Disorders of the motor unit

Question 1

Diseases that affect the alpha lower motor neuron

Answer 1

1. Spinal muscular atrophy

2. Amyotrophic lateral sclerosis (also affects UMN)

Question 2

Diseases that affect peripheral nerves

Answer 2

1. Neuropathy: Charcot-Marie Tooth

2. infectious, inflammatory: Guillain-Barré syndrome

Question 3

Diseases that affect the Neuromuscular Junction

Answer 3

Myasthenia gravis

Question 4

Diseases that affect the muscle

Answer 4

Duchenne’s Muscular Dystrophy

Question 5

Neurological Approach to injury-2 steps

Answer 5

Step1:  
Identify the location of the injury
–  Central 
–  Peripheral 
–  Mixed

Step 2:
Determine the source of the injury
-Acquired
-Congenital

Question 6

Do central lesions (UMN) tend to yield positive or negative signs

Answer 6

Central lesions tend to yield positive signs

Question 7

DO Peripheral lesions (LMN) ten to yield positive or negative signs

Answer 7

peripheral lesions (LMN) ten to yield negative signs

Question 8

Motor unit compents

Answer 8

• Alpha lower motor neuron
– Cell body located in ventral horn of spinal cord (LMN)
– Axon forming peripheral nerve

• Neuromuscular junction
• Muscle

Question 9

How do central Lesions influence

• tone
• reflexes
• atrophy
• fasciculations
• sensory patterns
• other

Answer 9

• tone: increase, hypertonia
• reflexes: increase, hyperreflexia
• atrophy: none or mild
• fasciculations: absent
• sensory patterns: central pattern
• other: seizures, cognitive abnormalities

Question 10

How do Peripheral Lesions influence

• tone
• reflexes
• atrophy
• fasciculations
• sensory patterns
• other

Answer 10

• tone: decrease, hypotonia
• reflexes: decrease, hyporeflexia
• atrophy: significant
• fasciculations: Present
• sensory patterns: peripheral pattern

Question 11

Guillain-Barre

• description/cause
• onset
• symtoms
• treatment
• recovery

Answer 11

• an acquired neuropathy caused by an immune-mediated demyelination of peripheral nerve axons
• rapid onset of symptoms usually following an infection, symptoms peak at 2-3
weeks
• ascending weakness beginning in the distal limbs and progressing proximally
• areflexia
• Rx: Immunosuppression with intravenous immunoglobulins (not steroids)
• prolonged recovery

Question 12

Charcot Marie Tooth

Answer 12

• a congenital sensory and motor neuropathy (affecting lower motor neurons)
• progressive sensory loss occurs distally
• progressive weakness occurs distally
• “Charcot” foot – high arch and claw toes
• Rx: no cure; maintain movement, strength and flexibility with therapy

Question 13

Spinal Muscular Atrophy

Answer 13

• a congenital, progressive loss of lower motor neurons; SMN1 gene
• 2nd most common autosomal recessive disease
• progressive motor weakness and eventual muscle atrophy
• fasciculations
• Rx: Nusinersen (anti-sense oligonucleotide)

Question 14

Myasthenia Gravis

Answer 14

• an autoimmune disease of the neuromuscular junction
• fatigable weakness
• ptosis
• proximal muscles more susceptible than distal
• Rx: immunosuppression, pyridostigmine (blocks acetylcholinesterase)

Question 15

Muscular Dystrophy

Answer 15

• X-linked family of diseases that lead to progressive weakness and muscle
degeneration
• Gowers Sign – proximal muscle weakness leads patients to “walk” up their own
body when rising from a squat or prone position. (weak hips)
• Rx: no cure; steroids

Question 16

Amyotrophic Lateral Sclerosis (ALS) (Lou Gehrig’s disease)

Answer 16

• an acquired upper and lower motor neuron disease
• slowly progressive motor weakness
• progressively increased muscle tone
• Rx: none