LO: Surface Anatomy & Examination of the Nerves of the Upper Limb

Understand the concepts and associated principles, functional and clinical anatomy underlying the physical examination of the peripheral nerves of the upper limb (syllabus and ICARS lecture notes).

General Inspection

1. Look for an abnormal posture (such as hemiplegia from a stroke)2. Look for muscle wasting

Muscle wasting could indicated a denervated muscle, a primary muscle disease or disuse atrophy

Compare one side with the other for wasting and try to work out which muscle groups are involved (flexor/extensor, unilateral/bilateral, proximal/distal)

3. Look for any abnormal movements (such as a tremor of the wrist or arm) Inspect the skin Look for evidence of neurofibromatosis (a genetic disease where nerve tissue grows

tumours), cutaneous angiomata or herpes zoster Scars from old injuries/surgical treatment Has this person got a urinary catheter?

The Motor System (General)

Introduce yourself and shake the patient’s hand A patient who cannot let go of your hand after shaking it has myotonia (an inability to

relax the muscles after voluntary contraction). The most common cause of this state is dystrophia myotonia (a genetic, multisystemic disease)

Ask the patient to appropriate undress so that the shoulder girdles are shown Sit the patient over the edge of the bed and ask them to hold their arms out in front, palms

facing the floor and eyes closed. Watch for evidence of drifting (movement of one or both of the arms) The causes of a drift are any of the following;

o Upper motor neurone (pyramidal) weakness. The drift will be due to muscle weakness and tends to be in a downward movement. The drift will typically start distally with the fingers and spreads proximally. There may also be a slow pronation of the wrist and flexion of the fingers and elbow.

o Cerebellum disease. This drift is usually upwards and also includes a slow pronation of the wrist and elbow.

o Loss of proprioception. This is usually a searching movements and usually only affects the fingers. This is due to a loss of point position sense and can be in any direction

Whilst the patient is in this position, also ask them to try to keep their arms in the same position, whilst the examiner tries to knock their arms out of position.

Ask the patient to relax and inspect the large muscles of the upper arms for fasciculations (irregular contractions of small areas of muscle which have no rhythmical pattern). They may be course or fine, present at rest, but not during active movement. Causes of fasciculations;

o Motor neurone disease (if the fasciculations are present with weakness or wasting, there may be degeneration of the lower motor neurone)

o Motor root compressiono Peripheral neuropathy (eg. diabetes)o Primar myopathyo Thyrotoxicosis

Fasciculations are usually benign unless associated with other signs of a motor lesion

Test Tone

Tone is tested at both the wrists and the elbows

Rotate the wrists with supination and pronation of the elbow joints passively. Patient should be told to relax, and the examiner should support the elbow with one hand and hold the patient’s hand with the other.

If the patient resists the passive movements, the joints should be moved unpredictably and at different rates. When the arm is raised by the examiner and dropped, it will fall suddenly if tone is reduced. (Hypotonia is a difficult sign to elicit and not all that helpful in assessment of the lower motor neurone lesion.

Cogwheel rigidity of Parkinson’s should assessed by having the patient move one arm up and down, whilst the examiner moves the hand and forearm of the other arm, testing tone at the wrist and elbow.

Test for myotonia. In these patients, tone is usually normal at rest, but after active or sudden movements, there may be a great increase in tone and the patient is unable to relax the muscle. It may be elicited by tapping over the body of a myotonic muscle, causing a dimple of contraction that is slow to disappear. The best test for this is tapping over the thenar eminence or by asking the patient to make a tight fist and then open the hand quickly (the opening of the fist will be very slow in a patient who has myotonic muscles).

Power

Power is assessed on the following scale;

0 Complete paralysis 1 Flicker of contraction possible2 Movement is possible when gravity is excluded3 Movement is possible against gravity but not if any further resistance is added4- Slight movement against resistance4 Moderate movement against resistance4+ Submaximal movement against resistance5 Normal power

If power is reduced, work out if it is symmetrical or asymmetrical, if it is involving only particular muscle groups, if it is proximal, distal or general.

(need to assess if any painful joint or muscle disease may be interfering with the assessment)

Asymmetrical muscle weakness is most often the result of peripheral nerve, brachial plexus or root lesion, or an upper motor neurone lesion.

