1013

What's New in Head and Neck of the Dog M. J.

Bojrab, DVM, MS, PhD, Larry

A.

Nafe, DVM

Some of our readers may wonder at the subject of this article, and think that it somehow crept into the wrong journal. However, every now and then it seems good policy to lift one's eyes from the work at hand to appreciate the breadth of influence of the modern suppor¬ tive techniques that we have become familiar with. Increased future communication between the disciplines of veterinary and human surgery can lead to nothing but benefit to both parties.Richard Warren, MD

\s=b\ Major surgical procedures in veterinary medicine have increased in sophistication and number. An area that has received much attention recently is surgery of the head and neck of the dog. This article discusses some new techniques that have gained popular usage in recent years. Repair of tracheal collapse, treatment of salivary mucoceles, pharyngostomy, and atlantoaxial subluxation are the procedures reviewed.

(Arch Surg 112:1013-1018, 1977)

progressed tremendously in the increasing number of veterinarians advanced training in veterinary surgery. The are recent trend toward specialization is reflected in the growth of membership in the American College of Veteri¬ nary Surgeons. This specialty group, founded in 1965 by a few charter members, presently has over 100 members. Paralleling this increased interest in surgery as a specialty is an increase in the veterinary literature of new surgical techniques, as well as modifications of existing surgical techniques. This article discusses a few techniques that have recently gained widespread utilization in appropriate

Veterinary past seeking

surgery has

ten years. An

canine

cases.

Accepted

publication Dec 23, 1976. Department of Veterinary Medicine and Surgery, College of Veterinary Medicine, University of Missouri, Columbia (Dr Bojrab), and the Animal Medical Center, New York (Dr Nafe). Reprint requests to Veterinary Teaching Hospital; Department of Medicine and Surgery; College of Veterinary Medicine; University of Missouri, Columbia, MO 65201 (Dr Bojrab). From the

for

Surgery

TRACHEAL COLLAPSE Incidence A number of cases of trachéal collapse in the dog have been recorded. Baumann (1941)' was the first to describe the condition. No further reports were published until 1960, when Leonard- mentioned a case. Since that time, over 40 cases of trachéal collapse have been reported.:1 The cause of collapsed trachea is unknown. Although obesity and head conformation have been mentioned as predisposing causes, it is usually described as an acquired lesion found in middle-aged dogs of miniature and toy breeds.1 In these cases, there is no loss of potential trachéal ring size, although the rings do lose their ability to remain firm, and, subsequently, collapse. To date, there is no published information to our knowledge on the chemical contents of trachea! rings in dogs with normal vs collapsed tracheas. This condition has also been described in young dogs as a congenital lesion. Clinically, both the acquired and congenital conditions have the same presenting signs.5 The condition causes respiratory embarrassment due to dorsoventral narrowing of the trachéal lumen. Its major pathological feature is a weakened, flaccid trachealis muscle and annular trachéal ligaments that connect the cartilaginous rings dorsally in a bowstring effect. This weakening and stretching of the soft tissues allow the rings to flatten and the trachea to assume a lunate rather than circular shape (Fig 1). The major clinical sign associated with trachéal collapse is a continual honking cough. In severe trachéal collapse, the animal may have persistent respiratory infections. The diagnosis is confirmed by palpation of the cervical trachea, tracheoscopy (endoscopie), and cervical as well as thoracic roentgenograms." These roentgenograms must be taken on both inspiration and expiration in order to illustrate the trachéal collapse." Indications

Surgical correction is currently

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being performed on only

soft tissue of the trachea with polyester suture material (Fig 3 and 4).s" An antibiotic treatment regimen that was chosen by presurgical sensitivity testing should be started 24 hours before surgery and continued for five days

postoperatively. If the cough persists postoperatively, an antitussive agent should be used to prevent damage to the suture line. Exercise and excitement should be minimized until healing has taken place (14 to 21 days). In the event the cartilagenous rings also become flaccid, the previously described technique will not be successful. In this case, 0.5 cm wide, C-shaped polyurethane prosthetic rings are implanted and sutured on the outside of the trachea. They are placed approximately 1 cm apart for the entire distance of the collapse.12 SALIVARY MUCOCELE Incidence

