Motor System Examination

The motor system examination involves assessing muscle bulk, tone, and power, along with reflexes and coordination.

1. Bulk of Muscle

• Method:

  • Inspection: Examine the patient in lying, sitting, and standing postures, comparing both sides symmetrically. Inspect facial, neck, shoulder, upper arm, forearm, hand (thenar, hypothenar, interossei), hip girdle, thigh, calf, foot, trunk, and paraspinal muscles for wasting or hypertrophy.

  • Palpation: Feel muscles for consistency. Wasted muscles are typically soft and flabby unless fibrosed.

  • Measurement: Use a tape measure at equidistant points from fixed bony landmarks.

    • Mid arm: 10 cm above olecranon.

    • Mid forearm: 10 cm below olecranon.

    • Mid thigh: 18 cm above upper border of patella.

    • Mid calf: 10 cm below tibial tuberosity.

    • A difference of up to 1 cm between dominant and non-dominant limbs is usually not significant.

• Comment on: Symmetrical/asymmetrical, generalized/proximal/distal wasting, specific patterns, and differentiate from thinning (not associated with weakness or reflex loss).

2. Tone of Muscle

Tone is the resistance of a muscle to passive stretch.

• Patient Position: Supine and relaxed, attention distracted.

• Method: Test tone of muscles acting on all major joints before commenting on a limb.

  • Upper Limbs: Perform passive flexion and extension of fingers, wrist, and elbow; supination and pronation of forearm; and abduction and adduction of the shoulder.

  • Lower Limbs: Perform passive flexion and extension of hip, knee, and ankle; and adduction and abduction of the hip.

  • Palpate muscles; hypotonic muscles are flabby, hypertonic muscles are stiff.

• Types of Hypertonia:

  • Spasticity: Velocity-dependent increase in tone, predominantly affecting antigravity muscles (upper limb flexors, lower limb extensors). Characterized by "clasp-knife phenomenon" (sudden release after maximum resistance).

  • Rigidity: Length-dependent increase in tone, uniform resistance in both agonist and antagonist muscles throughout the movement.

    • Cogwheel rigidity: Intermittent release in increased resistance, due to superimposed tremors.

    • Lead pipe rigidity: Uniform resistance throughout the movement.

  • Paratonia/Gegenhalten: Resistance proportional to the applied stretch, seen in frontal lobe dysfunction.

• Hypotonia: Reduced tone, seen in LMN lesions, neuronal shock, and cerebellar lesions.

• Indirect Methods of Testing Tone:

  • Arm Drop: Raise arm and allow it to fall; hypotonic limb falls without resistance.

  • Hand Dangle: Forearm held vertically, hand dangles; angle between hand and forearm is acute in hypotonia (normally 90°C).

  • Wrist Oscillation: Shake hands by holding forearm; more than three wrist oscillations indicate hypotonia.

3. Muscle Power

• Principles: Fix the proximal joint before testing the distal joint. Test main movements about a joint in suspected UMN lesions.

• MRC Grading of Power:

  • 0: No contraction.

  • 1: Flicker of contraction.

  • 2: Movement with gravity eliminated.

  • 3: Movement against gravity.

  • 4: Movement against gravity and some resistance.

  • 5: Normal power.

  • Sub-grades (e.g., 4-, 4, 4+) can be used for more precision.

• Specific Joint Movements, Muscles, Nerve Supply & Testing Methods:

  A. Upper Limb

  • Shoulder

    • Abduction:

      • Muscles: Deltoid, Supraspinatus

      • Nerve Supply: Axillary, Suprascapular

      • Root Value: C5-C6

      • Method: Supraspinatus (C5): Patient tries to initiate abduction from the sides against resistance

        Deltoid (C5) : Patient holds his arm abducted at 60 degree against examiners resistance

    • Adduction:

      • Muscles: Pectoralis major, Latissimus dorsi, Teres major

      • Nerve Supply: Pectoral nerves, Thoracodorsal, Lower subscapular

      • Root Value: C5-T1

      • Method: Ask the patient to adduct their arm (bring it towards their body from an abducted position), and the examiner then applies resistance against this movement

    • Flexion:

      • Muscles: Deltoid, Biceps, Coracobrachialis, Supraspinatus

      • Nerve Supply: Axillary, Musculocutaneous, Suprascapular

      • Root Value: C5-C6

      • Method: Patient flexes arm forward, examiner applies resistance.

