International Journal of Otolaryngology and Head & Neck Surgery, 2013, 2, 253-258
Published Online November 2013 (http://www.scirp.org/journal/ijohns)
Open Access IJOHNS
Botulinum Toxin A in the Treatment of Oropharyngeal or
Caroline Beutner1, Katharina Bartsch2, Harald Schwörer3, Rainer Laskawi2, Saskia Rohrbach4
1Department of Otorhinolaryngology, Duesseldorf University Hospital, Duesseldorf, Germany
2Department of Otorhinolaryngology, Georg-August-University Hospital Göttingen, Göttingen, Germany
3Department of Gastroenterology an d Endocrinology, Georg-August-University Hospital Göttingen, Göttingen, Germany
4Department of Audiology and Phoniatrics, Charité, Berlin, Germany
Received July 22, 2013; revised August 25, 2013; accepted September 10, 2013
Copyright © 2013 Caroline Beutner et al. This is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Objectives: In this retrospective analysis, we explored the effect of botulinum toxin A (BTA) injection to treat oro-
pharyngeal dysphagia or esophageal dysfunction caused by diseases of the upper (UES) and lower (LES) esophageal
sphincter. Methods: In total, 48 patients (17 patients with UES diso rders, and 31 patients with LES dysfunction; mean
age 64 years) wer e treated between 1996 and 2007 in our hospital. Comorbid diseases as well as maintenance medica-
tion were documented to evaluate the overall health status of our patients. The mean duration of symptoms, the number
of pre-treatments and the specification of dysphagia were considered. Results: One month after injection, the response
rates were 73.3% (UES group) and 76.6% (LES group). Most patients in the UES group received 30 - 40 units BTA
(Botox®) whereas most patients in the LES group were treated with 100 units BTA. In cases of re-injection, 50% of
patients in the UES group experienced an escalation of dosage (up to 75 units), whereas the other 50% received the
same dosage. The dosages in the LES group were mostly kept constant. Conclusion: Comparing the two groups with
esophageal dysfunction of fundamentally different etiologies (UES/LES), a discrepancy in the level of symptom relief,
onset and a longer cessation of clinical benefit were observed in the LES group. In this analysis, we were able to show
that injection of BTA is an effective and safe treatment for disorders of the UES and LES.
Keywords: Botulinum Toxin; Dysphagia; Upper Esophageal Sphincter; Lower Esophageal Sphincter
Because of the complex course of function during swal-
lowing, the underlying cause of esophageal dysphagia is
highly variable. Neuromuscular diseases are especially
common. While the treatment of mild disorders of the
upper esophageal sphincter (UES) is manageable by
swallowing exercises and modification of nutrition, se-
vere disorders in this area often require surgical myo-
tomy of the cricopharyngeal muscle. Disorders of the
lower esophageal sphincter (LES), especially achalasia,
can be treated with pharmacological agents, such as ni-
trates, calcium channel blockers, anticholinergic agents
and beta-adrenergic agonists, but frequently do not pro-
vide satisfactory relief of symptoms 1,2. Pneumatic
dilatation is considered as the treatment of choice, espe-
cially in the primary management of achalasia. The
standard for surgical management is laparoscopic Heller
myotomy, although improvements in long-term remis-
sion rates compared to the open approach are still lack ing
1,3. Since none of these methods yield universally sat-
isfactory results for either UES or LES diseases, an al-
ternative endoscopic treatment option is proposed. The
intramuscular injection of botulinum toxin A (BTA),
which is produced by the bacterium Clostridium botu-
linum, offers a viable alternative treatment. BTA blocks
the cholinergic neuromuscular innervation of intra- and
extrafusal muscle fibers, innervation of striated and
smooth muscle as well as the cholinergic junctio ns of the
autonomous nervous system 4. Earlier studies reported
on the use of BTA in LES- 5,6 and UES 7 -diseases.
The purpose of this study is to demonstrate the efficacy
of BTA injection as a non-surgical therapeutic option for
oropharyngeal or esophageal dysphagia caused by dys-
function of the UES or LES. Furthermore, recommenda-
tions for the injection technique and the treatment dosage
are stated and any side effects are noted.
