Dysphagia is a potential complication of anterior cervical spine surgery (ACSS). Although the reported incidence rate of dysphagia after ACSS varies, it is known to occur in up to 70% of cases after ACSS and related risk factors include multilevel surgery, female sex, and involvement of the C4-C5 and C5-C6 levels^1,2. There is no specific treatment for dysphagia that occurs after ACSS; as a conservative treatment method, the patient is educated on behavioral management tech-niques including postural changes, swallowing mane-uvers and effortful swallowing exercises³. The prog-nosis may be poor owing to complications such as malnutrition and aspiration pneumonia. Therefore, it is important to ascertain the dietary intake of such patients through appropriate management. However, the cause of dysphagia after ACSS has not yet been clearly identified, and many studies are ongoing. One proposed factor contributing to this complication is recurrent laryngeal nerve (RLN) injury that may occur during surgery^4,5.

The upper esophageal sphincter (UES) is normally closed but it opens during swallowing. The muscles involved in the closing of the UES include the inferior pharyngeal constrictor, cricopharyngeus, and cervical esophagus, with the cricopharyngeus being the most significant⁶. The dilation of the esophagus following the entry of food causes the relaxation of the UES. The UES relaxation is triggered by the relaxation of the cricopharyngeus which is innervated by the pharyn-geal plexus and RLN^6,7. Since the cricopharyngeus muscle receives innervation from the RLN, difficulties in swallowing may occur due to impaired UES opening resulting from RLN injury.

Previous studies have shown an improvement in dysphagia in patients with cricopharyngeal problems through videofluoroscopic swallowing study (VFSS)- guided balloon dilatation of the UES^8,9. This method induces swallowing exercises via repetitive reflexes tri-ggered by balloon dilatation. Notably, balloon inflation between the 4th and 5th cervical vertebrae induces a swallowing reflex by stimulating the pharyngeal nerve plexus around the cricopharyngeus muscle. However, to the best of our knowledge, no previous studies have reported on the efficacy of VFSS-guided balloon dila-tation for addressing post-ACSS dysphagia. This case report describes VFSS-guided balloon dilatation per-formed in a patient with UES opening dysfunction due to RLN damage after ACSS; we confirmed impro-vement in dysphagia and UES opening following the procedure.

A 55-year-old man experienced cervical spinal cord injury (neurological level C5; American Spinal Injury Association D [ASIA-D]) following a bicycle accident. On physical examination, the motor power grade of both upper extremities was 4 and the motor power of both lower extremities was almost intact. Based on the findings of the imaging test and the physical examination, central cord syndrome was suspected in the patient. Subsequently, the patient underwent ante-rior cervical discectomy and fusion of C5-7. The patient had no past medical history or risk factors that could have caused dysphagia after surgery. The surgery lasted for approximately 2 hours and no complications were observed during the surgical pro-cedure. The patient did not complain of hoarseness or dysphagia before surgery. However, immediately after surgery, the patient experienced dysphagia to the extent of being unable to swallow saliva; additio-nally, hoarseness was observed. Therefore, it was suspected that dysphagia may have originated from a cause unrelated to cord injury. Under the super-vision of an otolaryngologist, we performed laryngo-scopy to assess the presence of nerve damage, which revealed that the left vocal cord was slightly weaker and bowed more than the right one.(Fig. 1A) The left cord was located lateral to the midline rather than being positioned at the midline. The right cord was normal and located at the midline when the vocal cords were closed.(Fig. 1B) In addition, the movement of the intrinsic muscle of the larynx during phonation was observed using a laryngoscope. At this time, it was observed that the posterior cricoarytenoid, lateral cricoarytenoid, thyroarytenoid, and interarytenoid mus-cles, which receive innervation from the RLN, were fixed and immobile.(Fig. 1B) Consequently, we were able to confirm that the patient had left-sided vocal cord paralysis due to damage to the left RLN¹⁰ and inferred that this caused hoarseness and dysphagia.

Figure 1. Laryngoscopy findings. (A) During expiration: The weak vocal cord appears more bowed than the right. (B) During phonation: The left cord is not positioned in the midline but is located laterally in a paramedian position. The right cord is normal and remains positioned in the midline when the vocal cords are closed.

On postoperative day 5 (POD 5), two physiatrists performed the initial VFSS to properly evaluate dys-phagia and develop a treatment plan using the revised protocol from Logemann’s study¹¹. A barium swallow study was conducted using barium contrast (barium sulfate; Solotop suspension) mixed with liquid and solid foods. The initial VFSS revealed a tightly closed UES, and the patient was unable to swallow yogurt through the UES. Subglottic aspiration occurred during the ingestion of curd-type yogurt along with 3 ml of diluted barium.(Fig. 2A) Due to the UES closure and the inability to insert the nasogastric tube (NG tube), the patient was nourished through total parenteral nutrition. At this point, the patient’s Functional Oral Intake Scale (FOIS) score was 1. Subsequently, the pa-tient received conventional dysphagia therapy from a skilled physical therapist. The treatment was performed for 50 minutes, once a day, 3 days per week on week-days. The treatment included oromotor sensory stimulation, supraglottic swallow, effortful swallow, and Men-delsohn maneuver. However, the patient’s FOIS score remained at 1 after receiving the conventional dys-phagia therapy, with no improvement. Additionally, the patients’ subjective symptoms were assessed using a Disability Rating Scale for swallowing impairment.

