Bridging the gap between molecular dynamics and hydrodynamics in nanoscale Brownian motions.

Through molecular dynamics simulations, we examined the hydrodynamic behavior of the Brownian motion of fullerene particles based on molecular interactions. The solvation free energy and velocity autocorrelation function (VACF) were calculated by using the Lennard-Jones (LJ) and Weeks-Chandler-Andersen (WCA) potentials for the solute-solvent and solvent-solvent interactions and by changing the size of the fullerene particles. We also measured the diffusion constant of the fullerene particles and the shear viscosity of the host fluid, and then the hydrodynamic radius aHD was quantified from the Stokes-Einstein relation. The aHD value exceeds that of the gyration radius of the fullerene when the solvation free energy exhibits largely negative values using the LJ potential. In contrast, aHD is similar to the size of bare fullerene when the solvation free energy is positive using the WCA potential. Furthermore, the VACF of the fullerene particles is directly comparable with the analytical expressions utilizing the Navier-Stokes equations both in incompressible and compressible forms. A hydrodynamic long-time tail t-3/2 is demonstrated for timescales longer than the kinematic time of the momentum diffusion over the particle size. However, the VACF at shorter timescales deviates from the hydrodynamic description, particularly for smaller fullerene particles and for the LJ potential. This occurs even though the compressible effect is considered when characterizing the decay of the VACF around the sound-propagation timescale over the particle size. These results indicate that the nanoscale Brownian motion is influenced by the solvation structure around the solute particles originating from the molecular interaction.

Pleomorphic adenoma of salivary glands: common and uncommon CT and MR imaging features.

Pleomorphic adenoma (PA) is the most common salivary gland tumor and is characterized by cytomorphological and architectural diversity. On CT and MR images, PAs are shown as well-defined lesions occasionally accompanied by characteristic lobulated contours. On T2-weighted images, typical PAs show marked hyperintensity, which reflects the abundant myxochondroid stroma, with a hypointense rim indicating the fibrous capsule. However, intratumoral signal intensity varies according to the cellular density, proportion of epithelial and stromal components, and type of stromal components. In addition, a variety of secondary histological changes, including fibrosis, lipometaplasia, ossification, cystic degeneration, and infarction, occur rarely in PAs; therefore, they are associated with difficulty in differential diagnosis from other salivary gland tumors. This review article describes the common and uncommon CT and MR imaging features of PA of the salivary glands.

CT and MR imaging characteristics of histological subtypes of head and neck ossifying fibroma.

OBJECTIVES: The current study aimed to assess CT and MRI characteristics of histological subtypes of head and neck ossifying fibroma (OF). METHODS: 12 patients with histopathologically-proven head and neck OF were included in this study. Lesions were pathologically classified into three histological subtypes: eight cement-OFs (COFs), three juvenile psammomatoid OFs (JPOFs), and one juvenile trabecular OF (JTOF). All patients underwent CT examination, while seven also underwent MRI. Imaging characteristics were retrospectively assessed. RESULTS: On CT images, the lesion margins were well-defined in nine patients (75%) (seven COFs and two JPOFs), partially ill-defined in two (17%) (one COF and one JTOF), and ill-defined in one (8%) (one JPOF). The continuity of the eroded overlying bone cortex was maintained in nine patients (75%) (seven COFs and two JPOFs) but disrupted in three (25%) (one COF, one JPOF, one JTOF). With respect to lesion density, homogeneous ground-glass opacity was observed in five patients (42%) (five COFs), target-like appearance in three (25%) (two COFs, one JPOF), and mixture of hyper- and hypodense areas were observed in four (33%) (one COF, two JPOFs, one JTOF). MR signal intensity was homogeneous in two patients (29%) (two COFs) and heterogeneous in five (71%) (two COFs, two JPOFs, one JTOF). CONCLUSIONS: COFs tended to exhibit well-defined margins and preserved continuity of the overlying bone cortex. COFs were usually homogeneous, whereas JPOFs and JTOF were always heterogeneous. Target-like appearance was one of the characteristics of OFs, but it was observed in both COF and JPOF.

Japanese standard for clinical stabilometry assessment: Current status and future directions.

Stabilometry is a useful tool for examining patients with functional disorders of the vestibular system. However, measurement techniques and devices vary by country. Therefore, international standardization of stabilometry is mandatory to validate the exchange of important findings. This was advocated at the 1983 Posturography Meeting in Kyoto but has not been adopted worldwide, and each country has continued to use unique regional measurement methods. In Japan, stabilometry has widespread application in medical practice in conjunction with research into its applications. With a goal of international standardization, we present details of stabilometry measurement methods and their application in Japan, together with a brief history and potential future directions of stabilometry.

