Introduction: The purpose of this single subject study was to describe the dysphagia presentation, treatment course, and post-treatment swallowing function in a patient with chronic dysphagia after anterior cervical discectomy and fusion (ACDF) surgery. Case Presentation: An 83-year-old male experienced dysphagia >2 months post-ACDF. The patient presented with a narrowed pharyngoesophageal segment due to cervical hardware and reduced epiglottic inversion due to pharyngeal narrowing on videofluoroscopic swallow study (VFSS). He completed dysphagia therapy using neuromuscular electrical stimulation (NMES). Structural alterations and a complicated medical course after treatment impacted therapeutic outcomes. Reductions in penetration or aspiration and improved hyoid excursion were found post-treatment, though impairment persisted. The patient ended therapy after the post-treatment VFSS and began to experience odynophagia and submental pain. The patient experienced a complicated post-treatment course including bilateral cancerous masses at the base of tongue with subsequent surgery and chemoradiation. Conclusions: While considered rare, these findings present a post-operative course of chronic dysphagia post-ACDF surgery where morphological changes to the pharynx significantly altered swallowing function. Swallowing function should be tracked routinely and longitudinally in post-ACDF surgery patients. NMES may be a potential dysphagia therapy modality to explore.

Anterior cervical discectomy and fusion (ACDF) is the most common approach for cervical spinal surgical procedures targeting decompression and fusion. It is often considered a highly successful procedure with minimal or easily manageable post-surgical complications reported [1‒3]. The most common procedural technique is the anterior approach, typically characterized by creating an incision in the anterior neck and bypassing structures such as the larynx, trachea, and esophagus to reach the cervical spine [3, 4]. Though it is reported ACDF possesses limited post-surgical complications, dysphagia and swallowing difficulties are increasingly understood as a common post-operative condition [5]. Reported rates of post-operative dysphagia are inconsistent, ranging anywhere from approximately 10–57% [1, 5, 6], particularly in the acute post-operative stage.

Despite the potential for dysphagia with the anatomical structures that are directly (i.e., pharyngeal wall) or indirectly affected (i.e., larynx), our understanding of how dysphagia manifests post-ACDF surgery is still developing. Recent evidence suggests that early post-operative dysphagia is significantly worse than late post-operative dysphagia (i.e., >2 months) [7], with relatively typical pharyngeal swallow function >2 months post-surgery. However, we present a subject who experienced persistent dysphagia at approximately 2 months post-surgery, an outlier in most estimates of post-ACDF dysphagia [7]. Given its purported low incidence level, guidance on treatment modalities for chronic post-ACDF dysphagia is unclear. Additionally, there is a substantial gap in the literature on treatment options or efficacy, as it often focuses on reducing swelling or edema locally via steroid application in the acute stages [8].

Given the lack of comprehensive literature regarding chronic post-ACDF dysphagia and rehabilitative treatment approaches, the goals of this study were to present an atypically expected presentation of chronic dysphagia post-ACDF surgery, characterize this presentation, and report on the potential of a novel dysphagia treatment modality and its effects for this case.

Patient Demographics, Medical Case History, and Therapy Approach

The CARE Checklist has been completed by the authors for this case report, attached as online supplementary material (File B) (for all online suppl. material, see https://doi.org/10.1159/000546013). The patient was an 83-year-old male at the time of his initial videofluoroscopic swallow study (VFSS) with no prior history of dysphagia. He underwent ACDF surgery at the beginning of April in 2022 approximately at the level of C4–C5. There were no significant complications from the surgery noted, and no other structural or anatomical abnormalities noted during the surgery. The patient received no follow-up dysphagia screening, evaluation, or treatment post-surgery.

His first VFSS was conducted at the end of May in 2022 due to reports of ongoing difficulty swallowing including coughing on solids and liquids, difficulty swallowing pills, odynophagia, globus sensation, reduced food and liquid intake, and weight loss. The patient had no other medical concerns or active conditions that may have contributed to or caused swallowing difficulties and was not taking any medications. The patient had been consuming a regular diet with thin liquids and no restrictions outside of his noted complaints.

