Clinical and electrophysiological characterization of myokymia and neuromyotonia in Jack Russell Terriers.
BACKGROUND
Generalized myokymia and neuromyotonia (M/NM) in Jack Russell Terriers (JRTs) is related to peripheral nerve hyperexcitability syndrome in humans, a symptom complex resulting from diverse etiologies.


OBJECTIVE
Clinical and electrodiagnostic evaluation is used to narrow the list of possible etiological diagnoses in JRTs with M/NM.


METHODS
Nine healthy JRTs and 8 affected JRTs.


METHODS
A prospective study was conducted comparing clinical and electrophysiological characteristics in 8 JRTs affected by M/NM with 9 healthy JRT controls.


RESULTS
All affected dogs except 1 had clinical signs typical of hereditary ataxia (HA). In 6 dogs, neuromyotonic discharges were recorded during electromyogram. Motor nerve conduction studies showed an axonal neuropathy in only 1 affected dog. Compared with controls, brainstem auditory-evoked potentials (BAEP) showed prolonged latencies (P<.05) accompanied by the disappearance of wave components in 3 dogs. Onset latencies of tibial sensory-evoked potentials (SEP) recorded at the lumbar intervertebral level were delayed in the affected group (P<.001). The BAEP and SEP results of the only neuromyotonic dog without ataxia were normal.


CONCLUSIONS
The BAEP and spinal SEP abnormalities observed in JRTs with M/NM were associated with the presence of HA. Therefore, these electrophysiological findings presumably arise from the neurodegenerative changes characterizing HA and do not directly elucidate the pathogenesis of M/NM. An underlying neuronal ion channel dysfunction is thought to be the cause of M/NM in JRTs.
Vanhaesebrouck
A E
AE
Department of Small Animal Medicine and Clinical Biology, Faculty of Veterinary Medicine, Ghent University, Ghent, Belgium. av354@cam.ac.uk
Van Soens
I
I
Poncelet
L
L
Duchateau
L
L
Bhatti
S
S
Polis
I
I
Diels
S
S
Van Ham
L
L
D000818:Animals; D004283:Dog Diseases / Q000503:physiopathology*; D004285:Dogs; D055724:Electrophysiological Phenomena; D005260:Female; D020386:Isaacs Syndrome / Q000503:physiopathology / Q000662:veterinary*; D008297:Male; D020385:Myokymia / Q000503:physiopathology / Q000662:veterinary*; D009431:Neural Conduction / Q000502:physiology