This first study utilizing US in Bell's palsy highlights its role in outcome prediction and contributes to our understanding of recovery processes in this common neurological disorder.

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High-Resolution Ultrasound as a Diagnostic Adjunct in Common Peroneal Neuropathy E ntrapment neuropathy of the common peroneal nerve is caused mostly by compression at the fibula head region. 1 In cases of severe axon loss, demonstration of conduction block or reduction of conduction velocity would be difficult. Apart from demyelination, mechanical factors and ischemic mechanisms may play a role. 2 Differing degrees of damage to individual nerve fascicles may occur within the common peroneal nerve, 3 rendering interpretation of needle electromyography (EMG) difficult. High sciatic nerve lesions are also known to mimic peroneal neuropathy at the fibular head if electrodiagnostic examination is not performed adequately. 1 High-resolution ultrasonography (US) may be a potential diagnostic tool in these technically challenging circumstances. Methods. Over a 1-year period, we studied 32 healthy controls and 8 otherwise well patients who presented with footdrop. All controls and patients underwent US of the peroneal nerve as well as electrodiagnostic studies. Peroneal sensory and motor nerve conduction studies (NCS) were performed with standard techniques. Blinded US examination was conducted with a General Electric Logiq 7 Pro machine (GE Healthcare, Chalfont St Giles, England), using a 5-to 10-MHz linear array transducer. Transverse scans of the peroneal nerves were obtained at the level of the fibula head bilaterally with the subject's legs supported and slightly flexed (20°to 30°) at the knees in the lateral position (Figure 1). We measured the maximum transverse length, maximum transverse breadth (perpendicular to transverse length), ratio of these 2 parameters (breadth/length), and cross-sectional area (Figure 2). The upper limit of normality was 2 SDs above the mean. PϽ.05 was considered statistically significant.

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Measurement of the decremental muscle response to repetitive nerve stimulation (RNS) has low yields for the diagnosis of neuromuscular transmission defects compared with single fiber electromyography (SFEMG). We compared area and amplitude of muscle responses to RNS in 87 patients and 30 controls, using SFEMG as the reference standard. Decrement of response area provided additional diagnostic yields of 5.3% to 30% depending on the muscle examined and disease severity, and is recommended as a diagnostic adjunct to measurement of amplitude decrement during RNS.