Idiopathic hypertrophic pachymeningeal lesions: correlation between clinical patterns and neuroimaging characteristics.

Nine patients with intracranial pachymeningeal thickening and enhancement on magnetic resonance imaging (MRI) completed a short-term clinical and MRI follow-up study. Based on clinical pictures, 4 of them were found to have spontaneous intracranial hypotension (SIH) and the remaining 5 had idiopathic intracranial pachymeningitis (IIP). Both groups were compared regarding their clinical and MRI characteristics. In 4 patients with SIH, gadolinium-enhanced T1-weighted images (WI) showed a diffuse and even enhancement of the entire intracranial and spinal dura mater. These thickened dura was slightly hyperintense on T2-WI. They had a favorable prognosis. In 2 patients with IIP, MRI demonstrated a relatively focal and even thickening and enhancement of the intracranial dura which was slightly hyperintense with a central hypointense area on T2-WI. These patients showed a very favorable course with or without steroid pulse therapy. In the remaining 3 patients with IIP, MRI depicted a focal, uneven enhancement of the intracranial dura which was relatively hypointense on T2-WI. Two of them with prolonged symptoms had a remitting and relapsing course, and 1 had a favorable outcome. In spite of current limitations in identifying the underlying causes of idiopathic pachymeningeal abnormalities, MRI can characterize the different patterns of pachymeningeal thickening. These findings may also correlate with the clinical picture and may be useful in predicting the response to treatment and prognosis.