rTMS Treatment site: The projection area of the swallowing center in the human skull was determined with reference to Emilia Michou,s study(Michou and Hamdy, 2009).
1.1 Case description:
A total of 60 patients with swallowing disorders were enrolled in this study and randomly assigned to the low-frequency rTMS group or the high-frequency rTMS group. Moreover, 30 patients with swallowing disorders were included in the control group. This research was approved by the Ethics Committee of The Third Affiliated Hospital of Zhejiang Chinese Medical University. All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. All methods were performed in accordance with relevant guidelines and regulations. Written informed consent was obtained from all individual participants included in the study.
1.1.1 Inclusion criteria: (1) Patients who met the International Classification of Diseases (ICD)-10 diagnostic criteria for cerebral infarction; (2) cerebral infarction confirmed with CT or MRI; (3) Kubota’s water-swallowing test and video fluoroscopic swallowing study (VFSS) screening indicated swallowing disorders, needing oral feeding modification; (4) conscious, stable vital signs, and ability to cooperate during treatment; (5) ≥ 18 and ≤ 80 years of age; (6) the duration of disease was one to six months since onset.
1.1.2 Exclusion criteria: (1) Swallowing disorders unrelated to cerebral infarction; (2) metal object and pacemaker in the body; (3) uncontrolled blood pressure (> 180/120 mm Hg); (4) vital organ failure; (5) cerebral infarction patients in critical condition; (6) brain stem infarction;
(7) epencephalon infarction.
1.2 Treatment
1.2.1 Routine Treatment
All enrolled patients received routine treatment for cerebral infarction, including amlodipine (to control blood pressure), atorvastatin (to lower blood lipids), and aspirin (anti-platelet agent), and routine treatment for swallowing disorders, including acetic acid stimulation, low-frequency electrical stimulation of pharyngeal muscles, and facial muscle function training.
1.2.2 rTMS Treatment
The Rapid2 transcranial magnetic stimulator (Magstim Company Limited, UK) with a figure-eight coil (inner diameter: 10 mm, outer diameter: 50 mm; one side) was used. During magnetic stimulation, the coil was secured in place. The standard stimulation mode was used.
(1) High-frequency rTMS group
Treatment site: The projection area of the swallowing center in the human skull was determined with reference to Emilia Michou,s study(Michou and Hamdy, 2009). The area to be stimulated was 3 cm anterior to the center of the top of head and then 8 cm lateral towards the infarction side (A model of rTMS stimulation site was showed in Figure 1, point C was the stimulation site).
Stimulation frequency: 10 Hz.
Stimulus intensity: The intensity was 80% of the movement threshold.
Total stimuli in each session and interval: rTMS was performed at 10 Hz stimulation for 1 s, interval 20 s, and then repeated next stimulation and interval.
Treatment time: rTMS was applied 20 minutes every day, for consecutive 30 days.
(2) Low-frequency rTMS group
Treatment site: Same as the high-frequency rTMS group.
Stimulation frequency: 1 Hz.
Stimulus intensity: The intensity was 80% of the movement threshold.
Total stimuli in each session and interval: rTMS was performed at 1 Hz stimulation, for 1 s, interval 20 s, and then repeated next stimulation and interval.
Treatment time: rTMS was applied 20 minutes every day, for consecutive 30 days.
(3) Control group
The control group received routine treatment but with no rTMS treatment. The total treatment time was 30 days.
1.3 Outcome measures
1.3.1 Kubota’s water-swallowing test
Before and after treatment, the Kubota’s water-swallowing test was performed to assess the patient’s swallowing function as follows: the patient was instructed to drink 30 mL of warm water, and the time required and any choking were recorded to classify swallowing function as profile I to V. Profile I: the patient drinks 30 mL of warm water all at once within five seconds (defined as a score of 0); profile II: the patient drinks the water after swallowing twice or more within five to 10 seconds with no choking (defined as a score of 2); profile III: the patient drinks the water all at once within five to 10 seconds with choking (defined as a score of 4); profile IV: the patient drinks the water after swallowing twice or more within five to 10 seconds with choking (defined as a score of 6); profile V: the patient chokes multiple times while drinking the water and found it difficult to finish drinking the water within 10 seconds (defined as a score of 8).
1.3.2 VFSS
Before and after treatment, VFSS was performed with a digital gastrointestinal X-ray machine (VS-20D, Shimazu, Japan) to assess the patient’s swallowing function as follows:
Mouth period: the food in the mouth cannot be delivered to the pharynx (defined as a score of 0); cannot move a piece of food into the pharynx or can only form a paste in the pharynx (defined as a score of 2); cannot completely move all food into the pharynx at one time, some food remains after swallowing action (defined as a score of 4).
Pharynx period: cannot cause the pharynx to lift up, swallowing reflex is insufficient (defined as a score of 0); a large amount of residual food remains in the pyriform fossa (the residual food is larger than 1/2 of the pyriform fossa) (defined as a score of 1); a small amount of residual food (less than 1/2 of the residual food) remains in the pyriform fossa (defined as a score of 2); can move food into the esophagus using a swallowing action (defined as a score of 3).
Degree of aspiration: Most of the food was inhaled by mistake, no cough was observed (defined as a score of 0); most of the food was inhaled by mistake, cough present (defined as a score of 1); a small amount of aspiration was observed, no cough (defined as a score of 2); a small amount of aspiration was observed, cough present (defined as a score of 3); no food was inhaled by mistake, no cough observed (defined as a score of 4).
1.3.3 Detection of major intracranial neurotransmitters
The patients and control subjects underwent intracranial neurotransmitter detection using the Encephalofluctuograph analytical instrument (ML2001 encephalofluctuograph analyzer, Beijing Tongren Optoelectronics Technology Co., Ltd.). According to the international 10-20 electrode system, the anterior and posterior attachment of the sutura nasofrontalis to the external occipital protuberance as one of the base line, the left and right articulation of the anterior fossa of both ears as the other base line. A total of 12 leads, which included F3(left frontal), F4(right frontal), C3(left the central), C4(right the central), P3(left top), P4(right top), O1(left occipital), 02(right occipital), F7( left anterior temporal), F8( right anterior temporal), T5(left posterior temporal), and T6(right osterior temporal) were used to record the EEG. Bilateral reference electrodes were placed on the right and left earlobes.
The electrical signals were recorded for 18 minutes via encephalofluctuograph analytical instrument and were stored for EEG analysis. Then the EEG signals were analyzed by encephalofluctuograph to finally obtain a new informative frequency hidden in the brain waves, which typically falls in the range of 1–255 MHz. The waves are correlated to a super-slow shocking S system, including the S1–S255 series, which could reflect the activity of different intracranial neurotransmitters, with the S1, S2, S4, S5, S7, and S11 series corresponding to γ-aminobutyric acid (GABA), glutamate (Glu), 5-hydroxytryptamine (5-HT), acetylcholine (Ach), norepinephrine (NE), and, dopamine (DA) respectively. The data of neurotransmitters was analyzed and converted into value form by FoxPro v6.0 database software in ML2001 encephalofluctuograph analyzer before export.
1.4 Statistical analysis
The data were analyzed using SPSS 18.0 software. The data are presented as the mean±standard error of mean (S.E.M.) or the mean±standard deviation (S.D.). Descriptive statistics were performed to determine whether the data were normally distributed. Normally distributed data were analyzed with one-way analysis of variance (ANOVA) and independent sample t test, and non-normally distributed data with non-parametric test. P ≤ 0.05 was considered statistically significant.