The Effect of Cranial Nerve Stimulation on Swallowing: A Systematic Review.
Michelle G M H Florie, Walmari Pilz, Remco H Dijkman and 4 others
PMID 32410202WHAT IT FOUND
Cranial nerve stimulation cannot be recommended for swallowing problems.
Evidence came only from tiny, low-quality studies; some showed aspiration or worse swallowing during vagal nerve stimulation, while tiny recurrent laryngeal nerve series reported less aspiration.
Key findings
01The review found no high-quality evidence that cranial nerve stimulation treats swallowing problems; all eight studies were rated expert opinion, and they could not be pooled.
02Twenty studies described oropharyngeal dysphagia as an adverse reaction to cranial nerve stimulation, with reported frequencies ranging from 1 to 80%.
03In a five-patient recurrent laryngeal nerve stimulation series, aspiration decreased in four patients, but one stroke patient did not benefit.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The review included only 28 articles, and the eight studies on swallowing effects were all rated level C, expert opinion, so they cannot support a treatment recommendation. The studies were very small, with sample sizes from 2 to 14 people, and none reported statistical analyses. Patient groups and outcomes were heterogeneous, including epilepsy, multiple sclerosis, stroke, cerebral palsy, sleep apnea, and healthy subjects, so results cannot be combined. Many studies did not describe how swallowing was tested, did not report diagnostic protocols, and did not state whether outcomes were long term. The adverse reaction studies often reported dysphagia without onset, severity, duration, or relation to stimulation settings, and frequencies ranged from 1 to 80%. The search may have missed studies because terminology was inconsistent, gray literature was excluded, and publication bias could not be ruled out.
The easy way to misread this
Do not read the reduced aspiration reports as evidence that cranial nerve stimulation works. The studies were tiny, mostly case reports or case series, and rated expert opinion, and some vagal nerve stimulation reports showed worse swallowing.