10.1
Introduction
Benign parotid tumors have historically been treated by parotidectomy focused on the complete resection of the neoplasm with facial nerve preservation.
Parotid masses were formerly managed via surgical enucleation, as first described by Béclard in 1824 with the aim of avoiding any facial nerve damage. , Nonetheless, tumor recurrence was pointed out in the mid-50s as the main risk of enucleation. Since then, several modalities were used to treat patients with parotid tumors depending on the cytological nature and localization: extracapsular enucleation; removal of the tumor with a limited cuff of normal parotid tissue; superficial parotidectomy; subtotal resection of the parotid gland; and total parotidectomy.
Regardless of the indication for surgery and the nature of the lesions, parotidectomy is a challenging procedure requiring skilled surgeons due to the anatomical proximity of the facial nerve. The facial nerve identification itself is the key point in the outcome of this procedure, second only to the radicality of the resection.
Facial nerve identification can be achieved with two approaches: anterograde or retrograde dissection. It was advocated by Janes and Bailey to prior identify the main trunk of the facial nerve and subsequently to perform the parotidectomy. The anterograde approach allows the facial nerve identification at its emerge from the stylomastoid foramen. Using this technique, the reported recurrence rate and permanent facial nerve paralysis rate become very rare, decreasing to 0.2% and 2.2%, respectively. In case of the lack of anatomical landmarks, revision surgery, or very bulging tumor, the detection of the main trunk of the facial nerve by an anterograde approach may be challenging. In such cases, the retrograde approach is crucial for nerve preservation avoiding spillage of the tumor. It consists of prior identification of a distal branch of the nerve and subsequently dissecting back to the main trunk.
Regardless of the nerve identification technique (whether anterograde or retrograde), its intraoperative preservation is supported by several tools such as loupes or the operative microscope. Although the loupes provide an excellent view, allowing for good dissection, the magnification is restricted to the surgeon unless coupled to a head microcamera. Microscope-assisted surgery offers high-intensity light and high magnification to the surgeon who works with a 3D view, but images are usually presented to the observers with 2D monitors with an unavoidable lack of depth-of-field information.
The exoscope has been introduced as an alternative to a microscope in neurosurgery for 2D and, more recently, 3D viewing to overcome these limits. It consists of a rigid rod lens video telescope that is suspended above the surgical field and displayed the image to a high-definition (HD) monitor in front of the surgeon (see Chapter 1 ). Recently, the use of 3D exoscopes has spread suitable for many surgical specialties such as gynecology, urology, and ENT. Thanks to the compact size and the high-quality images offered by the 3D-HD magnification, its use turned out to be ideal for parotid surgery, as reported in recently published preliminary experiences. ,
10.2
Operating room setting
The operating room layout is configured to allow the surgeons to work closely to the surgical field and the scrub nurse to have an adequate range of movement to help the surgeons.
The 3D-HD exoscope (3D Vitom, Karl Storz, Tuttlingen, Germany) is positioned on the side of the first surgeon, approximately 30 cm from the surgical field. The main 55-in. 4K 3D monitor is positioned in front of the surgeon, at the eye level, while the second 3D monitor is oriented to allow the scrub nurse and assistants to have a good view ( Figs. 10.1 and 10.2 ).
The surgeon is positioned on the left/right of the head of the patient (on the basis of the side of the lesion). The scrub nurse stands next to the first surgeon. The assistant stands at the patient’s head, using the controller (IMAGE1 PILOT) covered with a sterile coating, to adjust the optical magnification and maintain the focus of the camera on the surgical field ( Fig. 10.3 ). This position allows an easy view of the intraoperative nerve-monitoring device (Medtronic NIM Response 3.0), which is placed at the bottom of the surgical bed.
The use of polarized glasses is mandatory for all the theater attendants to perceive the 3D image.
10.3
Surgical technique
The surgical procedure is performed using the same surgical technique as in conventional parotid surgery, but the novelty is that the surgeon works with a direct vision to a 3D-HD 4K monitor, using polarizing eyeglasses, with a magnification of the anatomic structures from 8 to 30 times. The procedure is carried out under general anesthesia performed by nasotracheal intubation. The facial nerve function is monitored intraoperatively by a nerve integrity monitor (NIM) (Medtronic NIM Response 3.0 – 4 channels).
