Myasthenia Gravis + Neurofibromatosis Flashcards
Myasthenia gravis (MG) pathology
Autoimmune
Antibodies against nicotinic ACh receptors
Interferes with neuromuscular transmission
Presentation of MG
Increasing muscular fatigue
Reflexes normal
Ptosis
Muscle groups affected in MG in order
Extra-ocular
Bulbar (swallowing, chewing)
Face
Neck
Limb girdle
Trunk
Factors which worsen muscle weakness in MG
Pregnancy
Low K
Infection
Exercise
Gentamicin
Beta blockers
Associations of MG if age under 50 yrs
F
Other autoimmune
Thymic hyperplasia
Associations of MG if age > 50 yrs
M
Thymic atrophy / tumour
Rheumatoid
SLE
Ix for MG
Anti-AChR antibodies
MUSK antibodies
Neurophysiology
MUSK antibodies
Muscle specific tyrosine kinase
MG findings in neurophysiology
Decreasing muscle response to repetitive nerve stimulation
Mx of MG
Symptom control
Immunosuppression
Thymectomy
Sx control for MG
Pyridostigmine
(Anticholinesterase)
Immunosuppression for MG
Prednisolone
+/- azathioprine / methotrexate
Use of immunosuppression for MG
Relapses
When to consider thymectomy for MG
Onset < 50 yrs
Thymoma
Cholinergic SEs
Hypersalivation
Lacrimation
Sweats
Vomiting
Miosis
Prognosis of MG
Relapsing or slow progression
Myasthenic crisis
Respiratory muscle weakness in relapse
Life threatening
Mx of myasthenic crisis
Plasmapheresis or IV Ig
Rx trigger (eg. infection, drugs)
Plasmapheresis
Filter blood
Removes antibodies from plasma
Lambert-Eaton myasthenic syndrome pathology
Antibodies to voltage gated Ca channel on presynaptic membrane
Causes of Lambert-Eaton myasthenic syndrome
Paraneoplastic (from small cell lung cancer)
Autoimmune
Features of Lambert-Eaton myasthenic syndrome (differing from MG)
Gait difficulty before eye signs
Autonomic involvement
Hyporelexia and weakness improving after exercise
Mx of Lambert-Eaton myasthenic syndrome
3,4-diaminopyridine
IV Ig
Types of neurofibromatosis
Type 1 neurofibromatosis (NF1)
Type 2 neurofibromatosis (NF2)
Other name for NF1
von Recklinghausen’s disease
NF1 inheritance
Autosomal dominant
Signs of NF1
Cafe-au-lait spots
Freckling
Dermal neurofibromas
Nodular neurofibromas
Lisch nodules
Short stature
Macrocephaly
Cafe-au-lait spots
Flat
Coffee coloured patches of skin
Seen in 1st year of life
Increase in size and number
Freckling in NF1
In skin folds
Present by age 10
Dermal neurofibromas
Small
Violaceous nodules
Gelatinous texture
Appear at puberty and increase in number
Painless
Nodular neurofibromas
From nerve trunks
Firm
Well demarcated
Paraesthesia if pressed
Lisch nodules
Tiny and harmless
Brown / translucent mounds (hamartomas)
On iris
Develop by 6 yrs
Complications of NF1
Mild learning disability
Local effects of neurofibromas
HTN
Malignancy
Epilepsy
Carcinoid syndrome (rare)
Local effects of neurofibromas
Nerve root compression
GI bleeds / obstruction
Bone cystic lesions
Scoliosis
Malignancy risks with NF1
Optic glioma
Sarcomatous change in neurofibromas
Diagnosis of NF1
2 or more of:
- 6+ cafe-au-lait spots
- 2+ neurofibromas
- Freckling in axilla / inguinal region
- Optic glioma
- 2+ lisch nodules
- Typical osseous lesion
- First degree relative with NF1
Mx of NF1
MDT
Genetic counselling
Can excise particulary troublesome neurofibromas
(Not all though)
NF2 inheritance
Autosomal dominant
Mosaicism in 50%
Which is more common, NF1 or NF2?
NF1
Signs of NF2
Cafe-au-lait spots
Bilateral vestibular schwannomas
Juvenile posterior subscapular lenticular opacity
Juvenile posterior subscapular lenticular opacity
Form of cataracts
Rough age of vestibular schwannoma presentation
20 yrs
Complications of NF2
Tender schwannomas (cranial / peripheral nerves)
Meningiomas
Glial tumours
Diagnosis of NF2
1) Bilateral vestibular schwannomas
OR
2) First degree relative with NF2
+ a) unilateral vestibular schwannoma OR
b) one of:
- Neurofibroma
- Meningioma
- Glioma
- Schwannoma
- Jeuvenile cataract
Mx of NF2
Hearing tests yearly from puberty
Neurosurgery for vestibular schwannomas
Prognosis of NF2
Mean survival 15 yrs from diagnosis
Mosaicism NF2 definition
NF2 but vestibular schwannomas may be absent
Schwannomatosis definition
Multiple tender cutaneous schwannomas
No vestibular schwannomas
Normal life expectancy