A Novel Balloon Catheter-based Dilation Intervention for Patients with Cricopharyngeus Achalasia After Stroke: A Randomized Study

Cricopharyngeus achalasia is a common cause of dysphagia caused by failure of relaxation of the cricopharyngeus muscle during the pharyngeal phase of swallowing [1‐3]. Its clinical symptoms and complications include dysphagia, coughing, choking, nasopharyngeal regurgitation, aspiration pneumonia, weight loss, and malnutrition [4, 5]. Cricopharyngeus dysfunction (CPD) can be a consequence of a spectrum of neurological diseases, including stroke, multiple sclerosis, amyotrophic lateral sclerosis, primary muscle disorders, skull base neoplasia, and Parkinson’s disease [3]. Patients with stroke have a relatively high risk of cricopharyngeus achalasia, especially in cases of brain stem stroke, which has an incidence rate of up to 70% [6].

A range of management stratagies exist to improve the cricopharyngeus muscle function and swallowing, including compensatory strategies, rehabilitation exercises, physical dilation, pharmacological interventions, and surgery. Dilation is the most commonly used intervention and can include bougies, a wire-guided polyvinyl dilator, air-filled pneumatic dilation, and water-filled balloon dilation with or without endoscopy guidance [7, 8]. Among these, balloon catheter dilation is the most effective method, which has been investigated in the previous study [9]. A previous study has demonstrated good efficacy with urethral catheter dilation in CPD patients after stroke, with both active and passive balloon dilation presenting benefits (narrowing or obstruction disappeared rate of 76.2% vs. 76.5%, respectively) [10]. However, to the best of our knowledge, balloon catheter dilation protocols have not been standardized yet. Although urethral catheters (No.14-No.16) are commonly used in China, these balloons are oval and small with several disadvantages such as heterogeneous pressure distribution, short ice stimulation time, and small expansion range.

In this study, we developed a novel balloon dilation catheter by improving the tube material, internal circulation structure, balloon shape, and ordinary urinary catheter length. This study aimed to investigate the effectiveness of dilation intervention using our novel balloon dilation catheter in patients with cricopharyngeus achalasia after stroke.

This study protocol was approved by the Ethics Committee of Hunan Provincial People's Hospital (No. 2021019). Informed consent was obtained from each participant for study inclusion.

This study determined that the use of the novel balloon catheter for dilation was more beneficial than the use of an ordinary urinary catheter in terms of several outcomes, including shorter dilation duration, shorter recovery time for swallowing function, and shorter recovery time for oral intake of food. Compared with the ordinary urinary catheter, this novel balloon catheter did not result in a higher complication incidence but had better tolerability.

To the best of our knowledge, this is the first study wherein a novel balloon dilation catheter is used in patients with cricopharyngeus achalasia after stroke. We believe that there are two reasons why the novel catheter can help patients recover more rapidly compared with an ordinary urinary catheter. First and most importantly is ice stimulation, which is an effective method to improve the motor and sensory activities of the tongue and soft palate through repeated mechanical, temperature, and pressure stimulation [16]. It increases the sensitivity of the swallowing reflex areas by stimulating the sensory input nerve fibers and eventually induces the swallowing reflex to improve the swallowing function [17, 18]. Kawakami,M et al. first reported the excitability of the human cortical swallowing motor pathway after oral ice stimulation and found that oral ice stimulation increases the excitability of the corticobulbar projection to the mylohyoid muscles, but ice stimulation to the superficial neck skin does not have any effects [19]. The No.14 ordinary urinary catheters, which are commonly used in clinical practice, have a balloon with only one water inlet valve. Filling the balloon with ice water and inserting it into the esophagus can achieve a relatively short time of ice stimulation, as the temperature rises quickly. To extend the ice stimulation time, we developed this new catheter with two independent cavities, both connected to the balloon, which could achieve continuous circulation of ice water in and out of the catheter. Thus, the cricopharyngeus muscle could continuously receive constant low temperature ice stimulation. Therefore, we believe that the combination of physical dilation and a relatively long-term ice stimulation has more beneficial effects compared with the combination of physical dilation and a relatively short-term ice stimulation.

