Wilkinson. Essential Neurology 2005

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Investigation

Brain imaging

Brain tumours can be detected using CT X-ray scanning or MR scanning. The choice of technique used will often depend upon local facilities. CT is cheaper, more widely available and (when used with contrast enhancement) capable of detecting the majority of tumours. MR scanning is superior in many ways, especially in detecting small tumours and tumours in the base of the skull and the posterior fossa. MR also allows the images to be presented in a range of planes, which helps with surgical planning.

Admission to hospital

If the clinical presentation and results of scanning suggest a brain tumour, admission to hospital for further investigation will be indicated in most cases, especially if there is progressive neurological deficit or evidence of raised intracranial pressure. This will be an extremely stressful experience for the patient and relatives. Reassurance, sympathy and encouragement together with adequate explanation are required.

Other tests

The brain imaging procedures mentioned above sometimes require the support of:

•radiological and other imaging techniques elsewhere in the body if metastatic disease seems likely;

•carotid or vertebral angiography if the neurosurgical team needs this information prior to surgery;

•haematological and biochemical investigation if cerebral abscess, granuloma, metastatic disease or pituitary pathology are under consideration.

(NB Lumbar puncture is contra-indicated in suspected cases of cerebral tumour.)

CHAPTER 3

BRAIN TUMOUR

Management of brain tumours

•Admission to hospital

•Scanning

•No lumbar puncture

•Dexamethasone

•Surgery

•Radiotherapy

•Anticonvulsants

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Management

If the patient shows marked features of raised intracranial pressure and scanning displays considerable cerebral oedema, dexamethasone may be used with significant benefit. The patient will be relieved of unpleasant, and sometimes dangerous, symptoms and signs, and the intracranial state made much safer if neurosurgical intervention is to be undertaken.

Surgical management

Complete removal

Meningiomas, pituitary tumours not susceptible to medical treatment, acoustic neuromas and some solitary metastases in accessible regions of the brain can all be removed completely. Sometimes, the neurosurgical operation required is long and difficult if the benign tumour is relatively inaccessible.

Partial removal

Gliomas in the frontal, occipital and temporal poles may be removed by fairly radical debulking operations. Sometimes, benign tumours cannot be removed in their entirety because of tumour position or patient frailty.

Biopsy

If at all possible, the histological nature of any mass lesion in the brain should be established. What looks like a glioma or metastasis from the clinical and radiological points of view occasionally turns out to be an abscess, a benign tumour or a granuloma. If the mass lesion is not in a part of the brain where partial removal can be attempted, biopsy by means of a needle through a burrhole usually establishes the histological diagnosis. The accuracy and safety of this procedure may be increased by use of stereotactic surgical techniques. Histological confirmation may not be mandatory where there is strong collateral evidence of metastatic disease.

Histological confirmation may be postponed in patients presenting with epilepsy only, in whom a rather small mass lesion in an inaccessible part of the brain is revealed by a scan. Sequential scanning, initially at short intervals, may be the most reasonable management plan in such patients.

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Shunting and endoscopic surgery

Midline tumours causing ventricular dilatation are routinely treated by the insertion of a shunt into the dilated ventricular system. The shunt tubing is tunnelled under the skin to drain into the peritoneal cavity. This returns intracranial pressure to normal, and may completely relieve the patient’s symptoms. Sometimes it is possible and desirable to remove the tumour or treat the hydrocephalus using intracranial endoscopic procedures instead.

Additional forms of treatment

Radiotherapy

Middle-grade gliomas, metastases and incompletely removed pituitary adenomas are the common intracranial tumours which are radiosensitive. The posterior fossa malignant tumours of childhood and lymphoma are also sensitive to radiotherapy. Radiotherapy commonly follows partial removal or biopsy of such lesions, and continues over a few weeks whilst the preoperative dose of dexamethasone is being gradually reduced.

Chemotherapy

Chemotherapy can be useful as primary treatment for lymphoma and as adjunctive therapy for oligodendroglioma and some high-grade astrocytomas.

Anticonvulsants

Control of epilepsy may be an important part of the management of a patient with a supratentorial brain tumour.

Dexamethasone

Taken in large and constant dosage, dexamethasone may be the most humane treatment of patients with highly malignant gliomas or metastatic disease. Used in this way, dexamethasone often allows significant symptomatic relief so that the patient can return home and enjoy a short period of dignified existence before the tumour once more shows its presence. At this point, dexamethasone can be withdrawn and opiates used as required.

