Lecture 26: Clinical 3: Reflexes & muscle tone

Question 1

Reflex muscle contraction when the muscle is lengthened (prevent overstretch) & consists of… _______ and ______

Answer 1

Reflex muscle contraction when the muscle is lengthened (prevent overstretch) & consists of:

• Phasic stretch reflex
  
  • Tendon jerk/reflex
  • Brisk, brief
• Tonic stretch reflex
  
  • Passive bending – tone
  • Weaker, long-lasting

Question 2

Describe Tendon Jerks

Answer 2

• Involuntary
• Stereotyped (same jerks)
• Non-fatiguing (no decrease in power)
• Response determined by stimulus strength
• Normal v_ariations between individual_s, look for symmetry of an individual!
• ↑ by muscle activation in same segment & other muscles, called reinforcement, e.g. clenching the teeth.
• Reinforcement is used to confirm absent/reduced reflexes.

Question 3

What nerve/nerve roots are associated with Jaw jerk?

Answer 3

Trigeminal

Question 4

What nerve/nerve roots are associated with the following

Biceps

Brachioradialis (supinator)

Triceps

Answer 4

C5/C6

C5/C6

C6/C7

Question 5

What nerve/nerve roots are associated with the following

Finger

Answer 5

C8

Question 6

What nerve/nerve roots are associated with the following

Knee

Ankle

Answer 6

L3/L4

S1

Question 7

Describe the Grading reflexes

Answer 7

Grading reflexes allows:

• Comparison between different examiners
• Reflex changes to be followed over time

If normal, relaxed shows +, reinforcement (clench teeth) shows ++.

Question 8

If there was UMN lesion. what would you observe? (7)

Answer 8

1. No wasting
2. No fasciulation
3. Increased tone (spasicity)
4. Reduced power
5. Increased tendon reflexes
6. Extensor plantar response (babinski reflex)
7. Rapid alternating movements is reduced

Question 9

If there was a Lower Motor Neuron lesion, what would you observe?

Answer 9

• Some wasting
• May be fasciulations
• Normal or decreased tone (Hypotonia)
• Reduced power
• Decreased or absent t_endon reflexes_
• Flexor plantar response (normal reflex)
• Rapid alternating movements is Normal

Question 10

If there was an Extra-pyramidal lesion, what would you observe?

Answer 10

1) No wasting
2) No fasciulation
3) Increased tone (rigidity)
4) Normal power
5) Normal tendon reflexes
6) Flexor/normal plantar reflex
7) Reduced alternating movements

Question 11

What are fasciulations?

Answer 11

Fasciculation is a brief spontaneous contraction affecting a small number of muscle fibres, often causing a flicker of movement under the skin

Question 12

What is rigidity?

Answer 12

Rigidity is an increased resistance to passive movement of a joint which is constant throughout the range and speed of joint displacement.

Question 13

What is spasticity?

Answer 13

Spasticity is an increased resistance to passive movement of a joint which varies with amplitude and speed of displacement of a joint.

Question 14

What are some abnormalities in reflexes?

Answer 14

Question 15

If you see reduced or absent tendon reflexes what are SOME areas where the lesion can have occured?

Answer 15

• Afferent (sensory) nerve
• Cell body of motor neuron (anterior horn cell)
• Efferent (motor) nerve
• (Muscle)

Question 16

What is tone?

Answer 16

Tone is resistance of a muscle to passive lengthening

Components of tone:

• Muscle elasticity
• Neural (tonic or stretch reflex)

Assessed by passive flexion and extension of limb at varying speeds

Question 17

What are some abnormalities of tone?

Answer 17

Question 18

Describe spasticity

Answer 18

Depends on the speed of muscle stretch:

1. Slow stretch has little resistance;
2. Faster stretch has ↑ resistance;
3. Rapid stretch has ↑ resistance then sudden loss of reflex contraction (“clasp knife”).

Question 19

What would you see if there were lesions in the brain?

Answer 19

CNS lesions result in:

• ↑ tone (spastic)
• ↑ reflexes
• ↓ sensation
• Extensor (up-going) plantar response (Babinski reflex)
• Look for symmetry on CT scan. Area of increased signal appears white. Note that coronary plexuses is white (normal).*
• Golf ball size mass affecting on right lateral ventricle. There is intracerebral haemorrhage with intraventricular extension.*

Question 20

There was a lesion at the C5 of the spinal cord.

What would you observe on each of the limbs/peripheries?

Answer 20

Are the reflexes and tone increased/decreased?

• ↓ tone and reflexes at level of the lesion -> compress nerve roots (LMN)
  
  • Absent biceps (C5/6) & brachioradialis (C5/6) jerks
  • ↓ tone at the elbow
• ↑ tone and reflexes below the lesion -> compress spinal cord (UMN)
  
  • ↑ triceps (C7) & finger jerks (C8)
  • ↑ knee (L3/4) & ankle jerks (S1)
  • ↑ tone in legs (spastic)

There is CSF (white) on each side of spinal cord (black). Loss of CSF signal at C4-6 level with spinal cord looking indented/pitched. There is a disk lesion compressing the spinal cord. Always worse on side than the other.