Horner syndrome
Horner syndrome is a neurological condition characterized by a collection of symptoms resulting from damage to the sympathetic nerves controlling the muscles of the eye. This syndrome can be caused by various factors, including tumors, trauma, or other medical conditions affecting the nervous system. Common symptoms include drooping of the upper eyelid, swelling of the lower eyelid, and a constricted pupil in the affected eye. The condition typically manifests only on one side of the face and can sometimes lead to noticeable differences in eye color in congenital cases.
Diagnosis is usually conducted by an ophthalmologist through specific tests, such as using a cocaine solution to determine the functionality of the sympathetic nerve. Imaging techniques like MRI or CT scans may be employed to identify underlying causes such as tumors. While there’s no direct treatment for Horner syndrome itself, addressing the underlying cause, especially in cases related to cancer, is crucial for management. The prognosis largely depends on the reason behind the neural damage. Horner syndrome is relatively uncommon, affecting about one in every 6,000 individuals in the general population.
On this Page
Horner syndrome
ALSO KNOWN AS: Horner’s syndrome
RELATED CONDITIONS: Neuroblastoma, of the lung
DEFINITION: Horner syndrome is not a disease, but it is a collection of symptoms caused by damage to a nerve that controls the muscles of the eye. Horner syndrome has many causes, some of which are related to tumor growth.
Risk factors: Risk factors for developing Horner syndrome vary and are related to the risk factors for developing the underlying disease that causes Horner syndrome symptoms.
Etiology and the disease process: Horner syndrome is a disorder of the eye named for William Edmonds Horner, a Virginia physician who developed an operation to correct some of the symptoms associated with the syndrome. To understand the syndrome and how it is related to cancer, it is necessary to understand some information about the nervous system.
The nervous system has two divisions. The voluntary nervous system consists of nerves that are under conscious control. These nerves control actions such as turning the head or raising the arm. The involuntary, or autonomic, nervous system controls muscle movements that are not under conscious control. The regulates activities such as breathing, digesting food, and the contraction and dilation (expansion) of the pupil of the eye.
The autonomic nervous system has two divisions: the sympathetic and the parasympathetic nervous systems. Stimulation of the sympathetic nerves prepares the body for action by doing things such as moving more blood to the skeletal muscles. Stimulation of the parasympathetic nervous system calms the body by doing things such as allowing muscles to relax.
The eye contains both sympathetic and parasympathetic nerves. Normally, these two nervous systems balance each other. In Horner syndrome, the sympathetic nerve to the eye is damaged. As a result, there is only parasympathetic stimulation; the upper eyelid droops, the lower eyelid swells, and the pupil remains small and does not dilate. These changes occur only in one eye.
The sympathetic nerve that is damaged in people with Horner syndrome does not go directly from the brain to the eye. It has a three-step path, and in each stage, different events can cause Horner syndrome. In the first step, the nerve starts in the brain and goes down the spinal cord to the chest. Damage to this part of the pathway (called first-neuron Horner syndrome) can be caused by brain tumors, by a tumor of the pituitary gland (an organ at the base of the brain), or by a brief interruption in blood flow to the brain (a transient ischemic attack, or TIA).
The next part of the pathway takes the nerve from the chest over the top of the lungs and up along the carotid artery in the side of the neck. Damage to the nerve in this part of the pathway (called second-neuron Horner syndrome) can be caused by a tumor in the upper part of the lung (a Pancoast tumor) or a tumor in the chest cavity (thoracic tumor). Noncancerous causes include trauma to the chest cavity or neck (either from surgery or an accident), an enlarged thyroid gland, and spinal cord injury or disease.
In the final part of the pathway, the nerve goes from the neck through the middle ear and into the eye. Damage to the nerve in this part of the pathway (called third-neuron Horner syndrome) has noncancerous causes such as injury to the skull, middle-ear infections, and migraine or cluster headaches.
Symptoms similar to Horner syndrome can also be caused by various drugs, including some antipsychotics, anesthetics, and drugs used for treating Parkinson’s disease.
Incidence: The incidence of Horner syndrome is not known, but the syndrome is uncommon. One study reported the incidence of congenital Horner syndrome as occurring in one out of every 6,250 births. Within the general population, one out of every 6,000 people has Horner syndrome.
Symptoms: Symptoms include a drooping upper eyelid and a puffy lower eyelid. The eyeball may appear sunken. The pupil of the affected eye is smaller than the pupil of the healthy eye. Children with congenital Horner syndrome (caused by nerve-cell tumors) often have eyes that are different colors. People who have third-neuron Horner syndrome do not sweat from the affected side of the face.
Screening and diagnosis: An ophthalmologist (eye specialist) usually diagnoses Horner syndrome. A few drops of a solution containing a small amount of cocaine are put in the affected eye. If the sympathetic nerve to the eye is undamaged, then the pupil will dilate (enlarge). If there is damage, pupil size remains unchanged. Other drugs, such as apraclonidine or hydroxyamphetamine, help confirm the diagnosis. Following diagnosis, imaging scans (such as magnetic resonance imaging, computed tomography, ultrasound) are done to locate tumors that may be the source of the damage. In the 2020s, targeted imaging technologies advanced to better doctors' abilities to locate and treat nerve damage.
Treatment and therapy: There is no specific treatment for Horner syndrome. Treatment varies depending on the underlying cause of the symptoms. In cancer-related cases, this means diagnosing and treating the specific cancer.
Prognosis, prevention, and outcomes: Prognosis and outcome depend on the cause of the syndrome.
Bibliography
Davagnanam, I., et al. "Adult Horner's Syndrome: A Combined Clinical, Pharmacological, and Imaging Algorithm." Eye, vol. 27, 2013, pp. 291–98.
“Horner Syndrome - Diagnosis & Treatment.” Mayo Clinic, 13 May 2022, www.mayoclinic.org/diseases-conditions/horner-syndrome/diagnosis-treatment/drc-20373551. Accessed 13 June 2024.
“Horner Syndrome: What It Is, Causes, Symptoms & Treatment.” Cleveland Clinic, 4 Nov. 2022, my.clevelandclinic.org/health/diseases/17836-horners-syndrome. Accessed 13 June 2024.
Icon Health. Horner’s Syndrome: A Medical Dictionary, Bibliography, and Annotated Research Guide to Internet References. San Diego: Icon Health, 2004.
Zalan, Khan. “Horner Syndrome - StatPearls.” NCBI, 10 Apr. 2023, www.ncbi.nlm.nih.gov/books/NBK500000. Accessed 13 June 2024.
Lee, Jeong Hyun., et al. “Neuroimaging Strategies for Three Types of Horner Syndrome with Emphasis on Anatomic Location.” American Journal of Roentgenology, vol. 188.1, 2007, pp. W74–W81.
Moreno, Tomas A., et al. "Isolated Horner Syndrome and Syringomyelia in a Child." Journal of American Association for Pediatric Ophthalmology and Strabismus, vol. 16.6, 2012, pp. 569–70.
Rabady, David Z. “Pediatric Horner Syndrome: Etiologies and Roles of Imaging and Urine Studies to Detect Neuroblastoma and Other Responsible Mass Lesions.” American Journal of Ophthalmology, vol. 144.3, 2007, pp. 481–82.