Muscle and Nerve Diseases Flashcards
Image showing the motor pathway
Muscle converts chemical energy to what?
designed to convert chemical energy → mechanical energy
What are the components of the process needed to convert chemical energy to mechanical energy?
- Structural components
- Contractile mechanism
- Excitation-contraction coupling (ion channels)
- Energy system
What are the symptoms of msucle disease?
• Weakness of skeletal muscle
Short of breath (respiratory muscles)
Poor swallow/aspiration (bulbar muscles)
- Cardiomyopathy
- Cramp, pain, stiffness, myoglobinuria - start to destroy muscle and myoglobin is peed out and will turn urine dark brown/bloody
(Babies: poor suck / feeding / failure to thrive / floppy)
What are the signs of muscle disease?
- Wasting/hypertrophy
- Normal or reduced tone and reflexes
- Motor weakness…NOT sensory
What investigations can be carried out for muscle disease?
- History and examination
- Creatine Kinase (CK)
- EMG - evaluating and recording the electrical activity produced by skeletal muscles
- Muscle biopsy
Structure
Biochemistry
Inflammation
• Genetic testing
What are the 2 categories that muscle disease can be put into?
congenital/genetic
acquired
What are some types of genetic/congenital muscle diseases and examples?
Structural: muscular dystrophies
Contractile: congenital myopathies
Coupling: channelopathies
Energy: enzymes/mitochondria
What are some examples of aquired muscle diseases?
Metabolic (Ca2+, K+)
Endocrine (thyroid, adrenal, vit D)
Inflammatory muscle disease
Iatrogenic: medication (steroids / statins)
When do muscular dystrophies start?
young or old onset
What is the severity of muscular dystrophies?
Progressive, variable severity
What happens in muscular dystrophies?
Cell degeneration (often high CK)
muscle diseases that results in increasing weakening and breakdown of skeletal muscles over time
What are some examples of muscular dystrophies?
Duchenne’s/Becker’s (dystrophin) - most common
Facioscapulohumeral/oculopharyngeal/limb girdle
Myotonic dystrophy (cataracts)
What is the treatment of muscular dystrophies?
No specific treatments yet
What cannels do Channelopathies effect and what are the symptoms? and treatment?
disorders of Ca2+, Na+, K+ and Cl- channels
often paroxysmal symptoms e.g. periodic paralysis / myotonia - toruble relaxing muscle
partially treatable - drugs can alter channels
How are energy production (metabolic myopathy) induced and what is the reason?
Exercise induced: early = disorders of carbohydrate metabolism
late = disorders of lipid metabolism
Mitochondrial problems
Are problems with energy production treatable?
partially treatable - alter diet
WHat are the 2 types of inflammatory muscle disease and their difference?
Polymyositis vs dermatomyositis (DM)
DM also comes with a rash
WHat are the features of inflammatory muscle disease?
Any age
Acute or subacute, painful, weak muscles
Characteristic rash of DM
How can inflammatory muscle diseases be diagnosed and investigated?
- High CK, autoantibodies, tumour screen (esp DM)
- EMG & biopsy
- Polymyositis: CD8 cells
- Dermato: humeral-mediated, B cells and CD4 cells
What is the treatment of inflammatory muscle diseases?
immunosuppresion
What else may be present alongside DM apart from a rash
Often all have a underlying tumour in DM – 50%
If you treat DM then miss tumour then problem
Where do disorders of neuromuscular junction effect?
How is ACh taken up from the synaptic cleft?
When you release ACH into synaptic cleft there is a recycling system and cholinesterase is what dose this
What is Myasthenia Gravis?
affects neuromuscular junction
a rare long-term condition that causes muscle weakness
What is the clinical presentation of Myasthenia Gravis?
Clinical presentation = Fatiguable weakness:
- Ocular: eyelids (ptosis)
muscles of eye movement (diplopia) - Generalised: limbs
bulbar (chew, swallow, talk)
breathing
What investigations are carried out for Myasthenia Gravis?
AChR, Anti MuSK antibodies - looking ofr the antibody that is causing it
Neurophysiology (Repetitive stimulation, Jitter)
CT chest (10% have an underlying thymoma)
What is the treatment of myathenia gravis?
- Symptomatic - Acetylcholinesterase inhibitor (pyridostigmine) - inhibits acetylcholinesterase from breaking down acetylcholine into choline and acetate, thereby increasing both the level and duration of action of the neurotransmitter acetylcholine
- Immunosuppression
Prednisolone - block cholinesterase so much more ACH but not removing antibody so use an immunosuppressant to try and reduce it
Steroid saving agent (e.g. azathioprine)
- Immunoglobulin/plasma exchange
- Thymectomy
Where does peripheral nerve disease affect?
What do peripheral nerves consist of?
•Sensory axons:
- Small fibres (pain + temperature)
- Large fibres (joint position sense + vibration)
- Motor axons
- Autonomic axons
- Nerve sheath (myelin)
Whata re the 3 different types of nerve disease?
- Root disease
- Lesion of individual peripheral nerve
Compressive/entrapment neuropathy
Vasculitic (mononeuritis multiplex)
• Generalised peripheral neuropathy
Motor/sensory/both
+/- autonomic features
Generalised peripheral neuropathy can either be __________ or _________
Axonal vs demyelinating
WHat are the causes of generalised peripheral neuropathy?
Hereditary
Metabolic: diabetes, alcohol, renal failure, B12
Toxic: drugs
Infectious: Lyme, HIV, leprosy
Malignancy: paraneoplastic
Inflammatory demyelinating:
Acute = Guillain Barre syndrome
Chronic = chronic inflammatory demyelinating polyneuropathy
What are the symptoms and signs of nerve root nerve disease?
Myotomal wasting and weakness
Reflex change
Dermatomal sensory change
symptoms and signs tend to be quite localised to the are of the nerve root
What are the symptoms and signs of individual nerve disease?
Wasting and weakness of innervated muscle
Specific sensory change
What are the symptoms and signs of generalised peripheral neuropathy
Sensory and motor symptoms, usually starting distally and moving proximally
What are the investigations for nerve disease?
Investigations depend on the cause:
- Blood tests
- Genetic analysis
- Nerve Conduction Studies
- Lumbar puncture (CSF analysis)
- Nerve biopsy (nb sensory nerve)
What is the treatment of nerve disease?
Treat the cause eg stop drug, surgery, immunoglob
Where do disorders of the anterior horn cell effect?
As the anterior horn cell is affected, what else is therefore effected?
LMN
What is motor neuron disease?
an uncommon condition that affects the brain and nerves. It causes weakness that gets worse over time. It’s nearly always fatal and can significantly shorten life expectancy, but some people live with it for many years
Where does motor neuron disease spread to and from?
Usually limb → bulbar (swallowing, speech etc)→ respiratory
What are the signs of motor neuron disease?
combination of UMN and LMN signs:
LMN = muscle fasciculations, wasting, weakness
UMN = increased tone, brisk reflexes
No sensory involvement
10%+ have cognitive decline
What is the prognosis of motor neuron disease?
Median 3-5 years from symptom onset, 2-3 years from diagnosis
50% die within 14 months of diagnosis
What is the diagnosis of motor neuron disease?
Basically a clinical diagnosis
Unique combination of UMN + LMN signs with no sensory signs
EMG - an electrodiagnostic medicine technique for evaluating and recording the electrical activity produced by skeletal muscles
What is the treatment of motor neuron disease?
Supportive - important:
PEG feed, non invasive ventilation, physio, OT, SALT, care
Riluzole - not great
Anticipatory / palliative care
