Neuro-Motor

Question 1

Duchenne Muscular Dystrophy (DMD)

Answer 1

Etiology: X linked recessive, generally in males
Pathophysiology: Dystrophin gene mutation  Deficiency in dystrophin protein production 
-Muscle cell membranes become more permeable 
-Free calcium enters the muscle cells  cell death 
-Muscle cells replaced with fat and connective tissue
-Muscle fibers may tear with contraction. Fig. 15-6, p. 388
Manifestations of DMD:
-Progressive muscle weakness
-Pseudohypertrophy
-Gower sign
-Waddling gait
-Loss of ambulation ability
-Contractures, joint immobility, and scoliosis
-Respiratory and cardiac problems

Question 2

Myasthenia Gravis

Answer 2

-neuromuscular junction disorder affecting the peripheral nerves
Etiology: progressive, autoimmune disorder; can occur at any age, see more in females
Pathophysiology: Fig. 15-7, p. 390 Neuromuscular junction
-Acetylcholine receptor sites not seen as “self”
-Complement mediated injury to receptor sites
-Autoantibodies (IgG antibody complexes) produced
-Acetylcholine receptor sites blocked by antibody attachment and eventually destroyed at the neuromuscular junction
-Blocks neurotransmission at the neuromuscular junction
Manifestations:
-Muscle fatigue and progressive weakness
-Eye muscles, progressive down face, and neck first
-Myasthenia crisis – muscle weakness compromising ventilation

Question 3

Mononeuropathies

Answer 3

Ex. Carpal tunnel syndrome
Etiology: most often due to repetitive use of the wrist
Pathophysiology:
-Carpal tunnel is too small or increased amount of tunnel contents 
-Compression of the median nerve  entrapment
Manifestations: pain, paresthesia, numbness (thumb and first 3 fingers), weak grip

Question 4

Polyneuropathies

Answer 4

demyelination or axonal degeneration 
Etiology: immune mechanisms, toxic agents, metabolic diseases
Guillain-Barre syndrome
Pathophysiology:
-Autoimmune inflammatory reaction against peripheral nerves
-Antibodies produced against myelin sheath  demyelination in an ascending pattern
-Re-myelination and axonal regeneration occur
Manifestations:
-Motor weakness, paresis/paralysis, paresthesias, pain
-Decreased or absent deep tendon reflexes
-Respiratory insufficiency
-No loss of cognitive function

Question 5

Back pain and spinal nerve root disorders

Answer 5

Low back pain

• Acute: usually muscle or ligament strain
• Chronic: degenerative disk disease (DDD) - genetic tendency, increased with age →
• Chronic Inflammatory, mechanical, or vascular cause  disk dehydrates or changes structure/function. Examples:
• Spondylolysis – may be hereditary, structural defect in the vertebrae
• Spondylolisthesis – vertebrae move forward
• Spinal stenosis–narrowing of the spinal canal

-Herniated disk - Fig. 15-9, p. 394 
Pathophysiology:
-Disk capsule may be torn 
-Nucleus pulposus herniates through annulus 
-Compresses the nerve or spinal cord
Manifestations: depends on area – Fig. 15-10, p. 394
-Pain 
-Weakness/Numbness  
-Reflexes

Question 6

Disorders of the Motor Unit (muscular dystrophy)

Answer 6

Duchenne Muscular Dystrophy (DMD) 
Myasthenia Gravis 
Mononeuropathies
Polyneuropathies
Back pain and spinal nerve root disorders

Question 7

Disorders of the Basal Ganglia

Answer 7

Parkinson disease

Etiology: onset > 50 years; genetic and environmental factors
Pathophysiology: Fig. 15-12, p. 398
-Degeneration of basal ganglia  loss of neurons that produce and store dopamine 
-Low dopamine levels with increased cholinergic activity 
-Abnormal proteins may accumulate in brain tissue over time (Lewy bodies)  dementia
Manifestations: difficult to assess initially  symptoms mild initially
-Hallmark: tremor at rest (in arms and hands)
-Rigidity, bradykinesia/akinesia
-Short, shuffled gait, weakness
-Loss of postural stability
-Excessive daytime sleepiness
-Mask like facial expression, infrequent blinking, drooling
-Monotonous, slow speech
-Advanced → intellectual deterioration, dementia, depression (Lewy bodies in the brain)

