The neurology of balance: Function and dysfunction of the vestibular system in dogs and cats

The Spontaneous Incidence of Neurological Clinical Signs in Preclinical Species Using Cage-side Observations or High-definition Video Monitoring: A Retrospective Analysis

When conducting toxicology studies, the interpretation of drug-related neurological clinical signs such as convulsions, myoclonus/myoclonic jerks, tremors, ataxia, and salivation requires an understanding of the spontaneous incidence of those observations in commonly used laboratory animal species. The spontaneous incidence of central nervous system clinical signs in control animals from a single facility using cage-side observations or high definition video monitoring was retrospectively analyzed. Spontaneous convulsions were observed at low incidence in Beagle dogs and Sprague-Dawley rats but were not identified in cynomolgus monkeys and Göttingen minipigs. Spontaneous myoclonic jerks and muscle twitches were observed at low incidence in Beagle dogs, cynomolgus monkeys, and Sprague-Dawley rats but were not seen in Göttingen minipigs. Spontaneous ataxia/incoordination was identified in all species and generally with a higher incidence when using video monitoring. Salivation and tremors were the two most frequent spontaneous clinical signs and both were observed in all species. Data from the current study unveil potential limitations when using control data obtained from a single study for toxicology interpretation related to low incidence neurological clinical signs while providing historical control data from Beagle dogs, cynomolgus monkeys, Sprague-Dawley rats, and Göttingen minipigs.

Current definition, diagnosis, and treatment of canine and feline idiopathic vestibular syndrome

Idiopathic vestibular syndrome (IVS) is one of the most common neurological disorders in veterinary medicine. However, its diagnosis and treatment varies between publications. The aim of the current study was to gather experts' opinion about IVS definition, diagnosis, and treatment. An online-survey was used to assess neurology specialists' opinion about the definition, diagnosis and treatment of IVS. The study demonstrated that the definition, diagnosis, and treatment of IVS are largely consistent worldwide, with the EU prioritising less frequently advanced imaging and more often otoscopy to rule out other diseases. IVS was defined by most specialists as an acute to peracute, improving, non-painful peripheral vestibular disorder that often affects cats of any age and geriatric dogs. Regarding diagnosis, a detailed neurological examination and comprehensive blood tests, including thyroid values, blood pressure, and otoscopic examination, was seen as crucial. A thorough workup may also involve MRI and CSF analysis to rule out other causes of vestibular dysfunction. Treatment of IVS typically involved intravenous fluid therapy and the use of an antiemetic, with maropitant once daily being the preferred choice among specialists. Antinausea treatment was considered, however, only by a handful specialists. This survey-based study provides valuable insights from neurology experts and highlights areas that require further research to bridge the gap between theory and practice.

The value of vestibular graviceptive pathway evaluation in the diagnosis of unilateral peripheral vestibular dysfunction

BACKGROUND

Evaluation of vestibular graviceptive pathway (VGP) in patients with unilateral peripheral vestibular dysfunction (UPVD) has received increasing attention from researchers. The study aimed to investigate the value of VGP evaluation in the diagnosis of UPVD.

METHODS

Ninety-five UPVD patients were divided into attack and remission phase groups. VGP evaluation-related indicators, including subjective visual vertical (SVV), subjective visual horizontal (SVH), head tilt, ocular torsion (OT), and skew deviation (SD), were measured, and their correlations with cochleovestibular function test results were analyzed. The possible etiologies of contralesional VGP (c-VGP) were analyzed.

RESULTS

Positive rates of SVV, SVH, OT, and SD were significantly higher, and the degrees of SVV, SVH, and OT were significantly greater in the attack phase group than the remission phase group. The sides with abnormal VGP evaluation results were correlated with the sides with hearing loss, abnormal caloric, and video head impulse test (vHIT) results. A total of 14 patients showed c-VGP, and possible etiologies included contralateral benign paroxysmal positional vertigo (n = 4), bilateral hearing loss (n = 8), bilateral vHIT gain reduction (n = 1), autoimmune diseases (n = 6), vascular risk factors (n = 6), lacunar infarction (n = 3), and endolymphatic hydrops (n = 3).

