Horner’s Syndrome

I’m pretty sure I get this when I haven’t slept enough…


Horner’s Syndrome

Definition: a triad of miosis, partial ptosis + apparent enophthalmos, and anhidrosis.

Image result for sympathetic supply of face hornersAetiology/ risk factor:

-Interruption of sympathetic innervation of the face.

Anatomy:

1st order central sympathetic fibres from the posterolateral hypothalamus ⇒ descend through midbrain and pons ⇒ terminate in the intermediolateral column of spinal cord at C8-T1 ⇒ 2nd order preganglionic pupillomotor fibres exist spinal cord at T1 ⇒ enter cervical sympathetic chain ⇒ ascend though sympathetic chain ⇒ synapse in superior cervical ganglion at level of carotid bifurcation (C3-4) ⇒ postganglionic, third order fibres exit superior cervical ganglion

⇒ vasomotor and sudomotor fibres branch off and travel along external carotid artery to innervate blood vessels and sweat glands

⇒postganglionic pupillomotor fibres ascend along the internal carotid artery to innervate the eye

Causes:

Interruption of the sympathetic supply at the level of:

1st order

Brainstem = demyelination, vascular disease (posterior circulation stroke)

Cervical Cord = syringomyelia, tumour (glioma)

2nd order

T1 root = brachial plexus lesion, neurofibromatosis (tumour along nerves)

Thoracic outlet/cervical sympathetic chain = pancoast tumour (lung apex)

3rd order

Internal carotid artery = dissection, occlusion (interruption of the sympathetic’s trip on the internal carotid artery into the skull and orbit)

Other: Migraine, cluster headaches

May be congenital or hereditary

Epidemiology: uncommon

Symptoms:

-symptoms of associated condition

e.g. lung cancer (pancoast tumour) cough, shortness of breath, haemoptysis

stroke- hemisensory loss, dysarthria, dysphagia, ataxia, vertigo, nystagmus

Signs:

Ipsilateral

-Ptosis- drooping of upper eyelid

-Apparent enophthalmos (sunken eye)

-Miosis- contracted pupil (still reactive to light)

-Anhidrosis- loss of sweating

Image result for horner's syndrome

Image result for horner's syndrome

-Iris heterochromia (affected eye hypopigmented)- may be seen in congenital Horner’s syndrome, Horner’s syndrome that occurs in children younger than 2, or long-standing Horner’s syndrome.

Investigations:

-The diagnosis may be clinical.

-Pharmacological testing can be helpful in diagnosis and can help identify the presence and level of an ocular sympathetic lesion.

Noradrenaline = sympathetic neurotransmitter

alpha-1 receptors = NA binds, receptors mediate sympathetic activity e.g. pupil dilation

alpha-2 receptors = NA binds, receptors stop more NA being released i.e. lessen sympathetic activity

       Topical apraclonidine test:

– little to no effect on normal pupil

– Horner’s = pupillary dilation + lid elevation on abnormal side and no response or mild pupil constriction on normal side

Apraclonidine = weak alpha-1 and strong alpha-2 agonist.

Dilation in Horner’s is due to upregulation of alpha-1 receptors, whilst slight constriction in normal eye is due to the alpha-2 agonist action, without the alpha-1 upregulation.

Topical cocaine test:

– intact sympathetic innervation leads to pupil dilation

– Horner’s syndrome, any level = dilates poorly to cocaine

Cocaine = indirect sympathomimetic agent, inhibits reuptake of noradrenaline.

Lack of response in Horner’s as there is sympathetic denervation and so there is not much noradrenaline to stop the reuptake of.

Topical hydroxyamphetamine test- helps to localise lesion

Hydroxyamphetamine = stimulates release of  stored noradrenaline from the postganglionic axon terminals into the neuromuscular junction at the iris dilator muscles.

-Horner’s syndrome with intact post-ganglionic fibres (1st or 2nd order lesions) = affected pupil dilates to equal or greater extent than the normal pupil

-Horner’s with damaged post-ganglionic fibres (3rd order lesion) = affected pupil does not dilate as well as normal pupil

-Investigations to find cause, if not known

CXR- pancoast lung tumour

CT head- stroke

MR angiography-internal carotid artery dissection (painful Horner’s syndrome)

Management:

-Manage cause, eradicate underlying disease process

e.g. neurosurgical care for aneurysm-related Horner’s syndrome, vascular surgery for carotid artery dissection

-In many cases, there is no effective treatment

Complications:

-Depend on cause

Prognosis:

-Depends on cause

References: Cheese & Onion, Medscape
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