Veterinary Surgery, 19, 2, 162-1 66, 1990
Chronic Otitis Externa and Otitis Media Treated by Total Ear Canal Ablation and Ventral Bulla Osteotomy in Thirteen Dogs N.J. H. SHARP, BVetMed, MVM, MRCVS, DiplornateACVS Ventral bulla osteotomy was combined with total ear canal ablation for the treatment of chronic otitis externa and otitis media in 13 dogs (14 ears) that had been refractory to medical and surgical treatments. Resolutionof disease occurred in 11 dogs (12 ears). One dog with unilateral disease underwent a second operation before achieving a good result. One dog was euthanatized for persistent unilateral disease after three surgical procedures. The recurrence of disease in these two dogs (15%) was associated with remnants of ear canal integument within the osseous horizontal canal or tympanic bulla. Facial paralysis occurred in four dogs (31°/,) and there were no complications in eight dogs (62%). This technique shows no advantage over lateral bulla osteotomy combined with total ear canal ablation for the treatment of chronic otitis externa and otitis media.
was first described as a A treatment for canine otitis externa in 1958.’ When the condition is complicated by otitis media, ablation BLATION OF THE E A R CANAL
alone may be inadequate because it does not drain the middle ear and fistulation may r e ~ u l t . Otitis ~ - ~ media has been reported to complicate up to 52% of chronic otitis externa cases.’ When both otitis externa and otitis media are present, middle ear drainage should accompany ablation.‘ Of the techniques described for surgical drainage of otitis media, the most useful are lateral and ventral bulla osteotomies.6-8 Both have been combined with ablation of the ear canal as treatment for concomitant intractable otitis externa and Long-term results have been reported for ablation alone and combined with lateral bulla o ~ t e o t o m y . ~ .In ~ , this ’ study, those results are compared with long-term results of ear canal ablation combined with ventral bulla osteotomy in dogs with otitis externa and otitis media.
’
Materials and Methods Thirteen dogs with severe intractable otitis externa without neoplasia were studied. All had been treated medically, surgically, or both, for 1 to 4 years without success. Additional lesions in six of the dogs included fa-
cial abscesses, facial sinus tracts, no patent opening to the auditory meatus on the affected side, facial paralysis, and otitis interna on the affected side (Table 1). Examinations were conducted with the dogs under general anesthesia. Dorsoventral skull and “open mouth” rostrocaudal radiographic projections were used to evaluate the horizontal ear canals, petrous temporal bones, and tympanic bullae. Radiographic findings of bulla osteitis were interpreted as otitis media. Samples for bacteriologic examination were aspirated from the tympanic bulla with a 6 inch blunt metal (Spreull) needle.5 When this was not possible, a fine-needle aspirate was obtained from the facial abscess (dogs 5 and 12), or the facial sinus was cultured (dogs 2, 8, and 9). Culture of the tympanic cavity was subsequently performed at surgery in these five dogs. The diagnosis of otitis media was based on absence of an intact tympanic membrane as shown by otoscopic examination, and by the uninterrupted passage of a 6 inch blunt metal needle to the medial wall of the bulla.’’ To substantiate active inflammatory disease, additional criteria of otitis media were based on radiologic, histopathologic, or bacteriologic examination of the middle ear (Table 2). Unilateral surgery was performed in 12 dogs. Dog 11 underwent bilateral surgery with a 4 month interval between procedures. A neurologic examination was per-
From the Veterinary Hospital, University of Liverpool, Liverpool, England. The author thanks Drs. C. E. Harvey and P. G. Bedford for their advice and helpful criticism in the preparation of this manuscript. Reprint requests: N.J.H. Sharp, MRCVS, North Carolina State University, College of Veterinary Medicine, Department of Companion Animal and Special Species Medicine, 4700 HillsboroughSt, Raleigh, NC 27606.
162
163
SHARP TABLE 1. Signalrnent and Presenting Features in Thirteen Dogs with Otitis Externa and Otitis Media
Dog No. 1 2 3 4 5 6
Age (yrs)
9 10 2
2 10 4
Breed
Duration of Signs (YW
Affected Ear
German shepherd W ~ terrier W WHW terrier German shepherd English setter German shepherd
1.5 3 1.25 1.5 1 3
Right Left Left Left Right Left
Previous Treatment
VCA Bulls lavage and LWR
Bulls lavage, ventral osteotomy and LWR Bulls lavage and VCA LWR
4 3.5
German shepherd Standard poodle
4 1.25
Left Left
9
9
Crossbred
1
Right
10 11
7 5.5
German shepherd Basset hound
2.5 2
12
4
Labrador retriever
3
Left Left Right Left
Attempted total canal ablation without bulla osteotorny Bulls lavage and LWR Bilateral bulla lavage and LWR LWR
13
4
German shepherd
2
Left
LWR and bulla lavage
WHW-West
highland white; VCA-vertical
-
Bulls lavage and LWR
a
7
Additional Lesions
Facial sinus No opening to horizontal canal
Facial abscess for 1 month
Facial sinus; no opening to horizontal canal Facial sinus; no opening to horizontal canal
Abscess for 1 yr, facial paralysis and otitis interna for 1 month duration; no opening to horizontal canal
-
canal ablation; LWR-lateral wall resection
formed on days I and 7. Owners were asked about the dog's condition at least 1 year after the last surgical procedure.
