Inflammatory Aural Polyps

Inflammatory aural polyps are benign, pedunculated or sessile, soft tissue growths that arise from the mucosal lining of the middle ear, auditory tube (Eustachian tube), or tympanic cavity, and may extend into the external ear canal through a perforated tympanic membrane or via the auditory tube into the nasopharynx. They are composed of granulation tissue with a variable inflammatory infiltrate, often associated with chronic otitis media. In veterinary medicine, these polyps are most commonly diagnosed in cats, but can also occur in dogs. They are typically unilateral but can be bilateral in up to 10% of cases. The condition is characterized by clinical signs referable to the ear, such as otorrhea, head shaking, and pain, and may also cause upper respiratory signs if nasopharyngeal extension occurs. Surgical management is the mainstay of treatment, with options including traction-avulsion, ventral bulla osteotomy, and lateral bulla osteotomy, depending on the extent of the disease. Complete surgical excision is often curative, but recurrence can occur if the inflammatory process within the middle ear is not adequately addressed.

The exact etiology of inflammatory aural polyps is not fully understood, but they are believed to arise as a result of chronic inflammation of the middle ear mucosa, often secondary to bacterial or viral infections. In cats, chronic otitis media is frequently associated with upper respiratory infections caused by feline herpesvirus, calicivirus, or Mycoplasma species. The inflammation leads to hyperplasia of the mucosal epithelium and proliferation of granulation tissue, which can form a polypoid mass. In some cases, the polyps may be congenital, arising from remnants of the branchial arches or the first pharyngeal pouch. Iatrogenic factors, such as repeated ear flushing or inappropriate use of ear cleaners, may also contribute to mucosal irritation and polyp formation. Additionally, anatomical factors, such as a short and wide auditory tube in brachycephalic breeds, may predispose to ascending infections from the nasopharynx. The polyps are not neoplastic, but rather represent a chronic inflammatory response, and they do not metastasize.

Inflammatory aural polyps are most commonly diagnosed in young adult cats, with a median age of 1 to 2 years, but they can occur in cats of any age. There is no strong breed predisposition, but some studies suggest a higher incidence in domestic shorthair cats. Dogs are less commonly affected, but when they are, it is often in the context of chronic otitis externa and media. No sex predilection has been consistently reported. The condition is relatively uncommon, but it is one of the most frequent causes of otitis media in cats. In a retrospective study of cats with otitis media, inflammatory polyps were identified in approximately 30% of cases. Bilateral involvement occurs in about 10% of cases, and concurrent nasopharyngeal polyps are seen in up to 50% of cats with aural polyps. The condition can affect both indoor and outdoor cats, with no clear environmental risk factors identified.

The pathophysiology of inflammatory aural polyps involves a chronic inflammatory response within the middle ear cavity. The initial insult is often an infection, which may ascend from the nasopharynx via the auditory tube or descend from the external ear canal through a ruptured tympanic membrane. The inflammation leads to edema, hyperemia, and infiltration of the submucosa with inflammatory cells, including lymphocytes, plasma cells, and neutrophils. This chronic inflammation stimulates fibroblast proliferation and angiogenesis, resulting in the formation of granulation tissue. Over time, this granulation tissue can become organized into a polypoid mass, which is covered by respiratory epithelium or stratified squamous epithelium. The polyp may remain confined to the middle ear or extend through the tympanic membrane into the external ear canal, or through the auditory tube into the nasopharynx. The presence of the polyp can obstruct the auditory tube, leading to further accumulation of inflammatory exudate and perpetuating the cycle. Additionally, the polyp can cause pressure necrosis of surrounding structures, including the tympanic membrane and ossicles, leading to conductive hearing loss. In severe cases, the polyp may erode into the inner ear, causing vestibular signs, or extend into the surrounding bone, leading to osteomyelitis.

