Horner’s syndrome is a combination of signs that appears when the sympathetic nerves running to the eye are disrupted. It usually does not reduce vision on its own, but it often becomes the first signal of another, more important condition. That is why any new case of Horner’s syndrome requires finding the underlying cause.
What Horner’s syndrome is
A long chain of nerve fibres — the sympathetic pathway — runs to the eye and eyelid. It begins in the brain, descends toward the chest, curves around the top of the lung, rises along the carotid artery in the neck and ends near the eye. These nerves slightly lift the eyelid, widen the pupil in the dark and control sweating on the face. If the pathway is damaged at any point, characteristic changes appear on one side of the face. This is Horner’s syndrome. Importantly, it is not a separate disease but a consequence of something interrupting this nerve chain.
Causes
- A tumour at the top of the lung pressing on the nerve fibres.
- Dissection of the carotid artery — a dangerous condition that may be an emergency.
- Impaired blood flow or a tumour in the brainstem.
- Diseases or injuries of the neck, surgery on the thyroid gland or carotid artery.
- Nerve damage during childbirth (in children).
- Sometimes no cause can be found — then observation is needed.
Symptoms
- Ptosis — slight drooping of the upper eyelid on one side, the eye looks “squinted”.
- Miosis — a constricted pupil on the affected side; the pupils become different in size (pupil asymmetry), especially noticeable in dim light.
- Anhidrosis — reduced or absent sweating on the corresponding half of the face.
- Sometimes — a slight “sinking” of the eye, redness or a feeling of stuffiness on that half of the face.
Why this is a neuro-ophthalmological condition
Horner’s syndrome is above all an important marker. The pupil and eyelid “tell” the doctor about the state of the nerves along the whole path from the brain to the eye. Assessing these signs, comparing them with other symptoms and deciding exactly where to look for the cause is the work of a neuro-ophthalmologist — a doctor working at the border of ophthalmology and neurology. It is this specialist who distinguishes harmless variants from those that require urgent examination.
Diagnosis
- Examination and comparison of the pupils and eyelids under different lighting.
- Pharmacological pupil tests — instilling special drops whose reaction confirms Horner’s syndrome and suggests the level of damage.
- Imaging of the sympathetic pathway — MRI or CT of the brain, neck and chest.
- Examination of the neck vessels (carotid arteries) when their dissection is suspected.
- If needed — consultations with a neurologist, vascular surgeon or other specialists.
Treatment
There is usually no separate treatment for “the ptosis or miosis itself” in Horner’s syndrome — the cause that produced it is treated. If it is a tumour, an artery dissection or inflammation, the doctor directs efforts specifically at the underlying disease. So the main task is not to “remove” the outward signs but to find out why they appeared. Once the cause is dealt with, the signs may partly or fully diminish. In some cases, a residual mild ptosis can later be corrected if the patient wishes.
When to seek help urgently
A sudden Horner’s syndrome combined with pain in the neck, back of the head or head, dizziness or speech disturbance is especially dangerous. Such a combination may mean a dissection of the carotid artery and requires emergency care to rule out the threat of a stroke. Do not wait — seek medical help as soon as possible.
German Eye Clinic, phone 0 800 507 670, the “Neuro-ophthalmologist consultation” service page.
