Cerebral Hyperperfusion Syndrome After Surgical Repair of Congenital Supravalvular Aortic Stenosis

Asymmetric cerebral edema presenting with severe neurologic impairment and seizures after cardiac and thoracic interventions

INTRODUCTION

A syndrome of focal neurologic deficits with characteristic imaging features, acute encephalopathy, and seizures after cardiac and thoracic interventions has been previously briefly reported in the literature. In a retrospective observational study, we aim to identify the prevalence and characteristics of this syndrome, in addition to discussing the possible underlying pathophysiology.

METHODS

In a retrospective study, we reviewed records of consecutive adult patients (≥18 years old) who underwent cardiac and thoracic procedures at a single institution between September 2014 to September 2019 and found to have evidence of focal cerebral edema following their procedure. We included and reported clinical course of patients who developed post-operative neurologic dysfunction and underwent magnetic resonance imaging (MRI) showing (1) asymmetric cerebral edema with (2) cortical diffusion restriction and (3) T2 cortical or subcortical hyperintensity and (4) no proximal vascular occlusion.

RESULTS

Three out of 107 patients (2.8%) met our inclusion criteria. These represented one male and two females with age at presentation of 63, 81 and 69, respectively. All patients developed severe neurologic impairment on the same day following their procedure (sternotomy with valve or bypass surgery in 2 patients; esophageal dilatation procedure in 1 patient). All patients underwent MRI of the brain and vessel imaging qualifying our inclusion criteria. Two patients improved neurologically prior to discharge, and one patient expired after family elected to withdraw care.

CONCLUSION

We present a series of cases with a rare syndrome after cardiac and thoracic interventions. Although the exact mechanism of this syndrome remains unclear, we believe it to be related to relative cerebral hyperperfusion and cerebral dysautoregulation following anesthesia and thoracic manipulation. Future studies should focus on understanding the true prevalence and pathophysiology of this syndrome.

Cerebral blood flow, frontal lobe oxygenation and intra-arterial blood pressure during sprint exercise in normoxia and severe acute hypoxia in humans

Cerebral blood flow (CBF) is regulated to secure brain O₂ delivery while simultaneously avoiding hyperperfusion; however, both requisites may conflict during sprint exercise. To determine whether brain O₂ delivery or CBF is prioritized, young men performed sprint exercise in normoxia and hypoxia (P_IO₂ = 73 mmHg). During the sprints, cardiac output increased to ∼22 L min^-1, mean arterial pressure to ∼131 mmHg and peak systolic blood pressure ranged between 200 and 304 mmHg. Middle-cerebral artery velocity (MCAv) increased to peak values (∼16%) after 7.5 s and decreased to pre-exercise values towards the end of the sprint. When the sprints in normoxia were preceded by a reduced P_ETCO₂, CBF and frontal lobe oxygenation decreased in parallel ( r = 0.93, P < 0.01). In hypoxia, MCAv was increased by 25%, due to a 26% greater vascular conductance, despite 4-6 mmHg lower PaCO₂ in hypoxia than normoxia. This vasodilation fully accounted for the 22 % lower CaO₂ in hypoxia, leading to a similar brain O₂ delivery during the sprints regardless of P_IO₂. In conclusion, when a conflict exists between preserving brain O₂ delivery or restraining CBF to avoid potential damage by an elevated perfusion pressure, the priority is given to brain O₂ delivery.