Oral Radiology

, Volume 29, Issue 2, pp 111–120 | Cite as

Role of magnetic resonance imaging in diagnosis of bisphosphonate-related osteonecrosis of the jaw

Original Article

Abstract

Objectives

To clarify the magnetic resonance (MR) imaging features of bisphosphonate-related osteonecrosis of the jaw (BRONJ), particularly those in the early stage, through a literature review and case analysis.

Methods

Literature on MR imaging of BRONJ was collected, and the MR imaging features were summarized. On MR images of patients with BRONJ, the signal intensity of the bone marrow was evaluated quantitatively by means of the contrast-to-noise ratio (CNR). The relationships of the imaging features with the presence of exposed bone, types and administration routes of bisphosphonates (BP), and duration of symptoms were investigated.

Results

Fifteen articles were identified. In the early stages, the region of osteonecrosis displayed decreased signal intensity on T1-weighted images and normal signal intensity on T2-weighted images. In the late stages, the signal intensity of the bone marrow on T2-weighted images was variable: the exposed diseased bone displayed decreased signal intensity, and the unexposed diseased bone displayed increased signal intensity. These changes were also seen in BRONJ cases. There was a significant difference in the CNR between the exposed and unexposed diseased bones on STIR images. There were no significant differences in the CNR among the three groups by types and administration routes of BP, both on T1-weighted and STIR images. Changes in the signal intensity of bone marrow were seen at the early duration of symptoms. In the early stage, the CNR on T1-weighted images had a significant correlation with duration of symptoms.

Conclusion

MR imaging may provide visualization of useful features in the early stage of BRONJ.

Keywords

MRI Bisphosphonate-related osteonecrosis Jaw 

Introduction

Bisphosphonates (BP) are widely used to treat a variety of bone diseases, including osteoporosis, Paget’s disease, osteogenesis imperfecta, osteolytic bone lesions of multiple myeloma, and bone metastases from breast and prostate cancer [1, 2, 3]. Reported side effects of BP include flu-like symptoms, fatigue, gastrointestinal reactions and edema, and mucous ulcerations [4, 5]. Bisphosphonate-related osteonecrosis of the jaw (BRONJ) can severely affect quality of life and can even become the major concern of cancer patients because of pain and difficulties in maintaining oral hygiene and eating [6, 7]. A number of articles detailing the clinical aspects of this condition have appeared [8, 9]. BRONJ is a difficult-to-treat condition associated with morbidity and potential complications [10].

Imaging may demonstrate the extent of BRONJ before surgical intervention and complications such as pathological fractures [10]. Some articles have reported the imaging features of BRONJ [6, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23]. Bedogni et al. [11] compared CT and magnetic resonance (MR) imaging features with those of histopathologic examination; in particular, bone alternations exhibited great variation between exposed and unexposed areas. Morag et al. [10] presented a pictorial review, and other articles showed pictorial case presentations of BRONJ [6, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23]. Changes associated with BRONJ were apparent using various imaging modalities, whereas the findings were typically nonspecific [10].

Early signs of BRONJ on imaging can provide useful information. There are a few reports of imaging features based on differences in the duration of symptoms [10, 16]. Especially in the early stage, there is little information on the typical imaging features. Bisdas et al. [16] showed MR imaging features of the region of osteonecrosis in patients with BRONJ with early and intermediate symptoms, particularly decreased signal intensity on T1-weighted images and normal signal intensity on T2-weighted images. MR imaging can detect mandibular osteomyelitis in patients in the early stages of BRONJ without positive features of osteomyelitis on CT or other conventional images [24]. A detailed imaging investigation of BRONJ in the early stages can ensure effective treatment and a good prognosis.

In the present study, we clarify the MR imaging features of BRONJ, especially those in the early stage, through a review of the literature and analysis of our patients with BRONJ.

Materials and methods

Review of the literature on MR imaging characteristics

To clarify the MR imaging features of BRONJ, a search of the literature was performed using the keywords “bisphosphonate,” “jaw,” and “MRI” in the MEDLINE database (PubMed) between 2003 and 2012. We agreed on the following inclusion and exclusion criteria:
  1. 1.

