Calcitonin gene related peptide in peripheral blood as a diagnostic marker in recurrent painful ophthalmoplegic neuropathy/ophthalmoplegic migraine

Abstract

Recurrent Painful Ophthalmoplegic Neuropathy (RPON) / Ophthalmoplegic migraine (OM) is a rare neurologic disorder. Its nomenclature, classification and pathophysiology are still debatable despite its initial description dating back to more than a century. While the headache characteristics, temporal profile and response to treatment makes it similar to migraine; the nerve enhancement on imaging points towards a pathology primary to cranial nerves. Our objective was to determine the serum Calcitonin gene related peptide (S.CGRP) levels in peripheral blood in RPON/OM and assess if any correlation exists between the two. 31 clinically suspected RPON/ OM patients were recruited as per the predefined inclusion criteria.16 patients were excluded after investigations.Serum CGRP levels were estimated in ictal and interictal phase (after at least two weeks of clinical resolution of symptoms) and in matched healthy controls. Serum CGRP level were analyzed in 15 patients in ictal phase,12 patients of interictal OM and in 12 age and sex matched healthy controls. S.CGRP levels were found to be significantly elevated (p= 0.048) during the ictal phase (50.2 ng/L) compared to matching controls (33.2 ng/L). Serum CGRP level of 35.46 ng/L ictal phase of ophthalmoplegic migraine patients has sensitivity of 86.7% and specificity of 75%. Serum CGRP levels in the ictal phase, positively correlated with the duration of chronic headaches.There was no gender variability in S. CGRP levels. The raised levels of Serum CGRP levels may indicate a migrainous etiology of this disorder. It may be used as biomarker when in diagnostic dilemma.