Some patients affected by a pituitary condition may need surgery.
Why do I need an operation?
A pituitary tumour may affect your vision, your hormonal balance or other functions.
If your pituitary tumour has enlarged considerably, it may be pressing the optic nerves (to the eyes) which lie just above the pituitary gland. This can affect your eyesight, and may cause any of the following symptoms:
- It may reduce the amount that you can see overall so that particular areas in your field of vision are reduced. This usually affects the periphery (to the side) and makes it seem as if you are looking down a tunnel. It often affects one eye more than another. This is technically known as a bi-temporal hemianopia.
- It can affect vision by reducing your ability to see detail. This is called reduction in visual acuity. This will be discovered when you look at the reading chart that you will undoubtedly have seen in almost every doctor’s surgery and perhaps, too, in one of the endocrine clinics you have attended.
Large tumours can cause double vision, but very rarely.
A significant number of pituitary adenomas are discovered because they cause the over-production of one particular hormone. In contrast, another group of pituitary adenomas fail to produce one or more hormones.
The three most common types of over-producing adenomas are:
- Prolactin secreting tumours (prolactinomas), which produce the hormone prolactin.
- Cushing’s disease: this is caused by over-production of the hormone ACTH (Adrenocorticotrophic Hormone) which in turn releases Cortisol (the body’s natural glucocorticoid steroid hormone).
- Growth hormone-secreting adenomas: the excess secretion of growth hormone causes a condition called Acromegaly.
There are a couple of other hormone-producing tumours, but these are very much rarer.
The groups of pituitary adenomas which fail to produce one or more hormones are called non-functioning pituitary adenomas. This condition results in symptoms of hormone deficiency. They are often diagnosed late because they don’t produce specific symptoms of hormone excess.
A tumour can also be discovered when its increase in size has effects on functions other than vision. For example, occasionally (and again very rarely) tumours can be so large that they can cause blockage of the circulation of the fluid inside the brain, leading to a condition called hydrocephalus (water on the brain).
When pituitary tumours are very small, (less then 1cm) they are called microadenomas. Large tumours (over 1 cm) are called macroadenomas. Large tumours can also prevent normal hormone secretion by other parts of the pituitary gland causing symptoms of hormone deficiency. Sometimes they are more difficult to control.
Pituitary tumours are sometimes discovered when a patient has a scan for some other reason. This is happening more and more commonly as patients receive scans for other conditions. For example a CT scan or an MRI scan may be performed to investigate headaches, dizziness, hearing loss or other symptoms and this may lead to discovery of a pituitary tumour which is completely unrelated to these symptoms. Patients with incidentally discovered tumours require surgery only if the tumour has reached a certain size or if it is found to increase in size over time.
With all surgical procedures there are some associated risks and potential complications. The choice of surgeon is crucial to the likelihood of successful removal of the tumour, with experienced pituitary surgeons having the best results. The duration of hospital stay depends on the type of surgery.
Some units like to transfer their patients back to the referring endocrinologist fairly soon after the operation for more detailed tests. Other units discharge the patient home and refer the patient to the endocrinologist as an outpatient.
What will surgery achieve?
The aim of surgery is to remove as much of the tumour as safely as possible, without damage to the delicate nerves and blood vessels in the area. Surgery can, in some cases, remove all of very small tumours but complete removal of large tumours can be difficult and inaccessible areas of the tumour will be left in place. For many patients it is an essential part of their treatment to achieving restoration of hormone balance - there is more information on this subject later in this booklet.
What sort of surgery is undertaken?
Most operations on the pituitary gland are now carried out through the nose. This is called transsphenoidal surgery. ‘Trans’ means across and ‘sphenoid’ is the air cavity in which the pituitary gland sits, as you will see from our diagram at the beginning. Transsphenoidal surgery is traditionally performed using an operating microscope.
More recently technological advances have led to the use of fibre optic endoscopes in pituitary surgery. This is a newer technique and is called endoscopic pituitary surgery.
Operations through the skull (craniotomy) are far less common these days than they used to be. However, there are still situations where a craniotomy is required, for example, if parts of the tumour cannot be reached through the nose.