Electromyographic evaluation of adult Labrador retrievers with type-II muscle fiber deficiency

Labrador Retrievers with type-II muscle fiber deficiency were examined electrodiagnostically. Electromyographic changes consisted of positive sharp waves, fibrillation potentials, bizarre high-frequency discharges, and, rarely, myotonic-like discharges. Fasciculation potentials were recorded infrequently. Fibrillation potentials and bizarre high-frequency discharges were the most commonly observed electromyographic changes. Bizarre high-frequency discharges were prominent in muscles of the head and neck, proximal muscles of the thoracic limbs, and the thoracolumbar paraspinal musculature. Marked abnormalities were not observed in the motor nerve conduction velocity. Decremental responses of the evoked compound muscle action potential to repetitive nerve stimulation were not observed.