    • Extension:

      • Muscles: Latissimus dorsi, Deltoid, Teres major

      • Nerve Supply: Thoracodorsal, Axillary, Lower subscapular

      • Root Value: C5-C8

      • Method: Patient extends arm backward, examiner applies resistance.

    • Internal Rotation:

      • Muscles: Subscapularis, Pectoralis major, Latissimus dorsi, Teres major

      • Nerve Supply: Subscapular, Pectoral, Thoracodorsal

      • Root Value: C5-T1

      • Method:

        Arm Positioning:

        • Ask the patient to flex their elbow to 90 degrees.

        • Active Movement: Ask the patient to actively perform the internal rotation. This involves them rotating their arm inwards, bringing their forearm and hand forward and across their body, or towards their stomach (if sitting/standing), without moving their elbow from its position. Observe the range of motion and smoothness. Now perform the same movement against resistance to assess power.

    • External Rotation:

      • Muscles: Infraspinatus, Teres minor, Deltoid

      • Nerve Supply: Suprascapular, Axillary

      • Root Value: C5-C6

      • Method:

        Arm Positioning:

        • Ask the patient to flex their elbow to 90 degrees.

          Active Movement: Ask the patient to actively perform the external rotation. This involves them rotating their arm outwards, bringing their forearm and hand outwards and away from their body, without moving their elbow from its position. Observe the range of motion and smoothness. Now perform the same movement against resistance to assess power.

  • Elbow

    • Flexion:

      • Muscles: Biceps, Brachialis, Brachioradialis

      • Nerve Supply: Musculocutaneous, Radial

      • Root Value: C5-C6

      • Method: Patient flexes elbow, examiner applies resistance.

    • Extension:

      • Muscles: Triceps

      • Nerve Supply: Radial

      • Root Value: C6-C8

      • Method: Patient extends elbow, examiner applies resistance.

  • Wrist

    • Flexion:

      • Muscles: Flexor carpi radialis, Flexor carpi ulnaris

      • Nerve Supply: Median, Ulnar

      • Root Value: C6-C7

      • Method: Patient flexes wrist, examiner applies resistance.

    • Extension:

      • Muscles: Extensor carpi radialis, Extensor carpi ulnaris

      • Nerve Supply: Radial

      • Root Value: C6-C7

      • Method: Patient extends wrist, examiner applies resistance.

    • Radial Deviation:

      • Muscles: Extensor carpi radialis, Flexor carpi radialis

      • Nerve Supply: Radial, Median

      • Root Value: C6-C7

      • Method: Patient deviates wrist radially, examiner applies resistance.

    • Ulnar Deviation:

      • Muscles: Extensor carpi ulnaris, Flexor carpi ulnaris

      • Nerve Supply: Ulnar

      • Root Value: C8-T1

      • Method: Patient deviates wrist ulnarly, examiner applies resistance.

  • Forearm Muscles (implicitly covered by wrist movements and tone)

  • Small Muscles of Hands

    • Finger Abduction:

      • Muscles: Dorsal interossei, Abductor digiti minimi

      • Nerve Supply: Ulnar

      • Root Value: C8-T1

      • Method: Patient abducts fingers against resistance.

    • Finger Adduction:

      • Muscles: Palmar interossei

      • Nerve Supply: Ulnar

      • Root Value: C8-T1

      • Method: Patient adducts fingers against resistance.