Si1 rgicul T d i niqiic. Systemic antibiotics selected from bacteriologic sensitivity results were administered parenterally I hour before surgery. External ear canal ablation was performed first."' Total ear canal ablation was performed in dogs 2 and 5. In the I 1 dogs with previous ear canal surgery, any remaining horizontal canal was excised. Only the annular cartilage could be identified in dog 9 because of a previous attempt at canal ablation. During surgery, the parotid salivary gland and facial nerve were identified and protected by gentle ventral retraction. Sinus tracts were debrided with care to protect the facial nerve. Before wound closure, the epithelial lining ofthe bony canal was thoroughly curetted. Each dog was repositioned in dorsal recumbency and the neck was prepared aseptically for surgery. The tympanic bulla was exposed by a ventral approach.x A large opening was made into the tympanic cavity with an osteotome. Any tissue or debris within the cavity was removed for bacteriologic or histopathologic examination, or both. Curettage was performed carefully to avoid the dorsal and medial aspects of the tympanic cavity, to pre-
vent vestibular damage. The surgical site was flushed with physiologic saline solution and the wound was closed with chromic gut in the deep layers and monofilament nylon in the skin. In the five dogs with soft tissue swelling or sinus formation, a Penrose drain was placed in the tympanic cavity and exteriorized adjacent to the ventral incision. Antibiotics were administered orally for 2 weeks. In dogs with Pseirdomonas infection, gentamicin was administered intravenously for 6 days and amoxicillin orally for 2 weeks. Results The tympanic membrane was absent and there was at least one other feature diagnostic of otitis media in all 14 ears (Table 2). Otoscopy was not possible in dogs 3 , 5, 8, 9, and 12 because of occlusion of the horizontal or the vertical canal. Otitis media was confirmed radiographically in 1 1 dogs by lysis or sclerosis of the tympanic bullae or petrous temporal bones. or by increased radiopacity within the tympanic cavity. In one dog the bulla was filled with radiopaque material of bone density after a previous bulla osteotomy. Other radiographic features included calcification of the ear canal cartilages (4 dogs) and occlusion of the canal lumen (5 dogs). In three dogs, including one ear in dog 1 I , there were no radiographic signs of otitis media.
164
EAR CANAL ABLATION AND VENTRAL BULLA OSTEOTOMY TABLE 2. Results of Evaluationand Surgery (Continues)
Dog No.
Otoscopic/Surgical Findings
Radiologic Findings
Bacteriologic Findings
Histopathologic Findings
FOIIOW-UP
1
Stenosis and ulceration of horizontal canal
Sclerosis of PTB; tympanic bulla radiopacity
Pseudomonas sp Staphylococcus aureus
Fibrous connective tissue with a ciliated epithelial lining
1 yr, no recurrence
2
Hyperkeratosis and ulceration of vertical canal; sinus draining from horizontal canal
Bulla radiopacity
S. aureus
Chronically inflamed granulation tissue
Euthanasia at 3 mos due to CRF; temporary VII paralysis for 1 wk
3
Occluded horizontal canal
Bulla lysis; occluded horizontal canal
Sterile
Chronically inflamed granulation tissue
1 yr, no recurrence
4
Stenosis and ulceration of horizontal canal
Bulla lysis and radiopacity
Pseudomonas sp and Escherichia coli
Chronically inflamed granulation tissue
4 yrs, no recurrence
5
Facial abscess occluding and communicating with horizontal canal
Sclerosis of PTB, calcified and occluded horizontal canal
Proteus sp and E. coli
No tissue present in bulla
2 yrs, no recurrence VII paralysis permanent
6
Ulceration of horizontal canal; poor LWR
Radiodense tympanic bulla; calcified horizontal canal
Pseudomonas sp and E coli
Not done
3.5 yrs, no recurrence
7
Hyperkeratosis of horizontal canal
Normal
E. coli
No tissue present in bulla
3 yrs, no recurrence
8
