Motor System Examination

  >   Rahul's Noteblog   >   Notes on USMLE facts, Exam Tips, and USMLE Lab Values   >   Motor System Examination

Purpose of Motor System Examination:

The purpose of the motor system examination is two-fold: to find the cause of the etiology and find the site of the lesion (UML vs LML). Motor system examination is done under these headings:


The best way to check for bulk is to look for a bony prominence in the upper or lower extremity, then mark four points equidistant to that point in the top, bottom, left, and right positions. Then, measure the circumference of the circle formed and compare abnormal with normal. Muscle atrophy is an early sign of lower motor lesion and late sign of upper motor lesion.


Tone can help determine whether it is an UMN or LMN lesion. Hypotonia signifies LMN and hypertonia signifies UMN. There are four types of hypertonia that you come across in practice: clasp-knife spasticity (corticospinal tract lesion), cog-wheel rigidity (extra-pyramidal lesion), paratonic spasticity (catatonic patients), hysteria.


This basically means testing the patient's muscle strength. The commonest muscle to test is the serratus anterior.

Muscle power ratings:

1/5 = little twitching of muscle.

2/5 = movement with gravity, not against it.

3/5 = movement with and against gravity very weak.

4/5 = movement with and against gravity but weak.

5/5 = normal.

Now, there are certain etiologies which present with proximal muscle weakness and there are certain etiologies which present with distal muscle weakness.

Common Brain Lesions:

LMN lesion locations:

• Anterior horn cell, peripheral nerve root, peripheral nerve, or muscle.

Neurogenic weakness:

• Lesion in anterior horn cell, peripheral nerve root, or peripheral nerve. Eg., presentation as fasciculations in a weak muscle.

Myogenic or myopathic lesion:

• Lesion in muscle alone (will never have fasciculations).

Inclusion body myositis:

• This is an important *distal* muscle weakness myopathy. This is important because every other myositis presents proximally except inclusion body myositis, which presents distally.


• Contraction is very slow and the relaxation is very slow; never shake hands with a myotonic. You can evaluate a myotonic person by tapping on their thenar and hypothenar muscles.


• Site of lesion is the mid-brain.


If a reflex is gone, the lesion is above that. Hyporeflexia signifies LMN and hyperreflexia signifies UMN. There are five main reflexes: biceps (C5-C6), triceps (C7-C8), knee (L2-L4), ankle (S1), and plantar reflex (Babinski, Oppenheim, and Gordon's reflex). Plantar reflex, if present, indicates UMN lesion; if absent, indicates a neuronal state of shock. Some other reflexes are the jaw reflex (UMN lesion; brain stem injury), corneal lesion (C5; brain stem injury), gag reflex (brain stem injury), cremasteric reflex (L1-L2; cord lesions), anal reflex (S2-S4; cord lesions). Then, there is the abdominal reflex which is elicited when you stroke the abdomen of a patient going laterally to medially, then, the muscle underneath that stroke must contract.

Pendular knee jerk:

• Oscillating knee in knee-jerk; characteristic of cerebellar lesion. Normal power and hyporeflexia are also present.

Ankle reflex:

• Delayed ankle reflex signifies myxedema.

Co-ordination, gait, and abnormal movements:

Co-ordination can be affected cerebellar involvement. In a cerebellar lesion, patient will have ipsilateral and truncal ataxia, gait problems, speech involvement, hyoptonia, pendular knee-jerk, normal power, in-coordination.


• Patient cannot perform repetitive rapid movements; seen in alcoholics.

Tandem walking:

• Patient cannot walk in a straight line.

Romberg test:

• Positive test indicates posterior column involvement.

Corticospinal tract lesions:

Consist of pyramidal and extra-pyramidal tract lesions responsible for motor movements.

Additional Reading:

Random USMLE Facts

1. Random USMLE Facts volume 1-1
2. Random USMLE Facts volume 2-1
3. Random USMLE Facts volume 3-1
4. Random USMLE Facts volume 4-1
5. Random USMLE Facts volume 5-1
6. Random USMLE Facts volume 6-1
7. Random USMLE Facts volume 7-1
8. Random USMLE Facts volume 8-1
9. Random USMLE Facts volume 9-1
10. Random USMLE Facts volume 10-1
11. Random USMLE Facts volume 11-1
12. Random USMLE Facts volume 12-1

General and Systemic Examinations

1. General Examination for Internal Medicine
2. Jugular Venous Distention Workup
3. ER Chest Pain Workup
4. Format for Patient Presentation
5. Pulmonary Examination for Internal Medicine
6. Cardiac Examination for Internal Medicine
7. Abdominal Examination for Internal Medicine
8. Cranial Nerve Reflexes
9. Motor System Examination
10. Random Sensory System Facts
11. Random Stroke Facts

Medical Files & Presentations

1. USMLE Flashcards [Size: 1.9 MB; Format: MS Powerpoint]
2. Otitis Media in Children [Size: 5.4 MB; Format: MS Powerpoint]
3. Irritable Bowel Syndrome [Size: 170 kB; Format: MS Powerpoint]
4. Acid-Base Disturbance: Acidotic or Alkalotic? [Size: 427 kB; Format: PDF]
5. Thrombocytopenia [Size: 2.42 MB; Format: MS Powerpoint]
6. Are Face Transplants Ethical? [Size: 70.2 kB; Format: MS Powerpoint]

USMLE Step 2 CS Videos

1. Video of Cardiology Examination in a Clinical Setting
2. Video of Neurology Examination in a Clinical Setting
3. Video of Pulmonology Examination in a Clinical Setting
4. Video of Musculoskeletal Examination in a Clinical Setting
5. Video of Abdominal Examination in a Clinical Setting
6. Video of HEENT Examination in a Clinical Setting
7. Video and Description of Rinne Hearing Test
8. Video and Description of Weber Hearing Test

USMLE Laboratory (lab) Values

1. USMLE Blood Lab Values
2. USMLE Cerebrospinal Lab Values
3. USMLE Hematologic Lab Values
4. USMLE Sweat and Urine Lab Values

Medical Images

Useful Medical Images & Diagrams (link opens in a new window)

Random Pages:

The Existence of Matter How to Stop Feedback Form & Guestbook Spam
Video of me playing Titanic Piano Theme: The Portrait Notes on Female Reproductive System
Video of Musculoskeletal Examination in a Clinical Setting Notes on Bacteriodes and Prevotella
Notes on Pyruvate Metabolism Notes on Hypothesis Testing
Differentiation and Anatomy of a Blastocyst Diagram of Gastric Blood Supply
Notes on Basic Gastrointestinal Physiology What is Time?
Why is it hard to find Christian husbands? What is an ELEK`s Test?
Why did I decide to become a doctor? Medical School Admissions Essay Video: Titanic Piano Theme: The Portrait
Corporate Failure: The Enron Case My Experience during the Iraqi Invasion of Kuwait
USMLE Blood Lab Values Regulation of Heart Rate by Autonomic Nervous System
Images of Antibodies Video of me playing Titanic Piano Theme: The Portrait
Notes on Renal/Urinary System Differentiation and Anatomy of a Blastocyst
Notes on Cell Components Notes on Nervous Tissue
Voices from Hell: My Experience in Mussoorie, India Video of Cardiology Examination in a Clinical Setting

Please Do Not Reproduce This Page

This page is written by Rahul Gladwin. Please do not duplicate the contents of this page in whole or part, in any form, without prior written permission.