Brain perfusion SPECT demonstrated brain regions responsible for lower processing speed in patients with diffuse traumatic brain injury

Objectives Diffuse traumatic brain injury (TBI) often causes severe higher brain dysfunction. However, lack of regional abnormality makes it difficult for conventional anatomical imaging to demonstrate cerebral regions which is responsible for the post-traumatic functional disturbances. The purpose of this study was to identify the cerebral regions associated with higher brain dysfunction chronically after diffuse TBI.

Methods The study subjects were retrospectively included from TBI cohort who participated in the rehabilitation program for higher brain dysfunction from September 2008 to September 2013. All underwent brain perfusion SPECT with I-123 iodoamphetamine and MRI for imaging work-up. Higher brain dysfunction was evaluated with Wechsler Adult Intelligence Scale to investigate the following four index scores 1) Verbal Comprehension Index (VCI) 2) Perceptual Reasoning Index (PRI), 3) Working Memory Index (WMI), 4) Processing Speed Index (PSI). The acquired brain perfusion SPECT were specially normalized to the Talairach coordinates and statistically correlated with these scores in voxel-by-voxel manner using 3D-SSP and Neurostat.

Results MR imaging did not show focal brain injury in 21/62 TBI patients to suggest diffuse brain injury. They had moderately impaired PSI (76 ± 17), while the remaining indices showed mild abnormalities (VCI: 90 ± 16, PRI: 90 ± 16, and WMI: 82 ± 17). Statistical correlation found significant positive correlations between PSI and brain perfusion in the posterior cerebral structures (z-score = 2.73 at left precuneus) and cerebellum (z-score = 3.01).

Conclusions Brain perfusion SPECT succeeded to demonstrate the responsibility of posterior cerebral structures and cerebellum for lower processing speed index in patients with diffuse TBI showing higher brain dysfunction.

Research Support Grant-in-Aid for Scientific Research #24591741 & National Mutual Insurance Federation of Agricultural Cooperatives.