During the baseline and post-treatment VFSS, a preliminary cranial nerve exam and a orofacial exam were completed. All structures and functions were noted to be within normal limits. The patient presented with normal cognitive status and an informal report by his wife that he did not have cognitive deficits. In both the baseline and post-treatment VFSS, there was a narrowing of the pharyngoesophageal segment area, superior to the upper esophageal sphincter (UES), caused by the hardware present. This was noted on VFSS documentation as well as during the data extraction process in our laboratory. This can be seen in Figure 1.

Fig. 1.

VFSS at the height of nectar thick barium (approximately IDDSI level 2) swallow depicting impaired epiglottic inversion and narrowed pharyngoesophageal segment.

Fig. 1.

VFSS at the height of nectar thick barium (approximately IDDSI level 2) swallow depicting impaired epiglottic inversion and narrowed pharyngoesophageal segment.

Close modal

Additionally, there was a marked thickening and subsequent narrowing of the mid-inferior pharyngeal space preventing inversion of the epiglottis during the height of the swallow. Figure 2 highlights this, where during pharyngeal shortening, this thickened pharyngeal wall creates a narrowing of the pharyngeal space directly in the path of the epiglottis, preventing full epiglottic inversion.

Fig. 2.

VFSS at the height of saliva swallow depicting impaired epiglottic inversion, pharyngeal wall thickening, and narrowed pharyngoesophageal segment.

Fig. 2.

VFSS at the height of saliva swallow depicting impaired epiglottic inversion, pharyngeal wall thickening, and narrowed pharyngoesophageal segment.

Close modal

The overall impression of pre-treatment (baseline) and post-treatment swallowing function is presented in Tables 1 and 2, at the bolus level. Referencing typical healthy adult swallowing parameters [9], and at baseline, the patient presented with substantially prolonged swallow reaction time (SRT) and time-to-laryngeal vestibule closure (LVC), atypically shortened LVC duration, atypically increased levels of pharyngeal residue across all pharyngeal locations measured, and substantially increased pharyngeal area at maximal constriction. He also presented with atypical severity and frequencies of Penetration-Aspiration Scale (PAS) scores and atypical frequencies of incomplete LVC.

Table 1.

Bolus level pre-treatment and post-treatment timing intervals

Teaspoon nectarCup sip nectarTeaspoon thinCup sip thinTeaspoon puddingMechanical soft – mixed consistency
Timing intervals1 
 SRT 
  Pre 0.37 2.07 0.67 1.13 2.17 10.87 
  Post 2.94 2.13 0.07 0.05 1.85 11.63 
 Time-to-LVC 
  Pre 0.43 0.33 0.35 0.23 0.47 0.70 
  Post 0.31 0.29 0.19 0.53 0.32 0.39 
 LVC duration 
  Pre 0.10 0.10 0.22 0.07 0.47 0.17 
  Post 0.75 0.27 0.37 0.20 0.32 0.13 
 Time-to-peak hyoid frame 
  Pre 1.76 1.82 1.79 1.95 1.74 1.46 
  Post 2.56 2.89 2.69 2.61 2.73 2.67 
Teaspoon nectarCup sip nectarTeaspoon thinCup sip thinTeaspoon puddingMechanical soft – mixed consistency
Timing intervals1 
 SRT 
  Pre 0.37 2.07 0.67 1.13 2.17 10.87 
  Post 2.94 2.13 0.07 0.05 1.85 11.63 
 Time-to-LVC 
  Pre 0.43 0.33 0.35 0.23 0.47 0.70 
  Post 0.31 0.29 0.19 0.53 0.32 0.39 
 LVC duration 
  Pre 0.10 0.10 0.22 0.07 0.47 0.17 
  Post 0.75 0.27 0.37 0.20 0.32 0.13 
 Time-to-peak hyoid frame 
  Pre 1.76 1.82 1.79 1.95 1.74 1.46 
  Post 2.56 2.89 2.69 2.61 2.73 2.67 

1All timing intervals are expressed in seconds and fractions of seconds.

Table 2.

