Muscle tone Flashcards
(23 cards)
What is muscle tone?
Muscle tone is the residual tension in a resting muscle that allows it to be ready for movement and maintains posture
How is muscle tone categorized?
Passive tone: Muscle tension at rest, independent of strength.
Active tone: Muscle tension associated with voluntary and spontaneous movements
Why is assessing muscle tone important in newborns?
It reflects the maturation of the nervous system.
Helps identify neurological disorders such as cerebral palsy.
Determines postural control and motor function
What factors influence passive muscle tone?
Resting posture
Passive range of motion
Joint resistance to mobilization
Prevention of excessive joint mobility
How does passive muscle tone develop in utero?
Before 28 weeks: Minimal resistance to passive manipulation.
At 32 weeks: Clear flexion of the lower limbs.
At 36 weeks: Increased popliteal angle and more defined flexor tone.
At 40 weeks: Strong flexor tone with limb adduction
What are common postures in a newborn?
Supine: Flexed limbs slightly elevated from the surface.
Prone: Elevated pelvis and flexed knees.
Upper limbs: Flexed, close to the thorax, tend to move with head rotation
What is the Scarf Maneuver?
Assesses resistance to passive stretching of the shoulder adductors.
The arm is pulled across the chest to see how far the elbow reaches.
Normal response: The elbow does not cross the midline
What is the Arm Recoil Maneuver?
Tests flexor muscle tone in the arms.
The arms are flexed for five seconds, extended, and then released.
Normal response: The arms rapidly recoil into flexion
What is the Arm Traction Test?
Evaluates resistance to passive stretch of the arm flexors.
The examiner lifts the baby by the arms to assess shoulder and elbow resistance
What is the Heel-to-Ear Test?
Assesses hamstring muscle flexibility.
The examiner brings the baby’s heel towards the ipsilateral ear and observes the angle
What does the Popliteal Angle Test measure?
Evaluates passive knee extension.
A larger angle suggests hypotonia, while a smaller angle indicates hypertonia
What is the Leg Recoil Maneuver?
Tests resistance to passive hip and knee flexion.
Legs are flexed, extended, and then released to assess the speed and strength of recoil
What is the Ventral Suspension Test?
Assesses neck and back extensor tone.
The examiner suspends the newborn prone in the air, observing posture and limb positioning
What is active muscle tone?
Active tone refers to muscle tension associated with voluntary movements, rather than passive muscle resistance
What are key maneuvers to assess active tone?
Pull-to-Sitting: Evaluates head control and trunk strength.
Raise-to-Sit: Tests postural control and coordination.
Righting Reactions: Determines postural stability when changing position
What factors influence muscle tone assessment?
State of alertness (drowsy vs. active)
Head position
Muscle contractures
Confusion between muscle tone and strength
What are key signs of hypotonia?
Flat posture
Increased joint mobility
Delayed motor milestones
Reduced resistance to passive movement
What are signs of hypertonia?
Increased resistance to movement
Stiff posture
Reduced joint mobility
Exaggerated reflexes
How does prematurity affect muscle tone?
Preterm infants tend to have lower flexor tone due to a lack of intrauterine confinement.
They exhibit less adduction and flexion in the limbs
What is the clinical importance of the Dubowitz Scale?
Assesses resting posture to determine neurological maturity.
A low score indicates hypotonia, while a high score suggests hypertonia
What are the main passive tone maneuvers?
Scarf Maneuver
Arm Recoil
Arm Traction
Leg Recoil
Heel-to-Ear
Popliteal Angle
Ventral Suspension
What are the main active tone maneuvers?
Pull-to-Sitting
Raise-to-Sit
Back-to-Lying
Righting Reactions
How does muscle tone change with development?
Flexor tone develops caudo-cephalically (from legs to head).
In preterm infants, tone is reduced, but in term infants, flexor tone is strong
