Vestibular Disease, Idiopathic—Cats is an acute onset non-progressive disturbance of the peripheral vestibular system of cats.
PATHOPHYSIOLOGY
Unknown.
Suspected abnormal flow of the endolymphatic fluid in the semicircular canals of the inner ear, secondary to a disturbance in the production, circulation, or absorption of the fluid.
Possible intoxication of the vestibular receptors or inflammation of the vestibular portion of the vestibulocochlear nerve (cranial nerve VIII).
SYSTEMS AFFECTED
Nervous—peripheral vestibular system
INCIDENCE/PREVALENCE
Sporadic acquired disease
None reported
SIGNALMENT
Species – Cat
Mean Age and Range
Any age; rare in cats < 1 year of age
SIGNS
General Comments
Limited to signs associated with peripheral vestibular disturbance.
Historical Findings
Sudden onset of severe disorientation, falling, rolling, leaning, vocalizing, and crouched posture; tendency to panic when picked up.
Physical Examination Findings
Head tilt—always toward the side of the lesion; occasionally disease is bilateral with wide, side-to-side excursions of the head either without a head tilt or with a mild tilt toward the more severely affected side.
Resting nystagmus—usually horizontal, but may be rotatory with the fast phase always in direction opposite to the head tilt; with bilateral disease, the abnormal nystagmus is usually mild or not present, and physiologic nystagmus or conjugate eye movements are diminished to absent.
Vestibular ataxia with tendency to roll and fall toward the side of the head tilt.
Preservation of strength and normal proprioception; with bilateral disease, patient may be reluctant to ambulate, preferring to stay in a crouched posture and possible wide-based stance.
CAUSES
Unknown.
Previous upper respiratory tract infection—suspected in some patients; relationship not confirmed; in limited necropsy data no evidence of inflammation.
RISK FACTORS
May be an increase in cases in the summer and early fall, possibly after outbreaks of upper respiratory disease; disease can occur throughout the year.
DIAGNOSIS
DIFFERENTIAL DIAGNOSIS
Diagnosis made on the basis of acute onset peripheral vestibular signs that improve rapidly without specific treatment.
Otitis media and interna (e.g., bacterial, parasitic)—may have concurrent ipsilateral facial nerve (cranial nerve VII) paresis or paralysis, Horner’s syndrome, deafness, ruptured tympanic membrane, otitis externa, and/or radiographic changes in tympanic bulla; signs usually not self-limiting.
Nasopharyngeal polyp(s)—may cause unilateral or, much less commonly, bilateral peripheral vestibular signs; may have concurrent tympanic bulla involvement; signs usually not as acute and severe at onset and are not self-limiting.
Blue-tailed lizard ingestion—southeastern United States; thought to produce a similar acute, unilateral, peripheral vestibular syndrome; vomiting, salivation, irritability, and trembling also noted; most patients recover without specific treatment.
Aminoglycoside toxicity, especially streptomycin—may cause acute unilateral or bilateral peripheral vestibular syndrome and/or hearing loss; differentiated by history of drug use.
CBC/BIOCHEMISTRY/URINALYSIS
Normal
IMAGING
None usually necessary.
Radiographs of tympanic bullae: normal radiographs do not rule-out bulla disease.
CT or MRI—occasionally required to rule out other causes such as otitis media and interna and nasopharyngeal polyp(s).
DIAGNOSTIC PROCEDURES
Brainstem auditory evoked response—may help rule-out other causes (e.g., otitis media and interna; nasopharyngeal polyp); with idiopathic vestibular disease hearing not affected since disease limited to the vestibular portion of cranial nerve VIII.
PATHOLOGIC FINDINGS
None reported
TREATMENT
APPROPRIATE HEALTH CARE
Usually outpatient.
Inpatient—severely affected patient may require hospitalization for supportive care.
NURSING CARE
Mild disease—treatment supportive only.
Severe disease—may require intravenous or subcutaneous fluids; maintain patient in quiet, well-padded cage.
ACTIVITY
Restricted according to the degree of disorientation and ataxia.
DIET
Patient may initially be reluctant to eat and drink because of disorientation and/or nausea.
CLIENT EDUCATION
Reassure client that, despite initial alarming and often incapacitating signs, the prognosis for rapid and complete recovery is excellent.
MEDICATIONS
DRUG(S) OF CHOICE
Sedatives—for severe disorientation and rolling; diazepam (1–5 mg/cat PO q8–12h) and acepromazine (0.02–0.05 mg/kg IM, SC, IV).
Antiemetic drugs and drugs against motion sickness—questionable benefit; e.g., meclizine HCl 12.5 mg PO q24h.
Glucocorticoids—not recommended since do not alter course of the disease.
Antibiotics—recommended if otitis media and interna cannot be ruled out; trimethoprim-sulfa (15 mg/kg PO q12h); first-generation cephalosporin (e.g., cephalexin 10–30 mg/kg PO q6–12h); amoxicillin/clavulanic acid (Clavamox 62.5 mg/cat PO q12h, Clavaseptin 12.5 mg/kg PO q12h).
FOLLOW-UP
PATIENT MONITORING
Neurologic examination of outpatient—repeat in approximately 72 hours to confirm stabilization and initial improvement.
Inpatient—discharge patient when able to ambulate and resume eating and drinking.
EXPECTED COURSE AND PROGNOSIS
Marked improvement, especially in resting nystagmus within 72 hours, with progressive improvement of gait and head tilt.
Patients usually normal within 2–3 weeks.
Head tilt—final sign to resolve; mild residual tilt may remain.
If signs do not improve rapidly, other causes of vestibular disease should be pursued.
Rarely recurs.
MISCELLANEOUS
ABBREVIATIONS
CT = computed tomography
MRI: magnetic resonance imaging
Visit your veterinarian as early recognition, diagnosis, and treatment are essential.