Lésions intracrâniennes occupant l'espace

What is a space-occupying lesion of the brain?

A space-occupying lesion of the brain is usually due to a tumour (53% of these in the UK are benign and 47% are malignant ¹) but it can be caused by other pathology such as an abscess or a haematoma. About half of intracerebral tumours are primary but the rest have originated outside the CNS and are metastases.²

The effect of the tumour may be local, due to focal brain damage; the presentation may give an indication of the location of the lesion but not its aetiology. There may be more general symptoms related to raised intracranial pressure or seizures, behavioural changes, or false localising signs. Large lesions in some regions, such as the frontal lobe, may be relatively silent whilst a small lesion in the dominant hemisphere may devastate speech.

A tumour may infiltrate and destroy important structures, it may obstruct the flow of cerebrospinal fluid (CSP) and cause hydrocephalus or it can induce angiogenesis (new blood vessels) and break down the blood brain barrier, causing oedema.

Presenting features may include localising signs, generalised signs and false localising signs. A rapid onset of symptoms suggests a cerebrovascular lesion whilst a space-occupying lesion of the brain will usually be more gradual. However, a space-occupying lesion of the brain can mimic a stroke.

Features of a des maux de tête indicating a high risk of a space-occupying lesion of the brain or idiopathic intracranial hypertension include:³

• A new headache with features suggestive of raised intracranial pressure, including papilloedema, vomiting, posture-related headache, or headache waking the patient from sleep.

• A new headache with focal neurological symptoms, or non-focal neurological symptoms such as blackout, and change in personality or memory.

• An unexplained headache that becomes progressively severe.

• An unexplained headache in anyone previously diagnosed with cancer or HIV.

• A new onset of epileptic seizures.

Voir également le document séparé Épilepsie chez les adultes et Épilepsie chez les enfants et les jeunes articles.

Many of the following features of a space-occupying lesion may be due to raised intracranial pressure.

• Headache:

  • The classic brain tumour headache (eg, worse in the morning and worse on bending or Valsalva manoeuvre) is not as common as a tension-type presentation or migraine.

  • A change in the pattern or frequency of headaches is a cause for concern.

  • Headache is more common in posterior fossa tumours and rapidly growing tumours.

  • Isolated headache is an uncommon presentation of a space-occupying lesion.

• Vomiting may occur. This may be without accompanying nausea.

• Nausea may be a feature.

• A change in mental status or a behavioural change is a cause for concern.

• There may be weakness, ataxia or disturbance of gait.

• Even deficits of speech or vision may be poorly localising signs.

• There may be generalised convulsions.

If there are generalised convulsions, try to get a good history. As described in the diagnosis of epilepsy, they may start with focal signs and then progress to a generalised convulsion as in Jacksonian epilepsy. The first features of the episode may be a good localising sign.

If raised intracranial pressure is suspected it is imperative to use the ophthalmoscope to look for œdème papillaire. This may be more marked in children than in adults.

If epilepsy starts in middle age or beyond, a space-occupying lesion of the brain is one of the possible diagnoses that should be considered.

Many patients have headaches. Very few have brain tumours. The signs and symptoms above can help to differentiate but it remains difficult to diagnose based on headache alone.⁴

• The abducent nerve (cranial VI) has a long and tortuous intracranial path that makes it vulnerable. Abducent nerve palsy is not a useful localising sign. It supplies the lateral rectus muscle and its action is to move the eye laterally - as described in diplopia et cranial nerve lesions.

• Syndrome de Horner is not a good localising lesion, as the path of the sympathetic nerves is also long but, as there is no chiasma (fibres don't cross the midline), it is a good lateralising sign. The lesion may also be outside the skull.

• If a headache is unilateral, this is often a good indicator of the side of the lesion.

• Cerebellar signs do not help to localise the lesion.

Cerebellum

Cerebellar ataxia is described more fully elsewhere. Space-occupying lesions represent only a small part of the differential diagnosis.

• Ataxia may present as general clumsiness.

• Intention tremor is worst at the end of a movement and leads to past-pointing. Ask the patient first to touch their nose with the index finger, and then your index finger, held about 50 cm away and back to their nose again. A sign is positive when the patient tends to point beyond your finger.

• Dysdiadochokinesis is tested by asking the patient to hold up their hands and rapidly pronate and supinate repetitively. Ask them to tap the back of their hand as fast as possible.

• Nystagmus may be seen.

• If truncal ataxia is worse when the eyes are closed, the lesion is in the dorsal columns, not the cerebellum.

• Cerebellar speech is described as staccato.

• Causes of cerebellar signs include brain tumours (see also Tumeurs cérébrales chez les enfants), acoustic neuroma, Ataxie de Friedreich, AVC, haemangioma, sclérose en plaques, chronic alcohol excess and intracranial abscess.

Temporal lobe

Lésions du lobe temporal often present with rather vague psychological problems.

• There may be depersonalisation, emotional changes and disturbances of behaviour.

• Épilepsie du lobe temporal - there can be hallucinations of smell, taste, sound and sight. There may be déjà vu in which there is a feeling of familiarity as if the present has happened before.

• Dysphasia may be noted.

• Défauts du champ visuel involve the contralateral upper quadrant.

