Snowman Sign in Pituitary Macroadenoma
Yuwei Zhou, Wei Weng
N Engl J Med 2025;393:699
DOI: 10.1056/NEJMicm2503820
A previously healthy 47-year-old woman presented to the neurology clinic with a 1-month history of worsening headaches associated with blurry vision, galactorrhea, and irregular menstrual cycles. Physical examination was notable for reduced visual acuity of 20/50 in both eyes, with normal visual fields and extraocular movements. Magnetic resonance imaging (MRI) of the head showed an enlarged pituitary gland protruding from the sella turcica (a depression at the base of the skull that houses the pituitary gland) into the suprasellar cistern, which was compressing the optic chiasm and causing the “snowman sign” (Panel A). Intrapituitary hemorrhage was also seen (Panel B, asterisks). The snowman sign occurs when a slow-growing tumor that originates in the sella turcica gets indented by the roof of the sella in its upward growth. Laboratory testing revealed a serum prolactin level of more than 200 mg per milliliter (reference range, 3.3 to 26.7), as well as central adrenal insufficiency and central hypothyroidism. A diagnosis of a prolactin-secreting pituitary macroadenoma with subclinical pituitary apoplexy was made. Transsphenoidal surgical resection was performed. The symptoms resolved on postoperative day 3, and levels of pituitary hormones normalized 1 month later. A repeat MRI at 1-year follow-up showed residual pituitary tissue in the sella turcica and no other abnormalities.
