Muscle and Nerve Disease Flashcards
Function of muscle
Convert chemical energy into mechanical energy
4 components of muscle
- Structural component
- Contractile mechanism
- Excitation-contraction coupling (ion channels)
- Energy system
Symptoms of muscle disease
Weakness of skeletel muscle Short of breath Poor swallow - aspiration Cardiomyopathy Cramp, pain, stiffness, myoglobinuria
Symptoms of muscle disease in children
Failure to thrive
Floppy
Poor feeding
Signs of muscle disease
Wasting
Hypertrophy
Normal/reduced tone with change in reflexes
Motor weakness, sensory normal
Investigation of muscle disease
History and Exam Creatine Kinase EMG Muscle biopsy Genetic testing
Why is creatine kinase tested when investigating muscle disease?
Degenerating muscle releases CK
Which type of muscle is CK testing not specific to? What should be tested instead?
Cardiac
Troponin
What elements are investigated when taking a muscle biopsy?
Structure
Biochemistry
Inflammation
4 categories of congenital/geneticc muscle disease
Structural
Contractile
Energy
Coupling
Examples of structural congenital/genetic muscle disease
Muscular dystrophies
Example of contractile congenital/genetic muscle disease
Congenital myotrophies
Examples of coupling congenital/genetic muscle disease
Channelopathies
Examples of energy congenital/genetic muscle disease
Enzymes/ mitochondrial disease
4 Categories of Acquired muscle disease
Metabolic - Ca, K
Endocrine - thyroid, adrenal, vitamin D
Inflammatory muscle disease
Iatrogenic -medication; steroids, statins
What symptoms may present with statin use to suggest muscle disease?
Aches
Unknown if psychological or organic
Some evidence of inflammatory myositis
Typical age Muscular dystrophies present
Younger or older onset
Character of disease course of muscular dystrophies
Progressive
One sign of cell degeneration in muscular dystrophies
High CK
5 examples of muscular dystrophy
Duchenne's Beckers Facioscapulohumeral Myotonic dystrophy (cataracts) Limb Girdle
Treatment for muscular dystrophies
Purely supportive, not curative
Managing respiration, swallowing
Provide support to children
Features of myotonic dystrophy
Multisystemic
Infertility
Cognitive decline
4 examples of channelopathies
Familial hypokalaemic periodic paralysis
Paramyotonia congenita
Hyperkalemic periodic paralysis
Myotonic congenita
What channels are affected in Familial hypokalaemic periodic paralysis?
Ca, Na, K
Which channels are affected in Paramyotonia congenita and Hyperkalemic periodic paralysis?
K
Which channels are afected in myotonia congenita?
Cl
Two factors to distinguish in metabolic muscle disease
Exercise induced
or
Fixed weakness
3 categories of metabolic muscle disease
Disorders of carbohydrate metabolism
Disorders of lipid metabolism
Mitochondrial myopathies/cytopathies
Features of mitochondrial myopathies
Genetic defect within mitochondrial gene Mild or profound effects Gut Deafness Diabetes Seizures Skeletal abnormalities
2 types of inflammatory muscle disease
Polymyositis
Dermatomyositis
Which inflammatory muscle disease is antibody associated?
Polymyositis
Needs aggressive immunosuppression to avoid fied weakness
Which inflammatory muscle disease is paraneoplastic?
Dermatomyositis
Onset of inflammatory muscle disease
Acute or subacute
Any age
Painful weak muscles
Characteristic rash of DM
Investigations for inflammatory muscle disease
High CK
EMG, inflammation and myopathic
Biopsy
Which cells are found in polymyositis on biopsy?
CD8 cells
Which cells are found in dermatomyositis on biopsy?
