Spasticity

Spasticity is an entity belonging to Upper motor Neuron series
Spasticity is a combination of
- Paralysis
- Increased tendon reflex activity
- Hypertonia/ Spasm
It is characterized by a velocity-dependent increase in tonic stretch reflexes with exaggerated tendon jerks
Spasticity is resulting from hyper-excitability of the stretch reflex
It results from the loss of inhibition of UMN, and ends in Tightness/ Stiffness of muscles
Spasticity naturally depends on Muscle speed and range of motion.
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

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.

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

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

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

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