Treatment of acquired nasopharyngeal stenosis using a removable silicone stent

CT features of confirmed nasopharyngeal stenosis in 12 cats

OBJECTIVES

CT is frequently utilised in the assessment of upper respiratory tract disorders. The aim of the present study was to further describe the CT features in cats with confirmed nasopharyngeal stenosis (NPS).

METHODS

CT images of the heads of cats with NPS confirmed via retroflex nasopharyngoscopy between 2011 and 2023 were retrospectively reviewed to describe the imaging features of NPS and other concurrent findings.

RESULTS

In total, 12 cats were included. All but one cat had pre- and post-contrast images available. All CT studies demonstrated focal, abrupt narrowing of the nasopharyngeal lumen by a variably thickened, homogeneous, soft tissue attenuating band. One cat appeared to have two separate NPS, giving a total of 13 NPS. All NPS were located in the caudal third of the nasopharynx, which resulted in a marked reduction in the luminal cross-sectional area. The narrowing of the nasopharyngeal lumen was either concentric (11/13) or lateral-to-lateral (2/13). Mild homogeneous contrast enhancement of the soft tissue band was observed in 8/11 cats (73%). The soft palate was focally dorsally deviated at the NPS site in 8/12 cats (67%) and was best seen in the sagittal plane. Other concurrent findings included non-contrast-enhancing soft tissue attenuating material within the nasal cavity (7/12) and tympanic bullae (4/12), and mild medial retropharyngeal lymphadenomegaly (2/12).

CONCLUSIONS AND RELEVANCE

The most frequently observed CT features in cats with NPS are marked, focal, abrupt narrowing of the nasopharyngeal lumen by a mildly contrast-enhancing soft tissue band in the caudal third of the nasopharynx and focal deviation of the soft palate dorsally at the NPS site. Identifying any of these CT features in the presence of compatible clinical signs should prompt further evaluation with retroflex nasopharyngoscopy to confirm the diagnosis of NPS and to direct appropriate treatment.

Patient-specific 3D-printed nasopharyngeal stents in dogs: a cadaveric pilot study

Background

Currently available treatment options for nasopharyngeal stenosis and imperforate nasopharynx in dogs and cats are fraught with complications and failures.

Objective

To develop patient-specific nasopharyngeal stents using 3D-printed molds and to assess placement and fit of stents within the nasopharynx.

Animals

Six canine cadavers.

Methods

Patient-specific nasopharyngeal silicone stents were generated using 3D-printed molds based on CT scans. A placement protocol was developed. Post-placement, goodness of fit within the nasopharynx was evaluated and compared to currently used methods. Mechanical properties of silicone stents were compared to catheter-based and nitinol stents.

Results

Development and placement of stents was successful in all six cadavers. Silicone stents offered stiffness (force required for compression, N) and post-load deformation comparable to nitinol stents (1.8-6.2 vs. 1.2-3.3 N and 0.02-0.08 vs. 0.01-0.14 mm, respectively). Patient-specific stents offered superior goodness of fit in the nasopharynx (81-90%) compared to bilateral red rubber catheters (16.2-33.8%).

Conclusion

Development and placement of patient-specific stents using 3D printed molds was successful in all six cadavers. The novel stents exhibited similar mechanical properties and superior goodness of fit compared to commercially available stents, potentially offering a better alternative to commercially available stents. Further investigation is needed in animals with nasopharyngeal stenosis to determine efficacy and to assess utility in live patients.

Nasopharyngeal stenosis in cats: a retrospective study of 21 cases comparing endoscopic and surgical treatment (2018-2022)

OBJECTIVES

Feline nasopharyngeal stenosis (NPS) is an uncommon disease in cats. The aim of this study was to compare the outcome with endoscopic and surgical treatments.

METHODS

In this retrospective study, medical records were searched for cases of NPS and cases were divided into three groups: endoscopic treatment (balloon dilation); surgical treatment; or no treatment. Data are presented as median and range. Success rates and length of post-procedure corticosteroid treatment were compared between the two treated groups.

