In accordance with the time-limit regulations for ethical review, since the ethical approval certificate of this study protocol has expired, I hereby formally apply for the withdrawal of this study from the clinical trial registration platform.

Sialorrhea refers to a group of syndromes characterized by excessive saliva secretion from the salivary glands or reduced clearance of oral saliva due to dysphagia, resulting in saliva overflowing from the corners of the mouth or accumulating in the pharynx. It is one of the common clinical problems in conditions such as cerebral palsy, Parkinson's disease [1], and brain injuries (including stroke, traumatic brain injury, and hypoxic-ischemic encephalopathy). Among them, true bulbar palsy after medullary injury often causes saliva to flow out from the corners of the mouth due to sensory impairment in the oral cavity, tongue, and pharynx, as well as motor dysfunction and loss of coordination of swallowing-related muscles [2]; on the other hand, it often leads to residual saliva in the hypopharynx due to weakness of the pharyngeal constrictor muscles and dysfunction of the upper esophageal sphincter [3]. Sialorrhea can not only cause oral odor, skin breakdown, and malnutrition but also have a negative impact on patients' psychology, and even lead to choking or aspiration pneumonia, seriously endangering their physical and mental health. Therefore, active management and treatment of sialorrhea in patients with true bulbar palsy have become the key to solving this problem.

Currently, the management of sialorrhea mainly involves improving swallowing function to enhance saliva clearance and using drug intervention to reduce saliva secretion, thereby alleviating sialorrhea symptoms. However, current studies have found that swallowing function cannot recover quickly in a short time in patients with medullary injury. Therefore, active intervention is needed to reduce saliva secretion to relieve sialorrhea symptoms. Clinical treatments for sialorrhea include drug therapy, botulinum toxin therapy, radiation therapy, and surgical treatment. Among them, oral drug therapy is mainly based on antimuscarinic drugs. Although it has a certain therapeutic effect, its clinical application is limited due to the side effects of systemic anticholinergic effects; while surgical treatment is not clinically adopted because of its high destructiveness.

In recent years, a number of clinical studies on botulinum toxin type A (BTX-A) in the treatment of sialorrhea in adults (Parkinson's disease, traumatic brain injury) and children (cerebral palsy) have been carried out at home and abroad, and its efficacy and safety have been verified [4] [5]. However, there are few reports on BTX-A in the treatment of sialorrhea in patients with medullary lesions. Therefore, this study aims to conduct a randomized controlled trial to explore the effect of ultrasound-guided botulinum toxin type A injection into the salivary glands on sialorrhea in patients with true bulbar palsy, and comprehensively evaluate the efficacy and safety of BTX-A in the treatment of sialorrhea by combining subjective scale assessment and objective instrument assessment.

Inclusion Criteria:① Aged 18-80 years; ② Cerebral magnetic resonance imaging or computed tomography confirms medullary lesions (hemorrhage, ischemia, or tumor); ③ Dysphagia is clearly diagnosed by flexible endoscopic evaluation of swallowing (FEES); ④ Presence of sialorrhea, which is defined as meeting any one of the following three criteria: total score of the Drooling Severity and Frequency Scale (DSFS-T) ≥ 4 points, each item score of the Drooling Severity and Frequency Scale (DSFS) ≥ 2 points, or score of the Murray Secretion Scale (MSS) for pharyngeal secretions ≥ 2 points; ⑤ Conscious and able to cooperate with sialorrhea assessment and follow-up; ⑥ Willing to receive BTX-A injection, informed of the study details, and sign the relevant informed consent documents.

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Exclusion Criteria:① Having received BTX-A injection treatment in the recent six months;

• Having an allergy or contraindication to botulinum toxin;

  • Having taken drugs for treating sialorrhea or drugs that can cause sialorrhea in the recent month;

    • Having severe diseases of important organs such as the heart, lungs, liver, kidneys, or malignant tumors, etc.; ⑤ Concomitantly using aminoglycoside antibiotics and warfarin; ⑥ Patients with infection or skin lesions at the injection site, or severe muscle atrophy at the injection site, or those with infection at the injection site, or skin lesions at the injection site, or severe muscle atrophy at the injection site, or infection.