Argyll Robertson pupils and light–near dissociation

Argyll Robertson pupils and light–near dissociation

DESCRIPTION

Arygll Robertson pupils are characterised by:

1.                  small pupils

2.                  absence of the pupillary light response

3.                  brisk accommodation reaction

4.                  bilateral involvement.

Light–near dissociation is defined as:

1.                  a normal accommodation response

2.                  a sluggish or absent pupillary light response.

Light–near dissociation is said to be present if the near pupillary response (tested in moderate light) exceeds the best pupillary response with a bright light source.⁹ Light–near dissociation is associated with Argyll Robertson pupils (classically, a sign of tertiary syphilis).

RELEVANT NEUROANATOMY AND TOPOGRAPHICAL ANATOMY

Accommodation and pupillary light pathways

AFFERENT STRUCTURES

·                            Retinal neuroepithelium

↓

·                            Optic nerve (CNII)

↓

·                            Pretectal nucleus midbrain

↓

·       Bilateral innervation of Edinger–Westphal nuclei

↓

EFFERENT STRUCTURES

·                            Visual cortex (accommodation only)

↓

·                            Accommodation area, visual cortex (accommodation only)

↓

·                            Pretectal nuclei, midbrain

↓

·                            Edinger–Westphal nuclei, midbrain

↓

·                            Oculomotor nerve (CNIII)

↓

·                            Ciliary ganglion

↓

·                            Short ciliary nerves

↓

·       Pupillary constrictor muscles

·       Ciliary muscle

·       Medial rectus muscles

CONDITION/S ASSOCIATED WITH

·                     Multiple sclerosis

·                     Neurosarcoidosis

·                     Tertiary syphilis

MECHANISM/S

Argyll Roberston pupils and light–near dissociation are caused by a pretectal lesion in the dorsal midbrain affecting the fibres of light reflex, which spare the fibres of the accommodation pathway that innervate the Edinger–Westphal nuclei

SIGN VALUE

Argyll Robertson pupils are classically a sign of tertiary syphilis. Tertiary syphilis is no longer the most common cause of light–near dissociation.