Imaging Characteristics of Malignant Sinonasal Tumors.

Malignancies of the nasal cavity and paranasal sinuses account for 1% of all malignancies and 3% of malignancies of the upper aerodigestive tract. In the sinonasal tract, nearly half of all malignancies arise in the nasal cavity, whereas most of the remaining malignancies arise in the maxillary or ethmoid sinus. Squamous cell carcinoma is the most common histological subtype of malignant tumors occurring in this area, followed by other epithelial carcinomas, lymphomas, and malignant soft tissue tumors. Although many of these tumors present with nonspecific symptoms, each tumor exhibits characteristic imaging features. Although complex anatomy and various normal variants of the sinonasal tract cause difficulty in identifying the origin and extension of large sinonasal tumors, the invasion of vital structures such as the brain, optic nerves, and internal carotid artery affects patients' prognosis. Thus, diagnostic imaging plays a key role in predicting the histological subtype and in evaluating a tumor extension into adjacent structures. This article describes the computed tomography and magnetic resonance imaging findings for malignant sinonasal tumors.

Imaging findings of primary immunoglobulin G4-related cervical lymphadenopathy.

PURPOSE: The purpose of the present study was to assess imaging findings of primary immunoglobulin G4 (IgG4)-related cervical lymphadenopathy. METHODS: Five consecutive patients with clinically, serologically, and histopathologically confirmed primary IgG4-related cervical lymphadenopathy without any other organ involvement were included. All patients underwent contrast-enhanced computed tomography (CT), and four underwent 18F-fluorodeoxyglucose (FDG)-positron emission tomography (PET)/CT. We retrospectively reviewed the images and assessed the number, size, location, central necrosis, perinodal infiltration, penetrating vessels, and maximum standardized uptake values (SUVmax) of the enlarged cervical nodes. RESULTS: Thirteen enlarged cervical nodes measuring larger than 10 mm in minimum diameter were identified. The maximum and minimum diameter of enlarged nodes ranged from 1.2 to 3.2 cm (median, 1.8 cm) and from 1.0 to 1.9 cm (median, 1.2 cm), respectively. Lymphadenopathy was unilateral in all patients, and eight enlarged nodes were located at level IB (62%), one at level II (8%), three at level IV (23%), and one at level V (8%). Central necrosis was not seen in any nodes. Perinodal infiltration was seen in only one node (8%), and penetrating vessels were seen in seven nodes (54%). The median SUVmax of nine nodes was 4.45 (range, 2.08-12.44). CONCLUSION: Eight enlarged nodes (62%) were located in the submandibular region. Central necrosis was not observed in any nodes and perinodal infiltration was observed in one node (8%).

M2-like macrophage polarization in high lactic acid-producing head and neck cancer.

Reprogramming of glucose metabolism in tumor cells is referred to as the Warburg effect and results in increased lactic acid secretion into the tumor microenvironment. We have previously shown that lactic acid has important roles as a pro-inflammatory and immunosuppressive mediator and promotes tumor progression. In this study, we examined the relationship between the lactic acid concentration and expression of LDHA and GLUT1, which are related to the Warburg effect, in human head and neck squamous cell carcinoma (HNSCC). Tumors expressing lower levels of LDHA and GLUT1 had a higher concentration of lactic acid than those with higher LDHA and GLUT1 expression. Lactic acid also suppressed the expression of LDHA and GLUT1 in vitro. We previously reported that lactic acid enhances expression of an M2 macrophage marker, ARG1, in murine macrophages. Therefore, we investigated the relationship between the lactic acid concentration and polarization of M2 macrophages in HNSCC by measuring the expression of M2 macrophage markers, CSF1R and CD163, normalized using a pan-macrophage marker, CD68. Tumors with lower levels of CD68 showed a higher concentration of lactic acid, whereas those with higher levels of CSF1R showed a significantly higher concentration of lactic acid. A similar tendency was observed for CD163. These results suggest that tumor-secreted lactic acid is linked to the reduction of macrophages in tumors and promotes induction of M2-like macrophage polarization in human HNSCC.

Usefulness of diffusion-weighted MR imaging for differentiating between Warthin's tumor and oncocytoma of the parotid gland.