    Only studies of humans were included.

     
  2. 2.

    Only studies written in English or Japanese were included.

     
  3. 3.

    Original articles, case reports, and review articles were included.

     
  4. 4.

    Studies in which the authors described the MR images of only the underlying primary disease were excluded.

     
  5. 5.

    Studies in which the authors neither showed the MR images nor described the image findings were excluded.

     
  6. 6.

    Studies in which the final histological diagnosis was not BRONJ were excluded.

     

We summarized the MR imaging features and the pathology of bone marrow based on the collected articles.

Evaluation of MR imaging features of our patients

Patients

Thirteen patients (1 male and 12 females) were enrolled in this study. The average age was 75.1 ± 4.6 years (range, 66–82 years). All patients were selected retrospectively from the files of our department between 2003 and 2012. Criteria for inclusion into this study were as follows: patients were medicated with bisphosphonates (BP) for osteoporosis or cancer for 2 years or longer, visited our hospital because of maxillofacial symptoms, and underwent MR examination. They were not undergoing radiation therapy. Only patients with a first occurrence of symptoms, such as exposed bone of the mandible, percussion and spontaneous pain of the teeth, swelling, redness, fistula and pus discharge of the lower gingiva, swelling and spontaneous pain of the buccal or submandibular region, paralysis of the lower lip, and/or trismus, were included. Patients with and without exposed bone were included.

Details of the patients are shown in Table 1. In terms of the type of BP and route of administration, three patients were medicated with zoledronic acid (Zometa) by intravenous drip, seven were medicated with alendronate (Bonaron) by oral administration, and three were medicated with risedronate (Actonel or Benet) by oral administration. The period between the onset of maxillofacial symptoms and MR examination ranged from 5 days to 43 months, with a median of 2.0 months. Exposed bone was seen in seven patients, and anamnesis of tooth extraction was found in six patients.
Table 1

Summary of our patients

Patient no.

Age (years)

Gender

Underlying disease

Bisphosphonates

Duration of symptoms (months)c

Exposed bone

Anamnesis of tooth extraction

Typesa

Administration routesb

Dosing duration (months)

1

69

Female

Breast cancer

Zol

i.v.

36

0.2

+

2

76

Female

Breast cancer

Zol

i.v.

36

2

+

+

3

73

Female

Breast cancer

Zol

i.v.

36

4

4

76

Female

Osteoporosis

Ale

p.o.

36

2

+

+

5

77

Female

Osteoporosis

Ale

p.o.

43

18

+

6

82

Female

Osteoporosis

Ale

p.o.

24

24

+

7

80

Male

Malignant lymphoma

Ale

p.o.

28

0.3

8

81

Female

Osteoporosis

Ale

p.o.

36

0.6

+

9

73

Female

Osteoporosis

Ale

p.o.

72

1.5

10

66

Female

Osteoporosis

Ale

p.o.

>60

43

11

74

Female

Osteoporosis

Ris

p.o.

36

2

+

+

12

75

Female

Osteoporosis

Ris

p.o.

40

3

+

+

13

80

Female

Osteoporosis

Ris

p.o.

60

1

+

aZol zoledronic acid (Zometa), Ale alendronate (Bonaron), Ris risedronate (Actonel or Benet)

bi.v. intravenous drip, p.o. oral administration

cDuration between the onset of symptoms and MR examination

MR imaging examination

MR imaging examination was performed with a 1.0-T Magnex (Shimadzu, Kyoto, Japan) or a 1.5-T Magnetom (Siemens, Tokyo, Japan) and a head coil. Standard MR imaging sequences were performed as follows: spin-echo T1-weighted images [450–500/11–18 ms (repetition time/echo time)]; T2-weighted short T1/tau inversion recovery (STIR) images [2800–3200/22/90–110 ms (repetition time/echo time/inversion time)]. The section thickness was 5.0 mm with an intersection gap of 1.0 mm. The acquisition matrix was 256 × 256. Axial and coronal images were obtained.

