🧠Tone Assessment

Definition And Physiology

Tone is the degree of tension in a skeletal muscle at rest.
It is the physiological resistance offered by the muscle to passive motion.
Tone is maintained by the spinal reflex arc.
Afferent impulses travel from muscle spindle Golgi tendon endings to the spinal cord.
Efferent impulses travel from the anterior horn cell to the muscle.
Tone is regulated by the corticospinal tract and extrapyramidal tract.

Spasticity is present throughout the day, even at rest and during sleep.
Difficulty in putting diapers is highly suggestive of spasticity.
Dystonia is triggered by stimulation, handling, or crying.
Dystonia is absent during rest or sleep.
Dystonia typically presents as an alternating pattern of hypotonia and hypertonia.

Decorticate posture indicates a lesion above the midbrain or in the cerebral cortex.
- Upper limbs are flexed, adducted, and bent inwards over the chest.
- Lower limbs are extended and rigid.
Decerebrate posture indicates a lesion at the brainstem level.
- Upper and lower limbs are fully extended.
- Forearms are hyperpronated with clenched fists and adducted thumbs.
Opisthotonos presents as backward bending of the body like an arc.
Scissoring posture presents with crossed legs due to adductor spasm.
Hemiplegic posture presents with the affected lower limb externally rotated.

Percussion is not directly used to assess resting muscle tone.
Percussion is used to elicit deep tendon reflexes, which are exaggerated in spastic hypertonia and diminished in hypotonia.
Percussion of the thenar muscles using a reflex hammer is used to elicit percussion myotonia.

Ask the child to relax completely.
Move the limbs passively at each joint to assess resistance to stretching.
Examine all four limbs and look for asymmetries.
Ensure the rhythm and rate of passive movement are irregular and unpredictable to prevent voluntary resistance.
Passive pronation and supination of the forearms is the easiest way to assess tone accurately.

Grade 0: No increase in muscle tone.
Grade 1: Slight increase in tone, catch and release, or minimal resistance at the end of range of motion.
Grade 1+: Slight increase in tone, catch followed by minimal resistance throughout the remainder of range of motion.
Grade 2: Marked increase in tone through most of range of motion, but affected parts are easily moved.
Grade 3: Considerable increase in muscle tone, passive movement is difficult.
Grade 4: Affected parts are rigid in flexion or extension.

This assessment is crucial for infants to differentiate central from peripheral hypotonia.
Pull to sit: Deliver traction to the arms from a supine position.
Observe for excessive head lag, which indicates hypotonia.
Ventral suspension: Hold the baby prone, supported by the examiner's hand under the abdomen.
A hypotonic baby will droop over the examiner's hands in an inverted U or rag doll posture.
Vertical or axillary suspension: Hold the baby under the axilla.
A hypotonic child will slip through the hands like a rag doll.
A hypertonic child will exhibit scissoring of the lower limbs.
Forester sign: The child slips through the examiner's arms due to weak shoulder muscles.

Evaluate range of motion using specific angles by visual assessment.
The infant must be calm with the head in the midline.
Stop stretching when the child starts crying.
Scarf sign: Pull the infant's arm across the chest towards the opposite shoulder.
- Normally, the elbow does not cross the midline.
Adductor angle: Abduct both lower limbs as far as possible.
Popliteal angle: Flex thighs to the abdomen and extend both knees simultaneously.
Heel to ear test: Assess the degree to which the heel can be brought to the ear.
Dorsiflexion angle: Flex the foot towards the leg and measure the angle.

Tone Assessment:

Inspection: Left upper limb is in flexion at the elbow joint with the hand clenched. Left lower limb is extended at the knee and internally rotated. Paucity of spontaneous movements noted on the left side. Right side adopts a normal resting posture.
Palpation: Muscles on the left upper and lower limbs feel stiff and firm compared to the right side.
Passive Movements: Increased resistance to passive stretch noted in the left upper limb and left lower limb. Resistance is velocity-dependent.
Clasp-Knife Phenomenon: Elicitable in the left elbow extensors and left knee flexors. Initial catch felt followed by a sudden release.
Flappability: Decreased flappability at the left wrist and left ankle joints.
Modified Ashworth Scale: Grade 2 spasticity in the left upper and lower limbs.
Interpretation: Hypertonia of the clasp-knife type (spasticity) on the left side, suggestive of an upper motor neuron (pyramidal) lesion (Left Hemiplegia).