Definitions and Pathophysiology of Spasticity Definition of

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Definitions and Pathophysiology of Spasticity
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Definition of Spasticity

• Spasticity is a motor disorder characterized by
  a velocity-dependent increase in tonic stretch
  reflexes (muscle tone) with exaggerated tendon
  jerks, resulting from hyperexcitability of the
  stretch reflex, as one component of the upper
  motor neuron syndrome. -- Lance, 1980
• Tonic Stretch Reflex
• Tonic muscle response to vibratory stretch
• Tonic response to a phasic stimulus
• Thus spasticity velocity-dependent increase of
  muscle response to phasic stretch, routinely
  tested by tendon taps or passive mobilization

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What is spasticity

• Velocity dependent tonic stretch reflex
• Resulting from abnormal processing of
  propioceptive input
• In response to stretching the muscle
• Other influences
• Nociceptive
• Loss of reciprocal inhibition

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Terminology

• Spasticity
• Motor disorder
• Velocity-dependent increase in stretch reflexes
• One component of the upper motor neuron (UMN)
  syndrome

• UMN Syndrome
• Positive symptoms
• Increased tone
• Clonus
• Released flexor reflexes
• Negative symptoms
• Loss of dexterity
• Weakness

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Upper Motor Neurone Syndrome

• Spastic Dystonia
• Spastic Paresis
• Symptoms
• Positive Negative

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Features of Spasticity

• Positive Symptoms
• Muscle Tone
• Tendon Jerks
• Repetitive Stretch Reflexes - Clonus
• Extensor St. Reflexes
• Released Flexor Reflexes - Babinski, Mass synergy
  pattern

• Negative Symptoms
• Paresis
• Fine Control
• Dexterity
• Fatiguability
• Early Hypotonia

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Etiologies

• Cerebral palsy
• Stroke
• Multiple sclerosis
• Traumatic brain injury
• Spinal cord injury
• Anoxia
• Neurodegenerative disease

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Vicious cycle

• Spasticity
• Shortened muscle
• Greater activity
• More spasticity
• Spasticity is relieved by stretching
• Clasp knife

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Pathophysiology

• Spinal Reflexes - Afferent Drive
• Efferent Reflexes - Non-Afferent Drive
• Disordered Control of Vol. Movement

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Pathophysiology
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Pathophysiology

• Normal tone is a balance of inhibitory and
  excitatory control
• In spasticity, normal inhibitory control is
  lost/diminished

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Spasticity
INCREASED MUSCLE TONE
MUSCLE SHORTENING
CONTRACTURE
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Pathophysiology of Spasticity

• Not completely understood, despite considerable
  investigation
• Interruption of descending inhibitory pathways
• Rearrangement of spinal circuitry

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Pathophysiology of Spasticity Established
Mechanisms

• Alterations within the reflex arc
• Change in muscle active properties (increased
  ratio torque/EMG)
• Change in muscle passive properties (decreased
  extensibility)
• Decreased pre-synaptic inhibition, at least in
  paraplegics
• Increased fusimotor activity and increased
  excitability of the alpha motor neuron have not
  been established

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Pathophysiology of Spasticity Established
Mechanisms, contd

• Mechanisms affecting the reflex arc
• Decreased reciprocal Ia inhibition on extensors
• Decreased non-reciprocal Ib inhibition
• Decreased inhibition from flexor reflex afferents

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Phenomena Commonly Associated with Spasticity

• Abnormal cutaneous reflexes (Babinski sign)
• Spastic dystonia
• muscle contraction present at rest, dependent on
  tonic stretch
• significant contribution to deformity
• Spastic co-contraction
• abnormal antagonist contraction present during
  voluntary agonist effort, dependent on tonic
  stretch on antagonist
• Extra-segmental co-contraction
• abnormal contraction distant from the muscles
  involved in a voluntary effort

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Phenomena Commonly Associated with Spasticity,
contd

• Other types of muscle overactivity (present with
  yawning, breathing etc.)
• Muscle shortening
• consequence of both immobilization and muscle
  overactivity
• Motor weakness
• significant source of disability

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Disabling Phenomena Associated with Spasticity

• Muscle shortening, motor weakness,
• and stretch-dependent muscle overactivity
• (spastic co-contraction and spastic dystonia)
• are probably the most disabling features in
• spastic patients.
• ? Three logical solutions in therapy
• muscle lengthening, motor training,
• and local muscle relaxation

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Pathophysiology of Impairment After a Central
Nervous System Lesion
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