Neurosurgery notes/Anatomy/Peripheral nerves anatomy/Autonomic nerves/Sympathetic/Horner syndrome

Horner syndrome

View Details
Status
Done
logo
Parent item
Sympathetic

Number

  • Pediatric
    • Incidence 1.42 per 100 000 patients
    • Birth prevalence of 1 in 6250 for those with a congenital onset.

Pathophysiology

  • Horner's syndrome results from a lesion to the sympathetic pathways that supply the head and neck, including the oculosympathetic fibers.

Anatomy

  • Pupillary
    • Dilation
      • Is mediated by a three-neuron sympathetic pathway that originates in the hypothalamus.
    • Constriction
      • CN3 parasympathetic (cholinergic) fibers
First order (central) neuron
  • Descends caudally from the hypothalamus to the first synapse in the cervical spinal cord (C8-T2 level-also called the ciliospinal center of Budge).
    • The descend in the brainstem is not clear which pathway is used as:
      • Pathologically if you get a lateral brainstem injury you get sympathetic injury causing Horner's
      • However from what I can find from the literature the two known pathways that transmit autonomic information from the hypothalamus to the brainstem/spinal cord is via (both midline structures
  • Aetiology
    • Lesions of the hypothalamus, brainstem and spinal cord
    • Stroke (classically the lateral medullary syndrome)
    • Demyelination (such as multiple sclerosis)
    • Neoplasms (such as glioma)
    • Syrinx (syringomyelia or syringobulbia)
Second order (preganglionic) neuron
  • Destined for the head and neck exits the spinal cord and travels in the cervical sympathetic chain through the brachial plexus, over the pulmonary apex and synapses in the superior cervical ganglion.
  • The superior cervical ganglion is located near the angle of the mandible and bifurcation of the common carotid artery.
  • Aetiology
    • Thoracic outlet (cervical rib, subclavian artery aneurysm),
    • Mediastinum (mediastinal tumors),
    • Pulmonary apex (Pancoast's tumor),
    • Neck
      • Thyroid malignancies
      • Cervical ICA dissection
    • Thoracic spinal cord (trauma)
    • Surgical procedures in this region
      • Radical neck dissection
      • Jugular vein cannulation
      • Thoracoscopy or mediastinoscopy
      • Chest tube placement
      • Other thoracic surgical procedures
Third order (postganglionic) neuron
  • The orbit enters the cranium within the adventitia of the internal carotid artery into the cavernous sinus.
  • The oculosympathetic fibers
    • Exit the ICA in close proximity to the trigeminal ganglion and the CN6 and join the 1st division of the trigeminal nerve to enter the orbit
    • The fibers (long ciliary nerve) innervate the dilator muscles of the iris and the smooth muscle (Müller’s muscle) in the upper and lower eyelid (inferior retractors).
  • The vasomotor and sudomotor fibers
    • Superior cervical ganglion → ECA → face
  • Etiology
    • Superior cervical ganglion (trauma, radical neck dissection or jugular vein ectasia)
    • Lesions of the internal carotid artery (ICA) in the neck and skull base (dissection, thrombosis, invasion by tumors or iatrogenic from endarterectomy or stenting, base of skull malignancies)
      • An internal carotid artery dissection.
        • Presentation
          • Neck pain
          • Oculosympathetic Horner syndrome (sweat fibers travel with the ECA and usually are not affected).
            • Horner syndrome
              • Ptosis
              • Miosis
              • No Anhydrosis here
              • Due to the location of the dissection (third-order neuron). Anhydrosis only occurs in first order neuron lesions.
          • CN XII deficit
          • TIA due to embolism or occlusion
          • SAH if it enters the dural space.
        • Imaging
          • The angiogram classically shows the string sign or a double-lumen.
        • Associated with
          • Fibromuscular dysplasia,
          • Cystic medial necrosis,
          • Ehler-Danlos syndrome,
          • Marfan syndrome,
          • Syphilis
        • Treatment
          • Anticoagulation therapy unless symptoms are progressing;
          • Direct surgical repair with stenting or bypass may be required.
    • Lesions of ICA in the cavernous sinus (thrombosis, aneurysm, inflammation or invasive tumors)
    • Lesions of the sellar and parasellar regions (invasive pituitary tumors, metastatic tumors, paratrigeminal tumors)
    • Other
      • Cluster headaches
 
A diagram of the head AI-generated content may be incorrect.