CONCLUSIONS

Alterations in SVV, SVH, OT, and SD were noted in UPVD patients in different phases, which are presumed to be related to dynamic vestibular compensation; correlations between VGP evaluation results and cochleovestibular function test results indicate that VGP evaluation may be helpful for the diagnosis of the side affected in UPVD; the presence of c-VGP may be related to bilateral labyrinth lesions or endolymphatic hydrops on the affected side; and the involvement of autoimmune mechanisms also deserves attention.

The Reibergram for immunoglobulin A in dogs: Evaluation of intrathecal IgA synthesis using a quotient graph in dogs with neurological diseases

BACKGROUND

Increased cerebrospinal fluid (CSF) protein concentration is a common finding in neurological diseases of dogs. Distinguishing between intrathecally-produced proteins and proteins that have passed the blood-CSF barrier because of barrier disruption facilitates diagnosis. Albumin is a microprotein mainly produced extrathecally that can be used as a reference marker for blood-CSF barrier dysfunction.

OBJECTIVES

Develop a quotient graph based on the CSF/serum quotient of albumin and immunoglobulin A (IgA; Reibergram) to visualize intrathecal IgA synthesis and blood-CSF barrier dysfunction.

ANIMALS AND METHODS

Retrospective single-center cohort study. A hyperbolic function was developed using data from 6 healthy Beagles and 38 dogs with neurological diseases in which an isolated blood-CSF barrier dysfunction was expected. The function was validated using data from 10 dogs with expected intrathecal IgA synthesis and was visualized as a quotient graph. Finally, the graph was used to evaluate data of 118 dogs with various neurological diseases.

RESULTS

Within the Reibergram, the function QLim IgA = 0.13 QAlb 2 + 11.9 · 10 - 6 - 1.01 · 10 - 3 describes the upper values of physiological IgA quotients. It detects diseases with expected intrathecal IgA synthesis with higher sensitivity (85%) and specificity (89%) than the IgA index. The upper value of the physiological albumin quotient is 2.22 and detects diseases with expected blood-CSF barrier dysfunction (sensitivity: 81%; specificity: 88%).

CONCLUSION AND CLINICAL IMPORTANCE

The canine Reibergram can detect blood-CSF barrier dysfunction and intrathecal IgA synthesis in the majority of cases. The graphical visualization simplifies data evaluation and makes it a feasible tool in routine CSF diagnostic testing.

Ondansetron in dogs with nausea associated with vestibular disease: A double-blinded, randomized placebo-controlled crossover study

Background

Nausea and emesis can be, among other signs, common manifestations of acute vestibular system dysfunction in dogs. Currently, antiemetic drugs, such as maropitant and metoclopramide, are used commonly, but do not appear to control nausea. A non‐placebo‐controlled preliminary study suggested good efficacy of 5‐HT3‐receptor antagonists, such as ondansetron, against nausea in dogs with vestibular syndrome.

Objectives

To assess and confirm the effect of ondansetron on behavior suggestive of nausea in dogs with vestibular syndrome.

Animals

Fourteen dogs with vestibular syndrome and clinical signs of nausea presented to a neurology service.

Methods

Placebo‐controlled, double‐blinded, crossover study. Behavioral assessment was performed hourly for 4 hours using an established numerical rating scale. The criteria salivation, lip licking, vocalization, restlessness, lethargy, and general nausea were scored. The occurrence of emesis was recorded. After scoring at T0 (pre‐dose) and T2 (2 hours post‐dose) either ondansetron (0.5 mg/kg) or placebo was injected IV. Two hours post‐dose, treatments were switched. Blood samples were collected to measure serum arginine vasopressin (AVP) concentration, which previously has been shown to correlate with clinical signs of nausea.

Results

Clinical resolution of nausea was observed 1 hour after administration of ondansetron, whereas serum AVP concentration decreased 4 hours after ondansetron administration.

Conclusion and Clinical Importance

Administration of ondansetron IV is beneficial for dogs with nausea secondary to acute vestibular syndrome. Ondansetron substantially and rapidly decreased clinical signs of nausea behavior and stopped emesis.

