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Head CT: Cerebral Malaria

Cerebral malaria is a life-threatening manifestation of Plasmodium falciparum infection defined clinically by coma (Blantyre Coma Score <=2 or GCS <11) in the presence of asexual parasitaemia after exclusion of other encephalopathies. Head CT is used chiefly to exclude alternative or coexisting surgical and infective causes of altered consciousness and to detect diffuse cerebral oedema, which carries prognostic weight. Imaging is frequently normal early in the disease, and a normal scan does not exclude the diagnosis, which remains clinical and parasitological.

Indications

  • Severe P. falciparum malaria with impaired consciousness, coma or persistent obtundation
  • New-onset or repetitive seizures, status epilepticus in an endemic setting
  • Focal neurological deficit raising concern for stroke, abscess or mass lesion
  • Failure to regain consciousness after correction of hypoglycaemia and control of seizures
  • Clinical deterioration or signs of raised intracranial pressure before lumbar puncture
  • Exclusion of alternative causes of coma (meningitis, encephalitis, intracranial haemorrhage) in a febrile comatose patient

Contraindications & Cautions

  • No absolute contraindication for non-contrast CT in an obtunded emergency patient; benefit outweighs radiation risk
  • Pregnancy (common in endemic regions): shield the gravid abdomen; head CT fetal dose is negligible but justify the study
  • Iodinated contrast: caution with acute kidney injury from severe malaria (blackwater fever, ATN) and dehydration; hydrate and check renal function where feasible
  • Prior severe contrast reaction warrants premedication or avoidance of contrast
  • Apply ALARA and paediatric dose-reduction protocols, as many patients are children

Patient Preparation

  • Stabilise airway, breathing and circulation; treat hypoglycaemia and seizures before transfer
  • Correct hypoglycaemia (common and treatable mimic of coma) and check point-of-care glucose
  • Secure intravenous access and continue antimalarial therapy (IV artesunate) without delay for imaging
  • Supine positioning with head immobilised; sedation or intubation may be required for the agitated or fitting child
  • Obtain consent from accompanying guardian where possible; proceed under emergency provision if not
  • Remove metallic hair ornaments and monitor oxygen saturation throughout

Technique & Parameters

  • Non-contrast helical head CT from foramen magnum to vertex, gantry angled to the orbitomeatal line
  • Typical adult parameters 120 kVp, 250-350 mAs with automatic exposure control; reduce mAs and kVp for children
  • Reconstruct 4-5 mm axial slices for brain and thin 0.6-1 mm for bone; add coronal and sagittal reformats
  • Review on brain (W80/L40), subdural (W150-200/L50-80) and bone windows
  • Add iodinated contrast (approximately 1-2 mL/kg) only if abscess, empyema, tumour or venous thrombosis is suspected
  • CT venography if cerebral venous sinus thrombosis is considered in the differential

Systematic Review

  • Assess grey-white matter differentiation and sulcal/cisternal effacement as markers of diffuse oedema
  • Evaluate ventricular size and configuration for compression or hydrocephalus
  • Search for parenchymal, subarachnoid or intraventricular haemorrhage on soft-tissue windows
  • Inspect for focal hypodensity indicating infarction (arterial territory or watershed)
  • Check basal cisterns and brainstem for effacement suggesting transtentorial herniation
  • Look for ring-enhancing lesions or extra-axial collections if contrast given
  • Review bone windows and scalp for trauma as an alternative cause of coma

Key Findings & Significance

  • Diffuse cerebral oedema: sulcal effacement, small ventricles, loss of grey-white differentiation - associated with poorer outcome
  • Often normal parenchyma early despite deep coma
  • Petechial or larger haemorrhages reflecting microvascular sequestration and endothelial injury
  • Territorial or watershed infarction from microvascular obstruction
  • Brainstem compression or effacement of basal cisterns indicating impending herniation
  • Absence of a mass lesion or meningeal enhancement helps exclude surgical and alternative infective causes

Differential Considerations

  • Diffuse oedema with coma: cerebral malaria versus hypoglycaemic or hypoxic-ischaemic encephalopathy
  • Ring-enhancing lesion: pyogenic abscess, tuberculoma, toxoplasmosis, neurocysticercosis
  • Meningeal enhancement and hydrocephalus: bacterial or tuberculous meningitis
  • Lobar or deep haemorrhage: hypertensive bleed, venous infarction, coagulopathy
  • Focal infarct: embolic stroke, vasculitis, sickle cell vasculopathy in coexisting haemoglobinopathy
  • Dense venous sinus (cord/dense triangle sign): cerebral venous sinus thrombosis

Pearls & Pitfalls

  • A normal CT never excludes cerebral malaria; the diagnosis is clinical and parasitological
  • Malarial retinopathy on funduscopy is more specific than imaging and supports the diagnosis
  • Always exclude and treat hypoglycaemia before attributing coma to malaria
  • Diffuse oedema and small ventricles can be subtle - compare with age-expected sulcal pattern in children
  • Beware coexisting pathology: bacterial meningitis and malaria can occur together
  • Motion and beam-hardening in the posterior fossa can mimic or obscure brainstem changes

Structured Report

  • State scan type, coverage and whether contrast was administered
  • Comment on presence and severity of cerebral oedema (grey-white differentiation, sulcal/cisternal effacement)
  • Describe any haemorrhage, infarction, mass lesion or extra-axial collection
  • Assess for mass effect, midline shift and signs of herniation with measurements
  • Explicitly address alternative causes of coma (abscess, meningitis, haemorrhage, thrombosis)
  • Impression: correlate with parasitaemia, glucose and retinopathy; advise MRI if diagnostic uncertainty and clinical stability permit

References

  • WHO Guidelines for the Treatment of Malaria (severe malaria management)
  • ACR Appropriateness Criteria: Altered Mental Status, Coma, Delirium and Psychosis
  • Mohanty S et al., Brain swelling and mannitol in cerebral malaria (RadioGraphics/clinical neuroradiology literature)
  • Osborn's Brain: Imaging, Pathology, and Anatomy (infection chapter)

Educational clinical decision support only. Protocols vary by institution and equipment; always confirm with a qualified radiologist and local guidelines before clinical use.