Causes of horner syndrome
Horner syndrome is caused by damage to a certain pathway in the sympathetic nervous system. The sympathetic nervous system regulates heart rate, pupil size, perspiration, blood pressure and other functions that enable you to respond quickly to changes in your environment. The nerve pathway affected by Horner syndrome is divided into three groups of nerve cells (neurons). First-order neurons This neuron pathway leads from the hypothalamus at the base of the brain, passes through the brainstem and extends into the upper portion of the spinal cord. Problems in this region that can disrupt nerve function related to Horner syndrome include: Stroke Tumor Diseases that cause the loss of the protective sheath on neurons (myelin) Neck trauma Cyst in the spinal column (syringomyelia) Second-order neurons This neuron path extends from the spinal column, across the upper part of the chest and into the side of the neck. Causes related to nerve damage in this region may include: Lung cancer Tumor of the myelin sheath (schwannoma) Damage to the main blood vessel leading from the heart (aorta) Surgery in the chest cavity Traumatic injury Third-order neurons This neuron path extends along the side of the neck and leads to facial skin and muscles of the iris and eyelids. Nerve damage in this region may be associated with the following: Damage to the carotid artery along the side of the neck Damage to the jugular vein along the side of the neck Tumor or infection near the base of the skull Migraines Cluster headaches, a disorder that results in cyclical patterns of severe headaches