Cerebral blood flow changes in rhinogenic subdural empyema and the role ofhyperaemia in brain swelling

Background: Previous studies have demonstrated that rhinogenic subdural emp yema (SDE) generally has a good prognosis. Most patients are admitted with an altered level of consciousness or significant neurological deficit, but eventually have a good outcome. It is well known that intra-operative brain swelling may occur with subdural empyema, Objective: To define cerebral blood flow (CBF) dynamics and determine the r ole of cerebral hyperaemia, if any, in intracranial SDE, Methods: CBF dynamics were assessed in five patients (mean age 13.2 +/- 2.2 years) with unilateral rhinogenic convexity SDE documented on computer tom ography (CT), Regional cortical blood flow (rCBF) was measured using a ther mo-coupled sensor placed on the cortex at the time of surgery. Dynamic CT s cans were performed to assess cerebral blood volume (CBV quantitatively, wh ile transcranial Doppler ultrasonography (TCD) was used to measure cerebral blood flow velocities (CBF velocities) both pre- and post-operatively for 21 days. The opposite 'normal' hemisphere served as a control for each pati ent. Results: Post-operative rCBF and CBF velocities in the pathological hemisph ere progressively increased to plateau at 96 hours. Cerebral blood volume w as increased bilaterally, but to a greater extent in the pathological hemis phere and more so in grey than white matter. These haemodynamic changes, th ough clinically significant did not reach statistical significance (p>0.05) , Conclusion: Our results suggest that the accompanying brain swelling in rhi nogenic SDE is a complex event, with reactive cerebral hyperaemia possibly playing neuroprotective role. Furthermore, unilateral convexity empyema cau ses bilateral cerebral haemodynamic changes. Future studies are necessary t o define the aetiology of brain swelling in intracranial SDE.