Vestibular Disease

The vestibular system (VS) is the primary specialized sensory system responsible for maintaining balance (equilibrium) and orientation of the eyes, neck, trunk, and limbs during rest and movement. Two important reflexes are responsible for maintaining balance: vestibulo-ocular and vestibulospinal reflexes. These reflexes involve peripheral and central components of the VS. Whether central or peripheral disease, most of the disorders of the VS result in ipsilateral neurologic deficits. A few uncommon exceptions present with contralateral signs to the site of the lesion. This article provides a brief review of functional anatomy, vestibular disease, clinical signs, and examples of disorders affecting the VS.

Unilateral Laryngeal Paralysis Secondary to Otitis Media/Interna in Two Cats

Two adult cats were presented for coughing, gagging, dysphonia, exaggerated swallowing attempts, unilateral vestibular dysfunction, and/or Horner syndrome. In both cats, unilateral laryngeal paralysis was identified on the side ipsilateral to other neurological deficits. Cross-sectional imaging was consistent with otitis media/interna. In both cats, there also was extensive cellulitis surrounding the tympanic bulla and dissecting through tissue planes to involve the opening of the tympano-occipital fissure on the side ipsilateral to the laryngeal paralysis. Laryngeal paralysis was presumed secondary to involvement of the vagus nerve as it emerged from the tympano-occipital fissure. Antibiotic therapy resulted in resolution of clinical signs in both cats and restored laryngeal function as evidenced by visual examination of the larynx in one cat.

Changes in Health Indicators of Welfare in Group-Housed Shelter Cats

The aim of this study was to detect changes in health-oriented welfare indicators of shelter cats housed in a shelter by means of long-term monitoring of health indicators of welfare in a population of group-housed cats in a private, no-kill shelter in the Czech Republic. The cat population housed in a large group was monitored for 1 year. The data recording took place at 2-week intervals. A total of 220 cats were evaluated using a protocol containing eight health-oriented welfare indicators: body condition, third eye visibility, eye discharge, eye irritation, nose discharge, the presence of pathologically induced respiratory sounds, coat condition, and lameness and abnormal posture. The assessment was performed based on the observation by two trained evaluators. The cats' condition was rated on a 5-point scale for each indicator, where the optimal condition was represented by the score of 1 and a severe deterioration by the score of 5 for the given indicator, except for the body condition indicator, where the optimal condition was represented by the score of 3. A deterioration in the score in at least one of the indicators during the stay in the shelter was recorded in 52 (41.6%) of 125 cats that were assessed at least twice. The effect of the LOS, sex and age on the scores for each health indicator was examined via a linear mixed model analysis, as this method allows for handling of dependencies in the data of repeated measurements. The effect of predictors on the third eye visibility scores was not found. The age of cats predicted the coat condition and body condition scores. The LOS predicted scores of the abnormal posture and lameness indicator and scores of a composite index composed of indicators related to upper respiratory tract disease. The results suggest that despite the fact that some improvement of health was documented during the cats' stay in the shelter, there were a non-negligible number of animals experiencing a permanent or long-term deterioration in health. Efforts to minimize the undesirable factors contributing to the deterioration of well-being of cats during their stay in a shelter should be made.

Unilateral decrease in inner ear signal in fluid-attenuated inversion recovery sequences in previously suspected canine idiopathic vestibular syndrome

The aetiology of canine idiopathic vestibular syndrome (IVS) remains unclear. In human medicine, characteristic magnetic resonance imaging (MRI) techniques are used to demonstrate differences in endolymph composition between affected and unaffected inner ears. The purpose of this study was to determine whether similar MRI techniques could help to detect changes in the inner ears of canine IVS patients. Medical records from two veterinary referral clinics were reviewed retrospectively. Dogs were included if they had a diagnosis of IVS, obvious lateralisation of clinical signs, and an MRI of the vestibular system. A region of interest (ROI) was manually outlined by defining the anatomical area of the inner ear in T2-weighted and fluid-attenuated inversion recovery (FLAIR) images. In order to calculate the ratio of FLAIR suppression of each ear, the mean grey value of the ROI was determined in both sequences. If a unilateral decrease in suppression was identified, it was compared with the direction of clinical signs. In total, 80 dogs were included in the study. There was a significantly lower degree of suppression on the affected compared to the unaffected side (0.8886 vs. 0.9348, respectively; P = 0.0021). In 92.5% of cases, there was agreement between the most suppressed side on MRI and the direction of clinical signs. This study provides preliminary evidence about the appearance of endolymph on MRI of dogs with IVS. Further studies are needed to investigate associations between the severity of MRI changes and prognosis.

