The sudden onset of hemiplegia in the child with a brief prodrome, preserved consciousness and no features of raised intracranial tension point towards arterial thrombosis as the underlying mechanism. In venous thrombosis on the other hand a prodromal phase is usually absent,sensorium is altered and features of raised intracranial tension may be present. Intracranial hemorrhage presents with an abrupt onset of symptoms with rapid progression usually to termination, associated loss of c onsciousness and features of raised intracranial pressure which is not the case here. Embolism too can be excluded as it also causes transient loss of consciousness and there appears to be no source of embolism. Presence of dense hemiplegia (power equal in both upper and lower limbs) with preserved consciousness suggests a lesion in the internal capsule. A cortical lesion that causes hemiparesis would be quite extensive and would lead to seizures besides also causing alteration in sensorium and seems unlikely. The cause of arterial thrombosis could be vasculitis secondary to a viral infection.
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