PURPOSE: To assess the efficacy of diffusion-weighted (DW) MR imaging for differentiating between Warthin's tumor and oncocytoma of the parotid gland. METHODS: Forty-five histopathologically confirmed parotid gland tumors (41 Warthin's tumors and 4 oncocytomas) were examined by MR imaging including DW imaging. 18F-fluorodeoxyglucose PET/CT was also performed in 9 Warthin's tumors and 3 oncocytomas. We retrospectively reviewed the images and compared the MR signal intensities, apparent diffusion coefficients (ADCs), and maximum standardized uptake values (SUVmax) of the solid components between the two pathologies. RESULTS: The signal intensity ratios (SIRs) on both T2-weighted images (0.92 ± 0.18 vs 0.65 ± 0.13, p < 0.01) and DW images (1.24 ± 0.42 vs 0.43 ± 0.16, p < 0.001) were higher in Warthin's tumors than in oncocytomas. ADCs (0.79 ± 0.11 vs 1.06 ± 0.06 × 10-3 mm2/s, p < 0.001) were lower in Warthin's tumors than in oncocytomas. No significant differences in the SIRs on T1-weighted images (1.09 ± 0.12 vs. 0.99 ± 0.07, p = 0.051) and SUVmax (8.22 ± 3.86 vs. 8.11 ± 1.33, p = 0.864) were found between Warthin's tumor and oncocytoma. CONCLUSION: DW imaging with ADC measurements is useful for the differentiation of Warthin's tumor from oncocytoma of the parotid gland.

[Eight Cases of Small Cell Neuroendocrine Carcinoma of the Head and Neck].

Small cell neuroendocrine carcinoma of the head and neck is a rarely occurring poorly differentiated and high-grade malignant neoplasm characterized by highly active proliferation of neuroendocrine tumor cells. There are no established therapies for this disease. To clarify the clinical course and develop effective treatment(s) for the carcinoma, we reviewed the data of 8 patients of small cell neuroendocrine carcinoma of the head and neck treated by us between 2006 and 2014 at the Department of Otolaryngology, Gifu University School of Medicine and our affiliated hospitals. The patients consisted of 3 men and 5 women, ranging in age from 38 to 84 years old (mean : 60.9 years). The tumor arose from the nasal cavity or the paranasal sinuses in 3 cases, from the parotid grand in 2 cases, from the oropharynx in 2 cases, and from the hypopharynx in 1 case. The tumor that arose from the hypopharynx was a combined small-cell carcinoma with squamous cell carcinomas, and the one that arose from the oropharynx had already metastasized to the brain. Most of the patients were treated by chemotherapy and radiotherapy based on the treatment employed for small cell carcinoma of the lung. Only the patient in whom the tumor arose from a paranasal sinus was treated by surgery despite the definitive diagnosis of small cell carcinoma. We selected CPT-11 and a platinum agent for 4 patients, and VP-16 and a platinum agent for 3 patients as the first-line chemotherapy. Although two patients showed carcinoma-free survival, one died of recurrence of the regional lymph node metastases and five died of distant metastases despite the absence of locoregional recurrence. The 5-year survival rate was a dismal 25%, suggesting that we need to establish effective treatment(s) for the control of distant metastases in cases of the small cell neuroendocrine carcinoma of the head and neck.

Effect of polaprezinc on oral mucositis, irradiation period, and time to discharge in patients with head and neck cancer.

BACKGROUND: The purpose of the present study was to determine whether polaprezinc suspension in sodium alginate (P-AG) reduces the irradiation period and time to discharge after completion of radiotherapy in patients with head and neck cancer. METHODS: The incidence and severity of oral mucositis, the irradiation period, and the time to discharge in patients who received radiotherapy with head and neck cancer were investigated retrospectively from the medical records. RESULTS: The incidence of grade 3 oral mucositis was significantly lower in the P-AG group than in the control group (16.5% vs 52.0%; p = .0003). P-AG also significantly reduced median duration of radiotherapy (hazard ratio [HR] = 0.557; 95% confidence interval [CI] = 0.357-0.871; p = .0149) and median time to discharge after completion of radiotherapy (HR = 0.604; 95% CI = 0.386-0.946; p = .028). CONCLUSION: P-AG reduced the irradiation period and the time to discharge after completion of radiotherapy by preventing oral mucositis in patients with head and neck cancer. © 2016 Wiley Periodicals, Inc. Head Neck 38: 1387-1392, 2016.

Differentiation of extranodal non-Hodgkins lymphoma from squamous cell carcinoma of the maxillary sinus: a multimodality imaging approach.