Clinical reasoning in feline vestibular syndrome: which presenting features are the most important?

OBJECTIVES

The aim of this study was to evaluate whether clinical variables from the history, clinical presentation, and physical and neurological examinations of cats with vestibular syndrome were statistically predictive of the underlying diagnosis.

METHODS

In total, 174 cats presenting with vestibular syndrome between January 2010 and May 2019 were investigated. Univariate statistical analysis of clinical variables was performed and those statistically associated with a diagnosis were retained for multivariable binary logistic regression modelling.

RESULTS

The seven most prevalent diagnoses represented 95% of vestibular presentations, which included: otitis media/interna (n = 48), idiopathic vestibular syndrome (n = 39), intracranial neoplasia (n = 24), middle ear polyp (n = 17), feline infectious peritonitis (n = 13), thiamine deficiency (n = 13) and intracranial empyema (n = 11). Idiopathic vestibular syndrome was commonly associated with non-purebred cats and had 17.8 times the odds of an improving clinical progression (95% confidence interval [CI] 1.3-250.0; P = 0.03). Intracranial neoplasia was associated with older age and chronic onset of clinical signs, and was significantly more likely to have a central vestibular neuroanatomical localisation (95% CI 8.5-344,349,142.0; P = 0.015) with postural deficits on neurological examination. Thiamine deficiency was more common in female cats, with 52.6 times the odds of a waxing and waning clinical progression (95% CI 1.2-1000; P = 0.038) and 6.8 times the odds of presenting with bilateral vestibular signs (95% CI 1.0-45.7; P = 0.047) and wide excursions of the head (95% CI 1.0-45.7; P = 0.047). Middle ear polyps were associated with 8.8 times the odds of presenting with Horner syndrome (95% CI 1.5-50.0; P = 0.015).

CONCLUSIONS AND RELEVANCE

Although it may be difficult to identify the underlying diagnosis in cats with vestibular syndrome from the presenting features alone, there are instances in which discrete clinical features may help to guide clinical reasoning when evaluating cats with vestibular presentations.

The use of ondansetron for the treatment of nausea in dogs with vestibular syndrome

Background

Vestibular syndrome is often accompanied by nausea. Drugs currently approved for its treatment have been developed to stop vomiting but not nausea. The efficacy of 5-HT₃ receptor antagonists to reduce nausea has been described for chemotherapy, but not for nausea secondary to vestibular disorders.

Methods

Sixteen dogs with vestibular syndrome-associated nausea were included in the open-label, multicentre study. The intensity of nausea-like behaviour was analysed before ondansetron administration (0.5 mg/kg i.v.) and 2 h afterwards, using a validated 5-point-scale. The occurrence and frequency of salivation, lip licking, restlessness, vocalisation, lethargy, and vomiting were assessed.

Results

All dogs initially showed signs of nausea, whereas only 31% showed vomitus. The intensity of nausea was significantly reduced in all dogs (p ≤ 0.0001) 2 h after ondansetron administration, including the clinical signs of nausea analysed in 11 dogs (salivation [p = 0.0078], lip licking [p = 0.0078], restlessness [p = 0.0039], and lethargy [p = 0.0078]) except for vocalisation (p > 0.9999).

Conclusions

The results provide preliminary evidence of the potential benefit of ondansetron in the treatment of nausea, which was present in all examined dogs. Vomiting was only observed in 5 dogs indicating that nausea can occur separately and should not be perceived only as a preceding stimulation of the vomiting centre.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-021-02931-9.

