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Upper Limb Neurological Examination for MRCS Part B: Tone, Power, Reflexes and Sensation

By Dr Richard Miller, MBChB FRCS with the MRCS Part B Questions Team · Reviewed 15 September 2026

In brief

Examine the upper limbs in a fixed order: inspection and pronator drift, tone, power graded on the MRC scale, the biceps, triceps and supinator reflexes, sensation by dermatome and modality, then coordination.

The upper limb neurological examination runs in a fixed order: inspection and pronator drift, tone, power, reflexes, sensation and coordination. Compare the two sides at every step, grade power on the MRC scale from 0 to 5 rather than describing it as weak, and say at the end whether the pattern fits a root, a plexus or a peripheral nerve.

Key takeaways

Expose both arms and shoulders fully and compare side with side throughout.
The MRC scale grades muscle power from 0 to 5 relative to the maximum expected for that muscle.
Grade 2 is active movement with gravity eliminated, not simply some movement.
Stanford Medicine 25 gives the reflex roots as biceps and brachioradialis C5 and C6, and triceps C7.
Localise the deficit: a dermatomal pattern suggests a root lesion and a named territory suggests a peripheral nerve.

How is this station marked in MRCS Part B?

A physical examination station is marked out of 20 across four domains: clinical and technical skill carries 8 marks, and clinical knowledge and its application, communication, and professionalism carry 4 marks each. The examiner also gives the station a separate global rating of pass, borderline or fail.

Two things follow from that split. More than half the marks sit outside your knowledge of the condition, so a silent, technically correct examination scores poorly. And you are signalled at six minutes of the nine to present your findings, so the sequence has to finish inside six.

How do I start the upper limb examination?

Gel your hands, introduce yourself, gain consent and ask about pain. Expose both arms to the shoulders and sit the patient so the arms can rest in the lap.

Ask whether the patient is right or left handed.
Inspect for muscle wasting, particularly of the small muscles of the hand and the shoulder girdle.
Look for fasciculation, tremor, abnormal posture, scars and trophic skin changes.
Test for pronator drift: arms outstretched, palms up, eyes closed. Pronation and downward drift on one side indicates a pyramidal weakness on that side.

How do I assess tone?

Ask the patient to relax and let the arm go floppy. Support the limb, then pronate and supinate the forearm, and flex and extend the elbow and wrist, at varying speeds.

**Spasticity** is a velocity-dependent increase in tone, greater on fast movement, and it indicates an upper motor neurone lesion. Rigidity is constant throughout the range and points to an extrapyramidal cause.

How do I test power and grade it?

Isolate each movement, demonstrate it, then apply resistance and compare sides. Work proximal to distal.

Shoulder abduction, C5, with the arms held out like a chicken wing.
Elbow flexion, C5 and C6, and elbow extension, C7.
Wrist extension and flexion.
Finger extension, finger flexion and grip.
Finger abduction, T1, with the fingers spread against your resistance, and thumb abduction for the median nerve.

The MRC scale, published in Aids to the Examination of the Peripheral Nervous System, grades power 0 to 5: 0 no contraction, 1 a flicker or trace of contraction, 2 active movement with gravity eliminated, 3 active movement against gravity, 4 active movement against gravity and resistance, and 5 normal power.

Which reflexes do I test and what are their roots?

Rest the arms in the lap and make sure the patient is relaxed. Strike your own finger over the tendon rather than the tendon directly for the biceps.

Biceps, C5 and C6, with your finger over the tendon in the antecubital fossa.
Supinator or brachioradialis, C5 and C6, over the radial aspect of the forearm a few centimetres above the wrist.
Triceps, C7, with the arm supported and the elbow flexed.
If a reflex appears absent, reinforce it by asking the patient to clench the teeth before you strike again.

How do I test sensation?

Demonstrate each modality on the sternum first so the patient knows what normal feels like, then test with the eyes closed, comparing left with right at each level.

Light touch, using cotton wool, dabbed rather than stroked, tests the dorsal columns and the spinothalamic tracts.
Pin prick, using a disposable neurotip, tests the spinothalamic tract. Dispose of the tip after a single patient.
Vibration, using a 128 Hz tuning fork on a distal bony prominence, moving proximally if it is not felt.
Proprioception, holding the sides of the terminal phalanx of the index finger and moving it up or down while the proximal phalanx is fixed.

Test the upper limb dermatomes in order: C5 over the lateral shoulder and upper arm, C6 the thumb, C7 the middle finger, C8 the little finger and T1 the medial forearm.

How do I test coordination?

Finger to nose, with your finger held at the limit of the patient's reach and moved between attempts, looking for past pointing and intention tremor.
Rapid alternating movements, pronating and supinating one hand onto the dorsum of the other, looking for dysdiadochokinesia.
Fine finger movements, asking the patient to play an imaginary piano.

Finish by saying you would examine the lower limbs, the cranial nerves and the neck, and take a full history.

What are the most common mistakes at this station?

Describing power as reduced instead of grading it on the MRC scale.
Getting MRC grade 2 wrong, which is movement with gravity eliminated.
Testing power without isolating the joint, so trick movements hide weakness.
Striking the biceps tendon directly rather than your own finger.
Stroking cotton wool along the skin, which tests a moving stimulus rather than light touch.
Finding a deficit and never saying whether the pattern is a root, a plexus or a peripheral nerve.

MRCS Part B Questions has an upper limb neurological examination station with a marked checklist at /Sample-Questions. Reviewed and updated 15 September 2026.

Key evidence

MRC muscle scale, from Aids to the Examination of the Peripheral Nervous System — Medical Research Council, UKRI
Deep Tendon Reflexes — Stanford Medicine 25
Candidate Instructions and Guidance Notes: MRCS Part B (OSCE), updated August 2021 — Intercollegiate Committee for Basic Surgical Examinations (2021)

FAQ

What is MRC grade 4, and why is it criticised?

Grade 4 is active movement against gravity and resistance, short of normal power. It is criticised because it covers an enormous range, from barely overcoming resistance to almost normal, which is why some clinicians subdivide it into 4 minus, 4 and 4 plus. The MRC scale itself has five grades above zero.

What does pronator drift indicate?

It indicates a pyramidal, upper motor neurone weakness on the drifting side. The supinators are weaker than the pronators in that pattern, so the forearm pronates and the arm drifts downwards when visual feedback is removed by closing the eyes. It is a sensitive screening test for subtle weakness.

Which reflex tests C6?

The supinator, also called the brachioradialis, reflex is usually attributed to C5 and C6, as is the biceps. Stanford Medicine 25 gives biceps and brachioradialis together as C5 and C6, with triceps at C7. If a station asks you to isolate C6, use the reflex together with power in elbow flexion and sensation over the thumb.

How do I tell a root lesion from a peripheral nerve lesion?

By the pattern. A root lesion follows a dermatome and a myotome, so sensory loss runs in a band and weakness affects all muscles sharing that root across different nerves. A peripheral nerve lesion affects the territory of that nerve only, so the sensory loss respects the nerve's cutaneous distribution and not a dermatome.

Do I need to test every dermatome?

Test one representative point per dermatome from C5 to T1 and compare sides, then go back and map more carefully only if you find an abnormality. Testing every point everywhere consumes the nine minutes and produces less information than a focused screen followed by targeted mapping.

The MRCS Part B Questions Team

Written and maintained by doctors who have sat and scored well at this interview, and reviewed against the current published guideline in each case. Guidance changes — check the source before you rely on a threshold.

Last reviewed 15 September 2026

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