Neurology: Oncology and Hydrocephalus

🧭 This chapter brings together brain tumours and hydrocephalus. Acute spinal cord compression, meningitis and encephalitis are covered in the Neurological Emergencies chapter.
Your four questions for every patient: Is there a structural cause that needs imaging? Is this a treatable complication of a systemic disease, drug or infection? Is the problem functional - and have I made a positive diagnosis rather than just excluding things? What does the patient need to know about driving and safety?

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Brain Tumours

Types:

• Metastases - the commonest brain tumours in adults. They come from the lung (the commonest), breast, melanoma, kidney and colon. Often multiple, at the grey–white matter junction.
• Gliomas (WHO 2021 classification uses molecular markers):
  • Glioblastoma (IDH-wildtype) - the commonest primary malignant tumour; older adults; aggressive. MRI with contrast. Glioblastoma shows ring enhancement with central necrosis and surrounding oedema.
• Astrocytoma, IDH-mutant - younger adults; slower.
• Oligodendroglioma (IDH-mutant, 1p/19q codeleted) - often presents with seizures; best prognosis of the gliomas; often calcified.

Meningioma: The commonest primary brain tumour overall - usually benign, slow-growing, arising from the meninges. Commoner in women; after radiation; in NF2. Often found by chance. Meningioma MRI with contrast shows a dural-based enhancing mass with a "dural tail"

Primary CNS lymphoma: Immunosuppressed people (HIV, transplant) and older adults. Deep periventricular lesions. Avoid steroids before biopsy if possible - they can make the lymphoma disappear temporarily and prevent diagnosis.

Others:

• Vestibular schwannoma (acoustic neuroma) - one-sided hearing loss, tinnitus, imbalance.
• Pituitary tumours (see the Pituitary chapter).
• Craniopharyngioma.
• Haemangioblastoma (VHL).
• Children: medulloblastoma, pilocytic astrocytoma, ependymoma (posterior fossa).

How brain tumours present:

• Seizures - especially low-grade gliomas and meningiomas. A new seizure in an adult always needs brain imaging.
• Progressive focal deficit - weakness, speech or visual field loss developing over weeks.
• Cognitive or personality change (frontal tumours) - can be mistaken for depression or dementia.
• Raised intracranial pressure: Headache worse on lying down, coughing and in the morning. Vomiting. Papilloedema. Sixth nerve palsy. Drowsiness.
• Headache alone is an uncommon presentation.

Referral (NICE NG12): Adults with progressive, subacute loss of central neurological function should have an urgent direct-access MRI (or CT) or suspected cancer referral.

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Managing Brain Tumours

• Imaging: MRI with contrast. Glioblastoma shows ring enhancement with central necrosis and surrounding oedema; meningioma shows a dural-based enhancing mass with a "dural tail".
• Differential diagnosis of a ring-enhancing lesion:
  • Glioblastoma.
  • Metastasis.
  • Abscess.
  • Toxoplasmosis (HIV).
  • Lymphoma.
  • Tumefactive demyelination.
  • Radiation necrosis.
• Symptom control:
  • Dexamethasone for symptomatic brain swelling (e.g. 8–16 mg daily, then reduce to the lowest effective dose). Give a PPI, monitor glucose, and watch for steroid myopathy, infection and mood change. Give in the morning.
  • Seizures: Levetiracetam (few interactions with chemotherapy). No routine prevention without seizures.
  • VTE is common - prophylaxis and treatment as appropriate.
• Glioblastoma (NICE NG99):
  • Maximal safe surgical resection, then radiotherapy with temozolomide, then 6 cycles of temozolomide.
  • MGMT promoter methylation predicts better response to temozolomide.
  • Median survival about 12–18 months.
  • Shorter radiotherapy courses for older or frailer patients.
• Lower-grade gliomas: Surgery, radiotherapy and chemotherapy (PCV or temozolomide). IDH inhibitors (e.g. vorasidenib) are a newer option for some IDH-mutant tumours.
• Meningioma: Watch-and-scan if small and without symptoms; surgery or stereotactic radiosurgery if growing or symptomatic.
• Brain metastases:
  • Stereotactic radiosurgery for a limited number of lesions; surgery for a single large lesion.
  • Systemic therapies that cross into the brain (e.g. targeted drugs in lung cancer and melanoma).
  • Whole-brain radiotherapy is now used less often.
  • Best supportive care for poor performance status.
• Holistic care:
  • Clinical nurse specialist.
  • Rehabilitation.
  • Cognitive and mood support.
  • Driving (DVLA rules depend on tumour type and treatment).
  • Early palliative care and advance care planning.

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Paraneoplastic Neurological Syndromes

What they are: Immune attacks on the nervous system triggered by a cancer elsewhere. They often appear before the cancer is found, develop over weeks, and can be very disabling.

