Overview of Transsphenoidal Hypophysectomy
Surgery at the center of the skull has been a daunting task for surgeons because it’s hard to reach this location. One of these surgeries is the operation on the pituitary gland, known as a pituitary surgery or hypophysectomy. The technique for this procedure has evolved significantly over the years. It started as an open surgery where the skull had to be opened (referred to as a craniotomy). Nowadays, we have developed much less invasive techniques where the surgery is performed endoscopically (using a small camera and other instruments) through the nose, specifically via the sphenoid sinuses which lie close to the pituitary gland.
This modern approach, also known as the transsphenoidal approach, was popularized way back in 1910. Surgeons Harvey Cushing and Oskar Hirsch were leading figures in medical history who championed this technique. Interestingly, it lost some popularity when Cushing started favoring a technique called the transcranial approach, which tackled the pituitary gland from within the skull. Nonetheless, other surgeons like Dott and Guiot continued to refine the transsphenoidal method. Hardy even introduced microsurgical techniques that improved the precision of these surgeries.
In general, surgeries to reach the pituitary gland come in two main types: transcranial (through the skull) and extracranial (outside the skull). Currently, the transcranial technique, which can be done using a microscope for higher precision, is reserved for cases where the transsphenoidal approach is not applicable. There are two major transcranial techniques: the pterional approach (approaching from the side of the forehead) and the anterior subfrontal approach (coming from the front of the forehead). The pterional technique has the advantage of providing a more straightforward route to the pituitary gland with minimal disturbance to the brain. The anterior subfrontal approach also allows a clear view of the pituitary gland but is less popular due to the risk of damaging the nerves responsible for smell and the frontal sinuses (air-filled spaces in the skull).
The extracranial techniques mainly involve microscopic transsphenoidal approaches or endoscopic transsphenoidal techniques. These methods might sound very techno-speak, but all they mean is that these operations go through the nose and into the sphenoid sinus. The operation will either use a microscope for magnification (microscopic) or a small camera (endoscopic). However, traditional microscopic techniques often lead to complications like facial swelling and pain, and a persistent need for nasal packing or splints to aide in healing.
Introduced by Jankowski in 1992, endoscopic pituitary surgery quickly grew popular due to its advantages such as shorter hospital stay, a broader view of the surgical area, and better maneuverability. This modern procedure has transformed skull base surgeries and made them considerably less invasive and more efficient.
Anatomy and Physiology of Transsphenoidal Hypophysectomy
The pituitary gland is a tiny organ located in a small, saddle-shaped cavity in a bone at the base of your brain, known as the sphenoid bone. This special cavity is called the sella turcica or pituitary fossa. The lower part of this cavity forms the roof of air pockets, called sphenoid sinuses, found behind your nose.
In medical procedures, the sphenoid sinuses can be reached by doctors using an endoscope, a small, flexible tube with a light and camera attached. The endoscope is carefully navigated through a passage between the nasal septum, or wall dividing the nostrils, and an anatomical structure called the middle turbinate, situated inside the nose.
The amount of air space within the sphenoid sinuses can vary from person to person. In some cases, this space can extend into other parts of the facial bones, resulting in a lateral recess. This may lead to the exposure of certain nerves.
During a procedure inside a well-aired sinus, doctors may come across structures like the optic nerve, carotid artery, and the pituitary fossa. Once a wall, known as the inter-sinus septum, is removed, all these structures become clearly visible. The pituitary fossa, the small depression housing the pituitary gland, can be easily seen lying between the cavernous sinus, a complex of veins, and the curve of the carotid artery.
However, anatomical differences in each person can make these types of procedures a challenge. A deviated septum or other nasal conditions can make the nasal passage narrower. Other diseases, pathology, or prior surgeries in the sinus area can also complicate access to the pituitary gland. For a successful procedure, the doctor has to study a CT scan of the sphenoid sinuses and its surrounding structures very carefully. This is important to understand the extent of sphenoid sinuses and any additional anomalies that may affect the procedure.
Risks of these types of procedures include potential injury to the optic nerve – which occurs in around 4% to 8% of cases – and the carotid artery, with an estimated risk around 5% in pituitary surgeries.
