Insufficient Dural Thickness Recovery in Acute Treatment Predicts Subsequent Relapses in Idiopathic Hypertrophic Pachymeningitis.

Objective Idiopathic hypertrophic pachymeningitis (IHP) is an inflammatory disease of the dura mater of an unknown underlying cause. Although corticosteroids are commonly used as a first-line treatment, mixed responses have been observed. Furthermore, biomarkers for predicting relapse independent of various symptoms and lesion morphology have not yet been identified. We aimed to identify the prognostic factors of relapse in the first episode of IHP by objectively measuring the thickness of hypertrophic lesions of the dura mater. Methods In this retrospective observational study, we enrolled patients with IHP and classified their clinical course into two groups: monophasic and relapsing. We then compared the laboratory data and brain magnetic resonance imaging (MRI) findings between the groups. Patients Fourteen patients with IHP were included, and seven patients were classified into the monophasic and relapsing groups. Results The laboratory data and lesion distribution of the thickened dura on MRI were comparable between the two groups. The ratio of post-treatment to initial thickness (RTT) was significantly higher in the relapse group than in the monophasic group. Conclusion RTT after first-line treatment can be a potential predictor of relapse in IHP, thus providing valuable insight for the development of therapeutic strategies.