Neuropathy, Myopathy, and Motor Neuron disease

Question 1

Mononeuropathy

Answer 1

involvment of a single major, named nerve usually by trauma or compression(wrist or elbow or peroneal nerve at fibular head)
-sensory and motor deficits reflect the anatomic nerve distribution

Question 2

Polyneuropathy

Answer 2

multiple nerves

• symptoms and signs are symmetrical and sensory loss or impairment occurs early and often remains prominent
• longest affected first-metabolic maintenance and axoplasmic flow are more susceptible to neurotoxic factors

symptoms:
* stocking and glove pattern
* paresthesia-pins and needles
* dysesthesia-unpleasant sensation from non-noxious stimulus
- weakness and muscle atrophy starts in distal limbs
- early loss or decrease of reflexes
- other symptoms if autonomic nerves involved

Question 3

What causes neuropathy?

Answer 3

1. demyelinating–>mononeuropathy (focal compression-carpal tunnel)
2. axonal degeneration–>polyneuropathy(guillain barre)

Question 4

Do most polyneuropathies from toxic metabolic causes have axonal degeneration or demyelination as the primary pathology?

Answer 4

axonal degeneration

-demyelination is secondary process

Question 5

With a severe crush or penetrating focal injury axonal degeneration occurs via wallerian degeneration, what does this mean?

Answer 5

axons and myelin degenerate distal to the point of nerve injury
-recovery takes longer and may be incomplete depending on perineurium to guide

without support scaffolding of perineurium resprouting axons pile up in a bulbous neuroma which is often painful

Question 6

What things can cause polyneuropathies?

Answer 6

1. medications(chemo)
2. neurotoxins (organic solvents, or alcoholism)
3. malnutrition and vitamin deficiencies
4. hereditary neuropathy (high arched feet, hammertoes, scoliosis)

Question 7

What test is good for detecting polyneuropathies ?

Answer 7

EMG
-electrical activity and function of nerves and muscles

Sural biopsy
or biopsy of adjacent muscle

Question 8

How do you treat polyneuropathy?

Answer 8

topical: capsaicin, substance P depleter, lidocaine
Oral: anticonvulsants and antidepressants

Question 9

Guillain Barre syndrome

Answer 9

-often following viral illness
-immune system targets peripheral nerve myelin
Symptoms:
ascending, areflexic paralysis
-spreads up even to extraocular muscles

EMG test: asymmetrical demyelination of proximal and distal segments of various nerves
Treatment:
plasmapheresis or IVIG

Question 10

What things cause chronic polyneuropathies?

Answer 10

1. diabetes mellitus
2. metabolic or endocrine disorders (uremia, hypothyroidism)
3. rheumatic disease (rheumatoid arthritis, systemic lupus)
4. cancer or myeloma
5. infection
6. nutritional deficiencies
7. toxins

Question 11

WHat is myopathy

Answer 11

primary pathology affects the muscle

-proximal weakness or fatigue with normal sensation and late loss of reflexes only after significant atrophy has occured

Question 12

WHat causes myopathies? What are tests you can do?

Answer 12

1. influenza
2. medications
3. endocrine disorders-cushing’s
4. hereditary
5. Creatine kinase level-elevated in muscle disease
6. EMG testing-rule out weakness from neuropathy, myasthenia, or motor neuron disease
7. muscle biopsy

Question 13

Polymyositis

Answer 13

• autoimmune disorder affecting muscles in adulthood
• proximal weakness evolves over weeks to months
• dermatomyositis-skin and muscle-rash periorbital and knuckles

Question 14

Duchenne’s X linked muscular dystrophy

Answer 14

• deficiency of muscle dystrophin
• Gower’s maneuver-use upper limbs to compensate for weak trunk and pelvic muscles
• pseudohypertrophy calves
• death from weakening of resp muscles or cardiomyopathy

Question 15

myotonic dystrophy type 1

Answer 15

excessive trinucleotide DNA repeats on chromosome 19-abnormal protein kinase in muscle fibers

• weakness in distal limbs, neck, face and jaw
• myotonia–impaired relaxation of muscle after volitional contraction

-also causes cataracts, frontal baldness, infertility and cardiac arrhythmias

Question 16

Mitochondrial myopathies

Answer 16

hereditary with abnormalities of various mito enzymes often affecting the brain in addition to muscle

Question 17

spinal muscular atrophy

give an example in a baby

Answer 17

group of disorders involving just anterior horn cells

• lower motor signs
  1. Werdnig Hoffman disease-infantile onset spinal muscular atrophy with fatal outcome due to respiratory weakness

Question 18

Primary lateral sclerosis

Answer 18

familial degeneration of the corticospinal tract in lateral columns of the spinal cord-not due to structural or metabolic

-weakness and upper motor neuron signs

Question 19

Pseudobulbar palsy

Answer 19

only the corticobulbar tract -cuasing facial weakness, impaired chewing, dysarthria, dysphagia and hoarseness

• bilateral may be caused by multiple cerebral infarctions, brain tumors lesions from MS, or brain trauma
• rarely is it degenerative disorder

Question 20

ALS

Answer 20

degeneration of corticospinal and corticobulbar tracts, gliosis and loss of anterior horn cells and pyramidal neurons and neurogenic atrophy of muscle
40-70
men more than women
Begins with:
focal weakness and atrophy in limb-such as shoulder or leg (foot drop)
–>spreads and becomes bilateral
or
with dysarthria, hoarseness or impaired swallowing (bulbar ALS)

• fasciculations
• spasticity and hyperreflexia
• extraocular muscle and sphincters of bladder and bowel are spared

familial-defective superoxide dismutase enzyme

• die from resp failure or complication such as infection
• can do an EMG

Treatment: riluzole-excitotoxic effect of glutamate at the NMDA receptors of motor neurons is opposed by riluzole