Luc Van Ham

Agreement and repeatability of linear vertebral body and canal measurements using computed tomography (CT) and low field magnetic resonance imaging (MRI).

OBJECTIVE To evaluate agreement and repeatability of vertebral column measurements using computed tomography (CT) and magnetic resonance imaging (MRI). STUDY DESIGN Retrospective observational study. ANIMALS; Dogs (n=18) with disc associated wobbler syndrome; Dog cadavers (n=3). METHODS Five measurements of the 5th cervical vertebra were performed: vertebral body length (VBL), vertebral canal height (VCH), vertebral body height (VBH), vertebral canal width (VCW), and vertebral body width (VBW). Measurements were performed independently twice by 2 observers. Bland-Altman plots were created to evaluate agreement. Cadaveric vertebrae with soft tissue removed had the same variables and actual dimensions measured. RESULTS The largest discrepancy between CT and MRI measurement was for VBL (mean difference+/-SD=1.262 mm+/-1.245; P<.001), with the difference for all the other variables being acceptable. The 1st measurement was significantly higher than the 2nd only for VBL using CT (mean difference=0.476 mm+/-1.120; P=.009), with all other variables having acceptable differences. Mean difference for all measurements between 2 observers was small, except for VBL using CT (mean difference=0.762 mm+/-1.042; P<.001). Only the difference for VBL between CT and cadaver specimens was statistically significant. CONCLUSIONS Our results suggest high repeatability and good agreement for most vertebral measurements of interest. VBL measurement using CT was considered problematic. CLINICAL RELEVANCE Provided limitations are understood, linear measurements of vertebral dimensions from CT and MRI images can be used clinically.

The use of magnetic motor evoked potentials in horses with cervical spinal cord disease

The aim of this study was to investigate the use of magnetic motor evoked potentials as an ancillary diagnostic test in horses with cervical cord lesions. Transcranial magnetic stimulation was performed in 12 ataxic horses and the results of the evoked responses were compared to those found in normal horses. The latency and peak-to-peak amplitude of the potentials in the 12 ataxic horses were significantly different from those measured in normal horses. The configuration of the abnormal potentials was also polyphasic. Normalisation of the evoked potentials occurred in none of the horses, presented after a period of clinical improvement. These findings demonstrate that the technique is also able to detect lesions in horses with subtle clinical signs of incoordination. Magnetic transcranial stimulation is a valuable ancillary test to assess the integrity of the motor tracts. The technique is painless and safe and shows good sensitivity to detect lesions along the descending motor pathways.

Transcranial magnetic stimulation: normal values of magnetic motor evoked potentials in 84 normal horses and influence of height, weight, age and sex

REASONS FOR PERFORMING STUDY Cervical spinal cord dysfunction is a common problem in equine medicine and the currently available tests give no objective information about the functionality of the nervous tracts. Therefore, transcranial magnetic stimulation (TMS) was performed in 84 healthy horses of different height in order to have an objective measure for the integrity of the descending motor tracts in normal horses. OBJECTIVES To obtain reference values for onset latency and peak-to-peak amplitude of magnetic motor evoked potentials (MMEPs) and to evaluate the possible effect of height, age and gender on the neurophysiological measures. METHODS All horses were sedated and stimulated transcranially by using a magnetic coil placed on the forehead. The stimulator triggered the sweep of an electromyogram machine that recorded MMEPs bilaterally from needle electrodes in the extensor carpi radialis and cranial tibial muscles. In that way, it was possible to measure latency between stimulus and onset of response. RESULTS A significant difference was found between recordings made in the fore- and hindlimbs; MMEPs recorded in the front legs had a shorter onset latency and higher peak-to-peak amplitude. Mean +/- s.d. normal values for onset latency of 19.32 +/- 2.50 and 30.54 +/- 5.28 msecs and peak-to-peak amplitude values of 9.54 +/- 3.73 and 6.62 +/- 3.62 mV were obtained for extensor carpi radialis and cranial tibial muscles, respectively. The left-to-right difference in onset latency and peak-to-peak amplitude was not significant. In the same horse, differences up to 0.82 and 1.53 msecs for the extensor carpi radialis and cranial tibial muscles, respectively, lie within the 95% confidence limit and are considered normal. In contrast to onset latency, peak-to-peak amplitude showed a very large intra- and interindividual variability, even in the same muscle. To reduce the variability and predict normal values of new individual cases, influence of height, weight, age and sex on the MMEPs were determined. No significant effects of sex were observed on onset latency and peak-to-peak amplitude. The age of the horse had only a small but significant effect on peak-to-peak amplitude, with larger responses in older horses. Height at the withers and weight of the horse, parameters that strongly correlate with the size of the horse, had an important significant influence on onset latency but not on peak-to-peak amplitude. The age of the horse and height at the withers were used to predict peak-to-peak amplitude and onset latency, respectively, in normal horses. CONCLUSIONS AND POTENTIAL RELEVANCE TMS is an excellent addition to the few tools we have for noninvasive imaging of the equine nervous system. Magnetically evoked potentials are highly reproducible and recent advances suggest that the applications of TMS in horses will continue to grow rapidly.