    • Thumb Abduction:

      • Muscles: Abductor pollicis brevis

      • Nerve Supply: Median

      • Root Value: C8-T1

      • Method: Patient abducts thumb perpendicular to palm, examiner applies resistance.

    • Thumb Adduction:

      • Muscles: Adductor pollicis

      • Nerve Supply: Ulnar

      • Root Value: C8-T1

      • Method: Patient adducts thumb to palm, examiner applies resistance.

    • Thumb Flexion:

      • Muscles: Flexor pollicis brevis, Flexor pollicis longus

      • Nerve Supply: Median

      • Root Value: C8-T1

      • Method: Patient flexes thumb, examiner applies resistance.

    • Thumb Extension:

      • Muscles: Extensor pollicis brevis, Extensor pollicis longus

      • Nerve Supply: Radial

      • Root Value: C7-C8

      • Method: Patient extends thumb, examiner applies resistance.

    • Thumb Opposition:

      • Muscles: Opponens pollicis

      • Nerve Supply: Median

      • Root Value: C8-T1

      • Method: Patient touches tip of thumb to tip of little finger, examiner tries to break the opposition.

    • Lumbricales (1st, 2nd):

      • Nerve Supply: Median

      • Root Value: C8-T1

      • Method: Patient extends interphalangeal joint while flexing metacarpophalangeal joint, examiner applies resistance.

    • Lumbricales (3rd, 4th):

      • Nerve Supply: Ulnar

      • Root Value: C8-T1

      • Method: Patient extends interphalangeal joint while flexing metacarpophalangeal joint, examiner applies resistance.

    • Interossei (Dorsal):

      • Nerve Supply: Ulnar

      • Root Value: C8-T1

      • Method: Patient spreads fingers and holds against resistance.

    • Interossei (Palmar):

      • Nerve Supply: Ulnar

      • Root Value: C8-T1

      • Method: Patient brings fingers together and holds against resistance.

    • Finger Flexion (DIP):

      • Muscles: Flexor digitorum profundus

      • Nerve Supply: Median, Ulnar

      • Root Value: C7-T1

      • Method: Patient flexes DIP joint, examiner applies resistance to distal phalanx.

    • Finger Flexion (PIP):

      • Muscles: Flexor digitorum superficialis

      • Nerve Supply: Median

      • Root Value: C7-T1

      • Method: Patient flexes PIP joint, examiner applies resistance to middle phalanx.

    • Finger Extension (MCP):

      • Muscles: Extensor digitorum

      • Nerve Supply: Radial

      • Root Value: C7-C8

      • Method: Patient extends MCP joint, examiner applies resistance.

    • Finger Extension (PIP/DIP):

      • Muscles: Lumbricales, Interossei

      • Nerve Supply: Median, Ulnar

      • Root Value: C8-T1

      • Method: Patient extends PIP/DIP joints, examiner applies resistance.

  B. Lower Limb

  • Thigh

    • Extension (Hip Extension):

      • Muscles: Gluteus maximus

      • Nerve Supply: Inferior gluteal Nerve

      • Root Value: L5-S1

      • Method: Patient lies on stomach and tries to extend thigh against resistance.

    • Adduction (Hip Adduction):

      • Muscles: Adductor magnus, longus, brevis, Gracilis, Pectineus

      • Nerve Supply: Obturator Nerve

      • Root Value: L2-L4

      • Method: Patient tries to keep legs together against resistance.

    • Abduction (Hip Abduction):

      • Muscles: Gluteus medius, minimus

      • Nerve Supply: Superior gluteal Nerve

      • Root Value: L4-S2

      • Method: Patient tries to abduct thigh against resistance.

    • Flexion (Hip Flexion):

      • Muscles: Iliopsoas, Rectus femoris, Sartorius

      • Nerve Supply: Femoral, Sciatic Nerve

      • Root Value: L2-L4, L4-S3

      • Method: Patient flexes thigh, examiner applies resistance.

