Vestibular Pathways

Question 1

Define peripheral vestibular system

Answer 1

Consists of semi-circular canals and CN VIII. Associated with CN VII and sympathetic innervation to the head.

Question 2

Define central vestibular system

Answer 2

Consists of 4 paired vestibular nuclei, lateral and medial vestibulospinal tracts, axons in reticular formation and vomiting centre, tracts for conscious perception via hypothalamus and tracts in the medial longitudinal fasciculus which terminate in the motor nuclei of CN III, IV and VI

Question 3

What is the main function of the vestibular system?

Answer 3

To maintain posture

Question 4

What are the clinical features of peripheral vestibular disease?

Answer 4

• Ipsilateral head tilt (associated with loss of facilitation to ipsilateral extensors)
• Ipsilateral ataxia, falling and rolling
• Horizonatal/rotary nystagmus (slow phase towards lesion)
• Ipsilateral facial nerve paralysis
• Pain opening jaw, ear disease
• Horners syndrome
• Normal proprioception (brainstem not affected)

Question 5

What are the features of central vestibular disease?

Answer 5

• Ipsilateral/contralateral head tilt
• Ipsilateral ataxia
• Ipsilateral/contralateral falling/rolling
• Horizontal/rotary nystagmus ipsilateral/contralateral
• Positional/vertical nystagmus
• Circle towards lesion
• Proprioceptive and postural deficits (hypermetria, clumsy)
• CN IV lesions (rare unless have meningitis)

Question 6

How does a lesion in the vestibular apparatus cause nystagmus?

Answer 6

• A lesion on the L will cause a decrease in the firing of AP on that side
• Causes an unbalance between R and L vestibular outputs
• There is increased input from the R which causes the head to turn to the right and nystagmus

Question 7

What are the features of paradoxical vestibular disease?

Answer 7

• Contralateral head tilt
• Nystagmus with slow phase away from lesion
• Cerebellar lesions -> ipsilateral ataxia and proprioceptive deficits

Question 8

What causes Horner’s syndrome and what are the clinical signs?

Answer 8

• Caused by damage to the sympathetic input to the eye which passes through the tympanic bulla and petrous temporal bone
• Due to underlying disease e.g. otitis, cervical disk herniation

Clinical signs:

• Miosis
• Prolapse of 3rd eyelid
• Narrowing of palpebral fissure
• Enopthalmus (posterior displacement of eyeball in orbit)

Question 9

Describe physiological nystagmus

Answer 9

1. Eyes fixed on object
2. Head turned to L - L vestibular nerve is stimulated via MLF, L abducent nerve and ocular nerve also stimulated
3. Stretch of extraocular muscles causes eyes to return to neutral position and fix on new object

Question 10

What type of nystagmus is seen with vestibular disease?

Answer 10

Jerk nystagmus