MR images were evaluated in terms of the signal intensity of the bone marrow, presence of sequestra, and involvement of the adjacent soft tissue. A sequestrum was described as a low-signal-intensity center on both T1-weighted and STIR images accompanied by a high-signal area on STIR images (Fig. 1). When the adjacent soft tissue including the periosteum showed swelling and increased signal intensity on STIR images, soft tissue involvement was determined to be present (Fig. 1).
Fig. 1

A 74-year-old female (patient no. 11). This patient was treated for osteoporosis with oral risedronate for 3 years. She underwent extraction of the right second molar 1 year previously. She had complained of swelling and spontaneous pain of the region of the right second molar for 2 months. An intraoral photograph showed exposed bone in this region (a). Panoramic radiography displayed a sequestrum in the region and sclerotic change of the whole right mandible, extending to the lower border and the ramus (b). The exposed bone (white arrow) displayed low signal intensity on T1-weighted (c) and STIR (d) MR images. It was surrounded by a high-signal-intensity zone on STIR images. Bone marrow in the distal region (asterisk) displayed low signal intensity on T1-weighted images and slightly high signal intensity on STIR images. The periodontal ligament space (white arrowhead) showed expansion and increased signal intensity on STIR images. The adjacent soft tissue (black arrow) showed swelling and increased signal intensity on STIR images

Evaluation of signal intensity of bone marrow

The change in the signal intensity of the bone marrow was analyzed according to the following method. The signal intensity of bone marrow was evaluated quantitatively on T1-weighted and STIR images. The regions of interest (ROIs) were set in the cancellous bones in the exposed area, the unexposed diseased area, and the opposite healthy area so that the pixel sizes were as large as possible (Fig. 2). The ROI size ranged from 900 to 1200 pixels. The signal intensities of the ROIs and the background noise were measured. All measurements were performed by one examiner (Y.A.) using two or three consecutive sectional images in which the diseased bone was represented as the maximum. The mean value of two or three measurements was obtained.
Fig. 2

Method of determining the ROI. The ROI was determined on two or three consecutive sectional images in which the diseased bone was represented as the maximum. ROIs 1, 2, and 3 were set in the cancellous bone in the exposed area, unexposed diseased area, and opposite healthy area, respectively, so that the pixel sizes were as large as possible. ROI 4 was set in the background. The ROI size ranged from 900 to 1200 pixels

The contrast-to-noise ratio (CNR) of the exposed diseased bone was calculated as follows:
$$ {\text{CNR}} = \left( {{\text{SI}}_{{{\text{ROI}}1}} - {\text{SI}}_{{{\text{ROI}}3}} } \right)/{\text{SD}}_{{{\text{ROI}}4}} $$

SIROI1 is the signal intensity of ROI in the exposed diseased bone marrow, SIROI3 is the signal intensity of ROI in the opposite healthy bone marrow, and SDROI4 is the noise of the background.

The CNR of the unexposed diseased bone was calculated as follows:
$$ {\text{CNR}} = \left( {{\text{SI}}_{{{\text{ROI}}2}} - {\text{SI}}_{{{\text{ROI}}3}} } \right)/{\text{SD}}_{{{\text{ROI}}4}} $$

SIROI2 is the signal intensity of ROI in the unexposed diseased bone marrow, and SIROI3 and SDROI4 are defined as above.

When the signal intensity of the diseased bone marrow was lower than that of the opposite healthy bone marrow, the CNR displayed a negative value. When the signal intensity of the diseased bone marrow was higher than that of the opposite healthy bone marrow, the CNR displayed a positive value.

MR imaging features were examined in terms of their relationship with the presence of exposed bone, types and administration routes of BP, and duration of symptoms.

