MG, MND AND GBS Flashcards

1
Q

What is the pathophysiology of myasthenia gravis?

A

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

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2
Q

what the S&S of MG?

A

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

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3
Q

what is MG associated with?

A

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

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4
Q

how is MG diagnosed?

A

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

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5
Q

how is MG treated?

A

symptom control
- pyridostigmine (Anticholinesterase)

Immunosupression

  • prednisolone
  • may be combined with azathioprine

thymectomy

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6
Q

outline mysathenia crisis

A

life threatening weakness of respiratory muscles

monitor FVC - if below 20ml/kg then ventilate

Plasmapharesis and IVIG and identify trigger

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7
Q

what can trigger myasthenia crisis?

A
pregnancy 
infection 
gentamicin 
opiates 
B-blockers 
over treatment
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8
Q

what is MND?

A

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

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9
Q

what are the types of MND and how are they distinguised?

A

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

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10
Q

what are the general S&S of ALS? what are the UMN and LMN signs

A

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%

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11
Q

how is MND diagnosed?

A

Mostly clinical

electromyography and repetiitive nerve stimulation can help

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12
Q

how is MND treated ?

A

Riluzole - prolongs life

Respiratory symptoms = NIPPV or ventilation

Mucous = carbocystiene

dysphagia = NG or PEG feeding

spascity = muscle relaxants (tizanidine) + PT

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13
Q

what infections can lead to Guillain Barre Syndrome?

A

CMV
EBV
Hep E

Camplyobacter jejuni
Mycoplasma species

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14
Q

what are the S&S of GBS?

A

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

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15
Q

what is the autoantibody involved in GBS?

A

antiganglioside antibodies such as GM1, asialoGM1, LM1 and GD1b.

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16
Q

how can GBS be diagnosed?

A

nerve conduction studies - slowed

LP - increased CSF protein (albumin)

LFTs - mild transaminits

spirometry - may show decreased VC, MIP or MEP

antiganglioside antibody

17
Q

how is GBS treated?

A

plasmapharesis
IVIG
ventilation