Muscle & Nerve Path

Question 1

Peripheral causes of numbness

Answer 1

1. polyneuropathy
2. peripheral entrapment neuropathy
3. Radiculopathies
4. Brachial plexus lesions

Question 2

Can nerves store energy?

Answer 2

Not very much - so much has good circulation to meet the high metabolic demand

Question 3

fibrillations

Answer 3

spontaneous contraction of de-innervated muscle fibers

Question 4

fasiculations

Answer 4

spontaneous discharge of a motor unit due to irritation or damage

Question 5

Amyotrophic lateral sclerosis (ALS)

Answer 5

degeneration of anterior horn cells and upper motor neurons - many genetic factors (SOD is most common mutation)

Question 6

lower motor neuron symptoms

Answer 6

atrophy, fasciculations, decr. reflexes

Question 7

upper motor neuron symptoms

Answer 7

spasticity, incr. reflexes, upgoing toes

Question 8

Primary lateral sclerosis

Answer 8

like ALS but only affects lower motor neurons and has better prognosis (10+ yrs)

Question 9

ALS disease progression

Answer 9

starts unilaterally and spreads to both sides in months, survival is 3-5 yrs, death due to respiratory weakness and infection

Question 10

Tx for ALS

Answer 10

nothing good. Riluzole can delay progression slightly

Question 11

3 patterns of peripheral neuropathy

Answer 11

1. mononeuropathy
2. radiculopathy
3. polyneuropathy

Question 12

Characteristics of mononeuropathy

Answer 12

often due to trauma causing nerve entrapment, presents with paresthesias when the region is tapped (Tinel sign)

Question 13

Causes of radiculopathy

Answer 13

1. intervertebral disc herniation (young)

2. degenerative changes (older)

Question 14

Characteristics of radiculopathy

Answer 14

symptoms follow a well defined pathway, symptoms often caused by stretching or pinching when coughing, sneezing..etc. Usually not a lot of sensory loss bc of degree of overlap with other nerves.

Question 15

polyneuropathy

Answer 15

diffuse peripheral nerve damage

Question 16

What is the most common cause of polyneuropathy?

Answer 16

Diabetes (after that many things can cause it - nutritional deficiencies (B12), infections, toxins, metabolic issues, inflammation…etc).

Question 17

What is Guillain-Barre?

Answer 17

autoimmune syndrome following infectious disease that presents with acute, rapid severe weakeness (polyneuropathy)

Question 18

Mononeuritis multiplex

Answer 18

condition caused by decr. blood flow to nerves or an autoimmune destruction of axon or myelin that can happen most commonly with diabetes in the lumbar plexus. causes decr. patellar reflex

Question 19

Myasthenia Gravis

Answer 19

autoimmune disease against nicotinic receptors at the NMJ. leads to ptosis, diplopia, weakness with sustained or repetitive use of the muscle

Question 20

Lambert-Eaton Syndrome

Answer 20

myasthenic syndrome that may be associated with carcinoma - defective Ca channel leads to hip girdle weakness that progresses. weakness improves with exercise (facilitation)

Question 21

What virus can produce impairment of the NMJ?

Answer 21

C. Botulinum with Botulinum toxin (binds synaptobrevin and blocks Ach release)

Question 22

Classic presentation of myopathies

Answer 22

symmetrical, proximal muscle weakness and incr. muscle enzymes (CK levels). must biopsy to be sure.

Question 23

What are 3 categories of myopathies that cause muscle cell destruction?

Answer 23

1. Muscular dystrophies
2. Metabolic Myopathies
3. Inflammatory Myopathy

Question 24

What are muscular dystrophies?

Answer 24

noninflammatory degenerative conditions of muscle (ex. Duchenne, Becker, facioscapulohumoral, limb-girdle, oculopharyngeal, & myotonic dystrophies)

Question 25

Duchenne and Becker Dystrophies

Answer 25

X-linked recessive disorder due to mutated dystrophin
Duchenne - presents in boys in childhood (kids never run) - death in 20’s due to cardiomyopathy
Becker’s - milder version of Duchenne

Question 26

What are metabolic myopathies?

Answer 26

Myopathies due to thyroid disease, meds, toxins, mitochondrial myopathies - present with exercise intolerance or cramping

Question 27

What is polymyositis?

Answer 27

inflammatory myopathy characterized by insidious, symmetrical onset of proximal weakness in 30-60 yr olds

Question 28

What is dermatomyositis?

Answer 28

polymyositis presentation + red/purple rash (esp over eyelids and joints) - high association with lymphoma and other cancers

Question 29

What is inclusion body myositis?

Answer 29

It is a slowly progressing inflammatory myopathy that often present distally in hands.

Question 30

What are two categories of diseases that cause functional deficits in muscles (channelopathies)?

Answer 30

1. myotonic disorders (2 types - distal and proximal)

2. periodic paralysis

Question 31

What is the difference between congenital myotonia and paramyotonia congenita?

Answer 31

congenital myotonia - sx improve with exercise

paramyotonia congenital - sx worsen with exercise

Question 32

Limb Girdle Dystrophy

Answer 32

Muscual dystrophy that can be caused by many different mutations that progresses slowly and can stop altogether - present in adolescence or early adulthood

Question 33

What is chronic inflammatory demyelinating polyradiculoneuropathy (CIDP)?

Answer 33

It is a condition with relapsing or progressive polyneuropathy that causes asymmetric weakness and sensory loss and is associated with very high CSF protein levels. Reflexes are lost early in this as well as acute IDP bc heavily myelinated fibers are affected first.