Horner syndrome


00:00 / 00:00



Horner syndrome


Central nervous system disorders

Spina bifida

Chiari malformation

Dandy-Walker malformation


Tethered spinal cord syndrome

Aqueductal stenosis

Septo-optic dysplasia

Cerebral palsy

Spinocerebellar ataxia (NORD)

Transient ischemic attack

Ischemic stroke

Intracerebral hemorrhage

Epidural hematoma

Subdural hematoma

Subarachnoid hemorrhage

Saccular aneurysm

Arteriovenous malformation

Broca aphasia

Wernicke aphasia

Wernicke-Korsakoff syndrome

Kluver-Bucy syndrome

Concussion and traumatic brain injury

Shaken baby syndrome


Febrile seizure

Early infantile epileptic encephalopathy (NORD)

Tension headache

Cluster headache


Idiopathic intracranial hypertension

Trigeminal neuralgia

Cavernous sinus thrombosis

Alzheimer disease

Vascular dementia

Frontotemporal dementia

Lewy body dementia

Creutzfeldt-Jakob disease

Normal pressure hydrocephalus


Essential tremor

Restless legs syndrome

Parkinson disease

Huntington disease

Opsoclonus myoclonus syndrome (NORD)

Multiple sclerosis

Central pontine myelinolysis

Acute disseminated encephalomyelitis

Transverse myelitis

JC virus (Progressive multifocal leukoencephalopathy)

Adult brain tumors

Acoustic neuroma (schwannoma)

Pituitary adenoma

Pediatric brain tumors

Brain herniation

Brown-Sequard Syndrome

Cauda equina syndrome

Treponema pallidum (Syphilis)

Vitamin B12 deficiency


Friedreich ataxia

Neurogenic bladder


Neonatal meningitis


Brain abscess

Epidural abscess

Cavernous sinus thrombosis

Creutzfeldt-Jakob disease

Central and peripheral nervous system disorders

Sturge-Weber syndrome

Tuberous sclerosis


von Hippel-Lindau disease

Amyotrophic lateral sclerosis

Peripheral nervous system disorders

Spinal muscular atrophy


Guillain-Barre syndrome

Charcot-Marie-Tooth disease

Trigeminal neuralgia

Bell palsy

Winged scapula

Thoracic outlet syndrome

Carpal tunnel syndrome

Ulnar claw

Erb-Duchenne palsy

Klumpke paralysis


Myasthenia gravis

Lambert-Eaton myasthenic syndrome

Autonomic nervous system disorders

Orthostatic hypotension

Horner syndrome

Nervous system pathology review

Congenital neurological disorders: Pathology review

Headaches: Pathology review

Seizures: Pathology review

Cerebral vascular disease: Pathology review

Traumatic brain injury: Pathology review

Spinal cord disorders: Pathology review

Dementia: Pathology review

Central nervous system infections: Pathology review

Movement disorders: Pathology review

Neuromuscular junction disorders: Pathology review

Demyelinating disorders: Pathology review

Adult brain tumors: Pathology review

Pediatric brain tumors: Pathology review

Neurocutaneous disorders: Pathology review


Horner syndrome


0 / 12 complete

USMLE® Step 1 questions

0 / 2 complete

High Yield Notes

3 pages


Horner syndrome

of complete


USMLE® Step 1 style questions USMLE

of complete

A 72-year-old man comes to his primary care physician to evaluate right-sided vision changes over six months. The patient also has noted an increase in swelling in his right upper arm.  Past medical history is significant for myocardial infarction and hyperlipidemia. The patient has a 30 pack-year smoking history. He has a droopy right eyelid and intact extraocular eye movements on examination. Pupils are asymmetric in dim light – 2 mm on the right and 4 mm on the left, with both reactive to light. The pupils become more symmetric in bright light. The skin on the right half of his face appears cracked and dry. Which of the following is the most likely etiology of this patient’s right eye droop?

External References

First Aid









Horner syndrome p. 559, 719

Brown-Séquard syndrome p. 549

Horner syndrome p. 549

Horner syndrome p. 530, 536, 559

labs/findings p. 723

lung cancer p. 709

Pancoast tumor p. 710

presentation p. 719


Horner syndrome p. 549, 719

Pancoast tumor p. 710

Horner syndrome and p. 559

Ptosis (eyelids)

Horner syndrome p. 560, 719

Syringomyelia p. 506

Horner syndrome p. 559



Filip Vasiljević, MD

Brittany Norton, MFA

Evan Debevec-McKenney

Tanner Marshall, MS

Horner’s syndrome, named after the ophthalmologist Johann Friedrich Horner, is caused by a problem with the sympathetic nerve supply to one side of the face.

This disruption results in miosis, which is constricted pupil; ptosis, a droopy eyelid; and anhidrosis, a failure to sweat.

Broadly speaking, the autonomic nervous system is a part of the nervous system that controls involuntary body functions like the heart rate, blood pressure and digestion.

The autonomic nervous system can be subdivided into the sympathetic and parasympathetic nervous system, which have opposite effects.

The sympathetic nervous system controls functions like increasing heart rate, blood pressure, and slowing digestion. All of this maximizes blood flow to the muscles, and can help you either run away from a threat or fight it which is why it’s also called the fight-or-flight response.

The parasympathetic nervous system has the opposite effect; it slows heart rate, decreases blood pressure, and stimulates digestion - the effects can be summarized as 'rest and digest'.

Now, with regard to the face and eye, there’s an oculosympathetic pathway with three groups of neurons called first-order, second-order and third-order neurons.

The body of the first-order neuron is located in the hypothalamus, and it’s axon extends down into the spinal cord, where it synapses with the second-order neuron.

The body of the second-order neuron is located in the cervical region of the spinal cord, and it’s axon exits the spinal cord and enters the sympathetic chain, which is a structure full of sympathetic ganglions or nerve cell bodies, and it runs along both sides of the spine.


Horner syndrome is a neurological disorder characterized by the combination of three main symptoms: ptosis (drooping eyelid), miosis (constricted pupil), and anhidrosis (lack of sweating on one side of the body).

Most cases of horner syndrome are caused by damage to the sympathetic nervous system, which can be due to a stroke, tumor, or injury. Less common causes include infections, autoimmune disorders, and medications. Some people also develop horner syndrome as a side effect of cancer treatment.


  1. "Robbins Basic Pathology" Elsevier (2017)
  2. "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
  3. "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
  4. "CURRENT Medical Diagnosis and Treatment 2020" McGraw-Hill Education / Medical (2019)
  5. "Enophthalmos Is Not Present in Horner Syndrome" PLoS Medicine (2005)
  6. "Neuroimaging Strategies for Three Types of Horner Syndrome with Emphasis on Anatomic Location" American Journal of Roentgenology (2007)

Copyright © 2023 Elsevier, except certain content provided by third parties

Cookies are used by this site.

USMLE® is a joint program of the Federation of State Medical Boards (FSMB) and the National Board of Medical Examiners (NBME). COMLEX-USA® is a registered trademark of The National Board of Osteopathic Medical Examiners, Inc. NCLEX-RN® is a registered trademark of the National Council of State Boards of Nursing, Inc. Test names and other trademarks are the property of the respective trademark holders. None of the trademark holders are endorsed by nor affiliated with Osmosis or this website.