Quantitative analysis of myokymic discharges in radiation versus nonradiation cases

Electromyography findings in radiation-induced unilateral tongue immobility

BACKGROUND

We used electromyography to characterize hypoglossal nerve function among radiation-treated head and neck cancer survivors with later onset unilateral tongue immobility.

METHODS

Patients with unilateral tongue immobility without evidence of recurrent cancer were seen at a tertiary academic institution between February and September 2021. All patients were at least 2 years post-treatment with radiation therapy for head and neck squamous cell carcinoma. Participants were under annual surveillance and displayed no evidence of operative injury to the hypoglossal nerve.

RESULTS

The median symptom-free interval for the 10 patients included in this study was 13.2 years (range 2-25 years). Myokymia alone was present in 3 of 10 patients, fibrillation potentials alone were present in 3 of 10 patients, and 1 subject displayed both fibrillation and myokymia. Three out of 10 patients had normal hypoglossal nerve function.

DISCUSSION

These findings highlight how disparate mechanisms may underlie similar clinical presentations of radiation-induced neuromuscular dysfunction.

Contactin-Associated Protein-Like 2-Related Peripheral Nerve Hyperexcitability Associated With Charcot-Marie-Tooth Type 4F

Contactin-associated protein-like 2 autoimmunity is an uncommon disorder resulting in peripheral nerve hyperexcitability or encephalitis. In a fifth of cases, onset may be provoked by thymoma, but other associations are largely unknown. We report a patient with anti-contactin-associated protein-like 2-related peripheral nerve hyperexcitability arising in the setting of Charcot-Marie-Tooth type 4F and discuss potential mechanisms underlying the association.

Needle Electromyography Waveforms During Needle Electromyography

Needle electromyography (EMG) waveforms recorded during needle EMG help to define the type, temporal course, and severity of a neuromuscular disorder. Accurate interpretation of EMG waveforms is a critical component of an electrodiagnostic examination. This article reviews the significance of spontaneous EMG waveforms and changes in voluntary motor unit potentials in neuromuscular disorders.