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.

Evolution of clinical signs and predictors of outcome after conservative medical treatment for disk-associated cervical spondylomyelopathy in dogs.

OBJECTIVE To evaluate the evolution of clinical signs and their correlation with results of magnetic resonance imaging (MRI) and transcranial magnetic stimulation (TMS) and to assess potential prognostic variables after conservative medical treatment for disk-associated cervical spondylomyelopathy (DA-CSM) in dogs. DESIGN Prospective cohort study. ANIMALS 21 client-owned dogs with DA-CSM. PROCEDURES After neurologic grading, dogs underwent low-field MRI and TMS with measurement of onset latencies and peak-to-peak amplitudes from the extensor carpi radialis and cranial tibial muscles. Dimensions calculated from MRI images were remaining spinal cord area, spinal cord compression ratio, vertebral occupying ratio, vertebral canal height-to-body height ratio, vertebral canal height-to-body length ratio, and vertebral canal compromise ratio. Intraparenchymal signal intensity changes were graded. Dogs were reevaluated 1, 3, 6, 12, and 24 months after initial diagnosis. RESULTS Outcome was successful in 8 of 21 dogs. Negative outcomes were characterized by rapid progression of clinical signs. All dogs with more severe clinical signs of DA-CSM 1 month after diagnosis had unsuccessful outcomes. Outcome was associated with the remaining spinal cord area and vertebral canal compromise ratio. Prognosis was not associated with severity of clinical signs or results of TMS. There were no significant correlations among clinical signs, MRI findings, and TMS results. CONCLUSIONS AND CLINICAL RELEVANCE Conservative medical treatment of DA-CSM was associated with a guarded prognosis. Selected MRI variables and clinical evolution 1 month after diagnosis can be considered prognostic indicators. The lack of correlation among clinical signs, results of diagnostic imaging, and results of electrophysiologic evaluation in dogs with DA-CSM warrants further investigation.

Non-pharmacological treatment options for refractory epilepsy: An overview of human treatment modalities and their potential utility in dogs

Refractory epilepsy is a common disorder both in humans and dogs and treatment protocols are difficult to optimise. In humans, different non-pharmacological treatment modalities currently available include surgery, the ketogenic diet and neurostimulation. Surgery leads to freedom from seizures in 50-75% of patients, but requires strict patient selection. The ketogenic diet is indicated in severe childhood epilepsies, but efficacy is limited and long-term compliance can be problematic. In the past decade, various types of neurostimulation have emerged as promising treatment modalities for humans with refractory epilepsy. Currently, none of these treatment options are used in routine daily clinical practice to treat dogs with the condition. Since many dogs with poorly controlled seizures do not survive, the search for alternative treatment options for canine refractory epilepsy should be prioritised. This review provides an overview of non-pharmacological treatment options for human refractory epilepsy. The current knowledge and limitations of these treatments in canine refractory epilepsy is also discussed.

