Case description

A 35-year-old female with a 3-month history of amenorrhea was found to have prolactin levels elevated to 200 ng/mL. Imaging revealed a left-sided pituitary microadenoma ( Figure 3.15.1 ). She was started on cabergoline 0.25 mg twice a week, and her prolactin subsequently dropped to 140 ng/mL. Her cabergoline regimen was increased to three times weekly, but this dose did not result in normal prolactin levels. Imaging obtained a year later showed interval growth of the tumor along the left side of the sella turcica, contiguous with the wall of the left cavernous sinus. She was diagnosed with a medically resistant prolactinoma and was referred for surgical excision via a sublabial microscopic transsphenoidal approach. The sellar portion of the tumor was fully excised, although the lateral aspect was found to have likely dural invasion, and residual tumor was left within the left cavernous sinus ( Figure 3.15.2 ). Postoperatively, her prolactin levels dropped to 70.5 ng/mL but were still elevated, so she was referred for stereotactic radiosurgery (SRS) ( Figure 3.15.3 ).

Initial postcontrast T1-weighted image prior to transsphenoidal resection.

Postoperative postcontrast T1-weighted image after transsphenoidal resection.

Imaging of treatment plan.

Critical Structure	Dose Tolerance
Optic nerve/chiasm	10 Gy maximum point dose <0.2 cc >8 Gy
Brainstem	15 Gy maximum point dose <1 cc >10 Gy
Cranial nerves in cavernous sinus	Not fully defined but significantly more resistant than the anterior optic apparatus Can be more sensitive if SRS follows another type of radiation therapy
Cavernous carotid artery	Very tolerant Cases of asymptomatic carotid stenosis after SRS for pituitary adenomas have been reported
Normal pituitary gland and pituitary stalk	Recommend to limit radiation exposure to the identifiable gland to <11.0 Gy and to avoid whole-sella SRS whenever possible

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