Introduction

Foreign bodies of the external canal are relatively common in human medicine and are generally reported in children.^1,2 In contrast, middle ear foreign bodies are rare,^1–3 the most commonly retrieved middle ear foreign bodies being cotton wool and silicone impression material.^1–7 In cats, the most common cause of otitis media is nasopharyngeal polyps, with other causes described as neoplasia and extension of external ear canal infection into the middle ear.^8,9 Ventral bulla osteotomy (VBO) is a commonly performed surgical procedure in cats for the management of middle ear diseases.^9–11 This invasive procedure has significant inherent potential complications including persistent disease, Horner syndrome, vestibular disease, and facial nerve paralysis.^10–13 To avoid complications and improve epithelial lining curettage, recent studies have been published describing the use of a rigid endoscope to explore the middle ear via a lateral or ventral approach.^14–16 We present here a case of otitis media secondary to a foreign body, successfully managed by endoscopy-assisted foreign body retrieval and curettage.

Case Report

A 7 yr old neutered male shorthair was presented to The Alliance veterinary clinic for progressive loss of balance, left head tilt, and positional nystagmus over the preceding week. The referring veterinarian had evaluated the cat 4 days before and gave him one injection of dexamethasone (0.1 mg/kg, subcutaneously). A history of gunshot injury was reported by the owner many years ago. On presentation, the cat was bright and alert, and the general physical examination revealed a left sternal systolic murmur (grade 5/6), a left head tilt, and positional nystagmus. A complete blood count and a biochemistry panel were performed and revealed no abnormalities. Preoperative echocardiography was proposed and declined by the owners. The cat was induced with propofol^a (4 mg/kg IV and as needed) and midazolam^b (0.2 mg/kg IV) and was intubated and maintained on isoflurane. A computed tomographic^c examination with contrast^d enhancement of the head was performed and revealed a round metallic foreign body of 4 mm diameter in the left tympanic cavity (Figure 1A) with two additional metallic fragments (<2 mm diameter) (Figure 1B–D). The main foreign body was noted in ventromedial component of the bulla (Figure 1A) behind the septum. The additional fragments were located within the dorsolateral lumen of the bulla before the septum and in the caudolateral wall of the bulla behind the septum hypotympanum (Figure 1B–D). A soft tissue/fluid attenuation within the left tympanic cavity was also noted (20 Hounsfield units before and after contrast enhancement). The vertical and horizontal canals were normal. Otitis media secondary to a chronic foreign body was diagnosed.

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Surgical removal of the foreign body was discussed and accepted by the owners. An informed consent was obtained from the pet owners before the surgery. The patient described in this study was clinically managed according to contemporary standards of care. A dose of IV dexamethasone (dexamethasone^e 0.1 mg/kg IV) was administered before the surgery. The cat was anaesthetized with the same protocol as described previously, intubated, and maintained on isoflurane. Methadone (comfortan^f 0.2 mg/kg IV q 4 hr) was administered during surgery and for 24 hr after surgery.

With the cat placed in dorsal recumbency, a 0.5 cm skin incision was made over the left tympanic bulla, blunt dissection was carefully performed with Metzenbaum scissors, and the bulla was identified. The periosteum covering the ventral part of the bulla was stripped away with a periosteal elevator. A 0.045-in K-wire was used to create three contiguous holes in triangle formation in the ventral aspect of the bulla. A 2.4 mm 30° rigid endoscope^g was inserted into the bulla without a protective sheath to avoid a larger bone hole. The bulla was thoroughly flushed with sterile saline. A large amount of pus was noted, and the first small foreign body was identified (Figure 2). The endoscope was gently withdrawn near the opening and endoscopic forceps^h were inserted alongside the scope to retrieve this foreign body. The bony septum separating the ventromedial and dorsolateral compartments of the bulla was opened with a 0.045-in K-wire and an endoscopic forceps under endoscopic assistance. The main fragment and the second fragment in the wall of the bulla were located and retrieved with endoscopic forceps in a similar manner. An endoscopic sample of mucosa withdrawn with the endoscopic forceps and one of the two foreign body fragments were sent for bacteriological analysis. The entire bulla was inspected and flushed after removal of the bony septum. Curettage was gently performed under endoscopic visualization with a curette inserted alongside the scope. Residual debris was removed by irrigation. The surgical wound was closed routinely. A postoperative head radiograph was performed to confirm the absence of residual metallic fragments. The cat recovered from surgery and anesthesia without complications. The cat was discharged the following day with a tapering dose of corticosteroids (prednisoloneⁱ starting at the dose of 0.5 mg/kg per os q 24 hr for 4 days, then 0.25 mg/kg per os q 24 hr for 2 days and 0.25 mg/kg per os every other day for two intakes) for 7 days total. Antibiotics (cephalexin^j 15 mg/kg per os q 12 hr) were administered until the results of bacteriologic analysis were obtained and adapted as needed.

