Pituitary adenomas represent approximately 10% of primary brain tumors and are the third most common intracranial tumor after gliomas and meningiomas. Most are benign and slow growing. Left untreated some will grow and cause neurological problems or hormonal abnormalities. Those tumors less than 1 cm in diameter are called microadenomas, while those over 1 cm in diameter are called macroadenomas. Endocrinologically active tumors include prolactin secreting adenomas known as prolactinomas, adrenocorticotropic hormone (ACTH) secreting adenomas causing Cushing’s disease, growth hormone (GH) secreting adenomas causing acromegaly, and the least common endocrinologically active adenoma, thyroid stimulating hormone (TSH) secreting adenomas causing hyperthyroidism. Adenomas that do not make excess hormones are called endocrinologically inactive.
Pituitary adenomas may cause problems because of hormonal hypersecretion, pituitary hormonal failure, vision loss, headaches and/or bleeding into the tumor (apoplexy).
• Hormonal hypersecretion: The three most common hormonally active adenomas are prolactinomas, GH-secreting tumors causing acromegaly, and ACTH-secreting tumors causing Cushing’s disease. Thyroid stimulating hormone (TSH) tumors are rare.
• Neurological problems: The most common neurological problems from a pituitary macroadenoma are loss of visual acuity and loss of peripheral vision termed a bitemporal hemianopsia. This visual loss results from pressure on the optic nerves and optic chiasm which is directly above the pituitary gland. Visual loss is usually seen only with larger macroadenomas (> 1 - 2 cms in size). Macroadenomas may on occasion also result in ocular palsies (double vision), but this is uncommon.
• Headache: Headaches may be seen in patients with macroadenomas and they are usually located in the frontal/ forehead and temporal area.
• Pituitary apoplexy: More rapid onset of symptoms is frequently seen when bleeding occurs within a pituitary tumor or the pituitary gland. Symptoms often include severe headache, a rapid change in vision or a change in mental status. Apoplexy is readily appreciated on MRI. The treatment for most patients with pituitary apoplexy is transsphenoidal surgery and hormonal replacement.
Transsphenoidal surgery is considered the first-line treatment for all pituitary adenomas except prolactinomas. The operation is performed through the nose endonasal without incisions on the face or head. The operating microscope combined with modern endoscopic techniques are utilized during surgery. During the past decades completely endoscopic endonasal surgery is possible. Complete tumor removal rates are generally high (80-90%) with smaller and non-invasive tumors, and lower with larger and/or invasive tumors (30-70%). Complications such as vision loss, bleeding, stroke, cerebrospinal fluid leak and meningitis are relatively rare when performed by experienced neurosurgeons. In rare cases (1%) a craniotomy (an incision on the scalp or eyebrow) is needed to adequately remove a tumor. Some tumors may also require long term hormonal treatment or radiation using conventional techniques or utilizing stereotactic radiosurgery such as the Gamma Knife.