C. BEUTNER ET AL.
2. Materials and Methods
Between 1996 and 2007, 48 patients (female n = 15,
male n = 33, mean age 64 years, range: 25 - 85 years)
with UES or LES dysfunctions were treated at the Uni-
versity Hospital of Goettingen, Germany. Based on their
symptoms, medical history and on an interdisciplinary
review of the diagnostic results (baseline: flexible laryn-
goscopy and esophagram in patients presumably having
UES dysfunctions; gastrointestinal endoscopy (see Fig-
ure 1) and manometry in patients presumably having
LES dysfunctions), patients were divided into two groups:
UES or LES. MRI, CT-scan or X-ray of the chest were
performed in patients with a history of malignant tumors
or if malignancy was suspected. For baseline characteris-
tics, see Table 1.
Pre-treatment included pneumatic dilatation, pharma-
cological or surgical procedures and showed unsatisfac-
tory results (for details see Table 2). Exclusion criteria
for the treatment with BTA were pregnancy, nursing,
under 18 years of age, malignancies and contraindica-
tions for the treatment with BTA or for general anesthe-
sia. A clinical assessment, describing the severity and fre-
Figure 1. Classical finding from esophago-gastrointestinal
endoscopy of a patient suffering from ac halasia: prestenotic
dilatation and retention of chime.
Table 1. Baseline characteristics of patients with dysphagia
caused by disorders of the UES or LES.
disease DystoniaTumor Unknown
(n) 17 7 5 3 2 3148
[years] 25 59 25 42 55 2525
[years] 80 80 75 74 59 8585
quency of the symptoms, was performed 6 months later.
For precise localization, the injection into the UES was
performed under general anesthesia and direct vision
using microscopic controlled endoscopy with a rigid en-
doscope. After having localized the UES (Figure 2), 30 -
75 units of botulinum toxin A (BTA, Botox®, Allergan
Inc., Irvin, CA, USA, freshly reconstituted with 0.9%
sterile saline to a final concentration of 2.5 U BTA/0.1ml)
were injected into both the lateral, ventral-medial and
dorsal-medial part of the cricopharyngeal muscle. An
adjusted injection set consisting of a Kleinsasser-Hecht
forceps holding a butterfly-needle was used for the inj ec-
tion, as shown in Figure 3.
Table 2. Pre-treatments.
Previous therapy UES
(n = 17) LES
(n = 31)Total
(n = 48)
Pharmacologic treatment 10 12 22
Pneumatic dilatation 1 10 11
Percutaneous endo scopic gastrostomy 10 0 10
Tracheostomy 7 0 7
Logopedics 8 0 8
Botulinum toxin inj e c t i o n s 3 1 4
Surgical myotomy 0 1 1
Surgery of the glottis 1 0 1
Figure 2. Direct endoscopic exposure of the UES for a safe
BTA application into both the lateral, ventral-medial and
dorsal-medial part of the cricopharyngeal muscle.
Figure 3. Instruments for transoral BTA injection: adjusted
injection set consisting of a Kleinsasser-Hecht forceps hold-
ing a butterfly-needle.
Open Access IJOHNS
C. BEUTNER ET AL. 255
For treatment of the LES, patients were first sedated
using midazolam and propofol, placed under cardiovas-
cular monitoring and positioned on their left side; 80 -
100 units of BTA (Botox®) were diluted in 0.9% sterile
saline to a final concentration of 2 U BTA/0.1ml. After
having visualized the sphincteric rosette (Figure 4), 20
units of BTA were injected into each quadrant of the
LES and 10 units at each point between quadrants two/
three and four/one (six points) through a 7 mm sclero-
therapy needle. Responders to BTA were defined as pa-
tients with symptom relief for at least 2 months. Patients
who failed to respond after a single treatment were clas-
sified as non-responders without testing for neutralizing
antibodies against BTA. These patients were free to elect
any alternative treatment options.