Several factors may predispose an animal to the development of inflammatory aural polyps. Anatomical factors, such as a short, wide, and horizontally oriented auditory tube in brachycephalic breeds, may facilitate ascending infections from the nasopharynx. Chronic upper respiratory infections, particularly in cats, are a significant risk factor, as they can lead to otitis media via the auditory tube. Immunosuppression, whether due to viral infections such as feline leukemia virus (FeLV) or feline immunodeficiency virus (FIV), or due to chronic corticosteroid use, may increase susceptibility to infections and subsequent polyp formation. Environmental factors, such as poor ventilation and overcrowding in catteries, may increase the risk of respiratory infections. Additionally, iatrogenic factors, such as aggressive ear cleaning or inappropriate use of ear medications, can cause trauma to the ear canal and tympanic membrane, predisposing to infection and polyp formation. Finally, a history of recurrent otitis externa or media is a significant risk factor, as the chronic inflammation can lead to mucosal hyperplasia and polyp formation.

Clinical signs of inflammatory aural polyps vary depending on the location and extent of the polyp. Common signs include chronic or recurrent otorrhea, which may be purulent or serosanguinous, head shaking, ear scratching, and pain on palpation of the ear. The external ear canal may be erythematous and swollen, and a polyp may be visible on otoscopic examination as a smooth, pink to red, pedunculated mass. If the polyp extends into the nasopharynx, clinical signs may include stertor (noisy breathing), nasal discharge, sneezing, dysphagia, and voice change. In severe cases, the polyp may cause obstruction of the nasopharynx, leading to respiratory distress. Vestibular signs, such as head tilt, nystagmus, and ataxia, may occur if the polyp erodes into the inner ear. Facial nerve paralysis (drooping of the ear, lip, and eyelid) may also be observed if the polyp involves the tympanic bulla and compresses the facial nerve. In chronic cases, hearing loss may be evident. On physical examination, the tympanic membrane may be bulging or ruptured, and a mass may be palpable in the nasopharynx on oral examination. Neurological examination may reveal deficits consistent with peripheral vestibular disease or facial nerve dysfunction.

Differential diagnoses for inflammatory aural polyps include: 1) Chronic otitis externa and media: This is the most common differential, and it may be distinguished by the presence of a polyp on otoscopic examination, but chronic otitis can also cause mucosal hyperplasia that mimics a polyp. 2) Neoplasia of the ear canal or middle ear: Tumors such as ceruminous gland adenocarcinoma, squamous cell carcinoma, and fibrosarcoma can present as masses in the ear. These are more common in older animals and may be invasive, with cytology and histopathology differentiating them from inflammatory polyps. 3) Nasopharyngeal polyps: These are similar to aural polyps but arise primarily in the nasopharynx and may extend into the middle ear. They are often seen in young cats and may cause upper respiratory signs. 4) Cholesteatoma: This is a keratin-filled cyst-like lesion in the middle ear, which can cause bone lysis and neurological signs. It is rare in animals but should be considered if imaging shows bone destruction. 5) Otitis interna: This is an inner ear infection that can cause vestibular signs, but it is usually not associated with a visible mass. 6) Foreign body in the ear canal: A grass awn or other foreign body can cause chronic inflammation and a secondary polypoid reaction. 7) Granulomatous disease: Fungal infections, such as cryptococcosis, can cause granulomatous masses in the ear. 8) Polyps associated with chronic otitis due to drug-resistant bacteria or yeast: These may be similar in appearance but are distinguished by culture and response to treatment.

The diagnostic algorithm for inflammatory aural polyps begins with a thorough history and physical examination, including a complete otoscopic examination of both ears. If a polyp is visualized, it is important to assess its size, location, and attachment. However, otoscopic examination may be limited by pain, discharge, or stenosis of the ear canal, and may require sedation or general anesthesia. The next step is imaging of the tympanic bullae. Radiography of the skull (open-mouth or oblique views) can reveal increased soft tissue opacity within the bulla, thickening of the bulla wall, or bone lysis, but it is less sensitive than advanced imaging. Computed tomography (CT) is the imaging modality of choice, as it provides detailed assessment of the bullae, middle ear, and surrounding structures, and can identify soft tissue masses, fluid accumulation, and bone changes. Magnetic resonance imaging (MRI) may be used if there is suspicion of intracranial extension or if soft tissue contrast is needed. If a polyp is identified, a biopsy or fine-needle aspiration may be performed for cytology and histopathology to confirm the diagnosis and rule out neoplasia. In cases where the polyp extends into the nasopharynx, a thorough oral examination and possibly nasopharyngoscopy should be performed. Additionally, bacterial culture and sensitivity of the middle ear exudate should be obtained to guide antimicrobial therapy. In cases with neurological signs, a complete neurological examination and possibly cerebrospinal fluid analysis may be indicated.

