Acute Flaccid Myelitis

Abstract

Background: Acute flaccid myelitis (AFM) is a rare debilitating poliomyelitis-like illness characterized by the sudden onset of flaccid palsy in the extremities. The purpose of this study was to report the mid-term clinical course of knee extension in AFM and the effect of contralateral obturator nerve-to-femoral nerve transfer (CONFNT) for restoration of knee extension in AFM. Methods: Twenty-six patients with lower extremity palsy due to AFM were referred to our clinic for possible surgical reconstruction. Their median age was 4.0 years, and the first evaluation of the palsy was done at a mean of 6 months after paralysis onset. The paralysis ranged from lower limb monoplegia to quadriplegia. The clinical course of knee extension was assessed using the British Medical Research Council (MRC) grading scale and surface electromyography (EMG). Five patients with unilateral paralysis of knee extension underwent CONFNT. Results: The mean follow-up period for 19 limbs with complete paralysis of knee extension (MRC grade M0) in 13 patients who were evaluated for spontaneous recovery was 43 months. No patient who had complete paralysis of knee extension at >6 months and paralysis of the hip adductor muscle had improvement of knee extension to better than M2. Five of the original 26 patients were treated with CONFNT and followed for a mean of 61 months. Two of 5 patients had the CONFNT ≤8 months after paralysis onset and obtained M4 knee extension. Only 1 of the 3 patients with CONFNT performed approximately 12 months after paralysis onset obtained M3 knee extension; the other 2 obtained only M1 or M2 knee extension. Conclusions: The paralysis of the lower extremity in our patients with AFM was similar to that in poliomyelitis. However, in AFM, spontaneous recovery of knee extension was possible if there were signs of recovery from hip adductor paralysis up to 6 months after paralysis onset. CONFNT may enhance the recovery of knee extension and seems to be a reliable reconstruction for restoring knee extension if performed no more than 8 months after paralysis onset. Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.