Wilkinson. Essential Neurology 2005

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Sensory ataxia

Since proprioception is such an important input to the cerebellum for normal movement, it is not surprising that loss of proprioception may cause ataxia, and that this ataxia may resemble cerebellar ataxia.

Pronounced loss of touch sensation, particularly in the hands and feet, seriously interferes with fine manipulative skills in the hands, and with standing and walking in the case of the feet.

In the presence of such sensory loss, the patient compensates by using his eyes to monitor movement of the hands or feet. This may be partially successful. An important clue that a patient’s impaired movement is due to sensory loss is that his clumsiness and unsteadiness are worse in the dark, or at other times when his eyes are closed, e.g. washing his face, having a shower, whilst putting clothes over his head in dressing.

Signs of sensory ataxia

In the hands

•Pseudoathetosis: the patient is unable to keep his fingers still in the outstretched position. Because of the lack of feedback on hand and finger position, curious postures develop in the outstretched fingers and hands when the eyes are closed.

•Clumsiness of finger movement, e.g. when turning over the pages of a book singly, and when manipulating small objects in the hands, made much worse by eye closure. Shirt and pyjama top buttons, which cannot be seen, present more difficulty than other buttons.

•Difficulty in recognizing objects placed in the hands when the patient’s eyes are closed, and difficulty in selecting familiar articles from pockets and handbags without the use of the eyes.

•Loss of touch and joint position sense in the fingers.

In the legs

•Marked and unequivocal Rombergism. The patient immediately becomes hopelessly unsteady in the standing position when the eyes are closed.

•As the patient walks, he is obviously looking at the ground and at his feet.

•Loss of touch and joint position sense in the feet and toes.

CHAPTER 5

CASE HISTORIES

Case 1

A 75-year-old woman notices that she can no longer deal the cards at her bridge club because her hands have become clumsy and slow. Her handwriting has become spidery and small. She cannot roll over in bed. She shuffles when she walks.

She lives with her husband who is in good health. She has never smoked. Her parents both lived into their eighties without anything similar, and her sister is alive and well. She is on medication for hypertension and a hiatus hernia.

On examination she walks with a flexed posture,a shuffling gait and no arm swing. She has moderate bradykinesia and rigidity in both arms.There is no tremor or cerebellar deficit. Her eye movements are normal for her age. Her pulse and blood pressure are normal.

a.What part of the history would you most like to clarify?

Case 2

A 16-year-old boy comes to see you about his balance. He has avoided running and football for 2 years

because of a slowly increasing tendency to fall, but now he topples over if he is jostled in the corridor and has to stay close to the wall for support. His speech is a little slurred, especially when he is tired. He has no headaches or weakness.

He has no past medical history or family history of similar problems. He is the oldest of four children. He does not consume alcohol or drugs.

On examination he walks on a broad base, lurching from side to side. He cannot walk heel to toe or stand with his feet together. He has mild finger–nose and heel–knee–shin ataxia and performs alternating movements slowly and awkwardly. His speech is slurred.There is no nystagmus. Both optic discs are pale.All of his reflexes are absent. His plantar responses are extensor. He cannot feel the vibration of a tuning fork in his feet.

a.Where in the nervous system does the problem lie?

b.What do you think is the cause of his problems?

c.What are the issues for his parents?

(For answers, see pp. 257–8.)

C1

C1

C2

C3

C4

C5

C6

C7

C8

T1

T1

T2

T3

T4

T5

T6

T7

T8

T9

T10

T11

T12

L1

L1

L2

L3

L4

L5

Sacrum

S1

S2

S3

S4

S5

Co

Coccyx

Anatomical considerations

Figure 6.1 shows the relationship of the spinal cord, dura, spinal nerves and vertebrae to each other. The important points to note are:

•the spinal cord terminates at the level of the L1 vertebra. Any disease process below the level of this vertebra may cause neurological problems, but it will do so by interfering with function in the cauda equina not in the spinal cord;

•because the vertebral column is so much longer than the spinal cord, there is a progressive slip in the numerical value of the vertebra with the numerical value of the spinal cord at that level, e.g.

•C7 vertebra corresponds to T1 cord

•T10 vertebra corresponds to T12 cord

•L1 vertebra corresponds to S1 cord;

•the dural lining of the bony spinal canal runs right down to the sacrum, housing the cauda equina below the level of the spinal cord at L1;

•the vertebrae become progressively more massive because of the increasing weight-bearing load put upon them;

•any lesion of the spine in the cervical and thoracic region, as far down as the 10th thoracic vertebra, may result in upper motor neurone signs in the legs;

•lesions in the lumbosacral spine may result in lower motor neurone signs in the legs.

Fig. 6.1 Diagram to show the relationship of the spinal cord, dura and spinal nerves to the vertebrae. Co, coccygeal.