Laboratory findings in animals with inflammatory aural polyps are often nonspecific. Complete blood count (CBC) may reveal mild leukocytosis or neutrophilia due to chronic inflammation or secondary infection. Serum biochemistry profile is usually within normal limits, but may show elevations in globulins due to chronic antigenic stimulation. In cats, testing for feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) is recommended, as these may be underlying predisposing factors. Cytological examination of the ear discharge or middle ear exudate may reveal inflammatory cells, bacteria, and yeast. Bacterial culture and sensitivity should be performed on samples obtained from the middle ear, as this is essential for guiding antimicrobial therapy. In cases where the polyp is biopsied, histopathology will show granulation tissue with a mixed inflammatory infiltrate, and the surface epithelium may be respiratory or squamous. Special stains, such as Gram stain or fungal stains, may be used to identify infectious agents. Coagulation panel is not routinely indicated unless surgery is planned and there is a history of bleeding disorders.

Imaging plays a crucial role in the diagnosis and surgical planning of inflammatory aural polyps. Radiography of the tympanic bullae is often the first imaging modality used. Open-mouth or oblique views can demonstrate increased soft tissue opacity within the bulla, thickening of the bulla wall, and in chronic cases, sclerosis or lysis of the bone. However, radiography has limited sensitivity and specificity, and may not detect small polyps or subtle changes. Computed tomography (CT) is the preferred imaging modality, as it provides high-resolution, cross-sectional images of the bullae and surrounding structures. CT findings typically include a soft tissue attenuating mass within the tympanic bulla, which may extend into the external ear canal or nasopharynx. There may be fluid accumulation within the bulla, thickening of the mucosa, and in chronic cases, bone remodeling or lysis. CT is also useful for assessing the extent of the polyp and for surgical planning, as it allows for evaluation of the bulla anatomy and the relationship of the polyp to vital structures such as the facial nerve and internal carotid artery. Magnetic resonance imaging (MRI) may be used if there is suspicion of intracranial extension or if better soft tissue contrast is needed. MRI can differentiate between fluid and soft tissue masses, and can identify inflammatory changes in the brain or meninges. Ultrasonography is not commonly used for this condition, but may be used to guide aspiration of the bulla. In cases where the polyp extends into the nasopharynx, nasopharyngoscopy can be used for direct visualization and biopsy.

Cytological examination of fine-needle aspirates or impression smears from inflammatory aural polyps typically reveals a mixed population of inflammatory cells, including neutrophils, lymphocytes, plasma cells, and macrophages, along with variable numbers of epithelial cells. The presence of bacteria or yeast may be noted, and special stains can be used to identify infectious agents. However, cytology is not definitive for the diagnosis of a polyp, as it may be similar to that of chronic otitis. Histopathology is the gold standard for diagnosis. On histopathological examination, inflammatory aural polyps are characterized by a core of fibrovascular tissue covered by respiratory epithelium (pseudostratified ciliated columnar epithelium) or, in some cases, stratified squamous epithelium. The stroma is edematous and contains a dense infiltrate of inflammatory cells, predominantly lymphocytes and plasma cells, with fewer neutrophils and macrophages. There may be areas of hemorrhage, necrosis, and fibrosis. The polyp is typically well-circumscribed and non-encapsulated. In contrast to neoplastic masses, the cells are well-differentiated and there is no evidence of invasion or metastasis. Special stains, such as Masson's trichrome for collagen and periodic acid-Schiff (PAS) for mucopolysaccharides, may be used to highlight the stroma and epithelial components. Immunohistochemistry may be used to differentiate polyps from other tumors, but is rarely necessary.