Figure 2. Videofluoroscopy-guided ballon dilatation of the upper esophageal sphincter (UES). (A) Video-fluoroscopic swallowing study demonstrating a firmly closed UES. The patient was unable to swallow yogurt through the UES. (B) After confirming that the 10-Fr Foley catheter is placed in the UES through fluoroscopy, a contrast agent is being injected.

On POD 12, a VFSS-guided balloon dilatation of the UES was performed. A 10-Fr Foley catheter with a deflated balloon was inserted until it reached the UES. The balloon was inflated using 5 ml of contrast medium and kept in place for 20 s to achieve mechanical dilation of the UES.(Fig. 2B) This procedure was repea-ted five times, with a 1-minute interval per session. Subsequent sessions were conducted on POD 15, 18, 21, and 24. No significant adverse events were obser-ved in the patient during the ballooning procedure.

On POD 26, a follow-up VFSS was performed for objective evaluation. The test began with curd-type yogurt and 3 ml of diluted barium. Previously, aspir-ation was observed owing to the yogurt remaining in the pyriform sinus and then overflowing; however, this time, the yogurt could be swallowed after five swallowing efforts. However, subglottic aspiration per-sisted.(Fig. 3A) Therefore, the patient still had to continue with NG tubal feeding, and the FOIS score was evaluated as 2.

Figure 3. Videofluoroscopic swallow study findings. (A) Yogurt (3 ml) could be swallowed in five swallowing attempts; however, subglo-ttic aspiration is observed (On POD 26). (B) Yogurt (3 ml) could be swallowed in three swallowing attempts without aspiration (After five sessions of procedures).

Following five sessions, the patient was discharged with the NG tube in place. On POD 33, a follow-up VFSS was performed and the patient could swallow 3 ml of yogurt in three attempts without aspiration.(Fig. 3B) The patient was able to swallow food without aspiration, but the NG tube had to be kept in place for nutrient supply; therefore, the FOIS score was 3. On POD 60, the last follow-up VFSS was performed and the patient maintained the ability to swallow yogurt with-out aspiration. FOIS score remained at 3, and the patient’s subjective symptoms as confirmed by the Disability Rating Scale for swallowing impairment improved from 5 to 2 points.

This case report highlights the successful application of VFSS-guided balloon dilatation in addressing dysphagia associated with ACSS, specifically focusing on RLN injury-induced UES dysfunction. The implications, limitations, and potential future directions have been discussed in the subsequent sections.

The incidence of symptomatic RLN injury following ACSS surgery is approximately 8%⁴. Although some patients show some degree of recovery, some may not recover even after 5 years¹². The RLN located in the trachea-esophageal groove is exposed if the surgical site is at or below C6. Despite being secured properly during surgery, the RLN may still be susceptible to direct injury or displaced by retracting the organs in the midline¹³. Furthermore, RLN may be injured due to overstretching during retraction by the cervical retractor or due to entrapment between the retractor and the endotracheal tube¹². Therefore, appropriate evaluation to confirm the presence of RLN injury is important in patients who complain of symptoms such as hoarseness and dysphagia after ACSS.

Treatment options for patients experiencing dys-phagia due to UES opening dysfunction include cri-copharyngeal myotomy and botulinum toxin injection in addition to balloon catheter dilatation, which was applied in our patient^14,15. Cricopharyngeal myotomy is a procedure that involves surgical removal of the muscle at the pharyngo-esophageal junction to mini-mize resistance and facilitate the movement of bolus from the pharynx to the cervical esophagus after swallowing¹⁶. Although several studies have demon-strated its effectiveness¹⁴, complications such as recu-rrent nerve paralysis, retropharyngeal hematoma, cer-vical fasciitis and mediastinitis are more common owing to the invasive nature of the procedure¹⁶. Botu-linum toxin injection is a procedure involving the administration of 5-100 IU of botulinum toxin into the cricopharyngeal muscle to enable easy movement of the bolus through the relaxation of the UES¹⁷. However, the success rate is lower than that of crico-pharyngeal myotomy¹⁴ and the duration of the treat-ment effect varies depending on the injection site and dosage¹⁷. No significant difference in the success rate was observed between balloon dilatation and the other two methods¹⁴. Compared with other treatments, balloon dilatation is a very effective treatment option because it is less invasive, associated with relatively few complications and offers a prolonged effect⁸.