Humeral mediated, B cells and CD4 cells
Treatment of inflammatory muscle disease
Immunosuppression
Disorder of the Neuromuscular Junction
Myasthenia Gravis
Presentation of myasthenia gravis
Fatiguable weakness
Limbs, eyelids, muscles of mastication
–> Talking, SOB, diplopia
Investigations for myasthenia gravis
Antibody serology - Anti MuSK, AChR ab
Neurophysiology
CT chest (thymoma)
What percentage of patients with myasthenia gravis have underlying thymoma?
10%
Look for nodule - thymic hyperplasia
Treatment for myasthenia gravis
Symptomatic - acetylcholinesterase inhibitor
Immunosuppression - prednisolone, steroid saving agent
Immunoglobulin.plasma exchange
Thymectomy
4 components of the peripheral nerve
Sensory axons
Motor aons
Autonomic axons
Nerve sheaths (myelin)
Small fibres of peripheral nerve communicate…
pain , temperature
Large fibres communicate…
joint position, vibration
3 origins of peripheral nerve disease
Root disease Lesion of individual peripheral nerve - Compression/entrapment neuropathy -Vasculitic (mononeuritis multiplex) Generalised peripheral neuropathy - Motor/Sensory/Both +/- autonomic features
2 types of generalised peripheral neuropathy
Axonal v Demyelinating
Causes of Generalised peripheral neuropathy
Hereditary Metabolic - diabetes, alcohol, renal B12 Toxic - drugs Infectious - Lyme disease, HIV, Leprosy Malignancy - paraneoplastic Inflammatory demyelinating - Acute : Guillain Barre Syndrome , Chronic : Chronic inflammatory demyelinating polyneuropathy
Signs and symptoms of Peripheral Nerve Disease - Root
Myotomal wasting and weakness
Reflex change
Dermatomal sensory change
Signs and symptoms of Peripheral Nerve Disease - Lesion of individual nerve
Wasting and weakness of innervated muscle
Specific sensory change
Signs and symptoms of Peripheral Nerve Disease - Gernealised peripheral neuropathy
Sensory and motor symptoms
Usually start distally and move proximally
Investigations for peripheral nerve disease
Blood tests - renal dysfunction, thyroid, liver Genetic analysis Nerve conduction studies Lumbar puncture (CSF analysis) Nerve biopsy
Motor Neuron disease - progression
Limb to bulbar to respiratory
Signs of MND
Upper and Lower Motor Neuron signs Muscle fasciculations, weakness, wasting Increased tone, brisk reflexes Sensory sparing 10% have cognitive decline
Prognosis of motor neuron disease
3-5 years from symptom onset, 2-3 from diagnosis
50% die within 14 months diagnosis
Treatment for MND
Supportive (PEG feed, non invasive ventilation, physio, OT, SALT, care)
Riluzole - will extend life 3 months - slows down progression, no strength gained
Anticipatory, pallative care
Genetic mutation in Duchenne Muscular Dystrophy
Dystrophin gene Xp21
X-linked recessive
Mothers to male children
Signs and symptoms of Duchenne Muscular Dystrophy
Frequent falls Fatigue Toe walking/difficulty walking - equinovarus foot Muscle weakness Muscle pseudohypertrophy Muscle fibrosis Positive Gower's test
What is Gower’s sign
Patient starts in squatting position
Assume tripod position
Uses hands and arms to walk up body due to weakness in gluteus and quadriceps
Which type of mutations in the dystrophin gene cause Duchenne and Becker’s?
Duchenne- nonsense, frameshift - more severe;presents before age 5
Becker’s - missense - milder - presents age 10-20
Investigations for Duchenne’s MD
DNA testing
Creatine phosphokinase test - increased
Muscle biopsies - confirm mutation
EMG Electromyography - muscle destruction analysis
Treatment for Duchenne’s
Prednisolone and creatinine replacement
OT
Physio
Patient and parent education
Life expectancy for Duchenne’s
25-30 years
Complications of Duchenne’s
Cardiomyopathy
Scoliosis
Respiratory complications, risk of infections
Osteoporosis
