Neurosurgery Treatments and Procedures
Treatment of Pituitary Adenoma
The pituitary gland is a small, fig-shaped gland about 10 mm in size that is the body’s central endocrine gland. It is located in the center of the skull behind the eyes near the crossing of the optic nerves (just above the nasal cavity, in the depression of the sphenoid bone called the Turkish saddle or the sella turcica). This tiny gland produces several key hormones that control the function of other hormonal glands and organs, thus regulating critical body processes, such as growth, metabolism, and reproduction. Since the pituitary gland is so important to the body, its anatomical location provides it with relative good protection against any mechanical impacts.
Pituitary adenoma is a tumor formed by the uncontrolled growth of cells in the anterior pituitary gland (adenohypophysis). About 10% of all intracranial tumors belong to this type. Adenomas appear with equal frequency among men and women, and mostly when a person is 30-40 years old. In 60% of cases, microadenomas smaller than the size of the gland (3 to 9 mm) occur, and in 40% of cases macroadenomas of 10 mm or more occur. In most cases, pituitary adenoma is a benign tumor characterized by the slow growth of cells that gradually increases pressure on the surrounding tissue. In half of the cases, it is a hormonally active tumor, which results in the release of higher than normal levels of one or more hormones into the blood. This results in various diseases: e.g. Cushing''s disease, caused by an excess of adrenocorticotropic hormone (ACTH) and, therefore, cortisone. Acromegaly as another example leads to an increased size of body organs, due to excessive growth hormone. An excess of prolactin may cause disorders of the menstrual cycle in women and infertility in both women and men.
Hormonally inactive tumors that do not secrete hormones can reach a size that causes physical pressure at the crossing of the optic nerves, which leads to impaired vision and narrowing of the vision field. Some patients may experience a variety of other physical symptoms, while the others have a symptomless course of the disease.
Surgical treatment of pituitary adenomas. Transsphenoidal removal of pituitary adenomas is the most commonly used surgical treatment today. With this method, surgical access to the pituitary gland is through the nose. Access into the cranial cavity is made through one of the nostrils using microsurgical instruments and a special microscope that allows the surgeon to see an enlarged operative field. During the procedure, the surgeon puts aside the nasal septum, enters the sphenoid sinus, and exposes the pituitary gland from below, through the sella turcica.
After identifying the tumor and removing it, the remaining space is filled with special biological glue or fat tissue taken from the patient''s abdomen. Surgery for pituitary adenoma is performed under general anesthesia.
Physiology of cerebrospinal fluid (CSF). In the cerebral hemispheres, as well as between the cerebellum and brainstem, there are cavities called the ventricles of the brain. In the walls of the lateral ventricles, in the upper wall of the third ventricle, and in the bottom wall of the fourth ventricle there is a special tissue called choroid plexus. This tissue creates a clear fluid called cerebrospinal fluid (CSF) at a constant rate of 500 ml. per day, though, at any given moment, there is only about 100-200 ml. of the fluid in the ventricular system of the brain itself. In the normal state, there is a balance between the rate of creation of cerebrospinal fluid and its absorption into the circulatory system.
The functions of CSF are to flush away the by-products of brain tissue metabolism and to assure mechanical protection of the brain from concussions. Since CFS is constantly produced, it flows from the lateral ventricles into the third ventricle and through a duct called the aqueduct into the fourth ventricle of the brain. Then, seeping through tiny holes, the liquid penetrates into the subarachnoid space and flows around the brain and spinal cord like a cushion, constantly being reabsorbed into the venous system of the brain.
Hydrocephalus or brain edema is characterized by an excessive accumulation of cerebrospinal fluid (CSF) in the ventricular system of the brain and in the subarachnoid space surrounding the brain. This creates increased pressure on the brain structure.
