Objective

To determine the safety, tolerability, and efficacy of fluoxetine for proven or presumptive enterovirus (EV) D68-associated acute flaccid myelitis (AFM).

Methods

A multicenter cohort study of US patients with AFM in 2015-2016 compared serious adverse events (SAEs), adverse effects, and outcomes between fluoxetine-treated patients and untreated controls. Fluoxetine was administered at the discretion of treating providers with data gathered retrospectively. The primary outcome was change in summative limb strength score (SLSS; sum of Medical Research Council strength in all 4 limbs, ranging from 20 [normal strength] to 0 [complete quadriparesis]) between initial examination and latest follow-up, with increased SLSS reflecting improvement and decreased SLSS reflecting worsened strength.

Results

Fifty-six patients with AFM from 12 centers met study criteria. Among 30 patients exposed to fluoxetine, no SAEs were reported and adverse effect rates were similar to unexposed patients (47% vs 65%, p = 0.16). The 28 patients treated with >1 dose of fluoxetine were more likely to have EV-D68 identified (57.1% vs 14.3%, p < 0.001). Their SLSS was similar at initial examination (mean SLSS 12.9 vs 14.3, p = 0.31) but lower at nadir (mean SLSS 9.25 vs 12.82, p = 0.02) and latest follow-up (mean SLSS 12.5 vs 16.4, p = 0.005) compared with the 28 patients receiving 1 (n = 2) or no (n = 26) doses. In propensity-adjusted analysis, SLSS from initial examination to latest follow-up decreased by 0.2 (95% confidence interval [CI] -1.8 to +1.4) in fluoxetine-treated patients and increased by 2.5 (95% CI +0.7 to +4.4) in untreated patients (p = 0.015).

Conclusion

Fluoxetine was well-tolerated. Fluoxetine was preferentially given to patients with AFM with EV-D68 identified and more severe paralysis at nadir, who ultimately had poorer long-term outcomes.

Classification of evidence

This study provides Class IV evidence that for patients with EV-D68-associated AFM, fluoxetine is well-tolerated and not associated with improved neurologic outcomes.

Acute flaccid myelitis (AFM) is a disabling, polio-like illness mainly affecting children. Outbreaks of AFM have occurred across multiple global regions since 2012, and the disease appears to be caused by non-polio enterovirus infection, posing a major public health challenge. The clinical presentation of flaccid and often profound muscle weakness (which can invoke respiratory failure and other critical complications) can mimic several other acute neurological illnesses. There is no single sensitive and specific test for AFM, and the diagnosis relies on identification of several important clinical, neuroimaging, and cerebrospinal fluid characteristics. Following the acute phase of AFM, patients typically have substantial residual disability and unique long-term rehabilitation needs. In this Review we describe the epidemiology, clinical features, course, and outcomes of AFM to help to guide diagnosis, management, and rehabilitation. Future research directions include further studies evaluating host and pathogen factors, including investigations into genetic, viral, and immunological features of affected patients, host-virus interactions, and investigations of targeted therapeutic approaches to improve the long-term outcomes in this population.