What is spasticity

Spasticity is a motor disorder characterized by muscle hyperactivity (or hypertony). It produces involuntary contraction of the involved muscles.

Definition

Lance's Lance JW. Symposium synopsis. In: Feldman RG, Young RR, Koella WP, eds. Spasticity: disordered motor control. Chicago: Yearbook Medical 1980: 485-94. widely accepted definition of 1980 states: "Spasticity is a motor disorder characterized by a velocity-dependent increase in tonic stretch reflexes The stretch reflex (“myotatic reflex”) is an automatic (or “reflex”) muscle contraction in response to an unexpected stretching within the muscle. It is sought for during every neurological examination. The most known reflex is the patellar reflex (“knee-jerk): with the knee flexed and the thigh muscles relaxed, percussion of the patellar ligament causes leg extension by reflex contraction of the quadriceps muscle.
Stretch reflexes are exagerated in brain and spine lesions, especially in spasticity.(“muscle tone”) with exaggerated tendon jerks, resulting from hyper-excitability of the stretch reflex, as one component of the upper motoneuron* syndrome."
The SPASM Consortium (2006) produced a simpler definition:"Assuming that all involuntary activity involves reflexes, spasticity is an intermittent or sustained involuntary hyperactivity of a skeletal muscle associated with an upper motoneuron* lesion."

Spasticity is elective.
It involves only certain muscles.
In the upper limb, these are usually the adductor muscles (bringing the arm alongside the trunk), the flexor muscles (flexion of the elbow, the wrist and the fingers), and the pronator muscles (bringing the palm of the hand face down).
In the lower limb, it affects mainly the adductor muscles (bringing the legs close to each other), the flexor muscles of the hip and knee, and the muscles which extend the foot and rotate it inwards.
Non-spastic muscles are usually weak or paralysed.

Spasticity is elastic.
The more one tries to fight it, the more it increases. But it finally gives way, and the joint can be moved all the way, unless there is some muscle (or joint) contracture associated.

The stretch reflex is increased in spastic muscles, and can produce a ClonusInappropriate recruitment of a muscle upon activating the muscle producing the opposite movement (antagonist). (example: co-contraction of the triceps when activating the biceps prevents flexion of the elbow).A clonus is a series of involuntary rhythmic muscle contractions. Unlike abnormal movements, it does not occur spontaneously, but is initiated by a reflex..

Spasticity is variable.
It increases with cold temperatures, emotions, fatigue. It is often milder at rest, and can disappear during sleep, if there is no associated muscle contracture.

How do we measure it?

Measurement of spasticity is essential to assess the response to treatment. But it is difficult to measure because of its multifactorial nature. Different methods are available for measurement but none of them is precise and reliable enough to quantify the severity of spasticity clinically.

-    Ashworth scale (1964), modified by Bohannon and Smith Bohannon RW, Smith MB. (1987)
Interrater reliability of a modified Ashworth scale of muscle spasticity. Phys Ther 67:206-7. (1987) is validated only for the lower limb.

-  The Tardieu scale a. Tardieu G, Shentoub S, Delarue R. (1954)
A la recherche d’une technique de mesure de la spasticité. Revue Neurol 91:143-4.

b. Gracies JM, Burke K, et al (2010)
Reliability of the Tardieu Scale for Assessing Spasticity in Children With Cerebral Palsy. Arch Phys Med Rehab. 91, 3: 421-428 measures the maximal angle obtained by mobilization of the joint by the examiner during as slow a movement as possible (V1), under gravitational pull (V2) and at a fast rate (V3: angle at which the examiner feels a “catch” in the muscle).

Spasticity may be associated with muscle / joint contractures, and with abnormal movements.

What is muscle contracture?

It is a consequence of spasticity. The muscle itself and its envelope (fascia) become permanently contracted, or tight. It becomes impossible to extend the involved joint fully.
Physiotherapy and splinting are important to prevent muscle contracture. But when it is established, it may require surgery.

What is an abnormal movement?

Not all spastic patients are affected by abnormal movements
Abnormal movements occur spontaneously and are not controlled by the patient . They can occur either when the patient is at rest (chorea, athetosis), or during voluntary movement (dyskinesia, dystonia) .

 Distonia

Is sensation affected?

Sensation is affected in most, but not all cases. In cerebral palsy, the sensation of touch is generally unaffected, but complex sensations (sense of the position of the fingers [proprioception], recognition of an object placed in the hand [stereognosis]…) are often altered.