Localization of Parotid Gland Tumors in Relation to the Intraparotid Facial Nerve on 3D Double-Echo Steady-State with Water Excitation Sequence

Abstract

BACKGROUND AND PURPOSE: Reliable preoperative facial nerve mapping may help avoid or minimize facial nerve injury during parotid tumor resection. The purpose of this study was to investigate the diagnostic performance of the 3D double-echo steady-state with water excitation sequence in localizing parotid gland tumors through direct visualization of the intraparotid facial nerve in comparison with indirect methods of estimating the facial nerve location. MATERIALS AND METHODS: We retrospectively reviewed 91 parotid gland tumors in 90 patients who underwent surgical resection and preoperative MR imaging, including the 3D double-echo steady-state with water excitation sequence. The tumor locations were categorized as deep or superficial on the basis of direct and 3 indirect methods: the facial nerve line, retromandibular vein, and Utrecht line. Surgical localization was considered the criterion standard. The diagnostic performance for localizing deep lobe lesions using direct and indirect methods was calculated and compared using the McNemar test. RESULTS: Surgical localization confirmed 75 superficial lesions and 16 deep lesions. The interobserver variability of the 3D double-echo steady-state with water excitation sequence was excellent (ϭ 0.870). The diagnostic accuracy, sensitivity, specificity, positive predictive value, and negative predictive value for localizing deep lobe lesions using the 3D double-echo steady-state with water excitation method were 97.8%, 87.5%, 100%, 100%, and 97.4%, respectively. These findings were significantly higher than the facial nerve line in sensitivity, the retromandibular vein in sensitivity, and the Utrecht line in accuracy and specificity (P Ͻ .05). Overall, the direct method was the most accurate, sensitive, and specific in localizing parotid gland tumors. CONCLUSIONS: We can achieve higher diagnostic performance in localizing parotid gland tumors by directly visualizing the intraparotid facial nerve using the 3D double-echo steady-state with water excitation sequence compared with indirect methods. ABBREVIATIONS: 3D-DESS-WE ϭ 3D double-echo steady-state with water excitation; FNL ϭ facial nerve line; RMV ϭ retromandibular vein; UL ϭ Utrecht line

Incidence of postoperative facial weakness in parotid tumor surgery: a tumor subsite analysis of 794 parotidectomies

“…In the present study, preoperative CT allowed us to estimate the positional relationship between the imaginary facial nerve line and the tumor before surgery. However, this indirect method on CT images showed only a modest diagnostic accuracy for localization of parotid tumors in relation to the facial nerve [37]. Thus, the tumor subsites in this study were classified based on the surgical findings, not on the CT images.…”

“…Thus, the tumor subsites in this study were classified based on the surgical findings, not on the CT images. Recent advanced techniques of magnetic resonance imaging may have clinical benefit of more accurate surgical planning by directly visualizing the facial nerve in the parotid gland [37].…”

“…In this study, we routinely applied preoperative computed tomography (CT) scans, intraoperative facial nerve monitoring, and surgical magnification for all parotidectomies, which is different from the previous studies. Preoperative CT scans is known to have a modest diagnostic accuracy for localization of parotid tumors in relation to the facial nerve using an imaginary facial nerve on images [37]. Thus, CT scans have some diagnostic limitations compared with the direct visualization of the facial nerve by advanced techniques of magnetic resonance imaging (MRI) [37].…”

“…Preoperative CT scans is known to have a modest diagnostic accuracy for localization of parotid tumors in relation to the facial nerve using an imaginary facial nerve on images [37]. Thus, CT scans have some diagnostic limitations compared with the direct visualization of the facial nerve by advanced techniques of magnetic resonance imaging (MRI) [37]. However, preoperative CT could provide the gross characteristics of tumors in the parotid gland, approximate location of tumors, and sketchy surgical planning.…”

MR Imaging of the Extracranial Facial Nerve with the CISS Sequence

“…10,11 Steady-state imaging with the gradient-recalled acquisition in steady state sequence 12 and double-echo steadystate with water excitation sequence 20 have previously been reported for facial nerve imaging with more inconsistent identification of the cervicofacial and particularly temporofacial trunks, though the double-echo steady-state with water excitation sequence has recently been shown to allow accurate categorization of tumor location to the superficial or deep parotid lobes. 21 Our success in this study may be attributable to the use of more technologically advanced hardware. Use of a PSIF-DWI sequence to visualize at least a portion of the cervicofacial and temporofacial branches has more recently been described, 13 and the images obtained with the CISS protocol (eg, Fig 2) seem comparable with the published PSIF-DWI, which was obtained with a small surface coil and postprocessed into MPR and MIP images.…”