RESUMEN
BACKGROUND: Primary central nervous system lymphoma (PCNSL) rarely originates in the hypothalamus. Hypothalamic PCNSL can present with various symptoms specific to dysfunction of the hypothalamus, including consciousness disturbance, cognitive impairment, hypopituitarism, and diabetes insipidus (DI). However, it remains unclear whether syndrome of inappropriate secretion of antidiuretic hormone (SIADH) can present as an initial sign of hypothalamic PCNSL. METHODS: Ninety-nine patients with PCNSL were diagnosed between January 2006 and December 2020 at our institutes. The initial symptoms and signs, hypothalamic-pituitary functions, serum sodium (Na) value, Karnofsky Performance Status (KPS) score on admission, and duration from onset to diagnosis were retrospectively investigated from the medical charts. RESULTS: Eight and 91 patients had hypothalamic PCNSL (hypothalamic group) and PCNSL located in other regions (control group), respectively. Patients' pathological diagnoses were diffuse large B-cell lymphoma (97 patients) and intravascular lymphoma (two patients). Six patients presented with hyponatremia derived from SIADH or suspected SIADH, and one presented with DI. Statistically significant differences between the hypothalamic and control groups were detected only in the preoperative serum Na values and KPS scores. CONCLUSION: SIADH can be an initial presentation of hypothalamic PCNSL. Early detection of hypothalamic PCNSL from SIADH may lead to proper management and improved prognosis.