Dr Ben Wild
Overview |
The iris, the colored part of our eyes, contains 2 muscles. One, the sphincter, is controlled by the parasympathetic nervous system and the other, the dilator, is controlled by the sympathetic nervous system. The interplay between these muscles controls the size of the opening in the middle of the iris known as the pupil.
A frontal view of a healthy eye.
Horner syndrome is a condition that is usually unilateral whereby the sympathetic nervous system pathway is disrupted. In rare cases it may be bilateral when caused by issues like diabetes. There is a 3-link chain in this sympathetic nervous system pathway and if either of these links are severed, it results in a small pupil, a droopy eyelid, and the loss of the ability to sweat on that side of the face. One can be born with this condition.
A frontal view of an eye with Horner Syndrome showing a small pupil even in dim light and a droopy eyelid.
The first link is a neuron connecting the hypothalamus (brain) to the spinal cord. Issues such as diabetes, stroke, brain tumors, spinal cord tumors, Multiple Sclerosis, and more can cause this. The second goes from the spinal cord to the cervical ganglia located just outside the spinal cord. Issues like apical lung tumors aortic or carotid aneurysms and neck trauma can cause this. The third goes from the cervical ganglia up the internal carotid artery and into the eye. Issues like trauma, pituitary tumors, carotid artery issues, jugular vein issues, aneurysms, and inflammation can cause this.
Signs and Symptoms |
Signs
Different sized pupils (unless bilateral), droopy eyelid, loss of the ability to sweat on the affect side of the head, lighter iris if born with the condition.
Symptoms
Pain if due to a cause located in the neck (carotid or jugular issues).
Causes and Risk Factors |
Causes
Loss of sympathetic nerve supply to the affect eye.
Risk Factors
Brain tumors, brain aneurysms, spinal cord tumors, carotid aneurysms, jugular vein issues, inflammation, diabetes, trauma, MS, strokes, lung tumors, surgery.
Prevention and Treatment |
Prevention
Regular check ups with a family doctor to catch any health conditions early and live a healthy lifestyle to avoid vascular conditions like diabetes.
Treatments commence after determining the cause of the Horner’s pupil via CT/MRI scans.
· Surgery to remove the lesion.
· Apraclonidine drops to dilate the affected pupil (depends on which neuron is not working).
Prognosis |
Horner syndrome can be a sign of a life-threatening condition and must be taken seriously. If it presents acutely (suddenly), it necessitates an immediate visit to the emergency room. If it has been slowly appearing over the course of a year, it still necessitates investigation but is not an emergency. The eye symptoms are not typically bothersome and do not require treatment.