Spasticity

Clinic

• Spasticity is an Upper motor Neuron / Pyramidal entity
• It is characterized with excessive velocity-dependent muscle contraction
• Spasticity is an exaggerated stretch reflex
• It is characterized by a velocity-dependent increase in tonic stretch reflexes with exaggerated tendon jerks, resulting from hyper-excitability of the stretch reflex
• It results from the loss of inhibition of UMN, and ends in tightness, stiffness or pull of muscles
• Spasticity naturally depends on Muscle speed and range of motion.
• It manifests itself when the muscle contracts at high speed. This means that when the speed and amplitude of contraction exceeds the threshold, Spasticity occurs
• Depends on the location, Spasticity might cause problem in Movement / Speech or Pain

Diagnostic Characters

• Asymmetric: Because it involves the antagonist muscles
• Velocity-dependent: It increases tonic stretch reflexes and tendon jerks, resulting from hyper-excitability of the stretch reflex

• Strength dependent: Increasing the strength of muscle stretch reflex causes the muscle to contract with greater intensity and power in response to stretching, and this contraction has a direct relationship with the strength of stretching. In this condition, spasticity is occurred.

Entity / Miasm

	GSS	CJD	NVCJD	FFI
Hyper reflexia	+++	+++	+++	+++
Spasm	+++	+++		+++
Hypertonia			+++

Note that here hypertonia is used in its general meaning. Its rubric is spasm.

Causes

• It mostly occurs in CNS disorders affecting UMN in the form of a lesion or syndrome
• It can also be present in various types of multiple sclerosis or neuromuscular cerebral palsy
• Spastic cerebral palsy is the most common form of CP

Mechanism

• One factor that is thought to be related to spasticity is the stretch reflex
• Combination of decreased inhibition and an increased depolarized state of cell membranes, decreases action potential threshold for nerve signal conduction, and thus increases activity of structures innervated by the affected nerves (spasticity).
• Muscles affected in this way have many other potential features of altered performance in addition to spasticity, including
  • Muscle weakness
  • Decreased movement control
  • Clonus
  • Exaggerated deep tendon reflexes
  • Decreased endurance

Related entities

• Clonus
• Fasciculation
• Myoclonus
• Twitching
• Rigidity

Related disease

• Parkinson disease
• MS
• CP