Idiopathic Vestibular Syndrome (IVS) stands as one of the most prevalent neurological disorders encountered in veterinary medicine. However, current literature reveals a lack of consistent consensus regarding its precise definition, diagnostic protocols, and therapeutic strategies. To address this gap, a study was conducted to gather and analyze the expert opinions of veterinary neurologists on these critical aspects of IVS. Utilizing an online survey, specialists were polled on their definitions of IVS, their preferred diagnostic methods for both dogs and cats, and their go-to treatment approaches. The findings indicate a largely global consistency in how IVS is defined, diagnosed, and treated, with a notable tendency in the European Union to favor otoscopy over advanced imaging to exclude other potential diseases. This comprehensive overview provides valuable insights into the current practices of veterinary neurology experts and underscores areas ripe for further investigation to bridge the divide between theoretical knowledge and practical application in managing IVS.
Understanding Idiopathic Vestibular Syndrome
Idiopathic Vestibular Syndrome (IVS) is a common neurological condition, particularly affecting older dogs (over nine years) and cats of any age, with some regions in North America observing seasonal patterns. The condition typically presents acutely, characterized by a head tilt towards the affected side, pathological nystagmus (involuntary rapid eye movements), positional strabismus (misalignment of the eyes), and vestibular ataxia (loss of coordination due to vestibular system issues). Nausea and vomiting are also frequently observed symptoms. [cite:1,3-7] A key characteristic of IVS is its rapid improvement, with most cases resolving within a few days and showing complete resolution of clinical signs within two to four weeks. However, some animals may experience persistent mild residual signs, such as a slight head tilt or ataxia, throughout their lives. This rapid improvement is a crucial distinguishing factor from other causes of vestibular disease.
Given that IVS is a diagnosis of exclusion, an extensive diagnostic workup is often recommended to rule out other potential causes. These can include cerebral ischemia, otitis media/interna (middle and inner ear infections), meningoencephalitis (inflammation of the brain and meninges), trauma, thiamine deficiency, tumors, and other conditions. The exact pathomechanism of IVS in veterinary medicine remains incompletely understood. In human medicine, similar vestibular diseases have more clearly defined etiologies. For instance, Menière’s disease involves distension of the inner ear’s membranous labyrinth, while benign positional paroxysmal vertigo (BPPV) is associated with free-floating otoliths in the semicircular canals. Acute vestibular neuritis (AVN), often idiopathic, can be linked to herpes virus infection, autoimmune causes, or microvascular ischemia, presenting with sudden dizziness, nystagmus, and nausea, typically resolving within weeks. [cite:8-17]
Diagnosis and therapy for vestibular disorders in human medicine are tailored to the specific etiology. Treatments range from symptomatic approaches to targeted therapies to manage dizziness and promote central compensation. Medications like betahistine are used to improve blood circulation in the vestibular organ, and specific movement exercises, such as repositioning maneuvers for BPPV, are employed. [cite:18-23] In contrast, veterinary medicine currently lacks clear guidelines for IVS diagnosis and treatment, with recommendations often focusing on symptomatic therapy, including anti-nausea medications (e.g., ondansetron), antiemetics (e.g., maropitant, metoclopramide), and intravenous fluid therapy. This study aimed to capture veterinary neurology experts’ opinions on the definition, diagnostics, and therapeutics for IVS in dogs and cats, also examining potential regional differences.
Diagnostic Approaches for IVS
The survey revealed a broad consensus among veterinary neurologists regarding the definition of IVS, with most characterizing it as an acute to peracute, improving, peripheral vestibular disorder. Key clinical signs often included in definitions were head tilt, nystagmus, and ataxia. Diagnostic procedures considered essential for identifying IVS in dogs and cats largely align with current literature, emphasizing a thorough neurological examination (NE) as paramount.
Diagnostic Methods in Dogs
For canine IVS, NE was the most frequently selected diagnostic tool. Other commonly cited diagnostics included magnetic resonance imaging (MRI), serum biochemistry (SB), complete blood cell count (CBC), cerebrospinal fluid (CSF) examination, and blood pressure (BP) measurement. Notably, participants from North America (NA) frequently prioritized MRI and CSF analysis, while European Union (EU) specialists often highlighted SB, CBC, and MRI. Interestingly, otoscopy was selected with similar frequency to MRI by EU participants, whereas it was less emphasized by UK and NA specialists. Additional tests mentioned in free-text responses included urinalysis, urine protein-to-creatinine ratio, palpation for bulla pain, free T4, brainstem auditory evoked response (BAER), and canine distemper titer. When participants were limited to selecting their top five diagnostic tests, NE, MRI, SB, otoscopy, and thyroid level determination (T4 and TSH) emerged as the most crucial.
