Which pituitary adenomas can be treated surgically? Are the risks of surgery high?

Author: Yu Shuqing, Chief Physician, Beijing Tiantan Hospital, Capital Medical University

Reviewer: Li Jingjing, Chief Physician, Beijing Tiantan Hospital, Capital Medical University

The pituitary gland is located in the sellar region in the middle of the brain. There are many tumors that occur in the sellar region, including pituitary adenomas, craniopharyngiomas, meningiomas, etc., so they must be distinguished in diagnosis. Clinically, by testing various hormone levels and imaging examinations, such as CT and MRI, combined with clinical manifestations, it can be confirmed that it is a pituitary adenoma.

There are three main types of treatments for pituitary adenomas: surgery, medication, and gamma knife. In terms of classification, if it is a growth hormone-producing pituitary adenoma, surgery is the first choice, which can achieve the purpose of cure. If drug treatment for prolactinoma is ineffective or the effect is not obvious, surgical treatment is also required. There are two main surgical methods, one is transnasal sphenoidal approach surgery, and the other is craniotomy, called transfrontal approach surgery.

Today I will mainly introduce the surgical treatment of pituitary adenomas.

1. How is transnasal sphenoidal approach surgery for pituitary adenoma performed? Are there any risks?

The pituitary gland grows in the sella turcica, just behind the nostrils. If the tumor is relatively small, transnasal surgery, which is a minimally invasive transnasal sphenoidal approach, can be chosen. Transnasal sphenoidal approach surgery, from an anatomical point of view, goes directly to the bottom of the sella turcica, with relatively little trauma. This procedure is currently a development trend.

After opening the nostrils, separate the nasal mucosa and insert the nasal endoscope into the sphenoid sinus. The sphenoid sinus is a cavity. After passing through the sphenoid sinus, you can directly reach the sella turcica. The sella turcica is a bony structure. Use instruments to open the sella turcica to see the dura mater of the sella turcica. Cut the dura mater to see the pituitary gland. Now there is a more advanced device called an endoscope. The endoscope goes directly through the nostrils to the sella turcica. After opening, the operation is performed under the endoscope, which is simpler and more convenient.

The most common complication of transnasal sphenoidal approach surgery is cerebrospinal fluid rhinorrhea. Because the dura mater must be cut open artificially during surgery, the arachnoid membrane may rupture after cutting, and cerebrospinal fluid will flow out of the nasal cavity. Because the cranial cavity is sterile, but the nasal passage is not sterile, reverse infection through the nasal passage can lead to meningitis, which is a very serious complication. If cerebrospinal fluid rhinorrhea occurs after surgery, it is generally necessary to lie flat for a few days, perform lumbar puncture and drainage, drain the cerebrospinal fluid, keep the leaking area dry, and promote healing. If it still doesn't work, a second surgery will be required to repair it.

Another common complication is diabetes insipidus. The pituitary stalk is an important structure connecting the hypothalamus and pituitary gland. If the pituitary stalk is pulled during surgery, it will be damaged, which will lead to severe neuro-endocrine dysfunction and diabetes insipidus. Diabetes insipidus can be controlled with a drug called vasopressin tablets. After the function of the pituitary stalk is gradually restored, the drug can be stopped.

Figure 1 Original copyright image, no permission to reprint

2. How is craniotomy for pituitary adenoma performed? Are there any risks?

If the pituitary adenoma is relatively large and grows above or beside the sella turcica, a craniotomy is required.

First, a bone flap is made in the forehead, the dura mater is cut to expose the brain tissue, and the lateral fissure is opened to release fluid. After the fluid is released, the brain tissue collapses, and the pituitary gland is buried just below the frontal lobe. The frontal lobe must be lifted to see the tumor. There are nerves and blood vessels around the tumor. The nerves and blood vessels are very thin and can only be seen clearly under a microscope magnified ten times. Removing the tumor while preserving the normal nerve and blood vessel functions is a challenge in neurosurgery, and the risk is still very high.

Figure 2 Original copyright image, no permission to reprint

Pituitary adenoma wraps around the optic nerve, causing compression on the optic nerve, which may affect vision. After surgery, the compression is relieved and vision should improve. However, due to the different degree of tumor wrapping and hardness, the damage and irritation to the optic nerve are also different, so the vision of some patients will decrease after surgery. Some blood vessels look like earthworms, and they will spasm when stimulated. This is actually a form of self-protection. The same is true for cerebral blood vessels. Repeated stimulation will cause spasm, causing cerebral ischemia and affecting function. The pituitary stalk may be damaged during the operation, and diabetes insipidus will occur after the operation. These are some common complications of craniotomy.

There are ways to treat these complications. For example, after surgery, a substance called mouse nerve growth factor can be injected into the optic nerve to help it recover; hyperbaric oxygen therapy can be used to increase oxygen supply; anti-vasospasm drugs can be used to eliminate cerebral vasospasm; and vasopressin tablets can be used to control diabetes insipidus. Generally, these complications can be controlled and cured, but it takes a process.

3. What should you pay attention to after surgery for pituitary adenoma?

Pituitary adenoma is an endocrine tumor, and the pituitary function will be inhibited to a certain extent after surgery. Under normal circumstances, the pituitary gland secretes a lot of hormones. When the pituitary function is inhibited, it cannot normally secrete the hormones needed by the human body, and drugs must be used for replacement treatment for a period of time, including glucocorticoids, thyroid hormone, etc.

Generally, a follow-up examination is required about two weeks after surgery for pituitary adenoma to see if the hormone level has recovered. If the hormone secretion is normal, the replacement drug can be reduced or stopped. If the test indicators show that it has not recovered, drug replacement therapy needs to be continued. Some patients do not have follow-up examinations on time after discharge and continue to take hormone replacement drugs, which may cause drug side effects.

After the operation, the patient will be reexamined two weeks later, and then again three months later. After that, the patient can be reexamined once a year. Because pituitary adenomas may recur, regular reexaminations are required. The reexamination mainly involves blood tests to check pituitary hormone levels and magnetic resonance imaging to check the morphological changes of the brain after surgery.