Late stimulation of the sphenopalatine-ganglion in ischemic rats: Improvement in N-acetyl-aspartate levels and diffusion weighted imaging characteristics as seen by MR

Purpose: To assess, by MR spectroscopy (MRS) and diffusion weighted imaging (DWI), the ability of electrical stimulation of the sphenopalatine ganglion (SPG) to augment stroke recovery in transient middle cerebral artery occluded (t-MCAO) rats, when treatment is started 18 ± 2 h post-occlusion. Materials and Methods: ¹H-MRS imaging (¹H-MRSI) and DWI were used to evaluate ischemic brain tissue after SPG stimulation in rats subjected to 2 h of t-MCAO. Rats were examined by ¹H-MRSI, DWI, and behavioral tests at 16 ± 2 h, 8 days, and 28 days post-MCAO. Results: N-Acetyl-aspartate (NAA) levels of the stimulated and control rats were the same 16 ± 2 h post-MCAO (0.52 ± 0.03, 0.54 ± 0.03). At 28 days post-occlusion, NAA levels were significantly higher in the treated group (0.60 ± 0.04) compared with those of the untreated animals (0.50 ± 0.04; P < 0.05). This effect was more pronounced for regions with low NAA values (0.16 ± 0.03) that changed to 0.32 ± 0.03 (P = 0.04) for the treated group and to 0.10 ± 0.03 (P = 0.20) for the controls. DWI data showed better ischemic tissue condition for the treated rats, but the measured parameters showed only a trend of improvement. The MR results were corroborated by behavioral examinations. Conclusion: Our findings suggest that SPG stimulation may ameliorate MR tissue characteristics following t-MCAO even if treatment is started 18 h post-occlusion.