Conditions - Cranial Neuropathy and Brainstem Lesions

Question 1

What are the most common cranial neuropathies?

Answer 1

CNVI Abducent (most common)

CNIII Oculomotor
CNVII Facial
CNV Trigeminal

Question 2

What are the most common polyneuropathies of the cranial nerves?

Answer 2

Oculomotor & Trochlear
Trigeminal & Facial
Trigeminal & Abducent

Question 3

How are brainstem lesions classified?

Answer 3

Location
- midbrain / pons / medulla

Orientation
- medial / lateral

Origin

• intra-axial (originate in brainstem)
• extra-axial (original pathology external to brainstem)

Question 4

Describe the condition of CN VI Abducent Neuropathy

Answer 4

SSX:

• medial deviation of affected eye (from unopposed action of medial rectus)
• diplopia (double vision)

Etiology:
- ischaemia most common

Question 5

Describe the condition of CN VII Facial Neuropathy

Answer 5

SSX:

• ipsilateral SSX
• weakness / paralysis of muscles of facial expression
• eye unable to close (and subsequent eyelid irritation)
• decreased tear productiono
• drooling

Etiology:
- Bells Palsy common

Question 6

Describe the condition of CN III Oculomotor Neuropathy

Answer 6

SSX:

• L and R oculomotor nuclei are located close together, so often both are affected
• visual and extra-ocular SSX
• paralysis of extraocular muscles
• diplopia (double visiono)
• ptsosis (drooping)
• dilated pupil
• diminished pupillary response
• no lens accomodation

Etiology:

• vascular insults of posterior cerebral or superior cerebellar artery
• trauma or lesion

Question 7

Describe the condition of CN V Trigeminal Neuropathy

Answer 7

Anatomy:

• 4 nuclei (3 sensory & 1 motor)
• 3 divisions (V1, V2, V3)
• SSX vary depneding on nuclei / divisions affected

SSX:

• sensory SSX in face
• weakness / paralysis of mm mastication
• trigeminal neuralgia = severe and brief attacks of facial pain
• loss of corneal reflex

Question 8

Describe the condition of trigeminal neuralgia

Answer 8

• can affect 1 or more branches of trigeminal nerve
• caused by compression of nerve, leads to demyelination and spontaneous nerve firings

SSX:

• brief attacks of severe facial pain
• trigger zone where palpation will trigger an attack
• usually asymptomatic between attacks

Question 9

Describe the etiology and SSX of brainstem lesions

Answer 9

• usually caused by vascular insult (infarctions / haemorrhages), demyelinating disease or neoplasia

SSX:

• multiple cranial nerve involvement
• long tract signs (motor or sensory)
• crossed or alternating symptoms
• complex eye movement abnormalities
• vertigo / unsteadiness
• ataxia
• dysdiadochokinesia (unable to perform rapid alternating movements)
• nausea / vomiting

Question 10

Which arteries supply different parts of the brainstem?

Answer 10

Midbrain

• basilar
• posterior cerebral

Pons

• basilar
• superior cerebellar
• anterior inferior cerebellar

Medulla

• vertebral
• posterior inferior cerebellar
• anterior and posterior spinal

Question 11

Which parts of the brainstem are supplied by the basilar artery?

Answer 11

Midbrain and pons

Question 12

Which parts of the brainstem are supplied by the posterior cerebral arteries?

Answer 12

Midbrain

Question 13

Which parts of the brainstem are supplied by the superior cerebellar arteries?

Answer 13

Pons

Question 14

Which parts of the brainstem are supplied by the vertebral arteries?

Answer 14

Medulla

Question 15

Which parts of the brainstem are supplied by the anterior inferior cerebellar artery, and which by the posterior inferior cerebellar artery?

Answer 15

Anterior inferior cerebellar artery supplies pons

Posterior inferior cerbellar artery supplies medulla

Question 16

Describe medial medullary syndrome

Answer 16

• occlusion of anterior spinal or vertebral arteries

damage caused to:

• medial lemniscus
• pyramids
• hypoglossal nucleus / nerve

SSX:

• ipsilalteral paralysis / atrophy of tongue caused by damage to hypoglossal nerve
• contralateral hemiparesis (weakness) caused by damage to pyramids
• contralateral loss of light touch, vibration, propioception caused by damage to medial lemniscus

Question 17

Describe lateral medullary syndrome

Answer 17

• caused by occlusion of PICA or vertebral artery

damages:

• spinal trigeminal nucleus
• nucleus ambiguus
• spinothalamic tract

SSX:

• ipsilateral loss of pain and temperature sensory over face (damage to spinal trigeminal nucleus)
• ipsilateral paralysis of pharyngeal & laryngeal muscles
• contralteral loss of pain & temperature sensation over body (damage to spinothalamic tract)
• dysphagia (hoarseness)
• ipsilateral Horner’s Syndrome (damage to descending sympathetic fibres

Question 18

What is Horner’s syndrome?

Answer 18

• caused by interruption to sympathetic supply

SSX:

• ptosis (drooping)
• mimosis (pupil constriction)
• enopthalmos (backward displacement of eyeball in orbit)
• facial anhidrosis (impaired ability to sweat on affected side of face)

Question 19

Occlusion of the PICA and/or vertebral arteries is associated with which condition?

Answer 19

Lateral medullary syndrome

Question 20

Occlusion of the anterior spinal and/or vertebral arteries is associated with which condition?

Answer 20

Medial medullary syndrome