Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.115051
Source of Support: None, Conflict of Interest: None
Endoscopic techniques are increasingly being used in recent times for various spinal and brain pathologies. Although endoscopic neurosurgical technique holds the potential for reducing morbidity, it is also associated with limitations such as steep learning curve, obstruction in manipulation of instruments by telescope in an already limited exposure, proximal blind spot, visual obscuration, disorientation, loss of stereoscopic image and others. Neuroendoscopy is distinct from micro-surgery and a thorough understanding of the technique and its limitations is required to get maximal benefit. Difficulties in controlling bleeding, longer operative time are common obstacles with this technique, especially in early learning curve. Higher complication rate during initial learning curve can be reduced by attending live workshops, practice on models and hands on cadaveric workshops. Large vascular lesions should be avoided and a thorough knowledge of possible complications and techniques to avoid such complications can improve results in endoscopic surgery.
Keywords: Complications, endoscopic surgical procedure, endoscopy, intraoperative complication, minimal invasive surgical procedure, neuroendoscopy, neurosurgical procedure, operative surgical procedure, post-operative complications
Endoscopy is having an increasingly prominent role in neurosurgery. , It has advanced both as an independent treatment modality and as an adjunct to micro-neurosurgery for various neurologic disorders. , Although endoscopic technique has many advantages, it is also associated with unique obstacles, which must be anticipated. Endoscopic procedures require development of skills unique to endoscopy to avoid complications. 
This article will discuss about the techniques that could be used to reduce complications of endoscopic procedures and management of the complications with special reference to endoscopic third ventriculostomy (ETV). This review is based on personal experience of more than 1500 neuroendoscopic surgeries performed by the senior author and review of relevant literature.
The equipment required to perform the procedure and image quality needs to be checked before induction of anesthesia. All instruments such as sheaths, biopsy forceps, scissors and graspers, should be inspected for proper functioning. These instruments should properly fit down the working channel of the endoscope. Instrument tip should be slightly curved to allow better visualization.  Single shaft slender instruments are preferred because of the less space occupied by such equipments in an already compromised field.
Orientation and position of camera
Camera should be placed in the correct position and orientation should be checked by anterior-posterior and side movement. Use of long telescope can keep camera away from the operative site, which allows easy and unobstructed entry of the instruments. Proper knowledge of anatomy and Neuronavigation facility can be useful, especially when landmarks are not visual.  It is critical that the surgeon must survey the anatomy carefully before making any definitive maneuvers.
Site and size of exposure
The smaller exposures tend to be less flexible in endoscopic techniques as compared with larger openings in conventional surgery. It is important that a sufficiently large exposure is made to safely remove the lesion. Site of opening for targeted pathology should be properly planned as there is less flexibility in a small exposure.
Endoscopic blind spot
Although principle advantage of an endoscope is its ability to place light and view sources as close to the area of interest as possible, it also has a dangerous feature of inability to visualize the pathway between the skin and the endoscope tip [Table 1]. This creates the potential for instruments and the endoscope to unknowingly injure important structures on the way. Endoscopic surgeons must consciously train themselves to remove an endoscope with insertion of each new instrument and to follow the instrument into the field under direct endoscopic visualization.  Injuries to structures in between skin and endoscopic tip can also be avoided by direct observation of the instrument until it is seen on the monitor.
Injury to the telescope
Telescope can be injured due to wrong handling or by the drill. Telescope should be protected by the sheath to prevent any injury. Drill should be removed only when it is completely stopped. Telescope should not be lifted by holding it from the tip, especially when it is heavy and is connected with a camera.
Although bimanual techniques are superior to one hand dissection, it may not be possible in some of the endoscopic procedures. Bimanual dissection is not possible when one hand of the surgeon is being used for holding the scope and also because of availability of a single working channel in some procedures. Use of telescope holder allows the surgeon to employ both hands for dissection. Assistant can also hold the scope permitting surgeon to use both hands for dissection. It also saves a lot of time lost in repositioning of the scope when holder is used.