Bolus level pre-treatment and post-treatment pixel-based measures

Pixel-based measures1Teaspoon nectarCup sip nectarTeaspoon thinCup sip thinTeaspoon puddingMechanical soft – mixed consistency
Pharyngeal area at maximal constriction 
 Pre 2.78 3.33 3.24 4.44 2.39 3.67 
 Post 4.06 4.07 4.39 4.81 4.19 4.79 
Vallecular residue 
 Pre 1.92 1.77 1.72 2.03 1.40 1.49 
 Post 1.47 2.47 0.91 2.52 1.65 2.46 
Pyriform residue 
 Pre 1.47 1.61 1.27 1.77 0.99 1.09 
 Post 1.69 1.87 1.51 1.32 1.61 1.30 
Other pharyngeal residue 
 Pre 1.47 2.38 1.48 1.75 1.43 2.19 
 Post 3.30 3.86 1.35 2.82 3.62 2.69 
Total residue 
 Pre 4.87 5.76 4.46 5.55 3.83 5.11 
 Post 7.20 8.19 3.77 6.66 6.88 6.46 
Peak hyoid displacement2 
 Pre 1.76 1.82 1.79 1.95 1.74 1.46 
 Post 2.65 2.88 2.69 3.08 2.73 2.68 
UES maximum opening2 
 Pre 0.22 0.29 0.26 0.33 0.24 0.19 
 Post 0.43 0.46 0.40 0.48 0.38 0.35 
Pixel-based measures1Teaspoon nectarCup sip nectarTeaspoon thinCup sip thinTeaspoon puddingMechanical soft – mixed consistency
Pharyngeal area at maximal constriction 
 Pre 2.78 3.33 3.24 4.44 2.39 3.67 
 Post 4.06 4.07 4.39 4.81 4.19 4.79 
Vallecular residue 
 Pre 1.92 1.77 1.72 2.03 1.40 1.49 
 Post 1.47 2.47 0.91 2.52 1.65 2.46 
Pyriform residue 
 Pre 1.47 1.61 1.27 1.77 0.99 1.09 
 Post 1.69 1.87 1.51 1.32 1.61 1.30 
Other pharyngeal residue 
 Pre 1.47 2.38 1.48 1.75 1.43 2.19 
 Post 3.30 3.86 1.35 2.82 3.62 2.69 
Total residue 
 Pre 4.87 5.76 4.46 5.55 3.83 5.11 
 Post 7.20 8.19 3.77 6.66 6.88 6.46 
Peak hyoid displacement2 
 Pre 1.76 1.82 1.79 1.95 1.74 1.46 
 Post 2.65 2.88 2.69 3.08 2.73 2.68 
UES maximum opening2 
 Pre 0.22 0.29 0.26 0.33 0.24 0.19 
 Post 0.43 0.46 0.40 0.48 0.38 0.35 

1Pixel-based measures of pharyngeal residue are expressed as percentages of the C2–C42 scalar derived from the tracheal width.

2Peak hyoid displacement and UES maximum opening are expressed as a ratio of two times the tracheal width – roughly corresponding to the length of C2–C4 (Steele et al. [9]).

Based on the findings of the baseline VFSS, it was recommended the patient consume a dietary level commensurate with International Dysphagia Diet Standardization Initiative (IDDSI) levels 6 for solids (soft and bite sized) and level 0 for liquids. Utilizing repeat swallows and supraglottic swallows as compensatory strategies was recommended to clear pharyngeal residue and prevent airway invasion. Based on his level, the patient was considered a good candidate for dysphagia therapy to reduce the need for strategies and risk of ongoing penetration or aspiration due to swallow impairment.

The patient began therapy in the beginning of June 2022 and received their last treatment session at the end of August 2022, following the therapy timeline outlined in the Instrumentation and Procedures of Therapy section. The dysphagia therapy protocol implemented primarily utilized neuromuscular electrical stimulation (NMES) in conjunction with an effortful saliva swallow, while stimulation was active. This was based on the above VFSS findings, which displayed evidence of reduced epiglottic inversion, reduced UES opening, incomplete and prolonged LVC, and pharyngeal residue along with clinically judged reduced laryngeal elevation. Specific parameter and placement information used by the clinician for this approach can be found in the Instrumentation and Procedures of Therapy section below.