Cerebrospinal fluid analysis lacks diagnostic specificity in dogs with vestibular disease

BACKGROUND

Although, vestibular syndrome is a common neurological presentation, little is known about the diagnostic value of cerebrospinal fluid (CSF) analysis in vestibular syndrome in dogs.

METHODS

Medical records were retrospectively reviewed, and dogs with vestibular disease that had undergone magnetic resonance imaging of the head, CSF analysis and were diagnosed with central or peripheral vestibular syndrome were included. Disorders affecting the central vestibular system included meningoencephalitis of unknown origin (MUO), brain neoplasia, ischaemic infarct, intracranial empyema or metronidazole toxicity. Disorders affecting the peripheral vestibular system included idiopathic vestibular disease, otitis media/interna or neoplasia affecting the inner ear structures. Total nucleated cell concentration (TNCC), total protein concentration (TP) and cytologic assessment were recorded.

RESULTS

A total of 102 dogs met the inclusion criteria. The sensitivity and specificity of increased CSF TNCC to differentiate central from peripheral vestibular syndrome was 49% and 90%, while the sensitivity and specificity of increased TP was 58% and 39%, respectively. The TNCC and TP in dogs with MUO were significantly higher than in dogs with idiopathic vestibular disease (p = 0.000 and p = 0.004). MUO was associated with lymphocytic pleocytosis, while idiopathic vestibular disease and ischaemic infarct were associated with the presence of activated macrophages or normal cytology (p = 0.000).

CONCLUSION

Although consistent CSF abnormalities were observed in dogs with MUO, CSF analysis did not allow reliable differentiation between central and peripheral vestibular syndrome. CSF analysis is not reliable as the sole diagnostic technique in dogs with vestibular disease.

Clinical reasoning in canine vestibular syndrome: Which presenting factors are important?

BACKGROUND

Although the use of clinical reasoning has been evaluated for several neurological presentations, this approach has not yet been investigated for dogs with vestibular syndrome.

METHODS

Two hundred and thirty-nine dogs presenting with vestibular syndrome were included in this retrospective study. Univariate analysis of variables (clinical history, signalment, clinical presentation and neurological examination findings) was performed. Variables with p < 0.3 were selected for logistic regression.

RESULTS

Ninety-five percent of dogs were represented by eight conditions: idiopathic vestibular disease (n = 78 dogs), otitis media interna (n = 54), meningoencephalitis of unknown origin (n = 35), brain neoplasia (n = 26), ischaemic infarct (n = 25), intracranial empyema (n = 4), metronidazole toxicity (n = 3) and neoplasia affecting the middle ear (n = 3). Idiopathic vestibular disease was associated with higher age, higher bodyweight, improving clinical signs, pathological nystagmus, facial nerve paresis, absence of Horner's syndrome and a peripheral localisation. Otitis media interna was associated with younger age, male gender, Horner's syndrome, a peripheral localisation and a history of otitis externa. Ischaemic infarct was associated with older age, peracute onset of signs, absence of strabismus and a central localisation.

CONCLUSIONS

Discrete clinical features can be used to identify the most likely diagnosis in dogs with vestibular syndrome.

Vestibular disease in dogs under UK primary veterinary care: Epidemiology and clinical management

BACKGROUND

Vestibular disease (VD), central or peripheral, can be a dramatic primary-care presentation. Current literature describes mostly dogs examined in referral centers.

HYPOTHESIS/OBJECTIVES

Describe the prevalence, presentation, clinical management, and outcomes of VD in dogs under primary veterinary care at UK practices participating in VetCompass.

ANIMALS

Seven hundred and fifty-nine vestibular cases identified out of 905 544 study dogs.

METHODS

Retrospective cohort study. Potential VD cases clinically examined during 2016 were verified by reviewing clinical records for signalment, presenting clinical signs, treatments, and outcomes. Multivariable logistic regression was used to evaluate factors associated with VD.

