Endoscopic third ventriculostomy | |
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Specialty | neurosurgery |
Endoscopic third ventriculostomy (ETV) is a surgical procedure for treatment of hydrocephalus in which an opening is created in the floor of the third ventricle using an endoscope placed within the ventricular system through a burr hole. This allows the cerebrospinal fluid to flow directly to the basal cisterns, bypassing the obstruction. Specifically, the opening is created in the translucent tuber cinereum on the third ventricular floor. [1]
The ETV procedure is used as an alternative to a cerebral shunt [2] mainly to treat certain forms of noncommunicating obstructive hydrocephalus (such as aqueductal stenosis), but since the ETV was introduced as an accepted treatment modality the range of etiologies for which it is used has grown significantly. Whereas at first it was almost exclusively performed in patients with noncommunicating obstructive hydrocephalus (e.g. aqueductal stenosis or intracerebral tumor), in the present day patients with communicating obstructive hydrocephalus (e.g. post intracranial hemorrhage or post intracranial infection) also may be eligible for treatment by means of ETV.[ citation needed ]
A major advantage of performing an endoscopic third ventriculostomy over placement of a cerebrospinal fluid shunt is the absence of an implanted foreign body. A shunt has risk of infection and failure for which subsequent surgery is needed. Complications of ETV include hemorrhage (the most severe being due to basilar artery rupture), injury to neural structures (e.g. hypothalamus, pituitary gland or fornix of the brain), and late sudden deterioration. [3] Infection, hematoma, and cerebrospinal fluid leaks may present in the direct postoperative period.
Failure of the ETV occurs. This can be due to occlusion of the ventriculostomy (e.g. closure of the ventriculostomy, formation of subarachnoid membranes in the pontine cistern or other mechanisms). Although 60 - 90% of failures occur in the first few months after treatment, long-term failure also occurs (failures occurring after 7 years have been reported). [4] In a very small subgroup of patients a complication of ETV can be rapid late deterioration. [5] The mechanism is not clear.
When it is not possible to perform an ETV for different reasons, an alternative treatment is opening the lamina terminalis anterior to the third ventricle. [6] The effectiveness of this approach is not certain. [7]
The surgical treatment options for hydrocephalus are, as previously mentioned, implantation of a cerebral shunt and ETV. Especially in the youngest age group (younger than two years of age) it remains uncertain what is the superior treatment modality. Currently, a large international, multicenter study is conducted to address this issue. Patients under the age of two, diagnosed with aqueductal stenosis without a history of preterm birth or other associated brain anomalies are being included (International Infant Hydrocephalus Study). [8] [9]
There is a discussion regarding the additional benefit of combining endoscopic third ventriculostomy with choroid plexus cauterization. This combined procedure is referred by the abbreviation "ETV/CPC" and has also been called the "Warf Procedure" [10] after Dr. Benjamin Warf. There have been research studies published about the experience of authors with this procedure. The lion's share of the data that show favorable results is reported on patients in Africa. [11] More recent studies from research groups in Western countries also show that the combination of ETV with choroid plexus cauterization seems to be effective, safe, and durable, [12] and that predictions for success are similar to those of ETV alone. [13] The degree of choroid plexus cauterization in infants might be dependent on the experience of the neurosurgeon (learning curve) and thus surgeons training might improve results. [14] The ETV/CPC procedure is now being performed in a number of hospitals in US and Canadian cities, including Seattle, Washington; Houston, Texas; Calgary, Alberta; Toronto, Ontario; Salt Lake City, Utah; and Boston, Massachusetts. [15]
The chances of success of treatment of a pediatric patient can be calculated using the ETV success score (ETVSS). [16] [17] [18] The ETVSS is derived from patient age, etiology of hydrocephalus and history of previous cerebrospinal fluid shunt (e.g. ventriculo-peritoneal shunt). The percentage probability of ETV success = Age score + Etiology score + Previous shunt score. A two years old patient with hydrocephalus due to aqueductal stenosis, without previous shunt would have an 80% chance of success (40 for age + 30 for etiology + 10 for no previous shunt = 80).