Clinically, the most common injury to the salivary gland dog is salivary mucocele.1' The sublingual gland is most frequently involved. This condition develops from a leakage of saliva into surrounding tissue due to damage to the salivary gland or duct. The most frequent sites for collection of the extravasated saliva are the sublingual in the

Fig 1.—Top trachea demonstrates lunate appearance of collapsed trachea in cross section. Lower cross section represents normal trachea. Units shown are metric (from Rubin et al6). those animals that do not respond to conservative treat¬ ment. It is important that the cases selected for surgery be carefully evaluated. Many dogs exhibiting signs of trachéal narrowing have other underlying pulmonary or cardiac problems that either interfere with correction or must be stabilized before correction is undertaken. It is believed that unrelieved trachéal narrowing can cause hypoxia, and the hypoxia may result in cardiac, pulmonary, or CNS disturbances. There have been at least five methods for trachéal repair reported in the literature.61" One more recent technique that we have used successfully in a number of cases where the cartilagenous rings have maintained their structural integrity is the method of plicating the dorsal trachéal ligament. This procedure shortens the gap between the free ends of the trachéal cartilage and corrects the dorsoventral collapsing of the trachea. The trachea is approached from a ventral midline incision in the cervical region extending from the larynx to the thoracic inlet. The paired sternohyoideus muscles are separated the length of the incision to expose the trachea. The trachea is freed from the surrounding connective tissue by blunt dissection and is rotated so that the dorsal surface is accessible (Fig 2). Starting from the cranial trachéal region, horizontal mattress sutures are placed 0.5 cm apart through the dorsal

tissue on the floor of the mouth on one side of the tongue, and the superficial connective tissues of the intermandib¬ ular or cranial cervical area. The cause of the gland or duct damage is rarely known. Foreign body or trauma or both have been suggested as possible causes. The incidence of this condition is relatively low: in one study of approxi¬

mately 4,000 dogs presented to a university veterinary hospital, only one case of this condition was diagnosed.14 However, the condition is important because of its intract¬ able nature.

Indications

Treatment directed at the mucocele, such as its surgical resection, chemical cautery of its lining, or aspiration of the fluid, will frequently result in recurrence of the lesion. Because a ránula will often become traumatized by teeth, and because a pharyngeal mucocele can result in respira¬ tory obstruction, these lesions should always be treated definitively. Since the lining of the mucocele is not secre¬ tory, and thus the saliva is coming from a ruptured sublingual or mandibular duct, the definitive surgical treatment is directed at the removal of the involved salivary glands and draining or aspirating the muco¬ cele.1417 These two glands are intimately associated, and thus are removed as a unit. A 4- to 6-cm incision is made over the easily palpated mandibular salivary gland, caudal to the angle of the mandible (Fig 5). The thin cutaneous platysma muscle is incised to reveal the capsule of the mandibular salivary gland, which is also penetrated. An Allis tissue forceps is used to retract the salivary gland through the incision. Blunt and sharp dissection of the sublingual gland is continued rostrally between the masseter and digastric muscles (Fig 6).15'718 A hemostat is placed across the most rostral portion of the sublingual duct that can be exposed

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Fig 4.—Repaired trachea showing mat¬ placement (from Rubin et al6). tress suture

*J- uu-

Fig 2.—Plication of dorsal soft tissue struc¬ ture with Allis tissue forceps to determine amount of eversión required (from Rubin et al6).

Fig 3.—Representation of mattress suture placement in trachea (from Rubin et al6).

5.—Lateral view of head of dog. Skin incision (arrow) for salivary gland resec¬ tion is shown in relation to mandibular

Fig 6.—Mandibular salivary gland is grasped with Allis tissue forceps and sublingual salivary gland is dissected with Metzenbaum scissor (from Harvey16).

Fig

salivary gland (from Harvey16).

