Horner's Syndrome
 

Right congenital Honer's syndrome with anisocoria.   Left Horner's syndrome. Right Horner's sydrome.

The patient has a slight right ptosis with ipsilateral miosis(you may need to shield the eyes or dim the light to accentuate the anisocoria). There is an apparent right enophthalmos. Additional signs (which may be difficult to detect) are anhydrosis and vasodilation of head and neck if the lesion were pre-ganglionic. Look for the cause: difference in eye colour in congenital Horner's syndrome (as in this case, the right eye is lighter than the left) neck scar as in thryoidectomy wasting of ipsilateral hand muscles due to brachial plexus lesion as in Pancoast's tumour scars below the claivcle from sympathetomy for Raynaud's disease (this is an out-dated treatment)

Questions:

1. What is the cause enophthalmos in Horner's syndrome?

answer
The patient has apparent enophthalmos due to narrowing of the palpebral fissure. This enophthalmos is not true enophthalmos and cannot be demonstrated with exophthalmometer. It is causes by the ptosis and updrawing of the lower lid as a result of paralysis of the Muller's muscle of the upper lid and the smooth muscle of the lower lid retractor.

2. What is the reason for heterochromic iridis in congenital Horner's syndrome ?

answer
Sympathetic stimulation of the iris is essential for the migration of melanocytes during embryogenesis. Therefore, in congenital Horner's syndrome, the affected irid is lighter than the unaffected side.

3. What happen to the intraocular pressure and the accommodation in an eye with Horner's syndrome?

answer
The intraocular pressure is lower (typically about 5 mmHg than the normal side) and the accommodation is increased compared with the normal side.

4. How do you confirm Horner's syndrome?

answer
Physical signs as above is usually all that is needed
In doubtful cases, 4% cocaine eyedrop can be used. Cocaine acts by blcoking re-uptake of adrenaline. In a normal eye, dilatation occurs but in Horner dilatation is absent since little or no adrenaline is released.

5. How could you localize the lesion pharmaceutically in Horner's syndrome?

answer
1% hydroxyamphetamine can be used. It acts by releasing adrenaline from the third order  neurone junction at the iris. . In post-ganglionic lesion (third order neurone lesion), the pupil will not respond to the drop. Whereas in pre-ganglinoic lesions (first or second order neurone lesions), the pupil will dilate in response to the drop.
Alternatively, adrenaline in concentration of 1:1000 can be used to test denervation hypersensitivity. In post-ganglionic lesion (third order lesion), the pupil will dilate but not if the lesion is pre-ganglionic (first or second order). The responses are opposite to that of 1% hydroxyamphetamine.

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