Sinus draining from horizontal canal
Bulla lysis and radiopacity; occluded horizontal canal
S. aureus
No tissue present in bulla
3 yrs, no recurrence VII and XI1 paralyses permanent
9
Sinus draining from horizontal canal
Bulla lysis, sclerosis of PTB; occluded horizontal canal Normal
Proteus sp, Staphylococcus epidermis
Chronically inflamed granulation tissue
3 yrs, no recurrence
Pseudomonas sp
No tissue present in bulla
4 yrs, no recurrence
10
Stenosis of horizontal canal; poor LWR
11L
Intense erythema of horizontal canal
Sclerosis of left PTB, bulla radiopacity
S. aureus, Proteus sp
No tissue present in bulla
5 yrs, no recurrence
11R
Intense erythema of horizontal canal
Right normal
As above plus Bacteriodes SP
No tissue present in bulla
5 yrs, no recurrence
Pscvidomonas spp were zultured from four dogs. Tympanic bulla tissue from seven dogs was interpreted histologically as chronically inflamed granulation tissue. In dog 1 , this tissue was lined by ciliated epithelium. In five dogs. no tissue was found within the bulla. The bulla
from dog 6 was tilled with a homogeneous material grossly resembling bone. In five dogs, there was communication between the horizontal canal and either a facial abscess (dogs 5 and 12) or a sinus tract (dogs 2, 8, and 9). In four dogs. com-
165
SHARP TABLE 2. (Continued)
Dog No. 12
Facial abscess occluding and communicating with horizontal canal
Bacteriologic Findings
HistopathologicFindings
FoIIOW-UP
Bulla radiopacity; calcified and occluded horizontal canal Not done
S. aureus Pasturella sp
Chronically inflamed granulation tissue
Resolution of all signs, then recurrence of abscess after 3 wks
As above
As above with acute inflammatory tissue
Recurrenceof signs after 2 wks
Recurrenceof abscess 2 wks after surgery
As above with lysis of bulla
As above
Acutely inflamed granulation tissue
Recurrence of signs after 4 wks
Recurrence of abscess 4 wks after surgery
Not done
Not done
Stratified squamous epithelium with cystic glandular elements
Euthanasia
Stenosis and ulceration of horizontal canal
Sclerosis of PTB, bulla lysis, calcified horizontal canal
S. aureus
Chronically inflamed granulation tissue
VII paralysis permanent
Facial sinus 4 wks after surgery
As above
As above
As above plus areas containing cystic glandular elements
1 year, no recurrence
Recurrenceof abscess 3 wks after surgery
13
Radiologic Findings
Otoscopic/Surgical Findings
PTB-petrous
temporal bone; CRF-chronic
renal failure; VII-facial
munication occurred between the annular and auricular cartilages; in dog 5, the exact site was not determined. The abscesses and fistulae were immediately ventral to the horizontal canal. The median follow-up period was 3 years. There was no recurrence of infection or sinus formation and the owners were satisfied with the results in dogs 1 to 1 I . Dog 2 had no recurrence ofear disease 3 months after surgery, but was euthanatized because of chronic renal failure. Surgical complications included facial nerve paralysis in dogs 2, 5, and 13, and combined facial and hypoglossal paralysis in dog 8. The paralyses remained permanent in dogs 5 , 8 , and 13 but caused no additional complications during the follow-up period. In dog 12, presenting signs of facial paralysis and otitis interna abated after the first surgery. All dogs were subjectively deaf in the affected ear. Dog 1 1 , which had bilateral surgery, responded to low-frequency noises. Clinical signs recurred and a draining facial sinus developed 4 weeks after surgery in dog 13. The middle ear was reexplored via a lateral approach and several remnants of integument were found attached to the osseous horizontal canal. The remnants were removed, the site was irrigated as before, and a Penrose drain was placed before closure. There has been no recurrence for 1 year since the second operation.
nerve; LWR-lateral
wall resection; XII-hypoglossal
nerve.
