Luminal, Intramural Unicystic Ameloblastoma with Marked Fluid-Fluid Level: Validity of CT and MRI Findings.

We report herein a case of a luminal and intramural unicystic ameloblastoma (UA) with a marked fluid-fluid level. The validity of imaging findings in diagnosing UA in the present case is discussed in reference to the literature. The patient was a 50-year-old woman who presented with swelling of the gingiva in the region of the left mandibular third molar and numbness in the lower lip. Computed tomography (CT) and magnetic resonance imaging (MRI) revealed a large mass lesion with a unilocular appearance and a biphasic aspect, suggesting liquid content. Contrast-enhanced MRI (CE-MRI) and dynamic contrast-enhanced MRI (DCE-MRI) demonstrated that the biphasic aspect indicated a fluid-fluid level with no blood pooling/flow; it also revealed a thick rim-enhanced margin with mural protrusion. Postoperatively, the lesion was histopathologically diagnosed as a luminal and intramural UA. In conclusion, extensive imaging including both standard CT and MRI together with CE-MRI and DCE-MRI allowed mural protrusions or nodules on a thick cystic wall and liquid content to be correctly identified. This suggests that such imaging can play an important role in diagnosing a UA, even though the results were at first misleading due to the marked fluid-fluid level.

Atypical MRI and Histopathological Findings in Dermoid Cyst.

On images, a dermoid cyst is often described as resembling a "sack of marbles" or "marbles in a bag". Typically, it comprises an inhomogeneity filled with multiple nodules in a fluid matrix on both computed tomography and magnetic resonance imaging (MRI). How it appears, however, will vary depending on its histological contents, which may cause confusion in arriving at a diagnosis. This report describes a dermoid cyst in the floor of the mouth of a 55 year-old woman that showed an atypical internal appearance on MRI. Most of the lesion showed homogeneous high signal intensity on T1 - and T2-weighted images, suggesting that it was derived from fat. A small area within the mass, however, showed moderate signal intensity almost equal to that of muscle on T1-weighted images and high signal intensity on fat-suppressed T2-weighted images. Given the location of the lesion, a dermoid cyst was one possible diagnosis. A lipoma or lipoma variants were also considered, however, based on signal intensity. Histopathological section of the excised specimen revealed a dermoid cyst with sebaceous glands in its walls and keratin in its cavity. Dermoid cysts show variation in their internal structures and contents. Since MRI can reflect such histological variation, signal intensity requires careful interpretation.

Signal intensity on fluid-attenuated inversion recovery images of condylar marrow changes correspond with slight pain in patients with temporomandibular joint disorders.

OBJECTIVES: Edema and necrosis of the temporomandibular joint (TMJ) have been described in terms of bone marrow signal abnormalities in magnetic resonance imaging (MRI). However, painful joints often show no such signaling abnormalities, making the diagnosis of TMJ disorders difficult in the clinical setting. An association has been suggested between TMJ bone marrow change and TMJ pain, but even when such change results in slight pain, it may be too slight to be visually apparent on MR images. We hypothesized that fluid-attenuated inversion recovery (FLAIR) can be used to detect such minimal changes. The purpose of this study was to determine whether there is an association between signal intensity on FLAIR images and pain in the TMJ. METHODS: The study included 85 TMJs in 45 patients referred to our department for MRI. The signal intensity on FLAIR images was measured. Pain was evaluated based on the visual analog scale. An unpaired t test and Pearson's product-moment correlation coefficient were used for the statistical analysis. A p value of <0.05 was considered statistically significant. RESULTS: Signal intensity on the FLAIR images was significantly higher in painful than in nonpainful TMJs, although a significant correlation was not observed between the signal intensity and the pain score. CONCLUSIONS: The results of this study suggest an association between abnormalities in the marrow of the mandibular condyle and pain. They also indicate that FLAIR imaging is a useful tool in the clinical diagnosis of painful TMJs.

Incidental findings during head and neck MRI screening in 1717 patients with temporomandibular disorders.

OBJECTIVE: Magnetic resonance imaging (MRI) plays an important role in the evaluation of temporomandibular disorders (TMDs). At our institution, we perform additional head and neck screening using head coils when performing MRI screening of the temporomandibular joint (TMJ) to detect lesions in areas other than the TMJ (lesions discovered by chance, or incidental findings; IFs) and to conduct a diagnosis of exclusion. The objective of this study was to determine the number and frequency of IFs detected during head and neck screening, according to sites and diseases. MATERIALS AND METHODS: The study evaluated 1717 patients with clinically suspected TMDs who underwent MRI of the TMJ. IFs were assessed on horizontal sections of images of the craniofacial region obtained by the short tau inversion recovery imaging technique. RESULTS: The patients undergoing MRI of the TMJ comprised 433 males and 1284 females. Among the patients, at least one IF was detected on images in 461 patients. The most common IF site was the maxillary sinus. Based on diagnostic imaging, there were 21 IFs (1.2%) associated with TMD symptoms, or for which an association with TMD symptoms could not be ruled out. CONCLUSIONS: Combination of conventional MRI imaging of the TMJ with craniofacial MRI screening may allow detection of lesions other than TMDs, thereby confirming the usefulness of MRI. Detection of IFs may require development of different therapeutic strategies than those for TMDs.

