Tumours of brain, meninges and spinal cord

The commonest brain tumour is metastatic cancer but it is rare for such tumours to present to neurosurgeons unless the primary malignancy is undiagnosed, or the metastasis is solitary and slow growing.

Primary CNS tumours are summarised in Table 22.1.

Table 22.1 Tumours of the central nervous system

Tumour	Origin	Features
Glioma	Derived from supporting tissues of the brain, types include: astrocytoma, oligodendrocytoma, ependymoma	Varying degrees of malignancy depending on cellularity, mitoses, pleomorphism and necrosis
Meningioma	Arise from meninges	Usually benign, rarely recur after removal
Neuroma	Acoustic neuroma (derived from eighth nerve) is commonest	Usually benign
Pituitary	Derived from pituitary gland	Clinical features: Visual disturbance due to pressure on the optic chiasma Metabolic abnormality if the tumour is endocrinologically active

Developmental Derived from abnormal islands of cells at points of neural tube closure, commonest examples are: craniopharyngioma, colloid cyst of third ventricle, medulloblastoma, choroid plexus papilloma Variable degree of malignancy

Cerebral haemorrhage

Cerebral haemorrhage is spontaneous bleeding within the cranial cavity. The three types are:

• intracerebral haemorrhage (within the brain substance)

• subarachnoid haemorrhage (within the subarachnoid space)

• subdural haemorrhage (within the subdural space).

Intracerebral haemorrhage

Intracerebral haemorrhage is associated with hypertension or an underlying abnormality such as vascular malformation or aneurysm. Presentation is with sudden onset headache, neurological deficit or coma.

Diagnosis

Diagnosis is as for subarachnoid haemorrhage, below.

Treatment

Cerebellar haematomas should be removed but there is little benefit in evacuating other intracerebral clots.

Subdural haematoma

Acute subdural bleeding results from trauma (see Ch. 4). Spontaneous bleeding occurs in cerebral atrophy, especially old age and alcoholism. Onset is gradual and may mimic a tumour.

Diagnosis

Diagnosis is as for subarachnoid haemorrhage, above.

Treatment

Evacuation is required.

Hydrocephalus

Hydrocephalus is enlargement of CSF spaces. CSF is made in the lateral ventricles by the choroid plexuses. It passes into the third ventricle then via the aqueduct into the fourth ventricle and out into the subarachnoid space. It is reabsorbed into the blood by arachnoid granulations over the surface of the cerebral hemispheres.

Non-communicating hydrocephalus

This results from blockage, preventing CSF from reaching the subarachnoid space. Causes include intraventricular haemorrhage, congenital abnormalities and tumours.

Spinal degenerative disease

Disc prolapse

Prolapse of an intervertebral disc onto a nerve root causes severe pain in the distribution of the nerve dermatome and weakness of the muscles supplied. The L5/S1 disc is the most commonly affected, causing typical sciatica (pain down the back of the buttock, thigh and leg). MRI is the best method of confirming the diagnosis. Most cases resolve with analgesia and various forms of physical therapy. Surgical microdiscectomy is effective for intractable pain or when there is motor weakness.

Cauda equina compression

A large, central disc prolapse may compress the cauda equine causing bilateral sciatica and urinary retention. Surgical decompression is required urgently to prevent permanent sphincter disturbance.

Lumbar canal stenosis: spinal claudication

Cervical degenerative disease

Acute disc prolapse may cause pain and weakness in the nerve distribution in the same way as lumbar disc disease. Most settle with analgesia and a cervical collar but some require surgical decompression.

Chronic cervical spine degeneration causing gradual cord compression results in the more insidious myelopathy. Usually the arms are more affected than the legs. The combination of neck pain with upper motor neuron leg signs suggests cervical cord compression.

MRI is the imaging modality of choice, and surgical decompression may be necessary.

Peripheral nerve lesions

Most disorders are due to trauma or entrapment (Table 22.2). Motor and sensory loss result. Nerve conduction studies allow confirmation of the site of the lesion and whether it is complete (i.e. unlikely to recover) or incomplete. Clean traumatic transections of peripheral nerves may be repaired using microsurgical methods. Entrapments can be released by decompression.

Table 22.2 Features of common peripheral nerve lesions

Nerve	Clinical features	Causes
Facial	Facial weakness	Trauma, parotid surgery, acoustic neuroma, Bell’s palsy
Radial	Weakness of wrist/finger extension	Fractures of shaft of humerus
Median	Weakness of opposition of thumb, thenar eminence wasting, numbness of lateral three digits	Carpal tunnel syndrome
Ulnar	‘Claw hand’, wasting of interossei	Entrapment/trauma around elbow (medial epicondyle)
Femoral	Quadriceps weakness	Groin trauma (iatrogenic)
Sciatic	Pain down back of leg, weakness of foot extension and eversion	Lumbar disc prolapse
Common peroneal	Foot drop	Trauma around head of fibula