(Fig 7). Care is taken to make sure that the rostral polystomatic sublingual glands are retracted and removed. The duct is then ligated rostral to the hemostat with 2-0 chromic gut, and the duct is then replaced in the incision. The subcutaneous tissue and skin

are

closed in the normal

manner.1"

The mucocele itself is aspirated or drained by a ventral incision to remove the accummulated saliva. Postoperative care consists of supportive treatment. PHARYNGOSTOMY TUBE

Anorexia is a serious complication of many diseases of dogs and cats seen by the veterinary practitioner. Labora¬ tory dogs and cats often become stressed from shipping, and upper respiratory infections develop and they stop eating. The success of the treatment regimen often is dependent on fulfilling the nutritional needs of the animal until the specific therapy becomes effective.-" In these animals, a pharyngostomy tube is indicated, through which the caloric requirements can easily be administered. Other indications for a pharyngostomy tube are postop¬ eratively, after oral or esophageal surgery, and to remove fluid accumulation from the stomach, such as in the gas gastric dilation and torsion syndrome. The technique is or

Fig 7.—Hemostat is placed across sublin¬ gual gland as far rostrally as possible prior to ligation (from Harvey16).

rapid, and consists of making an incision caudal to the angle of the mandible into the pharyngeal recess (Fig 8). A flexible plastic tube is then grasped with forceps and drawn into the pharynx through the incision. The previously measured tube is passed down to the stomach and the external end is sutured to the skin of the pharyn¬ gostomy incision (Fig 9).s·21-' The tube must project only a few centimeters exterior to the incision. Capping of the tube when not in use is necessary to avoid loss of gastric contents and inflow of air. The skin edges of the incision will begin to granulate, but will not close due to the presence of the tube. However, once the tube is removed, healing is rapid, and rarely does the incision require surgical closure. BULLA OSTEOTOMY Incidence

Ear infection is widespread in the canine population throughout the world. It has been reported at one univer¬ sity veterinary teaching hospital that one out of eight animals brought to the hospital are clinically affected with

otitis.-4 Otitis media in the dog is commonly caused by an extension of otitis externa. Often, standard medical treat-

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Stylohyoid Epiglottis s Thyrohyoid Thyroid cartilage *ç~ Cricoid cartilage Trachea

Fig 8.—Proper placement (from Bohning8).

of

finger

lateral to

hyoid apparatus Fig 9.—Tube Bohning").

(systemic antibiotics, myringotomy, and flushing) of the otitis media is not satisfactory. At this point, surgical intervention is indicated in order to gain access and drainage to the area.-4-7 Although there are three techniques of bulla osteotomy in common use in veterinary medicine, the ventral approach is becoming the most popular.-4·-7 In this procedure (the ventral diverticulum of the middle ear cavity just rostral to the mastoid), the bulla is reached between th digastric and the styloglossus muscle (Fig 10, top) through a skin incision lateral to the larynx. Care should be taken to isolate and retract the hypoglossal nerve medially. When the bulla has been exposed, it is opened with a bone chisel (Fig 10, bottom) or trephine, and at this point a culture of the contents can be obtained. Further treatment depends on the type of lesion revealed and the results of the culture. Often, a drainage tube is placed from the opened bulla to the outside. The surgical site is then closed in the routine manner.-5 Daily flushing down the external ear through the myringotomy and out the bulla drain is continued until improvement is noted

in

ment

(five

to

seven

position within pharynx and esophagus (from Oseeus Bullo

Hypoqloasai V- Sublingual CjlancL

days).

ATLANTOAXIAL SUBLUXATION In recent years, atlantoaxial subluxation has been recog¬ nized with increasing frequency in the dog.-s Atlan¬ toaxial subluxation may result in dorsal displacement of the axis, with severe spinal cord compression.-" The most common cause of atlantoaxial subluxation and subsequent spinal cord compression is the congenital absence of the odontoid process or dens (Fig ll).38 The other two predis¬ posing factors are the rupture of the ligaments that hold the odontoid process in place (Fig 12) and a fracture of the dens (Fig 13).-* Surgical correction must be immediate because of the vital areas of the spinal cord involved. The joint is approached from the dorsal midline through the intervening epaxial muscles. The actual technique varies between surgeons, but the goal is to stabilize the joint dorsally with heavy, malleable stainless steel wire (20- to ;"

%*>

exposure of ventral aspect of osseous bulla. Bottom, Bulla has been opened with bone chisel to expose middle ear cavity (from Spreull27).