Instrumentation and Procedures of Therapy

The patient received NMES as their primary treatment for dysphagia. NMES was implemented utilizing a power stimulator with bilateral suprahyoid placement of surface electrodes (Ampcare, LLC). Parameters implemented included a fixed pulse frequency of 30 Hertz (Hz), a phase duration of 50 microseconds (µs) at the start of therapy that was increased to 250 µs for the final 12 therapy sessions based on patient progression and tolerance, and variable intensity in milliamps (mA)-dependent on patient tolerance and progression within and across therapy sessions.

Stimulation was delivered at a predetermined frequency (ON) for 5 s intervals, during which time the patient was cued to swallow effortfully during the stimulation period. Rest periods without stimulation active (OFF) began at 25 s and were decreased based on variable patient tolerance to as low as 15 s OFF prior to the next stimulation. The patient was instructed to drink water during OFF periods to facilitate swallow function in the following ON period and provide comfort. Sessions lasted 30 min with the therapeutic target being to swallow as effortfully as possible, as many times as possible, across the session.

The patient was seen for 13 weeks, 2 days per week, receiving treatment for 26 days total. He did not miss any sessions. Demographic information gathered included age at the start of therapy, gender, clinician notes from treatment sessions to extract NMES parameters, and the patient's relevant medical history.

Videofluoroscopic Measurements

Pre- and post-treatment VFSS from the single patient were compared to evaluate swallowing function. TIMS-DICOM review software was used for VFSS measurement collection. Frame-by-frame analysis was used to gather kinematic, pixel-based, and timing measures, as well as visual-perceptual analysis for PAS scoring and LVC completeness.

The cervical spine (C2–C4 length) was not used as a scalar for pixel-based area or distance measures due to concerns over the changes in spinal length no longer aligning with patient factors, such as height. Therefore, all measurements were normalized utilizing the patient’s tracheal width as described by Steele et al. [9], rather than the C2–C4 distance. The tracheal width using the posterior and anterior boundaries of the vocal folds was measured in pixels and then doubled to approximate the C2–C4 distance in pixels, as tracheal width is estimated to correspond with half of the C2–C4 distance [9].

Measurements were then either expressed as a percentage of this derived, squared C2–C4 distance (C2–C42) (i.e., residue), or in cervical units (i.e., peak hyoid displacement), where appropriate. A complete summary of all measures gathered along with definitions attached as online supplementary material (File A). All timing, kinematic, and pixel-based measures were averaged across six bolus types – teaspoon and individual cup sips of nectar (approximately IDDSI level 2), teaspoon and individual cup sips of thin barium (approximately IDDSI level 1), pudding (IDDSI level 4), and mechanical soft, mixed consistency (approximately IDDSI level 6). Only bolus conditions that were present in both pre- and post-VFSS conditions were extracted and analyzed.

Statistical Analysis

SPSS Statistics (v. 28) was used for all statistical analyses. Though our research design was not a prospective single subject research design (i.e., using an ABA treatment paradigm), we utilized similar reporting metrics used in other single subject designs [10, 11] for this study. Timing outcomes were analyzed descriptively by calculating Cohen’s d. For consistency, peak hyoid position, UES maximum opening, and all residue measures were also analyzed descriptively using Cohen’s d. All measures were averaged across bolus trials to provide an overall description of impairment pre- and post-treatment. Within bolus means are provided descriptively to contextualize the patient's performance in various swallow conditions for clinical value. Cross-tabulations were performed to assess associations of PAS scores and LVC completeness with pre- and post-treatment conditions at the bolus level (i.e., every swallow was included, not averaged) and reported using χ2. For cross-tabulations, α was set to 0.05 for detecting a significant difference.

Post-Treatment Effects on Swallowing Function

The patient’s post-treatment VFSS was conducted at the beginning of September 2022, approximately 2 weeks of post-treatment. Based on the findings from the VFSS, the patient was recommended to continue on his pre-treatment diet level (IDDSI level 6 – soft and bite sized with no mixed consistencies; and IDDSI level 0 – thin liquids) but with ongoing required compensatory strategies of utilizing repeat swallows and a supraglottic swallow.

