EXAMINATION OF MOTOR SYSTEM
EXAMINATION OF MOTOR SYSTEM
Aim: To assess the functional status of the motor system of the given subject.
Requirement: Tape for measurement.
Procedure: The bio-data findings of general examination including higher functions are noted. Then the motor system is examined under the fo! lowing headings.
I. Bulkof muscle
II. Toneof muscle
Ill. Strength of muscle
IV. Co-ordination of movements
VI. Involuntary movements
I. Bulk of Muscle
By just observing the subject, any significant difference in the bulk of muscle between both sides of the body can be assessed. Atape is used to measure the circumference of the limb at the same distance from a non- movable bony prominence, on both sides. The size or bulk of voluntary muscle varies with age, sex, body build, state of nutrition and muscular exercise.
(a) Atrophy: In atrophy or wasting, the muscle becomes small in size. This can occur due to disuse, neurological disorders, joint injury or joint diseases.
(b) Hypertrophy: Here the bulk of the muscle increases eg, muscular dystrophies. In pseudomuscular dystrophy due to pathological changes in the muscles, the muscle bulk increases, but these enlarged muscles are weak inspite of their size.
II. Tone of Muscle
The mild degree of tension or partial state of contraction found in normal healthy muscle is referred to as muscle tone. The tone is assessed by asking the subject to relax completely and then passively moving the joints of the upper and lower extremities. The resistance offered by the muscle during passive movement represents the degree of muscle tone.
(1) Hypertonia: Increase in muscle tone.
a) Spasticity - Seen in upper motor neuron lesions. The muscle tone is increased and is of clasp knife’ type. As the joint is passively flexed or extended, there is increased resistance to begin with, but as the movement is continued the resistance suddenly decreases.
i) Lead pipe rigidity - Characteristic feature of extrapyramidal lesions. Resistance is felt uniformly through out the movement. Here both agonists and antagonists muscles contract.
ii) Cog-wheel rigidity - Here the agonists and antagonists muscles contract alternately and regularly during the passive movement. As there is alternate increase and decrease in resistance the passive movement will be jerky, like the movements of a cog wheel. This is seen in extrapyram idal diseases. iii) Decorticate and Decerebrate rigidity-In decorticate position the upper limb is flexed and the lower limb extended - due to cerebral cortical lesions. In decerebrate rigidity there is extension of all limbs with internal rotation of the upper limb and plantar flexion of the feet.
(2) Hypotonia: Decrease in muscle tone. There is decreased resistance to passive movement there is increased range of movements in the limbs. This is seen in lower motor neuron lesion and cerebellar lesions.
Ill. Strength of the muscle (Power):
The patient tries to contract the muscle against resistance offered by the examiner (active method).