Describe the anatomy of the sympathetic pupillary pathway.

Answer
There are three orders of neurones in the sympathetic pupillary pathway:
1st order: the nerves begin in posterior hypothalamus and travels through
the brain and synapse at the spinal cord.
2nd order: the nerves travel from the spinal cord over the apex of the lung
to synapse at the superior cervical ganglia
3rd order: the nerves enter the skull as pericarotid plexus along the internal carotid artery. They then travel along the ophthalmic division of the trigeminal 
nerve and then the nasociliary nerve and finally the long ciliary nerve to innervate the iris dilator pupillae.
 

For each condition below, give the diagnosis and the effect of:
a. 1% hydroxyamphetamine
b. 0.1% adrenaline 
on the affected pupil
 

Patient A A patient with sixth nerve palsy

Answer
Aneurysm of the internal carotid artery within the cavernous 
sinus. This is a post-ganglionic cause of Horner's syndrome.
a. 1% hydroxyamphetamine will not dilate the miosed pupil
1% hydroxyamphetamine causes release of noradrenaline
from terminal axon. In post-ganglionic lesion, the third order 
neurone is damaged and unable to release noradrenaline. 
Therefore, 1% hydroxyamphetamine dilate post-ganglionic 
Horner's pupil but not pre-ganglionic or central Horner's pupil.
b. 0.1% adrenaline will dilate the miosed pupil.
Denervation supersensitivity causes the miosed pupil to dilate in response to 0.1% adrenaline. Central and post-ganglionic causes of Horner's syndrome will not be dilated with 0.1% adrenaline.

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