Subbasal Nerve Plexus Changes in Chronic Migraine

PURPOSE: Migraine is a multifactorial disorder that presents with unilateral headache and several sensory symptoms. Photophobia is one of the ophthalmic manifestations that cause significant morbidity. The trigeminal pathway that innervates the cornea in the form of afferents has been implicated in photophobia associated with chronic migraine. This study investigates changes in the corneal subbasal nerve plexus (SBNP) in chronic migraine patients with and without photophobia. METHODS: Thirty-six patients with migraine and photophobia (group 1), 24 patients with migraine without photophobia (group 2), and 24 age- and sex-matched controls (group 3) were studied. A detailed history analysis and ophthalmic evaluation were performed on all subjects. In vivo confocal microscopy (IVCM) with automated CCMetrics software was used to quantify changes in the SBNP in all 3 groups. Measured parameters were compared using analysis of variance. RESULTS: Analysis of corneal SBNP features revealed a significant decrease in the corneal nerve fiber length (14.76 ± 3.98 mm/mm), total branch density (43.37 ± 21.63 branch points/mm), nerve branch density (30.19 ± 15.76 number of branches/mm), and fiber area (0.005 ± 0.001 total nerve fiber area/mm) in patients of group 1 compared with group 2 (P < 0.05). CONCLUSIONS: Structural changes in nociceptive corneal axons in the SBNP of patients with migraine with photophobia lend further support to the hypothesis that the trigeminal system plays a critical role in the pathogenesis of ocular symptoms in migraine. Our observations demonstrate that SBNP changes on IVCM may serve as a potential imaging marker for ocular symptoms of chronic migraine, and this warrants further investigation.