This uncommon syndrome involves vertical gaze palsy associated with pupils that “accommodate but do not react." The causes of Parinaud syndrome include brain tumors (pinealomas), multiple sclerosis and brainstem infarction.ĭue 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. Parinaud syndrome Ī third cause of light-near dissociation is Parinaud syndrome, also called dorsal midbrain syndrome. To settle the question of whether the AR pupil is of central or peripheral origin, it will be necessary to perform iris transillumination (or a magnified slit-lamp examination) in a substantial number of patients who have a pupillary light-near dissociation (with and without tonicity of the near reaction), perhaps in many parts of the world. The evidence supports a midbrain cause of the AR pupil, provided one follows Loewenfeld’s definition of the AR pupil as small pupils that react very poorly to light and yet seem to retain a normal pupillary near response that is definitely not tonic. Thompson and Kardon summarize the present view: It is not known whether neurosyphilis itself (infection by Treponema pallidum) can cause tonic pupils, or whether tonic pupils in syphilis simply reflect a coexisting peripheral neuropathy. tonic) that are necessary to distinguish AR pupils from tonic pupils.
The older literature on AR pupils did not report the details of pupillary constriction (brisk vs. The exact relationship between syphilis and the two types of pupils ( AR pupils and tonic pupils) is not known at the present time. A lesion in this area would involve efferent pupillary fibres on the dorsal aspect of the Edinger-Westphal nucleus (associated with the response to light) while sparing the fibres associated with the response to near, which lie slightly more ventrally. Research has implicated the rostral midbrain in the vicinity of the cerebral aqueduct of the third ventricle as the most likely region of damage. Studies have failed to demonstrate a focal localising lesion. 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. Adie's pupil is caused by damage to peripheral pathways to the pupil (parasympathetic neurons in the ciliary ganglion that cause pupillary constriction to bright light and with near vision).
The two different types of near response are caused by different underlying disease processes. There is continued interest in the underlying pathophysiology, but the scarcity of cases makes ongoing research difficult. ĪR pupils are extremely uncommon in the developed world.
In general, pupils that accommodate but do not react are said to show light-near dissociation (i.e., it is the absence of a miotic reaction to light, both direct and consensual, with the preservation of a miotic reaction to near stimulus (accommodation/convergence). They are a highly specific sign of neurosyphilis however, Argyll Robertson pupils may also be a sign of diabetic neuropathy. Pupillary light reflex and accommodation reflex testsĪrgyll Robertson pupils ( AR pupils) are bilateral small pupils that reduce in size on a near object (i.e., they accommodate), but do not constrict when exposed to bright light (i.e., they do not react).
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