Horner's Syndrome: Causes, Symptoms & Treatments

What is Horner's Syndrome?

Horner’s syndrome (also known as Bernard-Horner Syndrome or Oculosympathetic Palsy) is a rare medical condition that affects the eyes and parts of the face.

Horner syndrome is typically found in children and adolescents, occurring in about 1.42 out of 100,000 people below 19 years old.¹ 

What are the Symptoms of Horner's Syndrome? 

Horner’s syndrome is associated with three classic symptoms:

• Partial ptosis or blepharoptosis — Drooping of the upper eyelid in the affected eye
• Miosis — Constricted eye pupil where one appears smaller than the other
• Facial anhidrosis — Absence of sweating in the affected side of the face

Signs and symptoms may appear at birth, or they may show up at a later age. 

They usually affect one side of the face. But they can also affect both sides and cause bilateral symptoms like complete ptosis.²

Other Signs and Symptoms of Bernard-Horner Syndrome

Rare eye diseases such as Horner syndrome may produce uncommon symptoms such as:

• Heterochromia iridis — The affected iris will remain blue while the other iris will change to brown over time. This symptom typically occurs in congenital Horner’s syndrome, or if a child sustained a lesion before the age of 2.³ However, it can also occur in older patients with internal carotid artery hypoplasia.⁴
• Apparent enophthalmos — Sinking of the eyeball doesn’t occur with Horner’s syndrome. Instead, ptosis gives off the illusion of true enopthalmos.⁵

Other signs include conjunctival redness, decreased eye pressure, and changes in tear viscosity on the affected side of the body.

What Causes Horner's Syndrome?

Sympathetic nerves connect the brain to different parts of the body. The sympathetic nervous system (SNS) triggers involuntary actions in response to dangerous or stressful situations.

Some of these nerves — called the cervical ganglia — are connected to the eyes and face. They are responsible for facial sweating and the dilation (enlargement) of eye pupils.

When the impulses along these nerves are disrupted in some way, Horner syndrome develops.

Common causes include injury or impaired blood flow to the cervical ganglia or the presence of tumors and inflammation in surrounding areas.

More than half of cases (55%) are congenital or present at birth. Less than half (45%) are acquired at a later age.¹ Whether it is congenital or acquired, each is associated with different causes.

• Congenital Horner Syndrome — It is commonly caused by trauma or injury to the nerves or carotid artery during childbirth. However, it can also be hereditary or caused by a tumor called pediatric neuroblastoma.
• Acquired Horner Syndrome — It is usually caused by underlying health conditions affecting the neck, chest, lungs, or blood supply to the brain. 
• Idiopathic Bernard-Horner Syndrome — The causes are unknown. 36.5 percent of congenital Horner’s syndrome and 33 percent of acquired Horner’s syndrome have unknown etiology.¹

The 3 Types of Horner's Syndrome

The cervical ganglia has three nerve pathways. Depending on which pathway is affected, it can lead to one of three types of Bernard-Horner’s syndrome:⁶

1. First Order Horner’s Syndrome

Also known as Central Horner Syndrome, it affects the first order neurons (FON) found along the hypothalamus in the brain and the spinal cord. 

Possible causes include spinal cord lesions, impaired blood flow to the brain stem, and tumors in the hypothalamus.

2. Second Order Horner’s Syndrome

Also known as Preganglionic Horner Syndrome, it affects the preganglionic nerves along the chest, the top of the lungs, and the carotid artery in the neck. It may be caused by tumors or trauma in the upper lungs or chest cavity which can result from surgery or an accident.

3. Third Order Horner’s Syndrome

Also known as Postganglionic Horner Syndrome, it affects the postganglionic nerves which run across the neck, the middle ear, and the eye. 

Migraines, cluster headaches, middle ear infections, carotid artery lesions, and skull injuries may lead to this condition.

Is Horner's Syndrome Life-Threatening? 

Horner syndrome does not cause any significant effects on a person’s vision and overall health. However, it may be a sign of oculosympathetic nerve damage. 