Statistical analysis

The Mann–Whitney U test was used to evaluate differences in the CNR between the exposed and unexposed diseased bones. The Kruskal–Wallis H test was used to evaluate differences in CNR among the three groups by types and administration routes of BP. Spearman’s rank correlation coefficient was used to analyze the relationship between the CNR and duration of symptoms. A p value less than 0.05 was considered to indicate statistical significance.

Results

Review of the literature on MR imaging characteristics

Fifteen articles were identified [6, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23]. Table 2 shows the MR imaging features and the pathology of bone marrow. Although the diseased bone marrow showed low signal intensity on T1-weighted images, it showed various signal intensities according to the pathological states on T2-weighted and STIR images. The patterns of signal intensity of the bone marrow changed with the histologic findings. The areas with increased signal intensity on T2-weighted and STIR images were thought to histologically resemble a chronic osteomyelitis pattern [13]. The areas with decreased signal intensity on T2-weighted or STIR images were histologically consistent with necrosis.
Table 2

Review of the literature on the MR imaging features and pathology of bone marrow

 

MR imaging features

References

T1 WI

T2 WI/STIR

Gd-T1 WI

Bone marrow

 Sclerosis

Low

Low

 

[12, 13, 14, 15]

 Fibrosis

Low

Low

 

[13]

 Exposed bone

Low

Low

 

[10, 11, 16]

 Unexposed bone

Low

High

 

[10, 11]

 Inflammation

Low

High

 

[17]

 Edema

Low

High

 

[17]

 Osteolysis

Low

Mid-high

e(+)

[6, 18, 19, 20, 21]

 Ischemia

  

e(−)

[13]

 Necrosis

Low

Low

 

[6, 10, 22, 23]

Low

Low + high rim

e(−) + rim

[12, 16, 17]

 Sequestrum

Low

Low + high rim

e(−)

[10, 19, 22]

Soft tissue inflammation

Low

High

e(+)

[12, 16, 18, 19, 20, 21, 22, 23]

e(+), contrast enhancement; e(−), no enhancement

Marx [8] defined BRONJ as ischemic osteonecrosis of the jaws. A description of ischemia was also presented by Khosla et al. [13]. Regions of ischemia can be recognized as non-enhanced areas on contrast-enhanced T1-weighted images [13].

Necrotic bone transformation displayed low signal intensity on T1- and T2-weighted or STIR images [6, 10, 22, 23]. Increased signal intensity and enhancement were seen at the periphery of the necrotic bone on T2-weighted and contrast-enhanced T1-weighted images, respectively [12, 16, 17]. These results may have been due to the development of a reactive fibrotic margin surrounding the necrotic area and the inflammatory change in the soft tissue [12, 16, 17]. Sequestra displayed a low-signal-intensity center and a high-signal-intensity rim on T2-weighted MR images [10, 19, 22].

Bedogni et al. [11] discussed the difference in T2-signal intensity between exposed and unexposed diseased bones. The exposed areas showed a low signal on T1- and T2-weighted and STIR images, which would suggest a low water content and a histopathological correlation with paucity in cells and vessels (osteonecrotic pattern). On the other hand, the unexposed diseased bone was characterized by decreased signal intensity on T1-weighted images and increased signal intensity on T2-weighted and STIR images, which would suggest a high water content and inflammation associated with hypercellularity, osteogenesis, and hypervascularity (osteomyelitic pattern).

There are a few reports of MR imaging features according to differences in duration of symptoms [10, 16]. Especially in the early stage, there is little information on the typical imaging features. In patients with early and intermediate symptoms, the region of osteonecrosis displayed decreased signal intensity on T1-weighted images and normal signal intensity on T2-weighted images [16]. The region of the open wound demonstrated decreased signal intensity on T1-weighted images and intermediate or slightly increased signal intensity on T2-weighted images [16]. On the other hand, the signal intensity of the bone marrow on T2-weighted images in the late stages was variable. The exposed diseased bone demonstrated decreased signal intensity on T2-weighted or STIR images, and the unexposed diseased bone demonstrated increased signal intensity on T2-weighted or STIR images [10]. In clinically advanced cases, a mixed pattern was noted.