• Other psychological problems include forgetfulness, fugue (a disturbed state of consciousness in which the patient seems to perform acts in full awareness but upon recovery cannot recollect them), functional psychosis and fear or rage. There may be inappropriate sexual behaviour but the Kluver-Bucy syndrome is extremely rare.

Frontal lobe

• Frontal lobe tumours can cause anosmia. This is especially significant if it is unilateral.

• There may be a change in personality with the person becoming indecent, indiscreet or dishonest.

• Dysphasia can occur if Broca's area is involved.

• Hemiparesis or fits may affect the contralateral side.

Parietal lobe⁵

Parietal lobe lesions can produce a neurological picture that includes the following:

• There may be hemisensory loss.

• Decreased two-point discrimination.

• Astereognosis is the inability to recognise a familiar object placed in the hand.

• Extinction can be demonstrated by asking the patient to close their eyes and touch one side of their body. Ask the patient to point to where you touched. Repeat this but touching both sides simultaneously. The patient will acknowledge only one side.

• The patient may systematically ignore one side of their body, called sensory inattention. If you ask them to draw a clock face, they omit the half contralateral to the lesion.

• Dysphasia may occur.

• Syndrome de Gerstmann can be congenital or acquired. The four components are:
  

  • Agraphia or dysgraphia.

  • Acalculia or dyscalculia.

  • Finger agnosia.

  • Left-right disorientation.

Occipital lobe

A lesion in front of the optic chiasma will affect just one eye. A lesion at the optic chiasma, such as a pituitary adenoma, classically causes a bitemporal hemianopia (as decussating fibres are affected).

A lesion posterior to the optic chiasm will cause a crossed homonymous field defect (eg, left optic tract lesion causing a right homonymous hemianopia). A lesion in the visual cortex will cause congruent contralateral visual field defects.

A visual field defect from the eye or optic nerve will be seen as a black area but loss of the visual cortex often leads to ignoring the affected area.

Voir également le document séparé Défauts du champ visuel article.

Cerebellopontine angle

The most common pathology here is an acoustic neuroma. Common features include:

• Ipsilateral deafness.

• Tinnitus.

• Nystagmus.

• Reduced corneal reflex.

• Facial and trigeminal nerve palsies.

• Ipsilateral cerebellar signs.

Corpus callosum

This is an interesting part of the brain that communicates between the two sides. Lesions usually cause severe rapid intellectual deterioration with focal signs of adjacent lobes. There may be signs of loss of communication between the lobes, such as inability of the left hand to carry out verbal commands.

Midbrain

The following features suggest a midbrain lesion:

• Pupilles inégales.

• Inability to direct the eyes up or down.

• Amnesia for recent events, with confabulation.

• Somnolence.

Pituitary tumours

Si tumeurs hypophysaires are large they can cause homonymous hemianopia but the most obvious presenting features may be related to their endocrine effects.

• Routine blood tests will include FBC, U&E and LFTs. Na+ may be low due to inappropriate ADH secretion.

• Imaging studies will usually be via an MRI scan as the imaging modality of choice but CT scans may also be used.⁶

• Biopsy of the lesion may be indicated.

• A known primary tumour may exist or it may be sought by CTCAP.

Imaging may indicate the site of a lesion but usually it will not indicate the nature, including whether it is a tumour or an abscess.

Malignité

• Metastases, gliomas, meningiomas, pituitary adenomas and acoustic neuromas account for 95% of all brain tumours.

• In adults, two thirds of primary brain tumours are supratentorial; however, in children, two thirds of brain tumours are infratentorial.

• Primary cerebral tumours include astrocytomas, glioblastoma multiforme, oligodendrogliomas and ependymomas.

• Primary brain tumours do not usually metastasise.

• About 50% of brain tumours are metastatic ²and of these about 50% are multiple. About 4-10% of people with cancer develop cerebral metastases. ⁷⁸ See also the separate Carcinomatosis article.

• The most common primary is lung cancer followed by malignant melanoma, renal carcinoma, breast cancer and carcinoma of the colon.²

Voir également le document séparé Tumeurs cérébrales chez les enfants et Tumeurs cérébrales chez les adultes articles.

Other space-occupying lesions

• A haematoma may follow a head injury. Risk factors include old age and anticoagulation.

• Hydrocéphalie.

• Cerebral abscesses are uncommon but risk factors include chronic obstructive pulmonary disease (COPD) that may be a source of infection to the systemic circulation and a right-to-left shunt that permits infection to bypass the lungs that would normally filter it out. Cerebral abscesses are multiple in 25% of cases.

• Cysts that may occur in the brain include arachnoid cysts (in the subarachnoid space), colloid cysts, dermoid cysts and epidermoid cysts.

• Cerebral amoebiasis et cysticercosis are rare.

• Both infection and lymphomas of the CNS are more common with HIV infection.

• Granuloma and tuberculoma can occur.

Other causes of focal CNS signs include:

• AVC.

• Traumatisme crânien.

• Vascularite including lupus érythémateux systémique, syphilis, périartérite noueuse et artérite à cellules géantes.

• Sclérose en plaques.

• Encéphalite.

• Post-ictal state (Todd's palsy).⁹

Management includes treatment of the underlying lesion, management of raised intracranial pressure, and treatment for any other complications (eg, anticonvulsants) and symptomatic treatment (eg, for headaches and for nausea and vomiting).