Diabetes Insipidus as Initial Presentation of Rathke's Cleft Cyst

Correspondence To the Editor: A 56-year-old Chinese man was referred to Peking Union Medical College Hospital because of polydipsia (9000 ml/24 h) and polyuria (7000 ml/24 h) for over 20 days accompanied with intermittent moderate headache in frontal and temporal areas of both sides for about 2 weeks. The patient underwent a brain magnetic resonance imaging (MRI) with contrast in a local healthy facility, revealing that there was an irregular pituitary lesion measuring 1.1 cm × 1.4 cm × 2.2 cm. Apparently, the diagnosis of central diabetes insipidus (DI) was made, but the pituitary lesion remained to be elucidated. The patient received desmopressin acetate tablets (1.2 mg, q.n.) to ameliorate polydipsia (5000 ml/24 h) and polyuria (4000 ml/24 h). In our hospital, another brain MRI with enhancement was performed demonstrating a round cystic lesion in sellar region measuring 1.99 cm × 0.84 cm × 1.08 cm. The MRI signal feature was hypo-to iso-intense on T1-weighted images (T1WI) with rim enhancement and iso-to hyper-intense on T2-weighted images (T2WI) [Figure 1]. Moreover, hyperintense signal of pituitary posterior lobe on T1WI was not detected with consistence to the typical MRI signal of central DI. Endocrine evaluations demonstrated no pituitary hormone disorders. The ophthalmic test showed no visual disturbance. The past history of this patient was unremarkable. Taken together, the admission diagnoses of pituitary abscess and Rathke's cleft cyst (RCC) were carefully considered and discriminated before operation. The patient underwent an endoscopic endonasal transsphenoidal surgery. During the procedure, yellowish-white mucous content was seen and drained out. Moreover, white cystic wall was piecemeal resected. Cerebrospinal fluid leakage occurred unexpectedly, and sellar repair and reconstruction were subsequently conducted. In the postoperative period, intracranial infection happened but was controlled by parenteral antibiotics therapy. Desmopressin acetate therapy was then tapered to a maintenance dosage of 0.05 mg for every 8 h. The histopathological findings proved the sellar lesion to be RCC. RCC commonly remains an asymptomatic sellar entity. Patients with rare symptomatic RCC usually present with headache, visual disturbance, and partial hypopituitarism. [1] However, DI as the initial presentation of RCC is extremely rare. DI usually occurs following pituitary damage, such as trauma, abscess, and hypophysitis. In our case, the lack of hyperintense signal in pituitary posterior lobe on T1WI is observed indicative of the neurohypophyseal dysfunction, verifying central DI firmly. Previous researches demonstrate that pituitary MRI features of RCC are variable according to intracystic content. Rim enhancement …