Diagnostic Methods in Cats
Similar to dogs, NE was the most frequently recommended diagnostic for feline IVS. Other core diagnostics included MRI, SB, CBC, BP, and CSF examination. NA participants tended to place a greater emphasis on SB compared to MRI, and focused more on blood examinations overall than EU participants. Conversely, otoscopy was selected more often by EU respondents for cats than by NA respondents. While MRI was considered essential by all UK participants, alongside NE, CSF was less frequently chosen by EU specialists compared to the overall group. Additional diagnostics mentioned for cats included Cryptococcus titers, feline infectious peritonitis (FIP) diagnostics, urinalysis, palpation for bulla pain, and thiamine levels. When asked to select their top five diagnostics for feline IVS, NE, MRI, SB, otoscopy, and BP were frequently chosen.
Treatment Strategies for IVS
The survey on treatment preferences for IVS revealed a consistent approach across different regions and between species, primarily focusing on symptomatic and supportive care.
Treatment of IVS in Dogs
Intravenous fluid therapy was the most recommended treatment for canine IVS, with a common rate of 2 ml/kg/h, although NA specialists also frequently used 3 ml/kg/h. Some specialists indicated adjusting fluid rates based on the patient’s hydration status. Maropitant was the most widely selected antiemetic, typically administered at a dosage of 1 mg/kg once daily. Metoclopramide and ondansetron were less frequently chosen, and a few participants used a combination of these antiemetics. Propentofylline was exclusively used by EU specialists, with 17 participants choosing a dose of 3 mg/kg twice daily. Betahistine was used sporadically, with a preferred dosage of 25 mg/kg twice daily. Physiotherapy, including coordination and positioning exercises, was reported as a supportive therapy used worldwide to aid in the improvement of clinical signs.
Treatment of IVS in Cats
For feline IVS, intravenous fluid therapy was also a common recommendation, with 75 participants favoring a rate of 2 ml/kg/h. Maropitant was frequently recommended as an antiemetic, at a dosage of 1 mg/kg once daily, though it was mentioned less often than in dogs. Metoclopramide and ondansetron were selected by a smaller number of specialists. Propentofylline was used in a few cases within the EU at a dosage of 3 mg/kg twice daily. Betahistine was rarely mentioned for cats, and UK participants did not select it as a treatment option. Vitamin B complex was used sporadically, and corticosteroids were occasionally administered in NA. Physiotherapy, incorporating coordination and balance exercises, was employed by about one-third of all participants, with some also using positioning exercises.
Discussion and Conclusion
The study highlights a notable global consistency in the definition of IVS as an acute to peracute, improving, peripheral vestibular disorder, aligning with previous statistical modeling studies. These studies identified additional risk factors such as older age, higher body weight, pathological nystagmus, facial nerve paresis in dogs, and being non-purebred and lacking a history of otitis externa in cats.
While diagnostic approaches are largely aligned with literature, regional differences in diagnostic preferences were observed. EU specialists’ preference for otoscopy over advanced imaging like MRI and CSF analysis may be influenced by factors such as owner finances, insurance coverage, availability of equipment, and concerns about anesthesia risks, particularly in older animals. Recent MRI studies have challenged the notion of entirely normal MRI findings in IVS, suggesting possible inner ear signal abnormalities or asymmetry in utricular diameters, leading to proposals for alternative terms like “facial and vestibular neuropathy of unknown origin” (FVNUO) or “benign peripheral vestibular syndrome.” [cite:26-28]
Treatment largely centers on symptomatic care, including intravenous fluid therapy and antiemetics. While maropitant is a preferred choice, evidence suggests ondansetron may be more effective for nausea. The study underscores the need for species-specific treatment plans due to pharmacological differences between dogs and cats. [cite:1,56-58] The use of medications like betahistine and propentofylline, as well as exercise therapy, shows potential but requires further research to establish their efficacy in companion animals with IVS.
In conclusion, the study confirms a general agreement on the definition and core diagnostic and treatment strategies for IVS among veterinary neurologists worldwide. However, it also emphasizes the need for further research into specific therapeutic agents and diagnostic refinements to improve the management of this common neurological disorder. The consistent definition of IVS as an acute to peracute, improving, non-painful peripheral vestibular disorder affecting cats of any age and geriatric dogs is supported. Key diagnostic tools remain a detailed neurological examination, comprehensive blood tests, and otoscopy, with MRI and CSF analysis playing crucial roles in ruling out other conditions. Maropitant remains the preferred antiemetic, but the potential benefits of antinausea medications like ondansetron warrant consideration.
