Horner's Syndrome Flashcards
What is horner’s syndrome?
A condition that results from the disruption of the sympathetic nerves supplying the face resulting in a triad of:
- Ptosis
- Miosis
- Anhydrosis
- (and enophthalmos)
Summarise the pathophysiology of Horner’s syndrome
Damage to the oculosympathetic pathway, at the level of either:
- 1st order neurones
- 2nd order neurones
- 3rd order neurones
Describe the pathways of 1st - 3rd order neurones.
Damage to the oculosympathetic pathway, at the level of either:
-
1st order neurones
- hypothalamus –> synapes in spinal cord level T1
-
2nd order neurones
- spinal cord level T1 –> synapses in superior sympathetic ganglion of sympathetic chain
-
3rd order neurones
-
superior sympathetic ganglion of sympathetic chain –> travels along nerves that follow path of common carotid artery –> forms internal carotid plexus –> synapes at NMJ of:
- pupillary dilator muscles
- Muller’s muscle
- sweat glands
-
superior sympathetic ganglion of sympathetic chain –> travels along nerves that follow path of common carotid artery –> forms internal carotid plexus –> synapes at NMJ of:
What are some CENTRAL causes of Horner’s syndrome?
Causes can be divided according to presence & location of anhidrosis:
Central involving hypothalamospinal tract (anhidrosis of face, arm and trunk) - 1st order neurones
- Strokes
- tumours
- MS
- encephalitis
- lateral medullary syndrome
What are some PRE-GANGLIONIC causes of Horner’s syndrome?
Preganglionic (anhidrosis of face) - 2nd order neurones
- Pancoast tumor i.e. bronchogenic carcinoma on lung apex
- Thyroid carcinoma
- Thyroidectomy
- Goiter
What are some POST-GANGLIONIC causes of Horner’s syndrome?
Postganglionic (no anhidrosis) - 3rd order neurones
- Carotid artery dissection/carotid artery aneurysm
- Cluster headache
- Migraine –> episode of Horner’s –> relieved post-migraine
- Cavernous sinus thrombosis
- Otitis media
What are the presenting symptoms of Horner’s syndrome?
- Inability to open the eye fully on the affected side
- Loss of sweating on affected side
- Facial flushing
- Orbital pain/headache
- Other symptoms based on CAUSE
What are the signs of Horner’s syndrome O/E?
SPAM
- sympathetic fibres
- ptosis
- anhydrosis
- miosis
ipsilateral to side of sympathetic nerve damage
What are the primary investigations for ?Horner’s syndrome?
-
Cocaine drop test
- positive result = no dilation of pupil
-
Apraclonidine test
- positive result = dilation of pupil
-
Paredrine test
- helps to ascertain if lesion is on 3rd order neurone
- 3rd order neurone affected = no dilation of pupil
How does the cocaine drop test work?
Normal eye:
- Cocaine eyedrops block reuptake of post- ganglionic norepinephrine
- –> retention of norepinephrine in the synapse
- –> dilation of a normal pupil
BUT, in Horner’s syndrome:
- the lack of norepinephrine in the synaptic cleft
- –> mydriatic failure i.e. lack of dilation
What is paredrine?
- major metabolite of amphetamine
- drug that stimulates sympathetic nervous system
How does the paredrine test work?
If the 3rd order neuron (discharges norepinephrine into the synaptic cleft) is intact:
- amphetamine –> neurotransmitter vesicle release –> releases norepinephrine into synaptic cleft –> mydriasis of affected pupil.
If lesion is of the 3rd order neuron:
- amphetamine has no effect –> pupil remains constricted
How does the apraclonidine test work?
weaker form of norepinephrine
In Horner’s syndrome, the sympathetic innervation to pupillary dilator muscle is lost
- —> affected pupil = miotic
- –> pupillary dilator muscle responds to denervation by increasing α1 receptors
Apraclonidine is useful in this case due to:
- its weak α1-adrenergic properties.
- When applied to denervated (hyper-sensitive) pupillary dilator
- a super-normal dilatory response is generated
- –> pupil dilates to a more than it would it in a a non-denervated muscle
What are some secondary investigations that are conducted once a diagnosis of Horner’s syndrome is reached?
To find CAUSE of Horner’s syndrome:
- CXR - apical lung tumour
- CT/MRI - cerebrovascular accidents
- CT angiography - carotid artery dissection
How is Horner’s syndrome managed?
Horner’s syndrome is a sign not a disease in itself
- So, management depends on CAUSE
- (e.g. management for carotid dissection is very different to management of Pancoast’s tumours)
