What causes the absence of the pupillary reflex (pupillary light reflex)?

From the Guidelines

The absence of a papillary reflex is typically caused by damage to the neural pathways controlling pupil constriction or dilation, and common causes include brain injury, stroke, increased intracranial pressure, opioid overdose, certain medications, and neurological conditions like Adie's tonic pupil or third nerve palsy, as noted in the most recent study 1.

Causes of Papillary Reflex Absence

The causes of papillary reflex absence can be diverse and include:

• Brain injury
• Stroke
• Increased intracranial pressure
• Opioid overdose
• Certain medications, particularly anticholinergics
• Neurological conditions like Adie's tonic pupil or third nerve palsy
• Direct trauma to the eye
• Advanced glaucoma
• Complications of eye surgery

Importance of Immediate Medical Evaluation

When the papillary reflex is absent, it often indicates significant neurological dysfunction and requires immediate medical evaluation, as it may signal life-threatening conditions like brain herniation, as discussed in 1 and 1.

Diagnostic Approach

The diagnostic approach to a patient with an absent papillary reflex should include a comprehensive eye examination, with particular attention to sensorimotor exam, evidence of ptosis and anisocoria, and pupillary responses in bright and dim illumination, as recommended in 1. Neuroimaging, including MRI or CT scans, may be necessary to rule out compressive lesions or other underlying conditions, as suggested in 1 and 1.

Prognostic Value

The absence of a papillary reflex can have prognostic value, particularly in comatose patients after cardiac arrest, as noted in 1. However, the prognostic value of this sign should be considered in the context of other clinical findings and should not be used in isolation to predict poor neurologic outcome.

From the Research

Papillary Reflex Absence Causes

The absence of a papillary reflex can be caused by various factors, including:

• Traumatic brain injuries (TBI) 2
• Internal carotid artery dissection (ICAD) 3, 4, 5
• Horner's syndrome, which results from interruption of the sympathetic innervation to the eye 6
• Compression or stretching of the nerve by the expanded artery 4
• Interruption of the nutrient vessels supplying the nerve 4
• Direct compression of cranial nerves by a subadventitial haematoma in the parapharyngeal space 5
• Ischemic palsy by compression of the ascending pharyngeal artery 5

Related Conditions

Some conditions that may be related to the absence of a papillary reflex include:

• Third nerve palsy, which can be an extremely rare presentation of ICAD 3
• Lower cranial nerve palsies, which can occur in association with an ipsilateral spontaneous ICA dissection 4, 5
• Horner's syndrome, which can be a manifestation of ICAD or other conditions 6, 5