Clinical characteristics and results after conservative treatment or interfascicular neurolysis of 58 limbs with spontaneous posterior interosseous nerve palsy: A prospective Japanese multicenter study.

Abstract

Spontaneous posterior interosseous nerve (PIN) palsy is a rare condition with controversial clinical features. Although this palsy is conventionally treated conservatively, interfascicular neurolysis to release hourglass-like fascicular constrictions has also been recommended. This study aimed to clarify the clinical characteristics and treatment guidelines for this palsy. Fifty-eight limbs with spontaneous PIN palsy receiving conservative treatment or interfascicular neurolysis. The presence of pain as a premonitory symptom and the degree of muscle weakness were investigated. Patients were followed periodically from 3 months after palsy onset to either recovery or ≥36 months afterwards. Limbs recovering to manual muscle testing (MMT) grade 4 or better for both the extensor pollicis longus and extensor digitorum were rated as Good recovery, with all others judged as Poor. Good recovery was achieved in 31 of 34 limbs treated conservatively and 19 of 24 of limbs by interfascicular neurolysis. Younger age at onset was the factor significantly associated with achieving Good recovery in 58 limbs treated by conservatively or interfascicular neurolysis. In the 24 limbs treated by interfascicular neurolysis, early timing of surgery was the factor significantly associated with attaining Good recovery. All 27 limbs with conservative treatment displaying ≥1 grade of MMT improvement within 6 months after onset achieved Good recovery. In the 23 limbs with Poor recovery at 6 months by conservative treatment, Good recovery was attained in 4 of 7 limbs by continuing conservative treatment and in 12 of 16 limbs by subsequent interfascicular neurolysis. Although the latter treatment tended to produce better results, no significant difference was detected. Diverse clinical characteristics of spontaneous PIN palsy are useful for diagnosis. Conservative treatment is advisable within 6 months after onset of palsy. If no improvement is observed, interfascicular neurolysis without delay is a reasonable option.