Abscess formation recurred 3 weeks after surgery in dog 12. A second ventral bulla osteotomy incision was made and additional granulation tissue was removed from the bulla. Signs recurred 2 weeks later and the area was reexplored via a lateral approach. Granulation tissue was curetted from the bulla but no canal integument could be identified. Clinical signs recurred 4 weeks later and the dog was euthanatized. At postmortem examination, there was severe osteomyelitis ofthe petrous temporal bone. Deeply embedded within the bone were remnants of ear canal integument, consisting of stratified squamous epithelium and cystic glandular structures surrounded by acutely inflamed granulation tissue. Discussion All dogs in this series had severe otitis externa and at least two features consistent with a diagnosis of otitis media. Conservative therapy, including lateral ear resection in most ofthe dogs, had been unsuccessful. In such cases, a combination of ear canal ablation and bulla osteotomy is the recommended treatment.' The most common postoperative complications in this series were deafness, facial nerve paralysis, and recurrence of ear disease. Hypoglossal nerve paralysis occurred in one dog, which has been reported elsewhere
EAR CANAL ABLATION AND VENTRAL BULLA OSTEOTOMY
after ventral bulla osteotom y.* The deafness, also noted elsewhere,* was subjective and would require clarification by electrodiagnostic techniques. The persistence of hearing ability in a dog after bilateral surgery has been reported previously.* Facial paralysis occurred in 3 1% of the dogs in this series and was permanent in 23%. Corresponding rates of permanent facial paralysis after lateral bulla osteotomy combined with ear canal ablation were 33%,' 1770,'' and 8%.' The facial paralysis seen in the current series occurred in three of five dogs in which the nerve was entrapped in fibrous tissue that resulted from extension of infection outside the ear canal. Postoperative facial paralysis was documented previously in two dogs with facial sinuses arising from the horizontal canal.'.I4 Attempts to isolate the facial nerve surgically in this situation should be minimized. Postoperative facial paralysis described in a previous report required enucleation in one dog and continuous artificial tears in another.2 The three permanent facial nerve deficits in this series caused the dogs no problems during observation periods of 1 to 3 years. In another study, five dogs with postoperative facial paralysis also had no associated adverse effects. ' ' The presence of Pseztdumunus spp in the middle ear was not associated with a poor outcome. The two dogs that required reoperation had epithelial and glandular tissue from the external ear canal within the bulla. The integument found deeply embedded within the petrous temporal bone in dog 12 was presumably pushed there during the initial curettage of the bony horizontal canal. Tissues removed from the tympanic bullae were identified histologically as granulation tissue. In samples from humans with otitis media, mature fibrous tissue or immature granulation tissue also is the most frequent finding. I In a previous report, total ear canal ablation alone was complicated by recurrence or prolonged drainage in 23% and wound infection in 2790 of 30 cases.2 In the same report. one ( 17%) of six dogs that underwent lateral bulla osteotomy combined with ear canal ablation had recurrence of infection.' In two other reports of lateral bulla osteotomy combined with ear canal ablation the recurrence rates were 3 (12%)" of 26 dogs and I ( 8 % ~of) ~13 dogs. The overall rates of recurrence or persistence of drainage after the lateral approach appear to be lower than the 15% found in the current series using the ventral
approach.2.'.' ' Valid comparison is difficult, partly because the clinical features and criteria for case selection or follow-up are not available for one of these reports.' The apparent advantage of the lateral technique may be because removing the ventral aspect of the osseous horizontal canal allows more accurate curettage of the ear canal integument. Another advantage of lateral bulla osteotomy is that the patient does not need to be repositioned after the ear canal ablation as with ventral bulla osteotomy. Only a well-designed prospective study can accurately compare these two approaches for bulla osteotomy combined with ear canal ablation as a treatment for intractable otitis. References I . Seward CO, Blackmore WM. Ott RL. Treatment ofchronic canine otitis externa by ablation of the ear canal. J Am Vet Med Assoc 1958: 133:417-419. 2. Smeak DD, DeHoff WD. Total ear canal ablation: clinical results in thedogand cat. Vet Surg 1986; 15:161-170. 3. Tufvesson E. Operation for otitis externa in dogs according to Zepps method. Am J Vet Res 1955; 16:565-570. 4. Grono LR. Surgical treatment of canine otitis externa. Aust Vet J 1962;38:235-238. 5. Sprcull JSA. Treatment of otitis media in the dog. J Small Anim Pract 1964;5:107-152. 6. Harvey CE. Diseases of the middle ear. In: Slatter D. ed. Tesrbook Q/ Stnull Animal Srirgrrj.. Vol. 11. Philadelphia: WB Saunders, 1985:1915-1923. 7. Barrett RE, Rathfon BL. Lateral approach to bulla osteotomy. J Am Anim Hosp Assoc 1975: I1:203-205. 8. McNutt GW. McCoy JH. Bulla osteotomy in the dog. J Am Vet Med Assoc 1930:77:617-628. 9. Cechner P. Total ablation ofthe ear canal and middle ear drainage. Abstract Ann Mtg Am Coll Vet Surg 1982. 10. Schwartz A. Ablation ofthe external ear canal. In: Bojrab MJ, ed. Cirrrcnr Techniyitrs rn Stnall Anr~nalSitrgerv. Philadelphia: Lea & Febiger, 1983:102- 104. I I. Mason LK, Harvey CE. Orsher RJ. Total ear canal ablation combined with lateral bulla osteotomy for end stage otitis in dogs: results in thirty dogs. Vet Surg 1988; 17:263-268. 12. Lane JG. Otitis media and otitis interna. In: Lane JG, ed. ENT & Oral Sirrgerj, of'[hcDog and Cul. Bristol: Wright PSG, 1982: 257-271. 13. Redding RW, Myers LJ. Evoked response. In: Oliver JE, Hoerlein BF. Mayhew IG. eds. L'efPrinury Neirrologj:. Philadelphia: WB Saunders, 1987:171-173. 14. Berzon JL, Bunch SE. Recurrent otitis externa and media secondary to fibroma of the middle ear. J Am Anim Hosp Assoc 1980: 16173-77. 15. Meyerhoff WL, Kim CS. Paparella MM. Pathology of chronic otitis media. Ann Otol Rhino1 Laryngol 1978;87:749-761.