There were clinically meaningful effects present for LVC duration from pre- to post-treatment, suggested by a large treatment effect of d = 0.96. A small treatment effect was observed on time-to-LVC (d = 0.26) from pre- to post-treatment. For kinematics including peak hyoid position and UES opening, there were large treatment effects of peak hyoid displacement (d = 6.24) (Fig. 3) and UES opening (d = 3.39), respectively.

Fig. 3.

Changes in peak hyoid displacement from pre-treatment to post-treatment.

Fig. 3.

Changes in peak hyoid displacement from pre-treatment to post-treatment.

Close modal

Negative effect sizes were also present, including a small negative effect pre- to post-treatment in vallecular residue (d = −0.38), a medium negative effect in pyriform residue (d = −0.53), and a large negative effect in other pharyngeal residue (d = −1.66). The result was an overall negative effect of total pharyngeal residue from pre- to post-treatment (d = −1.37). Finally, there was a large negative effect of pre- to post-treatment on pharyngeal area at maximal constriction (d = −1.94).

Significant associations were found between treatment condition and PAS scores (p < 0.05) and LVC completeness (p < 0.05), suggesting a significant improvement in airway safety and degree of airway closure post-treatment. A full breakdown of effects for timing and kinematic measures can be found in Tables 1 and 2, respectively.

Dysphagia Presentation and Patient-Centered Factors

There is limited extant literature on the comprehensive manifestation of dysphagia in patients post-ACDF. Our findings are consistent with and contribute to the literature available, particularly in regard to reduced airway closure, reduced UES opening, poor pharyngeal constriction, and an increase of pharyngeal residue [5, 12‒15], as well as increases in airway invasion across multiple consistencies [1, 5].

However, our findings of substantially atypical swallowing physiology differ from recent findings from Ziegler et al. [7] when categorizing this patient as having chronic post-operative dysphagia. Ziegler and colleagues [7] found that in post-ACDF patients >2 months post-surgery, swallow function was not significantly different from control subjects. Our findings in the unique course of this subject highlight the likely individuality in post-operative condition. As examples in this patient, the level of the cervical hardware, post-operative healing and subsequent scarring at the surgical site in the pharynx, and non-surgical-related health conditions all may contribute to the post-operative course of chronic dysphagia. As such, normal swallow function post-ACDF surgery, while likely, should not be assumed. This supports the need for longitudinal follow-up and assessment, if needed, in these patients.

Despite the evidence provided from this patient, the underlying cause of the impairment, as in all patients, is multifaceted. There are several factors to consider regarding his chronic dysphagia and its generalizability to similar patients. A primary reason may be the presence of hardware in the cervical spinal region. While it is well documented that pharyngeal wall thickness post-ACDF is increased in the acute stages, this patient’s significant time post-surgery leaves acute inflammation or edema an unlikely possibility. Miles et al. [5] postulate that neuromuscular, sensory, and vascular injury sustained during the surgery may persist in individuals’ post-surgery because of the surgical procedures and techniques involved as it may affect patients individualistically.

As an example, in the current study, a narrowed pharyngoesophageal segment was highlighted at the same level of the cervical hardware both clinically and during data extraction at baseline and post-treatment VFSS. There was also a thickening of the pharynx in the middle-inferior region of the pharynx (Fig. 2). These factors likely contributed to the unique structural and mechanical insufficiencies seen in this patient that resulted in reduced UES opening for bolus transport to the esophagus, reduced pharyngeal constriction, and impaired epiglottic inversion.

