Page 2075 - Cote clinical veterinary advisor dogs and cats 4th

1038 Vestibular Disease

Etiology and Pathophysiology • Otoscopic exam: evaluate tympanic mem- osteotomy and total ear canal ablation) may
be required to remove infected tissues.
• Basic neuroanatomy of the vestibular system branes for integrity. • Nasopharyngeal polyps: bulla osteotomy
VetBooks.ir lar canals, saccule, utricle) located within Advanced or Confirmatory Testing • Hypothyroidism: thyroid supplementation
○ Peripheral: vestibular receptors (semicircu-
(p. 681)
the petrous temporal bone and cranial
• Bulla radiographs: dorsoventral, oblique
(p. 525)
nerve VIII (vestibulocochlear nerve)
○ Central: vestibular nuclei in the dorsal lateral, and rostroventral-caudodorsal open- • Neoplasia: surgical excision may be pos-
mouthed views. Abnormalities include soft-
portion of the medulla oblongata, ves- tissue or fluid opacity within the bulla and sible for meningioma and choroid plexus
tibular pathways of the brainstem and sclerosis of the tympanic bulla. tumors, depending on lesion location.
spinal cord (medial longitudinal fasciculus, • Oropharyngeal and otoscopic exam under Surgical excision of tumors in the middle
vestibulospinal tracts), vestibular compo- general anesthesia to identify nasopharyngeal and inner ear may be possible but is difficult.
nents in the cerebellum, and vestibular polyps and otitis media. Abnormalities Radiation therapy may provide some relief
pathways through the caudal cerebellar include soft-tissue or fluid opacity within of clinical signs, and consultation with an
peduncle the affected tympanic bulla (p. 681). oncologist is recommended in these cases
• Cause of idiopathic peripheral vestibular • Brainstem auditory evoked response (BAER) (p. 557).
disease in dogs and cats is unknown; an test may be useful for differentiating PVD • CDV and FIP encephalomyelitis: no specific
immune-mediated mechanism is suspected, from CVD. therapy is available but nonspecific supportive
but immunosuppressive drugs such as glu- • CT scan: useful for exam of the middle ear therapy with antibiotics and glucocorticoids
cocorticoids have not been shown to help. in patients with PVD. CT scans can also be may alleviate signs temporarily (pp. 271 and
used for CVD; however, beam-hardening 327).
DIAGNOSIS artifacts in the caudal brain may preclude • Rickettsial encephalitis: doxycycline 5 mg/
evaluation of the brainstem, and small lesions kg PO q 12h (pp. 285 and 891)
Diagnostic Overview may not be visualized (MRI preferable for • Fungal encephalitis: fluconazole 5 mg/kg
Clinical signs of vestibular disease are usually this location). PO q 12h penetrates the CNS to a greater
distinctive (see above). The diagnostic challenge • MRI (p. 1132): useful for exam of peripheral degree than other antifungal medications.
consists of identifying peripheral versus central and central vestibular structures; superior Itraconazole and amphotericin B can be used
disease, which can be done on physical exam in resolution of brain parenchyma for blastomycosis (pp. 121 and 184).
most cases. The underlying cause is found using • Cerebrospinal fluid (CSF) analysis (pp. 1080 • MUO: immunosuppressive dose of predni-
specific diagnostic tests ranging from hormonal and 1323): used as an adjunct to advanced sone, initially at 2 mg/kg PO q 12h for 1-2
assays (hypothyroidism) to advanced imaging imaging, primarily to rule out encephalitis days, then 1 mg/kg PO q 12h for at least 2
(structural brain lesion). • Infectious disease testing may be required weeks. Then slowly taper the drug over 4-8
in certain cases to rule out infectious months to reach the minimal effective dose
Differential Diagnosis encephalitis. CSF is the preferred sample (p. 647).
Peripheral vestibular diseases: for CDV, FIP, and cryptococcosis. Serum • Protozoal encephalitis: clindamycin 10 mg/
• Otitis media/interna titers can be performed for Toxoplasma and kg PO q 8-12h for 4 weeks or combination
• Idiopathic peripheral vestibular disease Neospora spp. of trimethoprim-sulfadiazine 15 mg/kg PO
• Nasopharyngeal polyps: cats > dogs • CSF culture and susceptibility (C&S) testing q 12h and pyrimethamine 1 mg/kg PO q
• Hypothyroidism: dogs may be required for ruling out bacterial 24h (p. 984)
• Neoplasia: squamous cell carcinoma, ceru- encephalitis (rare). • Metronidazole toxicosis: discontinue met-
minous gland adenocarcinoma • Histopathologic exam is required for definitive ronidazole; diazepam 0.5 mg/kg IV once,
• Ototoxicosis: topical chlorhexidine or iodine; diagnosis in many diseases causing structural then 0.5 mg/kg PO q 8h until resolution
systemic aminoglycosides, and other drugs; lesions (e.g., masses). Tissue samples can be of signs; accelerates recovery; use extreme
furosemide (rare) obtained via surgical excision or stereotactic caution with oral dosing in cats due to
Central vestibular diseases: brain biopsy. idiosyncratic hepatic necrosis
• Canine distemper virus (CDV) encephalo-
myelitis TREATMENT Possible Complications
• Feline infectious peritonitis (FIP) A permanent, mild head tilt may persist after
• Rickettsial encephalitis: Rocky Mountain Treatment Overview resolution of other clinical signs.
spotted fever (RMSF), ehrlichiosis Definitive treatment for vestibular disease
• Fungal encephalitis: Cryptococcus neoformans is based on diagnosis of the underlying Recommended Monitoring
most common; blastomycosis or coccidioido- cause. • Serial neurologic exam every 4 weeks
mycosis in certain regions of North America • Serial infectious disease testing if indicated
• Meningoencephalitis of unknown origin Acute General Treatment
(MUO) • Meclizine 25 mg/dose PO q 24h in PROGNOSIS & OUTCOME
• Protozoal encephalitis: Toxoplasma gondii, dogs (12.5 mg/dose PO q 24h in cats)
Neospora caninum or maropitant 1 mg/kg SQ q 24h can • Prognosis for most PVDs is good with
• Neoplasia: meningioma, choroid plexus help alleviate signs of nausea and vomit- specific treatment, with the exception of
tumor, lymphoma, metastatic neoplasia ing. Meclizine causes less sedation than neoplasia, which carries a guarded to poor
• Metronidazole toxicosis diphenhydramine and other antihistamines prognosis.
• Cerebrovascular accident (infarct) and can be purchased as an over-the-counter • CDV and FIP encephalomyelitis: generally
drug. poor even with treatment
Initial Database • Idiopathic PVD: clinical signs improve spon- • Rickettsial and protozoal encephalitis: good
• CBC, serum biochemical analysis, urinalysis: taneously over 1-2 weeks; no treatment has with early and specific treatment
results often normal been shown to accelerate natural resolution • Fungal encephalitis: fair to guarded; long-
• Thyroid hormone analysis: low total of the disorder. term treatment may be required to control
thyroxine (T 4) and free T 4 and elevated • Otitis media/interna: systemic antibiotics clinical signs
thyroid-stimulating hormone (TSH) in dogs ± antifungals for 6-8 weeks, ideally based • MUO: fair to guarded. Many dogs respond
with hypothyroidism on C&S results. Surgical treatment (bulla initially to treatment, but relapse is common.

www.ExpertConsult.com