Download Motor unit pathophysiology

Motor Unit Pathophysiology
Neuro Course 4th Year
Neuro Course
General Principles of Motor Activity
Voluntary movements
Reflex movements
Rhythmic motor patterns
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Cortical
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Brain stem and associated structures
Brain Stem Centers
Cerebellum
Basal Ganglia
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Spinal cord
Final Common Pathway - lower motor neuron
Origin of Motor Unit Disease
Motor unit diseases can be broadly classified into four major categories:
 Spinal dystrophies (motor neuron body)
 Peripheral neuropathies (nerve: body+axon)
 Diseases of the myoneural junction
 Myopathies
Motor Deficits- Correlation of Signs with Anatomical Level
MUSCLE DISEASE:
NEUROMUSCULAR JUNCTION:
PERIPHERAL NERVE:
Major Categories of Peripheral Nerve Disease
1) Traumatic
2) Toxic/Metabolic
a) Systemic disorders (diabetes mellitus, uremia, liver disease)
b) Nutritional (beriberi, pellagra, alcohol, vitamin E deficiency)
c) Toxic-industrial (lead), drugs
d) Endocrine (DM, hypothyroidism)
3) Inflammatory Neuropathies
a) Acute inflammtory demyelinating polyradiculoneuropathy (Guillain-Barré syndrome)
c) Infections: leprosy, diphtheria, lyme disease, rabies, HIV, infectious mononucleosis
4) Hereditary Neuropathies
a) Hereditary Motor and Sensory Neuropathies (HMSNs)
b) Hereditary Sensory and Autonomic Neuropathies
c) Friedreich's ataxia
d) Neurofibromatosis
Neuromuscular disorders
Myasthenia gravis
Eaton-Lambert myasthenic syndrome
Muscle disorders
Inherited muscle diseases
 Congenital myopathies
 Lack of structural proteins e.g. Merosin deficient
 Ultrastructural appearance
 Central Core
 Lack of structural proteins
 Dystrophinopathies (Becker, Duchenne)
 Sarcoglycanopathies
 Alteration in muscle enzymes
 Calpain 3
 Myotonic dystrophy
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Defects in muscle energy metabolism
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glyco(geno)lysis e.g. McArdles
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lipid oxidation
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mitochondrial defects
Acquired muscle diseases
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Drugs (steroids)
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Endocrine (DM, thyroid)
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Infectious (viral myositis, dermatomyositis)
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Intoxication (venom)
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Paraneoplastic
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Rhabdomyolysis
Muscle disorders
Myopathy
a) static congenital myopathies
b) progressive genetically-determined wasting diseases or dystrophies
c) inflammatory myopathies
d) metabolic disorders
Neuropathy
Signs:
a) atrophy/hypertrophy
b) increased connective tissue, central nuclei, variation in fiber size,
disturbances in architecture
c) necrosis and regeneration
Muscle disorders – clinical signs
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Muscle pain
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Muscle weakness (limb, bulbar, respiratory)
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Muscle stiffness (myotonia)
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Breathlessness (respiratory or cardiovascular)
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Palpitations (cardiomyopathy or arrhythymia)
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Skin rash and other systemic features
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Myoglobinuria
Muscular Dystrophies
1) Duchenne and Becker Muscular Dystrophy
2) Congenital Muscular Dystrophy
3) Myotonic Dystrophy(chloride transport abnormality)
Metabolic Myopathies
1) Disorders of Glycogen Metabolism
2) Mitochondrial Encephalomyopathies