Neuromuscular Disorders

Question 1

Primary Myopathy

Answer 1

• Weakness (proximal > distal; ex: deltoid, ilopsoas, hip flexors)
• Normal reflexes
• Normal tone
• Muscle atrophy may occur with disease progression

Question 2

Neuromuscular Junction Disorder

Answer 2

• Weakness which fatigues → fluctuates throughout the day: Can feel good in the AM, then slur your words later
• Normal reflexes
• Normal tone
• No muscle atrophy
• e.g., Myasthenia Gravis

Question 3

Peripheral Neuropathy

Answer 3

• These nerves have a motor and sensory component so there will be motor and sensory deficits
• Longest nerves affected the most
• Muscle weakness (distal > proximal)
• Sensory loss (usually a stocking/glove distribution)
• Parasthesias, dysesthesias (can be very painful or absent feeling)
• Decreased or absent reflexes

Question 4

Myasthenia Gravis

Answer 4

• Most common NMJ disorder

Mech: Autoantibodies (made in thymus) to postsynaptic Ach receptor

Clinical:

• Ptosis
• Diplopia
• Weakness that worsens with muscle use

Dx: Repetitive stimulation testing

Tx: Acetycholinesterase Inhibitor; Immunosupression; thymectomy

Question 5

Inflammatory Myopathies

Answer 5

• Polymyositis
• Dermatomyositis
• Inclusion body myositis

Question 6

Polymyositis

Answer 6

• inflammatory myopathy with Proximal weakness, dysphagia, weakness of neck flexion
• NO SKIN RASH
• Inflammatory injury to heart
• Endomesial inflammation with invasion of non-necrotic fibers

Question 7

Dermatomyositis

Answer 7

• inflammatory myopathy that is similar to polymyositis, but younger onset and more systemic disease
• WITH SKIN RASH (Heliotrope rash on face)

Question 8

Inclusion body myositis

Answer 8

• inflammatory myopathy that has slowly progressive proximal and distal weakness
• Involves quads and finger flexors first
• Late adulthood onset
• Doesn’t respond to immune modulation therapy

Question 9

Amyotrophic Lateral Sclerosis

Answer 9

• Degeneration of UMN (Lateral corticospinal tract) and lower motor neurons (Anterior motor horn)
• Mixture of atrophy, hyper- and hyporeflexia, fasciculations
• Atropy and weakness of hands is an early sign
• Normal sensation; the lack of sensory impairment distinguishes ALS from syringomyelia (loss of Pain & Temp)

Question 10

Poliomyelitis

Answer 10

• Damage to the anterior motor horn due to poliovirus infection
• presents with lower motor neuron signs

Question 11

Duchenne’s muscular dystrophy

Answer 11

• X-linked recessive
• Absence of dystrophin gene: results in muscle wasting and replacement of skeletal muscle with adipose tissue
• Onset in childhood → delayed walking, calf hypertrophy
• Toe walking, waddling, lordosis
• Gower’s sign: use his hands and arms to “walk” up his own body from a squatting position due to lack of hip and thigh muscle strength –> indicates proximal weakness

Question 12

Guillain Barre syndrome

Answer 12

• Acute inflammatory demyelinating polyneuropathy: autoimmune destruction of Schwann cells
• Ascending paralysis beginning in lower extremities
• Respiratory compromise
• Autonomic dysfunction
• almost all patients survive, with complete recovery after weeks to months

Question 13

Wallerian degeneration

Answer 13

• nerve fiber is cut or crushed from neuron cell body
• Leads to degeneration of the separated axon distal to the injury
• Conduction is blocked

Question 14

Segmental demyelination

Answer 14

• loss of myelin around axon
• Increased distal latency
• Conduction velocity is reduced

Question 15

Axonal degeneration

Answer 15

• usually due to toxins
• Results decreased amplitude of signal
• Speed of conduction is normal