American Society for Peripheral Nerve

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Markers of Spontaneous Recovery Versus Surgical Intervention In Acute Flaccid Myelitis (AFM)
Erin L Weber, MD, PhD; Mitchel Seruya, MD
University of Southern California, Los Angeles, CA

Introduction: Acute flaccid myelitis (AFM) is the sudden onset of limb paralysis following a viral illness. Previously rare due to eradication of the poliovirus, AFM is again on the rise, with 150 cases reported in 2016. The purpose of this study is to evaluate patient characteristics and disease severity to better understand markers of spontaneous recovery versus the need for surgical intervention.

Materials and Methods: Retrospective chart review identified twenty-one patients with post-viral, upper extremity AFM treated at our pediatric institution from 2014-2018. Patient age, sex, and history were reviewed. Muscle strength was assessed using the Medical Research Council (MRC) scale at the time of paralysis, 3 months post-paralysis, and at maximal follow-up. A composite strength score was calculated by summing MRC scores for seven upper extremity motor functions (maximum score = 35). Clinically acceptable strength for each muscle group was defined as ≥M3 function.

Results: Age of onset ranged from 2-16 years. 29% of patients with AFM had a pre-existing history of asthma. 63% involved bilateral upper extremity paralysis, with proximal musculature more frequently and severely affected. Other sites of paralysis included the spinal accessory nerve (71%), lower extremity nerves (29%), facial nerve (29%), glossopharyngeal or hypoglossal nerves (24%), and phrenic nerve (19%). Spontaneous recovery of all muscle groups was observed in 50% of limbs and occurred within 3 months of paralysis. Up to 18 months post-paralysis, only 1 additional patient fully recovered. At the onset of paralysis, the mean composite strength score for spontaneously recovered patients was 15, compared to 8 for unrecovered patients requiring surgery (p=0.1). At 3-months post-paralysis, the mean composite score for spontaneously recovered patients was 30, compared to 10 for surgical patients (p<0.01).

Conclusions: Acute flaccid myelitis represents a diagnostic and therapeutic challenge for pediatricians and surgeons. Patients with asthma appear to be more susceptible to post-viral paralysis. Regions outside the brachial plexus may be affected and eliminate routine donor options for nerve transfer, such as the spinal accessory nerve. A higher initial composite score is associated with a greater likelihood for spontaneous recovery and the indication for surgical intervention is greater for patients without significant recovery by 3-months post-paralysis.

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