Symptoms appearing when the sympathetic trunk nerve group is damaged, mostly ocular.Encyclopedia Entry for Horner Syndrome :Horner syndrome. Horner syndrome can be caused by any interruption in a set of nerve fibers that start in the part of the brain called the hypothalamus and travel to the face and eyes. These nerve fibers are involved with sweating, the pupils in your eyes, and the upper and lower eyelid muscles. Damage of the nerve fibers can result from: Injury to the carotid artery, one of the main arteries to the brain Injury to nerves at the base of the neck called the brachial plexus Migraine or cluster headaches Stroke , tumor, or other damage to a part of the brain called the brainstem Tumor in the top of the lung, between the lungs, and neck Injections or surgery done to interrupt the nerve fibers and relieve pain (sympathectomy) Spinal cord injury In rare cases, Horner syndrome is present at birth. The condition may occur with a lack of color (pigmentation) of the iris (colored part of the eye).Symptoms of Horner syndrome may include: Decreased sweating on the affected side of the face Drooping eyelid ( ptosis ) Sinking of the eyeball into the face Different sizes of pupils of the eyes ( anisocoria ) There may also be other symptoms, depending on the location of the affected nerve fiber. These may include: Vertigo (sensation that surroundings are spinning) with nausea and vomiting Double vision Lack of muscle control and coordination Arm pain, weakness and numbness One sided neck and ear pain Hoarseness Hearing loss Bladder and bowel difficulty Overreaction of the involuntary (autonomic) nervous system to stimulation ( hyperreflexia ).The health care provider will perform a physical exam and ask about the symptoms. An eye exam may show: Changes in how the pupil opens or closes Eyelid drooping Red eye Depending on the suspected cause, tests may be done, such as: Blood tests Blood vessel tests of the head ( angiogram ) Chest x-ray or chest CT scan MRI or CT scan of the brain Spinal tap (lumbar puncture) You may need to be referred to a doctor who specializes in vision problems related to the nervous system (neuro-ophthalmologist).Treatment depends on the underlying cause of the condition. There is no treatment for Horner syndrome itself. Ptosis is very mild and in rare cases affects vision in Horner syndrome. This can be corrected by cosmetic surgery or treated with eyedrops. The provider can tell you more.The outcome depends on whether treatment of the cause is successful.There are no direct complications of Horner syndrome itself. But, there may be complications from the disease that caused Horner syndrome or from its treatment.Call your provider if you have symptoms of Horner syndrome.Oculosympathetic paresis.Central nervous system Central nervous system and peripheral nervous system.Balcer LJ. Pupillary disorders.