A 9-year-old girl with complex cyanotic congenital heart disease, managed conservatively, presents with: • Fever for 5 days ,Headache for 2 days ,Poor oral intake for 24 hours , Reduced urine output for 6 hours On examination: • Dehydrated ,Febrile ,Glasgow Coma Scale (GCS): 12/15 ,No focal neurological deficits Investigations: • Haemoglobin: 22 g/dL, Packed cell volume (PCV): 60% ,White blood cell count: 15 × 10⁹/L ,Platelets: 90 × 10⁹/L ,Sodium: 142 mmol/L , Potassium: 4.2 mmol/L What is the most likely cause of her current condition? A. Bacterial meningitis B. Cerebral abscess C. Cerebral venous thrombosis D. Infective endocarditis E. Intracranial haemorrhage
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Answer: C. Cerebral Venous Thrombosis (CVT)
Why CVT is the most likely diagnosis
This case presents the classic triad that predisposes to CVT in cyanotic congenital heart disease (CHD):
| Factor | This patient |
|---|---|
| Polycythaemia / hyperviscosity | Hb 22 g/dL, PCV 60% |
| Dehydration | Poor intake 24 h, reduced urine output 6 h, clinically dehydrated |
| Underlying cyanotic CHD | Polycythaemia, venous stasis, central venous hypertension |
As Bradley and Daroff's Neurology in Clinical Practice directly states:
"Cerebral venous thrombosis [can result] secondary to the combination of polycythemia, venous stasis, and central venous hypertension."
The same textbook notes that the most common associated cardiac lesions are Tetralogy of Fallot (TOF) and transposition of the great arteries - exactly the kind of complex cyanotic CHD described here.
Mechanism
In cyanotic CHD, the right-to-left shunt causes chronic hypoxaemia. The body compensates with reactive polycythaemia. When a child becomes dehydrated (as here - fever for 5 days, poor oral intake, reduced urine output), plasma volume falls further, dramatically increasing blood viscosity. This sluggish, hyperviscous blood in the cerebral venous sinuses precipitates thrombosis. The raised ICP from venous obstruction explains:
- Headache (2 days)
- Reduced GCS (12/15)
- Fever can be either the precipitant (via dehydration) or a consequence of the inflammatory response
The thrombocytopaenia (platelets 90 x10⁹/L) is also consistent - platelet consumption occurs in extensive venous thrombosis.
Why the other options are less likely
A. Bacterial meningitis - Possible with fever and reduced GCS, but there is no mention of meningism (neck stiffness, Kernig's sign), photophobia, or a petechial rash. Also does not account for the polycythaemia/dehydration picture, and the white cell count (15 x10⁹/L) is only mildly elevated.
B. Cerebral abscess - This is a real risk in cyanotic CHD (incidence 2-6%, mostly in uncorrected TOF) and must be considered. However, early brain abscess typically presents with focal neurological signs (present in 75% eventually), and as many as 75% of patients are afebrile early on. This child has no focal deficits and is febrile from day 1. The acute dehydration history strongly points to CVT rather than an indolent abscess. Brain abscess also develops more subacutely (days to weeks of headache, vomiting, personality change). - Bradley and Daroff's Neurology, p. 1242
D. Infective endocarditis - Can cause neurological complications (cerebral emboli, abscess, meningitis), but there is no mention of a new murmur, embolic phenomena, or prolonged bacteraemia. The acutely dehydrated, polycythaemic picture does not fit.
E. Intracranial haemorrhage - The thrombocytopenia (90 x10⁹/L) is mild and not usually haemorrhagic at that level. There are no focal deficits, which would be expected with a significant bleed. CVT can cause secondary haemorrhagic transformation, but the primary event here is thrombosis.
Key teaching point
In any child with cyanotic CHD + extreme polycythaemia (PCV >55%) + acute dehydration, CVT must be the first diagnosis considered. The management priorities are:
- Rehydration (reduces viscosity - the most urgent step)
- Neuroimaging (MRI with MR venography is gold standard)
- Anticoagulation (low molecular weight heparin, even in the presence of mild thrombocytopenia, once haemorrhagic transformation is excluded)
- Phlebotomy/venesection if PCV remains dangerously elevated after rehydration
The answer is C - Cerebral Venous Thrombosis.
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