A prospective, randomized, placebo-controlled evaluation of corticoneuronal response to intrathecal BDNF therapy in ALS using magnetic resonance spectroscopy: feasibility and results

During the multicenter, phase III trial of intrathecal BDNF in ALS, we evaluated the neuronal marker N-acetylaspartate (NAA) as a surrogate marker of therapeutic efficacy using proton magnetic resonance spectroscopic imaging (MRSI) in a prospective and blinded manner. Selected subjects tolerated the study well without pump malfunction. The NAA to creatine (Cr) intensity ratio (NAA/Cr) was measured in the precentral and postcentral gyri, the superior parietal lobule, the supplementary motor area, and the premotor cortex. After 4.5+/-0.6 weeks treatment, NAA/Cr did not change significantly in any of the regions in the BDNF-treated group (n=5) compared to the placebo group (n=6). The lack of change in NAA correlated with the lack of clinical efficacy and supports the validity of NAA/Cr as a surrogate in this setting. MRSI is a feasible and safe method to evaluate intrathecal therapies in ALS.