Avoiding fatigue and improving precision
Some kind of hand support, commonly used in micro-surgery, can be utilized to prevent fatigue and improve precision in endoscopic technique. Gentle support of the hand on the endoscopic sheath or surrounding structures can prevent fatigue and improve precision [Figure 1], where as unsupported hand can give rise to early tiredness. Optimal help of an assistant for opening and closure of the long instruments can also help in improving the precision [Figure 2] and [Figure 3].
Endoscopic neurosurgery is usually associated with a steep learning curve, which improves with the experience. The views are often unfamiliar and the disorientation is easier as compared to the microscopic technique, especially during the transition from the microscopic to the endoscopic surgery. It is important that neurosurgeons begin their use of endoscopy from simple to progressively more complex cases. Multidisciplinary team approach, practice on models, cadaveric dissection and attending live operative workshops can shorten the learning curve.
Proper position of the telescope
Proper placement of the telescope is important, especially in endoscopic controlled surgeries. Telescope can obstruct movement of the instrument [Figure 4]. Slight withdrawal of the scope can permit entry of the instrument [Figure 5]. The scope should be positioned in such a way that it does not obstruct movements of the instruments. The telescope, instrument and the surgical target should not be in a straight line otherwise the surgical object won't be visualized [Figure 6].
Visual obscuration in endoscopic controlled surgery
Visual obscuration in endoscopic controlled surgeries can be due to the presence of blood, bone dust, drop of fluid or brain tissue staining lens tip. Excessive moisture content in the air medium, telescope out of focus and the breakage of lens, etc., can degrade image quality. Lens fogging usually occurs when there is an imbalance between the temperature of the front lens, temperature of the airway cavity and humidity of the environment. Anti-fogging agents such as baby shampoo, savlon and povidone iodine scrub are very effective. Lens tip can also be cleaned by using commercially available lens cleaner.
The telescope can be cleaned by manual irrigation using saline and removal of drop off liquid from lens tip by suction. Image quality can be improved by treatment of the causative factors such as suction of air containing excessive humidity and proper focusing etc. Proper positioning of the lens can improve visualization and can allow unobstructed execution of the surgery. Telescope should be parallel to the operative corridor.
Operative time can be prolonged due to bone dust frequently staining the telescope tip when drilling is required. Image quality frequently gets poor because the lens tip, which is closer to the drilling site, frequently gets stained due to irrigation fluid or bone dust. This problem can be partly avoided by using comparatively larger sized telescope, with longer focal length, which permits lens tip to be placed away from the drilling site. This problem can also be managed by using intermittent irrigation in between the short period of drilling. Lower revolutions per min can be used to reduce staining during the drilling.
Sometime unwanted tissue comes in front of the telescope lens obscuring visualization of the neighboring desired structures, slight withdrawal of scope away from the obstructive tissue [Figure 7] or the repositioning of scope can solve this problem. Obstructing tissue can be retracted or removed if indicated.
Some of the intraoperative complications are discussed below.
Hypothermia during neuroendoscopy is seen more often in small children, caused by large exchanges of irrigation fluid and ventricular cerebro-spinal fluid (CSF) and wetting of drapes by the returning fluid. Hypothalamic injury may contribute to impaired temperature regulation. Routine use of pre-warmed irrigation fluid and blankets can help in reducing intraoperative hypothermia. , Wetting of drapes should be avoided by using drainage line connected to outflow channel. Hypothalamic injury should be avoided.
Intra- ventricular bleeding
Intra-ventricular bleeding can occur from the ependymal margin of lateral ventricle. Attempts to perforate the ventricular floor can lead to bleeding especially in hydrocephalus following infection and hemorrhage. Intra-ventricular bleeding can be caused by excessive side movements, removing flexible scope in curved tip position, wrong entry in the lateral ventricle, injuries due to repeated introduction of endoscope without the use of the peel-away sheath or other sheath, direct ventricular access by the telescope and use of sharp edged sheath etc. Rarely blood might trickle from the burr-hole site into the ventricle. Proper hemostasis must be achieved before entering the ventricle. Flexible scope should be removed in a neutral position. If scope needs to be removed and reintroduced, it is wise to use peel-away sheath or other sheath in order to maintain tract without injury to the surrounding structures. Sheaths with a sharp edge should be avoided as it may tear vessel. If there is the wrong site of entry into the lateral ventricle, one should not move the scope too much to gain entry into the foramen of Monro. It is better to re-enter at a correct site. In opaque floor, it is wise to be as anterior as possible but posterior to the infundibular recess and the dorsum sellae. Intraoperative bleeding should be avoided by using a waterjet dissection in thick and opaque third ventricle floor,  avoiding stretching of the third ventricle especially during perforation of tough third ventricle. Significant side movement should also be avoided to prevent bleeding due to injuries to the fornix and the veins at foramen of Monro. Proper inspection is necessary before making perforation in the third ventricle floor to avoid injury to the vessels. 