A previous study employed the traditional method which involved using a through-the-scope balloon dilation catheter positioned across the upper esopha-geal sphincter under visual guidance⁹. The balloon was then sequentially inflated with each distention held in position for 30-60 s, reaching a maximum diameter of 45-Fr to 60-Fr. This procedure has to be performed under sedation and the upper esophageal sphincter and surrounding structures were closely inspected for signs of mucosal damage after dilata-tion. Of the 20 patients included in the study, appro-ximately 80% showed improvement in dysphagia. However, owing to the increased diameter of the cathe-ter, complications such as mucosal rupture could occur, and the patient had to be sedated⁹. Therefore, we preferred to use a Foley’s catheter in our case, as previously described^8,18. This procedure involved the placement of a 16-Fr Foley catheter in the UES and dilatation was performed for 3 min. Each ballooning was repeated six times. Significant reductions in pha-ryngeal transit time and pharyngeal remnants were observed⁸. In another case report, a 16-Fr Foley cat-heter was placed in the UES and ballooning was performed 10 times per session for 30 s at one-minute intervals. This procedure was repeated 11 times for 2 months. Subsequently, VFSS performed during the last visit revealed no aspiration, and an improvement in UES opening was observed¹⁸. However, entry was challenging in our patient because the UES was firmly closed; therefore, we used a 10-Fr Foley catheter instead of a 16-Fr Foley catheter.

Considering the commonly recognized muscles in-volved in UES opening, such as the cricopharyngeus, the esophago-UES relaxation reflex has been descri-bed in detail in a previous study⁷. Rapid distention of the esophagus induces UES relaxation primarily invol-ving the cricopharyngeus. The specific involvement of the thyropharyngeus or cervical esophagus in this reflex remains unclear, but it is presumed to play a role. This reflex is triggered by the rapid adaptation of mucosal mechanoreceptors, primarily functioning through the afferent limb of the vagus nerve. Notably, RLN, the nerve impaired in our patient is a branch of the vagus nerve; therefore, it could be presumed that dysfunction in the UES opening, as observed in our patient, could be attributed to RLN injury.

VFSS-guided balloon dilatation has been employed previously to treat patients with dysphagia after cer-vical area surgery. However, one patient had under-gone laminoplasty by posterior approach not an anterior approach surgery and the other patient had undergone surgery for retropharyngeal abscess remo-val¹⁸. Therefore, this is the first case report to demo-nstrate the effectiveness of VFSS-guided balloon dila-tation treatment for RLN nerve injury-induced dys-phagia following anterior cervical spine surgery.

Our study had certain limitations. First, a laryngeal electromyogram (EMG) should have been performed before and after the ballooning procedure to exclude the possibility of a natural course of the patient’s neurological recovery and to accurately evaluate the RLN injury. However, EMG was not performed because the patient complained of the needling process. Accu-rately diagnosing RLN injury based on laryngoscopy findings alone is not always reliable. However, consi-dering that movement of the patient’s left intrinsic muscles of the larynx was not observed in our patient and the surgical site is at the level of C6, the trachea- esophageal groove area where the RLN is located, the possibility of injury to the RLN had been confirmed¹⁰.

The observed improvement in UES opening after VFSS-guided balloon dilatation suggests a potential therapeutic approach for managing post-ACSS dys-phagia. The therapeutic mechanism involves inducing a swallowing reflex through repetitive exercises facili-tated by balloon dilatation. Specifically, inflating the balloon between the C4 and C5 triggers the swallowing reflex by stimulating the pharyngeal nerve plexus around the cricopharyngeal muscle. Swallowing exercises are performed by repeating this process. Additionally, the range of motion of the cricopharyngeus muscle is enha-nced by passing the balloon catheter through the UES. Consequently, it contributes to the reduction of UES impedance and an improvement in UES relaxation⁸.

The clinical significance of improved UES opening is evident in the transition from total parenteral nutrition to the successful ingestion of yogurt without aspiration. Moreover, the patient showed substantial improvement in subjective symptoms of dysphagia. Although the functional outcomes are promising, longterm follow- up studies are needed to assess the sustained efficacy and potential recurrence of dysphagia.

Safety considerations and the generalizability of VFSS-guided balloon dilatation to a broader population are crucial. Compared to other treatment options, VFSS- guided balloon dilatation can be used in patients with potential difficulties undergoing cricopharyngeal myo-tomy or botulinum toxin injection owing to under-lying complications or high cost and to avoid general anesthesia in older adults. Furthermore, VFSS-guided balloon dilatation can be the first option because it is less invasive and had comparable outcomes. How-ever, compared to other treatments, patient cooperation is crucial in the treatment process and a lack of mo-tivation or impaired cognitive functions to understand instructions may limit its clinical application.

Further studies exploring the variations in the pro-tocol such as balloon size, inflation duration, and num-ber of sessions are warranted to optimize its effecti-veness. Additionally, collaborative efforts across ins-titutions can facilitate multicenter studies to enhance the external validity and generalizability of the findings.

In conclusion, VFSS-guided balloon dilatation can be considered an effective treatment alternative for patients experiencing dysphagia due to impaired UES opening caused by nerve injury after ACSS.

No potential conflict of interest relevant to this article was reported.