Shoulder:Firstly, the patient should be asked to shrug their shoulders.Movement Muscles Spinal Cord Segment DescriptionAbduction Mostly deltoid and

supraspinatusC5, C6 Arms should be

abducted with elbows flexed and try to resist examiner’s efforts to push the arms down

Adduction Mostly pec major and Lat dorsi

C6, C7, C8 Adduct with elbows flexed, resisting examiners attempts to separate them

Elbow:Movement Muscles Spinal Cord Segment DescriptionFlexion Biceps and brachialis C5, C6 Patient should bend

the elbow and resist the examiners attempts to straighten it

Extension Triceps brachii C7, C8 Patient should try to straighten the elbow whilst the examiner attempts to bend it

Wrist:Movement Muscles Spinal Cord Segment DescriptionFlexion Flexor carpi ulnaris and

radialisC6, C7 Patient should bend

the wrist and not allow the examiner to straighten it

Extension Extensor carpi group C7, C8 The patient should extend the wrist and not allow the examiner to bend it

Fingers:Movement Muscles Spinal Cord Segment DescriptionExtension Extensor digitorum

communis, extensor indicis and extensor digiti minimi

C7, C8 Patient should straighten fingers and stop the examiner from trying to bend them

Flexion Flexor digitorum C7, C8 Patient squeezes the

profundus and sublimis examiners fingersAbduction Dorsal interossei C8, T1 Patient should spread

the fingers and resist examiners attempts to push them together

Adduction Volar interossei C8, T1 Patient holds their fingers together and resists the examiners attempts to separate them

Special Tests: A radial nerve injury will result in a wrist drop and therefore, this should be noted all

through the examination and does not require a special test To test the median nerve, two tests should be performed;

o The pen touching test – ask the patient to lay the hand flat, palm upwards and attempt to abduct the thumb vertically to touch the examiner’s pen above it

o Ochsner’s clasping test – ask the patient to clasp the hands firmly together – the index finger on the affected side will fail to flex with a lesion in the cubital fossa or higher

The ulnar nerve can be tested with the paper grip test to try to elicit the froman’s sign. Ask the patient to grasp a piece of paper between the thumb and the lateral aspect of the forefinger of each hand. The affected thumb will flex because of loss of the adductor of the thumb

Reflexes

A reflex is usually mediated via a neural pathway synapsing in the spinal cord. It is subject to regulation from the brain

Reflexes are graded from absent to greatly increased;0 = absent+ = present but reduced++ = normal+++ = increased, possibly normal++++ = greatly increased, possibly associated with clonus (involuntary muscle contractions)

Biceps jerk (C5, C6)

Place one finger on the biceps tendon and tap it with the tendon hammer If the reflex appears to be absent, test following a reinforcement manoeuvre, eg. ask the

patient to clench their teeth tightly just before the hammer falls. An increased jerk occurs with an upper motor neurone lesion. A decreased or absent reflex occurs with a breach in any part of the reflex motor arc – the

muscle, the motor nerve, the anterior spinal cord root, the anterior horn cell or the sensory arc.

Triceps jerk (C7, C8)

Support elbow and tap over the triceps tendon

Brachioradialis (supinators) jerk (C5, C6)

Examiner placed their first 2 fingers over the radius, just above the wrist and the strikes their own fingers with the tendon hammer.

Normally, contraction of the brachioradialis causes flexion at the elbow. If elbow extension and finger flexion is the response when the wrist is tapped, it is said to be

the inverted brachioradialis (supinators) jerk. The triceps contraction causes elbow extension instead of the usual elbow flexion. This would also be associated with an absent biceps jerk and an exaggerated triceps jerk. This indicates a spinal cord lesion at the C5 or C6 level and occurs because a lower motor neurone lesion at C5 or C6 is combined with an upper motor neurone lesion affecting the reflexes below this level.

Finger jerks (C8)

Patient rests hand with palm upwards and the fingers slightly flexed. The examiner places their fingers over the patients and the tendon hammer is struck over the examiner’s fingers. Slight flexion of the patient’s fingers should occur.

Coordination (testing the cerebellum)

Always demonstrate these tests for the patient’s benefit.

1. Finger-nose test

Ask the patient to touch their index finger to their nose and then turn the finger around and touch the examiner’s outstretched forefinger at nearly full extension of the shoulder and elbow.

This test should be done both fast and slow, with the patient’s eyes open and closed.

Slight resistance to the patient’s movements by the examiner pushing on his or her forearm during the test may unmask less severe abnormalities.

Look for;

Intention tremor (tremor increasing as the target is approached) Past-pointing (finger overshoots the target towards the side of the cerebella

abnormality)

2. Rapidly alternating movements

Ask the patient to pronate and supinate his or her hand on the dorsum of the other hand as rapidly as possible. This movement is slow and clumsy in cerebella disease (and is called dysdiadochokinesis), and may also be affected in extrapyramidal disorders (such as Parkinson’s) and in pyramidal disorders (such as an internal capsule infarction).

