Neuromuscular Diseases

Question 1

Gower’s sign

Answer 1

a characteristic feature of neuromuscular disease or myopathy. Involves having to use your hands to get off the floor and then climbing over your legs.

Question 2

Ptosis

Answer 2

muscle fatigue…present in diseases such as myasthenia gravis where pts presesnt with “lid Lag” where the eyelids become tired

Question 3

He wants us to know the anatomical location of different neuromuscular diseases

Answer 3

ok

Question 4

Anterior Horn is affected in:

Answer 4

SMA and ALS….spinal muscular atrophy, amytrophic lateral sclerosis

Question 5

Peripheral nerves (peripheral neuropathy)

Answer 5

Demyelinating neuropathies or axonal neuropathies

Question 6

In polyneuropathy, there is distal muscle wasting and weakness. These patients also typically have decreased sensation and depressed reflexes.

Answer 6

In contrast, patients with motor neuron diseases typically do not have sensory deficits

Question 7

Mononeuropathy

Answer 7

a disorder that affects an individual nerve.

Question 8

Slide numer seven is bigtime

Answer 8

ok

Question 9

Normal shape of muscle fibers?

Answer 9

polygonal

Question 10

What is electromyography

Answer 10

Detects the number and size of motor unit action potentials. close to a needle electrode inserted into a muscle.

Question 11

Motor neurons innervate either type one or type 2 muscle fibers. Each motor neuron only innervates one type of fiber.

Answer 11

yup

Question 12

Type 1 muscle fibers stain

Answer 12

pale

Question 13

Type II muscle fibers stain

Answer 13

dark

Question 14

Most muscles exhibit a checkerboard type pattern which shows a mixture of type one and type two muscles

Answer 14

yeah

Question 15

When a muscle loses its innervation due to some injury, muscle fibers become atrophic and angulated (do not retain the polygon shape). How do these fibers stain?

Answer 15

They stain dark on most stains

Question 16

What is fiber type grouping?

Answer 16

This is a process that occurs when certain nerves have been damaged and can no longer innervate muscle fibers. Axons from other intact neurons sprout and reinvervate these fibers. Because of this, you get groups of muscle fibers innervated by the same motor neuron. This manifests on EMG as a larger action potential, but fewer action potentials

Question 17

What does fiber type grouping look like on histo?

Answer 17

Checkerboard lost. More areas of dark fibers and light fibers clumped together

Question 18

What is the problem in myopathies?

Answer 18

Muscle fibers themselves are ill or non-functional.

Question 19

Know this….

Answer 19

In myopathies, the number of motor units is not decreased because the number of motor neurons or axons is normal. It is the number of individual fibers of the motor unit that are nonfunctional or dead.

Question 20

In myopathies, what do the sick muscle fibers do>

Answer 20

Leak enzymes like creatinine kinase. Common blood test for Serum CK

Question 21

Myopathies are characterized at the most basic level by:

Answer 21

a decrease in the numbe rof muscle fibers per motor unit and, thus, small action potentials!!

Question 22

In myopathy, during voluntary activity:

Answer 22

• potentials are small and short
• In creased number of unit potentials relative to the strength of contraction since a seemingly easy movement requires the participation of tons.
• the number of fibers per motor unit is decreased because some fibers are sick

Question 23

conduction velocity calculation

Answer 23

distance between the two electrodes/ (latency 1- latency 2)

Question 24

Signs and symptoms of myopathies

Answer 24

proximal weakness, normal sensation, normal reflexes, elevated muscle enzyme in serum, small motor unit potentials but normal number of motor units activated (this is because the number of motor neurons and their axons are not reduced, there is just less functional muscle fiber).

Question 25

Floppy infants

Answer 25

congenital myopathies

Question 26

Muscular dystrophies start when?

Answer 26

childhood or later, they are hereditary and caused by protein defects in muscle fiber

Question 27

Myotonic dystrophies are also hereditary and progressive, but they have difficulty relaxing the muscles due to what?

Answer 27

abnormal electical activity….this is called….myotonia

Question 28

Muscular dystrophy affects who, has what inheritance pattern?

Answer 28

affects children, it is x-linked recessive

Question 29

The problem in DMD is

Answer 29

The effected gene does not code for dystrophin protein.

Question 30

DMD causes

Answer 30

progressive muscle weakness, psuedohypertrophy, abnormal heart

Question 31

dystrophin is typically located where?

Answer 31

muscle cell membrane.

Question 32

What does a lack of dystrophin cause

Answer 32

Excessive entrance of calcium which triggers necrosis and atrophy

Question 33

myotonic dystrophies have what type of inheritance and are characterized by what?

Answer 33

autosomal dominant diseases, characterized by weakness and myotonia

Question 34

Inflammatory myopathies

Answer 34

acquired diseases that are mostly autoimmune but some are caused by infection

Question 35

metabolic myopathies are:

Answer 35

disorders of glycogen, lipid metabolism, or the mitochondrial respiratory chain.
They are caused by enzyme deficiencies that blocks a metabolic pathway. This deprives cells of energy for muscle contraction and relaxation and to maintain membrane integrity. Some of them manifest by weakness, but the majority of them manifest by muscle pain and breakdown (rhabadomyolysis and excretion of muscle prteins in the urine (myoglobinuria)

Question 36

McArdle’s disease is:

Answer 36

muscle pain during exercise caused by: muscle phosphorylase deficiency which means that glycogen cannot break down during exercise to produce ATP, lactate and pyruvate necessary for oxidative metabolism

Question 37

Endocrine disorders cause what type of muscle weakness?

Answer 37

proximal

Question 38

Biopsy of muscle in endocrine disorders shows

Answer 38

type II muscle fiber atrophy

Question 39

Myasthenia gravis is a disease caused by what?

Answer 39

autoantibodies to acetylcholine receptors

Question 40

Know Eaton Lambert Syndrome

Answer 40

ok

Question 41

What is weird about ALS as a motor neuron disease in regards to the pattern of weakness and the Motor Reflexes?

Answer 41

Pattern of weakness is typically Asymetrical in ALS whereas in most it is symetrical. Also the muscle reflexes are increased.

Question 42

What is central to the Muscular atrophy encountered in DMD?

Answer 42

Calcium activated neutral proteases which are activated when calcium enters the cell

Question 43

In Lambert Eatons Syndrome, why are the salivary glands affected?

Answer 43

Because neuromuscular transmission (Nicotinic receptors) is not the only transmission affected. The antibodies which block the PRE-synaptic ion channels in the neuromuscular pathway also block the channels of the autonomic pathway (muscarinics) which controls salivation.