Distinguishing magnetic resonance imaging features between idiopathic hypertrophic pachymeningitis and secondary hypertrophic pachymeningitis

Background: Hypertrophic pachymeningitis (HP) is a rare chronic inflammatory disorder characterized by marked fibrous thickening of the cerebral and/or spinal dura mater. This condition is caused by infection, inflammation, autoimmune disorder, neoplasms, or idiopathic. Magnetic resonance imaging (MRI) may play an important role in differentiating idiopathic HP from secondary HP, may avoid unnecessarily invasive dural biopsy, and prompt specific treatment. Objective: To determine the specific MRI findings for differentiation between idiopathic HP and secondary HP. Method: A total of 34 patients underwent MRI of the brain and cervical spine from January 2003 to December 2015. In all, 23 patients were diagnosed idiopathic HP and 11 patients were secondary HP. Demographic data and imaging findings reveal the following: configuration, thickness, signal intensity on T1-weighted image (T1WI), T2-weighted image (T2WI), and enhancement pattern of the lesions. The data were analyzed by T-test and Fisher's exact test. Result: Secondary HP were significantly located at anterior and middle cranial fossa (P = 0.033). There is no significant difference of lesions in configurations, T1 and T2 signal intensity and patterns of enhancement. There was significant and exclusive difference in T2 hypointense/dark intensity and homogeneous enhancement in idiopathic HP (75%, P = 0.044). Conclusions: MRI may play a complimentarily important role in distinguishing idiopathic HP from secondary HP. Idiopathic HP is probably preferred diagnosis in the lesions with T2-rim pattern and T2 hypointense/dark intensity with homogeneous enhancement.