This study aimed to assess the efficacy of a multimodality imaging approach for differentiating between primary extranodal non-Hodgkin's lymphoma (NHL) and squamous cell carcinoma (SCC) of the maxillary sinus. Twelve NHLs and 29 SCCs of the maxillary sinus were included. CT findings, MR signal intensities, apparent diffusion coefficients (ADCs), and maximum standardized uptake values (SUVmax) were correlated with two pathologies. On CT, permeative growth frequency was greater among NHLs than among SCCs (50 % vs. 10 %; p < 0.01), whereas destructive growth frequency was greater among SCCs than among NHLs (83 % vs. 33 %; p < 0.01). On CT, remaining sinus wall within the tumor was more frequent with NHLs than with SCCs (92 % vs. 34 %; p < 0.01), whereas intratumoral necrosis was more frequent with SCCs than with NHLs (86 % vs. 17 %; p < 0.01). ADCs were lower for NHLs than for SCCs (0.61 vs. 0.95 × 10(-3) mm(2)/s; p < 0.01). No significant differences in MR signal intensities and SUVmax were observed. Tumor growth pattern, remaining sinus wall within the tumor, and intratumoral necrosis were useful CT findings for differentiating between NHLs and SCCs. ADC measurements could assist the differentiation of NHL from SCC.

Invasive epiglottic aspergillosis: A case report and literature review.

Invasive aspergillosis is a life-threatening infection in immunocompromised hosts and occurs most frequently in the lungs. Invasive laryngeal aspergillosis is extremely rare. Due to the potential progression of invasive aspergillosis, antifungal therapy must be started immediately in cases involving clinical suspicion of the disease. A 65-year-old male with agranulocytosis complained of sore throat and dysphagia. His epiglottis was covered with caseating granulomatous lesions and the tissue was easily disrupted. A histopathological examination showed an aggressive invasion of Aspergillus species and cartilage destruction. Therefore, we made a diagnosis of primary invasive epiglottic aspergillosis. The invasive aspergillosis resolved with antifungal therapy and an increase in neutrophils. It is therefore necessary to include invasive laryngeal aspergillosis in the differential diagnosis when encountering immunocompromised patients presenting with laryngeal granulomatous lesions and laryngitis-like symptoms.

Perfusion imaging of parotid gland tumours: usefulness of arterial spin labeling for differentiating Warthin's tumours.

OBJECTIVE: To assess prospectively the efficacy of arterial spin labelling (ASL) against conventional and diffusion-weighted (DW) MR imaging for differentiating parotid gland tumours. METHODS: We included 10 pleomorphic adenomas, 12 Warthin's tumours, and nine malignant tumours of the parotid glands. Only tumours larger than 10 mm were included in this study. All parotid gland tumours underwent T1-weighted, T2-weighted, DW, and ASL imaging. Tumour-to-parotid gland signal intensity ratios (SIRs) and apparent diffusion coefficients (ADCs) of solid components were correlated with these pathologies. RESULTS: SIRs on T2-weighted images and ADCs were higher in pleomorphic adenomas than in Warthin's tumours (p < .01) and malignant tumours (p < .01). SIRs on ASL were higher in Warthin's tumours than in pleomorphic adenomas (p < .01) and malignant tumours (p < .05). Az value of SIRs on ASL for differentiating Warthin's tumours from the other pathologies was 0.982. The sensitivity, specificity, and accuracy of SIRs on ASL for the diagnosis of Warthin's tumours at an optimal SIR threshold of over 8.70 were 91.7%, 94.7%, and 93.5%, respectively. CONCLUSIONS: ASL with SIR measurements could non-invasively evaluate tumour blood flow of parotid gland tumours and differentiate Warthin's tumours from pleomorphic adenomas and malignant tumours. KEY POINTS: • ASL non-invasively evaluates tumour blood flow of parotid gland tumours • ASL differentiates Warthin's tumours from pleomorphic adenomas and malignant tumours • ASL cannot differentiate between pleomorphic adenomas and malignant tumours.

Treatment for Progressive Hearing Loss Due to Paget's Disease of Bone - A Case Report and Literature Review.

