Chronic otitis externa/media with total ear canal ablation and bulla curettage in a North American bison (Bison bison).

An adult female North American bison (Bison bison) with a chronic otitis externa/media of the right ear was examined because of a 4-mo history of intermittent anorexia, apparent painful behavior, and auricular discharge from the right ear. Computerized tomography (CT) demonstrated osteolysis of the tympanic, petrous, and squamous aspects of the temporal bone with soft tissue replacement and sclerosis of the right bulla. A total ear canal ablation with bulla curettage was performed, and cefazolin-impregnated polymethacrylate beads were left within the right bulla and the remnant temporal bone. Six months after the surgery, the bison had no clinical signs of otitis media.     

Total ear canal ablation and lateral bulla osteotomy in the dog

One hundred total ear canal ablation/lateral bulla osteotomy procedures were performed in 71 dogs over a four year period. The main indication for surgery was advanced disease of the aural canal or middle ear resulting from prolonged inflammatory disease of the outer ear. Complications of surgery included facial nerve injury, inner ear injury, retroglenoid vein haemorrhage and wound dehiscion. The incidence of complications (29 per cent) was, however, substantially lower than has previously been recorded following this procedure. Meticulous dissection technique and increasing familiarity with the procedure were thought to be responsible for lower complication rates than have previously been recorded. Surgery was considered to have resolved the original aural condition in 92 per cent of cases and only infrequently resulted in complete loss of hearing function.     

Partial ear canal ablation and lateral bulla osteotomy in rabbits

Six lop rabbits were presented with clinical signs of otitis media or externa. The presence of disease was confirmed by computerized tomography examination, with two rabbits suffering from bilateral disease. The rabbits were anaesthetized and underwent surgery of the affected bulla. Rabbits with bilateral disease had a minimum of 2 weeks between procedures. A single vertical incision was made over the base of the vertical canal, which was bluntly dissected free from surrounding tissue. The ventral portion of the vertical canal was removed and a lateral bulla osteotomy was performed. The mucosa at the base of the dorsal vertical canal was apposed and the aural cartilage sutured to form a blind‐ending pouch open at the pretragic incisure. Histopathological samples taken from the dorsal margin of the vertical canal yielded subtle and non‐specific changes in the six samples submitted. All rabbits were discharged within 48 hours of surgery. The cosmetic outcome was excellent with animals retaining visually normal aural anatomy. The partial ear canal ablation/lateral bulla osteotomy procedure is quick and has a good cosmetic result when performed in rabbits.     

Total ear canal ablation combined with lateral bulla osteotorny in J the cat

Eighteen total ear canal ablations combined with lateral bulla osteotomy (TECA/LBO) procedures were performed in 15 cats over a period of 30 months. The indications for surgery included neoplastic disease, ceruminous gland adenocarcinoma of the horizontal canal or middle ear (10 ears), squamous cell carcinoma extending from the pinna (four), polyps emanating from the middle ear (three), and chronic unremitting middle ear disease (one). Complications associated with surgery included facial paralysis (seven cases), facial neuropraxia (four), Horner's syndrome (three), and wound dehiscion (one). Eleven cats were alive and disease-free six months after the surgery. The results indicate that the major indication for TECA/LBO in the cat is neoplastic disease involving the ear. Unlike the procedure in the dog, for which the usual indication is benign end-stage ear disease, neurological complications are common despite meticulous surgical dissections. In addition, the postoperative prognosis is guarded because of malignant disease in many cases.     

Wound contamination and antimicrobial susceptibility of bacteria cultured during total ear canal ablation and lateral bulla osteotomy in dogs.