Chronic Otitis Externa and Otitis Media Treated by Total Ear Canal Ablation and Ventral Bulla Osteotomy in Thirteen Dogs N.J. H. SHARP, BVetMed, MVM, MRCVS, DiplornateACVS Ventral bulla osteotomy was combined with total ear canal ablation for the treatment of chronic otitis externa and otitis media in 13 dogs (14 ears) that had been refractory to medical and surgical treatments. Resolutionof disease occurred in 11 dogs (12 ears). One dog with unilateral disease underwent a second operation before achieving a good result. One dog was euthanatized for persistent unilateral disease after three surgical procedures. The recurrence of disease in these two dogs (15%) was associated with remnants of ear canal integument within the osseous horizontal canal or tympanic bulla. Facial paralysis occurred in four dogs (31°/,) and there were no complications in eight dogs (62%). This technique shows no advantage over lateral bulla osteotomy combined with total ear canal ablation for the treatment of chronic otitis externa and otitis media.
was first described as a A treatment for canine otitis externa in 1958.’ When the condition is complicated by otitis media, ablation BLATION OF THE E A R CANAL
alone may be inadequate because it does not drain the middle ear and fistulation may r e ~ u l t . Otitis ~ - ~ media has been reported to complicate up to 52% of chronic otitis externa cases.’ When both otitis externa and otitis media are present, middle ear drainage should accompany ablation.‘ Of the techniques described for surgical drainage of otitis media, the most useful are lateral and ventral bulla osteotomies.6-8 Both have been combined with ablation of the ear canal as treatment for concomitant intractable otitis externa and Long-term results have been reported for ablation alone and combined with lateral bulla o ~ t e o t o m y . ~ .In ~ , this ’ study, those results are compared with long-term results of ear canal ablation combined with ventral bulla osteotomy in dogs with otitis externa and otitis media.
’
Materials and Methods Thirteen dogs with severe intractable otitis externa without neoplasia were studied. All had been treated medically, surgically, or both, for 1 to 4 years without success. Additional lesions in six of the dogs included fa-
cial abscesses, facial sinus tracts, no patent opening to the auditory meatus on the affected side, facial paralysis, and otitis interna on the affected side (Table 1). Examinations were conducted with the dogs under general anesthesia. Dorsoventral skull and “open mouth” rostrocaudal radiographic projections were used to evaluate the horizontal ear canals, petrous temporal bones, and tympanic bullae. Radiographic findings of bulla osteitis were interpreted as otitis media. Samples for bacteriologic examination were aspirated from the tympanic bulla with a 6 inch blunt metal (Spreull) needle.5 When this was not possible, a fine-needle aspirate was obtained from the facial abscess (dogs 5 and 12), or the facial sinus was cultured (dogs 2, 8, and 9). Culture of the tympanic cavity was subsequently performed at surgery in these five dogs. The diagnosis of otitis media was based on absence of an intact tympanic membrane as shown by otoscopic examination, and by the uninterrupted passage of a 6 inch blunt metal needle to the medial wall of the bulla.’’ To substantiate active inflammatory disease, additional criteria of otitis media were based on radiologic, histopathologic, or bacteriologic examination of the middle ear (Table 2). Unilateral surgery was performed in 12 dogs. Dog 11 underwent bilateral surgery with a 4 month interval between procedures. A neurologic examination was per-
From the Veterinary Hospital, University of Liverpool, Liverpool, England. The author thanks Drs. C. E. Harvey and P. G. Bedford for their advice and helpful criticism in the preparation of this manuscript. Reprint requests: N.J.H. Sharp, MRCVS, North Carolina State University, College of Veterinary Medicine, Department of Companion Animal and Special Species Medicine, 4700 HillsboroughSt, Raleigh, NC 27606.
162
163
SHARP TABLE 1. Signalrnent and Presenting Features in Thirteen Dogs with Otitis Externa and Otitis Media
Dog No. 1 2 3 4 5 6
Age (yrs)
9 10 2
2 10 4
Breed
Duration of Signs (YW
Affected Ear
German shepherd W ~ terrier W WHW terrier German shepherd English setter German shepherd
1.5 3 1.25 1.5 1 3
Right Left Left Left Right Left
Previous Treatment
VCA Bulls lavage and LWR
Bulls lavage, ventral osteotomy and LWR Bulls lavage and VCA LWR
4 3.5
German shepherd Standard poodle
4 1.25
Left Left
9
9
Crossbred
1
Right
10 11
7 5.5
German shepherd Basset hound
2.5 2
12
4
Labrador retriever
3
Left Left Right Left
Attempted total canal ablation without bulla osteotorny Bulls lavage and LWR Bilateral bulla lavage and LWR LWR
13
4
German shepherd
2
Left
LWR and bulla lavage
WHW-West
highland white; VCA-vertical
-
Bulls lavage and LWR
a
7
Additional Lesions
Facial sinus No opening to horizontal canal
Facial abscess for 1 month
Facial sinus; no opening to horizontal canal Facial sinus; no opening to horizontal canal
Abscess for 1 yr, facial paralysis and otitis interna for 1 month duration; no opening to horizontal canal
-
canal ablation; LWR-lateral wall resection
formed on days I and 7. Owners were asked about the dog's condition at least 1 year after the last surgical procedure.