Paget's disease is a common bone remodeling disorder that typically begins with excessive bone resorption in the elderly. Bilateral progressive hearing loss is the most frequently encountered complication of Paget's disease. The types of hearing loss identified by audiometry are conductive, sensorineural, or both. However, the precise mechanism of hearing loss remains unclear, and the treatment has been controversial. We present a 73-year-old man who suffered from bilateral progressive hearing loss due to Paget's disease. Potent bisphosphonates, oral risedronate in daily adjusted dosages for 6 months, did not decrease or suppress the worsening of the hearing loss. The Nucleus CI24 Contour electrode array was successfully inserted on the left side without surgical and postoperative complications. The Japanese open set monosyllable word recognition test in a sound field at 65 dB had a result of 74%. This cochlear implantation can be an indication for cases of profound hearing loss due to Paget's disease.

Pharmacotherapy for adverse events reduces the length of hospital stay in patients admitted to otolaryngology ward: a single arm intervention study.

BACKGROUND: To determine whether adverse events extend the duration of hospitalization, and to evaluate the effectiveness of medical intervention in ameliorating adverse events and reducing the prolonged hospital stay associated with adverse events. METHODS: A single arm intervention study was conducted from October 2012 to March 2014 in the otolaryngology ward of a 614-bed, university-affiliated hospital. Adverse events were monitored daily by physicians, pharmacists and nurses, and recorded in the electronic medical chart for each patient. Appropriate drug management of adverse events was performed by physicians in liaison with pharmacists. The Kaplan-Meier method was used to assess the length of hospitalization of patients who underwent medical intervention for adverse events. RESULTS: Of 571 patients admitted to the otolaryngology ward in a year, 219 patients (38.4%) experienced adverse events of grade ≥2. The duration of hospitalization was affected by the grade of adverse events, with a mean duration of hospital stay of 9.2, 17.2, 28.3 and 47.0 days for grades 0, 1, 2, and 3-4, respectively. Medical intervention lowered the incidence of grade ≥2 adverse events to 14.5%. The length of hospitalization was significantly shorter in patients who showed an improvement of adverse events after medical intervention than those who did not (26.4 days vs. 41.6 days, hazard ratio 1.687, 95% confidence interval: 1.260-2.259, P<0.001). A multivariate Cox proportional hazard analysis indicated that insomnia, constipation, nausea/vomiting, infection, non-cancer pain, oral mucositis, odynophagia and neutropenia were significant risk factors for prolongation of hospital stay. CONCLUSION: Patients who experienced adverse events are at high risk of prolonged hospitalization. Medical intervention for adverse events was found to be effective in reducing the length of hospital stay associated with adverse events.

Salivary gland tumors of the parotid gland: CT and MR imaging findings with emphasis on intratumoral cystic components.

INTRODUCTION: The purpose of this study was to assess computed tomography (CT) and magnetic resonance (MR) imaging findings of salivary gland tumors of the parotid gland with emphasis on intratumoral cystic components. METHODS: Seventy-two histopathologically confirmed salivary gland tumors of the parotid gland (44 benign and 28 malignant), which underwent both CT and MR imaging including contrast-enhanced study, were included in this study. We retrospectively reviewed images for the presence, number, occupying rate, margin characteristics, distribution, and predominant MR signal intensity of intratumoral cystic components. RESULTS: The prevalence of cystic components was greater in malignant than benign tumors (79 vs. 50%, p < 0.05). The number and occupying rate were similar between benign and malignant tumors. The irregular margins were more frequent in malignant than benign tumors (73 vs. 27%, p < 0.01). The frequency of eccentric location was greater in benign than malignant tumors (91 vs. 55%, p < 0.01), whereas the frequency of centric location was greater in malignant than benign tumors (32 vs. 0%, p < 0.01). On T1-weighted images, the frequency of hyperintensity was greater in benign than malignant tumors (50 vs. 9%, p < 0.01), whereas that of isointensity was greater in malignant than benign tumors (50 vs. 0%, p < 0.01). Multiple logistic regression analysis showed that the absence of irregular margins of cystic components only was significantly correlated with the presence of benign salivary gland tumors (p < 0.01). CONCLUSION: Imaging features of intratumoral cystic components may help to differentiate benign from malignant tumors of the parotid salivary gland.

A characteristic pattern in the postural sway of unilateral vestibular impaired patients.