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Bacteriological evaluation of the sample revealed Stenotrophomonas maltophilia with sensitivity to amoxicillin/clavulanic acid. Current antibiotic therapy (cephalexin) was discontinued and amoxicillin/clavulanic acid^k (15 mg/kg per os q 12 hr) was prescribed for 10 additional days.

Two weeks postoperatively, the cat still had a mild left head tilt, but the loss of balance was resolved. Two months postoperatively, a residual head tilt was noted. All other neurological signs were resolved. At 5 mo postoperatively, the cat was evaluated for an emergency (blood in the oral cavity and pneumothorax, unknown origin); the neurologic examination was normal without evidence of head tilt. The owner reported that the animal had normal behavior before the accident.

Discussion

Endoscopic instrumentation is widely used in veterinary and human minimally invasive soft tissue, orthopedic, and, more recently, neurologic surgery because of several reported advantages.^17,18 Among those, increased visibility, magnification, and illumination in areas that are typically difficult to access have been reported.^13–18 Several cadaveric studies have been recently published describing the access and anatomy of the tympanic bulla under endoscopic assistance.^14–16 This technique may be particularly useful for cats, in which the tympanic bulla is divided into two compartments (dorsolateral and ventromedial compartments) by an incomplete septum, making it difficult to access and visualize completely.¹² Particularly, using a 30° endoscope rather than a 0° endoscope improves field of view and allows more thorough evaluation when work is being performed in a confined space such as the tympanic cavity.^14,16

Otitis media is a common cause of peripheral vestibular disease in dogs and cats. The known causes of middle ear disease in cats are inflammatory polyps, neoplasia, and extension of external ear canal infection into the middle ear.^8–12 In young cats, the most common cause of otitis media is nasopharyngeal polyps.^8,9,12 In this case, a unique cause of otitis media was described. Otitis can cause vestibular dysfunction by two mechanisms. Bacteria that infect the middle ear can produce toxins that inflame the labyrinth (otitis media), or bacteria may invade the labyrinth itself (otitis interna), often as an extension of otitis media. Common bacterial isolates include Staphylococcus spp., Streptococcus spp., and Pseudomonas spp. In the case presented here, Stenotrophomonas maltophilia was isolated. Stenotrophomonas maltophilia is one of the less known drug-resistant bacteria that can cause challenging infections.¹⁹ Surgery to provide drainage and remove infected tissue may be necessary in patients refractory to medical therapy. A mild head tilt, facial paralysis, or Horner syndrome may persist, despite effective therapy, because of permanent damage to neural structures. In this case, surgery was indicated to remove the foreign material, resolve the infection, and allow neurologic recovery.

Horner syndrome is a common complication reported in 43–97% of cats treated by VBO and could persist long term in fewer than 25% of cases.^11,13,20,21 Other complications described after this procedure are permanent or temporary facial nerve paralysis, recurrence of otitis in 0–33% of cases, persistent infection, or vestibular signs.^10–13 A recent study found that cats treated with single-stage bilateral VBO were significantly more likely to have severe respiratory complications and surgery-related death than cats treated with other VBO procedures.²² Video-assisted VBO data are unavailable for comparison with traditional VBP, but it could be interesting to investigate the impact of endoscopic assistance on the complication and mortality rates.

In our case, endoscopic magnification was very helpful to avoid neural structure and to remove the maximum of the epithelial lining as much as possible with a minimal approach (less than 1 cm). No recurrence or Horner syndrome was noted during the long-term follow-up in this case.

Conclusion

To the authors’ knowledge, this is the first case report of video-assisted middle ear foreign body removal in a cat. A limited ventral approach to the tympanic bulla with intraoperative endoscopy allowed good visualization of the foreign material, facilitating safe retrieval. Furthermore, the technique permitted good epithelial lining removal and allowed avoidance of neurological structures. In accordance with the purported benefits of minimally invasive procedures as compared with traditional surgery, the patient recovered quickly with complete remission of neurological signs and excellent long-term outcomes without recurrence 5 mo after surgery. Middle ear foreign body should be considered as a differential diagnosis of vestibular syndrome in outdoor cats, particularly cats living in rural areas. Video-assisted retrieval and surgical debridement appears to be a safe and effective treatment.