3. Rebound

Ask the patient to lift their arms rapidly from their side and then stop. Hypotonia due to cerebella disease causes a delay in the stopping of the arms.

Sensory Testing

Spinothalamic pathway (pain and temperature)

Theory: Pain and temperature fibres enter the spinal cord and cross a few segments higher to the opposite spinothalamic tract, which then ascends to the brainstem.

Pain (pinprick) testing

Firstly show the patient the sensation of the pinprick on the anterior chest wall. Ask the patient to tell you if it feels sharp or dull when you touch areas of their upper limb. Start proximally on the upper arm and test in each dermatome Also compare left and right of the same dermatome Map out any area of dullness

Temperature Testing (not usually necessary)

This can be done by using test tubes filled with differing temperatures of water and using the same method as above

Absence of the ability to feel heat is almost always associated with the inability to feel cold

Posterior columns (vibration and proprioception)

Theory: these fibres enter and ascend ipsilaterally in the posterior columns of the spinal cord to the nucleus gracilis and nucleaus cuneatus in the medulla, where they cross.

Vibration testing

Ask the patient to close their eyes and using a tuning fork, place the vibrating fork on one of the distal interphalangeal joints

The patient should be able to tell the examiner that there is a vibration When the examiner deadens the vibration, the patent should be able to say exactly when

this occurs Compare one side with the other If the vibration sense is reduced or absent, test over the ulnar head at the wrist, and then

the elbows and then the shoulders to determine the level of abnormality

Proprioception testing

Use the distal interphalangeal joint of the patient’s little finger. When the patient has their eyes open, grasp the distal phalanx from the sides and move it up and down to demonstrate these positions. Then ask the patient to close their eyes and perform these manoeuvres randomly. Ask the patient to tell you which direction you are moving the finger in

If there is an abnormality, test the wrists and elbows similarly Sense of position is lost before a sense of movement and the little finger is affected before

the thumb

Light touch testing

Theory: some fibres travel in the posterior columns (ipsilaterally) and the rest cross the middle line to travel in the anterior spinothalamic tract (contralaterally). For this reason, light touch is not very discriminating.

Ask the patient to close their eyes, and using a cotton wool on each of the dermatomes, ask the patient to tell you when they feel the light touch. Compare each dermatome.

Graphaesthesia

Ask patient to close their eyes and then draw a number on their palm and tell you what you have drawn.

Stereognosis

Ask the patient to close their eyes and then hand them a familiar object (such as a pen). They will need to distinguish size, texture and the identity of the familiar object in their hand.

Interpretation of sensory abnormalities

Try to determine if there is injury to a dermatome (spinal cord or nerve root lesion), a single peripheral nerve, a peripheral neuropathy (glove distribution) or a hemisensory loss (due to spinal cord or upper brainstem or thalamic lesion).

Dermatomes of the Upper Limb

Nerves of the upper limb

Musculocutaneous Nerve

Motor: arm flexors Sensory: lateral cutaneous nerve of the forearm

The picture below shows the approximate area within which sensory changes may be found in lesions of the musculocutaneous nerve. The continuous line corresponds to light touch, whilst the dotted line corresponds to pin-prick (pain).

Axillary Nerve

Motor: deltoid muscle Sensory: upper lateral cutaneous nerve of the arm

On the picture below, the light touch will correspond to the continuous, solid line and the pin-prick (pain will correspond to the dotted line).

Radial Nerve

Motor: arm/forearm extensors Sensory: posterior cutaneous nerve of the arm, lower lateral cutaneous nerve of the arm

and posterior cutaneous nerve of the forearm

Proximal Radial Nerve Lesion

The continuous line corresponds to light touch and the dotted line corresponds to pin-prick (pain).

Distal radial nerve lesion

Median Nerve

Motor: forearm/ finger flexes Sensory: palmar cutaneous branch to palm of the hand (centre and

radial side), digital branches to palmer surfaces of fingers (radial three and a half digits), tips and dorsal surfaces over distal one and a half phalanges.

Median nerve lesion

Ulnar Nerve

Motor: forearm/finger flexors (medial) Sensory: superficial cutaneous branch to the palm of

the hand (ulnar side), digital branches to palmar surfaces of fingers, tips and dorsal surfaces over distal one and a half phalanges (ulnar one and a half digits), dorsal branch to dorsal surface of hand ulnar side (ulnar one and a half digits)

Proximal Ulnar Nerve Lesion

Distal Ulnar Nerve Lesion

Medial Cutaneous Nerve of the Forearm