Evaluating Oral Stimulation as a Treatment for Dysphagia after Stroke
Maxine L. Power, PhD,1 Christopher H. Fraser, MD,2 Anthony Hobson, PhD,2 Salil Singh, MRCP,2
Pippa Tyrrell, MD,3 David A. Nicholson, MD,4 Ian Turnbull, MD,4 David G. Thompson, MD,2 and
Shaheen Hamdy, PhD2
1Department of Rehabilitation and Human Performance Research, University of Salford, Salford, United Kingdom; 2Department of
Gastrointestinal Science, University of Manchester, Manchester, United Kingdom; 3Department of Stroke Medicine, University of
Manchester, Manchester, United Kingdom; and 4Department of Radiology, University of Manchester, Manchester, United Kingdom
Abstract. 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 in-
crease corticobulbar excitability, which in previous
work was correlated with swallowing recovery after
stroke. Our study assessed the effects of oral stimu-
lation 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 pa-
tients (12 male, mean age = 73 ± 12 years). Swal-
lowing 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 aspi-
ration 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.
Key words: Aspiration — Deglutition disorders —
Stroke — Treatment — Deglutition.
Swallowing is initiated by the cerebral cortex and
effected by the brain stem swallowing center [1]. Brain
injury, such as stroke, disrupts the normal physiology
of swallowing, leaving the airway vulnerable to the
entry of food into the lungs (aspiration) [2]. Stroke
affects up to 100,000 people per year in the United
Kingdom and is the third most common cause of
death after myocardial infarction and cancer [3].
Deglutitive aspiration is reported in up to 50% of
patients, with the major complication being pneu-
monia, a likely consequence of bacteria-infected
secretions or ingested food repeatedly transgressing
into the airway [4]. While many patients can experi-
ence some form of swallowing recovery within the
first few weeks after ictus, 40% still develop aspiration
pneumonia that increases the use of artificial feeding,
length of hospital stay, and mortality [5]. Despite the
high incidence of aspiration pneumonia after stroke,
treatment options for accelerating the recovery of
swallowing by improving physiology and reducing
aspiration remain limited. The development of an
evidence-based treatment, which can be performed
Abbreviations: mA = milliamps; FP = faucial pillar;
LCD = laryngeal closure duration; OTT = oral transit time;
PTT = pharyngeal transit time; SRT = swallow response time;
TMS = transcranial magnetic stimulation; UES = upper esoph-
ageal sphincter.
Correspondence to: Maxine L. Power, PhD, Department of Stroke
Medicine, Clinical Sciences Building, Hope Hospital, Salford, M6
8HD, United Kingdom; E-mail: mpower@fs1.ho.man.ac.uk
Dysphagia 2006: 49–55
DOI: 10.1007/s00455-005-9009-0

repeatedly and noninvasively at bedside to reduce
aspiration, is therefore crucially important.
After stroke, mechanical stimulation of the
anterior faucial pillar (FP) has been used to treat
swallowing abnormalities, but its scientific merit re-
mains unproven [6]. This technique, referred to as
thermal stimulation or thermal-tactile stimulation,
involves stroking the base of the anterior FP with an
ice-cold laryngeal mirror in an attempt to evoke
pharyngeal swallowing, requires virtually no equip-
ment, and therefore is easily applied by rehabilitation
staff [7]. However, an optimal protocol for stimulus
intensity and frequency has yet to be established and
clinical application of thermal stimulation is highly
labor intensive [8]. Furthermore, to date no study has
proven that mechanically applied FP stimulation can
improve swallow function or reduce aspiration. This
apparent lack of efficacy can be partly explained by
two significant problems. First, stimulus delivery is
difficult to standardize and is therefore applied in a
variable manner, which may dilute any beneficial ef-
fect. Second, there is a lack of understanding of the
mechanism that may induce change in swallowing
function after stimulation because no study has
looked at the ability of oral stimulation to alter
neurophysiologic processes. A more objective defini-
tion of the stimulation parameters therefore is re-
quired to evaluate any possible benefits from this
technique and determine its cost-benefit ratio.