Why do People Need Transsphenoidal Hypophysectomy
Pituitary adenomas, small or large tumours in the pituitary gland, are often the reason for a surgical procedure called transsphenoidal hypophysectomy. This is a kind of surgery performed to remove these tumours through the nose and sinus cavity. Usually, this operation is necessary for non-secreting adenomas, meaning tumours that don’t produce hormones, but cause issues like vision problems, a variety of symptoms from hormonal imbalance (hypopituitarism), sudden severe headache and double vision (pituitary apoplexy), or if they are growing, as seen on medical images taken over time.
The surgery is also advised for secreting adenomas, which are tumours producing hormones, but only if these are not responding to medication.
Other similar abnormalities around the same area of the brain (sellar lesions) might also require this kind of surgery, like Rathke’s cyst, craniopharyngiomas (noncancerous tumours near the pituitary gland), meningiomas (tumours that grow from the protective membranes around the brain and spinal cord), chordomas (rare malignant tumours), or even metastatic lesions which are secondary cancer tumours formed from a cancer that started somewhere else in the body.
When a Person Should Avoid Transsphenoidal Hypophysectomy
There are certain conditions where the transsphenoidal approach (a surgical method accessing the brain through the nose and sinuses) shouldn’t be used. It’s not advisable if a person has sphenoid sinusitis, which is an infection in a particular sinus near your nose. It’s also not suggested if someone has unusual blood vessels in their skull, has abnormally large arteries in the middle of their neck (ectatic midline carotid arteries), or if a tumor has significantly grown towards the side in a region above the pituitary gland, especially when the central point of this growth is to the side of the carotid artery.
There are also situations where this procedure might not be the best choice, but it’s not outright forbidden. For example, if a person’s sphenoid sinus (part of the sinus system behind your eyes and just below your brain) isn’t filled with air as it should be, or if a benign tumor known as adenoma has grown extensively above the pituitary gland. It might also not be suitable if someone has a condition where a small part of the brain (diaphragma sellae) is unusually tight or restricted.
Equipment used for Transsphenoidal Hypophysectomy
If you are having a procedure called an “endoscopic transsphenoidal hypophysectomy,” which is a type of sinus surgery, your doctor will use a range of specific medical tools. These include a high-speed drill and agents that stop bleeding, for example, gelatin mixed with thrombin (a protein that helps blood clot).
In some cases, if the surgeon opts for a microscopic approach, they will need a set of tools used in the treatment of the lower face, mouth and jaw (maxillofacial tools). These include a device called a Hardy self-retaining bivalve speculum that helps keep the surgical area open during the procedure.
Furthermore, an Image Guidance Navigation (IGN) system is usually used in procedures that need to be repeated, ones where the tumour has grown around the sinuses, or in cases where the structure of your sinuses isn’t normal. This system helps the surgeon navigate during the operation.
Additionally, an intraoperative MRI (live MRI carried out during surgery) can be very useful in this type of surgery. It offers up-to-date images that show changes in the size of the tumor, the lining of the brain and spinal cord (dura), and normal pituitary region. This allows doctors to work more accurately during your surgery.
Who is needed to perform Transsphenoidal Hypophysectomy?
Endoscopic surgery to remove pituitary tumors usually needs two surgeons or a technique called ‘four-handed’. One surgeon uses an instrument called an endoscope to light up and magnify the area inside the body, so the other surgeon can see clearly to remove the tumor. The perfect team for this surgery would include a skilled sinus surgeon, who can reach the pituitary gland quickly and safely, and a brain surgeon, who knows how to operate on this complex region of the body.
Nowadays, brain surgeons can perform endonasal surgery (a surgery through the nose) on their own. However, if there are any deformities in the nose like a bent nasal wall, nasal polyps, or a pituitary gland that’s not hollowed out, an ear-nose-throat (ENT) specialist can make the surgery quicker and easier. Usually, the ENT specialist clears a path to the covering of the pituitary gland, and then the brain surgeon opens up that covering to remove the tumor.
Having a skilled sinus surgeon can be really helpful, especially for more complex cases where the tumor extends into places like the cavernous sinus (a space in the skull behind the eye) or behind the carotid artery. These surgeons can also help manage complications that might happen after the operation like stiff nasal passages or a nose condition where the nasal lining dries up and shrinks. That’s why it’s important for the brain surgeon and the ENT specialist to work closely together.