Differences in signal intensities of temporomandibular joint (TMJ) effusion on fluid-attenuated inversion recovery (FLAIR) images.

OBJECTIVES: Joint effusion is demonstrated by high signal intensity in the upper and lower temporomandibular joint (TMJ) spaces on T2-weighted images. The fluid-attenuated inversion recovery (FLAIR) technique can be applied to analyze joint effusion in the TMJ. FLAIR signal intensity can be more sensitively influenced by the contents of joint effusion than T2-weighted signal intensity. The purpose of this study was to analyze the signal intensity of joint effusion on FLAIR images and to investigate the changes in joint effusion contents according to the status of TMJ disorders. METHODS: A total of 48 joints (45 patients) with joint effusion were investigated by magnetic resonance (MR) imaging. Regions of interest were placed over the joint effusion and gray matter on FLAIR images. The joints were categorized as normal disk position (NL), disk displacement with reduction (DWR), disk displacement without reduction (DWOR), and osteoarthritis (OA). The signal intensity ratio of joint effusion was calculated using gray matter as the reference point. The Kruskal-Wallis test and Steel test were applied. A probability of less than 0.05 was considered statistically significant. RESULTS: The median signal intensity ratios of joint effusion differed significantly among the four joint categories (p = 0.02, Kruskal-Wallis test). The median signal intensity ratio of joint effusion in the OA category was significantly higher than that in the NL category (p = 0.04, Steel test). CONCLUSIONS: The present findings suggest that FLAIR images can demonstrate the changes in joint effusion contents according to the status of TMJ disorders.

Analysis of elements in a minimal amount of temporomandibular joint fluid on fluid-attenuated inversion recovery magnetic resonance images.

OBJECTIVE: The aim of this study was to elucidate possible elements in minimal amounts of fluid (MF) in the temporomandibular joint by analyzing signal intensities in T2-weighted and fluid-attenuated inversion recovery (FLAIR) magnetic resonance (MR) images. STUDY DESIGN: Fifteen joints (15 patients) with MF were subjected to MR imaging to obtain T2-weighted and FLAIR images. Regions of interest were placed on MF, cerebrospinal fluid (CSF), and gray matter (GM), and their signal intensities were measured on both images. The signal intensity ratio (SIR) obtained by the signal intensity of GM between MF and CSF was compared in T2-weighted and FLAIR images. RESULTS: The average SIR of MF was lower than that of CSF on T2-weighted images, whereas it was higher on FLAIR images. The average suppression ratio of the signal intensity was lower for MF (24.1%) than for CSF (71.4%). CONCLUSIONS: MF may contain elements such as protein that are capable of inducing a shortened T1 relaxation time on MR images.

Potential of fluid-attenuated inversion recovery (FLAIR) in identification of temporomandibular joint effusion compared with T2-weighted images.

OBJECTIVE: The purpose of this study was to determine the potential of fluid-attenuated inversion recovery (FLAIR) sequence images in the identification of joint effusion (JE) compared with T2-weighted images. STUDY DESIGN: A total of 31 joints (28 patients) with JE were investigated by magnetic resonance imaging (MRI). Regions of interest were placed over JE, cerebrospinal fluid (CSF), and gray matter (GM) on T2-weighted and FLAIR images and their signal intensities compared. The signal intensity ratios (SIRs) of JE and CSF were calculated with GM as the reference point. The Pearson product-moment correlation coefficient was used for the statistical analysis. RESULTS: The SIR of JE showed a strong correlation between T2-weighted and FLAIR images. However, no correlation was observed for CSF. The average suppression ratio for JE was lower than that for CSF. CONCLUSIONS: MRI using FLAIR sequences revealed that JE was not just water content, but a fluid accumulation containing elements such as protein. Further studies are needed, and FLAIR sequences could be useful for the diagnosis of pain and symptoms of the temporomandibular joint (TMJ).

Image interpretation for squamous cell carcinoma of Stensen duct.

A case of squamous cell carcinoma presumed to have arisen from the right Stensen duct is reported. The patient, a 62-year-old man, was referred to our hospital with swelling in the right cheek. Magnetic resonance imaging (MRI), including contrast-enhanced MRI, and contrast-enhanced computerized tomography (CECT) enabled diagnosis of a solitary mass in the Stensen duct. Fat-suppressed T(2)-weighted imaging, in particular, demonstrated a mass-like lesion in the dilated Stensen duct and obstructive parotitis where the duct transitions into the parotid gland. Gadolinium-DTPA-enhanced T(1)-weighted imaging demonstrated the mass-like lesion surrounded by signal-hyperintense layer showing continuous transition from the thickened Stensen duct wall, which was also hyperintense. The CECT revealed peripheral annular enhancement surrounding the tumorous mass, with no enhancement of the duct wall itself, reflecting an increase in micro blood vessels in the stroma of the neoplasm. These image findings correlated well with subsequent histopathologic findings. A mass with rim enhancement and dilated Stensen duct accompanied by parotitis and no salivary calculus may suggest a differential diagnosis of malignant tumor of Stensen duct.