The Causes of Argyll Robertson Pupil: A Comprehensive Review

Argyll Robertson pupil is a rare neurological disorder characterized by abnormal pupillary response to light and accommodation. The condition is often associated with Parinaud's syndrome, a complex disorder that affects the brain's ability to control eye movements and other functions. In this article, we will delve into the causes of Argyll Robertson pupil and explore the underlying pathophysiology of Parinaud's syndrome.

The pretectal nucleus receives afferent projections from the retina and optic nerve via optic tract fibers that bypass the lateral geniculate body. This unique pathway is responsible for the pupillary constriction response to light, which is impaired in patients with Parinaud's syndrome. However, the pupillary constriction response to convergence and accommodation remains preserved.

In Parinaud's syndrome, the compression of the superior cerebellar peduncle causes ataxia, while damage to the oculomotor nerve, particularly the levator palpebrae portion, leads to ptosis. The compression of the posterior commissure and pretectal area can also cause pseudo-Argyll Robertson pupils, which constrict to accommodation and have a slight response to light.

The visual field defects in Parinaud's syndrome are a consequence of chronic papilledema that causes optic neuropathy. Blurry vision is related to accommodation problems, while diplopia is mainly due to involvement of the trochlear nerve (IVth cranial nerve). In some cases, patients with Parinaud's syndrome may conserve a slight response to light due to an additional pathway involving attention to a conscious bright/dark stimulus.

In contrast, Argyll Robertson pupils do not respond to a light stimulus. The distinction between pseudo-Argyll Robertson pupils and true Argyll Robertson pupils lies in their pupillary response to light and accommodation. Pseudo-Argyll Robertson pupils constrict to accommodation and have a slight response to light, whereas true Argyll Robertson pupils show no response to either.

The investigation of the pathophysiology related to the signs and symptoms of Parinaud's syndrome has revealed that the disorder involves dysfunction of the structures of the dorsal midbrain. Specifically, the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF), interstitial nucleus of Cajal (iNC), and posterior commissure are disrupted in patients with upward gaze palsy.

In conclusion, the causes of Argyll Robertson pupil are complex and multifaceted. The disorder is often associated with Parinaud's syndrome, which involves dysfunction of the structures of the dorsal midbrain. A comprehensive understanding of the pathophysiology of Parinaud's syndrome is essential for effective diagnosis and management of this rare neurological disorder.

Causes of argyll robertson pupil