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| Argyll Robertson pupil | |
|---|---|
 | |
| Specialty | Neurology  |
| Risk factors | A highlyspecific sign ofneurosyphilis |
| Diagnostic method | Pupillary light reflex and accommodation reflex tests |
Argyll Robertson pupils (AR pupils) are bilateral smallpupils that reduce in size on a near object (i.e., theyaccommodate), but donotconstrict when exposed to bright light (i.e., they do not react). They are a highlyspecific sign ofneurosyphilis; however, Argyll Robertson pupils may also be a sign ofdiabetic neuropathy. In general, pupils that accommodate but do not react are said to showlight-near dissociation (i.e., it is the absence of amiotic reaction to light, both direct and consensual, with the preservation of a miotic reaction to near stimulus (accommodation/convergence)).[1]
AR pupils are extremely uncommon in the developed world. There is continued interest in the underlying pathophysiology, but the scarcity of cases makes ongoing research difficult.
The two different types of near response are caused by different underlying disease processes.Adie's pupil is caused by damage toperipheral pathways to the pupil (parasympathetic neurons in theciliary ganglion that cause pupillary constriction to bright lightand with near vision). The pathophysiologic mechanism which produces an Argyll Robertson pupil is unclear, but is believed to be the result of bilateral damage to the pretectal nuclei in the midbrain. Studies have failed to demonstrate a focal localising lesion. Research has implicated the rostral midbrain in the vicinity of thecerebral aqueduct of the third ventricle as the most likely region of damage. A lesion in this area would involve efferent pupillary fibres on the dorsal aspect of theEdinger-Westphal nucleus (associated with the response to light) while sparing the fibres associated with the response to near, which lie slightly more ventrally.[2]The exact relationship between syphilis and the two types of pupils (AR pupils andtonic pupils) is not known at the present time. The older literature on AR pupils did not report the details of pupillary constriction (brisk vs. tonic) that are necessary to distinguish AR pupils from tonic pupils. Tonic pupils can occur in neurosyphilis.[3] It is not known whether neurosyphilis itself (infection byTreponema pallidum) can cause tonic pupils, or whether tonic pupils in syphilis simply reflect a coexisting peripheral neuropathy.
Thompson and Kardon[4] summarize the present view:
A third cause of light-near dissociation isParinaud syndrome, also called dorsal midbrain syndrome. This uncommon syndrome involves vertical gaze palsy associated with pupils that “accommodate but do not react."[5] The causes of Parinaud syndrome include brain tumors (pinealomas), multiple sclerosis and brainstem infarction.
Due to the lack of detail in the older literature and the scarcity of AR pupils at the present time, it is not known whether syphilis can cause Parinaud syndrome. It is not known whether AR pupils are any different from the pupils seen in other dorsal midbrain lesions.
The condition is diagnosed clinically by a physician.
There is no definite treatment, but, because syphilis may be an underlying cause, it should be treated.However, because this sign is associated with neurosyphilis, it should be treated with crystalline penicillin 24 mU intravenous per day for 10 to 14 days. If the patient is allergic to penicillin, they should undergo desensitization and then be treated.
Argyll Robertson pupils were named afterDouglas Argyll Robertson (1837–1909), a Scottish ophthalmologist and surgeon who described the condition in the mid-1860s in the context of neurosyphilis.
In the early 20th century,William John Adie described a second type of pupil that could "accommodate but not react". Adie'stonic pupil is usually associated with a benign peripheral neuropathy (Adie syndrome), not with syphilis.[6]
When penicillin became widely available in the 1940s, the prevalence of AR pupils (which develop only after decades of untreated infection) decreased dramatically. AR pupils are now quite rare. A patient whose pupil "accommodates but does not react" almost always has a tonic pupil, not an AR pupil.
In the 1950s, Loewenfeld distinguished between the two types of pupils by carefully observing the exact way in which the pupils constrict with near vision.[7] The near response inAR pupils is brisk and immediate. The near response intonic pupils is slow and prolonged.