Si1 rgicul T d i niqiic. Systemic antibiotics selected from bacteriologic sensitivity results were administered parenterally I hour before surgery. External ear canal ablation was performed first."' Total ear canal ablation was performed in dogs 2 and 5. In the I 1 dogs with previous ear canal surgery, any remaining horizontal canal was excised. Only the annular cartilage could be identified in dog 9 because of a previous attempt at canal ablation. During surgery, the parotid salivary gland and facial nerve were identified and protected by gentle ventral retraction. Sinus tracts were debrided with care to protect the facial nerve. Before wound closure, the epithelial lining ofthe bony canal was thoroughly curetted. Each dog was repositioned in dorsal recumbency and the neck was prepared aseptically for surgery. The tympanic bulla was exposed by a ventral approach.x A large opening was made into the tympanic cavity with an osteotome. Any tissue or debris within the cavity was removed for bacteriologic or histopathologic examination, or both. Curettage was performed carefully to avoid the dorsal and medial aspects of the tympanic cavity, to pre-
vent vestibular damage. The surgical site was flushed with physiologic saline solution and the wound was closed with chromic gut in the deep layers and monofilament nylon in the skin. In the five dogs with soft tissue swelling or sinus formation, a Penrose drain was placed in the tympanic cavity and exteriorized adjacent to the ventral incision. Antibiotics were administered orally for 2 weeks. In dogs with Pseirdomonas infection, gentamicin was administered intravenously for 6 days and amoxicillin orally for 2 weeks. Results The tympanic membrane was absent and there was at least one other feature diagnostic of otitis media in all 14 ears (Table 2). Otoscopy was not possible in dogs 3 , 5, 8, 9, and 12 because of occlusion of the horizontal or the vertical canal. Otitis media was confirmed radiographically in 1 1 dogs by lysis or sclerosis of the tympanic bullae or petrous temporal bones. or by increased radiopacity within the tympanic cavity. In one dog the bulla was filled with radiopaque material of bone density after a previous bulla osteotomy. Other radiographic features included calcification of the ear canal cartilages (4 dogs) and occlusion of the canal lumen (5 dogs). In three dogs, including one ear in dog 1 I , there were no radiographic signs of otitis media.
164
EAR CANAL ABLATION AND VENTRAL BULLA OSTEOTOMY TABLE 2. Results of Evaluationand Surgery (Continues)
Dog No.
Otoscopic/Surgical Findings
Radiologic Findings
Bacteriologic Findings
Histopathologic Findings
FOIIOW-UP
1
Stenosis and ulceration of horizontal canal
Sclerosis of PTB; tympanic bulla radiopacity
Pseudomonas sp Staphylococcus aureus
Fibrous connective tissue with a ciliated epithelial lining
1 yr, no recurrence
2
Hyperkeratosis and ulceration of vertical canal; sinus draining from horizontal canal
Bulla radiopacity
S. aureus
Chronically inflamed granulation tissue
Euthanasia at 3 mos due to CRF; temporary VII paralysis for 1 wk
3
Occluded horizontal canal
Bulla lysis; occluded horizontal canal
Sterile
Chronically inflamed granulation tissue
1 yr, no recurrence
4
Stenosis and ulceration of horizontal canal
Bulla lysis and radiopacity
Pseudomonas sp and Escherichia coli
Chronically inflamed granulation tissue
4 yrs, no recurrence
5
Facial abscess occluding and communicating with horizontal canal
Sclerosis of PTB, calcified and occluded horizontal canal
Proteus sp and E. coli
No tissue present in bulla
2 yrs, no recurrence VII paralysis permanent
6
Ulceration of horizontal canal; poor LWR
Radiodense tympanic bulla; calcified horizontal canal
Pseudomonas sp and E coli
Not done
3.5 yrs, no recurrence
7
Hyperkeratosis of horizontal canal
Normal
E. coli
No tissue present in bulla
3 yrs, no recurrence
8