RESULTS

The overall prevalence of VD was 8 per 10 000 dogs (95% CI = 7-9). Median age at first diagnosis was 12.68 years (interquartile range [IQR], 11.28-14.64). Compared with crossbreeds, breeds with the highest odds of VD diagnosis included French Bulldogs (odds ratio [OR] = 9.25, 95% CI = 4.81-17.76, P < .001), Bulldogs (OR = 6.53, 95% CI = 2.66-16.15, P < .001), King Charles Spaniels (OR = 4.96, 95% CI = 2.52-9.78, P < .001), Cavalier King Charles Spaniels (OR = 3.56, 95% CI = 2.50-5.06, P < .001), and Springer Spaniels (OR = 3.37, 95% CI = 2.52-4.52, P < .001). The most common presenting signs were head tilt (69.8%), nystagmus (68.1%), and ataxia (64.5%). The most frequently used treatments were antiemetics (43.2%), systemic glucocorticoids (33.1%), antimicrobials (25%), and propentofylline (23.25%). There were 3.6% of cases referred. Improvement was recorded in 41.8% cases after a median of 4 days (IQR, 2-10.25).

CONCLUSIONS

Our study identifies strong breed predispositions for VD. The low referral rates suggest that primary-care data sources offer more generalizable information for benchmarking to help clinicians review their own clinical activities.

MRI utricle diameter asymmetry is significantly greater in dogs with idiopathic vestibular syndrome compared with unaffected dogs

Idiopathic vestibular syndrome (IVS) is the most common cause of acute unilateral peripheral vestibular dysfunction in older dogs. The purpose of this retrospective, cross-sectional study was to characterize morphological changes in the utricle of dogs affected by IVS, using MRI. To evaluate differences between affected and unaffected utricles, the ratio of the largest to the smallest utricle diameter was obtained, as measured on transverse T2-weighted images, and defined as the utricle asymmetricity ratio (UAR). Out of 137 patients diagnosed with IVS after excluding other vestibular diseases by MRI, 101 were eligible for inclusion. Additionally, 31 older dogs with no signs of vestibular disorders or other intracranial diseases were included as a control group. The disease group was divided into two subgroups in which the direction of head tilt and nystagmus symptoms versus the decreased utricle diameters were consistent or inconsistent. The medians of UARs of the IVS and control groups were 0.83 (range 0.37-1.00) and 0.98 (0.70-1.00), respectively. The medians of the UARs of the consistent and inconsistent IVS subgroups were 0.82 (0.37-0.99) and 0.90 (0.74-1.00), respectively. The UAR of the IVS group was significantly decreased than that of the control group and UAR of the consistent sub-group was significantly decreased than that of the inconsistent sub-group (P < .01). In conclusion, significant asymmetry of utricle diameter was identified in dogs with IVS versus unaffected dogs. We propose that canine IVS may possibly be correlated with structural atrophy of the vestibular system.

Inner ear fluid-attenuated inversion recovery MRI signal intensity in dogs with vestibular disease

The inner ear contains endolymph and perilymph. The second is comparable and in continuity with the cerebrospinal fluid (CSF) so it is expected to suppress in fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI) if normal. Even though inner ear FLAIR abnormalities have been extensively described in humans with inner ear disease, its diagnostic value in dogs is yet to be proven. The goal of this retrospective cohort study was to investigate the diagnostic utility of FLAIR MRI in dogs with vestibular disease. A review of medical records identified 101 dogs that had brain MRI performed because of vestibular signs. Based on the final diagnosis, patients were allocated to three groups: otitis media/interna, idiopathic vestibular disease, and central vestibular disease. Additionally, a control group (n = 73) included dogs with normal MRI and without vestibular signs. Inner ears were delineated using a region of interest, and signal intensity was measured in FLAIR and T2-weighted images. The percentages of suppression in FLAIR were calculated and compared between affected and unaffected sides of each individual and between groups using a general linear mixed model. Correlation between suppression and CSF cell count and protein concentration was assessed. Affected inner ears in dogs with otitis media/interna had decreased suppression in FLAIR compared to the unaffected side (P < .001), and all other groups (P < .01). No significant correlation was detected between CSF results and suppression. These results show the diagnostic value of FLAIR in otitis media/interna due to lack of suppression in the affected inner ear.

