Spasticity is an UMN problem, Rigidity involves also Biomechanical issues

spasticity involves pyramidal tract and rigidity involves extra pyramidal tract lesion. In contrast to spasticity, rigidity is considered to be independent of hyperactive segmental stretch reflexes, so that tendon jerks and H reflexes are almost normal in subjects without altering to change of velocity.

Can you differentiate between spasticity versus rigidity?

Whenever there is resistance to movement, think of the two most common issues: spasticity and rigidity. Both spasticity and rigidity represent hypertonic states, however both have different causes and characteristics that are important to be aware of.

Spasticity:

• Caused by lesions in the pyramidal tract (i.e. upper motor neurons) such the corticospinal tract
• Stroke
• Spinal cord compression
• Motor neuron disease
• Weakness present
• More resistance in one direction the other direction
• More tone in initial part of movement – “Clasp knife spasticity”
• It is velocity dependent (i.e. more noticeable with fast movements)

· Rigidity:

• Seen in extrapyramidal lesions (i.e. Parkinson’s) is such as the rubrospinal or vestibulospinal tracts
• Subtypes include:
• Cog wheel rigidity (Parkinson’s) – Tremor superimposed on this hypertonia that results in intermittent increase in tone during the movement.
• Lead pipe rigidity (neuroleptant malignant syndrome or less commonly stiff man syndrome) – Uniform increase in tone
• Same resistance in all directions
• Not velocity dependent – does not vary with speed of movement of muscle groups involved

What is Spasticity?

Spasticity in Greek means “pulling”. Spasticity is a condition where a number of muscles suffer continuous contraction, stiffness, and tightness. It is caused by lesions in the pyramidal tract i.e. UMNL (Upper Motor neuron lesion). Spasticity is characterized by spasm, especially the tonic spasm. This kind of stiffness or spasm interferes with the speech, normal movement and gait. Spasticity is uni-directional, i.e. the resilience to motion is only experienced when the joint or a muscle makes a move in some particular direction. Spasticity is a common symptom of a demyelinating disease called as Multiple Sclerosis (MS) and is termed as muscle stiffness. In this disease, the neuron cells of the brain and spinal cord suffer damage. Spasticity is dependent on velocity i.e. it can be noticed with fast movements.

What are the causes of spasticity?

· Spasticity takes place when the messages from the central nervous system are not transmitted properly to the spinal cord and the muscles, due to the degradation of the paths between the brain system, the spinal cord and the muscles being

· It is also caused due to the progressive degeneration of myelin and the nerve fibers.Myelin is a fatty white substance that envelops the axon of nerve cells, forming an electrically insulating membrane.

· Spasticity also takes place due to contraction of the extensor muscles and the flexor muscles that causes pain and weak coordination.

· Multiple sclerosis

· Acquired brain trauma

· Stroke

· Cerebral palsy

· What are the symptoms of spasticity?

· Hypertonicity i.e. rising muscle tone, that causes stiffness, rigidity and dysfunctional bladder.

· Uncontrollable muscle spasms (called clonus)

· Exaggerated tendon reflexes (tense muscles)

· Nocturnal awakening

· Deformity causing difficulty in walking, moving and speech.

· Abnormal positioning of arm, wrist, fingers, and shoulder.

· Involuntary jerky movement.

What is Rigidity?

It is defined as a state of stiffness, inflexibility, and inability to bend, stretch, twist or any deformity under pressure. Rigidity is also known as muscle tension or rigor. Rigidity is mostly bi-directional, i.e. resistance to movement in muscles is felt regardless of speed and course of direction in which the muscles and tissues exhibit their motion. Rigidity can be seen in extrapyramidal lesions, (part of the motor system causing involuntary actions) for example Parkinson’s disease. Parkinson’s disease is a progressive neurological disease which affects movement.

What are the causes of Rigidity?

· Parkinson’s disease

· Wilson’s disease (Autosomal recessive condition inherited of copper metabolism in lungs, liver, brain and other tissues.

· Multiple system atrophy

· DMD (Dystonia musculorum deformans). This is a disease where painful muscle contractions cause exaggerated distortions.

· MNS (Neuroleptic-malignant syndrome). This is a life-threatening disease. It is described as idiosyncratic reaction toneurolepticmedications.

· Catatonia (State of unresponsiveness to external stimuli).

· CJD (Creutzfeldt-Jakob disease i.e. fatal brain disorder).

· Progressive supranuclear palsy or Steele-Richardson-Olszewski syndrome

· Acute cerebral infraction

· Multiple system atrophy (MSA) or Shy-drager syndrome (neurodegenerativedisorder due to dysfunction of autonomic nervous system)

· Basal ganglia infection

· Gegenhalten (involuntary resistance to passive movements).

· lupus, (a chronic inflammatory disease that causes pain and stiffness in the joints)

· Pinched nerves

· Viral and bacterial infections.

· What are the symptoms of rigidity?

· Bradykinesia (impaired ability and slowness of movement)

· Stiff and inflexible muscles

· Pain, severe muscle weakness and muscle cramps

· Decreased movement

· A fixedfacial expression called a “mask”

· Difficulty moving in bed

· Difficulty getting up from a chair

· Trouble in writing, walking and clothe buttoning ·Restlessness and irritability

· Decreased appetite

· Difficulty in breathing

· High fever

Difference between Spasticity and Rigidity

1) Definition Spasticity and Rigidity

Spasticity - Continuous contraction of muscles

Rigidity - The state of stiffness, inflexibility and inability to bend.

2) Type of muscles that are affected

Spasticity commonly affects muscles of legs and arms, neck. Eyelids, face, and vocal chords. It can be also said that spasticity involves only one muscle group i.e. Flexors.

Rigidity can affect any muscle of the body, i.e. both Flexors and Extensors.

3) Velocity dependence

Spasticity depends on velocity. This means that spasticity is more noticeable with fast movements. It exhibits abnormally high muscle tone due to the excitability of the stretch reflex.

Rigidity is not dependent on the velocity of the movement. In this, the resistance of a joint is unaffected by the speed of movement of muscles.

4) Lesions in Spasticity and Rigidity

Spasticity is found in pyramidal tract lesions (Upper motor neuron lesion).

Rigidity is found in extrapyramidal lesions, (i.e. parkinsonism) like the rubrospinal or vestibulospinal tracts.

5) Reflexes

Spasticity covaries with Hyperreflexia. Hyperreflexia is a condition in which involuntary nervous system shows a disordered response to external stimuli. It is caused due to spinal cord lesion or injury.

Rigidity covaries with Hyporeflexia. Hyporeflexia is a condition in which there is weak or diminished reflex in reaction to some external stimuli.

Summary of Spasticity and Rigidity

The points of difference between Spasticity and Rigidity have been summarized below:

Two common cases of resistance to movement are spasticity and rigidity. Both of them demonstrate hypertonic conditions, however, their causes, symptoms, and attributes differ. These two states are elicited while examining the tone of muscle limbs. Spasticity features include clonus and increased reflexes while as the features of rigidity include mental state, alertness, and emotions.

Spasticity depends on velocity. This means that spasticity is more noticeable with fast movements. It exhibits abnormally high muscle tone due to the excitability of the stretch reflex.

Rigidity is not dependent on the velocity of the movement. In this, the resistance of a joint is unaffected by the speed of movement of muscles.