An Vanhaesebrouck

Myokymia and neuromyotonia in 37 Jack Russell terriers

The clinical and clinicopathological characteristics, treatment and outcome of vermicular muscle contractions (myokymia) and generalized muscle stiffness (neuromyotonia) in 37 Jack Russell terriers were evaluated retrospectively. Thirty dogs were affected by both disorders, whereas seven were presented with myokymia and never developed neuromyotonia. Clinical signs started at the mean age of 8 months. Except for signs of myokymia and neuromyotonia, clinical and neurological examination was normal in all dogs. Thirty dogs demonstrated typical signs of hereditary ataxia. Changes in serum chemistry included increased creatine kinase, aspartate aminotransferase and alanine aminotransferase concentrations. Electromyographic abnormalities, especially in muscles showing macroscopically visible myokymia, consisted of semirhythmic bursts of doublet, triplet, or multiplet discharges of a single motor unit. The amplitudes varied between 80 μV and 1 mV and occurred with an interburst frequency between 10 and 40 Hz and an intraburst frequency between 150 and 280 Hz. Most dogs were treated with a sodium channel blocker with variable results. Seven dogs died (most likely because of hyperthermia) or were euthanased during a neuromyotonic attack; 15 dogs were euthanased due to worsening of clinical signs, or lack of or no long-lasting effect of medication, and three were euthanased for unknown or unrelated reasons. Nine dogs were lost to follow-up and three were still alive 5-10.5 years after the start of clinical signs. In conclusion, young Jack Russell terriers with myokymia and neuromyotonia should undergo a complete blood and electrophysiological examination. Long-term prognosis is not favourable.

Temporal lobe epilepsy in a cat with a pyriform lobe oligodendroglioma and hippocampal necrosis

A 14-year-old male domestic shorthair cat presented with an acute onset of aggressive behaviour, fear and hypersalivation. Neurological examination revealed bilateral mydriasis and left-sided facial twitching and hemiparesis. Magnetic resonance imaging (MRI) showed moderate bilateral symmetrical T2-hyperintensity along the entire hippocampus and bilateral asymmetric T2-hyperintensity in the pyriform lobes. Marked bilateral contrast enhancement of the hippocampus was evident on post-contrast T1-weighted images. The partial complex seizures were refractory to medical treatment and the cat was euthanased 4 days after admission. The clinical and MRI findings were consistent with feline hippocampal necrosis (FHN). On histopathology, neuronal necrosis and astrocytosis were present in the hippocampi and pyriform lobes. In addition, an oligodendroglioma was detected in the right pyriform lobe. Contrary to previous reports of FHN in which no underlying cause could be identified, we believe that in this case the seizure focus arose from a neoplastic lesion within the right pyriform lobe. This unique case report represents the so-called ‘dual pathology’ of temporal lobe epilepsy in humans, in which an extrahippocampal lesion within the temporal lobe results in hippocampal sclerosis.

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. ANIMALS 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 AND CLINICAL IMPORTANCE 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.

Experimental validation of in silico predicted KCNA1, KCNA2, KCNA6 and KCNQ2 genes for association studies of peripheral nerve hyperexcitability syndrome in Jack Russell Terriers

KCNA1, KCNA2, KCNA6 and KCNQ2 are associated with peripheral nerve hyperexcitability in humans. In order to determine if these genes are also involved in Jack Russell Terriers with a similar syndrome characterized by myokymia and neuromyotonia, their predicted canine orthologs were first validated experimentally. They were found either incompletely or even incorrectly annotated, mainly due to gaps in the canine genomic sequence and insufficient transcript data. Canine KCNQ2 was found to contain 20 coding exons, of which three are not described in humans. It encodes for at least 14 different transcript variants in the frontal cortex of a single dog, of which only four are also described in humans. Mutation detection in Jack Russell Terriers diagnosed with peripheral nerve hyperexcitability revealed no pathogenetic relevant structural mutations. However, the four missense sequence variations and the 14 transcript variants of KCNQ2 will contribute to the study of the functional diversity of voltage-gated potassium channels.

Magnetic stimulation of the radial nerve in dogs and cats with brachial plexus trauma: A report of 53 cases

Brachial plexus trauma is a common clinical entity in small animal practice and prognostic indicators are essential early in the course of the disease. Magnetic stimulation of the radial nerve and consequent recording of the magnetic motor evoked potential (MMEP) was examined in 36 dogs and 17 cats with unilateral brachial plexus trauma. Absence of deep pain perception (DPP), ipsilateral loss of panniculus reflex, partial Horners syndrome and a poor response to MMEP were related to the clinical outcome in 29 of the dogs and 13 of the cats. For all animals, a significant difference was found in MMEP between the normal and the affected limb. Absence of DPP and unilateral loss of the panniculus reflex were indicative of an unsuccessful outcome in dogs. Additionally, the inability to evoke a MMEP was associated with an unsuccessful outcome in all animals. It was concluded that magnetic stimulation of the radial nerve in dogs and cats with brachial plexus trauma may provide an additional diagnostic and prognostic tool.