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Clinical considerations

The clinical picture of a patient presenting with a lesion in the spinal cord is a composite of tract signs and segmental signs, as shown in Fig. 6.4.

Tract signs

A complete lesion, affecting all parts of the cord at one level (Fig. 6.5), will give rise to:

•bilateral upper motor neurone paralysis of the part of the body below the level of the lesion;

•bilateral loss of all modalities of sensation below the level of the lesion;

•complete loss of all bladder, bowel and sexual function.

It is more frequent for lesions to be incomplete, however, and

this may be in two ways.

1.The lesion may be affecting all parts of the spinal cord at one level (Fig. 6.5a), but not completely stopping all function in the descending and ascending tracts. In this case there is:

•bilateral weakness, but not complete paralysis, below the level of the lesion;

•impaired sensory function, but not complete loss;

•defective bladder, bowel and sexual function, rather than complete lack of function.

2.At the level of the lesion, function in one part of the cord may be more affected than elsewhere, for instance:

•just one side of the spinal cord may be affected at the site of the lesion (Fig. 6.5b), the so-called Brown-Séqard syndrome;

•the lesion may be interfering with function in the posterior columns, with little effect on other parts of the cord (Fig. 6.5c);

•the anterior and lateral parts of the cord may be damaged,

with relative sparing of posterior column function (Fig. 6.5d).

The level of the lesion in the spinal cord may be deduced by finding the upper limit of the physical signs due to tract malfunction when examining the patient. For instance, in a patient with clear upper motor neurone signs in the legs, the presence of upper motor neurone signs in the arms is good evidence that the lesion is above C5. If the arms and hands are completely normal on examination, a spinal cord lesion below T1 is more likely.

CHAPTER 6

Tract symptoms and signs

Segmental symptoms and signs

Lesion

Tract symptoms and signs

Fig. 6.4 Diagram to show that the clinical phenomena generated by a spinal cord lesion are a composite of tract and segmental features.

Right

Complete spinal cord lesion

No downward or upward transmission of impulses

Right

Posterior column spinal cord lesion

No neurotransmission in either posterior column \ position and vibration sense loss in both legs

Bladder probably intact

Left

Right-sided spinal cord lesion

No neurotransmission in :

Right pyramidal tract \ UMN signs right leg

Right posterior column \ position and vibration sense loss right leg

Right spinothalamic tract

Left \

pain and temperature sense loss left leg

Effect upon bladder variable, probably just intact

Anterolateral column spinal cord lesion

No neurotransmission in :

Either pyramidal tracts \ UMN signs both legs

Either spinothalamic tracts \ pain and temperature sense loss both legs

Tracts to bladder, bowel etc. \ incontinence, retention, constipation

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Segmental signs

In addition to interfering with function in the ascending and descending tracts, a spinal cord lesion may disturb sensory input, reflex activity and lower motor neurone outflow at the level of the lesion. These segmental features may be unilateral or bilateral, depending on the nature of the causative pathology. Chief amongst the segmental symptoms and signs are:

•pain in the spine at the level of the lesion (caused by the pathological causative process);

•pain, paraesthesiae or sensory loss in the relevant dermatome (caused by involvement of the dorsal nerve root, or dorsal horn, in the lesion);

•lower motor neurone signs in the relevant myotome (caused by involvement of the ventral nerve root, or ventral horn, in the lesion);

•loss of deep tendon reflexes, if reflex arcs which can be assessed clinically are present at the relevant level. (A lesion at C5/6 may show itself in this way by loss of the biceps or supinator jerks. A lesion at C2/3 will not cause loss of deep tendon reflexes on clinical examination.)

A common example of the value of segmental symptoms and signs in assessing the level of a spinal cord lesion is shown in Fig. 6.6.

Knowledge of all dermatomes, myotomes and reflex arc segmental values is not essential to practise clinical neurology, but some are vital. The essential requirements are shown in Fig. 6.7.

Before proceeding to consider the causes of paraplegia in the next section, two further, rather obvious, points should be noted.

•Paraplegia is more common than tetraplegia. This is simply a reflection of the fact that there is a much greater length of spinal cord, vulnerable to various diseases, involved in leg innervation than in arm innervation, as shown in Fig. 6.1.

•At the beginning of this section, and in Fig. 6.4, it was stated that patients with spinal cord lesions present with a composite picture of tract and segmental signs. This is the truth, but not the whole truth. It would be more accurate to say that such patients present with the features of their spinal cord lesion (tract and segmental), and with the features of the cause of their spinal cord lesion. At the same time as we are assessing the site and severity of the spinal cord lesion in a patient, we should be looking for clinical clues of the cause of the lesion.

CHAPTER 6