Lecture 13 Abnormal Muscle Tone

Question 1

Lower motor neuron lesions AND acute CNS lesions can cause ___________

Answer 1

Hypotonia/flaccidity

Question 2

resistance to stretch in resting muscle

Answer 2

muscle tone

Question 3

complete lack of resistance to passive stretch

Answer 3

flaccidity

Question 4

abnormally low/less than normal resistance to passive stretch

Answer 4

hypotonia

Question 5

in an awake person, with a normal neuromuscular system, slight muscle resistance to passive stretch is normal

Answer 5

normal

Question 6

hypertonia has two subcategories

Answer 6

spasticity and rigidity

Question 7

velocity dependent resistance to passive stretch

Answer 7

spasticity

Question 8

non velocity dependent increase in resistance to passive stretch

Answer 8

rigidity

Question 9

abnormally strong resistance to passive stretch

Answer 9

hypertonia

Question 10

Chronic (after spinal shock has resolved) upper motor neuron lesions and basal ganglia lesions will cause…

Answer 10

Hypertonia/spasticity

Question 11

what two mechanisms cause UMN overactivity?

Answer 11

1. absence of corticospinal/ reticulospinal inhibition onto LMNs
2. BS UMN overactivity

Question 12

The lack of inhibition of which tracts causes hypertonicity (spacticity), when impacted by an upper motor neuron lesion?

Answer 12

Reticulospinal and corticospinal

Question 13

Normal muscle rigidity : Resistance to passive mvmt is ____________ no matter how fast/slow you try to move the body part

Answer 13

Resistance to passive mvmt is constant no matter how fast/slow you try to move the body part

Question 14

cog wheel rigidity is a combo of

Answer 14

-lead pipe rigidity and tremor

Question 15

is cog wheel seen in BG disorders like Parkinsons?

Answer 15

yes

Question 16

Some basal ganglia disorders can cause cogwheel rigidity, which is….

Answer 16

When passive movements of a muscle trigger start-stop ratchet-like rigidity

Question 17

Gegenhalten

Answer 17

Resistance to passive stretch that remains constant no matter how fast/slow you move it

Question 18

where is gegenhalten seen

Answer 18

severe dyspraxia, apraxia, dementia

Question 19

Identify

Answer 19

Decerebrate

Remember more “E”s in the word for extension

Damage between brainstem and the midbrain/pons

Question 20

Identify

Answer 20

Decorticate
flexed elbows
Damage to superior midbrain or severe B lesions of cortex

Question 21

Spasticity definition

Answer 21

intermittent or sustained involuntary hyperactivity of a skeletal muscle associated with an upper motor neuron lesion

Question 22

Normal progression of UMN lesion:

Answer 22

Spinal Shock (flaccidity) -> spasticity

flaccid –> decreased mvmt –> adaptations –> myoplasticity or neural overactivity –> spasticity

Question 23

What are the 2 hallmarks of spasticity?

Answer 23

Increased velocity dependent muscle tone

Tendon jerk (deep tendon reflex - DTR) hyperreflexia

Question 24

Clonus definition

Answer 24

involuntary, Repetitive reflex contraction of single muscle
Can be sustained or unsustained

Question 25

What is the clasp-knife phenomenon

Answer 25

an initial resistance when attempting passive movement of the extremities, followed by a rapid decrease in resistance. Indicates UMN lesion

Question 26

Biomechanical factors of spasticity

Answer 26

Changing viscoelasticity of muscle Muscles and tendons become stiff Reduced # of sarcomeres in proportion to reduced length in chronic stages HIGH risk of contractures PROM and/or AROM may still remain normal if no fixed shortening or contracture

Question 27

Weak ________ binding can contribute to spasticity

Answer 27

Actin-Myosin

Question 28

Benefits of spasticity

Answer 28

Maintain postural Maintain muscle mass Maintain bone mineralization Reduce dependent edema Prevent deep vein thromboses

Question 29

Spasticity arises when pyramidal tract is interrupted at: _____ , ______ , _______

Answer 29

Cortex Corona radiata Internal capsule

Question 30

What tract is inhibitory for spasticity?

Answer 30

Dorsal Reticulospinal

Question 31

What tracts are excitatory for spasticity?

Answer 31

medial reticulospinal and vestibulospinal Note: Dorsal reticulospinal is inhibitory

Question 32

True or false: Lesions of primary motor cortex alone will produce spasticity

Answer 32

false

Question 33

Lesions must include the ____________ cortex to produce spasticity

Answer 33

pre-motor cortex

Question 34

Why do lesions of the **anterior limb of the internal capsule** produce spasticity?

Answer 34

Because fibers of supplementary motor cortex pass through here

Question 35

Where in the internal capsule is the corticobulbar tract found?

Answer 35

Genu

Question 36

Describe the contents of the posterior limb of the internal capsule

Answer 36

Has the Corticospinal tract inside With the UE in the anterior portion Trunk in the middle portion and LE in the most posterior portion

Question 37

Where does the cortico-reticular tract arise?

Answer 37

premotor and supplementary motor areas

Question 38

Reticulospinal tract projects to __________ in SC

Answer 38

Motor neurons and interneurons

Question 39

ventromedial reticular formation is this formation excitatory or inhibitory?

Answer 39

Inhibitory

Question 40

What inhibits the spinal stretch reflex (DTR)

Answer 40

ventromedial reticular formation

Question 41

Excitatory system – diffuse/extensive areas in midbrain, pons, and bulbar medullary reticular formation These systems facilitate ______ and ___________ but they inhibit __________

Answer 41

Facilitate: Extensors (anti-gravity muscles) + DTR Inhibit: Flexors

Question 42

The lateral coritcospinal tract inhibits the __________

Answer 42

reticulospinal tract The lateral corticospinal tract (CST) inhibits the reticulospinal tract mainly through direct inhibition of spinal interneurons and indirect modulation via the corticobulbar tract. This inhibitory relationship helps ensure that fine voluntary movements controlled by the lateral CST are not disrupted by the automatic postural movements managed by the reticulospinal tract. This balance allows for smooth and coordinated motor control.****

Question 43

Excessive reticulospinal drive (lack of lateral corticospinal) can cause

Answer 43

Contracture, spasticity

Question 44

Cell bodies of gamma motor neurons are located where?

Answer 44

Ventral horn

Question 45

Increased fusiform drive from reticular formation -> hyperactivity of _______ -> Increased muscle spindle sensitivity

Answer 45

Gamma Motor Neurons

Question 46

True or false: During spinal shock you will have exxagerated Deep tendon reflexes

Answer 46

False, they will be absent

Question 47

What are examples of enhanced cutaneous reflexes due to lack of supraspinal inhibition?

Answer 47

Babinski sign Flexor Withdrawal reflex

Question 48

True or false: Spasticity can be triggered by both non-nociceptive and nociceptive input

Answer 48

True

Question 49

What will a nerve conduction velocity test show when you have spasticity?

Answer 49

Nothing because spasticity is a CNS problem but NCV tests the PNS -Bryan Yu, SPT 2024