Conduction block and positive sharp waves/fibrillation potentials in entrapment neuropathies of the ulnar, radial, and peroneal nerves

Introduction: Entrapment mononeuropathies can cause motor conduction block, positive sharp waves, and fibrillation potentials. Aim: The study aims to find whether there is a relationship between positive sharp waves/fibrillation potentials and conduction block observed in entrapment mononeuropathies. Materials and methods: Patients with ulnar neuropathy at the elbow, radial neuropathy at the spiral groove, and peroneal neuropathy at the fibular head were included in this retrospective study. Nerve conduction study and needle electromyography results of the patients were analysed. Results: The study included a total of patients with 67 ulnar neuropathy, 8 radial neuropathy, and 27 peroneal neuropathy. All radial and peroneal neuropathy patients and 30 ulnar neuropathy patients had positive sharp waves/fibrillation potentials in at least one muscle. Twenty-three ulnar neuropathy patients with these potentials, 6 radial neuropathy patients, and 18 peroneal neuropathy patients had conduction block (p < 0.001). The reduction of compound muscle action potential amplitude in percentage recorded from the abductor digiti quinti/first dorsal interosseous across the elbow segment in ulnar neuropathy patients with and without positive sharp waves/fibrillation potentials was 41.9 ± 35.9/46.6 ± 36.1% and 7.6 ± 16.5/10.4 ± 16.5%, respectively (p < 0.001/p < 0.001). The distal compound muscle action potential amplitudes of ulnar neuropathy patients with these potentials were lower than those of ulnar neuropathy patients without these potentials (p = 0.029 – abductor digiti quinti, p = 0.017 – first dorsal interosseous). No correlation was found between the severity of positive sharp waves/fibrillation potentials and muscle strength in patients with these potentials (p > 0.05). Conclusions: Positive sharp waves/fibrillation potentials and motor conduction block can be seen together in patients with entrapment mononeuropathies. We concluded that there may be no relationship between the severity of these potentials and muscle strength.