INTRODUCTION: Endoscopic endonasal approach (EEA) for resection of multicompartiment skull base tumors is often limited due to bilateral and inferior tumor extension into the retrostyloid parapharyngeal space (PS) and upper cervical region. In order to achieve gross total resection (GTR), open anterior or lateral corridors such as trans-oral, trans-parotid, transcervical, extreme-lateral or combined approaches can be indicated in selected cases. However, such procedures are time-consuming and can be associated with high morbidity and complications. In an attempt to minimize approach-related morbidity, we designed a minimally invasive, keyhole, endoscopic-assisted transcervical (MIKET) approach as an alternative and an adjunct for achieving GTR, complementing EEAs. We describe the relevant anatomy, key landmarks and optional extensions.
METHODS: Three colored silicone-injected anatomical specimens (6 sides) were dissected in the Surgical Neuroanatomy Lab at the University of Pittsburgh Medical Center. In addition to the MIKET approach on one side, we performed a combined transmastoid infralabyrinthine transcervical approach (TITA) on the contralateral side to compare and obtain high quality photographs and detailed anatomical descriptions. Image guided navigation was used for bony landmark identification.
RESULTS: For the MIKET approach, an inverted 5 cm hockey stick incision 1 cm behind the ear and 2 cm above the tip of the mastoid (M) was made, skin was dissected away from the invest layer of deep cervical fascia (IL) to allow the skin flap for mobility preserving the posterior auricular nerve (*) (Figure 1); a strip of sternocleidomastoid (SCM) and splenius capitis was cut and underlying muscles were dissected posteriorly in a subperiostial fashion to expose the mastoid and identify the posterior belly of digastric muscle (PBD). In a corridor posterior to the parotid gland (P) and anterior to the cervical muscles, fascia and fat were removed; the PBD tendon was cut above the level at which the accessory nerve (XI) crosses towards the SCM and the occipital artery (OA) was sacrificed. This allowed exposure of the internal jugular vein (IJV) and C1 transverse process (TP), along with the muscles inserted on it (Figure 2). Further facial nerve (FN), PS and sigmoid part of the jugular foramen (JF) were exposed by adding an infralabyrinthine mastoidectomy, superior oblique (SO) and lateral rectus muscle (LRC) detachment and jugular process (JP) drilling, respectively (Figure 3). Following the digastric branch to PBD into the stylomastoid foramen allowed for early FN identification and preservation. Unless the IJV is thrombosed or transected, the lower cranial nerves (LN) and internal carotid artery will remain safe and hidden antero-medial to it inside the carotid sheath.
CONCLUSIONS: MIKET approach can reach the upper cervical and parapharyngeal space through a natural corridor with minimal dissection and without injuring important neurovascular structures and offers similar surgical view compared to open approaches. Next steps would include application in a clinical setting to evaluate its efficacy and safety.
KEY WORDS: Retrostyloid parapharyngeal space · upper cervical · endoscopic-assisted · minimally invasive · keyhole approach
Figure 1.
Figure 2.
Dotted line: overimposed endoscopic view.
Figure 3.
