By Jan Bellows, DVM, Dipl. AVDC, Dipl. ABVP For The Education Center
Originally published in Veterinary Practice News, April 2017 – Download as a PDF
In dogs and cats, the tongue has important functions involved in prehending, chewing, drinking, swallowing, grooming and vocalization. The tongue is a muscular organ composed of both striated intrinsic and extrinsic muscles. The rostral two thirds of the tongue comprise its body, and the caudal one third comprises its root, which is attached to the hyoid apparatus. The dorsal surface of the tongue is covered by thick keratinized stratified squamous epithelium, which forms papillae. The ventral tongue surface contains less cornified mucosa. The lingual frenulum connects the tongue to the floor of the mouth (the intermandibular space). The tongue is richly vascularized and innervated. The nerves are important for the lingual sensory function including tactile, taste, thermal, pain and proprioception. Due to the important role of the tongue, lingual lesions may negatively impact an animal’s overall health and well-being. Therefore, early detection and surgical correction are necessary.
The CO2 laser has become a well-accepted instrument for oral surgery used by many veterinary dentists. The 10,600-nanometer (or 10.6-micron) wavelength of the CO2 laser causes a distinct tissue effect through heating intracellular water to produce steam and disrupt cell membranes resulting in tissue separation and hemostasis. Shallow thermal necrosis zones of under 50 microns at incised tissue edges are typical for modern CO2 lasers that utilize high peak power short pulses (superpulse).
For tongue surgery, the CO2 laser can be used in the continuous wave mode and variations of the pulsed mode. The superpulse mode is desirable for excision and ablation of oral lesions, because the pulse width is shorter than the thermal relaxation time of oral soft tissue. In addition, superpulse allows tissue to cool between pulses, thus significantly decreasing the potential for lateral thermal damage (tissue cools most efficiently when duration between pulses exceeds the thermal relaxation time).
For most cutting precision and speed, the laser tip should be maintained 1 to 3 millimeters away from the target tissue. Traction and countertraction of tissue with surgical sponges and tissue forceps facilitate incisional surgical technique. To achieve hemostasis, the continuous wave mode is most efficient. Hemostasis also can be achieved by defocusing the laser energy (increasing the laser tip-to-tissue distance increases laser beam spot size and reduces power density). The ability of the CO2 laser to coagulate tissue during incision is especially valuable for tongue surgeries due to the richness of the tongue’s blood supply.
Here, five clinical cases exemplify the use of a flexible fiber CO2 laser (Aesculight®, manufactured by LightScalpel LLC, Bothell, Wash.) for tongue surgeries at our practice.
Case 1: Benign Mass Excision
A dog owner noted a mass on the dog’s tongue. The sample was excised and sent for histopathology, which revealed a fibroma with complete excision with excellent prognosis. For this procedure, the Aesculight laser was set to 6 watts in the continuous wave mode. The laser focal spot size was 0.8 millimeters.
Case 2: Ranula Removal
In this case, a canine patient presented with a 25-millimeter- by-20-millimeter fluctuant, erythematous mass located sublingually—a ranula. The mass was ulcerated from repeated contact with the teeth. Ranulas result from damage to the sublingual or mandibular duct or gland. Due to the vascularity of the area, it was decided to excise the mass with the CO2 laser. For this procedure, the Aesculight laser was set to 8 watts and used in the continuous wave mode with a larger focal spot size of 0.8 millimeters to achieve more hemostasis. The surgical defect was then sutured with monofilament absorbable 4-0 suture.
Case 3: Sublingual Granuloma Excision
A dog presented for granulated tissue that had formed on the ventral surface of the tongue—a sublingual granuloma. Sublingual granulomas, also called “gum-chewing lesions,” occur secondary from trauma of caudal sublingual tissues from the mandibular cheek teeth. Initial treatment involved excision of the excess tissue followed by primary closure. The CO2 laser was set to 6 watts in the continuous wave mode. The laser focal spot size was 0.4 millimeters to 0.8 millimeters.
Case 4: Malignant Mass Excision
A 9-year-old Chow mix was presented in respiratory difficulty. After preoperative workup, including normal blood tests and thoracic radiographs, the dog was anesthetized and examined, and a large mass obstructing its oropharynx was revealed. Fortunately, the mass was attached to the tongue via a pedicle that allowed laser and scalpel excision. Upon awaking, the dog could breathe normally. Malignant melanoma was diagnosed with incomplete excision. Melanoma vaccine was administered. Regrowth of the melanoma reoccurred 14 months after surgery. In this case, the CO2 laser was set to 10 watts in the continuous wave mode with a 0.8-millimeter focal spot size.
Case 5: Ulceration
The CO2 laser is successfully used to photovaporize oral ulceration in human and veterinary medicine. CO2 laser treatment usually results in pain relief and quick return to function. In this case, an FIV-positive cat presented for excessive salivation. Marked tongue ulceration was part of the presentation. Six laser treatments were necessary to resolve the tongue lesion after full-mouth extraction. For the treatment of tongue ulceration, the laser was set to 2 watts in the continuous wave mode, and the wide ablation nozzle was used.
Dr. Bellows is board certified by the Board of Veterinary Practitioners (canine and feline) and by the College of Veterinary Dentistry. He is past president of the American Veterinary Dental College and the Veterinary Dental Forum. Currently he is president of the Foundation for Veterinary Dentistry.
This Education Center article was underwritten by Aesculight of Bothell, Wash., the manufacturer of the only American-made CO2 laser.
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