Several approaches to the nasal cavities and frontal sinuses have been described. A dorsal approach is still classically performed with a bone flap being removed from one or both nasal bones. Repositioning of the bone flap is recommended to avoid increased risks of post operative subcutaneous emphysema and facial deformity. Intractable bleeding may require temporary ligation of the internal carotid artery and subsequently repositioning of the patient. Cosmetic appearance of the patient following dorsal rhinotomy is often difficult to accept for the owner.
Alternatively a ventral approach to the nasal cavity has been proposed offering more acceptable cosmetic results, less invasive technique with lower complication rate. This technique does not require patient repositioning when internal carotid ligation is required by intra operative bleeding. However controversies exist concerning the use of this approach to reach frontal sinuses. The frontal sinuses extend very far caudally on the head. There are three compartments of the frontal sinuses. These include the large caudal compartment and smaller rostral and medial compartments. The latter drain via an ostia into the caudodorsal nasal cavity. The floor of the frontal sinuses extends over the olfactory and rostral part of the frontal lobes of the brain. A morphological and anatomical study is actually conducted in order to assess the feasibility to explore the entire volume of the frontal sinuses through a ventral rhinotomy approach. This study is considering species (dog and cat) and breed (dolico-mesocephalic versus brachycephalic) anatomical variations.
Indications for ventral rhinotomy include removal of nasal and nasopharyngeal foreign bodies, cytoreduction or biopsy of nasal tumours, aspergillosis treatment.
Surgery of the nasal cavities are often blood consuming surgeries. Careful pre-operative assessment of the patient is required. Pre-operative blood analysis including complete blood cell count, biochemistry, urinanalysis, coagulation profile, and von Willebrand's factor level in suspect breeds should be performed. Blood transfusion may be scheduled during surgery when severe blood loss is present.
The ventral approach to the nasal cavity is made through a midline incision in the hard palate mucoperiosteum. The incision can be made over the entire palatine length. A periosteal elevator is used to elevate the mucoperiosteum which is elevated laterally to the alveolar ridge. Care should be taken to avoid lacerating the major palatine arteries as they exit the caudal palatine foramina at the level of the fourth premolar in the dog or the third premolar in the cat. Electrocautery can be used to minimize bleeding. This bleeding usually resolves within a few minutes with or without digital pressure. A mini oscillating saw is used to create a bone flap on the affected side. Surgical suction is mandatory to remove blood and debris from the operating field. Blood loss should be quantified during surgery in order to allow therapeutic measures to replace blood and to prevent hypotension: blood transfusion, colloid infusion, internal carotid ligature.
The use of a rigid or flexible endoscope of the appropriate size can assist the exploration of the nasal cavity and frontal sinuses. Copious flushing/aspiration is necessary to improve visualization of the intranasal and intrasinusal structures.
The approach can be extended of the opposite side. A contro-lateral bone flap can be created. When the nasal septum is damaged by the disease, rongeurs can be used to enlarge the initial opening in the hard palate. The approach can also be extended caudally toward the nasopharynx.
Bone flaps are not preserved for closure. Most of the time they should be submitted for histopathology. The nasal cavities and sinuses are copiously flushed prior to closure. Haemostatic dissolvable swabs can be packed into the nasal cavity to reduce post operative bleeding. The mucoperiosteal flaps are replaced in their normal position. Absorbable or non absorbable (in cats) monofilament suture material is used to suture the mucoperiosteum in a simple interrupted suture pattern.
Post-operative complications related to the ventral rhinotomy are usually minimal. Cases of wound dehiscence with oro-nasal fistulae formation have been mentioned in the literature. A delayed second surgery is performed to close the defect.
When appropriate pre and post operative analgesia has been be performed, post-operative morbidity and discomfort is less than that after dorsal rhinotomy. Patients, even cats, eat shortly after recovery from anaesthesia. They should be given soft food until complete healing of the wound.