While positive treatment effects were found, not all parameters improved after the treatment period. All parameters of pharyngeal residue and PhAMC performed worse on average post-treatment. However, the worsening in pharyngeal residue post-treatment may not be due to the treatment itself but rather to remaining surgical and patient-centered factors that evolved outside of treatment. The patient experienced a complex course post-NMES treatment. This included reported instances of odynophagia in July of 2022 with low-grade pain during swallowing across 2 days. No sources of pain could be identified via orofacial exam. The patient did not report any additional instances of odynophagia throughout the remainder of therapy. After his post-treatment VFSS, the patient chose to end dysphagia therapy without pursuing additional sessions at this time. In October of 2022, the patient underwent an endoscopic procedure due to new onset odynophagia and blood in his saliva, 1-month post-treatment. A biopsy was performed for tongue base and bilateral vallecular masses. In November of 2022, a PET scan confirmed oropharyngeal cancer as cervical lymph node metastases. He underwent surgery and chemoradiation as a treatment regimen. The exact staging, surgical procedures, or margins taken for the surgical treatment were not available.

Post-Treatment Outcomes Using NMES: Chronic Dysphagia and Implementation

While dysphagia post-ACDF is expected to resolve, a subset of this post-surgical population likely experiences chronic dysphagia, as presented in this study. These results present the improvements using this modality in a single subject with chronic dysphagia post-ACDF. For this patient, dysphagia caused by underlying physiological impairment in hyolaryngeal function improved substantially. However, implementing NMES as a treatment modality requires an understanding of its purpose and how to appropriately implement it based on muscular, structural, and swallowing physiology [16]. Individualistic patient factors such as their time post-surgery, routine swallow studies to assess function, and the underlying impairment if present should also be considered. We intend for the placement and parameters provided (Instrumentation above) to serve as guides for clinicians in the appropriate implementation of NMES for this patient population as a potential treatment modality when appropriate, as these parameters are rooted in principles of small muscle function for those muscles of the anterior neck [17, 18].

The findings presented here are not without limitations, and interpretation of the results should be done with caution. The nature of an uncontrolled single subject study inherently limits generalizability to a broad scope of dysphagia etiologies or NMES uses. However, we believe the detailed therapy documentation including NMES parameters and session duration provide a clear intervention description. Additionally, NMES itself has several limitations regarding treatment applications for dysphagia. From a physiological perspective, NMES even when applied to the suprahyoids using appropriate physiological parameters is not designed to treat all physiological impairments causing dysphagia. To date, the available evidence suggests NMES may improve hyolaryngeal excursion and time-to-LVC. However, other manifestations of dysphagia such as poor pharyngeal constriction leading to increased pharyngeal residue, lack evidence of being improved by dysphagia therapy using NMES. NMES is also contraindicated in patients immediately post-ACDF to allow internal and external structures and incisions to heal. It is therefore not clinically recommended to begin dysphagia therapy post-ACDF using NMES immediately if the patient experiences dysphagia during the acute post-operative stages.

Second, this patient endured a complex post-treatment sequence, elements of which may have impacted therapeutic progress. We acknowledge that outcomes reflect the ceiling of the patient at that point in time and may not be generalizable to a large-scale therapeutic trial. However, we believe this highlights the true clinical nature and course that many patients take during and after clinical care. Regardless, the individualistic course that many patients may experience is vital to consider in the context of the presentation and needs of the patient. Clinicians should carefully evaluate the entire course of the patient, from pre- to post-operation, utilize follow-up assessment such as VFSS, and interpret the findings of the VFSS to appropriately determine the best course of treatment and management. For example, NMES may not be a feasible or necessary approach if certain physiological impairments are not present, such as decreased hyolaryngeal excursion. The clinical management of this particular patient was therefore centered around their dysphagia presentation, and patient-centered factors such as goals, tolerance, and therapy intensity were individualized. While these factors ultimately limit generalizability, these findings are important for practicing clinicians who may encounter similar situations in their real-world clinical practice to implement patient-centered care and decision-making when considering NMES.

This study protocol was approved by the Institutional Review Board at Western Michigan University, Approval No. 21-09-13, and complies with all relevant institutional and ethical requirements. Written informed consent was obtained from the patient for publication of the details of their medical case and any accompanying images and protected under an established HIPAA agreement with the primary investigator’s laboratory and the providing therapists.

The authors have no conflicts of interest to report.

No funding was received for this project.

All authors contributed equally to the conception, development, and finalization of the manuscript.

Data for this study are not publicly available due to concerns of patient confidentiality but are available from the corresponding author (M.D.) upon reasonable request.

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