Question 8

Upper Motor Neuron Disorders

Answer 8

Amyotrophic lateral sclerosis (ALS; Lou Gehrig disease)
Multiple sclerosis (MS)
Vertebral and spinal cord injury

Question 9

Amyotrophic lateral sclerosis (ALS; Lou Gehrig disease)

Answer 9

Etiology: mostly men; middle to late adulthood
Pathophysiology:
-Primary feature: destruction of upper and lower motor neurons without inflammation 
-Muscle fibers atrophy  skeletal muscle degeneration  severe muscle weakness
Manifestations:
-Initial muscle weakness, cramps, atrophy usually starts in one muscle group  complete flaccid and spastic paralysis
-Impaired speech, difficulty chewing/swallowing, drooling
-No change in mentation or cognition
-Poor long-term prognosis

Question 10

Multiple sclerosis (MS)

Answer 10

acquired, autoimmune or genetic tendency – Fig. 15-13, p. 401 (loss of myelin)
Etiology:
Pathophysiology:
-Autoimmune process in a genetically susceptible person 
-Destruction of myelin in the brain and spinal cord  inflammation  axonal scarring
-Development of MS lesions/plaques in the white matter of the CNS 
-Decreased neurotransmission
-Progressive disease with relapsing events
Manifestations:
Initial symptoms: paresthesias, muscle weakness, fatigue, visual changes
-Psychological changes:
-Advanced MS: ataxia, slurred speech, bowel/bladder incontinence

Question 11

Vertebral and spinal cord injury

Answer 11

Etiology: 16-30 years old most common; MVC #1, falls, violence, sports

Primary injury – Fig. 15-14, p. 403

• Hyperflexion
• Hyperextension
• Compression injuries
• Axial-rotation injuries
• Penetration

Pathophysiology: of the secondary injury: extension of injury

• Vessel trauma and hemorrhage 
• Impaired cord blood flow  spinal cord hypoxia  ischemia  necrosis

Paralysis of respiratory muscles possible with higher injury – C3 and above are usually fatal if no immediate intervention is taken; can occur with primary or secondary injuries

Complete spinal cord injury
-Blockage of neurotransmission in all tracts below the level of injury caused by:
Severed spinal cord
Intact but non-functional nerve fibers
Complete destruction of neural tissue from lack of blood flow

Incomplete (partial) spinal cord injury
-Portion of spinal cord tracts are intact

Spinal shock: period immediately after traumatic event – cord response to injury
-Complete but temporary loss of sensory, motor, reflex, and autonomic function below the level of injury
-Flaccid paralysis:
Tetraplegia:
Paraplegia
-Loss of temperature regulation below the level of injury  poikilothermia
-Bowel, bladder, and sexual dysfunction
-Hypotension and usually bradycardia from loss of sympathetic vasomotor tone
-Return of reflex activity as spinal shock subsides  hypertonia and spasticity
-Bulbocavernosus reflex – tests for SCI; pull on indwelling catheter or pressure on clitoris or glans penis)

Question 12

Autonomic dyreflexia

Answer 12

medical emergency/life threatening – Fig. 15-18, p. 408
-Usually seen in lesions at T6 or above
Etiology: full bladder, distended rectum, tight clothing (TEDs, SCDs, belts)
Pathophysiology
-CNS control of spinal reflexes is lost 
-Sudden stimulation of sensory receptors below the level of injury  exaggerated reflexive stimulation of the SNS below the level of injury 
-Arteriole vasoconstriction  severe HTN
-Baroreceptor’s sense HTN  stimulate parasympathetic nervous system (PNS) and the vagus nerve 
-Bradycardia and vasodilation above the level of injury 
-Efferent impulses cannot pass through the cord
Manifestations:
-Sudden onset of hypertension with blurred vision, anxiety, and headache (first sign)
-Bradycardia (30-40 beats/minute)
-Sweating above the level of the lesion with flushed skin, nasal congestion, nausea, and
piloerection