a) What are the clinical features of Horner’s syndrome?
b) What additional features are associated with lateral medullary syndrome?
a) Horner’s syndrome:
b) Lateral Medullary Syndrome:
Horner's syndrome (the four features mentioned above) is not a problem to remember.
The lateral medullary syndrome, however, is somewhat more taxing on the neurons.
Thankfully, strokecentre.org has an excellent resource for identification (and explanation) of stroke syndrome features. This is their entry on the Lateral Medullary Syndrome (Wallenberg Syndrome)
The best way to memorise lateral medullary syndrome features would be to remember the ipsilateral Horners and the contralateral pain and temperature loss. The word "medullary" should dredge up one's recollection of medullary cranial nerve nuclei, of which nerves 5 9 and 10 are involved.