Syndrome	Typical antibody and cancer
Lambert–Eaton syndrome	VGCC - small cell lung cancer
Subacute cerebellar degeneration	Anti-Yo (ovary, breast); anti-Tr (Hodgkin lymphoma); anti-Hu
Limbic encephalitis	Anti-Hu (small cell lung cancer); anti-Ma2 (testicular cancer); anti-AMPA, GABA-B
Sensory neuronopathy	Anti-Hu - small cell lung cancer
Opsoclonus–myoclonus	Anti-Ri (breast); neuroblastoma in children
Stiff person syndrome	Anti-amphiphysin (breast); anti-GAD (usually not paraneoplastic - associated with type 1 diabetes)
Anti-NMDA receptor encephalitis	Ovarian teratoma

• Search for the cancer: CT chest, abdomen and pelvis; PET-CT; mammography, testicular or pelvic ultrasound as relevant. Repeat for up to 2–4 years if negative.
• Treatment: Treat the cancer - the most important step. Add immunotherapy (steroids, IVIg, plasma exchange, rituximab); syndromes with antibodies to intracellular targets (Hu, Yo) respond poorly.

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Hydrocephalus and Normal Pressure Hydrocephalus

• Hydrocephalus: Enlarged ventricles from blocked or poorly absorbed CSF.
  • Obstructive (non-communicating) - tumour, aqueduct stenosis, colloid cyst, posterior fossa haemorrhage.
  • Communicating - after subarachnoid haemorrhage, meningitis or head injury (absorption blocked).
  • Acute hydrocephalus causes headache, vomiting, drowsiness and upgaze palsy - neurosurgical emergency (external ventricular drain).
• Normal pressure hydrocephalus (NPH):
  • Older adults; often idiopathic, or after SAH, meningitis or head injury.
  • Classic triad:
    • Gait disturbance first - broad-based, shuffling, "magnetic" gait with difficulty turning.
    • Urinary urgency and incontinence.
    • Cognitive slowing (frontal-subcortical).
  • Imaging: Enlarged ventricles out of proportion to atrophy (Evans index over 0.3), with tight high-convexity sulci.
  • Tap test: Remove 30–50 mL of CSF by LP and re-test gait, or use a lumbar drain for several days. Improvement predicts benefit from a shunt.
  • Treatment: Ventriculoperitoneal shunt. Gait responds best; cognition responds least.
  • Mimics: vascular parkinsonism, Parkinson's disease, cervical myelopathy, Alzheimer's disease.
• Shunt problems:
  • Blockage - headache, vomiting, drowsiness (raised pressure) - urgent neurosurgical review.
  • Infection - often within months of surgery (staphylococci).
  • Over-drainage - low-pressure headache, subdural collections.

Drug Reference Table

Drug	Key points
Dexamethasone e.g. 8–16 mg daily, then reduce	Brain tumour oedema; give with a PPI; check glucose; avoid before biopsy if lymphoma is suspected.
Levetiracetam	Seizures with brain tumours; few interactions.
Temozolomide	Glioblastoma with radiotherapy; myelosuppression; better response if MGMT is methylated.

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Spot the Diagnosis

Clue	Diagnosis
Ring-enhancing lesion with central necrosis and oedema in a 68-year-old	Glioblastoma (or metastasis)
Dural-based enhancing mass with a dural tail	Meningioma
Deep periventricular lesion that shrank after steroids in a transplant recipient	Primary CNS lymphoma
Rapid unsteadiness in a woman, anti-Yo antibodies	Paraneoplastic cerebellar degeneration (ovarian or breast cancer)
Shuffling magnetic gait, incontinence and slowed thinking, big ventricles	Normal pressure hydrocephalus

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Exam-style Scenarios

1. A 62-year-old has had 6 weeks of worsening left arm weakness and personality change. MRI shows a right frontal ring-enhancing mass with oedema.
Answer: Likely glioblastoma (or metastasis).

• Dexamethasone with a PPI; glucose checks.
• CT chest, abdomen and pelvis to look for a primary.
• Neuro-oncology MDT: maximal safe resection, then radiotherapy with temozolomide.
• Seizure plan; DVLA advice; specialist nurse and palliative care.

2. A 75-year-old has 1 year of a shuffling gait, then urinary urgency and slowed thinking. CT shows enlarged ventricles.
Answer: Suspected normal pressure hydrocephalus.

• CSF tap test (or lumbar drain) with gait assessment before and after.
• Refer to neurosurgery for a VP shunt if he improves.

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Key Points

• Metastases are the commonest brain tumours; glioblastoma is the commonest primary malignant one; meningioma is the commonest primary overall.
• A new seizure or a progressive focal deficit in an adult needs brain imaging.
• Dexamethasone for tumour oedema (with PPI and glucose checks); avoid steroids before biopsy if lymphoma is likely.
• Glioblastoma: surgery, radiotherapy and temozolomide; MGMT methylation predicts response.
• Paraneoplastic syndromes often come before the cancer - search with CT and PET.
• NPH: gait, incontinence, cognition - tap test, then shunt.

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Guidelines and Further Reading

• NICE NG99: Brain tumours (primary) and brain metastases in over 16s
• NICE NG12: Suspected cancer - recognition and referral
• WHO Classification of Tumours of the Central Nervous System (2021)

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