In addition, the shape and size of the balloon might be the second reason for the superiority of our novel catheter. The cricopharyngeus muscle is the main muscle of the upper esophageal sphincter, which is a high-pressure zone lying between the pharynx and the cervical esophagus. Lang et al. [20] and Gerhardt et al. [21] demonstrated that the upper esophageal sphincter comprises the proximal esophageal circular muscle, cricopharyngeus muscle, and thyropharyngeal muscle, and the pressure gradually increases in this order. Sivarao et al. compared the manometric data from three different sources of the upper esophageal sphincter and concluded that the peak high-pressure zone lies above the anatomical extent of the cricopharyngeus muscle [22]. Although the cricopharyngeus muscle is only 1–2 cm wide, the high-pressure zone may be 2.5–4.5 cm in length [23]. Thus, patients with cricopharyngeus achalasia require dilation not only for the cricopharyngeus muscle but also for the entire high-pressure upper esophageal sphincter zone. The ordinary urinary catheter, which is only 2 cm in length, will cause insufficient expansion in this regard. Therefore, by increasing the length of the balloon to 4 cm, the upper esophageal sphincter high-pressure zone can be fully dilatated.

Despite the recovery time for oral intake of different foods, including liquid food, mushy food, and solid food, being shorter in the Exp group, the recovery time for oral intake of water was not markedly different between the two groups. Mostly likely, this is because the definition of recovery for oral intake of water involved drinking without choking. There are many other reasons for choking during drinking, besides cricopharyngeus muscle dysfunction, especially in patients with stroke. Therefore, even when the cricopharyngeus muscle function recovers, patients may still choke during drinking water for a prolonged period.

Despite the total time required for each intervention being similar between the two groups, i.e. approximately 30 min per intervention, the use of the novel balloon catheter was more easy comapred with the use of the ordinary urinary catheter; however, a longer time was taken for ice stimulation in the Exp group, eventually resulting in similar times for both the catheters. We believe there is a benefit in the novel catheter being made from medical silicone rather than latex, similar to the urinary catheters. A stiffer catheter makes it easier to pass through the high-pressure zone of the upper esophageal sphincter. Simultaneously, due to the single inlet valve of the ordinary urinary balloon catheter, the syringe needs to be used multiple times during operation, which increases the time and difficulty of the procedure.

Regarding adverse events in our study, the incidence of mucosal bleeding and laryngeal edema and the pain scores were similar between both the groups. In a study by Wu et al. [24], minor self-limiting mucosal bleeding was commonly observed during dilation but neither endoscopic hemostasis or blood transfusion was required. These results show that this type of intervention is a relatively safe and tolerable method for patients with cricopharyngeus achalasia. The novel balloon catheter is also as safe as the ordinary urinary catheter.

In our study, the physician who was blinded to the study decided whether the dilation therapy should be terminated or not based on the FOIS scores. The FOIS scoring system is a 7-point ordinal scale that reflects the functional oral intake [25]. Crary,M. A et al. have demonstrated that the FOIS scoring system is an independent measure of functional oral intake in a prospective study [26]. In our study, intervention was terminated when the FOIS score of participants was ≥ 6, which indicates normal oral intake without special requirements with or without special diet restrictions. This is also used in ordinary clinical practice as one of the discharge criteria for patients with dysphagia. According to Huai et al., the clinical outcomes of patients with dysphagia were considered to be significantly improved when their FOIS score increased to ≥ 3 [5]. In our study, the recovery time for an FOIS score of ≥ 3 in the Exp group was shorter than that in the Con group, indicating that the clinical outcomes improved quicker when patients received the novel balloon catheter dilation. The EAT-10 scoring system is a 10-item self-administered questionnaire about the severity of dysphagia symptoms and its clinical and social impact [27]. A previous study has demonstrated that a final EAT-10 score of ≥ 3 is considered abnormal [14]. In our study, the mean EAT-10 score at time of treatment termination in the Exp group (3) was significantly lower than that in the Con group (5). From these results, we can conclude that not all participants had an EAT-10 score of < 2 when the intervention was terminated. We believed the reason why the FOIS score recovered to normal but the EAT-10 score did not may be to do with psychological feelings and social influences. Although some patients achieved complete recovery for oral intake of water and foods, they still maintained some psychological barriers.

There are still some limitations of our study. First, this study used the EAT-10 and FOIS scores to clinically evaluate the swallowing function, whereas in future studies we plan to use gold standards methods such as VFSS or videoendoscopy swallowing study. Second, this study focused on patients with dysphagia after stroke, but the dysphagia degree and recovery ability vary according to the location and distribution of the stroke. In future studies, we will conduct subgroup analysis of patients with brain stroke in different locations. Third, the adverse events, including laryngeal edema or mucosal bleeding, in our study were assessed through visual evaluation by a physician. In future studies, we aim to use more accurate methods of evaluation, such as laryngoscopy. Finally, due to the time limitation, only short-term efficacy was discussed in this study, the long-term efficacy through follow-up examination will be discussed in a future study.

In conclusion, dilation intervention using the novel balloon catheter improves the swallowing function of patients with cricopharyngeus achalasia after stroke in a more effective and faster manner compared with the ordinary urinary catheter. This novel balloon catheter can be recommended for clinical practice.