Damage to this nerve may result from serious and sometimes life-threatening medical conditions.

Serious health problems that are associated with Horner’s syndrome include:

• Lung cancer
• Head injuries
• Trauma to the neck
• Infections
• Thyroid tumor
• Migraines
• Cluster headaches
• Stroke or aneurysm
• Brain embolism (blood clots)
• Carotid artery dissection

Malignant (cancerous) and benign tumors (noncancerous) around the cervical ganglia have also been linked to the development of Horner’s syndrome.

When to See a Doctor

You should see a doctor as soon as you notice signs. Horner’s syndrome may occur due to serious conditions, so you must get a prompt and accurate diagnosis.

Emergency care is needed if symptoms appear suddenly after a traumatic injury on the head or neck, or if the following signs accompany them:

• Impaired eyesight
• Dizziness
• Muscle weakness
• Sudden severe headache
• Severe neck pain

How is Horner's Syndrome Diagnosed?

A doctor may initially assess for signs of Horner’s syndrome and check for possible causes. 

In addition, they may perform a series of tests to confirm a positive diagnosis and identify the site of nerve damage.

Physical Exam

Diagnosis begins with the doctor conducting a physical examination. They will check for visible signs and symptoms of the condition. 

A physical eye exam usually includes checking for the following:

• Upper eyelid ptosis
• Lower eyelid or “upside-down” ptosis
• Pupil size (in dim and light conditions) and reaction time
• Unusual eye movements
• Visual field
• Facial sensation
• Microscopic examination of the pupils and iris

Patient History

Once the doctor confirms the presence of symptoms, they will review your medical history to see if they can trace its underlying causes. 

Obtaining a patient’s history will also help them identify where the lesions are located.

Test to Confirm Horner Syndrome

An ophthalmologist may use different eye drops to see how your pupils react. Pharmacologic tests can determine whether or not you have Horner’s syndrome and which type you have.

Tests may include:

Topical apraclonidine test

0.5% or 1% solution is applied to both eyes to confirm a Horner’s syndrome diagnosis. The affected side will respond with dilated pupils and elevation of the eyelid. Meanwhile, the healthy eye will not respond or experience mild miosis.

Topical cocaine test

2 to 10% cocaine is applied to both eyes and checked after 30 minutes. If the affected eye doesn’t dilate as much as the healthy eye, it confirms a diagnosis of Horner’s syndrome.

Tests to Identify the Site of Nerve Damage

A doctor may request pharmacologic and imaging tests to identify which type of Horner’s syndrome a person has and whether it is caused by a tumor, lesion, or structural abnormality.

Tests may include:

Topical hydroxyamphetamine test

1% solution is applied to both eyes to identify the location of nerve damage.

If the affected eye dilates in the same size as the healthy eye, it means that the postganglionic nerves are intact and that a person has first order or second order Horner’s syndrome. However, if the affected side doesn’t dilate as much as the healthy eye, it suggests postganglionic nerve damage and a diagnosis of third order Horner’s syndrome.

Imaging tests

These tests include X-rays, ultrasound, magnetic resonance imaging (MRI), and computed tomography (CT scan).

They usually check for the presence of tumors, lesions, and structural abnormalities. If there is a tumor, these tests can identify if it is cancerous or a benign tumor. Imaging of the neck is also ordered to rule out a carotid artery dissection, which can be life-threatening.

Treatment Options for Horner's Syndrome

According to the Genetic and Rare Diseases (GARD) Information Center, the treatment for Horner syndrome depends on the underlying cause. 

When appropriate, a doctor may recommend surgical interventions to alleviate conditions such as aneurysm, carotid artery dissection, and tumor growths.

What is the Recovery Rate/Outlook? 

The prognosis of Horner’s syndrome depends on the causative factors. While the condition itself won’t affect your eyesight or quality of life, there may be a severe and life-threatening condition causing it that requires immediate treatment.