Page 854 - Problem-Based Feline Medicine

846 PART 10 CAT WITH SIGNS OF NEUROLOGICAL DISEASE

Differential diagnosis lar receptors by the product used to flush the ear (e.g.
chlorhexidine, quaternary ammonium compounds).
As in most cases of middle-inner ear disease, if there is
no swelling of the face, surgical exploration of the bulla If the peripheral vestibular signs develop 48–72
is the only reliable approach to reach a definitive diag- hours following an ear flush, an inner ear infection is
nosis. suspected. Bacteria may have been introduced through
a perforated tympanic membrane at the time of the
Middle ear polyp is usually in young cats, but can be
flush. The ear flush may not be vigorous for this to
in older cats. Typically, the progression is slower. The
occur because the tympanic membrane may have
polyp may be visible in the ear canal or oro-nasophar-
already been ruptured secondary to an otitis externa.
ynx. There is no pain, and no swelling of the face.
Alternatively, topical (e.g. gentamycin-containing ear
drops) or systemic treatment administered after the ear
Treatment flush may be toxic to the vestibular receptors.
Aggressive excision including ear canal ablation and
lateral bulla osteotomy is the treatment of choice for Clinical signs
malignant ear canal tumors. If excision is incom-
Acute onset of peripheral vestibular signs in the 72
plete, radiation therapy can be a useful adjunct to
hours following an ear flush. The flush may have been
surgery.
an elective procedure or therapeutic for a severe otitis
externa.
Prognosis
Prognosis is guarded because of the invasive nature of Diagnosis
the tumor and advanced stage of the disease by the time
Diagnosis is based on the history of acute vestibular
neurologic signs are present.
signs following a recent ear flush.
Cats with ceruminous adenocarcinoma have a 75%
1-year survival rate following aggressive ear ablation Differential diagnosis
and bulla osteotomy compared to a 33% 1-year survival
after conservative surgical resection. The prognosis is Idiopathic vestibular syndrome cannot be differenti-
more guarded for squamous cell carcinoma. ated from the iatrogenic cause if the signs appear 2–3
days following the flush.

EAR FLUSH*
Treatment
Classical signs
Whenever acute vestibular signs appear to be associ-
● Acute onset of peripheral vestibular signs ated with an ear flush, a broad-spectrum antibiotic
that develop immediately or in the such as trimethoprim-sulfa, a cephalosporine or amoxi-
72 hours following an ear flush. cillin should be administered for 2–6 weeks.

Prognosis
Pathogenesis
If the onset was immediate and due to a change in the
The exact pathogenesis is unknown, but several mech- temperature or flooding of the inner ear, then the signs
anisms have been postulated to be involved. An ear may disappear within a few hours.
flush that leads to such consequences is usually done
If the signs are the result of toxicity, the head tilt may
under anesthesia or heavy sedation. If the signs develop
remain.
immediately after the flush, it is possibly due to: (1) a
change in the temperature of the endolymph; (2) If the signs appeared 2–3 days later, most vestibular
flooding of the inner ear through a perforated tym- signs resolve except for the head tilt, which usually per-
panic membrane; or (3) a toxic effect on the vestibu- sists for the life of the animal.