History and Physical
A 9-year-old boy began drinking large amounts of water and urinating excessively for 3 months. This led to frequent interruptions at school and bedwetting at night. Over the past 3 weeks, his vision worsened and he had difficulty reading the school board from a distance. Medical history was unremarkable with no history of asphyxia, head trauma, surgery, encephalitis, tuberculosis, kidney disease, blood disease, visual impairment, deafness, or drug use. He was the third child of healthy, nonconsanguineous parents. The other two siblings, a 14-year-old girl and a 12-year-old boy, were both healthy.
Physical examination showed temperature 36.2°C, pulse 90, respiration rate 23/min, blood pressure 100/60, weight 22 kg (3%), and height 123 cm (5%). Head and neck examination was normal and assessments of respiratory, cardiovascular, gastrointestinal, and genitourinary systems were unremarkable. Bitemporal hemianopsia was detected on ophthalmologic examination.
Diagnostic Workup
Glucose and renal function tests were within normal limits. Urine volume was increased and a urine sample was lightly colored, with specific gravity between 1.001 and 1.005, and osmolality lower than plasma. Water restriction test and nasal 1-desamino-8-D-arginine vasopressin test confirmed central diabetes insipidus. Head CT showed a sellar and suprasellar mass with calcifications. Brain MRI showed an expansile cystic sellar and suprasellar mass replacing the pituitary gland and infundibulum. There was a mural nodule along the superior surface with uplifting and compression of the hypothalamus and optic chiasm ( Fig. 43.1 ).
Craniopharyngioma. (A) Noncontrast head CT shows an expansile hypodense sellar mass with surrounding bone remodeling. Brain MRI, (B) sagittal precontrast T1 demonstrates a lobulated sellar/suprasellar mass with uplifting of the optic chiasm ( arrow ). (C) Coronal T2 shows hyperintense cystic component with small superior solid nodule ( arrow ). (D) Postcontrast coronal T1 shows peripheral cyst wall and solid nodular enhancement ( arrows ).
Clinical Differential Diagnoses
Common endocrine presentations of hypothalamic and pituitary disorders are central (vasopressin deficient) diabetes insipidus, hypopituitarism, precocious puberty, delayed/early puberty, and amenorrhea.
In a patient with diabetes insipidus and bitemporal hemianopsia, consider masses of the sella and suprasellar region including tumors, inflammation, infection, and vascular lesions.
Imaging Differential Diagnoses
Pediatric sellar and suprasellar masses can include craniopharyngioma, optic-hypothalamic glioma, germ cell tumor, Langerhans cell histiocytosis, hypothalamic hamartoma, pituitary adenoma, Rathke cleft cyst, arachnoid cyst, inflammatory, and granulomatous disease.
Craniopharyngioma is a benign tumor originating from remnants of the Rathke pouch with admixed solid tissue, coarse calcifications, and complex cysts of varying size and composition. Tumor walls can be very adherent to surrounding brain parenchyma with associated vasogenic edema.
Optic pathway-hypothalamic gliomas are infiltrative tumors with T2-hyperintense signal, facilitated diffusion, and variable contrast enhancement.
Germ cell tumors are heterogeneous midline tumors that arise near the midline with heterogeneous solid-enhancing tissue and restricted diffusion, cystic/hemorrhagic changes, and calcifications. CSF dissemination is common.
Langerhans cell histiocytosis preferentially involves the infundibulum with a thickened appearance. Additional sites of osseous involvement may be present in the cranium, jaw, or skeleton with lytic and “beveled edge” appearance.
Hypothalamic hamartomas are sessile or pedunculated masses of ectopic gray matter with similar signal characteristics but more disorganized appearance ( Fig. 43.2 ).
