To investigate the clinical characteristics, neuroimaging findings, treatment response and outcome of IHP. Method: A retrospective case series of 30 patients admitted Beijing Tiantan Hospital were screened via Hospital Information System from January 1st, 2011, to January 31st, 2021. All patients' clinical symptoms, imaging, and treatment response were collected via a standardized form. We compared the effects of high-dose and low-dose corticosteroids on headache, impaired vision, and MRI remission during acute onset. The effects of different immunosuppressants on preventing relapses were also compared. Results: Headache (93.3%) and multiple cranial neuropathy (66.7%) were the most common symptoms of IHP. Cerebral spinal fluid test showed that protein levels were elevated in 17 (56.7%) patients, and white blood cells were increased in seven patients. MRI demonstrated that diffuse (60%) and focal (40%) enhancement occurred in the dura mater, especially in the tentorium cerebellum (80%). High-dose and low-dose corticosteroids reduced headache and dural enhancement during the acute phase. The high dose corticosteroid significantly relieved the headache than the low dose group (p = 0.041). Patients treated with mycophenolate mofetil and cyclophosphamide might achieve longer remission (months, p = 0.428). Conclusion: Headache and multiple cranial neumpathy are the most common clinical manifestations of IHP. In this study, almost all patients had a good initial response to corticostemid therapy during the acute phase. Mycophenolate mofetil and cyclosporine may be effective for preventing relapses.