Argyll Robertson pupil

This is an interesting video I downloaded from youtube. I am sure it will be benefeficial for medical students to understand this.

I used to have problem remember when the pupil constricts and when it dilates till I heard this joke :

A prostitute will accomadate but will not react.

So in Argyll Robertson pupil(due to Neurosyphilis), the pupil will constrict to accomadation reflex but will not constrict to light - just as what the video showed.

It is due to damage to the periaqueductal area and is a classic sign.

The pupil is small, irregular and fixed to light but reactive to accomodation

Other causes of what perhaps incorrectly called AG pupils are pinealomas, diabetes, brainstem encephalitis, multiple sclerosis and Wernicke's encephalopathy. These conditions cause fixed semidilated pupils and sometimes unequal pupils; only a small, irregular, fixed pupil should be attributed to neurosyphilis.

I was fortunate, well unfortunate for the patient to have managed a case of neurosyphilis 2 years ago in Neurology . I still remembered the LP I did for the patient (as above) which showed VDRL positive in the LP. Patient actually improved after treated with Penicillin.

Now, the question I want to ask is - what if you get pupils which react to light but not to accomodation (reversed Argyll Robertson pupil). What is the cause ?

Clue : It occured in 1920s