To evaluate the overall health status of our patients,
we asked them about attendant disorders and any main-
tenance medications. In addition to the dysphagia, 41.2%
of the UES group had a cerebral infarction or brain hem-
orrhage; 25.8% of both groups had a tumor disease and
22.6% were suffering from reflux esophagitis or gastritis.
Maintenance medication in all patients included frequent
use of proton pump inhibitors (PPI, 58.5% in the UES
group, 41.9% in the LES group) and anti-neuromuscular
or antispasmodic agents (41.2% in the UES group);
25.8% of patients in the LES group used calcium channel
blockers, 12.9% of patients needed prokinetics and 12.0 %
used HMG-CoA-reductase enzyme inhibitors.
In patients with severe dysphagia, nutrition was en-
sured by a permanent endoscopic gastrostomy (PEG).
Patients unable to swa llo w so lids were dependent on high -
caloric fluid alimentation. In cases of severe achalasia,
swallowing liquids was only possible in combination wit h
special maneuvers or positions. In the UES group, be-
sides dysphagia, the primary symptoms were aspiration
Figure 4. Endoscopic view of the sphincteric rosette of the
LES for BTA injections into each quadrant and each point
between quadr ant two/three and four/one (six points).
(n = 10) as shown in Figure 5, dysarthria (n = 8) and
weight loss (n = 7). In the LES group, patients repo rted a
loss of weight (n = 14), postprandial vomiting (n = 11),
regurgitation and retrosternal pain (n = 9) in addition to
the dysphagia. For duration of symptoms before the
treatment see Table 3.
3. Results and Analysis
The 48 patients received a total of 101 injections of BTA
into the LES or UES.
In the UES group, (n = 17), the majority (52.9%) re-
ceived a single BTA injection, 23.5% were treated twice,
17.6% received three injections and one patient received
four injections. In those receiving more than one injec-
tion the dosage was accelerated in 4 cases and remained
unchanged in 4 cases. The initial dosage ranged from 30
to 75 U. 29.4% received 30 U, 53% received 40 - 50 U,
11.8% got 51 - 65 U and 5.9% (one patient) received 75
U. The majority of patients in this group who required a
second injection (17.6%) were treated after an interval of
at least 150 days.
In the LES group, (n = 31), 38.7% received one injec-
Figure 5. Videofluoroscopy in one representative patient in
the UES group, suffering from hypertrophy of the crico-
pharyngeal muscle before and after treatment with botu-
linum toxin A. The prestenotic pooling of contrast medium
and laryngeal penetration with aspiration is shown in the
left image (arrowhead). After injection of BTA, a normal-
ized UES function without retention or aspiration is ob-
served in this patient (right image).
Table 3. Duration of symptoms.
Duration of symptoms [months]UES
(n = 17) LES
(n = 31)*Total
(n = 48)*
0 - 3 5 2 7
4 - 6 4 1 5
7 - 12 0 4 4
13 - 24 2 2 4
>24 6 21 27
Median 6.5 >24 >24
*One patient without inform a tion about the dura tion of sym ptoms.
Open Access IJOHNS
C. BEUTNER ET AL.
tion, 19.4% were treated twice, 22.6% had three injec-
tions, and 35% received four or more injections. In those
receiving more than one injection 16 patients had no
change in dosage and in 3 patients the dosage increased.
The initial dosage ranged from 40 to 100 U. 81% re-
ceived 100 U. This dosage remained constant in the fol-
lowing four treatments. 3% were injected with 40 - 50 U
and in 16%, due to disconnection of the needle, there was
no clear information on the actual dosage. Most patients
were retreated after an interval of over 150 days.
In 75.5% of all patients (combined LES and UES), a
good improvement was obtained (responders), while
24.4% of all patients showed no relief of symptoms after
1 month. In 3 patients, we received no information about
the therapeutic effect. After 1 month, the respon se rate in
the LES group was higher (76.6%) than in the UES
group (73.3%, see Table 4). The effect was noticed after
0 - 2 days in 43.8% of all patients, while 14.6% of all
patients showed an effect between day 3 and 8.
