Pituitary Tumor: Endoscopic Procedure Revolutionizes Pituitary Surgery
One of the most extraordinary advances pioneered at the Skull Base Institute is the minimally invasive, fully endoscopic approach to treating pituitary tumors (pituitary adenomas) and other skull base disorders. This innovative procedure utilizes a tiny endoscope - 2.7 mm wide and 20 cm long - with angled tips that is inserted through the nostril and into the skull base. This approach offers numerous advantages in terms of the surgery and recovery period.
First, since the camera is "placed" at the tip of the endoscope, surgeons have a vivid panoramic view of the brain. They can look around corners and make a full visual assessment. This panoramic view also provides surgeons with the ability to remove the entire tumor in most cases. This process is in sharp contrast to the traditional approach, which requires viewing the tumor site through a microscope outside the skull at a focal distance that limits visibility.
Since the point of entry is through a nostril, no incision is required. Consequently, there is no scarring, no nasal packing, and the brain is undisturbed. The time required for the actual surgical procedure, the length of hospital stay and overall recovery time are dramatically reduced. Patients return home within 24-48 hours of surgery and enjoy a rapid overall recovery, and return to work and normal activities.
The Fully Endoscopic technique was simultaneously and independently pioneered at the Skull Base Institute and another major university medical center in Pittsburgh in 1996. Since then more than one thousand patients with pituitary tumors from all fifty states of our nation and international patients from countries such as Australia, Belgium, Canada, Egypt, France, Germany, Israel, Italy, Japan, Mexico, Poland, South Korea, Switzerland have sought surgical care at the Skull Base Institute.
Today, our research and development is focused on yet further innovating the field of Minimally Invasive Brain and Skull Base surgery in general and pituitary surgery in particular. High definition intraoperative digital imaging, 3D endoscopy, custom designed microinstruments, headsup displays and even nanotechnology are all being tapped in order to provide our patients with the most cutting edge and yet least invasive approaches to rid them of their tumors.
Overview
Most pituitary tumors are benign overgrowths (adenomas), while malignant overgrowths (pituitary carcinomas) are very rare. Pituitary tumors arise primarily from the anterior pituitary gland (adenohypophysis) whereas the posterior pituitary gland (neurohypohysis) rarely gives rise to tumors. The pituitary gland is multifunctional in nature and it secretes a variety of "key hormones" that regulate and control the activity of virtually all other glands of the human body. There are many different kinds of pituitary tumors.
Classically, pituitary tumors are divided into two groups: functional (secretory) and non-functional (non-secretory), the latter usually do not present until reaching a sufficient size to cause mass effect or compression on the surrounding neurovascular structures, mainly the optic nerves, whereas the former frequently present at an earlier stage with symptoms caused by the physiological effects of the excess hormones they secrete. This distinction is not always adhered to as "secretory" tumors may grow large enough to cause symptomatic mass effect and "non-secretory" tumors, can grow and destroy the normal pituitary gland leading to a decrease in the secretion of some or all of the pituitary hormones, a condition known as panhypopituitarism.
Pituitary tumors represent approximately 10% of all intracranial tumors. They are most common in the third and fourth decades of life, and equally affect both sexes. Approximately 70% of pituitary adenomas produce hormones (secretory) while 30% do not produce any hormones (non-secretory).
The key hormones secreted by the anterior pituitary gland are:
Growth hormone (GH) which, as the name indicates, regulates growth;
Adrenocorticotropic hormone (ACTH) which stimulates the adrenal glands to produce cortisol;
Thyroid-stimulating hormone (TSH), which stimulates and regulates the activity of the thyroid gland; also known as Thyrotropin;
Luteinizing hormone (LH) and follicle-stimulating hormone (FSH), the effect of these hormones depends on one's sex, in women they regulate ovulation, estrogen and progesterone production, and in men they regulate sperm formation and testosterone production;
Prolactin (PRL), during pregnancy this hormone helps prepare the breasts for future milk production and after birth it promotes the synthesis of milk; and
Melanocyte-Stimulating Hormone (MSH), which regulates the production of melanin, a dark pigment, by melanocytes in the skin.
The key hormones secreted by the posterior pituitary gland are:
Oxytocin, which stimulates contractions of the uterus during labor and the ejection of milk during breast-feeding; and
Antidiuretic hormone (ADH), which increases reabsorption of water into the blood by the kidneys and therefore decreases urine production; also known as Vasopressin.
Causes
Most pituitary tumors arise spontaneously and sporadically and are not genetically inherited. The events within the cell that lead to disordered pituitary cellular growth and/or hormonal over-secretion are not yet fully understood. Like most other tumors, the actual cause of pituitary tumors remains unknown.
Other causes such as aneurysms, tumors, chronic meningeal inflammation, or other lesions may irritate trigeminal nerve roots at the pons and cause symptoms of TN to occur, these can be identified and ruled out by MRI scan of the brain.
Symptoms
In general, pituitary tumors become symptomatic either due to an endocrinologic disturbance or due to mass effect on the surrounding neurovascular structures. Other symptoms are specific to the specific type of pituitary tumor, such as Cushing's disease, acromegaly, hyperprolactinemia, etc.
Symptoms of pituitary tumors vary depending on the size (microadenomas are smaller than one centimeter and macroadenomas are larger than one centimeter) and location of the tumor and whether the tumor affects the secretion of hormones by overproduction (hypersecretion) or under production (hyposecretion) of one or more of the pituitary hormones, and whether it exerts pressure on nearby neural or vascular structures (the optic nerves are particularly vulnerable due to their close proximity to the pituitary gland).
Some patients with large tumors may have acute hemorrhage into the tumor, a condition known as "pituitary apoplexy" which causes sudden onset of headache, visual loss, double vision, and/or pituitary failure. This condition is a medical emergency and immediate decompressive surgery is indicated.
Diagnosis
In addition to complete medical history, physical examination and hormonal studies; magnetic resonance imaging (MRI) is the investigation of choice to diagnose pituitary tumors as it is able to detect these tumors at a very early stage. Other investigations such as computed tomography (CT) may be helpful occasionally. Visual studies are important for evaluating any possible or existing visual field defects caused by large tumors that compress the optic pathways; bitemporal hemianopsia (loss of peripheral visual field) is the classic finding when a pituitary tumor compresses the optic chiasm.
Treatment
The three treatment options for symptomatic pituitary tumors are medical, surgical and radiotherapy (Gamma Knife (GK) or conventional radiotherapy). In some cases, such as in incomplete surgical removal these treatments may be combined. The goal of treatment, and the best measure for its success, is to reduce pressure on nearby structures (generally the optic nerves or the pituitary gland itself) and/or to normalize the levels of hormone production.
The goals of therapy are improved quality of life and survival, relief of mass effect and reversal of its associated signs and symptoms, normalization of hormonal hypersecretion, preservation or recovery of normal pituitary function, and prevention of recurrence.
Prognosis
Pituitary tumors are treatable and in many cases curable. The optimal treatment modality is determined by the type and size of the tumor, and how far it has grown into the surrounding brain at the time of diagnosis. Early detection of pituitary tumors is often "key" to successful treatment.
Future Prospects such as gene therapy, tissue-specific promoters and stem cell therapy may play a role in the future treatment of pituitary adenomas.
