Lecture 4a (Muscular Abnormalities)

Question 1

What is the most profound muscular abnormality associated with SCI?

Answer 1

Muscular Atrophy
(30-80% of that in able bodied individuals)

Question 2

What type of SCI has more pronounced muscular atrophy?

Answer 2

LMN (Cauda Equina) injury is more pronounced since impossible to contract at all even spastic

Question 3

Which fibre type is associated with profound muscle atrophy?

Answer 3

All types (I, IIa, IIx) will have atrophy, but it is most profound in type IIa fibers

Question 4

Why may SCI individuals legs still look similar size even though there is muscular atrophy?

Answer 4

Decrease in fiber is accompanied by increases in interstitial fat which could be maintaining some of the bulk
- Difficult to tell how much atrophy is
present with just a look

Question 5

What is a muscle biopsy?

Answer 5

1. Physician freezes the desired area
2. Needle plunges small piece of muscle up
3. Muscle thinly sliced and dyed
4. Different muscle fiber types and sizes of those fibers can then appear under a microscope

Question 6

How does a SCI affected area appear under the microscope in a biopsy? (1 year)

Answer 6

Small fibers with abnormal distribution of fiber variety

Question 7

What does healthy tissue look like in a muscle biopsy?

Answer 7

Large muscle fibers, good variety of fiber type, able muscle
- Upper limbs may get even more healthy/strong after years due to paraplegia individuals maintaining use, and utilizing even more

Question 8

What does an affected area look like of an individual with a SCI leg biopsy? (19 years)

Answer 8

Even though usually levels off after about a year, sample is almost all fat tissue with little to no muscle fibers, varieties, etc (ASIA A - cannot move legs at all)
- Legs appeared very similar to before, just replaced muscle with fat

Question 9

How long does muscle atrophy last?

Answer 9

Will usually level off after 1-2 years

Question 10

Why is maintaining muscle important? Why does this matter for SCI individuals?

Answer 10

Skeletal muscle is the major player in storage of glucose and maintenance of normal glucose regulation/metabolism
-SCI more susceptible to disorders of altered glucose metabolism like diabetes (4-5x more likely than non SCI individuals

Question 11

What is diabetes? Type 1 vs Type 2?

Answer 11

Increased blood glucose levels (Hyperglycemia) resulting from the body’s inability to store glucose

Type 1:
- The pancreas no longer produces insulin (Born with it)

Type 2 (Relevant to SCI):
- The pancreas doesn’t produce enough insulin OR the body has an impaired response to insulin (Resistance)

Question 12

What does the process of having less muscle in the body leading to higher blood glucose look like in regard to SCI?

Answer 12

1. Food is eaten and broken down into glucose
2. Glucose is released into the blood, and wants to be stored into the muscles as an available energy source (Muscle is a great form of storage for glucose)
3. Insulin is released from the pancreas to bind to the receptors on the muscle and allow for the glucose to be signaled
4. Glucose is then able to be taken into the muscle cells for storage

Having atrophied (less) muscle means that there is:
- Less absorption of glucose into the muscle (Smaller capacity)
- More difficult to get glucose out of blood stream and into the muscle cells since less ability for insulin to open the “entrance” for glucose (More insulin required per glucose to get in)

This leads to higher amount of glucose in the bloodstream making blood sugar levels higher (Also leads to higher amounts of insulin in the body, increasing the insulin resistance, meaning more insulin comes in, etc - feedforward making it harder to store glucose)

Question 13

Does the type of SCI affect the risk of diabetes?

Answer 13

Yes, found higher amounts those with SCI had type 2 diabetes compared to control, and those with tetraplegia had worse glucose tolerance
- Since the higher the injury the more muscles affected, and therefore less storage sites available

Question 14

Why is there a greater risk in SCI of diabetes/what causes this?

