chapter 3

Neurological Examination of the Limbs

Learning how to perform a neurological examination requires repeated practice. Practice without an understanding of how to examine the various aspects of the nervous system and how to interpret the findings is akin to practising golf without having had lessons – useless. This chapter describes how to examine the limbs and interpret the findings. As it is very difficult to learn examination technique from a textbook, a video of the technique is included on the accompanying DVD.

Apart from a few pathognomonic signs that distinguish one disease from another, for example the tremor, rigidity and bradykinesia implicating Parkinson’s disease with involvement of the substantia nigra or basal ganglia, in most instances the neurological examination does not establish the aetiology or cause of the problem. It simply localises the part of the nervous system affected by the pathological process.

The principal purpose of the examination is to determine whether the patient has lower motor neuron (LMN) signs or, more specifically, signs that indicate involvement of the peripheral nervous system (anterior horn cells, nerve roots, brachial or lumbosacral plexus, peripheral nerve, neuromuscular junction or muscle) or upper motor neuron (UMN) signs that indicate involvement of the central nervous system (brain, cerebellum and spinal cord). These were briefly discussed in Chapter 2, ‘The neurological history’, and, because they are absolutely crucial, they will be discussed in more detail in this chapter (see Table 3.1).

TABLE 3.1

The neurological findings in upper versus lower motor neuron lesions

	Upper motor neuron lesion	Lower motor neuron lesion
Wasting	Usually no wasting but there may be mild wasting with long standing problems	No wasting in the very early stages but usually associated with significant wasting
Power	Weakness of extensor muscles in the arms^∗ and flexor muscles in the legs^∗∗	The pattern of weakness reflects that part of the LMN that is affected
Tone	Increased +/– clonus	Decreased
Reflexes	Increased	Decreased or absent
Plantars	Up-going (extensor)	Down-going
Sensory findings	Sensory level	Focal sensory loss reflecting involvement of a nerve root, plexus or peripheral nerve

^∗Shoulder abduction, elbow extension, wrist and finger extension in the arms.

^∗∗Hip flexion, knee flexion and foot dorsiflexion in the legs. The tone may not be increased and the reflexes can be absent in acute spinal cord lesions referred to as spinal shock. Clonus is a series of involuntary repetitive movements of the ankle, up and down, induced by suddenly pushing the foot upwards while the leg is extended [1]. The test is less painful if it is performed with the knee slightly flexed.

Although there are many ways to examine a patient, the following method is used by many neurologists and is the one recommended by this author.

THE MOTOR EXAMINATION

The examination of the motor system involves:

• inspecting for wasting and fasciculations in the muscles

• looking for changes in tone and reflexes

• testing strength

• checking the plantar responses.

The examination should start with inspection for wasting and fasciculations. This author then examines the tone, followed by strength, then the reflexes and the plantar responses. The exact order is not important.

Many examiners will perform a screening test of the upper limbs by observing patients elevating their arms and holding them horizontally straight out in front, initially with their eyes open and then subsequently closed (see Figure 3.1). The palms can be turned either down or up – it does not matter – although occasionally having

FIGURE 3.1 Screening test of the upper limbs with hands outstretched: A with palms up; B with palms down

• The pathology is always at the level of the LMN signs and at or above the uppermost limit of the UMN signs.

• In most instances the neurological examination does not establish the aetiology or cause of the problem. It simply localises the part of the nervous system that is affected by the pathological process.

• If the history has been obtained using the method described in Chapter 2, ‘The neurological history’, the nature and distribution of the symptoms should provide an idea as to whether there will be upper or lower motor neuron signs.

the palms turned upwards seems a more sensitive technique.¹

The arm(s) will:

If the signs are different, the diagnosis suspected from the history should be reviewed and the whole process should be repeated to confirm both the history and findings. This is far more rewarding than ordering a multitude of purposeless investigations.

• drift downwards if there is weakness

• drift upwards and often outwards if there is a proprioceptive or parietal lobe problem

• oscillate up and down with a cerebellar disturbance if the patient is asked to elevate the limbs briskly, which can be missed if the movement is too slow.

Inspection for wasting and fasciculations

The muscles of the upper arm, forearm, hand, thigh, anterior tibial compartment and calves are examined for wasting and/or fasciculations. Fasciculations are visible spontaneous contractions or twitching of muscle fibres that are innervated by a single motor unit [1]. It may be necessary to spend several minutes carefully examining the muscles in order to detect fasciculations. It is easy to be certain that wasting is present when it is very severe, but with milder degrees of wasting one is less certain that there is a lesion involving the peripheral (LMN) nervous system. Some patients are very thin, and inexperienced clinicians may incorrectly suspect wasting when examining the small muscles of the hands, particularly in older patients. If the wasting affects one arm or one leg a comparison can be made with the contralateral limb. The muscles, if wasted, will initially lose their rounded appearance and appear flattened.

The reliable signs of muscle wasting are (Figure 3.2):

FIGURE 3.2 The first dorsal interosseous muscle: A no wasting; B wasting

• loss of the visible bulge that occurs when the thumb is adducted towards the index finger – the first dorsal interosseous muscle

• prominence of the anterior border of the tibia – tibialis anterior muscle

• prominence of the spine of the scapula – supraspinatus and infraspinatus muscles

• scalloped appearance just above the patella as if a bite has been taken out of the muscle – quadriceps.

Looking for changes in tone

There are two different ways to test for tone, depending on whether the problem is affecting the motor system or the extrapyramidal system (the latter is discussed in Chapter 13, ‘Abnormal movements and difficulty walking due to central nervous system problems’).

Tone is tested using quick movements when the motor system is being assessed.