Sinus draining from horizontal canal
Bulla lysis and radiopacity; occluded horizontal canal
S. aureus
No tissue present in bulla
3 yrs, no recurrence VII and XI1 paralyses permanent
9
Sinus draining from horizontal canal
Bulla lysis, sclerosis of PTB; occluded horizontal canal Normal
Proteus sp, Staphylococcus epidermis
Chronically inflamed granulation tissue
3 yrs, no recurrence
Pseudomonas sp
No tissue present in bulla
4 yrs, no recurrence
10
Stenosis of horizontal canal; poor LWR
11L
Intense erythema of horizontal canal
Sclerosis of left PTB, bulla radiopacity
S. aureus, Proteus sp
No tissue present in bulla
5 yrs, no recurrence
11R
Intense erythema of horizontal canal
Right normal
As above plus Bacteriodes SP
No tissue present in bulla
5 yrs, no recurrence
Pscvidomonas spp were zultured from four dogs. Tympanic bulla tissue from seven dogs was interpreted histologically as chronically inflamed granulation tissue. In dog 1 , this tissue was lined by ciliated epithelium. In five dogs. no tissue was found within the bulla. The bulla
from dog 6 was tilled with a homogeneous material grossly resembling bone. In five dogs, there was communication between the horizontal canal and either a facial abscess (dogs 5 and 12) or a sinus tract (dogs 2, 8, and 9). In four dogs. com-
165
SHARP TABLE 2. (Continued)
Dog No. 12
Facial abscess occluding and communicating with horizontal canal
Bacteriologic Findings
HistopathologicFindings
FoIIOW-UP
Bulla radiopacity; calcified and occluded horizontal canal Not done
S. aureus Pasturella sp
Chronically inflamed granulation tissue
Resolution of all signs, then recurrence of abscess after 3 wks
As above
As above with acute inflammatory tissue
Recurrenceof signs after 2 wks
Recurrenceof abscess 2 wks after surgery
As above with lysis of bulla
As above
Acutely inflamed granulation tissue
Recurrence of signs after 4 wks
Recurrence of abscess 4 wks after surgery
Not done
Not done
Stratified squamous epithelium with cystic glandular elements
Euthanasia
Stenosis and ulceration of horizontal canal
Sclerosis of PTB, bulla lysis, calcified horizontal canal
S. aureus
Chronically inflamed granulation tissue
VII paralysis permanent
Facial sinus 4 wks after surgery
As above
As above
As above plus areas containing cystic glandular elements
1 year, no recurrence
Recurrenceof abscess 3 wks after surgery
13
Radiologic Findings
Otoscopic/Surgical Findings
PTB-petrous
temporal bone; CRF-chronic
renal failure; VII-facial
munication occurred between the annular and auricular cartilages; in dog 5, the exact site was not determined. The abscesses and fistulae were immediately ventral to the horizontal canal. The median follow-up period was 3 years. There was no recurrence of infection or sinus formation and the owners were satisfied with the results in dogs 1 to 1 I . Dog 2 had no recurrence ofear disease 3 months after surgery, but was euthanatized because of chronic renal failure. Surgical complications included facial nerve paralysis in dogs 2, 5, and 13, and combined facial and hypoglossal paralysis in dog 8. The paralyses remained permanent in dogs 5 , 8 , and 13 but caused no additional complications during the follow-up period. In dog 12, presenting signs of facial paralysis and otitis interna abated after the first surgery. All dogs were subjectively deaf in the affected ear. Dog 1 1 , which had bilateral surgery, responded to low-frequency noises. Clinical signs recurred and a draining facial sinus developed 4 weeks after surgery in dog 13. The middle ear was reexplored via a lateral approach and several remnants of integument were found attached to the osseous horizontal canal. The remnants were removed, the site was irrigated as before, and a Penrose drain was placed before closure. There has been no recurrence for 1 year since the second operation.
nerve; LWR-lateral
wall resection; XII-hypoglossal
nerve.
