A stepwise surgical algorithm using nerve transfers for the treatment of upper extremity acute flaccid myelitis
Erin L Weber, MD, PhD; Division of Plastic and Reconstructive Surgery, University of Southern California, Los Angeles, CA; Mitchel Seruya, MD; University of Southern California, Los Angeles, CA; Children's Hospital Los Angeles, Los Angeles, CA
Background: Since 2013, there has been an abrupt increase in upper extremity acute flaccid myelitis (AFM), attributed to a new subtype of enterovirus compromising the spinal cord anterior horn cells. Acute treatment is largely supportive and functional recovery is infrequent. We propose that nerve transfers are an effective method for restoring clinically significant function. In this study, we describe our stepwise surgical algorithm of nerve transfers for the treatment of upper extremity AFM and present the functional outcomes to date.
Methods: Pediatric cases of AFM were evaluated at the onset of paralysis and at 3-month intervals, using the Medical Research Council (MRC) scale for muscle strength. Patients were stratified by the level of upper extremity weakness. Those without early functional recovery (?M3) were offered surgery by 5-6 months for total paralysis, 6-9 months for shoulder / elbow weakness, and 9-12 months for isolated shoulder weakness. Late-presenting patients (12-24 months) were offered primary nerve transfers as soon as possible. Nerve transfers were performed in 1-2 stages based on the severity of the deficit (Figure 1). Sequential intercostal and phrenic nerve transfers were separated by 3 months. Follow-up ranged from 6-12 months.
Results: Six patients (2.8-15 years) with upper extremity AFM were treated with nerve transfers (Table 1), with the time from illness to surgery ranging from 5.1-19.6 months. Average hospital stays were 2-5 days. There were no major surgical complications. Patient 1, presenting at 12-14 months with poor shoulder abduction (right M1, left M3-), successfully recovered M4 function bilaterally 3-5 months following staged nerve transfers. Patient 2, presenting at 19 months with no shoulder and elbow function (M0), achieved M2- shoulder abduction, M2 elbow flexion, and M4 elbow extension 12 months postoperatively. Three patients with total paralysis underwent first-stage intercostal nerve transfers, with one patient thus far completing second-stage video-assisted phrenic nerve transfer.
Conclusions: Nerve transfers for AFM are limited by a paucity of donor nerves, as even extraplexal donors (ex. CN XI) can be compromised by the virus. We have developed a stepwise surgical algorithm, utilizing innervation to the respiratory muscles to restore upper extremity function. Early outcomes are promising.
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