Evaluation of MR imaging features of our patients

MR imaging features of the present study are summarized in Table 3. A sequestrum and adjacent soft tissue involvement were each seen in eight (61.5 %) patients (Fig. 1).
Table 3

Summary of MR imaging features of our patients

Patient no.

Exposed bone

Sequestra

Adjacent soft tissue involvement

CNR of exposed bone

CNR of unexposed bone

On T1-weighted image

On STIR image

On T1-weighted image

On STIR image

1

+

+

+

−76.1

−7.5

−79.7

6.9

2

+

+

+

−123.2

−19.8

−98.3

84.7

3

  

−167.6

145.0

4

+

+

+

−205.9

−27.9

−182.1

52.9

5

+

+

−63.5

−3.9

−53.3

17.5

6

+

+

−65.4

−10.2

−36.0

19.1

7

+

  

−149.1

53.5

8

+

  

−100.0

98.0

9

+

+

  

−28.1

173.0

10

  

−44.1

15.5

11

+

+

+

−237.7

−69.2

−251.9

74.4

12

+

+

+

−358.0

−9.7

−326.0

51.5

13

  

−92.6

62.9

CNR and presence of exposed bone

The exposed diseased bone displayed low signal intensity on both T1-weighted and STIR images (Fig. 3). The unexposed diseased bone displayed low signal intensity on T1-weighted images and high signal intensity on STIR images (Fig. 3).
Fig. 3

A 76-year-old female (patient no. 2). This patient was treated for breast cancer with zoledronic acid by intravenous drip for 3 years. She underwent extraction of the right canine and first molar 5 months previously. She had complained of a swelling of the mental region for 2 months. She had exposed bone in the region of the right lateral incisor and canine. The exposed bone (white arrow) displayed low signal intensity both on T1-weighted (a) and STIR images (b). The CNR was −123.2 on T1-weighted images and −19.8 on STIR images. The unexposed bone in the right molar region (white arrowhead) displayed low signal intensity on T1-weighted images and high signal intensity on STIR images. The CNR was −98.3 and 84.7, respectively. The adjacent soft tissue showed swelling and increased signal intensity

Fig. 4

CNR of exposed and unexposed diseased bone

Figure 4 shows the CNR of the exposed and unexposed diseased bone marrow on T1-weighted and STIR images. The CNR of the exposed and unexposed diseased bone marrow displayed negative values on T1-weighted images. There was no significant difference in the CNR between the two groups (p = 0.2671, Mann–Whitney U test). On the other hand, the CNR of the exposed diseased bone displayed negative values, and that of the unexposed diseased bone displayed positive values on STIR images. There was a significant difference in the CNR between the two groups (p = 0.0004, Mann–Whitney U test).

CNR and types and administration routes of BP

Figure 5 shows the CNR of the three groups by types and administration routes of BP. The CNR of the exposed diseased bone displayed negative values on both T1-weighted and STIR images (Fig. 5a). There was no significant difference in the CNR of the exposed diseased bone among the three groups on both T1-weighted and STIR images (p = 0.1403 and p = 0.7382, respectively; Kruskal–Wallis H test). On the other hand, the CNR of the unexposed diseased bone displayed negative values on T1-weighted images and positive values on STIR images (Fig. 5b). There was no significant difference in the CNR of the unexposed diseased bone among the three groups on both T1-weighted and STIR images (p = 0.1864 and p = 0.9073, respectively; Kruskal–Wallis H test).
Fig. 5

CNR of the three groups according to type and administration route of BP. a Exposed diseased bone; b unexposed diseased bone

CNR and the period between the onset of maxillofacial symptoms and MR examination

Figure 6 shows the relationship between the CNR and duration of symptoms. The CNR of the exposed and unexposed diseased bone on T1-weighted and STIR images had no significant correlation with duration of symptoms (Table 4). Changes in the signal intensity of the bone marrow were seen with an early duration of symptoms. If the subjects were limited to patients with an early duration of less than 4 months, the CNR of the exposed and unexposed diseased bone on T1-weighted images had significant correlations with duration of symptoms (Table 4; Spearman’s rank correlation coefficient; rs = −0.9747, p = 0.0256 and rs = −0.6197, p = 0.0315, respectively).
Fig. 6