Abscess formation recurred 3 weeks after surgery in dog 12. A second ventral bulla osteotomy incision was made and additional granulation tissue was removed from the bulla. Signs recurred 2 weeks later and the area was reexplored via a lateral approach. Granulation tissue was curetted from the bulla but no canal integument could be identified. Clinical signs recurred 4 weeks later and the dog was euthanatized. At postmortem examination, there was severe osteomyelitis ofthe petrous temporal bone. Deeply embedded within the bone were remnants of ear canal integument, consisting of stratified squamous epithelium and cystic glandular structures surrounded by acutely inflamed granulation tissue. Discussion All dogs in this series had severe otitis externa and at least two features consistent with a diagnosis of otitis media. Conservative therapy, including lateral ear resection in most ofthe dogs, had been unsuccessful. In such cases, a combination of ear canal ablation and bulla osteotomy is the recommended treatment.' The most common postoperative complications in this series were deafness, facial nerve paralysis, and recurrence of ear disease. Hypoglossal nerve paralysis occurred in one dog, which has been reported elsewhere
EAR CANAL ABLATION AND VENTRAL BULLA OSTEOTOMY
after ventral bulla osteotom y.* The deafness, also noted elsewhere,* was subjective and would require clarification by electrodiagnostic techniques. The persistence of hearing ability in a dog after bilateral surgery has been reported previously.* Facial paralysis occurred in 3 1% of the dogs in this series and was permanent in 23%. Corresponding rates of permanent facial paralysis after lateral bulla osteotomy combined with ear canal ablation were 33%,' 1770,'' and 8%.' The facial paralysis seen in the current series occurred in three of five dogs in which the nerve was entrapped in fibrous tissue that resulted from extension of infection outside the ear canal. Postoperative facial paralysis was documented previously in two dogs with facial sinuses arising from the horizontal canal.'.I4 Attempts to isolate the facial nerve surgically in this situation should be minimized. Postoperative facial paralysis described in a previous report required enucleation in one dog and continuous artificial tears in another.2 The three permanent facial nerve deficits in this series caused the dogs no problems during observation periods of 1 to 3 years. In another study, five dogs with postoperative facial paralysis also had no associated adverse effects. ' ' The presence of Pseztdumunus spp in the middle ear was not associated with a poor outcome. The two dogs that required reoperation had epithelial and glandular tissue from the external ear canal within the bulla. The integument found deeply embedded within the petrous temporal bone in dog 12 was presumably pushed there during the initial curettage of the bony horizontal canal. Tissues removed from the tympanic bullae were identified histologically as granulation tissue. In samples from humans with otitis media, mature fibrous tissue or immature granulation tissue also is the most frequent finding. I In a previous report, total ear canal ablation alone was complicated by recurrence or prolonged drainage in 23% and wound infection in 2790 of 30 cases.2 In the same report. one ( 17%) of six dogs that underwent lateral bulla osteotomy combined with ear canal ablation had recurrence of infection.' In two other reports of lateral bulla osteotomy combined with ear canal ablation the recurrence rates were 3 (12%)" of 26 dogs and I ( 8 % ~of) ~13 dogs. The overall rates of recurrence or persistence of drainage after the lateral approach appear to be lower than the 15% found in the current series using the ventral
approach.2.'.' ' Valid comparison is difficult, partly because the clinical features and criteria for case selection or follow-up are not available for one of these reports.' The apparent advantage of the lateral technique may be because removing the ventral aspect of the osseous horizontal canal allows more accurate curettage of the ear canal integument. Another advantage of lateral bulla osteotomy is that the patient does not need to be repositioned after the ear canal ablation as with ventral bulla osteotomy. Only a well-designed prospective study can accurately compare these two approaches for bulla osteotomy combined with ear canal ablation as a treatment for intractable otitis. References I . Seward CO, Blackmore WM. Ott RL. Treatment ofchronic canine otitis externa by ablation of the ear canal. J Am Vet Med Assoc 1958: 133:417-419. 2. Smeak DD, DeHoff WD. Total ear canal ablation: clinical results in thedogand cat. Vet Surg 1986; 15:161-170. 3. Tufvesson E. Operation for otitis externa in dogs according to Zepps method. Am J Vet Res 1955; 16:565-570. 4. Grono LR. Surgical treatment of canine otitis externa. Aust Vet J 1962;38:235-238. 5. Sprcull JSA. Treatment of otitis media in the dog. J Small Anim Pract 1964;5:107-152. 6. Harvey CE. Diseases of the middle ear. In: Slatter D. ed. Tesrbook Q/ Stnull Animal Srirgrrj.. Vol. 11. Philadelphia: WB Saunders, 1985:1915-1923. 7. Barrett RE, Rathfon BL. Lateral approach to bulla osteotomy. J Am Anim Hosp Assoc 1975: I1:203-205. 8. McNutt GW. McCoy JH. Bulla osteotomy in the dog. J Am Vet Med Assoc 1930:77:617-628. 9. Cechner P. Total ablation ofthe ear canal and middle ear drainage. Abstract Ann Mtg Am Coll Vet Surg 1982. 10. Schwartz A. Ablation ofthe external ear canal. In: Bojrab MJ, ed. Cirrrcnr Techniyitrs rn Stnall Anr~nalSitrgerv. Philadelphia: Lea & Febiger, 1983:102- 104. I I. Mason LK, Harvey CE. Orsher RJ. Total ear canal ablation combined with lateral bulla osteotomy for end stage otitis in dogs: results in thirty dogs. Vet Surg 1988; 17:263-268. 12. Lane JG. Otitis media and otitis interna. In: Lane JG, ed. ENT & Oral Sirrgerj, of'[hcDog and Cul. Bristol: Wright PSG, 1982: 257-271. 13. Redding RW, Myers LJ. Evoked response. In: Oliver JE, Hoerlein BF. Mayhew IG. eds. L'efPrinury Neirrologj:. Philadelphia: WB Saunders, 1987:171-173. 14. Berzon JL, Bunch SE. Recurrent otitis externa and media secondary to fibroma of the middle ear. J Am Anim Hosp Assoc 1980: 16173-77. 15. Meyerhoff WL, Kim CS. Paparella MM. Pathology of chronic otitis media. Ann Otol Rhino1 Laryngol 1978;87:749-761.
