Side-locked Headache Associated with Habitual Neck-Shoulder Mobile Phone Clamping: A Case Series.

Side-locked headache is commonly regarded as a warning sign for secondary intracranial pathology; however, its musculoskeletal causes may be underrecognized. We report a series of seven patients with strictly unilateral headache consistently and temporally associated with the habitual clamping of a mobile phone between the neck and shoulder during hands-free multitasking. The headache was nonthrobbing, lacked migrainous or cranial autonomic features, and was reproducible with cervical palpation or sustained neck movements. Neurological examination and neuroimaging were normal in all cases. Cervical muscle tenderness, spasm, and trigger point-mediated referred pain were prominent findings. Conservative management focusing on avoidance of the implicated posture, posture correction, and physiotherapy was associated with substantial improvement or complete resolution in all patients. This series highlights neck-shoulder mobile phone clamping as a common posture-related trigger for cervicogenic or myofascial headache and underscores the importance of assessing smartphone-handling behaviors in patients with unilateral headache. These findings are hypothesis-generating and do not establish causality.