Relationship between CNR and duration of symptoms

Table 4

Relationship between CNR and duration of symptoms

 

rs

p value

All patients

 CNR of exposed bone on T1 WI

0.2703

0.5079

 CNR of exposed bone on STIR images

0.2523

0.5366

 CNR of unexposed bone on T1 WI

0.1492

0.6053

 CNR of unexposed bone on STIR images

−0.2486

0.3891

Patients with symptoms under 4 months

 CNR of exposed bone on T1 WI

−0.9747

0.0256*

 CNR of exposed bone on STIR images

−0.2052

0.3408

 CNR of unexposed bone on T1 WI

−0.6197

0.0315*

 CNR of unexposed bone on STIR images

0.2516

0.2252

p < 0.05, Spearman’s rank correlation coefficient (rs)

Discussion

The incidence of BRONJ is dependent on a number of factors, including the type of BP, route of administration, dose, duration of therapy, preexisting structural abnormalities of the jaws, and antecedent dental surgery or trauma [20].

Marx [8] was the first to describe avascular necrosis of the jaw associated with the use of intravenous administration of nitrogen-containing BPs, such as zoledronic acid. Most studies indicated that intravenous administration of nitrogen-containing BPs is associated with a higher risk of developing BRONJ than administration of BPs without nitrogen, such as pamidronate [12, 20, 25, 26, 27, 28]. If the risk of BRONJ differs according to the type or administration route of BP, differences in imaging features may be found. This was confirmed in the present study. However, there were no significant differences in signal intensity of the bone marrow among the three groups according to type and administration route of BP on both T1-weighted and STIR images. Further examination of a greater number of patients will be required.

The duration of BP therapy also seems to be involved in the multifactorial etiological process of BRONJ [21]. The incidence of BRONJ under pamidronate or zoledronic acid treatment was found to increase from 1.5 % after 1 year of treatment to 7.7 % after 3–4 years of treatment [29]. In the present study, the correlation between the duration of therapy and imaging features was not analyzed because all patients were medicated with BP for 2 years or more.

BP therapy interferes with bone repair mechanisms and may limit blood flow through its antiangiogenic property, which can potentiate minor injuries [30]. When the vascular supply of the jaw bones is compromised by BP, then minor injury or disease will be more likely to develop into a non-healing wound [9]. This may in turn progress to widespread necrosis and osteomyelitis. Whether these vessel abnormalities are related to inflammation or impaired angiogenesis and vascularization remains controversial [9]. Dental trauma and periodontal infection may be responsible for infection [20]. The reason that BP-induced disorders are seen in the jaw bones might depend on the unique environment of the oral cavity: only a thin layer of mucosa separates the jaw bone from the oral cavity. The roots of the teeth are separated from the underlying bone by a very thin periodontal ligament [30]. A position paper from the Allied Task Force Committee of five Japanese societies stated that widening of the periodontal ligament space, thickening of the lamina dura and cortical outlines, and incomplete healing of the extraction sockets were considered to be suspicious BRONJ signs [31]. In the present study, MR imaging of one patient with BRONJ displayed increased signal intensity of the periodontal ligament space (Fig. 1, white arrowhead), whereas other imaging findings could not be described owing to limitations of the MR imaging technique, such as metal artifacts or a large slice thickness.

MR imaging can depict changes in the bone marrow well. Bedogni et al. [11] described differences in T2-signal intensity between exposed and unexposed diseased bones of patients with BRONJ. The exposed diseased bone displayed decreased signal intensity on T1- and T2-weighted and STIR images, which suggests a low water content and a histopathological correlation with paucity in cells and vessels (osteonecrotic pattern). The unexposed diseased bone displayed increased signal intensity on T2-weighted and STIR images, which suggests a high water content and inflammation associated with hypercellularity, osteogenesis, and hypervascularity. This fits well the histopathological picture of a chronic osteomyelitic process, but does not apply to multinucleated osteoclast-like cells (osteomyelitic pattern). In our patients with BRONJ, these changes were confirmed. There was a significant difference in the CNR between the exposed and unexposed diseased bones on STIR images.

