Cushing used an occipital bur hole for EVD insertion during the removal of cerebellar astrocytomas. After the 1960s and the introduction of ventriculoperitoneal shunts with different types of valves, the management of hydrocephalus was dramatically improved. Many patients during diagnosis were in critical clinical condition mainly because of illness progression, and the insertion of a ventriculoperitoneal shunt preceded tumor removal. The risk of upward herniation was always present, and many surgeons preferred EVDs or ventriculoperitoneal shunts with high pressure settings preoperatively. The development of sophisticated endoscopes, optics, and monitors allowed the increasing performance of ETVs since the early 1990s. Today, ETV is the most widely used treatment option for this type of hydrocephalus, either pre- or post-tumor removal.
Understanding of Disease
- 1989 – importance for dural closure described: Dias and Albright had earlier suggested that significant factors were the severity of preoperative hydrocephalus and the type of dural closure (9).
- 1994 – risk factors for hydrocephalus described: In 1994 Culley et al. studied different factors that could affect the need for postoperative shunt placement. They found that age < 3 years, midline tumor location, subtotal resection, prolonged EVD requirement, formation of pseudomeningocele, CSF infections, and use of cadaveric dural grafts were statistically significant and correlated with persistent postoperative hydrocephalus (7).
- 2007 – importance of tumor type and its resection described: Due-Tonnessen and Helseth reported the cure rate of hydrocephalus when treated with tumor surgery alone. They found that tumor type was a significant prognosticator with a cure rate of 83% for astrocytomas but a cure rate of only 47% for medulloblastomas (10).
- 2001 – use of ETV to manage pre-tumor resection described: A retrospective analysis in 2001 supported that patients treated with ETV before tumor removal had a reduced incidence of postoperative hydrocephalus requiring treatment, compared to those that were treated only with tumor removal (6% vs. 26.8%) (35). Controversies arose concerning how many patients underwent a possibly unnecessary ETV procedure before tumor removal, since it was found that the long-term incidence of hydrocephalus requiring treatment after tumor removal was low, approximately 15% (5, 14).
Controversy over which patients with hydrocephalus to treat
- Cerebellar astrocytomas, medulloblastomas, and ependymomas: Evolving practice is to consider tumor resection as the primary treatment for hydrocephalus that is present at the time of tumor presentation. This reflects the fact that only 25% of patients will require permanent treatment of hydrocephalus with either a shunt or ETV after the primary tumor resection clears the obstruction in flow of CSF.
- Brainstem tumors: As there is no issue of total excision of the tumor and removal of the obstruction to CSF flow, an ETV or shunt is typically placed at the time of presentation of the hydrocephalus, or when symptoms progress as a temporizing measure.
- Shunting devices: The era of CSF valves began in the 1950s with the efforts of Nulsen, Spitz, and Holter (46). The introduction of silicone tubes by Pudenz supplemented the revolutionary treatment of hydrocephalus with closed CSF shunts (46). In recent years, important advances have been made with regard to different type of valves (adjustable, flow-regulating, gravity-activated), antisiphon devices, and antibiotic-impregnated tubes.
- Endoscopic hardware: In the beginning of the 20th century there were attempts to insert endoscopic devices into human cavities for diagnostic purposes. Rigid tubes with limited light sources were the first endoscopes. The evolution of imaging transmission through flexible fibers of glass and the introduction of cold light sources were the crucial steps for wider usage in many medical specialties.
- MRI: MRI is the imaging modality of choice for neuroscience. It has provided the ability to see not only the fluid spaces of the brain but also the flow patterns of CSF through the brain. This knowledge can be essential when determining treatments for tumor-associated hydrocephalus.
- Microsurgery: Pioneered by Yasargil, the main principles of microsurgery in the nervous system have allowed approaches to previously unreached brain tumors with improved extent of tumor resection and minimal damage to surrounding normal tissues (47). These advances have resulted in a lessening of persisting hydrocephalus.
- ETV: The initial ideas of Dandy for direct communication of the third ventricle to the basal cisterns involved open procedures (48). Neuroendoscopic attempts of Lespinasse and Mixter were limited by poor instrumentation (48). The application of shunts further diminished the indications for endoscopic techniques. In the 1990s the first convincing series for the efficacy of ETV made it widely accepted and a treatment of choice for obstructive hydrocephalus. In experienced hands, ETV is an easy and straightforward procedure that can offer control of hydrocephalus and reduce ICP without the need of hardware, tubing, and metals left behind. Of course, complications exist and they can be devastating (6); thus, performing an ETV should be fully justifiable, especially if the procedure is done prophylactically.
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