Page 824 - Clinical Small Animal Internal Medicine

792 Section 8 Neurologic Disease

Toxicity sive dilation of the fourth ventricle. Arachnoid divertic­
VetBooks.ir can result in both deafness and vestibular signs by uli within the quadrigeminal cistern are more
Drug toxicity (topical, intravenous, and inhaled drugs)
commonly associated with seizures if clinical signs are
damaging the hair cells or the vestibulocochlear nerve
Caudal occipital malformation syndrome (also called a
itself. Antibiotics (aminoglycosides, erythromycin, present at all, but vestibulocerebellar signs may be noted.
minocycline, topical choramphenicol, etc.), antiseptics Chiari‐like malformation) that leads to a degree of obstruc­
(chlorhexidine), diuretics (furosemide), and miscellaneous tive hydrocephalus and dilation of the fourth ventricle or
other agents (salicylates, propylene glycol, ceruminolytic bulbomyelia may result in central vestibular signs. Severe
agents, lead, mercury, etc.) are all recognized as causes of generalized hydrocephalus can occasionally be associ­
ototoxicity in veterinary patients, with aminoglycoside ated with vestibular signs because of fourth ventricle
being the most commonly reported cause. NSAIDs are involvement, but this would be an uncommon clinical
a well‐recognized cause of reversible toxicity in people. sign. Malformations leading to high cervical instability
Early recognition and withdrawal of the medication may (i.e., atlantooccipital or atlantoaxial subluxation/luxa­
limit damage, but by the time signs are recognized, the tions) can rarely lead to secondary edema and inflamma­
damage may be permanent. Even when animals do not tion extending cranial to involve the vestibular nuclei but
recover fully from peripheral disease due to ototoxicity, caudal nuclei involvement would also be present.
they usually compensate adequately to maintain a good
quality of life. Infection
Otitis can extend through the internal acoustic meatus
Metabolic and result in intracranial disease with compression of
Hypothyroidism is often linked to peripheral vestibular the brainstem from abscess formation or even active
disease, although the association is tenuous. If hypothy­ meningitis/encephalitis, although this is less common.
roidism is detected in a patient with peripheral vestibu­ Infectious agents are usually bacterial, but fungal dis­
lar disease, treatment should be considered. ease is also possible.
Systemic infections involving the CNS or infections
Trauma apparently isolated to the CNS are uncommon in dogs,
Since the vestibular apparatus is housed in the hardest with the exception of certain signalments and geographic
bone in the body, the petrous temporal bone, trauma is locations: Cryptococcus on the west coast, coccidiodio­
not a common cause of vestibular disease. However, mycosis in desert locales, histoplasmosis and blastomy­
blunt trauma, typically hit by car, can result in skull/bulla cosis in the Midwest, to name a few. Infections typically
fractures, hemorrhage in the soft tissues of the middle cause multifocal signs that may include the vestibular
and inner ear and lead to vestibular disease. Horner’s system.
syndrome and facial paralysis may also result from direct Young dogs and cats are at higher risk for viral dis­
trauma or soft tissue swelling/hemorrhage involving the eases, with distemper and FIP being the most commonly
adjacent tissue as they are in close proximity to CN VIII. diagnosed.
Treatment for the vestibular signs would be supportive Neospora and distemper appear to have a predilection
care and time. Resolution of vestibular signs may be for cerebellar involvement which may result in vestibular
incomplete. signs.

Central Vestibular Disease Vascular
Brain tumors, stroke‐like events, drug toxicities (such as Vascular events (ischemic vs hemorrhagic) typically
metronidazole and ronidazole), nutritional deficiencies have an acute onset, but may appear progressive over a
(thiamine), infections (such as distemper, feline infec­ 24‐hour period. Causes of vascular events often do not
tious peritonitis, Toxoplasma gondii, Neospora caninum, have an underlying identifiable cause, but screening for
and fungal infections) or diseases that cause inflammation causes of thromboembolic disease, +/− bleeding disor­
of the brain (such as granulomatous or necrotizing ders, is warranted.
meningoencephalitis) may all lead to central vestibular Hypertension, primary or secondary, can lead to ves­
disease in both the dog and the cat. tibular episodes. Many of these cases mimic idiopathic
vestibular disease in history and examination findings,
Anomalous/Congenital but the events will often recur, similar to TIAs in people,
Malformations resulting in central vestibular signs may and only resolve or improve once hypertension is
be present at birth but can progress over time due to controlled. In cases where there is an acute onset of ves­
obstruction of CSF flow either within cystic structures tibular signs that clearly localize to the central vestibular
(i.e., arachnoid cysts/diverticuli) or leading to progres­ system, the cerebellum is most commonly involved, in