• Ask the patient to lift their arms above their head.

• Ask them to ‘play the piano’. Check movements of the

fingers; asymmetric loss of fine finger movement may be a

very early sign of cortical or extrapyramidal disease.

• Observe the patient with their arms outstretched and

supinated (palms up) and their eyes closed for ‘pronator

drift’, when one arm starts to pronate.

7.8 Medical Research Council grading of muscle power

Grade Description

0 No muscle contraction visible

1 Flicker of contraction but no movement

2 Joint movement when effect of gravity eliminated

3 Movement against gravity but not against resistance

4a Movement against resistance but weaker than normal

5 Normal power

a

May be further classified as 4+ or 4−.

7.9 Nerve and muscle supplies of commonly tested movements

Movement Muscle Nerve and root

Shoulder abduction Deltoid Axillary C5

Elbow flexion Bicepsa Musculocutaneous C5a

/6

Brachioradialis (supinator reflex)a Radial C6a

Elbow extension Tricepsa Radial C7

Wrist extension Extensor carpi radialis longus Posterior interosseous C6

Finger extension Extensor digitorum communis Posterior interosseous C7

Finger flexion Flexor pollicis longus (thumb)

Flexor digitorum profundus (index and middle fingers)

Anterior interosseous C8

Flexor digitorum profundus (ring and little fingers) Ulnar C8

Finger abduction First dorsal interosseous Ulnar T1

Thumb abduction Abductor pollicis brevis Median T1

Hip flexion Iliopsoas Iliofemoral nerve L1/2

Hip extension Gluteus maximus Sciatic L5/S1

Knee flexion Hamstrings Sciatic S1

Knee extension Quadricepsa Femoral L3a

/4

Ankle dorsiflexion Tibialis anterior Deep peroneal L4/5

Ankle plantar flexion Gastrocnemius and soleusa Tibial S1a

/2

Great toe extension (dorsiflexion) Extensor hallucis longus Deep peroneal L5

Ankle eversion Peronei Superficial peroneal L5/S1

Ankle inversion Tibialis posterior Tibial nerve L4/5

a

Indicates nerve root innervation of commonly elicited deep tendon reflexes.

Rigidity is a sustained resistance throughout the range of

movement and is most easily detected when the limb is moved

slowly. In Parkinsonism this is classically described as ‘lead

pipe’ rigidity. In the presence of a Parkinsonian tremor there

may be a regular interruption to the movement, giving it a jerky

feel (‘cog wheeling’).

Clonus

Clonus is a rhythmic series of contractions evoked by a sudden

stretch of the muscle and tendon. Unsustained (<6 beats) clonus

may be physiological. When sustained, it indicates upper motor

neurone damage and is accompanied by spasticity. It is best

elicited at the ankle; knee (patella) clonus is rare and not routinely

tested.

Myotonia

Myotonia refers to the inability of muscles to relax normally and

characterises a group of neuromuscular disorders, the most

common of which is myotonic dystrophy. Patients may notice

difficulty in letting go of things with their hands, or a stiff gait.

Power

Strength varies with age, occupation and fitness. Grade muscle

power using the Medical Research Council (MRC) scale (Box

7.8). Record what patients can do in terms of daily activities;

for example, whether they can stand, walk and raise both arms

above their head. Lesions at different sites produce different

clinical patterns of weakness; examination will help discriminate

upper from lower motor neurone lesions.

Motor system • 139

7

weakness. This is helpful both diagnostically and therapeutically,

as you can show patients that their leg is not actually weak

using this sign.

Deep tendon reflexes

Anatomy

A tendon reflex is the involuntary contraction of a muscle in

response to stretch. It is mediated by a reflex arc consisting

of an afferent (sensory) and an efferent (motor) neurone with

one synapse between (a monosynaptic reflex). Muscle stretch

activates the muscle spindles, which send a burst of afferent

signals that lead to direct efferent impulses, causing muscle

contraction. These stretch reflex arcs are served by a particular

spinal cord segment that is modified by descending upper motor

neurones. The most important reflexes are the deep tendon

and plantar responses, whereas others, such as abdominal and

cremasteric reflexes, are rarely tested and of questionable value.

Dermatomal involvement may further help localise a lesion; for

example, pain going down one leg, with an absent ankle jerk

(S1) and sensory loss on the sole of the foot (S1 dermatome),

localises to the S1 root, most commonly due to a prolapsed

intervertebral disc (sciatica).

Examination sequence

• Ask the patient to lie supine on the examination couch

with the limbs exposed. They should be as relaxed and

comfortable as possible, as anxiety and pain can cause an

increased response.

• Extend your wrist and allow the weight of the tendon

hammer head to determine the strength of the blow. Strike

your finger that is palpating the biceps and supinator

tendons (otherwise it is painful for the patient), or the

tendon itself for the triceps, knee and ankle jerks.

• Record the response as:

• increased (+++)

• normal (++)

• decreased (+)

• present only with reinforcement (+/-)

• absent (0).

Principal (deep tendon) reflexes

• Ensure that both limbs are positioned identically with the

same amount of stretch. This is especially important for

the ankle reflex, where the ankle is passively dorsiflexed

before striking the tendon.

• Compare each reflex with the other side; check for

symmetry of response (Figs 7.19 and 7.20).

• Use reinforcement whenever a reflex appears to be absent.

For knee and ankle reflexes, ask the patient to interlock

their fingers and pull one hand against the other on

command (‘Have a tug of war with yourself’), immediately

before you strike the tendon (Jendrassik’s manœuvre).

• To reinforce upper limb reflexes, ask the patient to make a

fist with the contralateral hand.

Hoffmann’s reflex

• Place your right index finger under the distal

interphalangeal joint of the patient’s middle finger.

• Use your right thumb to flick the patient’s finger

downwards.

• Look for any reflex flexion of the patient’s thumb.

• Assess individual muscles depending on the history. Ask

the patient to undertake a movement. First assess whether