Muscular & neuromuscular treatments Flashcards
Myopathy acquired causes
- autoimmune
- toxic: corticosteroids , statins , chloroquine , colchicines, alcohol
- Viral - HIV , HCV
- metabolic - Ca, K +?-
- Critical illness myopathy - immobilization
- endocrine - thryoid, parathyroid, addison’s , cushing’s
What is dermatomyositis and how does it present
Cause of inflammatory myopathy , autoimmune
- Gottron papules ( red patches on knuckles ) , periorbital odema , heliotrope rash , V sign , shawl sign , mechanic’s hands
- Acute or subacture proximal weakness, myalgia
- CK 10-50x the normal ( high )
- Anti-Mi2, Anti-MDA5, Anti0TIF-Ia , etc.
- associated with malignancies ( 10-20%) : lung , breast , ovarian , lymphoma
- muscle biopsy : perifasicular atrophy
Treatment for Dermatomyositis
- Steroids
- long term immunosuppressants parallel with steroid : methotrexate, azathioprine, mycophenolate mofetil
- If not effective : IVIG , ciclosporin
- 3rd line : rituximab , cyclophosphamide
Common NMJ disorders
1- Lambert eaton myasthenic syndrome
2- organophosphate poisoning
3- Botulinum toxin
4- congential myasthenic syndromes
What antibodies might be seen with myasthenia Gravis
Anti muscle specific kinase ( MuSK )
What is MG ( explain physiologically what happens )
AChR antibodies bind to and block receptor leading to degradation and endocytosis of AChRs and degeneration of motor end-plate and loss of postsynaptic folds.
Leads to reduced muscle membrane depolarization and increase in threshold required to initiate muscle action potential
MG presention
1- Fatiguability
2- diurnal variation
3- weakness of extra-ocular muscles: ptosis and ophthalmoplegia
4- weakness of neck extension/flexion : head drop
5- proximal limb weakness and finger extensor weakness
6- rare wasting
7- preserved reflexes
8- sensory normal
MG investigations
- AChR antibody , MuSK antibody
- Ice pack test : Ptosis will resolve after ice
- Tensilon test : endrophonium IV to assess objective improvement in muscle strength
- Neurophysiology
- Exclude thymoma ( CT chest )
MG neurophysiology
RNS
- decrement of > 10% over 5 responses = MG
- can be normal in ocular MG
- unreliable if limb is cold or patient on acetylcholinesterase inhibitors
Single fibre EMG ( SFEMG)
- increased variability in interval b/w paired action potentials of 2 muscle fibres in a single motor unit - jitter = evidence of defect in neuromuscular transmission
- jitter could be found in myopathy or denervation
MG management
1- Pyridostigmine ( plus propantheline ) : acetylcholinesterase inhibitor
- inhibits Ch breakdown by acetylcholinesterase in synaptic cleft
2- steroids
3- steroid-sparing agents : azathioprine , ciclosporin , methotrexate, mycophenolate mofetil
4- IVIg, PLEX
5- Rituximab
MG exacerbating factors
- Infection
- stress , trauma , post-op
- cholinesterase inhibitors withdrawal
- rapid introduction or increase of steroids
- electrolyte imbalance
- anaemia
drugs
Myasthenic crisis presentation and management
Neurological emergency
On onset :
- increase muscle weakness and diplopia
- respiratory failure
- O2 saturation and blood gases could be normal until late in crisis
- FVC : less than 1L = requires ICU support
Management :
- IVIg , plasma exchange , ventilation , NBM 7 NG feeding
Most common causes of polyneuropathies
- Diabetes, vitamin deficiency ( BT12 ) , endocrine , toxins, hereditary , infectious , inflammatory
What is Guillain Barre Syndrome
Acute inflammatory demyelinating polyradiculoneuropathy ( AIDP )
- acute infectious triggers
- proximal weakness but all other signs of neuropathy
Guillain Barre Syndrome presentation
Progressive weakness : hrs to days
- Areflexia
- peak of symptoms in less than 4 weeks from onset
- symmetrical
- predominantly affects motor more than sensory ( might first start with tingling and then weakness )
- autonomic dysfunction : BP, cardiac arrhythmia
- facial involvement and bulbar involvement
GBS investigations
CSF - elevated protein ( unless really early in disease )
- NCS: demyelination ( can be normal initially )
- imaging : no structural cause
- CK : check no muscle disease
- TFTs, K , Bone : no metabolic cause
GBS treatment
Do not respond to steroids but IVID and PLEX
- supportive care with airway support
- enoxaparin
Examples of Mononeuropathies ( most common )
1- Carpal tunnel
2- ulnar nevre palsy
3- radial nerve palsy : compression in spiral groove in humerus = wrist drop
4- foot drop ( common peroneal nerve palsy )
MND subtype
1- Amytrophic lateral sclerosis : most common , mix of UMN & LMN signs
2- progressive muscular atrophy : LMN signs only , could start with 1 limb
3- Progressive bulbar palsy : confined to bulbar dysfunction but may progress to ALS
4- Primary lateral sclerosis : UMN signs only
Clinical findings of MND
- painless progressive weakness and wasting
- eye movements normal
- Lower Cranial nerves : jaw weakness, jaw jerk brisk , facial weakness , Gag reduced/exaggerated, bulbar/pseudo bulbar palsy , tongue fasciculation
- head drop
- cachexia
- normal sensation
- cognition : frontal involvement
- Limbs UMN/LMN: ex: triceps weak and wasted fasciculating but brisk reflex
MND mimics
- Multifocal motor neuropathy
- cervical myeloradiculopathy
- MG : MND has no ocular symptoms
- inherited motor neuropathies : MND is more rapidly progressive
MND investigations
- MRI spine: exclude other causes
- Nerve conduction studies and EMG : excludes multifocal motor neuropathy
MND management
Terminal Diagnosis - no treatment but interventions to improve quality of life
- SALT - speech and language therapist
- Non invasive ventilation : respiratory muscle weakness
- palliative care symptom control
- Nurse specialist
- Gastroenterology/Dietician : increased metabolic demands cause rapid weight loss and lose swallow = alternative feeding route
( PEC/RIG)
- Riluzole : prolong life for a couple of months
What is a bad prognostic sign of MND
Early bulbar involvement
Median survival for MND
3.5 years , 10% live more than 10 years
Acute neuromuscular respiratory failure Presentation
- ABG normal until very late
- FVC <1L or dropping by 50% = be concerned
- Acute : patients don’t complain of SOB , single breath test shows SOB , patient anxiety , increased HR , use of accessory muscle
- Acute on Chronic : confusion and sedation rather than agitation
Top causes of Acute neuromuscular respiratory failure
Guillan Barre syndrome , MG , MND
