Page 857 - Problem-Based Feline Medicine

38 – THE CAT WITH A HEAD TILT, VESTIBULAR ATAXIA OR NYSTAGMUS 849

Prognosis Clinical signs

Prognosis is good if treatment is given early when the Sudden onset of head tilt associated with somnolence
only clinical signs are bilateral vestibular signs. or stupor following a road accident or other trauma
that caused a fracture at the base of the skull affecting
Prognosis is poor in the late stage of the disease when
the petrosal and ethmoid bones.
the animal’s consciousness is significantly altered.
Facial paresis/paralysis and/or Horner’s syndrome
CONGENITAL PENDULAR NYSTAGMUS* may be present if there is hemorrhage in the middle ear.
If the injury is primarily intracranial, facial paresis/para-
Classical signs lysis and/or ipsilateral proprioceptive deficits may be
● Siamese, Himalayan and white tiger cats. present.
● Pendular nystagmus, i.e., the phase of the
On otoscopic examination, blood may be observed in
nystagmus is equal on both sides. the ear canal.
● Present from birth.
Diagnosis
Clinical signs
History of a road accident.
Typically, the nystagmus has a rapid, short and oscil-
latory motion that is equal bilaterally. It is observed Brain auditory-evoked responses (BAER) may be
especially when the cat is fixing its gaze. helpful in localizing the lesion to mainly a peripheral or
central location.
The defect is within the visual pathways and not the
vestibular pathways. No obvious visual impairment is Survey radiographs of the skull are difficult to inter-
present. pret because of the juxtaposition of multiple structures.
The nystagmus is always congenital and is evident in
the first few weeks of life. DRUG-INDUCED
It occurs primarily in Siamese, Himalayan and white
tiger cats. Classical signs
Medial strabismus is usually simultaneously present. ● Unilateral or bilateral peripheral vestibular
signs, following the use of drugs that are
Diagnosis toxic for the vestibular receptors.
● Concomitant deafness is frequent.
Diagnosis is based on the characteristic oscillatory nys-
tagmus.
Pathogenesis
FRACTURES OFTHE PETROUS TEMPORAL Multiple drugs cause damage to the vestibular and/or
BONE OR TYMPANIC BULLA, AND ETHMOID auditory receptors separately or simultaneously.
FRACTURE (BASE OFTHE SKULL)
Aminoglycosides especially streptomycin, chloram-
phenicol, chlorhexidine, cisplatin, furosemide, sal-
Classical signs
icylates and ceruminolytic agents are a few of
● Altered consciousness and head tilt after a long list of agents that may cause damage to these
a recent accident. receptors.
● +/- Facial nerve paresis/paralysis and
Horner’s syndrome. Clinical signs
● +/- Signs of brainstem involvement such
as proprioceptive deficits. Toxicity occurs following systemic or topical admin-
istration.