What is Horner's Syndrome (Horner Syndrome)?

From the Guidelines

Hornets Syndrome, also known as Horner's syndrome, is a neurological condition that requires immediate medical attention to identify and address the underlying cause, which may include stroke, tumor, trauma, or other conditions affecting the sympathetic chain, and management focuses on treating the root cause rather than the syndrome itself. The condition is characterized by a triad of symptoms: miosis (pupil constriction), ptosis (drooping eyelid), and anhidrosis (reduced sweating) on one side of the face. According to the most recent study 1, carotid and vertebral artery dissection can result in ischemic stroke or transient ischemic attack, often associated with neck pain or headaches, and occasional Horner syndrome in cases of carotid dissections.

Key Points to Consider

• The sympathetic pathway travels from the hypothalamus through the brainstem, spinal cord, and ultimately to the eye and face, with damage at any point potentially causing these characteristic symptoms.
• Treatment depends on identifying and addressing the underlying cause, which may include stroke, tumor, trauma, or other conditions affecting the sympathetic chain.
• Patients should seek immediate medical attention for proper diagnosis, which may involve imaging studies like MRI or CT scans and specialized eye tests such as cocaine or apraclonidine eye drop tests to confirm the diagnosis.
• The primary diagnostician should refer the patient for evaluation by indicated neurology or otolaryngology specialists, as stated in the adult strabismus preferred practice pattern 1.
• Initial treatment with prism may be helpful to manage diplopia while waiting for possible recovery, and botox, prism, or strabismus surgery may be considered for cases that do not resolve, as mentioned in the adult strabismus preferred practice pattern 1.

Important Considerations for Diagnosis and Management

• A complete ophthalmic examination with emphasis on the sensorimotor evaluation and completion of the three-step test and consideration of the upright-supine test should be performed.
• Careful checking for other neuro-ophthalmic signs and symptoms looking for Horner’s syndrome, cranial nerve palsy, INO, nystagmus, and hearing loss is essential.
• Fundus examination to check for papilledema or optic atrophy and visual field testing may provide additional information on the etiology.
• Abnormalities in the rostral pons and midbrain (e.g., INO) will result in contralateral hypotropia and head tilt, whereas abnormalities in the vestibular periphery, medulla, and more caudal pons will result in ipsilateral hypotropia and head tilt, as stated in the adult strabismus preferred practice pattern 1.

From the Research

Definition and Symptoms of Horner Syndrome

• Horner syndrome is a condition that results from an interruption of the oculosympathetic pathway, causing a slightly droopy upper lid and a smaller pupil on the affected side, as well as a deficiency of sweating over the brow or face on the affected side 2.
• The symptoms of Horner syndrome do not usually cause vision problems or other significant symptoms, but it is important as a warning sign that the oculosympathetic pathway has been interrupted, potentially with serious and even life-threatening processes 2.

Causes of Horner Syndrome

• The causes of Horner syndrome can be varied, including chest and neck tumors, stroke, and surgical procedures in the neck and chest 3.
• In some cases, the cause of Horner syndrome may be unknown, but the identification of the condition can be critical to the discovery of underlying conditions such as carotid dissection or tumor 3.
• The prevalence of causes of Horner syndrome depends on the accrual method, with procedures in the neck, chest, skull base, and paraspinal region accounting for most of the identified causes in pharmacologically-confirmed cases, and tumors being a common cause in pharmacologically-unconfirmed cases 3.

Diagnosis and Evaluation of Horner Syndrome

• The diagnosis of Horner syndrome can be difficult, as patients rarely present with the classic triad of ptosis, miosis, and anhydrosis, and the onset of anisocoria may be uncertain 4.
• A combined clinical, pharmacological, and imaging algorithm can be used to diagnose and evaluate Horner syndrome, including the use of cocaine, apraclonidine, and hydroxyamphetamine, as well as modern imaging modalities such as MRI and CT scans 4, 5.
• A careful physical examination and knowledge of the anatomy of the oculosympathetic pathway can help to narrow the differential diagnosis and evaluate patients with Horner syndrome 6.