Clinical signs, MRI findings and outcome in dogs with peripheral vestibular disease: a retrospective study

BACKGROUND

Vestibular dysfunction is relatively common in dogs, with a prevalence of 0.08% reported in primary veterinary care in the UK. There are several studies investigating how to differentiate between peripheral and central vestibular disease but only limited information regarding the possible underlying causes for peripheral vestibular dysfunction in dogs. This study therefore aimed to describe the clinical signs, magnetic resonance imaging findings (MRI), underlying causes and outcome in a large population of dogs diagnosed with peripheral vestibular disease.

RESULTS

One hundred eighty-eight patients were included in the study with a median age of 6.9 years (range 3 months to 14.6 years). Neurological abnormalities included head tilt (n = 185), ataxia (n = 123), facial paralysis (n = 103), nystagmus (n = 97), positional strabismus (n = 93) and Horner syndrome (n = 7). The most prevalent diagnosis was idiopathic vestibular disease (n = 128), followed by otitis media and/or interna (n = 49), hypothyroidism (n = 7), suspected congenital vestibular disease (n = 2), neoplasia (n = 1) and cholesteatoma (n = 1). Long-term follow-up revealed persistence of head tilt (n = 50), facial paresis (n = 41) and ataxia (n = 6) in some cases. Recurrence of clinical signs was observed in 26 dogs. Increasing age was associated with a mild increased chance of diagnosis of idiopathic vestibular syndrome rather than otitis media and/or interna (P = 0.022, OR = 0.866; CI 0.765-0.980). History of previous vestibular episodes (P = 0.017, OR = 3.533; CI 1.251-9.981) was associated with an increased likelihood of resolution of the clinical signs whilst contrast enhancement of cranial nerves VII and/or VIII on MRI (P = 0.018, OR = 0.432; CI 0.251-0.868) was associated with a decreased chance of resolution of the clinical signs.

CONCLUSIONS

Idiopathic vestibular disease is the most common cause of peripheral vestibular dysfunction in dogs and it is associated with advanced age. Incomplete recovery from peripheral vestibular disease is common, especially in dogs presenting with cranial nerve enhancement on MRI but less so if there is previous history of vestibular episodes.

Subcellular Abnormalities of Vestibular Nerve Morphology in Patients With Intractable Meniere's Disease

Objective: Few studies so far have focused on the retrocochlear lesions in Meniere's disease (MD). This study aims to investigate pathological alterations in the central portion of the vestibular nerve (VN) in patients with intractable Meniere's disease (MD) and to explore retrocochlear lesions and their relationship with disease severity. Methods: Eight MD patients with refractory vertigo received vestibular neurectomy via a retrosigmoid or translabyrinthine approach. Segments of VN were carefully removed and immediately fixed for histopathological examination. Five VN specimens were examined by light microscopy after hematoxylin/eosin staining; three specimens were extensively analyzed using transmission electron microscopy, to identify VN ultrastructural lesions. Correlations between lesions and patient clinical characteristics were examined. Results: Histopathological examination revealed evidence of various types of chronic VN impairment, including the formation of corpora amylacea (CA), axon atrophy, and severe damage to the myelin sheath. Electron microscopy revealed membranous whorls within dilated Schmidt-Lanterman incisures, the formation of myeloid bodies, dysmyelination, and demyelination. Unexpectedly, we observed a positive correlation between the density of CA in VN tissue and the duration of disease, as well as the degree of hearing impairment, independent of age. Conclusion: Our findings indicate that deformation of subcellular organelles in the central portion of the VN is one of the key pathological indicators for the progressive severity and intractability of vertigo and support a vestibular nerve degeneration.

Saccadic oscillations in 4 dogs and 1 cat

Disorders affecting the control of saccadic eye movements result in involuntary saccadic oscillations and are widely reported in human medicine. Information regarding the occurrence and potential importance of saccadic oscillations in veterinary medicine is currently limited. The clinical histories of three dogs and one cat displaying involuntary eye movements consistent with opsoclonus are presented, with final diagnoses including idiopathic generalized tremor syndrome and neuronal ceroid lipofuscinosis (NCL). A dog with eye movements closely resembling macrosaccadic oscillations is also presented, for which a final diagnosis of NCL was made. All animals had clinical signs of cerebellar disease. As in human medicine, recognition of these forms of involuntary eye movement might suggest a cerebellar neuroanatomic localization. Opsoclonus and macrosaccadic oscillations are forms of involuntary saccadic eye movement that are both unrecognized and under-reported in veterinary medicine.

