MG, MND AND GBS Flashcards
What is the pathophysiology of myasthenia gravis?
antibodies to the acetylcholine receptors attack the receptor and lead to destruction of the post synaptic membrane
the reduced no of binding sites for ACh leads to inconsistent generation of muscle fibre action potentials which manifests as skeletal muscle weakness
what the S&S of MG?
muscular fatigue
ptosis and diplopia
peek sign - ask patients to close eyes and doctor tried to pry them open - should be easy
Dysphagia
dysathria
facial paresis
proximal limb weakness - reflexes and sensation are normal
what is MG associated with?
in <50s = commoner in women and associated with other autoimmune conditions and thymic hyperplasia
in >50’s = commoner in men and associated with thymic atrophy or tumour, RA and SLE
how is MG diagnosed?
Serum AChR antibody analysis
Muscle-specific tyrosine kinase (MUSK) antibodies
serial pulmonary function tests
- in MG crisis there is low FVC and NIF
Repetitive nerve stimulation - decreased response
CT thymus
- enlargement, atrophy or tumour
how is MG treated?
symptom control
- pyridostigmine (Anticholinesterase)
Immunosupression
- prednisolone
- may be combined with azathioprine
thymectomy
outline mysathenia crisis
life threatening weakness of respiratory muscles
monitor FVC - if below 20ml/kg then ventilate
Plasmapharesis and IVIG and identify trigger
what can trigger myasthenia crisis?
pregnancy infection gentamicin opiates B-blockers over treatment
what is MND?
cluster of degenerative disease characterised by loss of neurons in the motor cortex, cranial nerve nuclei and anterior horn cells
upper and lower motor neurons are affected but there is no sensory loss or sphincter disturbance which distinguises it from MS and polyneuropathies
what are the types of MND and how are they distinguised?
Amyotrophic lateral sclerosis
- typical MND with loss of motor neurons in mortor cortex, and anterior horn
Progressive bulbar palsy
- only affectds cranial nerves IX-XII
progressive muscular atrophy
- anterior horn cells only
- no UMN signs. affects distal muscles before proximal
Primary lateral sclerosis
- loss of Betz cells in motor cortex so mainly UMN signs + marked spastic leg weakness and pseudobulbar palsy
what are the general S&S of ALS? what are the UMN and LMN signs
stumbling spastic gait
foot drop and proximal myopathy
weak grip and shoulder abduction
aspiration pneumonia
UMN signs
- spascity
- Brisk reflexes
- Upgoing plantars
LMN signs
- wasting
- fasiculation
- bulbar signs ie swallowing and speech
can also see fronto-temporal dementia in 25%
how is MND diagnosed?
Mostly clinical
electromyography and repetiitive nerve stimulation can help
how is MND treated ?
Riluzole - prolongs life
Respiratory symptoms = NIPPV or ventilation
Mucous = carbocystiene
dysphagia = NG or PEG feeding
spascity = muscle relaxants (tizanidine) + PT
what infections can lead to Guillain Barre Syndrome?
CMV
EBV
Hep E
Camplyobacter jejuni
Mycoplasma species
what are the S&S of GBS?
progressive, ascending, symmetrical muscle weakness
- flacid paralysis with areflexia
- starts in legs and moves up
paraesthesia
areflexia
speech problems
rspiratory distress
facial weakness and droop
mild dysautonomia
- increased HR, increased BP and OH
what is the autoantibody involved in GBS?
antiganglioside antibodies such as GM1, asialoGM1, LM1 and GD1b.