Recently, peripheral electrical stimulation in
humans has provided some insight into the possible
mechanisms by which interventional therapies may
work. For example, it has been shown that intralu-
minal pharyngeal electrical stimulation can increase
corticobulbar excitability in health and after stroke
[9], a phenomenon referred to as stimulus-induced
cortical plasticity, which in the short-term mirrors the
long-term changes seen in stroke recovery. These
studies have also shown that stimulus-induced corti-
cal changes are correlated with measurable
improvement in swallowing physiology and reduced
aspiration. In a recent study, we also described
stimulus-induced cortical changes in healthy subjects
following electrical stimulation of the FP using a
highly controllable digitally applied electrode [10].
While high-frequency (5 Hz) FP stimulation pro-
duced cortical inhibition and had a deleterious effect
on healthy swallowing, low-frequency (0.2 Hz) stim-
ulation produced late (60 min) increases in cortical
excitability, which were neither advantageous nor
detrimental to normal swallowing. We therefore
postulated that low-frequency FP stimulation, while
not changing swallowing in health, may improve
disrupted swallowing in stroke. Thus, the aims of our
study were to assess the effects of low-frequency FP
stimulation on swallowing function in a series of
aspirating stroke patients.
Materials and Methods
Subjects
Sixteen hemispheric stroke patients, with a diagnosis of dysphagia
(12 male, mean age = 73 years, range = 61–85 years) and admitted
to an acute hospital, consented to participate in the study. All were
studied within two weeks of their stroke (mean = 10 days,
range = 6–13 days). Exclusion criteria included a history of swal-
lowing difficulty, neurologic disease other than stroke, intercurrent
illness or upper gastrointestinal disease, and inability to give in-
formed consent because of cognitive impairment or receptive apha-
sia. Computerized tomography (CT) scans were used to confirm the
lesion. Neurologic disability was assessed at the time of the video-
fluoroscopy study using the modified Barthel Index [11], which
comprises a list of ten items of functional independence and provides
a score ranging from 0 (total disability/dependence) to 100 (full
function/independence). All protocols were presented to and ap-
proved by the Salford and Trafford Local Research Ethics Com-
mittee. All subjects gave written informed consent before study.
Computerized tomography (CT) of the brain was performed
on all patients and the scans were analyzed by a neuroradiologist
who was blinded to the patients
clinical presentation and video-
fluoroscopic swallowing status. Lesions were identified according to
type (ischemic vs. hemorrhagic), side (left or right), and volume.
Volume was calculated using the Alberta Stroke Programme Early
CT Score (ASPECTS), a reproducible grading system designed to
assess early ischemic changes on CT scans [12]. This system involves
analysis of seven discrete areas of the middle cerebral artery (MCA)
and three specific subcortical structures that, when affected by
stroke, are allocated one point each, so that a normal CT scan
would score 0 points. These areas were identified from two standard
CT axial cuts, one at the level of the thalamus and basal ganglia, the
other just rostral to the ganglionic structures. The first axial cut
incorporated the three subcortical structures, the insula, and three
branches of the middle cerebral artery, i.e., M1 anteriorly, M2
medially, andM3 posteriorly.M4,M5, andM6 were identified from
the second axial cut immediately above M1, M2, and M3.
Assessment of Swallowing
Videofluoroscopy was carried out using a Siemens Fluorospot
H
SIRESKOP SX unit (Siemens Aktiengesellschaft Medical Engi-
neering, Erlangen, Germany). X-ray images were acquired in real
time at 30 frames/s using a Videomed DI TV system and were
recorded by digital video at 25 frames/s (Sony DHR 1000, Sony
UK Ltd., Weybridge, Surrey, UK). Data were stored on mini-
digital-video cassette tape (Panasonic UK Ltd., Bracknell, Berk-
shire, UK) and reviewed frame by frame. All subjects were in-
structed to retain the full volume of liquid in the mouth until
commanded to swallow. Images were taken in the lateral view
according to previously described protocols [13], the anatomic
markers for imaging being the lips anteriorly, the cervical spine
posteriorly, the nasopharynx superiorly, and the upper margin of
the thoracic esophagus inferiorly. Total screening time was kept
below 80 s (range = 42–73 s) for each study, giving a radiation
dose of less than 0.3 milli-sieverts (mSv).
50 M.L. Power et al.: Oral Stimulation for Dysphagia Treatment