Definition and Overview
Pupillary dysfunction is a condition in which pupil size control, pupillary light reflex, and near response appear abnormally due to abnormalities in the autonomic nervous system. The pupil is an organ that receives antagonistic control from the sympathetic and parasympathetic nerves and is used as a clinical window on the function of the autonomic nervous system.
Pupil size and reflex abnormalities appear as clinical signs of various neurological and systemic diseases rather than independent diseases. Pupillometry is a tool to noninvasively evaluate autonomic function, and its use in clinical research is gradually expanding.
Normal pupil control mechanism
Parasympathetic pathway (miosis)
Light stimulation → retinal photoreceptors → optic nerve (2nd cranial nerve) → pretectal nucleus → Edinger-Westphal nucleus → oculomotor nerve (3rd cranial nerve) → ciliary ganglion → pupillary sphincter contraction (miosis)
Sympathetic pathway (mydriasis)
Hypothalamus → Brainstem → Spinal cord (C8–T2, ciliospinal center of Budge) → Superior cervical ganglion → Long ciliary nerve → dilator pupillae muscle contraction (mydriasis)
Pupil size is determined by the relative activity of these two pathways, and dilatation occurs when the sympathetic nerve is dominant, and miosis appears when the parasympathetic nerve is dominant.
major clinical syndromes
Horner syndrome
Horner syndrome is a clinical triad that occurs due to blockage at any point in the sympathetic pathway.
main symptoms - Pupil narrowing (miosis): more evident in dark environments - Ptosis: Sagging of the upper eyelid (loss of Müller muscle function controlled by sympathetic nerves) - Anhidrosis: Decreased sweat secretion on one side of the face (depending on the location of the lesion)
Classification by cause - Primary neurons (hypothalamus-spinal cord): brainstem infarction, multiple sclerosis, cervical lesions - Secondary neurons (spinal cord-upper cervical ganglion): Pancoast tumor, neck surgery, thoracic aortic aneurysm - Third-order neurons (superior cervical ganglion-eye): internal carotid artery dissociation, cavernous sinus lesions
The location of the lesion is differentiated using the cocaine test and the hydroxyamphetamine test.
Adie's Tonic Pupil Syndrome
Eddy syndrome is caused by damage to the parasympathetic nerves of the ciliary ganglion or uniciliary nerve.
Key Features - Pupils are large (dilated) and light reflection is lost or very slow. - Near-range accommodative response also appears slowly (tonic near response) - Pupil constriction due to denervation hypersensitivity when instilled with 0.1% pilocarpine (diagnostic significance)
It mainly occurs in young women (20s to 40s), and when accompanied by loss of knee deep tendon reflexes, it is called Adie-Holmes syndrome.
Anisocoria
Pupillary anisocoria is a condition in which the difference in pupil size between the two sides is more than 0.4 mm.
- Physiological anisocoria: observed in approximately 20% of normal people, normal light reflection on both sides, size difference less than 1 mm
- Pathological anisocoria: When accompanied by abnormal light reflection, ptosis, or eye movement disorders, the cause needs to be determined.
Pupil abnormalities in autonomic diseases
Diabetic autonomic neuropathy
In diabetic autonomic neuropathy, pupil abnormalities can appear as an early indicator. The pupil dilation response in the dark is reduced, and the pupil cycle time is prolonged. Pupillary autonomic abnormalities are observed in approximately 20-30% of diabetic patients.
multiple system atrophy
In patients with multiple system atrophy (MSA), pupillary reflex abnormalities may appear as part of decreased autonomic function, and can be evaluated through pupillometry testing.
migraine
Abnormalities in pupil function are sometimes observed during migraine attacks, and abnormalities in autonomic nerve control have also been reported in the period between attacks.
diagnosis
clinical examination
- Direct light reflex: Whether or not the pupil constricts when light is irradiated
- Indirect light reflex (consensual reflex): reaction when light is illuminated in the opposite eye
- Near response: contraction when looking at a near object.
pharmacological test
| inspection | Purpose | |------|------| | Cocaine 0.1% | Confirmation of Horner syndrome (confirmation of loss of sympathetic nerve function) | | Hydroxyamphetamine 1% | Differentiating third-order neuron lesions | | Pilocarpine 0.1% | Confirmation of denervation hypersensitivity of Eddy's pupil | | Pyridostigmine | Differentiation of pupil abnormalities in myasthenia gravis |
Pupillometry
Using an infrared pupilometer, pupil diameter, constriction speed, recovery time, etc. are quantitatively measured. It is used as a non-invasive tool for evaluating autonomic function, and is used in clinical research to evaluate pain, sedation, and autonomic neuropathy.
treatment
Diagnosis and treatment of the cause of the pupillary dysreflexia themselves are priority rather than direct treatment of the pupil reflex abnormality itself.
- Horner Syndrome: Treatment of causative lesions (tumor, vascular lesion, dissociation)
- Eddy syndrome: Most cases require follow-up, and if visual discomfort occurs, consider instilling pilocarpine.
- Pupil abnormalities due to diabetic autonomic neuropathy: blood sugar control, neuroprotective treatment
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This information is provided for medical educational purposes and is not a substitute for individual medical care or treatment. If you have any symptoms, be sure to seek professional advice. Inquiries: Osang Neurosurgery 1599-5453 | osns.co.kr