Background.—Idiopathic hypertrophic cranial pachymeningitis (IHCP) is an uncommon disorder due to localized or diffuse thickening of the dura mater. While headache is the most common manifestation, the clinical characteristics of the headache in IHCP have not been well characterized.
Methods.—From 1996 to 2002, 6 consecutive patients with IHCP presenting with headache were reviewed (3 women, 3 men; mean age: 49 years). Diagnosis was based on characteristic neuroimaging findings and the exclusion of secondary causes of cranial pachymeningitis. This study reported the headache characteristics, neuroimaging features, and longitudinal follow-up.
Results.—Chronic daily headache, especially chronic migraine, was the most common headache pattern observed (4/6 patients). Lateralization of headache location appeared to correlate with the distribution of the hypertrophied dural lesions. Diagnostic delay was due to failure to evaluate with gadolinium-enhanced MRI. After treatment, headache (5/6, 83%) and neurologic deficits (2/3, 67%) improved in most patients; however, follow-up MRIs (n = 5) showed deterioration in 3 patients.
Conclusion.—The headache of IHCP is typically a chronic daily headache, often resembling chronic migraine. Correspondingly, IHCP should be considered in the differential diagnosis of refractory chronic daily headache, with or without associated cranial neuropathy or other associated neurologic deficits. The typical imaging finding on gadolinium-enhanced MRI is localized or diffuse pachymeningitis and failure to order a gadolinium-enhanced MRI is the primary reason for delayed diagnosis. Despite symptomatic improvement on longitudinal follow-up, the MRI abnormalities may not improve in parallel with the clinical symptoms.