Interestingly, in some patients without subjectively
reported symptom relief after the treatment, the objective
assessment including esophageal manometry, video-
fluoroscopy and esophagogastroscopy showed an im-
provement and did not correlate with the persisting com-
plaints of the patients. No severe side effects occurred. In
all patients, mild side effects such as reflux (n = 3), pyro-
sis (n = 3), esophagitis/gastritis (n = 1) and retrosternal
pain (n = 1) were manageable by modification of the
dosage after the first interval.
The aim of this analysis was to describe the outcome
parameters for BTA-based therapy for patients suffering
from oropharyngeal or esophageal dysphagia, with re-
gard to the different etiologies of the two entities. Our
objective was to evaluate the clinical efficacy, to deter-
mine a recommended technique and treatment dosage,
and to report on the resultant side effects. The response
rates in the UES group (73.3%) were high compared to
an overview of reported studies between 1994 and 2004,
8 describing a success rate varying from 20% to 100%
9. This may be caused by the high initial doses we in-
jected, discussed below, compared to those in the litera-
The number of responders in our LES group (76.6%)
was comparable to those described in the literature. An-
nese and Bassotti compared 12 of the largest studies (in-
volving at least 30 patients suffering from achalasia) be-
tween 1996 and 2004 having response rates of 75% -
93% after 1 month, 10 of whom 95% had not been
treated before 11. Even though Storr et al. claim that
the same benefit from BTA injections could be expected
in untreated or pre-treated patients, 12 a possible ex-
planation for the slightly lower outcome in our group
Table 4. Onset of the effect.
Onset of the effect UES
(n = 17) LES
(n = 31) Total
(n = 48)
0 - 2 4 17 21
3 - 5 1 4 5
6 - 8 2 0 2
>8 2 0 2
Onset unknown 2 2 4
No informat i o n a bout the e f f ect2 1 3
No effect 4 7 11
could be the high number of pre-treated patients. A lower
muscle connective tissue ratio, found in non-responders,
13 could be caused by previous treatments.
The response rates for all patients, irrespective of
group, showed no dependence on duration of symptoms
before the first treatment. There was a trend towards bet-
ter outcome in younger patients 14-16 and additional
earlier onset of effect in patients with disorders of the
LES, especially in patients suffering from severe acha-
lasia, in contrast to patients with UES disorders. This
supports the results of a previou s study 17.
The number of patients in the LES group, wh o showed
an effect that lasted longer than a minimum of 5 months
after the fir st injection , was hig her th an in the U ES group
(29% versus 12%). The reason for these variable dura-
tions of effect after BTA injections, also observed in dis-
orders of the autonomic nervous system, remains unclear
18. The discrepancy of symptom relief between the
LES group (smooth muscle) compared to the UES group
(skeletal muscle) may be caused by the different neuro-
transmitters at the neuromuscular junctions. A study by
Torbey et al. 19 showed a relaxation of smooth muscles
in rats in both cholinergic and peptinergic neurons
through botulinum toxin injections. In several studies, an
earlier onset and a longer cessation of improvement
5,6,14 suggest a higher sensitivity of the smooth mus-
cle to BTA compared to injections in striated muscles.
Different predictors of outcome are controversially dis-
cussed. Pasricha et al. assessed the decrease in LES
pressure as a good predictive factor, 6 whereas others
described a correlation of esophageal clearance with
symptom improvement 14. The best predictors of suc-
cessful outcome after BTA injections into the UES seem
to be a good remaining swallowing function, a proven
cricopharyngeal muscle hypertonicity 13 or isolated
cricopharyngeal muscle pathology 20,21. Evaluation of
outcome is still a challenge because of the discrepancy
between symptomatic and objective measures of im-
The dosages of BTA injected into th e UES or LES re-
Open Access IJOHNS
C. BEUTNER ET AL. 257
ported in the literature are similar to our initial dosages.
Dosages from 10 - 100 units (all dosages transformed to
Botox®) with different injections techniques (transoral,
percuateneous with or without electromyography, per-
cuataneous CT-guided, with rigid or flexible endoscopes
or in open techniqu e during vocal cord lateralization) are
repor ted concerning the UES 7,9,20-24.