The statistical properties of the center of pressure (COP) change over time, and -invariant methods of the COP analysis is not sufficient to monitor the changes. Therefore, dynamic temporal information of the COP signals has been important in assessing the postural stability. The purpose of this study was to evaluate the characteristic pattern of time-frequency dynamics during the upright stance in patients with unilateral vestibular dysfunction (UVD). This study included 20 dizzy patients with UVD and age-matched 20 control subjects without any vestibular disorder. The COP signals were collected using a single standard force platform and a spectral analysis including the time-frequency dynamics was carried out on the basis of the maximum entropy method (MEM) by using a segment time series analysis. The power spectral density (PSD) analysis exhibited an exponential decreasing shape (1/f (-)(ß)) when plotted on a double logarithmic scale. The average value of ß in the low frequency range of less than 1 Hz in the UVD group was significantly lower than that in the control group (p < 0.05) in the medial-lateral (ML) direction under eyes closed condition. In the segment time series analysis, the peak frequency of the COP signals in the patients with UVD gradually converged to the frequency range of 0.1-0.2 Hz in the ML direction under EC condition. Our results suggest that the segment time series analysis of the COP signals can derive a characteristic pattern related to the UVD. It may indicate an increased reflexivity of the COP fluctuation by the UVD, resulting in inducing the instability.

Metastatic retropharyngeal lymph nodes: comparison of CT and MR imaging for diagnostic accuracy.

PURPOSE: The purpose of this study was to compare the diagnostic accuracies of CT and MR imaging for the detection of metastatic retropharyngeal lymph nodes (RLNs) in patients with nasopharyngeal and oropharyngeal squamous cell carcinoma (SCC). MATERIALS AND METHODS: The study included 38 patients (28 men and 10 women; mean age, 65 years; age range, 48-82 years) with nasopharyngeal (n=15) and oropharyngeal (n=23) SCC who underwent both contrast-enhanced CT and MR imaging before chemoradiotherapy. RLNs were classified as malignant or benign on the basis of the results of follow-up MR imaging. Two radiologists independently evaluated the images for diagnosing metastatic RLNs. RESULTS: Among a total of 68 RLNs (minimum diameter, ≥ 4 mm) that were detected on gadolinium-enhanced fat-suppressed T1-weighted images, 30 (44%) were malignant and 38 (56%) were benign. The sensitivities of CT versus MRI were 60% versus 97% for observer 1 (p<0.01) and 37% versus 90% for observer 2 (p<0.01). The specificities of CT versus MRI were 92% versus 97% for observer 1 (p=0.50) and 92% versus 100% for observer 2 (p=0.25). The areas under the receiver operating characteristic curve (AUC) for CT versus MRI were 0.788 versus 0.996 for observer 1 (p<0.01) and 0.693 versus 0.961 for observer 2 (p<0.01). CONCLUSION: MR imaging was superior to CT for the detection of metastatic RLNs.

CT and MR imaging findings of palatal tumors.

Palatal tumors commonly arise from the minor salivary glands, and benign tumors account for approximately half of all minor salivary gland tumors. Minor salivary gland tumors have an affinity for the posterior hard palate and soft palate and virtually never arise in the midline, probably because of the distribution of palatal salivary glands. The majority of benign salivary gland tumors of the palate are pleomorphic adenomas, while the most common malignant salivary gland tumor is adenoid cystic carcinoma, followed by mucoepidermoid carcinoma, adenocarcinoma, and polymorphous low-grade adenocarcinoma. Epithelial tumors frequently arise from the soft palate. The majority of benign epithelial tumors of the palate are papillomas, while most malignant epithelial tumors are squamous cell carcinomas. Various types of mesenchymal tumors, including fibromas, lipomas, schwannomas, neurofibromas, hemangiomas, and lymphangiomas, also involve the palate. This article describes the CT and MR findings of benign and malignant palatal tumors.

[A case of idiopathic neck bleeding from a parathyroid cyst].

Bleeding from parathyroid cysts is rare. The retropharyngeal space has a very soft structure and if bleeding spreads to this space, airway obstruction can easily occur. We report on a 50-year-old female case with idiopathic neck bleeding from a left parathyroid cyst without any episode of injury. The patient complained of neck swelling after exercise and went to a nearby hospital. At the hospital, the doctor thought this swelling was caused by retropharyngeal bleeding from a tumor behind the left thyroid gland. Embolization of the left thyroid artery was performed. However, the next day, airway obstruction.was occurred and she was brought to our hospital. An emergency operation was performed to open the left neck swelling region. The operation findings and pathological examination showed that the bleeding was caused by a parathyroid cyst and airway obstruction had occurred because of retropharyngeal edema. In this case, the bleeding may have been caused by torsion of the neck when the patient exercised. The retropharyngeal edema probably resulted from the delay of delivery of the lymphatic and venous return and the arterial embolization. 1 year after the operation, the patient is very well and there has been no recurrence.