RESULTS

A total of 21 cases were included: 10 males and 11 females (median age 6.7 years, range 0.5-14.4). Clinical signs at the time of initial presentation included permanent stertor (19/21), increased respiratory efforts (9/21), nasal discharge (9/21) and cough/reverse sneezing (6/21) with a duration in the range of 3-60 months. Diagnosis was based on endoscopy (21 cases) and CT (19 cases). In total, 12 cases were treated with endoscopic balloon dilation; 11 cases demonstrated a complete resolution of clinical signs (two cats had two dilations) and one case showed incomplete improvement after one balloon dilation but was successfully treated surgically. Eight cats were treated surgically (including one cat that was originally treated with balloon dilation), including seven cases with complete resolution of clinical signs and one case with a rostral NPS that failed to respond. Two cats were not treated and are still alive more than 3 years after diagnosis. The success rate was not different between the endoscopic (11/12) and surgically treated cases (7/8) (P = 0.85). The outcome was considered excellent in most of the cases as 18/23 procedures were successful, at least until the medium term, and 15/18 treated cats had no clinical signs of minimal stertor at follow-up.

CONCLUSIONS AND RELEVANCE

This preliminary study suggests that minimally invasive endoscopic treatment of NPS has a high success rate and should be attempted in all cases with perforate stenotic membranes. When not achievable, extended palatoplasty can be recommended as a good alternative.

Case report: Combination technique of balloon dilation, membrane excision, and topical mitomycin C for the treatment of nasopharyngeal stenosis in a cat

A two-year-old neutered male Turkish Angora cat presented with respiratory signs, including chronic snoring sounds and dyspnea with open-mouth breathing. Nasopharyngeal stenosis (NPS) was diagnosed based on endoscopy and computed tomography (CT). An attempt was made to break down the membrane, causing stenosis in the nasopharynx through balloon dilation using a valvuloplasty balloon dilation catheter (12 mm × 3 cm) and retroflexed endoscope. The balloon size was selected according to the identified diameter of the stenotic site on nasopharyngeal CT images. The balloon was inflated with radiographic contrast medium and maintained for 2 min; the similar procedure was repeated four additional times. The stenotic membrane was excised after balloon dilation. Topical Mitomycin C (MMC) was then administered to the stenotic region. After 2 weeks, an additional MMC application was repeated to prevent recurrence. The cat remained free of clinical signs without recurrence for 12 months after the most recent procedure. In this study, effective treatment results were obtained using a combination of balloon dilation, membrane excision, and topical MMC for membranous nasopharyngeal stenosis in a cat.

Imperforate nasopharynx in a cat successfully treated with an extended palatoplasty

Case summary

A female intact domestic shorthair kitten was evaluated at 8 months of age for bilateral mucopurulent nasal discharge, stertor, open-mouth breathing and difficulty eating. Imperforate nasopharynx (INP) was diagnosed on oronasal examination under anesthesia. An extended palatoplasty was performed and resulted in resolution of the clinical signs.

Relevance and novel information

The extended palatoplasty procedure is relatively simple and very similar to the correction of soft palate elongation in brachycephalic dogs. It does not require special equipment and materials; therefore, it represents a viable, more readily available and cost-effective option for the treatment of INP. To the author's knowledge, this is the first case of INP that has been treated with extended palatoplasty.

Retrospective study of 540 cats with respiratory diseases in Japan (2003-2020)

BACKGROUND

Few epidemiological studies on respiratory medicine and the relationship between clinical signs and various respiratory diseases in cats have been reported.

OBJECTIVES

This retrospective study aimed to investigate the prevalence and breed predisposition to feline respiratory diseases in Japan and determine the association between clinical signs, duration and type of respiratory diseases.

METHODS

The medical records of cats with feline respiratory diseases were examined to obtain information on age, sex, breed, final diagnosis, clinical signs and duration. The odds ratios (ORs) and 95% confidence intervals were calculated to evaluate breed predispositions. Mann-Whitney U, Kruskal-Wallis and Dunn's tests were used to assess the duration of clinical signs.

RESULTS

This study included 540 cats with 615 respiratory diagnoses. The American Shorthair breed was predisposed to bronchopneumonia (BP; OR: 5.0) and pulmonary tumour (PT; OR: 3.6), while the Russian Blue breed exhibited a predisposition to inflammatory lower airway diseases (OR: 3.4), BP (OR: 6.1) and interstitial lung diseases (OR: 11.1). Similarly, the Scottish Fold breed displayed predisposition to PTs (OR: 5.8). The duration of clinical signs among nasal diseases, nasopharyngeal diseases and lower tracheal/bronchial and pulmonary diseases differed significantly (p = 0.001, p = 0.012, p < 0.0001, respectively).

CONCLUSIONS

The results suggest that some popular breeds in Japan are predisposed to feline respiratory diseases, especially the American Shorthair, Russian Blue and Scottish Fold breeds. The characteristics of occurrence, clinical signs and duration of each disease will aid in diagnosing, treating, preventing and elucidating the pathophysiology of feline respiratory disease.

