Disorders of Muscle Tone - Week 6

Which statement best defines muscle tone?

A continuous state of muscle contraction at rest that helps maintain posture and joint stability

Which neural structures are identified as primary mechanisms mediating tone?

Extrapyramidal structures (UMN), basal ganglia, pyramidal structures, cerebellum, ventral horn motor neurons (LMN), and peripheral nerves to skeletal muscle (LMN)

Hypotonicity is most directly associated with which pathophysiological source?

LMN lesions and lesions to the posterior cerebellar lobe

Hypertonicity is characterized by which feature?

Increased tone with resistance to movement and association with UMN damage

Which statement differentiates spasticity from general hypertonicity?

Spasticity is velocity dependent and typically involves one side of a joint

Spasticity is commonly associated with which diagnoses?

SCI (T12 and above), TBI, CVA, and CP

Which of the following statements best describes rigidity?

Velocity-independent increased tone present during slow or fast movement

The “clasp knife phenomenon” is best described as:

Severe spasticity that suddenly gives way after sustained stretch

Cogwheel rigidity is commonly associated with which condition and exhibits what characteristic?

Parkinson’s disease; jerky, alternating resistance as muscles contract/relax

Lead pipe rigidity is defined by:

Uniform, continuous resistance to passive movement through entire ROM in all planes

Clonus is most commonly observed in which muscle group, and how is it rated?

Ankle plantar flexors; by number of beats

On the Modified Ashworth Scale, which score indicates “considerable increase in muscle tone, making passive movement difficult”?

3

Which etiology contributes to spasticity by disrupting inhibitory control of the antagonist and synergy muscles?

Reduced reciprocal inhibition

Damage to which regions is listed as contributing to spasticity?

Primary motor area and brainstem supraspinal motor centers

During sustained stretch on a spastic agonist muscle, which receptor is activated and what is the intended effect?

GTO; inhibit agonist and facilitate antagonist

A quick stretch on the agonist primarily activates which structure and produces what effect?

Muscle spindle; continued agonist activation via alpha motor neurons

When aiming to reduce spasticity in the biceps by tendon pressure, where should pressure be applied and why?

On the biceps tendon to activate GTOs and inhibit the contracting agonist

Which orthotic/casting intervention applies sustained stretch to reduce agonist tone and what is a key precaution?

Serial casting; monitor for skin breakdown

Which Deep Tendon Reflex (DTR) scale value corresponds to “very brisk with clonus”?

4

In an adult post‑stroke with marked flexor spasticity at the elbow limiting feeding, which immediate OT technique is most aligned with the lecture’s inhibitory strategies?

Sustained elbow extension stretch to activate biceps GTOs

A child with hypotonia (“floppy baby”) presents with poor UE function. Which technique may temporarily raise tone for functional use per the lecture?

Quick stretch of the agonist to engage muscle spindles

Which feature best distinguishes cogwheel from lead pipe rigidity for clinical documentation?

Cogwheel: jerky, alternating resistance; Lead pipe: uniform, continuous resistance across ROM

Which classification pairing is correct according to the slides?

Rigidity—velocity independent; Spasticity—velocity dependent

For a patient with UMN‑related ankle clonus, which clinical descriptor aligns with the slide guidance?

Record number of beats to quantify severity

Which listed mechanism contributes to the development of spasticity by altering spinal motor neuron activity?

Loss of cortical/subcortical modification of alpha and gamma motor neurons