Argyll Robertson pupil
Encyclopedia
Argyll Robertson pupils (“AR pupils”) are bilateral small pupil
s that constrict when the patient focuses on a near object (they “accommodate
”), but do not constrict when exposed to bright light (they do not “react” to light). They are a highly specific sign of neurosyphilis
. In general, pupils that “accommodate but do not react” are said to show light-near dissociation. A video of AR pupils and light-near dissociation is available here
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.
described a second type of pupil that could “accommodate but not react.” Adie’s tonic pupil is usually associated with a benign peripheral neuropathy (Adie syndrome
), not with syphilis.
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. The near response in AR pupils is brisk and immediate. The near response in tonic pupils is slow and prolonged.
that cause pupillary constriction to bright light and with near vision). The pathophysiologic mechanism which produces an Argyll Robertson pupil is unclear. Studies have failed to demonstrate a focal localising lesion. Research has implicated the rostral mid-brain in the vicinity of the cerebral 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 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.
The exact relationship between syphilis and the two types of pupils (AR pupils and tonic 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. 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.
Thompson and Kardon (2006) summarize the present view:
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.
Pupil
The pupil is a hole located in the center of the iris of the eye that allows light to enter the retina. It appears black because most of the light entering the pupil is absorbed by the tissues inside the eye. In humans the pupil is round, but other species, such as some cats, have slit pupils. In...
s that constrict when the patient focuses on a near object (they “accommodate
Accommodation (eye)
Accommodation is the process by which the vertebrate eye changes optical power to maintain a clear image on an object as its distance changes....
”), but do not constrict when exposed to bright light (they do not “react” to light). They are a highly specific sign of neurosyphilis
Neurosyphilis
Neurosyphilis is an infection of the brain or spinal cord caused by the bacterium Treponema pallidum. It usually occurs in people who have had untreated syphilis for many years, usually about 10 - 20 years after first infection.-Symptoms and signs:...
. In general, pupils that “accommodate but do not react” are said to show light-near dissociation. A video of AR pupils and light-near dissociation is available here
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.
History
In the early 20th century, William John AdieWilliam John Adie
William John Adie MD Ed., FRCP was a British physician and neurologist known for describing the Adie syndrome and narcolepsy.-Biography:...
described a second type of pupil that could “accommodate but not react.” Adie’s tonic pupil is usually associated with a benign peripheral neuropathy (Adie syndrome
Adie syndrome
Adie syndrome, sometimes known as Holmes-Adie's syndrome or Adie's Tonic Pupil, is a neurological disorder characterized by a tonically dilated pupil. It is named after the British neurologist William John Adie...
), not with syphilis.
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. The near response in AR pupils is brisk and immediate. The near response in tonic pupils is slow and prolonged.
Pathophysiology
The two different types of near response are caused by different underlying disease processes. Adie's pupil is caused by damage to peripheral pathways to the pupil (parasympathetic neurons in the ciliary ganglionCiliary ganglion
The ciliary ganglion is a parasympathetic ganglion located in the posterior orbit. It measures 1–2 millimeters in diameter and contains approximately 2,500 neurons. Preganglionic axons from the Edinger-Westphal nucleus travel along the oculomotor nerve and form synapses with these cells...
that cause pupillary constriction to bright light and with near vision). The pathophysiologic mechanism which produces an Argyll Robertson pupil is unclear. Studies have failed to demonstrate a focal localising lesion. Research has implicated the rostral mid-brain in the vicinity of the cerebral aqueduct
Cerebral aqueduct
The mesencephalic duct, also known as the aqueductus mesencephali, aqueduct of Sylvius or the cerebral aqueduct, contains cerebrospinal fluid , is within the mesencephalon and connects the third ventricle in the diencephalon to the fourth ventricle in the mesencephalon, which is between the pons...
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 the Edinger-Westphal nucleus
Edinger-Westphal nucleus
The Edinger-Westphal nucleus is the accessory parasympathetic cranial nerve nucleus of the oculomotor nerve , supplying the constricting muscles of the iris...
(associated with the response to light) while sparing the fibres associated with the response to near, which lie slightly more ventrally.
The exact relationship between syphilis and the two types of pupils (AR pupils and tonic 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. 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.
Thompson and Kardon (2006) summarize the present view:
-
- 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.
-
- 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.
Parinaud syndrome
A third cause of light-near dissociation is Parinaud syndrome, also called dorsal midbrain syndrome. 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.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.
See also
- Adie syndromeAdie syndromeAdie syndrome, sometimes known as Holmes-Adie's syndrome or Adie's Tonic Pupil, is a neurological disorder characterized by a tonically dilated pupil. It is named after the British neurologist William John Adie...
- AnisocoriaAnisocoria-Causes:In the absence of the iris or eyeball proper, anisocoria is usually the result of a defect in efferent nervous pathways controlling the pupil traveling in the oculomotor nerve or the sympathetic pathways...
- CycloplegiaCycloplegiaCycloplegia is paralysis of the ciliary muscle of the eye, resulting in a loss of accommodation.-Anatomy:The iris is the heavily pigmented colored part of the eye. It has a contractile diaphragm in front of the lens with a central opening called the pupil...
- Marcus Gunn pupilMarcus Gunn pupilMarcus Gunn pupil is a medical sign observed during the swinging-flashlight test whereupon the patient's pupils constrict less when a bright light is swung from the unaffected eye to the affected eye...
- MiosisMiosisMiosis is the constriction of the pupil of the eye to two millimeters or less...
- Parinaud's syndromeParinaud's syndromeParinaud's Syndrome, also known as dorsal midbrain syndrome is a group of abnormalities of eye movement and pupil dysfunction. It is caused by lesions of the upper brain stem and is named for Henri Parinaud , considered to be the father of French ophthalmology...
- SyphilisSyphilisSyphilis is a sexually transmitted infection caused by the spirochete bacterium Treponema pallidum subspecies pallidum. The primary route of transmission is through sexual contact; however, it may also be transmitted from mother to fetus during pregnancy or at birth, resulting in congenital syphilis...
External links
- Illustration at health-pictures.com
- Illustration at mrcophth.com