3D exoscopic parotidectomy

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