Horner syndrome results from disruption of the sympathetic nerve supply to the eye. It is characterized by three key signs: ptosis, miosis, and anhidrosis. The syndrome can be classified based on where along the sympathetic pathway the disruption occurs. Testing involves confirming the diagnosis with apraclonidine, which causes reversal of miosis and ptosis in denervated eyes. Investigations depend on classification and may include imaging of the brain, cervical spine, chest, or neck vessels to identify underlying causes.

1. Horner syndrome
Dr. Jwan Ali Ahmed AlSofi

2. Contents:-
• Definition
• Neuroanatomy
• Clinical presentation
• Pathophysiology
• Causes
• Classification
• Investigation

3. Definition:-
• Horner’s syndrome is the clinical picture resulting
from dysfunction of sympathetic nerve supply to
the eye.
• Most commonly is acquired.
• The congenital or familial form exists, often
associated with lack of pigmentation of the iris. The
lesion site is unknown.

4. Anatomy:-
Sympathetic nerve supply originates in the
hypothalamus and emerges in the root of the neck
before innervating the pupil:
• Posterior hypothalamus ( 1st order neuron) 
ciliospinal center of Budge C8-T2 ( 2nd order neuron,
preganglionic )  superior cervical ganglion ( 3rd
order neuron, postganglionic)  plexus around ICA
and ophthalmic arteries  ciliary ganglion without
interruption  ciliary nerves  dilator pupillae and
Muller’s muscle.
**Damage at any point in this pathway will result in
Horner’s syndrome

6. Neural pathway in Horner
syndrome:-
• First-order neurons
- Originate in hypothalamus
- Travel in spinal cord
- Synapse in ciliospinal center of Budge
• Second-order neurons (pre-ganglionic neurons)
- Originate at Budge center
- Exit spinal cord
- Travel in sympathetic chain
- Synapse in superior cervical ganglion – the stellate ganglion.
• Third-order neurons (post-ganglionic neurons)
- Originates in superior cervical ganglion
- Travels with internal carotid artery intocavernous sinus

9. CLINICAL FEATURES OF Horner syndrome:-

10. 1. Partial ptosis (drooping of the upper eyelid)  Muller muscle
and smooth muscle of levator palpebral superiors paralysis.
2. Miosis (constriction of the pupil)  pupil dilator paralysis.
3. Anhidrosis (decreased sweating)  occurs when the lesion is
proximal to fibre separation along the internal and external
carotid arteries.
4. Enophthalmus (sinking of the eyeball into the face)  The
enophthalmos of Horner syndrome is often apparent but not
real and is caused by the ptosis.
5. facial flushing  vasodilation of skin arterioles
6. loss of ciliospinal reflex.
7. The pupil's light reflex is maintained as this is controlled via the
parasympathetic nervous system.

12. Pathophysiology:-
• In Horner’s syndrome there is only partial ptosis since
control of the upper eyelid is controlled by two sets of
nerves: the IIIrd nerve supplies the levator palpebrae
superioris and sympathetic fibres supply the Muller
muscle.
• In Horner’s syndrome, despite the weakness owing to a
dysfunctional Muller muscle, the IIIrd nerve is still
intact meaning the ptosis is not complete. Interestingly,
voluntary upward gaze overcomes the partial ptosis.
• IIIrd nerve palsies and Myaesthenia gravis are two
important differentials of Horner’s syndrome to
exclude.

13. Pathophysiology:-
• Presentation of Horner’s is dependent on the site of the
lesion due to the anatomy of the sympathetic supply to the
face.
• Sympathetic supply to the face is composed of the
connection of three separate neurons:
• First order neurone: Hypothalamus → Brainstem → Cervical Cord à T1 root
ganglion.
• Second order neurone: T1 root ganglion → cervical sympathetic chain →
superior cervical ganglion.
• Third order neurone: Superior cervical ganglion → Muller muscles + pupil +
sweat glands

14. Pathophysiology:-
• Central lesions affect the First order neurones.
• Peripheral lesions are those which affect the Second (pre-
ganglionic) and Third (post ganglionic) order neurones.
• The ganglion is the superior cervical ganglion.
• Locating the lesion is dependent on identifying the pattern
of anhidrosis:

15. Causes of Horner syndrome:-

18. Classification of Horner syndrome:-

19. 1. First order neuron
2. Second order neuron
3. Third order neuron

20. FON:- Anatomy

21. FON:- causes

22. FON:- Associated features

23. FON:- Lesions

24. FON:- Imagings

25. Second order neurons:- Anatomy

26. Second order neurons:- Causes

27. Second order neurons:- Associated features

28. Second order neurons:- Lesions

29. Third order neurons:- Anatomy

30. Third order neurons:- Causes

31. Third order neurons:- Associated features

32. Third order neurons:- Lesions

33. Third order neurons:- Lesions

34. Third order neurons:- Lesions

35. first-neuron defect
(central Horner
syndrome)
second-neuron
involvement
(preganglionic Horner
syndrome)
third-neuron involvement
(postganglionic Horner
syndrome)
Clinical signs 1. contralateral
hyperesthesia
of the body
2. loss of sweating
of the entire
half of the
body.
1. loss of sweating
limited to the face
and neck
2. the presence of
flushing or blanching
of the face and neck.
1. facial pain or ear, nose,
or throat disease.
2. Usually not associated
with anhidrosis. 
because sympathetic
projections to the face
and neck emerge from
the sympathetic chain
prior to the superior
cervical ganglion.
Causes Arnold-Chiari
malformation
Pituitary tumour
Wallenberg (lateral
medullary) syndrome
Hypothalamic stroke
High cervical
myelopathy
Syringomyelia
Pancoast’s tumour
Subclavian artery dissection /
aneurysm
Thyroid masses / LAP
Cervical rib
Aortic aneurysm / dissection
Neck surgery
Central venous
catheterization
Shoulder dystocia (trauma to
Internal carotid artery
dissection
Cluster headache
Cavernous sinus thrombosis

37. Investigative approach:-

38. • Confirmatory test (apraclonidine test); can also use 1:1000
adrenaline eye drops
• Apraclonidine is a weak alpha-1 and strong alpha-2 agonist
• Due to hypersensitivity of the denervated pupil dilator and Muller
muscles
• Apraclonidine application hence results in reversal of miosis and lid
elevation
• Little or no response in normal eye
• False negatives: acute Horner’s when alpha-2 receptors have yet to be
up-regulated
• Cocaine test: cocaine inhibits noradrenaline re-uptake. In normal
eye, pupil will dilate. There will be no reaction in the affected eye
due to sympathetic denervation.
• First-order:
• MRI brain (structural lesions, stroke)
• MRI cervical spine (syrinx, cervical myelopathy)
• Second-order:
• Chest radiograph (apical lung tumour)
• Angiogram for large artery aneurysm / dissection
• Third-order:
• CT venogram (cavernous sinus thrombosis)

43. The END