The BDNF polymorphism Val66Met may be predictive of swallowing improvement post pharyngeal electrical stimulation in dysphagic stroke patients

BACKGROUND: The aim of this study was to explore the effect of brain-derived neurotrophic factor (BDNF) polymorphism rs6265 (Val66Met) in both "natural" and treatment induced recovery of swallowing after dysphagic stroke.

METHODS: Sixteen dysphagic stroke patients that completed a single-blind randomized sham controlled trial of pharyngeal electrical stimulation (PES) within 6 weeks of their stroke (N=38), were genotyped for the BDNF SNP Val66Met (rs6265) from saliva samples. These patients received active or sham PES according to randomized allocation. PES was delivered at a set frequency (5 Hz), intensity (75% of maximal tolerated), and duration (10 minutes) once a day for three consecutive days. Clinical measurements were taken from patients at baseline, 2 weeks and 3 months post entering the study. Changes in swallowing ability based on the dysphagia severity rating scale (DSRS) were compared between active and sham groups and associated with BDNF SNP status.

KEY RESULTS: In the active stimulation group, patients with the Met BDNF allele demonstrated significantly greater improvements in DSRS at 3 months compared to patients homozygous for the Val allele (P=.009). By comparison, there were no significant associations at the 2 week stage in either the active or sham group, or at 3 month in the sham group. Functional scores including the Barthel Index and modified Rankin scale were also unaffected by BDNF status.

CONCLUSIONS & INFERENCES: Our findings suggest an association between BDNF and stimulation induced swallowing recovery. Further work will be required to validate these observations and demonstrate clinical utility in patients.