TESTING FOR INCREASED TONE RELATED TO AN UPPER MOTOR NEURON PROBLEM

It is important to first check with the patient whether a quick movement of the arm or leg would cause pain.

• Arms. Tone is tested with the forearm semi-pronated and the elbow flexed at 90° (refer to Figure 3.3A). The examiner holds the elbow with one hand and then places the other hand in the hand of the patient as if they were shaking hands. The test is performed with a quick supination of the forearm. If there is increased tone there will be a discernible catch. Very occasionally, when the tone is markedly increased, repetitive contractions may occur, and this is referred to as clonus.

FIGURE 3.3 How to test tone in the upper limbs: A motor system; B extrapyramidal system

• Legs. Tone is tested with the leg lying flat on the bed and slightly externally rotated and with the knee flexed very slightly. The examiner places their hands behind the leg just above the knee and attempts to quickly elevate the leg. If there is increased tone, the heel will lift up off the bed. The leg may lift off the bed in patients who are very anxious and who find it difficult to relax – slight external rotation of the leg prior to the quick movement helps in this situation and eliminates the false impression of increased tone in anxious patients. The other test for increased tone in the legs is ankle clonus, where the leg is slightly flexed at the knee with the ankle plantar-flexed. The examiner places their left hand behind the knee and grasps the foot with their right hand and forcibly dorsiflexes the foot. Repetitive contractions while the examiner holds the foot in dorsiflexion is a sign of increased tone, referred to as ankle clonus.

TESTING FOR INCREASED TONE RELATED TO AN EXTRAPYRAMIDAL PROBLEM

To test the upper limbs (Figure 3.3B), the forearm and hand are pronated and the examiner holds the middle of the forearm with one hand and holds the hand of the patient in a monkey grip. The patient’s hand is compressed into the wrist as the wrist is slowly flexed and extended. This technique will elicit the classical cog-wheel rigidity seen with extrapyramidal problems.

To test the lower limbs, the leg is flexed at the knee and the examiner holds the leg behind the knee. Using the other hand the examiner grasps the foot and slowly dorsiflexes and plantar-flexes the ankle, looking for the cog-wheel rigidity. The two techniques for testing tone are demonstrated on the DVD.

Testing muscle strength

Use simple language that the patient can understand. The extent of muscle testing can be varied, depending on whether the history suggests an UMN problem or a LMN problem. In patients with involvement of the central nervous system or corticospinal tract, specific patterns of weakness occur and these are discussed below. In patients with focal weakness with or without focal sensory loss, suggesting a LMN problem, it is important to examine strength by commencing in that part of the limb that the patient describes as weak. The examiner then tests every single muscle of the affected limb to establish the pattern of weakness and, from this, the anatomical basis for the weakness and the site of the pathology within the peripheral nervous system can be determined.

The following technique is recommended when examining muscle strength. The muscle/muscle group, nerve related to that muscle/muscle group, the nerve root(s) and the action of the muscle [2] are listed in each section below. Experienced neurologists have memorised the neuroanatomy; inexperienced clinicians can record the pattern of weakness and consult a textbook of neuroanatomy, the illustrations in Chapter 1, ‘Clinically oriented neuroanatomy’, or this chapter.

UPPER LIMBS

Muscles around the shoulder:

To test the supraspinatus (Figure 3.4) the elbow should be abducted from the side of the body to approximately 30°, the examiner places a hand over the elbow and pushes the elbow towards the trunk while the patient tries to resist.

FIGURE 3.4 Testing of the A supraspinatus and B deltoid muscles (abduction of the shoulder)

To test the deltoid muscle (Figure 3.4) the elbow should be abducted from the side to 90°, the examiner places a hand over the upper arm just above the elbow and pushes downwards while the patient attempts to resist.

The elbow is kept by the side, the forearm is flexed at 90° and the hand is semi-pronated (Figure 3.5). The examiner places a hand over the middle of the back of the forearm and attempts to internally rotate the forearm towards the body as the patient resists.

FIGURE 3.5 Testing of the infraspinatus (external rotation of the shoulder)

The elbow is kept by the side, the forearm is flexed at 90° and the hand is semi-pronated (Figure 3.6). The examiner places a hand on the middle of the forearm and attempts to prevent internal rotation of the forearm.

FIGURE 3.6 Testing of the subscapularis (internal rotation of the shoulder)

There is a rare entity of winging of the scapular that is the result of damage to the nerve to the serratus anterior (see Chapter 11, ‘Common neck, arm and upper back problems’). The patient is instructed to stand in front of a wall, with the elbows slightly flexed and the palms on the wall (Figure 3.7). They are then instructed to push as hard as they can and the scapular should not lift off the chest wall. If it does the muscle is weak, resulting in ‘winging of the scapula’.

FIGURE 3.7 Testing of the serratus anterior

Muscles around the elbow:

The elbow is bent at 90° with the palm pointing towards the ceiling (Figure 3.8). The examiner grasps the elbow with the left hand and the wrist with the right hand and attempts to prevent further flexion of the elbow.

FIGURE 3.8 Testing elbow flexion with the forearm supinated

The elbow is flexed at 90° with the forearm semi-pronated (Figure 3.9). The examiner places the left hand under the elbow and the right hand on the wrist and attempts to prevent further flexion of the elbow.

FIGURE 3.9 Testing elbow flexion with the forearm semi-pronated

It is very important that the elbow is only slightly flexed (as little as 20–30° from the fully extended position) when testing extension (Figure 3.10). If the elbow is fully flexed, this will result in an apparent weakness of the triceps when it is strong and, if it is fully extended, subtle degrees of weakness may be missed. The examiner places the left hand over the anterior aspect of the elbow and the right hand over the dorsal aspect of the wrist and attempts to prevent the patient from straightening their elbow.