We decided to inject dosages of BTA ranging from 30
to 75 U into the UES, with exact localization under gen-
eral anesthesia, based upon evaluation of the results from
dose-range studies. These studies showed a dosage-re-
lated effect and relief of symptoms 25,26 without ob-
servation of severe complications 8. Injections of com-
parable high dosages are usually administered under
general anesthesia and direct endoscopic view to ensure
safe injection and correct localization of the needle to
minimize the risk of complications. The dosages of BTA
injection in patients with disorders of the LES, especially
of achalasia, vary from 80 U 6,14 to 200 U 1,11.
Since the mean dosage used by most centers was about
100 U BTA, in the majority of our patients, we chose to
inject this amount. There was no clear dose/effect rela-
tionship described in the first injection (investigation of
118 patients suffering from achalasia) 11. To inhibit the
complete nerve regeneration in the smooth muscle,
which is responsible for the recurrence of symptoms, a
timely re-injection might be useful. Re-injection with
100 U BTA into the LES is recommended after 30 days
11. Nevertheless, we have to consider that short re-in-
jection intervals and the amount of toxin might risk a
receptor blockage by antibodies. The role of antibodies
as a result of autoimmune response possibly leading to
variable duration of the effect has to be clarified.
The number of complications reported after BTA in-
jection into the UES or LES is low. Uncontrolled diffu-
sion into the hypopharyngeal musculature 22, transient
chest pain (also occurring in the placebo group) 14,
unilateral vocal fold paresis 9, abnormal acid reflux
27 and aspiration with death after delayed medical in-
tervention 13 have been described. Mediastinitis and
ulceration of the esophagus without perforation after
BTA injection are rare complications 28. In our patients,
no severe side effects or systemic effects were noted.
The necessity for BTA re-injection, because of its re-
versible effect, seems disadvantageous, but no additional
adverse effects have been described after long-term ap-
plication 4. Likewise, the indication for revision in
surgery must also be considered. The predictive value of
outcome of BTA injection into the UES compared to a
myotomy is still controversially discussed 7,20.
While evaluating the different treatment methods
available for a patient’s relief of dysfunctions of the UES
or LES causing dysphagia, numerous factors must be
taken into account. These include the endoscopist’s or
surgeon’s experience 13, the risk of complications in
surgery, the patient’s age, coexisting diseases 29, the
overall morbidity of the patient, long-term results and
In conclusion, comparing the two groups of esophag-
eal dysfunction with fundamentally different etiologies
(UES/LES), intramuscular BTA injections represent a
safe and feasible technique with a lack of significant side
effects in both groups, especially for older patients with
co-morbid illness. Symptom relief, onset and duration of
clinical benefit were better in dysfunctions of the LES,
explainable by the history of malignant tumor resection
in the UES group with scarred tissue and the presumably
better effect of BTA in smooth muscles. Further studies
are needed providing objective data that correlate with
The pharmacological and surgical treatment of severe
oropharyngeal or esophageal dysphagia often gives un-
satisfactory results. This paper reports an alternative
treatment option, using endoscopic applied intramuscular
injection of Botulinum toxin A in the upper or lower
esophageal sphincter. 48 treated patients suffering from
oropharyngeal or esophageal dysphagia confirmed the
clinical efficacy of this method. The recommended dos-
age and technique of injection showed no significant side
 J. E. Leyden, A. C. Moss and P. Mac Mathuna, “Endo-
scopic Pneumatic Dilatation versus Botulinum Toxin In-
jection in the Management of Primary Achalasia,” Coch-
rane Database of Systematic Reviews, Vol. 18, No. 4,
2006, Article ID: CD005046.
 Z. H. Wen, E. Gardener and Y. P. Wang, “Nitrates for
Achalasia,” Cochrane Database of Systematic Reviews,
2004, No. 1, Article ID: CD002299.
