Clinico-radiological spectrum and outcome in idiopathic hypertrophic pachymeningitis.

Objective: To elucidate the clinico-radiological features, treatment response and outcome of a large cohort of patients (n=20) with idiopathic hypertrophic pachymeningitis (IHP) and to examine if any of these features could differentiate between IHP and secondary causes of hypertrophic pachymeningitis (SHP).

Methods: 20 patients with IHP diagnosed between 1998 and 2009 formed the study cohort. We adopted a validated clinical score to quantitatively assess and document their neurological disability and to compare their pre- and post-treatment outcomes. Appropriate statistical analysis was done to look for any clinical and/or radiological features to differentiate IHP from SHP.

Results: Out of the twenty eight consecutive patients with pachymeningitis, 20 were having IHP and 8 were having SHP (Tuberculosis-5, Sarcoidosis-2, Wegener's granulomatosis-1). In IHP, headache and visual symptoms dominated the clinical symptomatology (80% and 75%). In MRI, the peripheral pattern of contrast enhancement was more common with IHP (p=0.03). The posterior falx and tentorium showing a hypointense center ("fibrosis") and enhancing periphery ("active inflammation") together mimicking "Eiffel-by-night" sign was found to be more commonly associated with IHP (60% vs 12.5%, p=0.03). Biopsy was done in 9 patients. At a mean follow-up of 51 months (range 24-144 months), the mean pretreatment clinical score improved from 6.55 to 1.80 in 20 patients with IHP (p<0.001).

Conclusions: Our data on the largest cohort of patients with IHP would shed light into its clinico-radiological spectrum, treatment and outcome. The prognosis is satisfactory if managed appropriately. We have highlighted the role of MRI in differentiating between IHP and other causes of SHP.