OBJECTIVE: To detect contamination of wound sites from surgical handling of excised tissues during total ear canal ablation and lateral bulla osteotomy in dogs, and to compare susceptibility of bacterial isolates to cefazolin with susceptibility to other antimicrobial agents. DESIGN: Prospective clinical study. ANIMALS: 13 dogs. PROCEDURE: Dogs were treated surgically for otitis externa and media via total ear canal ablation and lateral bulla osteotomy. Specimens for aerobic bacterial culture were obtained from SC tissue immediately following skin incision, tissues excised from the osseous bulla (after transection of the horizontal ear canal and lateral bulla osteotomy), and from SC tissue prior to skin closure. Antimicrobial susceptibility of bacterial isolates to various antibiotics was determined by use of a broth dilution assay. RESULTS: There was a significant association between isolation of Streptococcus canis and Escherichia coli from specimens from the osseous bulla and specimens from the SC tissues prior to skin closure, indicating contamination of the SC tissues during surgery. Seventy percent of bacterial isolates were susceptible to cefazolin. CLINICAL IMPLICATIONS: Measures to limit bacterial contamination resulting from tissue handling during total ear canal ablation and lateral bulla osteotomy are necessary. Bacteriologic culture of tissue of the osseous bulla and determination of antimicrobial susceptibility are recommended. Administration of cefazolin alone may not be efficacious for antimicrobial prophylaxis.     

Effect of tympanic cavity evacuation and flushing on microbial isolates during total ear canal ablation with lateral bulla osteotomy in dogs

OBJECTIVE: To evaluate differences in bacterial numbers, identity, and susceptibility in samples obtained from the tympanic cavity on entry (preflush) and after evacuation and lavage (postflush) and assess perioperative and empiric antimicrobial selection in dogs that underwent total ear canal ablation (TECA) with lateral bulla osteotomy (LBO) or reoperation LBO. DESIGN: Prospective clinical study. ANIMALS: 34 dogs. PROCEDURE: TECA with LBO or reoperation LBO was performed on 47 ears. Pre- and postflush aerobic and anaerobic samples were obtained from the tympanic cavity. Isolates and antimicrobial susceptibility patterns were compared. RESULTS: Different isolates (31/44 [70%] ears) and susceptibility patterns of isolate pairs (6/44 [14%] ears) were detected in pre- and postflush samples from 84% of ears. Evacuation and lavage of the tympanic cavity decreased the number of bacterial isolates by 33%. In 26% of ears, bacteria were isolated from post-flush samples but not preflush samples. Only 26% of isolates tested were susceptible to cefazolin. At least 1 isolate from 53% of dogs that received empirically chosen antimicrobials postoperatively was resistant to the selected drugs. Anaerobic bacteria were recovered from 6 ears. CONCLUSIONS AND CLINICAL RELEVANCE: Accurate microbiologic assessment of the tympanic cavity should be the basis for selection of antimicrobials in dogs undergoing TECA with LBO. Bacteria remain in the tympanic cavity after evacuation and lavage. Cefazolin was a poor choice for dogs that underwent TECA with LBO, as judged on the basis of culture and susceptibility testing results.     

Bulla curettage for chronic otitis media and interna in dogs.

In a series of 10 clinically affected and 6 clinically normal dogs, the technique of bulla curettage via the external ear canal, after lateral ear resection, was evaluated. In 5 of the 10 dogs with chronic otitis media and interna, the head carriage became normal 2 to 8 weeks after surgery and remained so for at least 18 months; 4 other dogs improved, but the improvement was either temporary or incomplete. In the clinically normal dogs, postsurgical complications were minimal; the tympanic membrane healed completely in 4 of the 6 dogs.     

Comparison of microbial isolates and susceptibility patterns from the external ear canal of dogs with otitis externa

Otic exudate was obtained from 33 dogs with otitis externa for cytopathology and culture. Two samples were taken from the same location in the external ear canal, for a total of 100 samples. Thirty-six (36%) samples isolated only a single organism, of which 21 (21%) were Malassezia spp. Two organisms were present in 23 (23%) of the samples. Cultures of the two samples agreed in 40 (80%) of the 50 pairs. Cytopathology agreed with culture results only 68% of the time. Cytopathology and culture may not be as definitive as previously assumed because of apparent variability of the microbial population within the external canal.     

