Mandibular Third Molar Surgery: Intraosseous Localization of the Inferior Alveolar Nerve Using 3D Double-Echo Steady-State MRI (3D-DESS).

Adib Al-Haj Husain,Marco Piccirelli,Marcel Müller,Sebastian Winklhofer,Bernd Stadlinger,Silvio Valdec

doi:10.3390/diagnostics11071245

Adib Al-Haj Husain, Marco Piccirelli + Show 4 more

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https://doi.org/10.3390/diagnostics11071245

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Abstract

The aim of this study was to evaluate the inferior alveolar nerve’s (IAN) intraosseous position within the inferior alveolar canal (IAC) using a 3D double-echo steady-state MRI sequence (3D-DESS). The IAN position was prospectively evaluated in 19 patients undergoing mandibular third molar (MTM) surgery. In the coronal reference layer, the IAC was divided into six segments. These segments were checked for the presence of hyperintense tubular MRI signals representing the IAN’s nervous tissue and assessed as visible/non-visible. Furthermore, the IAN in MRI and the IAC in MRI and CBCT were segmented at the third and second molar, determining the maximum diameter in all planes and a conversion factor between the imaging modalities. Regardless of the positional relationship at the third and second molar, the IAN showed the highest localization probability in the central segments (segment 2: 97.4% vs. 94.4%, segment 5: 100% vs. 91.6%). The conversion factors from IAC in CBCT and MRI to IAN in MRI, respectively, were the following: axial (2.04 ± 1.95, 2.37 ± 2.41), sagittal (1.86 ± 0.96, 1.76 ± 0.74), and coronal (1.26 ± 0.39, 1.37 ± 0.25). This radiation-free imaging modality, demonstrating good feasibility of accurate visualization of nervous tissue within the nerve canal’s osseous boundaries, may benefit preoperative assessment before complex surgical procedures are performed near the IAC.

Highlights

Accurate preoperative visualization of the inferior alveolar nerve (IAN), the largest branch of the mandibular nerve located within the inferior alveolar canal (IAC), is of clinical interest to minimize the risk of nerve injury during various dentoalveolar surgical interventions such as orthognathic surgery [1], dental implant insertion [2], mandibular block analgesia [3], and surgical extraction of mandibular third molars (MTM) [4]
This prospective cohort study included 23 patients, recruited between May 2018 and December 2018, with an indication for removal of retained or impacted MTMs with a positional relationship to the IAN, indicating three-dimensional imaging according to the guiding principles of the Swiss association of dentomaxillofacial radiology
At the third and second molar level, it can be stated that the conversion factor between the IAC in cone-beam computed tomography (CBCT) and IAC in magnetic resonance imaging (MRI) and IAN in MRI, respectively, showed no significant differences in all planes except the axial plane at the third and the coronal plane at the second molar (Figure 6)

Summary

Introduction

Iatrogenic injury to the IAN resulting from third molar surgery leads to sensory disorders, ranging from partial loss of sensitivity to complete neurosensory loss [5]. The frequency of these neurosensory disorders is reported in the literature to be approximately 4% (0.4%–8.4%) [5,6]. Full recovery occurs within the first 6 to 8 weeks postoperatively; if not, the probability of permanent neurosensory deficiency increases remarkably [8] This can lead to a loss of quality of life, often accompanied by psychological and social complaints [9]

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