Abstracts

2434 The frequency and location of complex repetitive discharges in Cervical Dystonia

Abstract

Objectives Cervical dystonia (CD), the most common form of adult focal dystonia, is characterized by sustained and repetitive muscle contrac­tion producing abnor­mal head and neck posture, muscle hypertrophy, pain and tremor.

Complex repetitive discharges (CRDs), detected on needle electromyography (EMG), are bursts of spontaneous trains of complex polyphasic potentials that repeat at a regular frequency (range, 5–100 Hz) and terminate abruptly. The clinical significance of CRDs is unclear though they are reported in both myopathic and neuropathic conditions. CRDs are rarely reported to accompany dystonic posturing. Herein we report the frequency of CRDs amongst patients treated with EMG-guided botulinum toxin (BoNT).

Methods Patients attending a BoNT clinic were prospectively collected from August 2020.

Results During ascertainment, 351 patients received EMG-guided BoNT injections for indications including CD (n=244), temporomandibular-joint dysfunction (n=53), spasticity (n=43) and tremor (n=11). CRDs were identified in 37 CD patients (26 female) with median age 65 years (Range 40–85). CRDs were identified in 6 BoNT naïve patients.

CRDs were identified in single muscles in 29 patients and multiple muscles in 8 patients, including levator scapulae (n=31, 38 muscles), trapezius (n=6), scalenes (n=2, 3 muscles) and sub-mentalis (n=1) muscles. CRDs were identified at the location of prominent pain in 20 of 37 patients.

Conclusions CRDs were present in approximately 16% of CD patients and were not identified in other BoNT indications. Amongst CD patients, CRDs most frequently involved the levator scapulae muscle (79%). The continuous spontaneous activity of CRDs possibly contribute to muscle hypertrophy and pain in CD.

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