Localisation

  • Above or below the carotid bifurcation
    • For lesions of the sympathetic pathway that occur below the bifurcation of the carotid artery, the classic findings of Horner syndrome are
      • Ptosis,
      • Miosis: constriction of pupil
      • Anhydrosis.
      • There may also be apparent enophthalmos, as a result of the narrow palpebral fissure (an appearance that the affected eye is located deeper, “sunken in,” compared with the unaffected eye).
    • For lesions that occur above the carotid bifurcation, Horner syndrome comprises only
      • Ptosis
      • Miosis.
      • Anhydrosis is absent in lesions at the level of the internal carotid artery or above (e.g., carotid dissection) because sudomotor and vasomotor fibers to the face follow the external carotid artery at the bifurcation.
  • 3rd order vs 1st/2nd order neurons: Topical Hydroxyamphetamine/ cocaine
    • Is used to differentiate pre and postganglioninc Horner's.
    • Hydroxyamphetamine causes a release of norepinephrine from intact adrenergic nerve endings causing pupillary dilation.
    • One hour after instillation of 1% hydroxyamphetamine eye drops dilation of both pupils indicate a lesion of the 1st or 2nd order neuron.
    • If the smaller pupil fails to dilate it indicates a lesion of the 3rd order or postganglionic neuron.
  • Identification of the level of lesion in Horner syndrome (i.e., first neuron, second neuron, or third neuron) may usually be determined on clinical grounds.
    • First-neuron lesions
      • Accompanied by other signs of brain-stem involvement, such as long tract signs or cranial nerve signs.
    • Second-neuron lesions
      • Associated with chest surgery, chest trauma, or pulmonary neoplasms involving the sympathetic plexus.
    • Third-neuron lesions
      • Most common.
      • Caused by pathology in the neck, such as neck trauma, carotid vascular disease, or cervical bony abnormalities.

Aetiology

  • Postganglionic interruption (at or distal to the superior cervical ganglion) is commonly benign or idiopathic, but preganglionic or central oculosympathetic pareses are associated with malignancy in about half the cases
  • Unknown aetiology in 35-40% of cases
  • Anatomical location
  • Children
    • In children, trauma (birth trauma or neck trauma) is the most common cause of Horner’s syndrome.
  • Other causes
    • Other causes include surgical trauma, neuroblastoma, brainstem lesions (such as vascular malformations, glioma and demyelination) and carotid artery thrombosis.

Primary prevention

  • Prevention strategies depend on the etiology of Horner’s syndrome.
  • These may include prevention of trauma (especially head trauma), control of cardiovascular risk factors, and smoking cessation.

Diagnosis

  • Horner’s syndrome is a clinical diagnosis.
  • Pharmacological confirmation tests can be performed in subtle cases.

Presentation

  • Isolated Horner's:
    • The patient, an acquaintance, or a health care provider may notice a difference in the palpebral aperture or pupillary size.
    • Patients may also complain of ocular redness, nasal stuffiness and headache.
    • Children with isolated Horner's syndrome may present when parents notice a difference in eye color, pupil size, or impaired facial flushing.
  • Non-isolated Horner's
    • Horner's syndrome may accompany other neurologic or systemic deficits from disease processes listed above.

Examination

  • Horner’s syndrome can be established clinically by an ocular examination.
  • Ocular signs
    • Eyelids:
      • Patients have a mild (< 2 mm) ptosis of upper lid and inverse ptosis of the lower lid (lower lid rests at a higher level than normal), which produces a decreased palpebral aperture compared to the fellow eye.
    • Pupils:
      • Patients have anisocoria (difference in the pupillary size) with the ptotic eye having the smaller pupil (miosis). The anisocoria is more prominent in the dark, indicating pathology of the pupillary dilator. The smaller pupil takes a longer time to dilate when a bright source of light is moved away from the eye. This phenomenon is called dilation lag.
    • Iris heterochromia
      • Different coloured irides
      • May be seen in children with congenital Horner’s.
    • Extraocular movements
      • May be affected in lesions of the brainstem or the cavernous sinus.
    • Other signs of sympathetic denervation include ipsilateral conjunctival injection, changes in accommodation and lower intraocular pressure.
  • Neurologic signs
    • Neurologic signs may be present depending on the site of lesion
    • Brainstem (bulbar) signs:
      • Ataxia, diplopia, nystagmus, lateralized weakness or numbness, hoarseness and dysphagia.
    • Spinal cord (myelopathic) signs:
      • Sensory or motor abnormalities with a spinal cord level,
      • e.g. dysfunction of bowel or bladder movements, erectile dysfunction in men and spasticity.
    • Brachial plexopathy:
      • Pain and weakness in the arm, or hand; abnormalities can be confirmed by nerve conduction studies and electromyography of the involved extremity.
    • Cranial neuropathy
      • Single or multiple cranial nerves
      • Can be produced by lesions in the cavernous sinus or base of skull.
  • Other signs
    • Anhidrosis:
      • Variable degree of loss of sweating can be seen depending on the site of the lesion. Central or preganglionic lesions tend to produce more noticeable anhidrosis.
      • The sudomotor and vasomotor fibers to most of the face separate out at the superior cervical ganglion and anhidrosis is often not noticeable in postganglionic lesions.
    • Harlequin sign:
      • Impaired hemi-facial (or hemi-body) flushing seen in children with sympathetic denervation to the face.
    • Cervical or abdominal mass may be seen in children with neuroblastoma.