A modified Blair incision is usually performed, but a facelift incision can be preferred in selected cases. The anterior skin flap is elevated in the plane superficial to the parotid fascia. The great auricular nerve is preserved where possible to reduce the numbness of the auricular region in the postoperative period. The posterior belly of the digastric muscle is identified, and the parotid gland is mobilized from the tragal cartilage until the tragal pointer is reached. The main trunk of the facial nerve is identified where it emerges from the stylo-mastoid foramen, following the three classical landmarks: the tragal pointer, the tympano-mastoid suture, and the posterior belly of the digastric muscle. In selected cases in which the deepest aspect of the tumor is in wide contact with the main trunk of the nerve, a retrograde dissection of a peripheral facial nerve branch can be useful. Once the main trunk of the facial nerve is identified, it must be followed distally to the pes anserinus and the secondary branches, dividing the parenchyma that lies superficial to the nerve. Meticulous and blunt dissection of the peripheral branches is essential to avoid facial nerve injury. The use of the 3D exoscope allows for a great magnification of the finer branches, reducing the risk of facial nerve lesions. The assistant provides constant high-quality images, adjusting the magnification and maintaining the focus on the surgical field using the IMAGE1 PILOT.
The parotid tissue is progressively dissected free of the nerve until the superficial lobe is resected (type I–II parotidectomies according to the European Salivary Gland Society ). If the tumor is located in the deep lobe, after the resection of the superficial lobe, the procedure is extended by meticulous dissection of the main trunk and branches of the facial nerve from the underlying parotid tissue, until the deep parotid lobe is removed (type I–IV parotidectomies according to the European Salivary Gland Society ).
Thanks to the exoscope, the entire surgical team can benefit from the presence of 3D vision. In fact, it allows to directly experience all surgical steps, appreciating contextually all surgeon’s fine gestures.
10.4
Outcomes
Eighteen cases of exoscopic parotidectomy have been reported in the literature so far , ( Table 10.1 ).
| Pt/sex/age | Localization | Surgical treatment | Operation time (min) | Postoperative facial nerve function | Other complications | Histology | |
|---|---|---|---|---|---|---|---|
| Carta 2020 | 1/F/47 | Superficial lobe | Type I–II | 145 | Normal | No | Pleomorphic adenoma |
| 2/M/74 | Superficial lobe | Type I–II | 195 | Normal | No | Pleomorphic adenoma | |
| 3/M/60 | Superficial lobe | Type I–II with retrograde facial nerve dissection | 210 | Normal | No | Pleomorphic adenoma | |
| 4/M/65 | Superficial lobe | Type I–II | 170 | Normal | No | Warthin’s tumor | |
| 5/F/33 | Superficial lobe | Type I–II | 120 | Grade II | No | Pleomorphic adenoma | |
| 6/M/48 | Superficial lobe | Type I–II | 115 | Normal | No | Warthin’s tumor | |
| 7/M/42 | Superficial lobe | Type I–II | 135 | Normal | No | Pleomorphic adenoma | |
| 8/F/42 | Superficial lobe | Type I–II | 140 | Normal | No | Pleomorphic adenoma | |
| 9/M/19 | Superficial lobe | Type I–II | 115 | Normal | No | Pleomorphic adenoma | |
| Mincione 2020 | 1/M/37 | Superficial lobe | Type II | 135 | Normal | No | Pleomorphic adenoma |
| 2/M/59 | Superficial lobe | Type I | 138 | Normal | No | Pleomorphic adenoma | |
| 3/F/41 | Superficial lobe | Type II | 137 | Normal | No | Pleomorphic adenoma | |
| 4/M/68 | Superficial lobe | Type I–II | 142 | Normal | No | Warthin’s tumor | |
| 5/F/28 | Superficial lobe | Type II | 148 | Normal | No | Pleomorphic adenoma | |
| 6/M/72 | Deep lobe | Type III | 165 | Normal | No | Pleomorphic adenoma | |
| 7/F/75 | Superficial lobe | Type II | 138 | Normal | No | Warthin’s tumor | |
| 8/M/47 | Superficial lobe | Type I–II | 157 | Normal | No | Pleomorphic adenoma | |
| 9/F/61 | Superficial lobe | Type II | 145 | Normal | No | Warthin’s tumor |
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