Traumatic bilateral isolated palsy of Flexor Pollicis Longus: an uncommon case report

Introduction and importance: Flexor Pollicis Longus (FPL) lies in the volar compartment of the forearm and is responsible for the flexion of the distal phalanx of the thumb. The innervation of FPL is provided by an isolated motor branch of the anterior interosseus nerve (AIN), a branch of the median nerve. AIN disfunction causes symptoms of exclusive motor involvement concerning the FPL muscle. Solitary paralysis of the FPL is very uncommon in clinical practice. Presentation of the case: We report the case report of a bilateral isolated paralysis of Flexor Pollicis Longus (FPL) that occurred after a trauma. Two years after the injury, no organic lesions were found and instrumental exams did not suggest any diagnosis. Surgical exploration of FPL and its innervation allowed to diagnose a pure post-traumatic bilateral neuroapraxia sustained by the presence of post traumatic connective fibrous bands. Discussion: Diagnostic and therapeutic bands release allowed the immediate functional recovery of the nerve function and the consequent restoration of FPL function. The surgical exploration of the suspected injured nerve was the resolutive procedure for diagnosis and treatment of the disease. During the surgical exploration, the cause of FPL palsy was identified and removed with a complete recovery of the neuromuscular unit function. Conclusion: This case is very peculiar because of the clinical presentation with an important bilateral functional limitation of FPL. The release allowed the complete restoration of FPL function. No similar cases were described in literature.