The treatment of inflammatory aural polyps is primarily surgical, with the goal of complete excision of the polyp and resolution of the underlying middle ear inflammation. The choice of surgical approach depends on the extent of the polyp and the presence of middle ear disease. For polyps that are confined to the external ear canal or are visible through the tympanic membrane, traction-avulsion may be attempted. This involves grasping the polyp with forceps and gently pulling it out through the ear canal. However, this technique is associated with a high recurrence rate (up to 50%) because it does not address the underlying middle ear disease. For polyps that extend into the middle ear or are associated with significant otitis media, a ventral bulla osteotomy (VBO) is the preferred surgical approach. VBO provides excellent exposure of the tympanic bulla and allows for complete removal of the polyp and any inflammatory debris. The procedure involves making an incision over the ventral aspect of the bulla, elevating the surrounding muscles, and creating a window in the bulla using a burr or osteotome. The contents of the bulla are then curetted and flushed, and the polyp is removed. The bulla is left open to drain, and the incision is closed in layers. In dogs, a lateral bulla osteotomy (LBO) may be performed, which involves approaching the bulla through a lateral incision. This approach is less invasive but provides less exposure. Postoperative care includes systemic antibiotics, analgesics, and anti-inflammatory medications. In some cases, topical ear medications may be used. If the polyp extends into the nasopharynx, it may be removed via traction-avulsion through the oral cavity, but this is often combined with VBO to address the middle ear component. Medical management alone is not curative, but may be used to control inflammation and infection prior to surgery. This may include systemic antibiotics, corticosteroids, and ear cleaning. However, surgery is the definitive treatment.

The prognosis for inflammatory aural polyps is generally good to excellent with appropriate surgical treatment. Complete excision via ventral bulla osteotomy is associated with a low recurrence rate, reported to be less than 10% in most studies. Traction-avulsion alone has a higher recurrence rate, up to 50%, due to incomplete removal of the inflammatory tissue. The prognosis is worse if there is extensive bone lysis, neurological involvement, or if the polyp is associated with a chronic, resistant infection. In cats, the prognosis is generally favorable, with most animals showing resolution of clinical signs within 2 to 4 weeks after surgery. However, some cats may develop chronic otitis or vestibular signs postoperatively, which may be temporary or permanent. The overall success rate, defined as resolution of clinical signs, is reported to be around 80-90% for VBO. Complications such as Horner's syndrome, facial nerve paralysis, and vestibular signs may occur in up to 20% of cases, but these are often transient. Recurrence of the polyp is possible if the underlying inflammation is not controlled, so long-term follow-up is recommended.

Postoperative follow-up for inflammatory aural polyps is essential to monitor for recurrence and complications. The animal should be re-examined 2 weeks after surgery to assess wound healing and to remove sutures if non-absorbable sutures were used. At this time, an otoscopic examination should be performed to evaluate the ear canal and tympanic membrane. The owner should be instructed to monitor for signs of recurrence, such as head shaking, ear scratching, or discharge. A recheck examination at 4 to 6 weeks postoperatively is recommended, and may include imaging (CT or radiographs) to assess the bulla for any remaining soft tissue or fluid. If the animal had neurological signs preoperatively, a neurological examination should be repeated to assess improvement. Long-term follow-up, at 6 months and 1 year, is recommended to ensure no recurrence. In cases where the polyp was associated with chronic otitis, ongoing management of the ear disease may be necessary, including regular ear cleaning and topical medications. The owner should be advised to avoid water in the ear and to monitor for any signs of infection. If vestibular signs persist beyond 2 weeks, further evaluation may be needed.