The reason for the accumulation of CSF in and around the brain is an imbalance between the secretion of CSF from the ventricles of the brain and its absorption (suction) into the circulatory system. This situation may arise from the blockage in CSF movement from the place of its secretion to the site of absorption into the circulatory system (the subarachnoid space). This type of abnormality is called obstructive hydrocephalus. Another cause of hydrocephalus may be destruction in the CSF absorption (suction) process, which is called aresobtive hydrocephalus. Hydrocephalus can occur in infants, children and adults, and its causes vary according to age. The most common cause of the disease by adults is tumors that block the ventricular system of the brain. Another cause may be a subarachnoid hemorrhage caused by hypertension, atherosclerotic changes of blood vessels in the brain, defects in blood vessels, or brain injury.
Particularly in the elderly, hydrocephalus occurs with normal intracranial pressure, during which the ventricles of the brain expand. The disease is typically accompanied by impaired memory, behavioral changes, walking disorders and loss of control over the sphincters.
Symptoms and Diagnosis. The most common symptoms of hydrocephalus for infants are an excessive increase in head circumference, changes in the shape of skull, and bulging and tension of the fontanelle. Strabismus and nystagmus, or involuntary oscillatory eye movements of high frequency (up to several hundred per minute), may also be symptoms of hydrocephalus.
In adults, due to the fact that the skull bones have fused, increased intracranial pressure caused by hydrocephalus may lead to more severe manifestations, such as impaired consciousness, memory loss, or unusual behavior. Sometimes the abnormality is accompanied by headaches, especially in the forehead, nausea, and impaired vision and hearing.
Diagnosis of hydrocephalus is made with CT. This method can reveal the size of the cerebral ventricles and determine the location of any obstructions and their causes, for example, tumor or hemorrhage.
Surgical treatment. A V-P SHUNT may be inserted to drain the fluid from the brain and reduce the pressure. The shunt connects the ventricles of the brain with the abdominal cavity to permit the fluid to flow out. This operation is performed under general anesthesia. Thin tubing fitted with a valve for one-way movement of fluid is inserted into the lateral ventricle of the brain, and then extended under the skin to the stomach, where it enters the abdominal cavity.
Stereotactic biopsy is a surgical procedure, applied to remove tissue samples of a brain tumor in order to analyze them on the presence of cancerous cells. The surgeon takes a sample of the suspected tissue by inserting a needle through a small hole in the skull without disrupting the integrity of vital adjacent brain structures. Strategies for further treatment are based upon the results obtained during the analysis of this sample. A stereotactic biopsy is performed under local anesthesia, which enables communication and interaction between the patient and the physician during the procedure. At the end of the procedure, the scalp skin is sutured and the hole in the cranium is closed.
Craniotomy is surgical removal of the calvaria for a variety of reasons, including:
- study or a biopsy of the brain and its membranes;
- removal of a brain tumor;
- treatment of cerebral aneurysms;
- reducing excessive intracranial pressure (e.g., subdural hematoma formed due to a head injury).
Removal of brain tumor requires precise definition of the boundaries of the tumor and its separation from neighboring healthy tissues. In the treatment of benign tumors it is sufficient to remove the tumor completely, without the need for radiotherapy and chemotherapy, because these tumors usually do not recur. In contrast, when a malignant tumor is removed, surgical treatment will be followed by radiotherapy and/or chemotherapy, because there is always the possibility of its relapse.
Cerebral aneurysm is damage to the arterial walls in the brain indicated by a protrusion of the blood vessel with a high risk of rupture and bleeding into the brain. Treatment of aneurysms includes the precise definition of their location and blocking blood flow through the damaged vessels by clipping or endovascular occlusion before rupture can take place.
Hematoma. Brain hematoma is an abnormal localized collection of clotted or partially clotted blood situated in the space between the scull and the brain or in brain itself. Brain hematoma is caused by a break in the wall of a blood vessel, as in the case of an aneurysm, or by trauma. Normal treatment for hematomas involves inserting a drainage tube to allow the excessive blood to flow out.