Radiographic vertebral canal and vertebral body ratios in Doberman Pinschers with and without clinical signs of caudal cervical spondylomyelopathy

OBJECTIVE To determine radiographic vertebral ratio values representing vertebral canal stenosis in Doberman Pinschers with and without clinical signs of caudal cervical spondylomyelopathy (CCSM). ANIMALS Doberman Pinschers with (n = 81) and without (39) signs of CCSM. PROCEDURES All dogs underwent lateral survey radiography of the cervical vertebral column. Five specific measurements were made at C3 through C7, and from those data, 3 ratios were calculated and analyzed for use in diagnosis of CSSM: canal height-to-vertebral body height ratio (CBHR), canal height-to-vertebral body length ratio (CBLR), and caudal vertebral canal height-to-cranial vertebral canal height ratio (CCHR). The CBHR and CBLR were considered indicators of vertebral canal stenosis, and CCHR described vertebral canal shape. RESULTS Compared with Doberman Pinschers without CCSM, mean CBHR and CBLR values were significantly smaller for Doberman Pinschers with CCSM; for CBHR, this difference was evident at each assessed vertebra. The CCHR value for C7 was significantly larger in dogs with CCSM. Receiver operating characteristic statistics did not identify a threshold point that had combined high sensitivity and specificity sufficient to differentiate between Doberman Pinschers with and without CCSM. CONCLUSIONS AND CLINICAL RELEVANCE Doberman Pinschers with CCSM had vertebral canal stenosis combined with a funnel-shaped vertebral canal at C7 significantly more often than did Doberman Pinschers without CCSM. Despite these significant differences, no reliable threshold ratio values were identified to differentiate groups of dogs.

Surgical Treatment of a Canine Intranasal Meningoencephalocele

OBJECTIVE To report the clinical signs, diagnosis, and surgical treatment of an intranasal meningoencephalocele in a dog. STUDY DESIGN Case report. ANIMAL Female Border collie, 5 months old. METHODS A right intranasal meningoencephalocele was identified by computed tomography and magnetic resonance imaging. RESULTS The lesion was approached by a modified transfrontal craniotomy. Surgical closure of the defect at the level of the cribriform plate and removal of extruded brain tissue resulted in regression of lacrimation and coincided with absence of seizuring. Treatment with phenobarbital was gradually reduced and stopped at 7 months after surgery. At 28 months the dog remained free of seizures. CONCLUSION Meningoencephalocele, although rare, can cause seizures in dogs and can be treated surgically. CLINICAL RELEVANCE A transfrontal craniotomy with excision of the meningoencephalocele and closure of the defect can be an effective treatment for an intranasal meningoencephalocele in dogs.

The influence of sex hormones on seizures in dogs and humans.

Epilepsy is the most common chronic neurological disorder in both humans and dogs. The effect of sex hormones on seizures is well documented in human medicine. Catamenial epilepsy is defined as an increase in frequency and severity of seizures during certain periods of the menstrual cycle. Oestradiol increases seizure activity and progesterone is believed to exhibit a protective effect. The role of androgens is controversial and there is a lack of research focusing on androgens and epilepsy. Indeed, little is known about the influence of sex hormones on epilepsy in dogs. Sterilisation is believed to improve seizure control, but no systematic research has been conducted in this field. This review provides an overview of the current literature on the influence of sex hormones on seizures in humans. The literature on idiopathic epilepsy in dogs was assessed to identify potential risk factors related to sex and sterilisation status. In general, there appears to be an over-representation of male dogs with idiopathic epilepsy but no explanation for this difference in prevalence between sexes has been reported. In addition, no reliable conclusions can be drawn on the effect of sterilisation due to the lack of focused research and robust scientific evidence.

Idiopathic head tremor in English bulldogs.

Idiopathic head tremor (IHT) syndrome is a recognized but poorly characterized movement disorder in English bulldogs (EBs). The data analyzed were collected via a detailed online questionnaire and video recordings. Thirty‐eight percent of the population demonstrated IHT. The first presentation was early in life. There was no sex or neutered status predisposition. The condition disappeared with time in 50% of the cases. The direction of the head movement was vertical or horizontal. The number of episodes per day and the duration of the episodes were greatly variable. The majority of episodes occurred at rest. Most of the episodes were unpredictable. And there was no alteration of the mental status for most dogs during the episodes. Stress has been reported as a suspected trigger factor. IHT in EBs can be considered an idiopathic paroxysmal movement disorder.