Neurology cases

Question 1

14 yr Female. 
Lead in: Please examine her eyes:
Alert
No cushinghoid face
Slightly lethagic
No Pallor/ Jaundice, No breathlessness
Eye alignments ok. No obvious squint
Some ptosis bilaterally at rest ( occasionally). 

Light reflex normal. Accomodation normal
Visual acuity Normal
Visual fields Normal
C/o diplopia on upward and lateral gazes bilaterally (beware if tested on extremes of visual fields)
No Nystagmus
Sustained Upward gaze 60s - noted to have slight downward movement of Rt eye. (Fatigability)
Rest of cranial nerves - grossly normal.
No problems counting from 1 - 30
No sternotomy scar
Examination of upper limb - including asking pt to adopt shoulders in abducted position for > 120s. All grossly Normal.

Answer 1

Dx - Ocular MG

Ddx- Systemic MG, 3rd nerve palsy; Myopathic face in Congenital Myopathy; Myotonic Dystonica (test Mother by shaking her hands - fail to relax grip); Glycogen storage diseases.

Pt’s Hx
C/o tremor on exertion (head and upper body) but not after a period of time.
Reduced exercise tolerance in PE class
Muscle tiredness and weakness.
Slurred speech and breathing difficulty (esp if tired)
No dysphagia/ choking

Question 2

Juvenile MG clinical features

Answer 2

The most frequent - ptosis, often associated with unilateral or asymmetric ophthalmoplegia, strabismus, and lid twitch, which may only be elicited after sustained upgaze. if severe may cause persistent amblyopia.
Most children also develop generalised muscle weakness, which presents as painless fatigability of the bulbar and limb musculature, with resultant dysphonia, dysphagia, and proximal limb weakness.
Weakness is often fluctuating and usually becomes more pronounced through the day and improves with rest. Children are at risk of choking or aspiration and are at increased risk of chest infection. Occasionally, impairment of the respiratory muscles necessitates ventilatory support- “myasthenic crisis”.

Prepubertal JMG is more likely to manifest as ocular myasthenia. There is an equal male: female ratio, in contrast to the female predominance that is seen in peri-/postpubertal children, and a better prognosis, with a higher rate of spontaneous remission in prepubertal presenters

Question 3

Juvenile MG DDx

Answer 3

1. Congenital myasthenic syndromes (Usually presents in infancy but can present later)
2. Mitochondrial cytopathies (Children frequently have additional neurological impairments or epilepsy)
3. Myopathies (Including congenital myopathies and muscular dystrophies)
4. Neurotoxins eg. botulism, venoms
5. Guillain-Barré syndrome
6. Acute disseminated encephalomyelitis
7. Multiple sclerosis
8. Brainstem tumour
9. Hypothyroidism

Question 4

How to diagnose MG

Answer 4

1. Serology -Detection of antibodies to the AChR supports the diagnosis of JMG.
2. Pharmacological Investigation - The Tensilon test involves intravenous infusion of edrophonium, a fast-acting, short-duration cholinesterase inhibitor. Look for transient improvement in , e.g, ptosis, dysphonia. Risky as it should only be performed by staff experienced in paediatric resuscitation, due to the cholinergic effects of edrophonium, which can result in bradycardia, nausea, and excess salivation.
3. EMG - decremental in motor action potentials in repeated nerve stimulation
4. CT thorax to look for Thymoma

Question 5

Rx for MG

Answer 5

1. Acetylcholinesterase inhibitors (Neostagmine)
2. Thymectomy (Not recommended in pre-pubertal child)
3. Steriods +/- AZA, Cyclosporin
4. Rituximab
5. IVIG / Plasma exchange