CHAPTER 3

CASE HISTORIES

Case 1

A 65-year-old widow presents with a 6-month history of unsteadiness. She has started to veer to the left. She has been well prior to this, apart from a longstanding hearing problem and surgery for colon cancer 5 years ago. On examination she has an ataxic gait, slight leftwards nystagmus, an absent left corneal reflex and marked left-sided deafness.There is no papilloedema.

a. What do you think is the cause of her symptoms?

Case 2

A 45-year-old oil company executive returns from secondment in Nigeria because of ill health. Over the

last 3 months he has become slow and erratic, making frequent mistakes at work and getting lost on his way home. His memory has become poor and he has had difficulty in finding his words. His appetite has faded and he has lost weight. In the last 2 weeks he has become unsteady on his feet and incontinent of urine.

On examination he is thin. He has no fever but his axillary and inguinal lymph nodes are slightly enlarged. He is drowsy. He had bilateral papilloedema. He has difficulty cooperating with a neurological examination and becomes increasingly irritated when you persist.

a. What do you think is the cause of his symptoms?

(For answers, see p. 256.)

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The effect in pathological terms

Primary brain injury

The brain is an organ of relatively soft consistency contained in a rigid, compartmentalized, unyielding box which has a rough and irregular bottom. Sudden acceleration, deceleration or rotation certainly allow movement of the brain within the skull. If sudden and massive enough, such movement will cause tearing of nerve fibres and petechial haemorrhages within the white matter, and contusions and lacerations of the cortex, especially over the base of the brain.

If the trauma has been severe, the diffuse damage to the brain described above may cause generalized brain swelling, just like the swelling that occurs with injury to any other organ. The brain, however, is contained within a rigid box, unlike other organs of the body. Diffuse brain swelling may result in the brain becoming too large in volume for the space allocated to it. As discussed in Chapter 3 (p. 42), this may lead to tentorial herniation, midbrain compression, impaction of the lower medulla and cerebellar hemispheres in the foramen magnum, secondary brainstem pathology and death (Fig. 4.1).

Severe rotational head injuries may cause primary brainstem injury, which may itself be fatal.

Secondary brain injury

In the circumstances of head injury, the diffusely damaged brain is extremely vulnerable to four other insults, all of which produce further brain swelling (Fig. 4.1). By causing further swelling, each of the four insults listed below tend to encourage the downward cascade towards brainstem failure and death:

1.Arterial hypotension —from blood loss at the time of injury, possibly from the scalp but more probably from an associated injury elsewhere in the body. Hypotension and hypoxia, in isolation but especially in combination, will cause hypoxic– ischaemic brain damage with swelling.

2.Arterial hypoxia —because of airway obstruction, associated chest injury or an epileptic fit.

3.Infection —head injuries in which skull fracture has occurred may allow organisms to enter the skull via an open wound, or from the ear or nose. Infection causes inflammatory oedema.

4.Intracranial haematoma —the force of injury may have torn a blood vessel inside the skull (either in the brain substance or in the meninges) so that a haematoma forms. This causes further compression of the brain by taking up volume within the rigid skull.

CHAPTER 4

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The effect in clinical terms

The clinical instrument that is used to monitor the effects of head injury on patients requiring admission to hospital is the neurological observation chart created by competent, trained nursing staff.

This chart includes the patient’s responsiveness using the Glasgow Coma Scale (GCS), recording the patient’s best eye, verbal and motor responses, together with his vital signs of pupil size and reactivity, blood pressure, pulse, respiratory rate and temperature. The observations are made at intervals appropriate to the patient’s clinical condition —every 15 minutes in critically ill patients.

The Glasgow Coma Scale is described and illustrated in Chapter 11 (p. 184, Fig. 11.3). The changes in the charted observations of best eye, verbal and motor responses are used to signal changes in the patient’s brain condition with great sensitivity. The vital signs of pupil size and reactivity, blood pressure, pulse, respiratory rate and temperature are, essentially, indicators of brainstem function.

Figure 4.2 shows the clinical states that accompany mild, moderate and severe degrees of diffuse cerebral damage after head injury. The adverse influence of hypotension, hypoxia, infection and intracranial haematoma will become apparent in the patient’s chart observations, possibly accompanied by an epileptic fit. (An epileptic fit may be the cause or effect of a deteriorating intracranial situation, undesirable because of the associated anoxia and effects on intracranial pressure.) The appearance of abnormal brainstem signs indicates that the additional insult is adversely affecting the brain very seriously.

Figure 4.2 also shows the clinical clues, and definite signs, that confirm the presence of one or more of the four additional insults. Ideally, the clues should make the doctor so alert to the possibility of the insult becoming operational that the problem is rectified before the patient starts to decline significantly in his Glasgow Coma Scale observations, and certainly before evidence of impaired brainstem function appears. This is what is meant by the prevention of secondary brain injury.

CHAPTER 4