Fig 10.—Top, Surgical

22-gauge orthopedic) (Fig 14 through 17). Also, some experts believe that decompression of the cord is indicated, and they achieve this by removal of bone from the caudal

arch of the atlas and from the cranial wall of the axis.28 The wire must be very tight to prevent any movement that might eventually shear the wire. The incision is closed in a suitable manner. These animals require careful postoperative observation, and should be confined to an intensive care unit after the

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fa w

Fig 11.—Congenital absence of odontoid (dens) with lack of joint support and subluxations. Arrows indicate abnormal rotational relationship between atlas and axis (from Gage28).

Fig 12.—Rupture of ligaments with sublux¬ ation of atlantoaxial joint. Arrows indicate abnormal rotational relationship between atlas and axis (from Gage28).

Fig 14.—Threading of double strand of wire under dorsal arch of atlas and dorsal to spinal cord to emerge at foramen magnum. Note that a hemilaminectomy has been performed (from

Gage28).

Fig 13.—Fractured odontoid process with subluxation of atlantoaxial joint. Arrows indicate abnormal rotational relationship between atlas and axis (from Gage28).

Fig 15.—Loop of wire has been pulled cranially to sufficient length caudally to axis (from Gage28).

to reach

Fig 16.—Two drill holes being placed in dorsal spine of axis (from

Gage28).

Fig 17.—Completed operation showing double wire technique for reduction and stabilization (from Gage28).

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operation. Postoperative therapy utilizes glucocorticoids to decrease spinal cord edema and inflammation that could cause severe respiratory depression. Many surgeons combine diuretic therapy with the cortico steroids to control the edema. Physical therapy should begin on the third postoperative day and continue until the animal is ambulatory. The duration of recovery depends on the severity of the condition and the degree of irreversible cord damage present, as well as the delay prior to surgical intervention.

COMMENT

The above

techniques represent a few of the many that use recently in canine surgery. Other

have gained popular

techniques

now

utilized with

frequency

in head and neck

ventral

decompression of the cervical spinal cord, cricopharyngeal myotomy, corrective otoplasty, surgical correction of primary and secondary cleft palate, and cervical vertebral fusion utilizing a rib graft. The other regions of the body have also paralleled these surgery

are

advances with new methods. Cryosurgery, among other modes of surgery, has surfaced, and is now popular use for specific conditions, especially superficial neoplasms. The instrumentation utilized by veterinary surgeons is more sophisticated, and therefore the results are more satisfac¬ tory. Other interesting procedures just being introduced are the adaptation of human knee prosthesis to the canine stifle, a new hip prosthesis, and radical trachéal resection and anastomosis. Through continuing research, clinical trials, and comparative studies, veterinary surgery will continue to progress.

