It is a rare condition that results from damage to the sympathetic nerve pathway (Oculosympathetic paresis), which controls functions like pupil dilation, eyelid elevation, and sweating on the face.
Clinical features-
• Miosis: due to loss of sympathetic supply
• Mild ptosis (drooping of upper lid): due to muller’s muscle paralysis [PYQ: NEET PG 2024]
• Enophthalmos (Posterior displacement of eyeball within orbit): Apparent / False
• Anhydrosis (loss of sweating): due to lesion before the superior cervical ganglion
• Absent ciliospinal reflex
Figure- Left sided Horner's syndrome
Note- Anhydrosis is absent in post superior cervical ganglion lesions (3rd order neuron).
Note- Horner syndrome is best described by - Ptosis + Miosis
Note- Lesion in sympathetic chain (Horner syndrome) is cause by both Congenital (Heterochromia iridis / Iris have different colors) and Acquired.
|
Lid retractor muscle |
Nerve supply |
|
LPS |
Oculomotor nerve (3rd cranial nerve) |
|
Muller muscle (2mm elevation) |
Sympathetic supply |
Horner's syndrome occurs due to a disruption in the sympathetic pathway (so no mydriasis), which can be categorized into three orders:
1. First-order neuron (Central): Originates in the hypothalamus and descends to the spinal cord at the level of T1.
2. Second-order neuron (Preganglionic): Travels from the spinal cord, exits at T1, and ascends to the superior cervical ganglion.
3. Third-order neuron (Postganglionic): Runs from the superior cervical ganglion to the eye muscles pupillary dilator muscle, Muller’s muscle) and face skin.
• 1st synapse - Ciliospinal centre of budge (C8, T1, T2)
• 2nd synapse - Superior cervical ganglion
|
Neuron |
Sympathetic Pathway |
Location of Lesion |
Hydroxyamphetamine Test (10%) Response |
|
1st order neuron (Central) |
Hypothalamus → Spinal cord (T1) |
- Brain stem disorders - Spinal cord injuries / tumors |
Dilation of the pupil (intact 3rd order neuron) |
|
2nd order neuron (Preganglionic) |
Spinal cord (T1) → Superior cervical |
- Lung tumors (Pancoast tumor) - Neck trauma - Carotid & Aortic aneurysm |
Dilation of the pupil (intact 3rd order neuron) |
|
3rd order neuron (Postganglionic) |
Superior cervical ganglion → Eye (pupillary dilator muscle, Muller’s muscle) and face skin |
- Atherosclerosis of ICA - Cavernous sinus lesions - Cluster headache - Nasopharyngeal tumors |
No dilation of the pupil (lesion in 3rd order neuron) |
Figure- Hydroxy amphetamine test
Hydroxy amphetamine test-
- It is helps to localize the lesion by assessing the integrity of the postganglionic neuron (3rd order neuron).
- Hydroxy amphetamine (10%) causes the release of norepinephrine (NE) from intact nerve terminals.
- If the 3rd order neuron is intact, hydroxy amphetamine will cause dilation of the pupil.
- If there is no dilation, it indicates that the lesion is in the 3rd order neuron.