Low pre-existing gray matter volume in the medial temporal lobe and white matter lesions are associated with postoperative cognitive dysfunction after cardiac surgery.
OBJECTIVE
Postoperative cognitive dysfunction (POCD) is recognized as a complication in the elderly after cardiac surgery. Imaging of the brain provides evidence of neurodegeneration in elderly patients; however, abnormalities in brain structure and their relation to POCD are uncertain. This pilot study investigated whether loss of gray matter in the bilateral medial temporal lobe (MTL), seen in preoperative MRI, was associated with POCD.


METHODS
Data were collected prospectively on 28 elderly patients scheduled for elective cardiac surgery. MRI of the brains of all patients were assessed for prior cerebral infarctions, and carotid and intracranial arterial stenosis. Patients also completed six neuropsychological tests of memory, attention and executive function before and after surgery. POCD was defined as an individual decrease in more than two tests of at least 1 standard deviation from the group baseline mean for that test. The degree of gray matter loss in the MTL of each patient was calculated using voxel-based morphometry with three-dimensional, T1-weighted MRI. This represented the degree of gray matter change as a Z score.


RESULTS
Postoperative cognitive dysfunction was identified in 8 of the 28 patients (29%). Patients with POCD had significantly more white matter lesions on MRI, and greater loss of gray matter in the bilateral MTL (average Z score 2.0±0.9) than patients without POCD. An analysis by stepwise logistic regression identified gray matter loss in the MTL and cerebral infarctions on MRI as independent predictors of POCD.


CONCLUSIONS
These preliminary findings suggested that reduced gray matter in the bilateral MTL and white matter lesions existed in brains of elderly cardiac surgery patients who experienced POCD. Additional studies with larger sample sizes are needed to confirm these findings.
Department of Anesthesiology, Graduate School of Medical Sciences, Kumamoto University, Kumamoto, Japan ; Department of Anesthesiology, Kumamoto Chuo Hospital, Kumamoto, Japan.
Kengo
K
Maekawa
Department of Anesthesiology, Kumamoto Chuo Hospital, Kumamoto, Japan.
Tomoko
T
Baba
Department of Anesthesiology, Kumamoto Chuo Hospital, Kumamoto, Japan.
Sumi
S
Otomo
Department of Radiology, Kumamoto Chuo Hospital, Kumamoto, Japan.
Shoji
S
Morishita
Department of Cardiovascular Surgery, Kumamoto Chuo Hospital, Kumamoto, Japan.
Nobushige
N
Tamura
D000368:Aged; D000369:Aged, 80 and over; D006348:Cardiac Surgical Procedures / Q000009:adverse effects*; D003072:Cognition Disorders / Q000209:etiology / Q000473:pathology*; D005260:Female; D006801:Humans; D007564:Japan; D056784:Leukoencephalopathies / Q000209:etiology / Q000473:pathology*; D016015:Logistic Models; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D011183:Postoperative Complications / Q000473:pathology*; D011446:Prospective Studies; D013702:Temporal Lobe / Q000473:pathology*