Preparing for Transsphenoidal Hypophysectomy
Before considering surgery, it’s very important to get a full medical check-up. This includes an in-depth examination of your head and neck, as well as tests to check your vision such as assessing how well you can see, how your eyes move, and whether there’s anything blocking your view. A special scope is used to look inside your nose to make sure nothing is obstructing your nasal passage or causing disease, which may need to be dealt with before or during surgery.
In addition, it’s crucial to evaluate your pituitary gland, a small pea-sized gland located at the base of your brain that produces hormones. This is done by an endocrinologist, a doctor who specializes in hormone-related conditions. If this gland is not working properly before surgery, it can increase the risk of hypopituitarism, a condition where the pituitary gland fails to produce enough hormones. This could complicate your surgery and recovery.
During the evaluation, your medical team will identify whether the tumor is producing hormones or not, understand the baseline function of your pituitary gland, and decide if any medical therapy would be effective before surgery.
Testing of different hormones, including growth hormone, cortisol, serum prolactin, triiodothyronine, thyroxine, follicle-stimulating hormone (FSH), and luteinizing hormone (LH) should be done. The levels of thyroid and cortisol hormones are very important before surgery. In case of low levels of cortisol or thyroid hormones, replacement with artificial hormones or thyroid supplements is essential to prepare for the surgery.
Imaging of your head using CT scan and MRI scan must be done. These scans give a detailed view of the inside of your head, helping doctors to plan the surgery. MRI is preferred over CT scan as it offers better images of soft tissues, which helps to precisely locate important structures like the optic nerve, which carries visual information from the eye to the brain, and cavernous sinuses, which are spaces located at the base of the brain. The MRI can also give a clear picture of the exact tumor size and its consistency, and whether it spreads to other areas.
Smaller tumors, called microadenomas, can be a bit challenging to locate. However, larger tumors, known as macroadenomas, are usually easier to spot. These imaging techniques are also used to evaluate bony erosion and expansion of the sella, the area where the pituitary gland resides. More importantly, they help in surgical planning as it can indicate any abnormalities that could complicate surgery.
If you’ve had any prior nasal surgery, your doctors will need this information as it can influence the planning and preparation of this surgery. If the previous surgery was due to chronic disease or a tumor, they will assess its current status using nasal endoscopy and imaging. If the condition hasn’t been completely resolved, another surgery may need to be done before the pituitary surgery. If the previous surgery involved the nasal septum, the wall separating the nostrils, a close evaluation of the septum will be done to check for any scars or perforations.
How is Transsphenoidal Hypophysectomy performed
For the procedure, the patient lies flat on their back with their head safely held in place by a special type of headrest known as a Mayfield head holder. Inserting a small drain tube into their bladder is required for accurate management of fluid levels, particularly as there’s a risk of a type of water imbalance known as diabetes insipidus. Certain medicines are applied inside the nose to reduce blood flow and swelling. The belly or thigh is prepared as the area from where a tissue sample might be taken. In certain cases where a technique using an endoscope (a thin tube with a light and camera attached to it) is used, a device that enables the healthcare provider to track the precise location of the instruments used during the procedure is attached to the patient’s forehead.
The surgery begins with both sides of the nose being treated to reduce swelling and correct physical obstructions like a deviated septum. The surgeon then makes space between the dividing wall of the nostrils and the curved structure along the sidewall of the nasal passage, so they can later use specialized instruments. A special flap of tissue in the nose can be prepared to cover the operated area if larger pituitary approaches are expected. The surgeon identifies and widens the small hole that leads to a hollow space within the facial bone called the sphenoid sinus. After this, multiple steps are followed to expose the pituitary gland. These steps vary based on the surgical approach the surgeon uses.
Next, the surgeon strips off the mucosa, a moist tissue that lines certain parts of the inside of your body, from the sphenoid sinus. This step is taken to avoid the development of a cyst filled with mucus and prevent nosebleeds. Then, the surgeon identifies certain anatomical landmarks within the sinus and opens up the sella, a saddle-shaped area at the base of the brain where the pituitary gland is located.
Following this, a cut is made in the tough outer layer covering the brain and spinal cord to expose the pituitary gland. The surgeon aims to remove the tumor without affecting the pituitary gland. The tumor is then removed. Special endoscopes are used if the tumor has spread to areas surrounding the pituitary gland.
