Characterizing the mechanisms of central and peripheral forms of neurostimulation in chronic dysphagic stroke patients.

BACKGROUND: Swallowing problems following stroke may result in increased risk of aspiration pneumonia, malnutrition, and dehydration. OBJECTIVE/HYPOTHESIS: Our hypothesis was that three neurostimulation techniques would produce beneficial effects on chronic dysphagia following stroke through a common brain mechanism that would predict behavioral response. METHODS: In 18 dysphagic stroke patients (mean age: 66 ± 3 years, 3 female, time-post-stroke: 63 ± 15 weeks [±SD]), pharyngeal electromyographic responses were recorded after single-pulse transcranial magnetic stimulation (TMS) over the pharyngeal motor cortex, to measure corticobulbar excitability before, immediately, and 30 min, after real and sham applications of neurostimulation. Patients were randomized to a single session of either: pharyngeal electrical stimulation (PES), paired associative stimulation (PAS) or repetitive TMS (rTMS). Penetration-aspiration scores and bolus transfer timings were assessed before and after both real and sham interventions using videofluoroscopy. RESULTS: Corticobulbar excitability of pharyngeal motor cortex was beneficially modulated by PES, PAS and to a lesser extent by rTMS, with functionally relevant changes in the unaffected hemisphere. Following combining the results of real neurostimulation, an overall increase in corticobulbar excitability in the unaffected hemisphere (P = .005, F1,17 = 10.6, ANOVA) with an associated 15% reduction in aspiration (P = .005, z = -2.79) was observed compared to sham. CONCLUSIONS: In this mechanistic study, an increase in corticobulbar excitability the unaffected projection was correlated with the improvement in swallowing safety (P = .001, rho = -.732), but modality-specific differences were observed. Paradigms providing peripheral input favored change in neurophysiological and behavioral outcome measures in chronic dysphagia patients. Further larger cohort studies of neurostimulation in chronic dysphagic stroke are imperative.

Adjunctive functional pharyngeal electrical stimulation reverses swallowing disability after brain lesions.

BACKGROUND & AIMS: Oropharyngeal dysphagia is an important disability that occurs after stroke; it contributes to aspiration pneumonia and death, and current modalities for rehabilitation of dysphagia have uncertain efficacy. We therefore examined the role of pharyngeal electrical stimulation (PES) in expediting human swallowing recovery after experimental (virtual) and actual (stroke) brain lesions. METHODS: First, healthy subjects (n = 13) were given 1-Hz repetitive transcranial magnetic stimulation to induce a unilateral virtual lesion in pharyngeal motor cortex followed by active or sham (control) PES. Motor-evoked potentials and swallow accuracy were recorded before and after the lesion to assess PES response. Thereafter, 50 acute dysphagic stroke patients underwent either a dose-response study, to determine optimal parameters for PES (n = 22), or were assigned randomly to groups given either active or sham (control) PES (n = 28). The primary end point was the reduction of airway aspiration at 2 weeks postintervention. RESULTS: In contrast to sham PES, active PES reversed the cortical suppression induced by the virtual lesion (F(7,70) = 2.7; P = .015) and was associated with improvement in swallowing behavior (F(3,42) = 5; P = .02). After stroke, 1 PES treatment each day (U = 8.0; P = .043) for 3 days (U = 10.0) produced improved airway protection compared with controls (P = .038). Active PES also reduced aspiration (U = 54.0; P = .049), improved feeding status (U = 58.0; P = .040), and resulted in a shorter time to hospital discharge (Mantel-Cox log-rank test, P = 0.038). CONCLUSIONS: This pilot study of PES confirms that it is a safe neurostimulation intervention that reverses swallowing disability after virtual lesion or stroke.

Evaluating oral stimulation as a treatment for dysphagia after stroke.

Deglutitive aspiration is common after stroke and can have devastating consequences. While the application of oral sensory stimulation as a treatment for dysphagia remains controversial, data from our laboratory have suggested that it may increase corticobulbar excitability, which in previous work was correlated with swallowing recovery after stroke. Our study assessed the effects of oral stimulation at the faucial pillar on measures of swallowing and aspiration in patients with dysphagic stroke. Swallowing was assessed before and 60 min after 0.2-Hz electrical or sham stimulation in 16 stroke patients (12 male, mean age = 73 +/- 12 years). Swallowing measures included laryngeal closure (initiation and duration) and pharyngeal transit time, taken from digitally acquired videofluoroscopy. Aspiration severity was assessed using a validated penetration-aspiration scale. Preintervention, the initiation of laryngeal closure, was delayed in both groups, occurring 0.66 +/- 0.17 s after the bolus arrived at the hypopharynx. The larynx was closed for 0.79 +/- 0.07 s and pharyngeal transit time was 0.94 +/- 0.06 s. Baseline swallowing measures and aspiration severity were similar between groups (stimulation: 24.9 +/- 3.01; sham: 24.9 +/- 3.3, p = 0.2). Compared with baseline, no change was observed in the speed of laryngeal elevation, pharyngeal transit time, or aspiration severity within subjects or between groups for either active or sham stimulation. Our study found no evidence for functional change in swallow physiology after faucial pillar stimulation in dysphagic stroke. Therefore, with the parameters used in this study, oral stimulation does not offer an effective treatment for poststroke patients.