Predictors of hippocampal atrophy in critically ill patients

Abstract

Background and purpose: Hippocampal atrophy is presumably one morphological sign of critical illness encephalopathy; however, predictors have not yet been determined.

Methods: The data for this report derived from patients treated at the intensive care units (ICUs) of the University Hospital in Bonn in the years 2004-2006. These patients underwent structural magnetic resonance imaging 6-24 months after discharge. Volumes (intracranial, whole brain, white matter, grey matter, cerebral spinal fluid, bilateral hippocampus) were compared with healthy controls. Pro-inflammatory parameters and ICU scoring systems were explored in conjunction with brain volumes. Cut-scores were defined to differentiate patients with high from those with low inflammatory response.

Results: Hippocampal and white matter volume were reduced in critically ill patients compared with healthy controls. Procalcitonin showed a very strong correlation (r = -0.903, P = 0.01) and interleukin-6 a moderate correlation (r = -0.538, P = 0.031) with hippocampal volume, but not with other brain volumes. C-reactive protein was linked to grey matter volume. There was no correlation with systemic inflammatory response syndrome criteria (body temperature, heart rate, respiratory rate, white blood cell count) or for hippocampal or whole brain volume. Furthermore, parameters representing severity of disease (APACHE II score, SOFA score, duration of stay and duration of mechanical ventilation) were not associated with hippocampal or other brain volumes.

Conclusions: This analysis suggests that high levels of procalcitonin and interleukin-6 in the blood serum of critically ill patients are associated with a high likelihood of hippocampal atrophy irrespective of the severity of disease measured by ICU scoring systems and other inflammatory parameters.

Keywords: critical illness; hippocampus; inflammation; neurodegenerative disorders; structural MRI.