After tumor removal, the void left is filled with a substance similar to a sponge and the membrane covering the brain and spinal cord is put back in place. A protective layer made from special tissue taken from the inside of the nose is fixed over this membrane using a substance derived from human plasma and a special type of surgical sealant.
After this, various techniques are used to rebuild the area. This mainly includes using a number of layers of different substances to patch up the hole and using a fat graft taken from the belly or a connective tissue graft. These substances support and bolster the repair.
Possible Complications of Transsphenoidal Hypophysectomy
There is strong evidence suggesting that endoscopic pituitary surgeries (that’s when a surgeon uses a tube with a light and a camera attached to it to examine or operate on the pituitary gland) are safer compared to traditional microsurgery using small tools through the skull or upper lip. However, both methods are just as effective in treating conditions related to the pituitary gland, which is a small organ in the brain that makes hormones.
Complications from Surgery
Complications can occur at every stage of the surgery, although they are not very common. These may include damage to the eye, changes in the shape of the nose, loss of smell, leakage of cerebrospinal fluid (a clear, colorless body fluid found in the brain and spinal cord), and excessive bleeding from damage to an artery in your face.
Complications can also occur in the sphenoid sinus, an empty space in your skull located behind your nose. These include inflammation of the sinus, injury to the artery or the optic nerve (which connects the eye to the brain), and mucoceles, which are sac-like swellings filled with mucus.
The process of removing the tumor can also present complications. These include leakage of cerebrospinal fluid, diabetes insipidus (a condition caused by an imbalance of water in the body), a deficiency in pituitary hormones, meningitis (inflammation of the membranes surrounding the brain and spinal cord), postoperative bleeding, injury to the artery or optic nerve, muscle spasm in the arteries, paralysis of the muscles in the eye, bleeding in the space between the brain and the thin tissues that cover the brain, and pneumocephalus, a condition where air gets trapped within the brain.
Immediate Postoperative Complications
Immediately after the surgery, complications may include leakage of cerebrospinal fluid, sinus inflammation, and meningitis. In case of a leak in the fluid surrounding the brain after the surgery, the patient is advised to rest, and a drain is placed in the lower back. If the leak does not improve in 24 hours, the doctors will need to explore and close the defect. Other immediate complications include worsening of vision due to bleeding or manipulation and severe bleeding from arteries.
Long Term Complications
Common long term complications include nasal congestion, mild nasal bleeding, pain over the region of the nose and upper jaw, nasal scabbing, scarring of the mucous membrane, swelling around the eyes, and numbness of the upper teeth. Some people might experience damage to their nasal mucus membrane which can lead to sinusitis (inflammation or swelling of the tissue lining the sinuses). There could also be changes in the sense of smell. These complications tend to be more common with a sublabial approach (through the upper lip) compared to a transnasal approach (through the nose).
Endocrine Complications
The most common hormonal complication early after surgery is abnormalities in the secretion of antidiuretic hormone (a hormone that regulates the balance of water in the body). These include diabetes insipidus and inappropriate secretion of the antidiuretic hormone. Diabetes insipidus is the most common hormonal complication after surgery on the pituitary gland, with the incidence ranging from 5% to 35%.
Postoperative Care
After the surgery, patients are monitored in an Intensive Care Unit for any neurological decline, nosebleeds, changes in vision, diabetes insipidus, or low blood pressure due to acute decrease in cortisol (a hormone that helps your body respond to stress). If they were already receiving treatment for hormonal deficiencies, these treatments, along with close monitoring of electrolyte levels in the body, need to be continued after the surgery. If their pituitary function was normal before surgery, levels of certain hormones (cortisol and prolactin) are measured the morning after the procedure.
What Else Should I Know About Transsphenoidal Hypophysectomy?
A transsphenoidal hypophysectomy is a surgical procedure commonly used to remove tumors in and around your pituitary gland, which is located at the base of your brain. This method is quite effective and typically has very low risk of complications, meaning you will likely feel better quicker and spend less time in the hospital after surgery.
In addition to removing the tumors, this type of surgery can also help improve hormone balance in your body (if it was out of whack due to the tumor.) It also helps to ease pressure on the pituitary gland and other nearby structures such as the optic nerves, which transmit information from your eyes to your brain. So, in addition to feeling better, you might also notice improvements in vision.
Importantly, every person’s circumstances are unique and your doctor will consider many factors to decide the best course of action in your specific case.
