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Acute Flaccid Myelitis: Mid-Term Clinical Course of Knee Extension Paralysis and Outcomes of Nerve Transfer
Kazuteru Doi1, Yasunori Hattori1, Akio Maruyama1
1Department of Orthopedic Surgery, Ogori Daiichi General Hospital, Yamaguchi, Japan.
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.
Insights
Acute flaccid myelitis (AFM) can cause leg paralysis. Contralateral obturator nerve-to-femoral nerve transfer (CONFNT) surgery shows promise for restoring knee extension if performed within 8 months of paralysis onset.
Area of Science:
- Neurology
- Orthopedic Surgery
- Pediatric Neurology
Background:
- Acute flaccid myelitis (AFM) is a rare, debilitating illness causing sudden limb paralysis, resembling poliomyelitis.
- Lower extremity paralysis, particularly affecting knee extension, presents a significant challenge in AFM patients.
- Understanding the natural course and surgical restoration options for knee extension in AFM is crucial.
Purpose of the Study:
- To evaluate the mid-term clinical course of knee extension in patients with AFM.
- To assess the efficacy of contralateral obturator nerve-to-femoral nerve transfer (CONFNT) in restoring knee extension in AFM.
- To determine the optimal timing for CONFNT to maximize functional recovery.
Main Methods:
- Retrospective review of 26 AFM patients with lower extremity palsy.
- Assessment of knee extension using British Medical Research Council (MRC) grading and surface electromyography (EMG).
- Analysis of spontaneous recovery and outcomes following CONFNT in a subset of patients.
Main Results:
- Spontaneous recovery of knee extension to MRC grade M2 or better was unlikely if paralysis persisted beyond 6 months, especially with concurrent hip adductor paralysis.
- CONFNT performed within 8 months of paralysis onset resulted in M4 knee extension in 2 out of 5 patients.
- CONFNT performed later (around 12 months) yielded less significant recovery (M1-M3).
Conclusions:
- While similar to poliomyelitis, AFM presents unique recovery patterns for lower extremity paralysis.
- Early intervention with CONFNT (within 8 months) appears to be a reliable surgical option for restoring knee extension in AFM.
- The timing of surgical reconstruction is a critical factor for successful functional restoration in AFM-related knee extension deficits.
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