Investigation of a retroesophagoscopic approach to nasopharyngoscopy as an alternative to the conventional retroflexed endoscopic approach for selected indications in feline cadavers and client-owned cats

OBJECTIVE

To describe a retroesophagoscopic approach (ROSA) to nasopharyngoscopy and compare it with the conventional retroflexed endoscopic approach (REA).

ANIMALS

36 feline cadavers and 2 client-owned cats with nasopharyngeal disorders.

PROCEDURES

36 veterinarians participated in the experimental portion of the study involving feline cadavers. Each veterinarian performed the ROSA and REA to nasopharyngoscopy on a feline cadaver once, attempting to identify and biopsy 2 landmarks (soft palate and choanae) with each approach while time was recorded. Numeric scales were used to measure perceived ease of use and image quality for both techniques. Data were compared between approaches by an independent statistician. The ROSA approach was also used as part of the diagnostic workup for the 2 client-owned cats.

RESULTS

35 of the 36 (97%) veterinarians were able to identify and biopsy both landmarks using the ROSA, whereas 21 (58%) veterinarians were able to visualize both landmarks using the REA and 19 (53%) successfully biopsied the landmarks. Image quality for the soft palate was scored higher with the ROSA (median score, 7.5/10) than with the REA (4.5/10). The ROSA was fast and easy to perform. This approach was also successfully performed in the 2 client-owned cats with nasopharyngeal disorders, with no complications reported.

CONCLUSIONS AND CLINICAL RELEVANCE

The ROSA was found to be a fast, effective, and easy alternative endoscopic technique for assessment of the nasopharynx in cats. This approach may allow use of various instruments that could be relevant for interventional procedures. However, the ROSA was also invasive and should be considered for diagnostic and therapeutic purposes for selected indications only when REA is unsuccessful.

Extended palatoplasty as surgical treatment for nasopharyngeal stenosis in six cats

OBJECTIVE

To describe the use of extended palatoplasty as treatment of caudal nasopharyngeal stenosis in cats.

MATERIALS AND METHODS

CT was used to confirm the diagnosis in cats with clinical signs consistent with nasopharyngeal stenosis. Extended palatoplasty rostral to the tonsils using monopolar electrocautery allowed simultaneous removal of the caudal soft palate together with the stenotic area. Cats were re-evaluated 2 weeks postoperatively. Telephone interview was used to obtain long-term follow-up.

RESULTS

Six domestic shorthair cats were diagnosed with nasopharyngeal stenosis, with clinical signs of snoring (n=4), stertor (n=4), nasal discharge (n=3) and sneezing (n=1). CT scan identified a soft-tissue stricture at the level of the caudal nasopharynx in all cats. Other abnormalities included bilateral rhinitis (n=3), retropharyngeal adenomegaly (n=2), unilateral sinusitis (n=1) and bilateral otitis externa with unilateral otitis media (n=1). Excision of the caudal soft palate and the entire stenotic soft-tissue membrane was successful in all six cats. No pre-, intra- or postoperative complications were observed. Short-term outcome revealed clinical improvement in all cases. Long-term outcome revealed no recurrence of clinical signs in four cats. In one cat, occasional sneezing was reported. One cat died 1 month postoperatively for reasons unrelated to the respiratory condition.

CLINICAL SIGNIFICANCE

Extended palatoplasty was an effective technique to treat caudal nasopharyngeal stenosis and provide improvement of clinical signs without postoperative complications in all cases.

Balloon dilation for the treatment of nasopharyngeal stenosis in seven cats

Objectives

The objective of this study was to evaluate the effectiveness of balloon dilation for the treatment of nasopharyngeal stenosis in cats.

Methods

The medical records of seven cats with nasopharyngeal stenosis treated with balloon dilation were reviewed. The most common presenting clinical signs included upper airway noise, sneezing, nasal and/or ocular discharge. All seven cats were confirmed to have nasopharyngeal stenosis via nasopharyngeal endoscopy and were treated with balloon dilation under endoscopic guidance.

Results

All seven cats had acceptable short-term control (median 14 days) of clinical signs after the procedure. Two of six cats had successful long-term control (median 34 days) of clinical signs after one balloon dilation and an additional 2/6 cats had acceptable long-term control of clinical signs after a second balloon dilation procedure. The most significant complication of balloon dilation was the recurrence of stenosis.

Conclusions and relevance

The findings of this study indicate that balloon dilation is a safe and effective treatment option for the relief of clinical signs associated with nasopharyngeal stenosis in cats. Multiple procedures may be necessary for the best chance of long-term success.