A Novel Movement Disorder in Related Male Labrador Retrievers Characterized by Extreme Generalized Muscular Stiffness

OBJECTIVES To describe the clinical phenotype of a new motor disorder in Labrador Retrievers. ANIMALS AND METHODS Case series study. Seven young male Labrador Retrievers presented for evaluation of stiff gait. RESULTS All affected dogs had generalized muscular stiffness, persistent at rest and resulting in restricted joint movements. They showed a forward flexed posture, festinating gait, and bradykinesia. Signs developed between 2 and 16 months of age and tended to stabilize in adulthood. Needle electromyogram in the conscious state showed continuous motor unit activity in resting epaxial and proximal limb muscles. This activity was abolished by general anesthesia. Muscle and nerve histopathology was normal. In 2 dogs necropsied, astrocytosis was evident throughout the spinal cord gray matter, reticular formation and caudate nuclei. Decreased neuronal counts were selectively found in the spinal cord Rexeds lamina VII, but not in VIII and IX. Pedigree analysis showed that the affected dogs were from 5 related litters. CONCLUSIONS AND CLINICAL IMPORTANCE This new hypertonicity syndrome in Labrador Retrievers is unique because of the selective distribution of the histological lesions, the lack of progression in adulthood, and its exclusive occurrence in male dogs. Pedigree analysis suggests an X-linked hereditary disease, although other modes of inheritance cannot be ruled out with certainty. We hypothesize that altered output from basal nuclei and reticular formation together with motor neuron disinhibition caused by a decreased number of spinal cord interneurons leads to the muscular stiffness.

Inspiratory stridor secondary to palatolingual myokymia in a Maltese dog

A nine-year-old male Maltese dog was presented with an eight-month history of inspiratory stridor leading to exertional dyspnoea and cyanosis. Myokymic contractions in the palatolingual muscles were noticed and confirmed by electromyography. Brain computer tomography-scan showed ventricular dilatation. Cerebrospinal fluid analysis revealed a slightly elevated protein level. Treatment with slow-release phenytoin was unsuccessful and symptoms gradually worsened over the next nine months. At post-mortem examination a small pituitary adenoma was found. Apart from a single canine report of facial myokymia, this is the only other description of spontaneous focal myokymia in animals. Palatolingual myokymia has only been reported in one human being. Although the co-occurrence with a pituitary adenoma might be incidental, a paraneoplastic pathogenetic mechanism is proposed. Its unique clinical presentation adds a new, albeit uncommon, syndrome to the differential diagnosis of upper airway complaints in dogs.

Comparison of gabapentin versus topiramate on clinically affected dogs with Chiari-like malformation and syringomyelia

To date there is no evidence-based data for efficacious treatment of neuropathic pain in dogs with Chiari-like malformation (CM) and syringomyelia (SM). The objective of this prospective cross-over study was to compare the effect of gabapentin versus topiramate, as an add-on treatment to carprofen, on quality of life (QoL) of dogs experiencing signs of neuropathic pain due to CM/SM. A visual analogue scale (VAS) was used to assess the QoL: (1) on day 0; (2) after 1 week of carprofen only; (3) after 2 weeks on carprofen and gabapentin; and (4) after 2 weeks on carprofen and topiramate. No significant difference was observed between VAS after gabapentin or topiramate (P=0.91). However, an improvement in QoL was observed when gabapentin was compared with baseline (P=0.009), but not for topiramate. In conclusion, the addition of gabapentin was more effective in improving QoL than carprofen alone, but the study failed to identify that gabapentin was more efficacious than topiramate. Perhaps the more favourable side effect profile of the former makes it more suitable for the treatment of neuropathic pain associated with CM/SM but further placebo-controlled trials are required to assess the efficacy of these drugs.

Association between the findings on magnetic resonance imaging screening for syringomyelia in asymptomatic Cavalier King Charles spaniels and observation of clinical signs consistent with syringomyelia in later life

A questionnaire-based study was used to investigate the association between the findings on magnetic resonance imaging (MRI) screening for syringomyelia (SM) in 79 asymptomatic Cavalier King Charles spaniels (CKCS) and the subsequent development of clinical signs consistent with SM in later life. Owners reported clinical signs consistent with SM in 13/79 (16%) dogs at the time of the questionnaire. A significantly greater proportion of CKCS with a syrinx visible on MRI screening showed clinical signs in later life (9/25, 36%) than dogs without a visible syrinx (4/54, 7%; odds ratio 6.9). Whether the findings of MRI screening can be used to indicate the likelihood of an asymptomatic CKCS developing clinical signs consistent with SM in later life warrants further prospective study in a larger cohort of dogs.

Surgical treatment of dorsal hemivertebrae associated with kyphosis by spinal segmental stabilisation, with or without decompression

This retrospective case series examined the effectiveness of spinal segmental stabilisation, with or without decompression, in nine dogs with neurological deficits associated with dorsal hemivertebrae. Data on signalment, preoperative neurological status, imaging findings, surgical techniques and outcome were evaluated. All cases occurred in young or adult, small-breed dogs with neurological signs ranging from progressive moderate pelvic limb ataxia to non-ambulatory paraparesis. Six dogs also showed urinary and faecal incontinence. In each dog, one or more dorsal thoracic hemivertebra(e) were detected by radiography and MRI. In all dogs, hemivertebra(e) were associated with kyphosis and reduced vertebral canal diameter. All dogs were surgically managed with spinal segmental stabilisation, using Steinmann pins and orthopaedic wires and/or sutures attached to the spinous processes. Three dogs also underwent additional decompressive surgery. Post-operative follow-up ranged from 1.5 to 5.5 years. Immediate or delayed post-operative complications occurred in three dogs, including implant migration or loosening. Eight dogs showed long-term gait improvement, with resolution of incontinence if previously present. At 2-6 years post-surgery, four dogs were neurologically normal, three had mild residual ataxia, one had moderate ambulatory paraparesis, and one dog relapsed 3.5 years after surgery, resulting in severe paraparesis. Spinal segmental stabilisation techniques, with or without decompression, can result in satisfactory outcomes in small dogs with hemivertebrae and mild to moderate neurological signs. Further adaptations might be required to avoid implant loosening and allow continued growth in immature dogs.