  • Knee

    • Extension:

      • Muscles: Quadriceps femoris

      • Nerve Supply: Femoral Nerve

      • Root Value: L3-L4

      • Method to Test Knee Extension:

        • Patient Position: The patient should ideally be in a supine (lying on their back) position.

          • Instruct the patient to straighten their leg at the knee.

        • Active Movement: Ask the patient to actively perform knee extension. Observe the range of motion and smoothness of the movement.

        • Resisted Movement (for Power Grading):

          • Once the patient performs the active movement, position your hand to apply resistance.

          • Place one of your hands firmly on the patient's distal thigh, just above the knee.

          • Place your other hand on the patient's distal calf or ankle, applying resistance against the extension.

          • Instruct the patient: "Now, try to straighten your leg, and don't let me bend it."

          • Apply steady, gradually increasing resistance against the extension movement. The resistance should be applied in the direction of flexion.

          • Assess the patient's ability to hold the position and move against your resistance.

    • Flexion:

      • Muscles: Hamstrings

      • Nerve Supply: Sciatic Nerve

      • Root Value: L4-S3

      • Method to Test Knee Flexion:

        • Patient Position: The patient should ideally be in a supine (lying on their back) position.

          • Instruct the patient to bend their knee and try to bring their heel towards their buttocks.

        • Active Movement: Ask the patient to actively perform knee flexion. Observe the range of motion and smoothness of the movement.

        • Resisted Movement (for Power Grading):

          • Once the patient performs the active movement, position your hand to apply resistance.

          • Place one of your hands firmly on the patient's distal calf or ankle, just above the heel.

          • Place your other hand to stabilize the thigh, just above the knee, to prevent compensatory movements.

          • Instruct the patient: "Now, try to bend your knee and pull your heel towards your bottom, and don't let me straighten it."

          • Apply steady, gradually increasing resistance against the flexion movement. The resistance should be applied in the direction of extension.

          • Assess the patient's ability to hold the position and move against your resistance.

  • Ankle

    • Dorsiflexion:

      • Muscles: Tibialis anterior, Extensor digitorum longus, Extensor hallucis longus

      • Nerve Supply: Deep Peroneal Nerve

      • Root Value: L4-L5

      • Method: Patient dorsiflexes ankle, examiner applies resistance.

    • Plantarflexion:

      • Muscles: Gastrocnemius, Soleus

      • Nerve Supply: Tibial Nerve

      • Root Value: S1-S2

      • Method: Patient plantarflexes ankle (e.g., stands on toes), examiner applies resistance.

    • Eversion:

      • Muscles: Peroneus longus, brevis

      • Nerve Supply: Superficial Peroneal Nerve

      • Root Value: L5-S1

      • Method: Patient everts foot, examiner applies resistance.

    • Inversion:

      • Muscles: Tibialis posterior, Tibialis anterior

      • Nerve Supply: Tibial, Deep Peroneal

      • Root Value: L4-L5

      • Method: Patient inverts foot, examiner applies resistance.

  • Toes

    • Big Toe Extension:

      • Muscles: Extensor hallucis longus

      • Nerve Supply: Deep Peroneal Nerve

      • Root Value: L4-L5

      • Method: Patient extends big toe, examiner applies resistance.

    • Big Toe Flexion:

      • Muscles: Flexor hallucis longus, brevis

      • Nerve Supply: Medial Plantar Nerve

      • Root Value: L5-S1

      • Method: Patient flexes big toe, examiner applies resistance.

    • Lateral 4 Toes Extension:

      • Muscles: Extensor digitorum longus, brevis

      • Nerve Supply: Deep Peroneal Nerve

      • Root Value: L4-S1

      • Method: Patient extends lateral toes, examiner applies resistance.

    • Lateral 4 Toes Flexion:

      • Muscles: Flexor digitorum longus, brevis, Quadratus plantae, Lumbricales

      • Nerve Supply: Lateral Plantar Nerve

      • Root Value: S1-S2

      • Method: Patient flexes lateral toes, examiner applies resistance.