Vestibular disorders in cats

Vestibular disorders are common in cats and often cause ataxia. They are generally easy to distinguish from spinal cord disease because of disturbances in balance leading to head tilts, circling, vomiting and nystagmus.

1) Idiopathic vestibular syndrome

© Norsworthy et al, 1998 The Feline Patient. Lippincott Williams & Wilkins

Feline idiopathic vestibular syndrome is a common disorder of unknown origin or causes. It results from dysfunction of either the peripheral vestibular receptors in the inner ear or the vestibulocochlear nerve (eight cranial nerve). Adult cats of any age are affected. There is no breed or sex predilection. 

Normal anatomy of the inner ear

Clinical signs

Acute or peracute onset of rolling, falling, ataxia (unbalance), tight circling and/or head tilt. Cats often assume a crouched position or lean to one side and are reluctant to move. Clinical signs are always to the side of the lesion. Other less common signs are vomiting, anorexia and vocalising. There is also a rotary or horizontal nystagmus (eye rolling) with the fast phase away from the side of the lesion. Conscious proprioception (sensations) are normal but may be difficult to assess. Differential diagnoses include otitis interna, nasopharyngeal polyps, neoplasia of the eighth cranial nerve, head trauma, drug toxicity (furosemide, aminoglycosides) and vascular disorders (heart disease, ischaemic encephalopathy and vasculitis).

Typical head tilt and circling behaviour of cats with vestibular diseases

Treatment

Treatment includes supportive care (quiet, valium for reducing anxiety) and medication, including fluids and anti-emetics (metoclopramide 0.2-0.4 mg PO oid). Glucocorticoids are not recommended.

Prognosis

Prognosis for complete recovery is excellent within 2-3 weeks. The head tilt is often slow to normalise over 3-4 weeks and some cats are left with a permanent head tilt to some degree.

2. Feline cuterebra infection

3. Congenital vestibular disease

Congenital vestibular disease has been documented in Burmese, British Cream, and Siamese cats, beginning at 3-4 weeks of age with resolution at 3-4 months of age. Clinical signs may be severe, resulting in rolling and marked disorientation.

4. Otitis interna

5. Toxicity

Causes of drug-induced vestibular disease includes:

1. metronidazole - narrow margin of safety
2. aminoglycoside antibiotics (gentamicin, baytril, orbax, zeniquin)
3. frusemide
4. ear cleansers - propylene glycol contained in cleaning solution

6. Nasopharyngeal polyps

Nasopharyngeal polyps are uncommon, benign, smooth, pink-red, fleshy, pedunculated, inflammatory growths of fibrous connective tissue that are found in the external ear canals of young cats. They may arise from the mucosal lining of the tympanic bulla, the pharyngeal mucosa, or the auditory tube. These polyps may be congenital or due to viral (calicivirus) or bacterial infection. Bacterial otitis externa or media due to obstruction of the ear canal or tympanic bulla may be present.

Diagnosis involves sedation and deep otoscopic examination of the vertical and horizontal ear canals. Purulent discharge may need to be gently suctioned from the ear canal to visualize the polyp. Use of a videographic otoscope greatly enhances the ability to evaluate the deep horizontal canal for polyps. Polyps originating from the eustachian tube may be seen by gently retracting the soft palate rostrally. Computed tomography or MRI may be helpful if a mass is suspected in the tympanic bulla that cannot be seen otoscopically. Definitive diagnosis is made via histopathology.

Surgical removal is curative as long as the entire polyp and stalk are removed. This often involves performing a bulla osteotomy, as the base of the polyp is often in the tympanic bulla. Incomplete removal of the base of the polyp leads to rapid regrowth and return of clinical signs.