References 1. Baumann R: Dorso-ventral flattening of the trachea. Berl M\l=u"\nch tier\l=a"\rztlWschr, 1941, pp 445-447. 2. Leonard HCL: Collapse of the larynx and adjacent structures in the dog. J Am Vet Med Assoc 137:360-363, 1960. 3. Done SH, Clayton-Jones DG, Price EK: Tracheal collapse in the dog: A review of the literature and report of two new cases. J Small Anim Pract 11:743, 1970. 4. Pennock PW, Archibald J: Canine Medicine. Santa Barbara, Calif, American Veterinary Publications Inc, 1967, p 575. 5. Suter PF, Colgrave DJ, Ewing GO: Congenital hypoplasia of the canine trachea. J Am Anim Hosp Assoc 8:120-127, 1972. 6. Rubin GJ, Neal TM, Bojrab MJ: Surgical reconstruction for collapsed tracheal rings. J Small Anim Pract 14:607-617, 1973. 7. Beall AC, Harrington OB, Greenberg SD, et al: Tracheal replacement with Marlex mesh. Arch Surg 84:390-396, 1962. 8. Bohning RJ Jr: Pharyngostomy for oral maintenance, in Bojrab MJ (ed): Current Techniques in Small Animal Surgery. Philadelphia, Lea & Febiger, 1975, pp 101-103. 9. Leonard HC: Surgical correction of collapsed trachea in dogs. J Am Vet Med Assoc 158:390-396, 1971. 10. Schiller AG, Helper LC, Small E: Treatment of tracheal collapse in the dog. J Am Vet Med Assoc 147:669-671, 1964. 11. Bojrab MJ: Collapsed tracheal rings, in Bojrab MJ (ed): Current Techniques in Small Animal Surgery. Philadelphia, Lea & Febiger, 1975, pp 189-191. 12. Anderson DR: Surgical correction of tracheal collapse using Teflon rings. Ikla Vet 23:6-7, 1971. 13. Harvey CE: Canine salivary mucocele. J Am Anim Hosp Assoc 5:155-156, 1969. 14. Spreull JSA, Head KW: Cervical salivary cysts in the dog. J Small Anim Pract 8:17-35, 1967. 15. Glen JB: Canine salivary mucoceles. J Small Anim Pract 13:515-526, 1969. 16. Harvey CE: Treatment of salivary mucoceles, in Bojrab MJ (ed): Current Techniques in Small Animal Surgery. Philadelphia, Lea & Febiger, 1975, pp 97-100.

heavy

17. Hoffer RE: Surgical treatment of salivary mucocele, in Greiner TP, Greene RW, DeHoff WD (eds): North American Veterinary Clinics. Philadelphia, WB Saunders Co, 1975, vol 5, pp 333-341. 18. Lippincott CL: Correction of extensive rannulas. Vet Med Small Anim Clin 67:869-874, 1972. 19. Hoffer RE, Jensen HE: Stereoscopic Atlas of Small Animal Surgery. St Louis, CV Mosby Co, 1973, pp 181-188. 20. Teeter SM: Artificial alimentation, in Kirk RW (ed): Current Veterinary Therapy. Philadelphia, WB Saunders Co, 1974. 21. Bohning RH Jr, DeHoff WD, McElhinney A, et al: Pharyngoscopy for maintenance of the anorectic animal. J Am Vet Med Assoc 156:611-615, 1970. 22. DeHoff WD:

Pharyngostomy, in Scientific Presentations and Seminar Synopses, 38th Annual Meeting, American Animal Hospital Association. Elkhart, Ind, American Animal Hospital Association, 1971, p 550. 23. Hofmeyer FB: Surgery of the pharynx, in Palminteri A (ed): Veterinary Clinics of North America. Philadelphia, WB Saunders Co, 1972, vol 2, pp 11-12. 24. Fraser G, Gregor WD, MacKenzie CP, et al: Canine ear disease. J Small Anim Pract 10:725-743, 1970. 25. Bojrab MJ: The ear, in Greiner TP, Green RW, DeHoff WD (eds): North American Veterinary Clinics. Philadelphia, WB Saunders, 1975, vol 5, pp 513-514. 26. Denny HR: The results of surgical treatment of otitis externa of the dog. J Small Anim Pract 14:585-600, 1973. 27. Spreull JSA: Tympanotomy, bulla osteotomy and vestibular osteotomy, in Bojrab MJ (ed): Current Techniques in Small Animal Surgery. Philadelphia, Lea & Febiger, 1975, pp 71-74. 28. Gage ED: Atlantoaxial subluxation, in Bojrab MJ (ed): Current Techniques in Small Animal Surgery. Philadelphia, Lea & Febiger, 1975, pp 376-380. 29. Gage ED, Smallwood JE: Surgical repair of atlantoaxial subluxation in a dog. Vet Med Small Anim Clin 65:583-692, 1970. 30. Geary JC, Oliver JE, Hoerlein BF: Atlantoaxial subluxation in the canine. J Small Anim Pract 8:577-582, 1967.

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