The major pathophysiology of eosinophilic chronic rhinosinusitis (ECRS) is thought to be type 2 inflammation by the innate and acquired immune responses of the sinonasal mucosae to external stimuli, centered on type 2 cytokines (IL-4, 5, and 13). Formation of albumin-based edema due to vascular hyperpermeability and excessive fibrin deposition due to hypercoagulation and fibrinolytic system suppression are thought to play the important roles on the causes of nasal polyps in the remodeling of the sinonasal mucosae. A definitive diagnosis of ECRS based on diagnostic criteria corresponds to the intractable disease designated by the Ministry of Health, Labor and Welfare. The accompanying eosinophilic otitis media, bronchial asthma, and systemic overlap type 2 inflammatory diseases should be also considered. The goal of ECRS treatment is to improve and stably maintain respiratory and olfactory function. For cost-effectiveness, management with an appropriate combination of pharmacotherapy that suppress type 2 cytokines, such as corticosteroids and biotics, and surgical therapy (full house of endoscopic sinus surgery) is critical.

　Although high-frequency hearing loss, as typified by age-related hearing loss, accounts for a large percentage of cases of hearing disorders, high-frequency hearing loss does not cause much inconvenience in conversation. Therefore, tinnitus as a symptom of hearing loss is the most common complaint of patients with high-frequency sensorineural hearing loss when they visit an otorhinolaryngologist, as their hearing is close to normal in the low to mid frequency range. Cisplatin, an anticancer drug used in the treatment of many malignancies, is well-known as a cause of sensorineural hearing loss of the high-frequency type. Although the incidence of sensorineural hearing loss increases when the cumulative dose of cisplatin exceeds 300 mg/m², hearing impairment can occur even with smaller cumulative doses of cisplatin. In this study, we report the case of a patient who developed tinnitus during adjuvant chemotherapy after lung cancer surgery, at a relatively small cumulative dose (160 mg/m²). Pure-tone audiometry showed high-frequency sensorineural hearing loss, and assessment of distortion product otoacoustic emission (DPOAE) showed a decrease in the distortion product level at high frequencies, suggesting the diagnosis of tinnitus associated with cochlear damage caused by cisplatin treatment. The high-frequency distortion-type sensorineural hearing loss progressed with increasing cumulative dose of cisplatin. Both the distortion product level and signal-to-noise ratio of distorted component otoacoustic emissions, which was used to evaluate cochlear damage, were decreased, and the tinnitus handicap inventory (THI) score, which reflects the severity of the subjective symptom of tinnitus, worsened. It is thought that it would be useful to perform not only pure tone audiometry, but also a combination of various other tests including measurement of distortion component otoacoustic emissions and assessment by the tinnitus handicap inventory for a thorough auditory evaluation in patients receiving treatment with cisplatin.

　Recurrent infection of a frontal mucocele can lead to frontal osteomyelitis and subperiosteal abscess formation in the orbit, resulting in orbital complications. We report a case of frontal mucocele complicated by formation of a subcutaneous abscess in the upper eyelid that ruptured through the overlying skin. A 51-year-old man visited us complaining of right upper eyelid swelling and tenderness. On examination, we found a subcutaneous abscess of the upper eyelid that had ruptured through the overlying skin. Computed tomography (CT) and magnetic resonance imaging (MRI) revealed a right frontal mucocele and inflammation of the supraorbital margin. Therefore, we made the final diagnosis of frontal mucocele complicated by formation of a right upper eyelid abscess rupturing through the overlying skin. Endoscopic sinus surgery was performed to open the maxillary sinus and frontal mucocele into the nasal cavity. Then, we performed craniotomy, resected the frontal mucocele, and cranialized the frontal sinus by inserting a frontal musculoskeletal flap into the floor of the frontal sinus. The anterior skull base was covered with a pedicled septal mucosal flap. The upper wall of the right orbit was reconstructed by a bone graft taken from the skull. The postoperative course of the patient was satisfactory. At present, 6 months since the surgery, the patient can open his right eye normally. Upper eyelid lesions complicating a frontal mucocele should be managed by collaboration between the departments of otolaryngology and other relevant departments.

　Liposarcoma is common among soft-tissue sarcomas, but rarely occurs in the head and neck region. We report a case in which a tumor arising in the retropharyngeal space, which is rare among head and neck tumors, was diagnosed as a liposarcoma.

　The patient was a 51-year-old woman who was suspected as having a cervical lipoma based on the findings of an imaging examination performed to evaluate the cause of her presenting symptom, namely, discomfort in the pharynx. She was followed up for a while, but as the tumor grew, she developed cervical swelling and dyspnea at night. Polysomnography led to the diagnosis of sleep apnea, and we performed retropharyngeal space tumor resection for the purpose of definitive diagnosis of the tumor and for providing relief from the severe sleep apnea. Gross examination of the resected specimen revealed a lipoma-like soft-tissue sarcoma with a deep white induration, and histopathological examination revealed well-differentiated liposarcoma. After surgery, the sleep apnea improved. The postoperative course was uneventful and the patient has shown no signs of recurrence. It is difficult to distinguish between lipoma and liposarcoma based on the imaging findings alone. Especially in the head and neck region, the anatomical features may make it difficult to select the most appropriate treatment method due to the large invasiveness of extended resection. When symptoms such as tumor growth or sleep apnea occur, as in this case, it is desirable to consider surgery, regardless of the preoperative diagnosis, and it is also necessary to remain vigilant in cases where the “wait-and-watch” policy is adopted without surgery.

　The differential diagnosis of lateral cervical cystic disease is wide, including lateral cervical cyst, ranula, lymphangioma, cutaneous cyst, lymphadenopathy, etc, and medical examinations and tests must be carried out bearing these diagnoses in mind before surgery. We encountered the case of a patient who was suspected preoperatively as having a lateral cervical cyst, but was diagnosed after surgery as having a parathyroid cyst. Parathyroid cyst is a relatively rare disease and could be functioning or non-functioning. Functioning parathyroid cysts cause hyperparathyroidism, associated with high plasma levels of parathormone (PTH) and calcium (Ca). Non-functioning parathyroid cyst is associated with normal parathyroid function and normal serum PTH and Ca levels. In this patient, we diagnosed a non-functioning parathyroid cyst based on the findings of blood and histopathological examinations. Some lateral cervical cystic diseases such as lymph node metastasis and symptomatic functioning parathyroid cyst need early diagnosis and treatment, but it is sometimes difficult to diagnose lateral cervical cystic disease only from cytologic and imaging examinations. The purpose of this report is to call attention to the need for inclusion of parathyroid cyst in the differential diagnoses of lateral cervical cysts, and suggest avoid missing malignant or fatal disease. We believe that histopathological examination should be prioritized if preoperative diagnosis is difficult.

　Boron neutron capture therapy (BNCT) for locally recurrent and locally advanced head and neck cancer using the boron agent, borofalan (¹⁰B) and the accelerator-based BNCT treatment system began with the public insurance coverage in June 2020. This therapy is based on the transmutation reaction of boron-10 and neutrons, and enables tumor-selective treatment based on the accumulation of boron agents. However, since the neutrons used in BNCT do not reach deep into the body, it may be difficult to provide effective treatment to patients with deep-seated tumors. Therefore, it is desirable to use this treatment method as early as possible as a treatment option for patients who are found to have local recurrence.