Brain tumours

THIS article will highlight some of the difficulties that can arise when managing patients with intracranial tumours. Neurooncology is a complex and constantly evolving subject but nevertheless certain fundamental principles apply which if attended to will avoid or minimise clinical and medico-legal problems. Interested readers are advised to consult standard texts and, in particular, the relevant NICE guidelines – Improving outcomes for people with brain and other CNS tumours (www.nice.org.uk/csgbraincns).

Scale of the problem

It is important to point out that primary CNS tumours are rare, and the average general practitioner will be unlikely to see more than a handful of cases throughout his practising lifetime. CNS tumours account for 1.6 per cent of cancers in the UK.

Despite their relative rareness, there are many histological subtypes and classification is complex. The use of terms such as benign or malignant which have a readily understandable and clear-cut meaning when discussing tumours outside the CNS are less helpful when considering brain tumours.

Benign tumours tend to be extra-axial, that is they do not arise in the substance of the brain but rather from the meninges, cranial nerves or other structures and produce their effects by compressing the brain from without.

There are of course histologically benign intra-axial tumours such as low-grade pilocytic astrocytomas which arise within the substance of the brain. Malignant tumours which can be primary or secondary tend to be intra-axial.

Glioma is a generic term which suggests that a tumour arises from one of the lines of glial cells such as astrocytes, oligodendrocytes or ependyma. Highgrade gliomas, such as glioblastoma multiforme, are common malignant tumours that arise in adults and have a notoriously poor prognosis.

A meningioma, which is a benign tumour, can nevertheless prove fatal if it causes raised intracranial pressure or leads to status epilepticus. Pituitary adenomas are also benign and can cause blindness by compression of the optic apparatus.

It will be readily appreciated that the classification of brain tumours is complex but the WHO 2007 classification is the most comprehensive and accepted system currently employed.

Treatment is complex and should always be discussed in a multidisciplinary team setting but may consist of surgery alone or supplemented by adjuvant means such as radiotherapy or chemotherapy. The gamma knife which provides focused irradiation in a single session is finding increased use, especially in the management of metastatic disease and small benign tumours such as acoustic neuromas in suitable patients.

Presentation of brain tumours

Clinical presentations of brain tumours include:

• Symptoms and signs of raised intracranial pressure
• Epilepsy
• Focal neurological deficit
• Endocrine disturbance
• Incidental finding.

Headache due to raised intracranial pressure typically has a diurnal variation and is worse in the morning. It can be associated with vomiting, and examination of the fundi may reveal papilloedema.

Focal deficit is obviously variable and will be determined by which area of the brain is involved. For example, a tumour in the right occipital lobe can produce a left homonymous hemianopia, a pituitary adenoma can cause chiasmatic compression, a bitemporal hemianopia or a left temporal lobe tumour may be associated with dysphasia and so forth.

Epilepsy of new onset in an adult patient should raise suspicion of an underlying tumour and investigation is mandated by CT or MRI scanning of the brain. If such tests suggest that the lesion is likely to be a metastasis then further imaging directed at locating the likely primary site is carried out and this typically should include a CT scan of the thorax, abdomen and pelvis.

Diagnosis

When to consider the diagnosis of intracranial tumour.

• Headache arising in a person with no history of headache that persists, especially if associated with nausea.
• Progressive neurological deficit.
• New onset of epilepsy or alteration of pre-existing epilepsy.
• Visual disturbance not explained by refractive error.
• Symptoms of raised intracranial pressure in a person with a past history of malignant disease.

Pitfalls in diagnosis

The two cases presented here highlight some of the pitfalls in the diagnosis of brain tumours.

Case 1
A 54-year-old woman had been attending her GP for over 10 years and periodically pointed out a lump on her head which was increasing in size. She was reassured and told it was a lipoma despite being hard. The lump increased in size and over a period of three months she started to develop progressive weakness of her left leg. She mentioned this to a general surgeon who was seeing her for an unrelated problem and he found a bony lump in the parietal region. An MRI scan was organised which showed a large parasagittal meningioma associated with a large overlying bony exostosis. Following neurosurgical referral, the lesion was excised and she made a good recovery.

Learning points:

• Lesions of the skull may be associated with underlying intracranial pathology.
• Investigation or referral should occur in the face of a lesion which is changing in size.
• Earlier referral would have resulted in the lesion being detected before it had started to cause neurological deficit.

Case 2
A 72-year-old man presented with a two-week history of headache and had a grand mal fit which brought him to hospital. A CT scan was performed which showed a mass lesion with irregular ring enhancement. His case was discussed at the local neuro-oncology MDT meeting where it was held that the radiological appearances were more in favour of an abscess than a malignant tumour and immediate transfer for biopsy was recommended. Unfortunately, due to problems with communication this did not occur and he remained at the local hospital where it was assumed that no action was advocated as the lesion was a malignant brain tumour with a hopeless prognosis. He deteriorated and died four days after the MDT meeting and at autopsy, a brain abscess which had terminally ruptured into the right lateral ventricle was found.

Learning points:

• Neither CT nor MRI scanning is tissue specific.
• Communication between clinicians managing patients is vital especially when different institutions are involved.
• The prognosis of a cerebral abscess and a malignant brain tumour are entirely different and would have been distinguished by biopsy.

Conclusions

It is always difficult to provide advice on uncommon conditions, especially when they present in an unusual or atypical manner. Headache is a very common symptom in general practice but brain tumours are rare. It would be completely inappropriate to refer every patient who presents with headache for a specialist opinion on the basis that they might harbour serious intracranial pathology.

Are there any pointers or “red flags” which should arouse suspicion of intracranial tumour and prompt investigation or referral?

Remember if you don’t consider the diagnosis you will not make it! Despite modern imaging techniques, the era of clinical methods is not yet dead. There is no substitute for taking a detailed history and performing a thorough physical examination. Persistent or progressive symptoms should always raise suspicion of serious underlying pathology and prompt referral to a neurologist or neurosurgeon.

Professor Paul Marks is a consultant neurosurgeon at Leeds General Infirmary and Visiting Fellow in Law, St Chad’s College, University of Durham. He also serves as HM Deputy Coroner, West Yorkshire (Western District)