 N. Pehlivanov and P. J. Pasricha, “Achalasia: Botox,
Dilatation or Laparoscopic Surgery in 2006,” Neurogas-
troenterology and Motility, Vol. 18, No. 9, 2006, pp. 799-
 D. Dressler, “Pharmacological Aspects of Therapeutic
Botulinum Toxin Preparations,” Nervenarzt, Vol. 77, No.
8, 2006, pp. 912-921.
 P. J. Pasricha, W. J. Ravich, T. R. Hendrix, S. Sostre, B.
Jones and A. N. Kallo, “Intrasphincteric Botulinum Toxin
for the Treatment of Achalasia,” New England Journal of
Medicine, Vol. 322, No. 12, 1995, pp. 774-778.
 P. J. Pasricha, R. Rai, W. J. Ravich, T. R. Hendrix and A.
N. Kalloo, “Botulinum Toxin for Achalasia: Long-Term
Open Access IJOHNS
C. BEUTNER ET AL.
Open Access IJOHNS
Outcome and Predictors of Response,” Gastroenterology,
Vol. 110, No. 5, 1996, pp. 1410-1415.
 I. Schneider, W. Thumfart and H. E. Eckel, “Treatment of
Dysfunction of the Cricopharyngeal Muscle with Bot u li n u m
Toxin. Introduction of a New, Non-Invasive Method,”
Annals of Otology, Rhinology, and Laryngology, Vol. 103,
1994, pp. 31-35.
 M. B. J. Moermann and B. J. Mieke, “Cricopharyngeal
Botox Injection: Indication and Technique,” Current Opin-
ion in Otolaryngology & Head and Neck Surgery, Vol. 14,
No. 6, 2006, pp. 431-436.
 S. I. Atkinson and J. Rees, “Botulinum Toxin for Crico-
pharyngeal Dysphagia: Case Reports of CT-Guided In-
jection,” Journal of Otolaryngology, Vol. 26, No. 4, 1997,
 V. Annese and G. Bassotti, “Non-Surgical Treatment of
Esophageal Achalasia,” World Journal of Gastroenterol-
ogy, Vol. 12, No. 36, 2006, pp. 5763-5766.
 V. Annese, G. Bassotti, G. Coccia, M. Dinelli, V. D’Onofrio,
G. Gatto, et al. and the GISMAD Achalasia Study Group,
“A Multicentre Randomised Study of Intrasphincteric
Botulinum Toxin in Patient s wit h Oesophageal A cha l asia,”
Gut, Vol. 46, No. 5, 2000, pp. 597-600.
 M. Storr, P. Born, E. Frimberger, N. Weigert, T. Rösch,
A. Meining, et al., “Treatment of Achalasia: The Short-
Term Response to Botulinum Toxin Injection Seems to
be Independent of Any Kind of Pre-Treatment,” BMC
Gastroenterology, Vol. 2, 2002, p. 19.
 G. Zaninotto, R. Marchese-Ragona, C. Briani, M. Costan-
tini, C. Rizzetto, G. Portale, et al., “The Role of Bo t ul i n um
Toxin Injection and Upper Esopha geal Sphincter Myotomy
in Treating Oropharyngeal Dysphagia,” Journal of Gas-
trointestinal Surgery, Vol. 8, No. 8, 2004, pp. 997-1006.
 C. Cuillere, P. Ducrotté, F. Zerbib, E. H. Metman, D. de
Looze, F. Guillemot, et al., “Achalasia: Outcome of Pa-
tients Treated with Intrasphincteric Injection of Botulinu m
Toxin,” Gut, Vol. 41, No. 1, 1997, pp. 87-92.
 V. M. Fishman, H. P. Parkman, T. D. Schiano, C. Hills,
M. A. Dabezies, S. Cohen, et al., “Symptomatic Improve-
ment in Achalasia after Botulinum Toxin Injection of the
Lower Esophageal Sphincter,” American Journal of Gas-
troenterology, Vol. 91, No. 9, 1996, pp. 1724-1730.
