USMLE Step 1 Review/Neurology
Small, irregular pupil that does not react to light but does react to accommodation.
Localization is to the midbrain and the cause is neurosyphilis. The pupil's better response to a near than to a light stimulus is because the lesion involves the more dorsally-located fibers that subserve the pupil response to light and spares the more ventrally-located fibers that subserve the pupil response to accommodation.
Care should be taken to not confuse Argyll-Robertson pupil with an Adie's tonic pupil, Horner's syndrome or third nerve lesions.
Regarding what to do in case of syncope:
If the face is red, raise the head.
If the face is pale, raise the tail!Last modified on 14 July 2009, at 13:42