In this retrospective study, we hypothesized that ADC values change in cervical lymph nodes that were affected by MRONJ. The findings of this study revealed that the ADC values of cervical lymph nodes that were affected by MRONJ were significantly higher than those of normal lymph nodes.
After several revisions, the term, BRONJ, was changed to MRONJ by the AAOMS in 2014 because jawbone necrosis was clearly caused not only by bisphosphonates, but also by immunosuppressants and anti-angiogenic drugs [4, 17]. MRONJ causes severe dysfunction and masticatory disorders due to jawbone necrosis and the associated effects on surrounding tissues, including the cervical lymph nodes, and can even lead to death [25].
Approximately 300 lymph nodes can be found in the head and neck [22, 23]. Most lymphatic fluid from the oral area is drained into the submental, submandibular, and superior internal jugular nodes, which are deep cervical lymph nodes [26]. Thus, these cervical lymph nodes may significantly be affected by inflammation and malignant diseases in the maxillofacial area. Furthermore, lymph node metastasis of oral malignancies has a significant influence on treatment and prognosis with a 50% 5-year survival rate for unilateral cases and lower survival rate for bilateral cases [27]. Imaging modalities such as ultrasonography (US), CT, and MRI play major roles in assessing enlargements and internal properties in lymph nodes. DWI can evaluate the diffusivity of water molecules in the region and help obtain the ADC value, which is a quantitative parameter. Many recent studies have reported the usefulness of ADC, which was obtained using DWI which allows for tissue characterization at the microscopic level, in identifying the causes of lymph node diseases [15, 16, 28–30]. However, little attention has been placed on the potential use of DWI in the quantitative assessment of lymph nodes that were affected by MRONJ.
In the present study, the mean ADC value of lymph nodes that were affected by MRONJ was significantly higher than that of non-affected lymph nodes. Previous studies have shown that the mean ADC values for reactive and metastatic lymph nodes were 1.24×10–3 mm2/s and 0.78×10–3 mm2/s, respectively [16]. Furthermore, other studies have shown that the mean ADC values for reactive lymphadenopathy, metastatic, and lymphoma were 1.64×10− 3 mm2/s, 1.09×10− 3 mm2/s, and 0.97×10− 3 mm2/s, respectively [12]. In addition, the ADC values of the submandibular and superior internal jugular nodes that were affected by suppurative acute osteomyelitis were 1.10 ± 0.18×10− 3 mm2/s and 1.05 ± 0.2×10− 3 mm2/s, respectively [15]. These different results may be due to differences such as choice of b values and ROI selection. In this study, the ADC values of lymph nodes that were affected by MRONJ were high and relatively close to the reported values in reactive lymphadenopathy in previous studies. This may be due to the increased perfusion and diffusion owing to the increased lymphatic flow and cell stroma because of inflammatory changes. Moreover, ROC curve analysis indicated cutoff ADC values of 0.86 (level IB) and 0.88 (IIA) for lymphadenopathy due to MRONJ. These cut-off ADC values showed a diagnostic efficacy value of 0.81–0.84 and above, with an AUC of 0.86–0.88, for predicting lymph nodes that were affected by MRONJ. These results indicate that ADC has good sensitivity, specificity, and accuracy and can be beneficial in distinguishing between MRONJ-affected and normal lymph nodes.
One limitation of this study is that the sample size was limited due to its retrospective design. Second, lymph nodes, with severe image distortion due to magnetic susceptibility artifacts, could not be measured. Third, some nodes could not be measured due to the 6-mm slice thickness used.
In conclusion, the ADCs of lymph nodes that were affected by MRONJ were significantly higher compared to that of non-affected lymph nodes, suggesting that MRONJ causes inflammatory changes in the cervical lymph nodes.