Objective: To define more clearly the neuropathophysiology of eclampsia utilising single-photon emission computed tomography (SPECT), cerebral computerised tomography (CT) and transcranial Doppler (TCD) ultrasonography.
Design: A prospective study
Setting: The obstetric unit in King Edward VIII Hospital, a large tertiary referral centre in Kwa-Zulu Natal, South Africa.
Participants: Sixty-five women with eclampsia.
Interventions: Imaging and ultrasonographic investigations were performed within 48 hours postpartum. Unenhanced cerebral CT scans were performed in all the women and SPECT scans were performed on 63 women using Technetium-99m-hexamethylpropyleneamineoxime (99mTc-HMPAO) as a tracer of regional cerebral blood flow. Middle cerebral artery blood flow velocity waveforms were measured using 2 MHz pulsed Doppler ultrasound via the transtemporal approach.
Main outcome measures: Abnormalities in SPECT scan, CT scan and TCD ultrasound findings.
Results: SPECT scanning revealed perfusion deficits in the watershed areas in all women, 75% of whom had concomitant deficits in the parieto-occipital areas of the brain. Hypodensities (cerebral oedema) were reported in 38 CT scans (58.5%), with parieto-occipital involvement in 97.4% of cases. Increased flow velocity measurements in the middle and posterior cerebral arteries were recorded in 36 (85.7%) women in whom TCD ultrasound was performed.
Conclusion: The pathophysiological mechanism of eclamptic seizures is primary cerebral vasospasm with resultant ischaemia and cerebral oedema involving mainly the watershed areas and parieto-occipital lobes of the brain. SPECT scanning has been shown to be superior to CT scanning and TCD ultrasonography in detecting neuropathophysiologic alterations in eclampsia. However, each of the three investigative tools provide its own unique information and all three are necessary research techniques to improve our understanding of the neuropathophysiological mechanism of eclamptic seizures.