Clinical diagnosis

  • Horner’s syndrome is diagnosed clinically by observing ptosis (of upper and lower lids),
  • Miosis of the ptotic eye and demonstration of dilation lag in the affected eye,
  • Anhidrosis on the same side as the ptosis and/or mitosis.

Pharmacologic tests

  • Topical Cocaine
    • May be used to confirm Horner's syndrome in subtle cases.
    • Cocaine blocks reuptake of the neurotransmitter norepinephrine from the synaptic cleft and will cause dilation of the pupil with intact sympathetic innervation.
      • The eye with Horner does not have Norepi released into the cleft so even with reduced reuptake of Norepi the eye would not dilate
    • One hour after instillation of two drops of 10% cocaine
      • The normal pupil dilates more than the Horner's pupil, thus increasing the degree of anisocoria.
    • It is becoming increasingly difficult to obtain cocaine eye drops due to increased regulations.
  • Topical Apraclonidine
    • An alpha adrenergic agonist.
    • Result
      • Pupillary dilation in the Horner's pupil
        • Due to denervation supersensitivity
      • Mild pupillary constriction in the normal pupil
        • Presumably by down-regulating the norepinephrine release at the synaptic cleft.
    • A reversal of anisocoria after instilling two drops of 0.5% apraclonidine is suggestive of Horner's syndrome.
    • Be aware: you can get a false-negative result in acute cases of Horner's syndrome because upregulation of alpha-1 adrenergic receptors on the dilator papillae muscle is not present immediately after the injury (but is estimated to occur between 5-8 days).

Differential diagnosis

Anisocoria:
  • Distinguish Horner syndrome from simple anisocoria (normal pupillary asymmetry), check the pupillary light reflex.
    • If both pupils react normally to light, then the patient may have simple anisocoria.
    • Turn the lights off in the examining room to distinguish between these two possibilities.
      • If the smaller pupil is the abnormal one, then the anisocoria will become more pronounced when the lights are turned off.
      • A “dilatation lag” of the smaller pupils implies poor sympathetic tone and suggests the diagnosis of Horner syndrome.
ΤΟ DlSTlNGlJlSH ςιΜΡΙΕ ΑΝΙςοτ:ολΙΑ ΑΝΟ TiJRN 0FF ΤΗΕ LlGHTS ΙΝ ΤΗΕ EXAMlNlNG ROOM. 1F ΤΗΕ SMALlER ΡυΡΙΙ ις ΤΗΕ ABNORMAL ΟΝΕ. HORNER SYNOROME. ΤΗΕΝ ΤΗΕ ANlsocORlA, wlLl BECOME MORE PRONOUNCEO.
  • Essential anisocoria
  • Argyll-Robertson pupil
  • Chronic anterior uveitis
  • Pupillary sphincter tear
  • Unilateral use of miotics or mydriatics
Third nerve palsy
  • Horner syndrome ptosis is partial and disappears on looking up while CN3 palsy does not
Ptosis
  • Aponeurotic ptosis
  • Ocular myasthenia
  • Third nerve palsy (ptotic eye has the larger pupil)
  • Congenital ptosis
Neuron
Cause of Horner's
Associated Symptoms
First-order
CVA, MS, Vertebral artery dissection
Contralateral hemianesthesia, Contralateral hemiparesis, VI palsy, Wallenberg syndrome
Second-order
Schwannoma, Lung/breast tumor, Trauma/surgery, Epidural anesthetic
Hoarse voice, Cough, Scapular pain
Third-order
Carotid artery dissection, Neck trauma, Neck tumors/inflammation, Cluster headache, Raeder's paratrigeminal neuralgia, Cavernous sinus lesions
Pain, Reduced taste, Dysphagia, Palatal hemianesthesia, Headache, Involvement of III, IV, V, VI

Reference