Pull-through technique for vertical canal ablation for the treatment of otitis externa in dogs and cats

An alternative technique to ablate the vertical segment of the external auditory meatus, applicable to dogs and cats, is described. The results of this surgery in 11 dogs and one cat are compared with those in seven dogs using the traditional ablation procedure.     

FC-46 Methicillin-resistant Staphylococcus intermedius organisms from the vertical ear canal of dogs with end-stage otitis externa

Different mite species generally found on animals may temporarily also infest humans. Consequently, these arthropods may be responsible for pruritic skin reactions that are often misdiagnosed. Mite dermatitis caused by the tropical rat mite Ornithonyssus bacoti occurs in several small mammals and rodents under tropical and temperate climatic conditions. According to various observations in Germany, O. bacoti appears in wild rodents more frequently than previously thought. In most cases, symptoms of mites are recognized only when they attack humans, but the diagnosis of rat mite dermatitis requires identification of the parasite, which is more likely to be found in the environment than on the hosts' skin itself. Here, five different outbreaks from Bavaria are reported. A clinical example is the case of a 23-year-old medical student and several other residents inhabiting a rat- and mouse-infested house in Munich. The arthropods originally came from an Italian restaurant and surrounding facilities. Mites were found in large numbers in the students' flat. The patient was suffering from severe itching and papular urticaria. He consulted a dermatology clinic complaining of a pruritic dermatitis of 2-weeks duration. Dermatitis was misdiagnosed as allergy and treatment with an anti-inflammatory agent was unsuccessful. Eradication of rodents and treatment of the house with a pyrethroid were performed to prevent reinfestation. Ornithonyssus bacoti is a periodic haematophageous parasite and spends a relatively short time on the host. Causal therapy with antiparasitic agents on human patients is not necessary. If indicated, treatment should be symptomatic.
Funding: Self-funded.     

Study of lipid in the ear canal in canine otitis externa with Malassezia pachydermatis

An epidemiological investigation of 120 canine otitis externa cases in 1,370 dogs was done on the incidence rate, ear pinna shapes, breeds and their relationships. Eighty-five cases (12.6%) in 672 dogs with pendulous ears and 35 cases (5.0%) in 698 dogs with erect ears had otitis externa, and the difference between them was significant (P<0.05). Ninety-five auditory cerumen specimens were cultured for Malassezia pachydermatis (M. pachydermatis) and analyzed for concentrations of major fatty acids. Although rates of cases positive for M. pachydermatis in both ear pinna shapes were almost the same, i.e. 55.2% in the pendulous group and 53.6% in the erect group, the average total fatty acid level of the pendulous ear group was significantly (P<0.05) higher than that in the erect ear group after dismissing extraordinary levels in the Siberian husky. Isolated M. pachydermatis strains were examined for the effects of fatty acid supplementation on their growth. The majority of the strains utilized fatty acids and grew faster in fatty acid supplemented broth. These results suggest that M. pachydermatis, the predominant causative agent of canine otitis externa, prefers the auditory canal of dogs with lipid-rich earwax and grows fast, but growth strongly depends upon the canine breed.     

Subtotal ear canal ablation in 18 dogs and one cat with minimal distal ear canal pathology

A modified technique for performing total ear canal ablations is described. This technique requires less dissection than the standard technique and maintains a portion of the distal vertical ear canal. Subtotal ear canal ablations were performed in 18 dogs and one cat for the treatment of otitis externa or masses of the horizontal ear canal. Animals with otitis externa had minimal involvement of the distal ear canal. Dermatological problems associated with the remaining ear canal and pinnae occurred in eight animals and resolved with medical management. Normal ear carriage was maintained in all animals with erect ears. Further investigation is required before the procedure can be recommended as a treatment for otitis externa not caused by masses or anatomical abnormalities of the horizontal ear canal in dogs with pendulous ears.