Muscle and Nerve Diseases Flashcards
What are the symptoms of muscle disease?
- Poor suck / feeding / failure to thrive / floppy
- Weakness of skeletal muscle
- Short of breath (respiratory muscles)
- Poor swallow (aspiration)
- Cardiomyopathy
- Cramp, pain, myoglobinuria
Myoglobin is muscle breakdown – you excrete in your urine and it makes the urine black
What are the signs of muscle disease?
- Wasting/ hypertrophy
- Normal or reduced tone and reflexes
- Motor weakness…NOT sensory
Why might hypertrophy result from a muscle disease?
Muscle cannot relax
What is the investigation for a muscle disease?
- History and examination
- CK - Creatinine phosphokinase – sometimes elevated in the blood in muscle degenerative diseases
- EMG - EMG – electrical myography – electrode is placed within the muscle to test electrical funciton
- Muscle biopsy
–Structure
–Biochemistry
–Inflammation
•Genetic testing
What are the classifications of muscle disease?
- Muscular dystrophies - usually genetic - to do with structure of the muscle
- Channelopathies - usually episodic
- Metabolic muscle disease - an issue with the way the muscle uses energy, usually due to enzymes
- Inflammatory muscle disease
- Congenital myopathies
- Iatrogenic - medication - statins cause inflammation or degeneration of the muscles
Which part of the muscle contracts and shortens?
Myosin fibrils
Give examples of muscular dystrophies
- Duchenne’s MD - related to dystrophin protein
- Becker’s MD - also dystrophin gene, milder form of duchenne’s
- Facioscapulohumeral MD
- Myotonic dystrophy
- Limb-Girdle MD
Give examples of muscle channelopathies
- Familial hypokalemic periodic paralysis
- Hyperkalemic periodic paralysis
- Paramyotonia congenita (chlorine deficiency)
- Myotonia congenita (chlorine deficiency)
Myotonia – can’t relax their muscles – muscles have continually low level contraction – if you shake their hand they can’t release their grip
What are metabolic muscle disorders?
- Disorders of carbohydrate metabolism
- Disorders of lipid metabolism
- Mitochondrial myopathies/ cytopathies
- Endocrinopathy (thyroid, Cushing)
- Biochemical abnormalities
Glycogen – used for immediate rapid muscle activity, eventually run out – fatty acids are the next supply. Disorders of carbohydrate and lipid metabolism is often more prevalent after excersize
Give examples of inflammatory muscle diseases
Polymyositis
Dermatomyositis - Dermatomyositis – inflammation of the skin too (characteristic rash) – often as a result of malignancy – paraneoplastic phenomenon
What are the symptoms of inflammatory muscle disease?
Pain as a result of inflammation
Patient generally feels unwell
What is the investigation for inflammatory muscle disease?
- Increase in Creatinint Phosphokinase
- EMG, inflammation and myopathic
- Biopsy
–PM: CD8 cells
–DM: humeral-mediated, B cells and CD4 cells
What is treatment for polymyositis and dermatomyositis?
Immunosuppression
What is the presentation of disorders of the neuromuscular junction?
Fatiguable weakness:
–Limbs
–Eyelids (ptosis)
–Muscles of mastication (chewing), swallow
–Talking
–SOB - Affects all NMJ’s so can cause respiratory failure
–diplopia
Clear feature of NMJ problems is fatigue – muscles start strong and then get weaker. As day goes on – progressive problem with muscle weakness – diplopia because of muscle weakness in the eye.
Why does fatigue in the muscle happen?
Because acetylcholine becomes gradually reduced throughout the day in the synapse
What are the three ways acetlycholine receptor antibody prevents the NMJ working properly?
“Binding” antibodies attach to the acetylcholine receptors on nerve cells and may initiate an inflammatory reaction that destroys them.
“Blocking” antibodies may sit on the receptors, preventing acetylcholine from binding.
“Modulating” antibodies may cross-link the receptors, causing them to be taken up into the muscle cell and removed from the neuromuscular junction.
What antibodies are searched for in Myasthenia Gravis?
AChR ab
Anti MuSK ab
(muscle specific tyrosin kinase)
What are the ither ways we can investigate myasthenia gravis?
•Neurophysiology
–Repetitive stimulation
–Jitter
•CT chest (thymoma)
What is treatment for myasthenia gravis?
•Symptomatic
–Acetylcholinesterase inhibitor
•Immunosuppression
–Prednisolone
–Steroid saving agent (azathioprine)
- Immunoglobulin / plasma exchange - filters out antibody in the blood
- Thymectomy - antibody production can be as a result of an over active thymus - even in the case where there is no thymoma
What do peripheral nerves consist of?
Sensory axons:
- Small fibres (pain and temperature)
- Large fibres (joint position sense and vibration)
Motor axons (lower motor neurone)
ANS
What are common causes of damage of the nerve root?
Lesions in the spine, such as prolapse of the nucleus pulposus, spinal tuberculosis, cancer, inflammation, spinal tabes.
Spinal tabes is also known as syphilitic myelopathy - slow degeneration (specifically, demyelination) of the neural tracts primarily in the dorsal columns of the spinal cord & dorsal roots
What are causes of lesions to individual peripheral nerves?
Compression / entrapment - carpal tunnel is caused by entrapment of the median nerve
Vasculitic (mononeuritis multiplex) - If nerve doesn’t receive blood from the vasovasorum there is mononeuritis multiplex (SLE, rheumatoid arthritis)
Besides root disease and lesion of individual peripheral nerves, what other mechanism exists that causes nerve disease?
Generalised peripheral neuropathy
–Motor/ sensory/ both
–+/- autonomic features
most nerves carry motor and sensory – affects longest nerves first
What are the causes of generalised peripheral neuropathy?
–Metabolic: Diabetes, alcohol, renal, B12
Diabetes affects peripheral nerves - loss of sensation of the feet
–Toxic: drugs - Alcohol – neurotoxin – takes control of cerebellum – eventually kills nerve cells – cerebellar ataxia, dementia – neuropathy because it damages peripheral nerves
–Hereditary
–Infectious: Lyme, HIV, leprosy
–Malignancy: paraneoplastic - body fights cancer and the inflammatory response attacks another part of the body
–Inflammatory demyelinating
- •Acute = Guillain Barre syndrome
- •Chronic = chronic inflammatory demyelinating polyneuropathy
What are symptoms and signs of a nerve root disease?
–Myotomal wasting and weakness
–Reflex change
–Dermatomal sensory change
What are signs and symptoms for individual nerve disease?
Wasing and weakness of innervated muscle
Specific sensory change
What are signs and symptoms of generalised peripheral neuropathy?
–Sensory and motor symptoms starting distally and moving proximally
What are nerve disease investigations?
- Blood tests
- Genetic analysis
- Nerve Conduction Studies - stimulate nerve with electricity
- Lumbar puncture (CSF analysis)
- Nerve biopsy (nb sensory nerve) - never motor nerve
Anterior horn cell
What is the other name for motor neuron disease?
Amyotrophic lateral sclerosis
What is the progression of disease in motor neuron disease?
•Usually limb onset, later bulbar and respiratory involvement
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
What is the prognosis of motor neuron disease?
–3-5 years from symptom onset
–2-3 years from diagnosis
–50% die within 14 months of diagnosis
What is diagosis of motor neuron disease?
- Unique combination of UMN + LMN signs
- EMG - electromyography – loss of lower motor neurone causes loss of innervation to muscle – appears on EMG – used to rule out a neuropathy.
What is treatment for motor neuron disease?
- Supportive (PEG, NIV, physio, OT, care)
- Riluzole - debatable