Clinical pearls: 1) Always perform a thorough otoscopic examination under general anesthesia, as polyps may be missed in the awake animal. 2) Use CT imaging preoperatively to assess the extent of the polyp and to plan the surgical approach. 3) When performing a ventral bulla osteotomy, be careful to identify and preserve the hypoglossal nerve and the internal carotid artery, which lie near the bulla. 4) Use a surgical headlamp and magnification to improve visualization during surgery. 5) After removing the polyp, flush the bulla copiously with sterile saline to remove all inflammatory debris. 6) Consider placing a drain in the bulla if there is significant infection, to allow for postoperative drainage. 7) In cats, always check for nasopharyngeal polyps, as they may be present concurrently. 8) Postoperative use of systemic antibiotics and anti-inflammatory drugs is important to control infection and inflammation. Pitfalls: 1) Traction-avulsion alone is associated with a high recurrence rate and should be reserved for small, pedunculated polyps with no evidence of middle ear disease. 2) Failure to perform a bulla osteotomy in cases of middle ear involvement will likely lead to recurrence. 3) Incomplete removal of the polyp due to poor visualization can lead to recurrence. 4) Damage to the facial nerve during surgery can occur if the nerve is not identified and protected. 5) Postoperative hemorrhage can occur if the bulla is not adequately packed or if the animal is not properly monitored. 6) Overlooking concurrent nasopharyngeal polyps can lead to persistent clinical signs. 7) Inadequate postoperative care, such as not administering antibiotics or not cleaning the ear, can lead to secondary infections and poor outcomes.

Perioperative drug protocols for inflammatory aural polyps are based on Plumb's Veterinary Drug Handbook. Prophylactic antibiotics: Cefazolin (22 mg/kg IV) administered 30 minutes before surgical incision, and repeated every 90 minutes during surgery. Postoperative antibiotics: Amoxicillin-clavulanate (13.75 mg/kg PO q12h) for 7-14 days, or based on culture and sensitivity results. Analgesics: Preoperative opioid, such as hydromorphone (0.05-0.1 mg/kg IV) or buprenorphine (0.01-0.02 mg/kg IV), followed by postoperative opioids as needed. Nonsteroidal anti-inflammatory drugs (NSAIDs): For dogs, carprofen (2.2 mg/kg PO q12h) or meloxicam (0.1 mg/kg PO q24h) for 3-5 days. For cats, meloxicam (0.05 mg/kg PO q24h) for up to 3 days, or robenacoxib (1-2 mg/kg PO q24h) for up to 5 days. Local anesthesia: A regional block of the auriculotemporal and great auricular nerves with bupivacaine (1-2 mg/kg) may be performed for postoperative analgesia. Anti-inflammatory corticosteroids: Prednisone (0.5-1 mg/kg PO q24h) may be used postoperatively to reduce inflammation, but should be used with caution in cats. Antiemetics: If vestibular signs are present, maropitant (1 mg/kg IV or PO q24h) may be used. Ear cleaning: Postoperative ear flushing with a sterile saline solution or a dilute chlorhexidine solution (0.05%) may be performed, but should be done gently to avoid trauma. In cases of confirmed bacterial infection, antibiotics should be adjusted based on culture and sensitivity. For fungal infections, such as Malassezia, topical or systemic antifungal agents may be indicated.

The veterinary literature on inflammatory aural polyps is limited but provides valuable insights. A landmark study by Kapatkin et al. (1990) evaluated the outcomes of ventral bulla osteotomy in cats with middle ear polyps and reported a recurrence rate of 10% and a complication rate of 20%, with Horner's syndrome being the most common complication. Another study by Trevor et al. (1993) compared traction-avulsion and ventral bulla osteotomy and found that traction-avulsion had a significantly higher recurrence rate (50%) compared to VBO (10%). A more recent study by Anderson et al. (2016) evaluated the use of CT in the diagnosis and surgical planning of aural polyps and found that CT was superior to radiography in identifying the extent of the disease. A consensus statement from the ACVS (American College of Veterinary Surgeons) recommends ventral bulla osteotomy as the treatment of choice for inflammatory aural polyps with middle ear involvement. The use of perioperative antibiotics and analgesics is supported by standard surgical principles. Overall, the evidence supports surgical excision as the definitive treatment, with VBO providing the best outcomes. Further research is needed to evaluate the long-term outcomes and to identify risk factors for recurrence.