How To Do The Motor Examination | Merck Manual Professional Version

Summary

This video script provides a detailed guide for assessing the motor system during a physical examination. It covers a range of assessments, including inspection for muscle asymmetry, strength testing for various body parts, and checks for muscle tone and fine motor movements. The exam progresses from neck strength to limb and lower extremity assessments, ensuring a comprehensive evaluation. Special attention is given to subtle signs like pronator drift and muscle fasciculations, while also testing coordination and proprioception. The script emphasizes systematic testing to identify weaknesses and motor impairments.

Takeaways

• 😀 Begin the motor exam with inspection for asymmetry, posture, and involuntary movements like tremors or tics.
• 😀 Inspect muscles for atrophy, hypertrophy, and fasciculations, checking both proximal and distal muscles.
• 😀 Test strength on a scale from 0 to 5, starting from the neck and progressing caudally.
• 😀 Pronator drift is an important screen for symmetry and weakness in the arms. Look for subtle downward drift of one arm.
• 😀 To test shoulder strength, have the patient abduct each arm to 90 and 180 degrees, then resist the movement.
• 😀 Test upper arm strength by having the patient flex elbows to 90 degrees and push against resistance.
• 😀 For wrist strength, test extension and flexion. For hand muscles, assess grip strength and interosseous muscle strength.
• 😀 To assess lower extremity strength, test hip flexion, knee flexion/extension, and ankle dorsiflexion/plantar flexion.
• 😀 Check for fine motor movements by assessing the patient's ability to tap the thumb and index finger rapidly.
• 😀 Muscle tone can be tested by passively moving the patient's joints and observing for subtle rigidity, such as cogwheel rigidity.

Q & A

What is the first step in a motor system examination?

The first step in a motor system examination is inspection, which includes looking for asymmetry, posture imbalances, and any involuntary movements such as tremors or ticks.

How should muscle strength be tested during a motor exam?

Muscle strength is tested by assessing resistance to force, with strength graded on a scale from 0 to 5. The exam begins with testing neck strength and progresses caudally to limbs.

What is pronator drift, and how is it tested?

Pronator drift is a sign of subtle weakness. It is tested by having the patient hold their arms out in front with palms up, eyes closed, and holding the position for 20 seconds. A slight downward drift or inward rotation of the hand indicates weakness.

How can shoulder strength be assessed during a motor exam?

Shoulder strength is assessed by having the patient abduct each arm to 90 and 180 degrees, then maintain abduction against resistance. The examiner presses down on the arms to test resistance.

What is the technique for testing elbow flexion and extension strength?

To test elbow flexion and extension strength, the patient should flex their elbows to 90 degrees and push against the examiner's hands for extension, and pull against the hands for flexion.

What method is used to test grip strength?

Grip strength is tested by having the patient forcefully squeeze two of the examiner's fingers and then trying to pull the fingers away. It is important to avoid using three fingers to prevent pain.

How can hip flexion strength be assessed?

Hip flexion strength is tested by having the patient raise one knee from the bed, then applying resistance to the movement. Inability to overcome the resistance indicates weakness.

What is the significance of testing muscle tone during a motor exam?

Muscle tone is tested to detect rigidity, such as cogwheel rigidity. It can be assessed by passively moving the patient's joints and observing for any subtle rigidity, particularly in the wrist or other areas.

How are fine motor movements assessed during the exam?

Fine motor movements are assessed by observing how rapidly and smoothly the patient can tap their thumb and index finger together, or perform wrist rotations to test rapid alternating movements.

Why is it important to compare strength between both sides of the body?

Comparing strength between both sides of the body is crucial to detect any asymmetry or weakness, helping to identify neurological issues or motor dysfunction.