Evaluation and Management of Idiopathic Unilateral Footdrop.

Background: We evaluated patients who were followed after acutely developing single-sided footdrop and improving with conservative management or spontaneously.

Methods: In 2019 and 2020, ten patients were retrospectively evaluated for unilateral weakness of the lower extremity in the form of absent dorsiflexion at the ankle joint and were given a diagnosis of footdrop without etiologic cause. Patients were followed for 18 months. Patients were evaluated for acute footdrop of the affected extremity with electromyography, lumbar spine magnetic resonance imaging (MRI), knee MRI, peripheral MRI neurography, and noncontrast brain MRI. Each patient was evaluated for a history of COVID-19 infection during the past year. Patients with any identified cause were excluded.

Results: Initial evaluation of muscle strength revealed 0/5 by the Medical Research Council muscle testing scale. In two patients, muscle strength was 3/5 at month 6 and in eight patients it was 4/5. Muscle strength of all of the patients improved to 5/5 at 1 year. Six patients were dispensed an ankle-foot orthosis, and nine patients performed physical therapy. Electromyography identified significant neuropathy at the level of the common peroneal at the fibular head in all of the patients. Compared with peroneal nerve stimulation below and above the fibular head in the lateral popliteal fossa, a 50% reduction in sensory amplitude and motor conduction slowing greater than 10 m/sec were present. Knee MRI revealed no masses, edema, or anatomical variations at the level of the fibular head.

Conclusions: Spontaneous resolution of unilateral acute footdrop without an etiologic cause can occur within 1 year.