Prefrontal N-acetylaspartate and poststroke recovery: a longitudinal proton spectroscopy study.

BACKGROUND AND PURPOSE Functional imaging studies suggest that poststroke recovery is related to the reorganization in both contralesional and ipsilesional prefrontal cortex. Little is known, however, about how longitudinal metabolic changes in prefrontal regions relate to the improvement after stroke. We sought to determine whether poststroke recovery is associated with changes in N-acetylaspartate/creatine (NAA/Cr) ratio within contralesional prefrontal regions. MATERIALS AND METHODS Twenty-seven patients with a first ischemic stroke located outside the frontal lobes were included. Proton MR spectroscopy ((1)H-MRS) was performed on a 1.5T scanner. Point-resolved spectroscopy sequence (PRESS) was used. NAA/Cr was measured both in ipsilesional and contralesional prefrontal regions in early (14 +/- 6 days after stroke) and chronic phases of the disease (110 +/- 30 days after). Patients' neurologic status was assessed using Scandinavian Stroke Scale (SSS) at discharge from the stroke unit and during second (1)H-MRS examination. RESULTS Subjects showing increased contralesional NAA/Cr from first to follow-up examination improved significantly more on the SSS than patients not showing this increase. Analysis was performed while correcting for change in NAA/Cr levels in the ipsilesional hemisphere. For the whole group, the change in contralesional NAA/Cr was significantly correlated to the change in SSS scores (r = 0.40, P = .03). Change in the ipsilesional NAA/Cr measures did not correlate with the change in SSS scores. CONCLUSION Poststroke recovery was related to the increase in contralesional prefrontal NAA/Cr. This association may reflect recovery mechanisms involving the nonaffected hemisphere. Further assessment of these regions may provide information about mechanisms contributing to neurologic improvement.