ETVSS table [16]
Score | Age | Etiology | Previous Shunt |
---|---|---|---|
0 | < 1 month | Post-infectious | Previous shunt |
10 | 1 month to < 6 months | No previous shunt | |
20 | Myelomeningocele, intraventricular hemorrhage, non-tectal brain tumor | ||
30 | 6 months to < 1 year | Aqueductal stenosis, tectal brain tumor, other etiology | |
40 | 1 year to < 10 years | ||
50 | ≥ 10 years |
The ETVSS was derived and validated without the use of adult data and it has inadequate discriminative ability in mixed adult and pediatric populations. [19]
After a patient gets readmitted with recurrent clinical and radiological symptomatology of hydrocephalus, it is unclear what the next step in treatment should be. Implantation of a cerebrospinal fluid shunt or repeat ETV. Data suggest that a second ETV might be worthwhile if implantation of cerebrospinal fluid shunt can be avoided. [20] [21]
In most countries and neurosurgical centres, the ETV procedure is part of the basic neurosurgery training program. For the sake of teaching and practicing, various simulation models have been developed. Virtual reality simulators, [22] and synthetic simulators. [23] [24] This allows neurosurgical trainees to practice skills in a low-risk environment. Educators can select either a virtual reality simulator or a physical model for the training of residents, the selection should be based on educational objectives. Where training focused on anatomy and using anatomical landmarks for decision making may better be aided with virtual reality model, the focus on familiarizing the resident with endoscopic equipment and developing manual dexterity may be better learned on a physical model. [25] The technical skill and competency of a trainee can be evaluated using the Neuro-Endoscopic Ventriculostomy Assessment Tool (NEVAT). [26]
Cerebrospinal fluid (CSF) is a clear, colorless body fluid found within the tissue that surrounds the brain and spinal cord of all vertebrates.
Hydrocephalus is a condition in which an accumulation of cerebrospinal fluid (CSF) occurs within the brain. This typically causes increased pressure inside the skull. Older people may have headaches, double vision, poor balance, urinary incontinence, personality changes, or mental impairment. In babies, it may be seen as a rapid increase in head size. Other symptoms may include vomiting, sleepiness, seizures, and downward pointing of the eyes.
Hydranencephaly is a condition in which the brain's cerebral hemispheres are absent to a great degree and the remaining cranial cavity is filled with cerebrospinal fluid. "Cephalic" is the scientific term for "head" or "head end of body".
The ventricular system is a set of four interconnected cavities known as cerebral ventricles in the brain. Within each ventricle is a region of choroid plexus which produces the circulating cerebrospinal fluid (CSF). The ventricular system is continuous with the central canal of the spinal cord from the fourth ventricle, allowing for the flow of CSF to circulate.
Normal-pressure hydrocephalus (NPH), also called malresorptive hydrocephalus, is a form of communicating hydrocephalus in which excess cerebrospinal fluid (CSF) occurs in the ventricles, and with normal or slightly elevated cerebrospinal fluid pressure. As the fluid builds up, it causes the ventricles to enlarge and the pressure inside the head to increase, compressing surrounding brain tissue and leading to neurological complications. The disease presents in a classic triad of symptoms, which are memory impairment, urinary frequency, and balance problems/gait deviations. The disease was first described by Salomón Hakim and Adams in 1965.
In the brain, the interventricular foramina are channels that connect the paired lateral ventricles with the third ventricle at the midline of the brain. As channels, they allow cerebrospinal fluid (CSF) produced in the lateral ventricles to reach the third ventricle and then the rest of the brain's ventricular system. The walls of the interventricular foramina also contain choroid plexus, a specialized CSF-producing structure, that is continuous with that of the lateral and third ventricles above and below it.
Dandy–Walker malformation (DWM), also known as Dandy–Walker syndrome (DWS), is a rare congenital brain malformation in which the part joining the two hemispheres of the cerebellum does not fully form, and the fourth ventricle and space behind the cerebellum are enlarged with cerebrospinal fluid. Most of those affected develop hydrocephalus within the first year of life, which can present as increasing head size, vomiting, excessive sleepiness, irritability, downward deviation of the eyes and seizures. Other, less common symptoms are generally associated with comorbid genetic conditions and can include congenital heart defects, eye abnormalities, intellectual disability, congenital tumours, other brain defects such as agenesis of the corpus callosum, skeletal abnormalities, an occipital encephalocele or underdeveloped genitalia or kidneys. It is sometimes discovered in adolescents or adults due to mental health problems.
The median portion of the wall of the forebrain consists of a thin lamina, the lamina terminalis, which stretches from the interventricular foramen to the recess at the base of the optic stalk and contains the vascular organ of the lamina terminalis, which regulates the osmotic concentration of the blood. The lamina terminalis is immediately anterior to the tuber cinereum; together they form the pituitary stalk.
Choroid plexus papilloma, also known as papilloma of the choroid plexus, is a rare benign neuroepithelial intraventricular WHO grade I lesion found in the choroid plexus. It leads to increased cerebrospinal fluid production, thus causing increased intracranial pressure and hydrocephalus.