 J. Kolbasnik, E. W. Wat erfall, B. Fachni e, Y. Chen and G.
Tougas, “Long-Term Efficacy of Botulinum Toxin in Cl as-
sical Achalasia: A Prospective Study,” American Journal
of Gastroenterology, Vol. 94, No. 12, 2004, pp. 3434-
 V. F. Eckardt, C. Aignherr and G. Bernhard, “Predictors
of Outcome in Patients with Achalasia Treated by Pneu-
matic Dilation,” Gastroenterology, Vol. 103, 1992, pp.
 M. Naumann, W. H. Jost and K. V. Toyka, “Botulinum
Toxin in the Treatment of Neurological Disorders of the
Autonomic Nervous System,” Archives of Neurology, Vol.
56, 1999, pp. 914-916.
 C. F. Torbey, C. Singaram, P. Bass and E. A. Gaumnitz,
“Action of Botulinum Toxin on Gut Smooth Muscle In-
volves Cholinergic and Non-C holinergic Neural Pathway ,”
Gastroenterology, Vol. 112, 1997, p. A840.
 A. Blitzer and M. F. Brin, “Use of Botulinum Toxin for
Diagnosis and Management of Cricopharyngeal Ach a l as i a, ”
Otolaryngology—Head and Neck Surgery, Vol. 116, No.
3, 1997, pp. 328-330.
 G. Y. Shaw and J. P. Searl, “Botulinum Toxin Treatment
for Cricopharyngeal Dysfunction,” Dysphagia, Vol. 16,
No. 3, 2001, pp. 161-167.
 J. Alberty, M. Oelrich, K. Ludwig, S. Hartmann and W.
Stoll, “Efficacy of Botulinum Toxin A for the Treatment
of Upper Esophageal Sphincter Dysfunction,” Laryngo-
scope, Vol. 110, No. 7, 2000, pp. 1151-1156.
 M. Moermann, Y. Callier, C. Dick and H. Vermeersch,
“Botulinum Toxin for Dysphagia Due to Cricopharyngeal
Dysfunction,” European Archives of Oto-Rhino-Laryn-
gology, Vol. 259, No. 1, 2002, pp. 1-3.
 R. Marchese-Ragona, G. Marioni, D. A. Restivo and A.
Staffieri, “Solving Dysphagia Due to Cricopharyngeal
Muscle Dysfunction with Botulinum Toxin,” European
Archives of Oto-Rhino-Laryngology, Vol. 262, No. 3,
2005, pp. 250-251.
 F. Mancini, G. Sandrini, A. Moglia, G. Nappi and C.
Pacchetti, “A Randomized, Double-Blind, Dose-Ranging
Study to Evaluate Efficacy and Safety of Three Doses of
Botulinum Toxin Type A (Botox) for the Treatment of
Spastic Foot,” Neurological Sciences, Vol. 26, No. 1, 2005,
pp. 26-31. http://dx.doi.org/10.1007/s10072-005-0378-9
 D. Dressler and J. C. Rothwell, “Electromyographic
Quantification of the Paralysing Effect of Botulinum
Toxin in the Sternomastoid Muscle,” European Neurol-
ogy, Vol. 43, No. 1, 2000, pp. 13-16.
 W. E. Waterfall, G. Tougas, B. Fachnie and U. Chauhan,
“Clinical and Manometric Response to Botulinum Toxin
(Botox) Used as Primary Treatment for Achalasia,” Gas-
troenterology, Vol. 108, 1995, p. A225.
 R. Mac Ever, M. Liptay and Y. Johnson, “A Case of Me-
diastinitis Following Botulinum Toxin Type A Treatment
for Achalasia,” Nature Clinical Practice Gastroenterol-
ogy & Hepatology, Vol. 4, No. 10, 2007, pp. 579-582.
 L. Dughera, E. Battaglia, D. Maggio, P. Cassolino, P. R.
Mioli, A. Morelli, G. Emanuelli, et al., “Botulinum Toxin
Treatment of Oesophageal Achalasia in the Old Old and
Oldest Old: A 1-Year Follow-Up Study,” Drugs Aging,
2005, Vol. 22, No. 9, pp. 779-783.