Imaging characteristics of hypertrophic pachymeningitis due to ANCA-associated vasculitis.

OBJECTIVE

Hypertrophic pachymeningitis (HP) is a rare disorder that causes localized or diffuse inflammatory fibrosis and thickening of the dura mater. Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV)-related HP is the most frequent form of HP. Otitis media with AAV (OMAAV) patients with HP are associated with higher rates of both ANCA-negative phenotypes and disease-related mortality. However, few studies have reported the imaging characteristics of HP due to AAV/OMAAV. Therefore, we investigated this issue in the present study.

METHODS

This retrospective study included patients diagnosed with HP between 2011 and 2020 at our hospital. Age, sex, causative disease, serum C-reactive protein (CRP) level, and MRI data were collected from medical records. We compared the locations of MRI enhancement depending on the causative diseases.

RESULTS

Of the 18 included patients with HP (mean age, 64.1 ± 2.6 years; range, 33-77 years), 10 (55.6%) were female, 12 (66.7%) were diagnosed with AAV/OMAAV, four (22.2%) were diagnosed as idiopathic, two (11.1%) were diagnosed with invasive Aspergillus mastoiditis. Eleven (61.1%) had cranial neuropathies. Facial nerve paralysis was common in AAV/OMAAV, while abducent nerve paralysis was common in idiopathic HP. Cranial fossa enhancement was most common presentation in patients with HP, whereas inner acoustic canal (IAC) enhancement was seen only in patients with AAV/OMAAV, while HP involving the cavernous sinus was seen only in patients with idiopathic and mastoiditis.

CONCLUSION

HP involving the IAC may be a key factor in diagnosing AAV/OMAAV.