A colloid cyst is a non-malignant tumor in the brain. It consists of a gelatinous material contained within a membrane of epithelial tissue. It is almost always found just posterior to the foramen of Monro in the anterior aspect of the third ventricle, originating from the roof of the ventricle. Because of its location, it can cause obstructive hydrocephalus and increased intracranial pressure. Colloid cysts represent 0.5–1.0% of intracranial tumors.
A cerebral shunt is a device permanently implanted inside the head and body to drain excess fluid away from the brain. They are commonly used to treat hydrocephalus, the swelling of the brain due to excess buildup of cerebrospinal fluid (CSF). If left unchecked, the excess CSF can lead to an increase in intracranial pressure (ICP), which can cause intracranial hematoma, cerebral edema, crushed brain tissue or herniation. The drainage provided by a shunt can alleviate or prevent these problems in patients with hydrocephalus or related diseases.
Intraventricular hemorrhage (IVH), also known as intraventricular bleeding, is a bleeding into the brain's ventricular system, where the cerebrospinal fluid is produced and circulates through towards the subarachnoid space. It can result from physical trauma or from hemorrhagic stroke.
Choroid plexus tumors are a rare type of cancer that occur from the brain tissue called choroid plexus of the brain. Choroid plexus tumors are uncommon tumors of the central nervous system that account for 0.5–0.6% of intracranial neoplasms in people of all ages. Choroid plexus papilloma, atypical choroid plexus papilloma, and choroid plexus carcinoma are the three World Health Organization grades for these cancers, respectively. Children under the age of five account for 10% of cases of choroid plexus tumors. In children and adults, respectively, the lateral ventricle and the fourth ventricle are common locations, About 5% of all choroid plexus tumors are located in the third ventricle. Along with other unusual places such the cerebellopontine angle, the Luschka foramen, or brain parenchyma, the third ventricle is a rare location for choroid plexus tumors. Together, atypical choroid plexus papilloma, and choroid plexus carcinoma make up around 25% of all choroid plexus tumors. Although there have been reports of third ventricle choroid plexus papillomas in people in their fifth decade of life, only 14% of choroid plexus tumors are reported to arise in infants. Most findings indicate that choroid plexus tumors have no sex predilection.
A choroid plexus carcinoma is a type of choroid plexus tumor that affects the choroid plexus of the brain. It is considered the worst of the three grades of chord plexus tumors, having a much poorer prognosis than choroid atypical plexus papilloma and choroid plexus papilloma. The disease creates lesions in the brain and increases cerebrospinal fluid volume, resulting in hydrocephalus.
An external ventricular drain (EVD), also known as a ventriculostomy or extraventricular drain, is a device used in neurosurgery to treat hydrocephalus and relieve elevated intracranial pressure when the normal flow of cerebrospinal fluid (CSF) inside the brain is obstructed. An EVD is a flexible plastic catheter placed by a neurosurgeon or neurointensivist and managed by intensive care unit (ICU) physicians and nurses. The purpose of external ventricular drainage is to divert fluid from the ventricles of the brain and allow for monitoring of intracranial pressure. An EVD must be placed in a center with full neurosurgical capabilities, because immediate neurosurgical intervention can be needed if a complication of EVD placement, such as bleeding, is encountered.
Bobble-head doll syndrome is a rare neurological movement disorder in which patients, usually children around age 3, begin to bob their head and shoulders forward and back, or sometimes side-to-side, involuntarily, in a manner reminiscent of a bobblehead doll. The syndrome is related to cystic lesions and swelling of the third ventricle in the brain.
CURE Children's Hospital of Uganda (CCHU) is a specialized children's neurosurgery hospital in Uganda. It is a private hospital, owned and operated by CURE International. The hospital is also a teaching center in pediatric neurosurgery for Sub-Saharan Africa.
Aqueductal stenosis is a narrowing of the aqueduct of Sylvius which blocks the flow of cerebrospinal fluid (CSF) in the ventricular system. Blockage of the aqueduct can lead to hydrocephalus, specifically as a common cause of congenital and/or obstructive hydrocephalus.
Benjamin Warf is an American pediatric neurosurgeon. Warf was awarded a MacArthur Fellowship in 2012.
Sandi Lam is a Canadian pediatric neurosurgeon and is known for her research in minimally invasive endoscopic hemispherectomy for patients with epilepsy. Lam is the Vice Chair for Pediatric Neurological Surgery at Northwestern University and the Division Chief of Pediatric Neurosurgery at Lurie Children's Hospital. She has spent her career advancing pediatric brain surgery capabilities globally through her work in Kenya performing surgeries as well as training and mentoring local residents and fellows.
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