Multifocal posterior interosseous nerve torsion: two case reports

We report two rare cases of multifocal torsion of the posterior interosseous nerve (PIN) that presented with isolated motor deficits in the upper extremity. Both patients experienced acute weakness in finger and thumb extension without sensory loss. Imaging and electrodiagnostic studies confirmed PIN involvement. Surgical exploration revealed multiple torsion points with segmental intraneural rupture requiring nerve grafting. These cases represent the first documented instances of multifocal PIN torsion that were confirmed radiologically and intraoperatively. Early recognition, aided by high-resolution ultrasound and electrodiagnostic studies, followed by prompt surgical intervention, led to gradual functional recovery. These findings highlight an uncommon structural cause of PIN palsy and emphasize the importance of considering nerve torsion in the differential diagnosis of isolated motor mononeuropathies.