facial muscles such as the buccinator , orbicularis oris , and risorius play an important 
 role in the oral phase of swallowing and are also involved in facial expression . however , 
 neurological disorders such as stroke cause paralysis of the opposite sides of the body , 
 thereby affecting the facial muscles1 .
the 
 impairment of the facial muscles in patients with central facial palsy ( cfp ) is typically 
 more pronounced in the lower than in the upper face . as a result , weakened facial muscles 
 cause problems in the oral phase of swallowing , such as decreased mastication and bolus 
 control , oral residue , and drooling , as well as facial expression .
neuromuscular electrical stimulation ( nmes ) provides electrical stimulation over the skin 
 in the anterior throat or facial region .
nmes is effective in muscle strengthening , 
 prevention of muscle atrophy , and neuromuscular re - education2 , 3 .
however , most studies have 
 reported applying it on the swallowing - related muscles located on the front side of the neck 
 in patients with pharyngeal dysphagia to examine the effects on swallowing function4 , 5 . 
 therefore , there is insufficient evidence on the effects of nmes on patients with oral phase 
 dysphagia accompanied by cfp .
the present study aimed to investigate the effects of nmes on 
 the facial muscles and oral phase of swallowing in patients with oral phase dysphagia who 
 have cfp following a stroke .
nine stroke patients with dysphagia ( age , 60.78  4.76  years ; 5 males and 4 females ) were 
 eligible for this study .
the inclusion criteria for participation were as follows : 1 ) oral 
 dysphagia with cfp from a stroke that was confirmed by a videofluoroscopic swallowing study 
 ( vfss ) , 2 ) onset < 3months , and 3 ) a mini - mental state examination score of 24 .
the 
 exclusion criteria were as follows : 1 ) implanted cardiac pacemaker , 2 ) severe communication 
 disorder such as severe aphasia , 3 ) unstable medical condition , and 4 ) skin problems that 
 could affect the electrode placement .
all subjects provided written informed consent before 
 participation according to the ethical standards of the declaration of helsinki .
nmes was performed using the vitalstim ( chattanooga group , hixson , tn , usa ) .
one set of 
 electrodes was placed on the paretic facial region according to the device manufacturer s 
 instructions .
the electrical stimulation unit provided 1 channel of bipolar electrical 
 stimulation at a fixed 80-hz pulse rate and a fixed biphasic pulse duration of 700  s .
the 
 intensity was increased gradually at an interval of 0.5 ma for the experimental group .
the 
 stimulation intensity was increased until subjects felt a grabbing sensation in their facial 
 muscles ; a therapist confirmed the visible muscle contraction .
the stimulation intensity was 
 set differently for each participant , from 9.0 to 14.0 ma ( average , 13.2 ma ) .
subjects 
 received the treatment for 30 minutes / session , 5 sessions / week , for 4 weeks . the iowa oral performance instrument (
iopi medical llc , carnation , wa , usa ) was used to 
 measure maximal cheek strength ( mcs ) and maximal lip strength ( mls ) in all subjects .
the 
 videofluoroscopy dysphagia scale ( vds ) was used to quantify the functional recovery of 
 swallowing .
vds is a functional evaluation scale that comprehensively reflects the overall 
 swallowing function in stroke patients7 , 8 . in this study , 7 subtests of oral stage 

function were analyzed such as lip closure , bolus formation , mastication , apraxia , tongue to 
 palate contact , premature bolus loss , and oral transit time .
the outcomes were analyzed using a statistical software program ( spss version 20 ) , with 
 descriptive statistics presented as mean  standard deviation .
mcs and mls improved following intervention from 14.3  3.4 to 18.4  2.8 kpa and from 10.6 
  2.7 to 13.4  2.7 kpa , respectively .
the oral phase vds score statistically significantly 
 decreased from 27.0  5.0 to 22.2  4.3 points ( table 
 1table 1.test results before and after nmesbefore nmes ( n=9)after nmes ( n=9)mcs ( kpa ) 14.3  3.418.4  2.8*mls ( kpa)10.6  2.713.4  2.7*vds ( points ) 27.0  5.022.2
nmes : neuromuscular electrical stimulation ; mcs : maximal cheek strength ; mls : maximal 
 lip strength ; vds : videofluoroscopy dysphagia scale ) .
nmes : neuromuscular electrical stimulation ; mcs : maximal cheek strength ; mls : maximal 
 lip strength ; vds : videofluoroscopy dysphagia scale
the present study aimed to investigate the effects of nmes on facial muscle strength in 
 patients with oral phase dysphagia who have cfp following a stroke .
the study demonstrated 
 improvement in the strength of the mcs and mls . in the present study ,
the electrodes are 
 placed on the lower part of the face to stimulate the buccal branch of the facial nerve , as 
 well as the trigeminal nerve .
this not only stimulates the nerves , but also stimulates 
 motion via muscle contraction , and the buccal branch of facial nerve controls both mcs and 
 mls .
nmes involves electrical stimulation of the muscles using surface electrodes and leads to 
 muscle contraction by depolarization of nerve fibers .
such continued muscle contraction has 
 a positive influence on muscle activation and can be effective for muscle strengthening , 
 reduction of spasm , atrophy prevention , and retraining2 .
nmes increases recruitment of motor units , which is closely 
 associated with an increase in muscle strength .
the present study 
 showed significant improvement in the oral phase parameters of the vds .
the oral phase 
 parameters of the vds include lip closure , bolus formation , and mastication , for which 
 performance of the facial muscles is important .
facial muscles are involved in mastication 
 of food and in formation of intraoral pressure during the oral phase and play a role in 
 preventing the leaking of food via lip closure9 .
therefore , the present study demonstrated that improvement in the 
 strength of facial muscles contributed to improvement in the oral phase of swallowing .
first , because sample size may have influenced the 
 results , they can not be generalized .
second , because this study was conducted in subacute 
 patients , the effects of natural recovery , considering the rapid nature of neurological 
 recovery , can not be excluded .
third , the absence of follow - up after the end of intervention 
 did not allow for determination of the long - term effects .
 [ purpose ] the aim of this study was to investigate the effect of neuromuscular electrical 
 stimulation on facial muscle strength and oral function in stroke patients with facial 
 palsy . [ subjects and methods ] nine subjects received the electrical stimulation and 
 traditional dysphagia therapy . 
 electrical stimulation was applied to stimulate each 
 subject s facial muscles 30 minutes a day , 5 days a week , for 4 weeks . 
 [ results ] subjects 
 showed significant improvement in cheek and lip strength and oral function after the 
 intervention . [ conclusion ] this study demonstrates that electrical stimulation improves 
 facial muscle strength and oral function in stroke patients with dysphagia . 