Congenital Peripheral Vestibular Syndrome in a Domestic Ferret (Mustela putorius furo)

A 3-month-old intact female ferret (Mustela putorius furo) was presented with a 2-month history of ataxia. On physical examination, the ferret had difficulty standing upright. During the neurologic examination, the patient had a left head tilt and positional strabismus, circled to the left, and was ataxic. Results of the complete blood count were consistent with a mild normocytic normochromic anemia. Initial treatment was supportive. Magnetic resonance imaging was performed and revealed an asymmetry of the inner ears. A brainstem auditory evoked response test was also performed. History, clinical signs, and diagnostic test results indicated that the ferret was suffering from congenital peripheral vestibular syndrome and left-sided deafness. Congenital disease should be considered in the differential diagnosis of young ferrets with peripheral vestibular syndrome. Supportive care and physiotherapy can improve balance and motor function, leading to an acceptable quality of life.

Proposed treatment for geriatric vestibular disease in dogs

Sudden-onset vestibular dysfunction in the canine is a commonly seen condition in veterinary practice, with some veterinarians reporting several cases each month. However, traditional veterinary medicine has little to offer these patients other than symptomatic relief for the severe nausea that accompanies the vertigo and supportive advice for the owners. Owners of affected dogs are informed that these symptoms usually resolve within a few days. As physical therapists, we often see cases of benign paroxysmal positional vertigo in our human practice clinics, and effective protocols for diagnosis and treatment of the condition have been developed for this condition. A modified testing and repositioning postural maneuver used successfully on 12 canine patients in our canine rehabilitation clinic (The Canine Fitness Centre, Calgary, Alberta, Canada) is hereby described.

Brainstem auditory evoked potentials in healthy cats recorded with surface electrodes

The aim of this study was to evaluate the brainstem auditory evoked potentials of seven healthy cats, using surface electrodes. Latencies of waves I, III and V, and intervals I–III, I–V and III–V were recorded. Monaural and binaural stimulation of the cats were done with sounds ranging between 40 and 90 decibel Sound Pressure Level. All latencies were lower than those described in previous studies, where needle electrodes were used. In the case of binaural stimulation, latencies of waves III and V were greater compared to those obtained for monaural stimulation (P < 0.01), and relatively unchanged for wave I (P > 0.05). Regardless of the sound intensity, the interwave latency was constant (P > 0.05). Interestingly, no differences were noticed for latencies of waves III and V when sound intensity was higher than 80dB SPL. This study completes the knowledge in the field of electrophysiology and shows that the brainstem auditory evoked potentials in cats using surface electrodes is a viable method to record the transmission of auditory information. That can be faithfully used in clinical practice, when small changes of latency values may be an objective factor in health status evaluation.

Cholesteatoma after lateral bulla osteotomy in two brachycephalic dogs

This report describes a French bulldog and a pug that presented to the authors' hospital following total ear canal ablation (TECA) and lateral bulla osteotomy (LBO), with signs of recurring otitis media and difficulty opening their mouths. The bulldog also had unilateral facial paralysis and sensory deficits of the trigeminal nerve on the ipsilateral side. Computed tomography and MRI scans suggested cholesteatoma in the bulldog, but showed only slight enlargement of the bulla in the pug. Histopathologic examination of samples yielded cholesteatoma in both cases. The authors suspect that development of the cholesteatomas was linked to the TECA/LBO surgery in both cases. Cholesteatomas may occur more frequently than currently thought. Even if only slight changes of the bulla wall are detected on CT, early-stage cholesteatoma should be considered. The narrow anatomic conditions in brachycephalic dogs possibly predispose such breeds to develop cholesteatoma after middle ear surgery because complete removal of all inflammatory and epithelial tissue can be more difficult than in other breeds. To the authors' knowledge, this is the first report of an aural cholesteatoma causing sensory deficits of the trigeminal nerve.