Evaluation of temporalis muscle thickness (TMT) in diagnosed cases of migraine and its comparison with controls with no headaches.

Many migraine patients often complain of temple swelling during attacks and sometimes it persists during attack free periods also, especially in chronic headache patients. Differential swelling of temple is also noticed in unilateral side locked migraine patients. This suggests that motor component of trigeminal nerve supplying temple and jaw muscles may also get activated in some migraineurs causing progressive hypertrophy of temporalis muscle causing swelling of temples.

Migraine patients fulfilling ICHD-3 criteria (n- 435) and age matched controls (n-408) were included in this prospective observational study conducted over a period of 2 years. In both cases and controls, TMT was assessed in brain T-1 weighted Magnetic Resonance axial images in plane oriented parallel to the anterior-posterior commissure line. The measurements were taken perpendicular to the long axis of the temporal muscle using the orbital roof and the Sylvian fissure as anatomical landmarks.

Average TMT in cases versus controls was 0.79 ± 0.18cm (right TMT-0.79 ± 0.18 and left TMT 0.79 ± 0.19) and 0.47 ± 0.08cm (right TMT- 0.46 ± 0.09 and left TMT 0.48 ± 0.08) respectively, and the difference between two groups was significant (p-value 0.001). Chronic migraine (21%) cases  has significantly more TMT in comparison to episodic migraine (79%) cases. Also significant difference in  average TMT found in female (n- 373, TMT 0.8 ± 0.19cm) and male (n-72, TMT-0.74 ± 0.15cm) patients. But no significant difference was found in TMT (p value 0.613) in patients with (n-241, TMT-0.79 ± 0.19cm ) and without (n-194 , TMT- 0.79 ± 0.18cm) cranial autonomic symptoms.

Increase TMT in migraine patients suggests possible additional activation of motor component of trigeminal nerve along with other components of trigemino-vascular pathway in genetically susceptible individuals.