CNS tumours

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CNS Tumours: Neurosurgical and Anaesthetic Considerations

Classification of CNS Tumours

Primary Intracranial Tumours

Tumour Type Notes
Astrocytoma Range from low-grade (WHO Grade I/II) to high-grade glioblastoma (Grade IV); prognosis worsens with grade.
Oligodendroglioma Often slow-growing; characterised by 1p/19q co-deletion; chemosensitive.
Ependymoma Predominantly in children; 4th ventricle common site. Surgical resection is primary therapy.
Embryonal Tumours (PNETs) Includes medulloblastoma (most common malignant paediatric CNS tumour), pineoblastoma, neuroblastoma. High CSF dissemination risk.
Meningioma Extra-axial, mostly benign (WHO Grade I); may recur. Often parasagittal or skull base.
Pituitary Adenoma Endocrine effects vary (e.g. Cushing’s, acromegaly, prolactinoma); usually transsphenoidal approach.
Vestibular Schwannoma (Acoustic neuroma) Benign CN VIII tumour; bilateral in NF2. May require retrosigmoid or translabyrinthine approach.
Primary CNS Lymphoma Typically high-grade B-cell; immunosuppressed patients; responsive to steroids and chemotherapy.

Secondary (Metastatic) Tumours

  • Common primaries: lung, breast, melanoma, renal, colon.
  • Often supratentorial; haemorrhagic tendency (esp. melanoma, RCC, choriocarcinoma).
  • Surgical resection for large symptomatic lesions or diagnostic uncertainty.

Preoperative Considerations

Raised Intracranial Pressure (ICP)

Clinical signs Mechanisms
Nausea, vomiting, headache Stimulation of area postrema
Depressed GCS, confusion Global cortical dysfunction
Mydriasis, bradycardia, hypertension (Cushing’s triad) Brainstem compression
Abnormal respiration Central or obstructive pattern
Papilloedema (late sign) Raised ICP over time
  • CT/MRI prior to GA is essential if GCS < 15 or focal signs.
  • Steroids (e.g. dexamethasone 8–16 mg/day) reduce vasogenic oedema, especially in metastases or meningiomas.

Anaesthetic Management

Premedication And Sedation

  • Caution with sedatives: Risk of CO₂ retention → ↑ ICP; avoid in patients with raised ICP or reduced consciousness.
  • Anticonvulsant continuation: Important in seizure-prone tumours (e.g. cortical gliomas, meningiomas)

Induction

  • Goals: Minimise ICP spikes, preserve MAP and CPP.
  • Options:
    • Propofol 1.5–2.5 mg kg⁻¹: cerebral vasoconstrictor.
    • Etomidate 0.3 mg kg⁻¹: cardiovascular stability.
    • Ketamine: Now considered safe in patients with controlled ICP; not first-line.
  • Neuromuscular Blockade:
    • Rocuronium 1.0–1.2 mg kg⁻¹ for rapid sequence; avoid suxamethonium if ↑ICP or tumour mass.

Airway And Haemodynamic Control

  • Blunt intubation response: fentanyl, lignocaine, beta-blockers.
  • Maintain CPP 60–70 mmHg: use vasopressors if needed (e.g. noradrenaline).
  • Avoid hypotension (even transient)–associated with worse outcomes.

Maintenance of Anaesthesia

Parameter Consideration
Volatile agents Isoflurane, sevoflurane: dose-dependent ICP increase; limit to ≤ 1 MAC.
TIVA (e.g. propofol/remifentanil) Preferred if intraoperative neurophysiological monitoring (NIM, MEPs, SSEPs) planned.
Neuromonitoring impact Volatiles suppress signals; NMBAs interfere with motor pathways. Confirm monitoring plan preoperatively.

Special Considerations

Positioning

Position Indications Key Concerns
Sitting Posterior fossa access Risk of venous air embolism (VAE), hypotension
Lateral/prone Cerebellar, occipital Eye protection, venous return
Supine Frontal, parasagittal May elevate head 30° to facilitate venous drainage
  • Preload with fluids, ensure adequate IV access and invasive monitoring if sitting.

Intravenous Access & Fluids

  • Use 2 × large bore cannulae.
  • Balanced crystalloids preferred; avoid hypo-osmolar fluids (e.g. 0.45 % NaCl).
  • Prepare for blood loss in vascular tumours (e.g. meningiomas, metastases).

Blood Products

  • Crossmatch if expected bleeding or coagulopathy.
  • Check coagulation in those on anticoagulants or with CNS lymphoma.

Monitoring

Modality Indications
Arterial line All supratentorial or posterior fossa craniotomies
CVP line If VAE risk (sitting) or fluid shifts
Capnography Detect VAE (sudden ↓ EtCO₂), guide ventilation
Precordial Doppler / TEE For high-risk VAE (sitting position)
ECG & NIM Brainstem monitoring (bradycardia, arrhythmias)

Emergence and Postoperative Considerations

Goals

  • Rapid, smooth emergence for early neurological assessment.
  • Avoid coughing, straining, hypertension (increases bleeding, ICP)

Strategies

  • Titrate anaesthetic depth and opioids.
  • Consider short-acting agents (remifentanil, dexmedetomidine).
  • Extubation criteria: airway protection, adequate ventilation, baseline neurostatus

Postoperative Complications

  • Bleeding, brain swelling, seizures.
  • Delayed awakening: Consider residual sedation, surgical cause (e.g. oedema, haemorrhage), metabolic derangement.

Summary Table

Domain Key Point
ICP Preoperative steroid (dexamethasone) and mannitol for raised ICP
Induction Propofol or etomidate; avoid hypotension
Maintenance TIVA preferred for neuromonitoring; avoid volatiles > 1 MAC
Positioning Sitting increases VAE risk–monitor with Doppler/TEE
Monitoring A-line, EtCO₂, ECG, Doppler (if sitting), NIM where applicable
Emergence Smooth, rapid; watch for delayed recovery and airway protection

Links

References:

  1. Pasternak JJ, Lanier WL. Neuroanesthesiology update. J Neurosurg Anesthesiol. 2009 Apr;21(2):73-97. doi: 10.1097/ANA.0b013e31819a0103. PMID: 19295386.
  2. Gupta A, Goyal R. Anaesthetic considerations in supratentorial and infratentorial tumour surgery. Indian J Anaesth. 2022;66(Suppl 1):S30–S36.
  3. Cottrell JE, Young WL. Cottrell and Patel’s Neuroanesthesia, 6th ed. Elsevier; 2016.
  4. Mashour GA, Hervey-Jumper SL, Zhou J, et al. Perioperative considerations for brain tumour patients. Br J Anaesth. 2023;130(2):e21–e34.
  5. Johnson MD, et al. Venous air embolism in the sitting position: prevention and management. Anesthesiology Clinics. 2022;40(3):571–584.
  6. Miller RD, Cohen NH, Eriksson LI, et al. Miller’s Anesthesia, 9th ed. Elsevier; 2020.
  7. Zheng K, et al. Anaesthetic management for intraoperative neuromonitoring. Curr Opin Anaesthesiol. 2023;36(5):597–604.
  8. SAJAA Expert Panel. Practical neuroanaesthesia for SA neurosurgical units. SAJAA. 2021;27(4):198–207.

Summaries:

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