Neurology

Question 1

Internuclear Ophthalmoplegia (INO)

(Pathophys, Association, Clinical S&S)

Answer 1

• Medial Longitudinal Fasciculus (MLF) lesion
• MLF functions to connect ipsilateral CN3 to contralateral CN6 so that eye can move synchronously left to right.
• Commonly seen in Multiple Sclerosis (MS) - always bilateral
• Impaired adduction of the eye on the same side as the lesion (CN3), with horizontal nystagmus of abducting eye on the contralateral side (CN6).
• When covering one eye, unilateral movements will be normal. But when together, the adducting eye will not move past the midline.
• the patient may complain of horizontal diplopia.
• Convergence normal

Question 2

Eye Palsies

(Terminologies, CN3, CN4, CN6 palsies, surgical vs medical CN3 palsy)

Answer 2

Terminology
- Hypo: Downwards
Hyper: Upwards
Exo: Abduct
Eso: Adduct

• CN 3 Palsy
  
  • Unopposed abduction of affected eye (Unopposed CN6 action)
  • Infarct - pupil spared. (Medical CN3 palsy)
  • Compression - pupil dilated despite light (Surgical CN3 palsy). Usually related to PCom artery aneurysm
• CN 4 Palsy
  
  • Vertical diplopia
  • ‘Clumsy’. Missing steps when walking down stairs, bumping head when trying to get out of car.
  • Tend to move head down and to contralateral side to compensate
• CN 6 Palsy
  
  • Horizontal diplopia
  • Cover test will help identify affected eye
    Eg. diplopia on right horizonal gaze, improved with covering the right eye, hence, right abducens affected
  • Raised ICP

Question 3

Draw the Circle of Willis

Answer 3

https://www.youtube.com/watch?v=1x4Bex1KtrQ&t=163s&ab_channel=DirtyMedicine

Question 4

Lambert Eaton vs Myasthenia Gravis

(Which has autonomic symptoms, Pathophysiology, Which antibodies involved?, Which is worse in AM vs PM?, Which has ptosis and diplopia?, Associations)

Answer 4

LEMS is same as MG but has autonomic symptoms

LEMS affects ACh in presynaptic neurone
MG affects neuromuscular junction in post-synaptic neurone (PNS, SANS and smooth muscles not affected)

LEMS is due to antibodies to pre-synaptic voltage gated calcium channels
MG is due to antibodies to ost synaptic acetylcholine receptors

LEMS improve with use (worse in AM)
MG worsens with use (worse in PM)

LEMS extraoculuar muscles spared
MG can get ptosis and diplopia

LEMS is associated with small cell lung cancer
MG is associated with thymomas

Question 5

Myasthenia Gravis

(Presentation, Diagnosis - blood, imaging and confirmation test, Treatment, Myasthenic Crisis)

Answer 5

Extraocular muscle weakness, ptosis, facial muscle weakness, dysphagia, slurred speech, fatiguability

Dx: ACh receptor antibodies, MuSK antibodies, LRP4 antibodies
CT/MRI scan to look for thymoma
Edrophonium test - Edrophonium blocks acetylcholinesterase. Will briefly relief weakness

Tx: Pyridostigmine/Neostigmine
Steroids and Azathioprime to block immunoglobulins
Thymectomy if thymoma present

Myasthenic Crisis
- Severe complication of MG. Usually precipitated by respiratory illness
- Treatment: BIPAP/Intubation for Resp Failure.
IV Immunoglobulin or plasma exchange to remove antibodies

Question 6

Spontaneous Intracranial Hypotension (SIH) vs Idiopathic Intracranial Hypertension (IIH)

(Differences between ICP, Papilloedema, Postural headache, Opening pressure)

Answer 6

Spontaneous Intracranial HYPOtension
- Reduced ICP
- Postural headache- better when lying down
- No papilloedema
- Non-localising 6th nerve palsy
- Reduced opening pressure during LP
- Can occur post lumbar puncture

Idiopathic Intracranial HYPERtension
- Raised ICP
- Postural headache - worse when lying down
- Papilloedema
- Non-localising 6th nerve palsy
- Raised opening pressure during LP