It is essential that professionals in the medical and dental fields can recognize subclinical signs of BRONJ early. Early diagnosis can ensure a better prognosis owing to early treatment and decreased necessity of surgery [19, 22]. MR imaging has crucial value in helping with early detection of bone lesions in patients taking BPs. BRONJ may remain as a slight symptomatic form for any number of weeks or months and is usually recognized exclusively owing to exposed bone in the oral cavity [9, 19]. Our series of patients were not asymptomatic. The initial symptoms corresponded to the typical presentation already described in the literature [19]: a painful “non-healing” extraction socket or exposed bone with progression to sequestrum formation associated with localized swelling. To examine the imaging features of the early stage of BRONJ, the progress of the disease in patients without symptoms should be observed prospectively. However, our study was retrospective; therefore, the subjects were patients who were medicated with BP and underwent MR examination regardless of whether they had exposed bone. In the present study, changes in the signal intensity of the bone marrow were seen in patients with early symptoms. The CNR in the early stage on T1-weighted images had a significant correlation with duration of symptoms.

In terms of the differential diagnosis in patients with BRONJ, metastatic lesions in the jaws are a major concern. Metastases occur four times more frequently in the mandible than in the maxilla. The bone destruction is similar to that caused by a primary tumor. The presence of necrotic lymph nodes may support the diagnosis of metastatic disease [16]. Osteomyelitis of the jaws is another important differential diagnosis [16]. The imaging findings of BRONJ may be essentially indistinguishable from those of osteomyelitis because both have considerable overlap in their pathophysiology [14]. An acute onset with a severe constitutional reaction suggests suppurative osteomyelitis; if this is not present, the differential diagnosis may be difficult [16]. Soft tissue involvement, such as edema and abnormal enhancement, is common in osteomyelitis, which is also seen in BRONJ [16].

In conclusion, we examined the MR imaging features of BRONJ, especially those in the early stage, through a review of the literature and analysis of our BRONJ patients. According to the literature, changes in the signal intensity of the bone marrow on T2-weighted images are variable: the exposed diseased bone displayed decreased signal intensity, and the unexposed diseased bone displayed increased signal intensity. In our patients, there was a significant difference in the CNR between the exposed and unexposed diseased bones on STIR images. There were no significant differences in the CNR among the three groups according to type and administration route of BP on both T1-weighted and STIR images. MR imaging could detect changes in the signal intensity of the bone marrow in patients with early symptoms. If the subjects were limited to patients in the early stage, the CNR on T1-weighted image had a significant correlation with the duration of symptoms. We believe that there is a need for prospective studies of patients to confirm these data.

Notes

Acknowledgments

We are thankful to all of the dentists in the Departments of Oral and Maxillofacial Radiology, Oral and Maxillofacial Surgery, Maxillofacial Surgery, and Oral Pathology for participating in the diagnosis and medical treatment of patients. We also thank all staff members in the MRI laboratory section of Hachiya Orthopedic Hospital for performing MR examinations of patients. In addition, we thank Prof. Tanimoto (Editor-in-Chief of the journal), Prof. Shimizutani (President of the 17th Congress of Clinical Imaging for Oral and Maxillofacial Lesions in Japan), and Prof. Taguchi (Coordinator of Symposium) for giving us the opportunity to present our work and contribute our findings to the medical field.

Conflict of interest

The authors declare no conflict of interest.

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Copyright information

© Japanese Society for Oral and Maxillofacial Radiology and Springer Japan 2013

Authors and Affiliations

  1. 1.Department of Oral and Maxillofacial RadiologyAichi-Gakuin University School of DentistryNagoyaJapan

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