Answer 14

1. Loss of muscle mass and the ability to contract them
2. Insulin resistance

Question 15

What is glucose intolerance and how does it affect SCI

Answer 15

An inability to properly store/metabolize glucose
- 62% of individuals with tetraplegia
- 50% of individuals with paraplegia
- 18% of able bodied

Question 16

What is insulin resistance and how does it affect SCI

Answer 16

Inability to respond to and use insulin
- Allows for lesser transport of glucose into muscle and liver and fat into adipose tissue
- SCI are about 3-4x more likely
- Due to decreased muscle mass, not decreased GLUT 4 - glut 4 doesn’t change in amount

Question 17

What is GLUT 4?

Answer 17

Acts like the “Bouncer” and allows for the uptake of glucose into the muscle cells, while the insulin attempts to bring the glucose to the GLUT 4
- Insulin like the friend knowing a bouncer, and insulin resistance means same amount of GLUT 4, just less convincing so needs more insulin to bring in any glucose

Question 18

What can type 2 diabetes lead to as a consequence of an SCI? (Chain reaction)

Answer 18

1. Secondary issues due to increased blood glucose
   - Like kidney failure since the build up of blood sugar can be too much for them to handle when filtering through bloodstream
   - Also peripheral neuropathy (Neural issues in somatic - weakness lower sensation, and autonomic - UTI and ED)
2. Can also lead to secondary problems due to increased fat in the blood which also has difficulty being absorbed
   - leads to conversion into LDL (Bad fats) and therefore an increased risk of CVD

Question 19

How can atrophy be reduced in SCI and why?

Answer 19

1. Resistance training
2. FES (Stim)
3. Body Weight Supported Treadmill Training
   - A 25-50% increase is realistic, will not be able to obtain the 100% back again

May partially be able to reverse glucose intolerance by:
- Increasing muscle mass
- Decrease insulin resistance (Increase insulin sensitivity)
- Increased GLUT 4 content in muscle

Question 20

What else could affect individuals with SCI muscles besides atrophy and decreased strength?

Answer 20

Decreased fatigue resistance
- Internal issues with the muscle itself, not motivational or voluntary force
- Muscles have reduced capabilities not being able to produce as much force after longer periods of time

Question 21

What causes the decreased fatigue resistance in SCI?

Answer 21

Fiber type shift towards type IIx fiber predominance (Fatigable fast twitch)
- Able-Bodied has mostly type 1
- SCI has more than half type 2x

This is also due to reduction in the Na, K-ATPase enzyme, since without this cannot contract as many times

Question 22

What are some ways of maintaining type 1 fibers with SCI?

Answer 22

Spasticity
- Many will try to get rid of spasms but maintain a little more muscle mass as well as type 1 fibers
- Preserve atrophy and fatigability

Question 23

What are some classifications of spasms?

Answer 23

Clonus
- Repetitive contraction of a muscle due to stretch reflex
- Gravity dropping the foot, plantar flexor reflex and then gravity drops and repeats (Almost like bouncing)

Contractures
- Reduced range of motion in a joint due to chronic shortening of muscle
- May not be in spasm, might be physically shortened due to atrophy and can no longer reach full ROM

Question 24

What is the Ashworth test of spasticity

Answer 24

Move the joints of the lower limb and record the amount of resistance (Spasticity) based on a 6 point scale
0. No increase in muscle tone
1. Slight increase catch and release or min resistance at end of ROM
1+. Slight increase catch, NO release, and min resistance for less than half of ROM
2. More marked increase, through most of ROM but still easily moved
3. Considerable increase, passive movement difficult
4. Rigid in flexion or extension

0 is no resistance
4 is stuck at a spot due to spasm or contracture

Subjective to each person, and in an artificial setting, not in their chair so may not be the most accurate test

Question 25

What is a SCI-SET spasticity evaluation tool?

Answer 25

Questionnaire filled out by individual with SCI
- 35 q’s to fill out rating different questions -3 - +3 on how much they are affected over the last week
- Great judge of measuring

Question 26

How can spasms be useful?

Answer 26

Could be helpful to evoke muscle spasticity to stand
- People find ways to manipulate spasms for motor function