Page 1344 - Problem-Based Feline Medicine

1336 PART 15 CAT WITH EYE PROBLEMS

long tracts, T1–T3 spinal nerves or nerve roots, ascend- elbow cannot be flexed or the paw picked up, result-
ing pre-ganglionic fibers, cranial cervical ganglion ing in excoriation of the dorsum of the paw. Muscle
and sympathetic post-ganglionic fibers in middle ear or atrophy is apparent within 5–7 days of injury to
orbit. Less commonly protrusion is the result of dys- the motor nerve roots. Damage to C7–T1 may also
function of the smooth muscle fibers innervated by the result in loss of the ipsilateral cutaneous trunci
sympathetic nerve. (panniculus) reflex.
More common causes in the cat include:
● Middle ear disease especially nasopharyngeal Diagnosis
polyps. Nasopharyngeal polyps arise in the middle
Any cat with an apparently non-painful, non-inflamed
ear and emerge into the external ear canal or naso-
prominent third eyelid, which also has miosis, upper lid
pharynx. Typically they occur in young cats
ptosis and enophthalmos should be suspected as having
(< 5 years), but any age can be affected.
Horner’s syndrome.
● Disruption of ascending sympathetic pathways
in the neck due to injury or inflammation associ- Pharmacological testing with sympathomimetics is
ated with fight wounds. controversial, and the indirect-acting sympathomimetic
● Injury to nerve roots of T1–T3 associated with fore- hydroxyamfetamine is no longer available in some
limb trauma, usually from motor vehicle accidents. countries. Reliable diagnostic protocols are not avail-
● Anterior thoracic cavity disease, e.g. mediastinal able, however a rapid (within 5–8 minutes) reversal of
lymphoma. signs following the administration of one drop of 10%
phenylephrine is suggestive of post-ganglionic dener-
Rarely, is third eyelid protrusion the result of nerve
vation hypersensitivity, indicating that the lesion is
damage within the brain or spinal cord, or smooth mus-
somewhere rostral to the cranial cervical ganglion.
cle disease.
Anatomically this corresponds to localization of the
lesion in the middle ear or orbital structures rostral to
Clinical signs the middle ear. The response should always be com-
pared with that in the contralateral normal eye.
Usually there is a unilateral, non-painful prominence
of the third eyelid, together with other signs of Lesion localization will not be possible in many
sympathetic denervation, i.e. miosis, upper lid ptosis cases, and many cases seem to be idiopathic.
(“drooping”), enophthalmos.
Other signs may be present in some cases, which may Differential diagnosis
enable further localization of the lesion, e.g.
Third eyelid dysautonomia (Haw’s) is always bilateral,
● An abscess or cellulitis of cervical soft tissue
and is not associated with other signs of sympathetic
structures suggests disruption of ascending pregan-
denervation. Horner’s syndrome is almost always
glionic fibers.
unilateral.
● Signs of middle or inner ear disease such as a
head tilt or circling. Nasopharyngeal polyp may be
seen as a fibrous mass emerging into the external Treatment
ear canal, or cause noisy breathing, dyspnea with or
Where possible, treatment should be directed at the
without nasal discharge, sneezing or coughing and
associated problems which may be causing interruption
gagging.
of sympathetic pathways.
● Ipsilateral forelimb lameness may occur from
damage to nerve roots or nerves innervating the leg. The disfigurement created by Horner’s syndrome can
Radial nerve paresis or paralysis may occur be reversed by frequent (at least 2–3 times daily) appli-
concurrently with avulsion of T1–T3 nerve roots if cation of one drop of 10% phenylephrine in the affected
C8 or T1 nerve roots are injured. If the musculo- eye. This treatment only alters the appearance of the
cutaneous nerve roots (C5–7) are also injured, the eye and does nothing else for the cat’s well-being,