Brainstem localisation

Question 1

Limitations of rules of 4

Answer 1

No anterior-posterior rules

Question 2

CN3 palsy TRO long tract signs

Answer 2

Long tract sign - look for pronator drift - brainstem disorder (midbrain)
Medial midbrain syndrome - Weber syndrome

All CN 3 4 6 palsies must check pronator drift!

Question 3

CN6 palsy TRO long tract

Answer 3

Look for pronator drift - pontine lesion
Look for CN7 pay

Medial pontine syndrome - Millard Gubbler

Question 4

Anisocoria, bhlepharoptosis, uvula deviated

Answer 4

look at the eyelid of normal eye - will not cover the iris
Inverse ptosis / upside down ptosis /bhlepharoptosis - lower eyelid covers part of the eyelid
> Horner syndrome

Lateral medullary syndrome

Question 5

Right tongue wasting, pronator drift

Answer 5

Medial medullary syndrome - Derjerine syndrome

Question 6

Isolated LE adduction defect

Answer 6

Intranuclear ophthalmoplegia - INO
- Test MLF - saccade (hardest and most stressful), pursuit, conjugate gaze (convergent divergent)
- Ddx: demyelination disorder - MS, NMO (younger pt), ischaemic cause - stroke (older pt)
- MRI brain demyelination protocol with contrast vs stroke protocol

Check saccades - test adduction defect properly
Check vergence - prove defect above nerve/ muscle
Check concomitant cranial nerve deficits
Demonstrate long tract signs

Other causes of INO: Wernicke encephalopathy

Very rarely partial 3rd nerve palsy or medial rectus injury
- 3rd nerve travels in bundle - usually won’t only hit 1 muscle (medial rectus entrapment) and sparing everyon else

Question 7

Addressing INO myths

Answer 7

Covering one eye, diseased eye will recover ??
- Conjugate gaze occurs even with just 1 eye and still requires MLF

To test supranuclear localisation, do VOR ??
- Shaking the head will not recover, MLF still needed