Cervical mucocele is corrected using a CO2 laser

    By Noel Berger DVM, MS, DABLS, For The Education Center
    Originally Published In Veterinary Practice News, July 2018 –
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    Dog

    Figure 1: If it is difficult to determine which side the mucocele originated from, place the dog in dorsal recumbency, and gravity will cause accumulation of the fluid on the originating side.

    Cervical mucoceles are easily identified as a soft, fluctuant, nonpainful swelling of the ventral neck. Tumors and abscesses may appear similar but generally, are either firm or painful. Fine needle aspiration generally produces copious viscous fluid that is clear, straw-colored, honey-colored, or occasionally bloody. Over time cervical mucoceles may expand and migrate to the ventral midline, making it difficult to determine whether the problem involves the left or right-sided glands. Examining a sedated pet on its back (Figure 1) often allows the mucocele to migrate to the affected side.

    This condition is almost exclusively seen in dogs and very rarely in cats. There is no age or sex predisposition, and there is an increased incidence in poodles, German shepherds, dachshunds, and Australian silky terriers. The inciting cause of a salivary mucocele is usually not definitively identified. Trauma from a choke chain, bites to the neck, chewing on foreign objects, and sudden hyperextension of the neck are suspected causes. These can cause stretching or tearing of the salivary gland or the duct that drains saliva from the gland to the mouth. Saliva accumulates under the skin and incites a marked inflammatory response. The body attempts to contain the leaking saliva by creating a layer of connective tissue around the saliva.

    Surgical removal of the mandibular and sublingual glands on the side of the mucocele is the normal surgical treatment. The glands are removed together because the duct of the mandibular gland travels through the sublingual gland and removal of one gland would unavoidably traumatize the other. The mandibular gland is closely associated with the maxillary and linguofacial veins that join to form the jugular vein. Removal of the salivary glands requires careful dissection to avoid damage to the lingual nerve and ventral branches of nerves exiting C2.

    I choose to use a CO2 laser for this procedure because it is so precise when careful dissection is required in the area of vital anatomical structures. The technique of removing the salivary glands and marsupializing the cervical mucocele has been described previously, and I adapted a CO2 laser for use as a cutting and dissecting tool for surgery in a delicate area.

    With the anesthetized patient in lateral recumbency, the mandibular gland is located at the junction of the major vessels of the neck (Figure 2), ventral to the ear and caudal to the ramus. A full thickness single pass skin incision is made using a 0.25 mm diameter spot size, 10 W SuperPulse, 50 Hz pulse rate, 20 msec pulse duration, 40 msec micropulse width. This creates a skin incision that does not bleed, is not painful, and clearly exposes the surgical site without damaging vital structures below the dermis. A similar incision is also made through platysma muscle (Figure 3).

    The mandibular gland is now easily identified, and with gentle forceps traction, the supporting connective tissue can be broken down using the CO2 laser in continuous wave (CW) mode (Figure 4). I use an adjustable focal diameter handpiece and change the power exposure to 0.8 mm diameter spot size, 4 W CW. This allows me to slowly and meticulously deliver the gland while I observe the surgical field for vital structures. The precision of the CO2 laser used in this manner is quite remarkable since the energy is almost completely absorbed within 0.3 mm tissue depth. This physical property assures me that adjacent tissues are protected from unnecessary damage.

    Once the mandibular gland and the chain of sublingual salivary glands have been removed, the surgical area is flushed and closed using standard suture technique (Figure 5). To continue the procedure, the mucocele needs to be drained and marsupialized to the oral cavity. Using the CO2 laser for this portion of the procedure provided a clean and clear surgical field. I set the laser to 0.4 mm diameter spot size, 15 W CW and made an incision over the bulging mucocele buccal to 409 (Figure 6). The mucocele contents were expressed and after several sterile saline flushes, a few sialoliths were found (Figure 7). There was no bleeding during this procedure—the use of a CO2 laser helped me visualize vital structures so the procedure could be completed rapidly.

    Marsupialization was then performed by suturing the rim of oral mucosa to the connective tissue of the mucocele (Figure 8). I used a synthetic braided absorbable 3-0 suture because it is soft and comfortable for my patient. Over the course of a few weeks, the mucocele sac will granulate in and not return on that side. The patient will still produce saliva from other glands in the mouth (parotic, pharyngeal, zygomatic salivary glands).

    Cervical mucocele is a cosmetic problem in dogs, and there is an easy surgical solution to provide a normal appearance. In just a few short weeks after the surgery, the patient will look normal again and the mouth will be healed (Figure 9). I enjoy using a CO2 laser in this procedure because it is precise, it provides pain relief, and less bleeding occurs so I can see better and finish the procedure faster.

    Noel Berger DVM, MS, DABLS, is a graduate of Cornell University (1988, 1989) for both his DVM and MS in clinical sciences. He has been a certified diplomate of the American Board of Laser Surgery in veterinary surgery since 2000, and he has written a textbook on the subject. He has lectured nationwide on laser physics and clinical applications for small animal veterinarians and is available for consultation and training at Quail Hollow Animal Hospital, Wesley Chapel, Fla.

    References

    1. Fossum TW, et al. Salivary Mucoceles, 417-422, Small Animal Surgery. 4th Edition, Elsevier, 2013.
    2. Berger NA, Eeg PH, Veterinary Laser Surgery: A Practical Guide, Blackwell Publications, 2006.
    3. Grandage J, et al. The Salivary Glands, In: Slatter DH ed. Textbook of Small Animal Surgery, WB Saunders, 1985.

    This Education Center article was underwritten by Aesculight of Bothell, Wash., the manufacturer of the only American-made CO2 laser.