Treatment of spontaneous anterior interosseous nerve palsy.

Objective: The purpose of this study was to clarify the clinical outcomes of spontaneous anterior interosseous nerve palsy (AINP) treated nonsurgically or surgically.

Methods: The authors retrospectively evaluated the clinical course of 27 patients affected with AINP, treated nonsurgically or surgically. Thirteen patients underwent surgical treatment (interfascicular neurolysis), and 14 patients underwent conservative nonsurgical treatment. The mean patient age at the onset of symptoms was 49 years (range 17-77 years). The mean follow-up duration from onset to the latest follow-up examination was 23 months (range 12-38 months).

Rresults: In 12 of 14 patients receiving conservative treatment, signs of recovery from the palsy were obtained within 6 months. These patients showed a recovery of manual muscle test (MMT) grade ≥ 3. In contrast, 2 patients who took more than 12 months from symptom onset to initial recovery showed poor recovery (MMT grade ≤ 2). Surgical treatment was performed in 13 patients because of no sign of recovery from palsy. The mean period from symptom onset to the operation was 8.4 months (range 6-14 months). Ten of 13 patients who underwent surgical treatment within 8 months after symptom onset showed good recovery, with MMT grade ≥ 4. However, 3 patients who underwent surgical treatment more than 12 months after onset showed recovery with MMT grade ≤ 3.

Conclusions: Conservative treatment for AINP may be continued when patients show signs of recovery within 6 months after symptom onset. In contrast, surgical treatment may be performed within 8 months from the onset of symptoms when the patients show no recovery signs for 6 months.

Abbreviations: AIN = anterior interosseous nerve; AINP = anterior interosseous nerve palsy; FDP1 = flexor digitorum profundus of the index finger; FPL = flexor pollicis longus; MMT = manual muscle test; NSG = nonsurgical treatment group; SG = surgical treatment group.