Basilar artery or its branch may get damaged during the perforation of the third ventricle floor or at the time of the dilatation of the stoma. There may be injury when closed end of the ventriculostomy forceps is opened. This injury can be prevented by partially retracting forceps into the third ventricle before it is fully opened. Similarly pulling the inflated balloon may tear a vessel. Knowledge of the position of basilar artery and its branches and perforation of the floor anterior to these vessels help in avoiding injury. The most fatal complication of basilar artery and its branch can be avoided by correct site of fenestration in the midline. The floor should be perforated with blunt probe to prevent injury to the basilar artery.  If 30°endoscope is used to perforate the floor, the sloping face should be looking posteriorly to push basilar artery backward.
Small hemorrhages during the procedures are usually venous in origin. Bleeding at the margins of the ventriculostomy ceases spontaneously with or without irrigation. In general, copious irrigation with warm lactated Ringer's solution can control most bleeding. The hemorrhage at the site of fenestration in the floor of the third ventricle can be stopped by inflating the balloon catheter or gently keeping any instrument on the bleeding point. If a bleeding site can be identified, cauterization may be attempted. Intermittent careful closure of outflow can also produce tamponade effect.
Maintaining ventricular access is important in severe bleeding. In such cases, the scope must be maintained within the field, rather than pulling it back. The telescope should be placed in large size ventricle cavity (lateral ventricle rather than third ventricle) as any movement in the smaller ventricle could be dangerous when there is no vision. Endoscope may be removed, but the sheath should be in place. It may take long to stop hemorrhage; once bleeding is stopped, sheath can be removed after evacuation of intra-ventricular blood. In case of residual oozing, a ventricular drain is recommended. Forceful irrigation may allow visualization of an appropriate site for bipolar coagulation. As a last resort to control bleeding, fluid can be replaced by air and coagulation of the bleeding point can be done. One must remember to replace fluid with air otherwise ventricle would collapse with even worse consequences. Rapid conversion to open surgery is recommended when significant bleeding is not controlled by any other technique.
Entrapment of air at the time of surgery can interfere with direct visualization of the anatomic landmarks that are essential for performing a third ventriculostomy safely. Excessive loss of CSF, wrong site of burr-hole and use of nitrousoxide anesthesia can predispose to the development of pneumocephalus. This can be avoided by keeping the head in midline, performing the burr-hole at the most superior point, carefully flushing out of the air bubbles from the irrigation lines, minimizing CSF loss especially in the early stages of the procedure and avoiding the use of nitrous oxide.
Raised intra cranial pressure (ICP) is due to the blockage of out flow channel, too cold irrigation fluid of different osmolarity as compared with plasma, forceful and rapid rate of irrigation, balloon inflation causing local pressures on the underlying hypothalamus, use of saline as an irrigation solution and traction on the third ventricle wall etc., can produce bradycardia. The scope may block both the foramina obstructing escape of fluid giving rise to raised pressure. One should check that the outflow is open and the fluid is coming out from the outflow. Open outflow does not guarantee egress of fluid as blood or brain tissue can obstruct the outflow. Turn up the volume of the cardiac monitor and keep the noise down in the theatre to detect bradycardia in time. Reverse the last action when there is any bradycardia or asystole. Use of isotonic irrigation solution at body temperature and perforation of tough third ventricle floor by sharp instruments can avoid bradycardia. Normal saline should be avoided.  Cardiac arrests, though rare, have been reported during ETV. Judicious use of irrigation at a speed of ≤10 ml/min and avoiding local pressures on the underlying hypothalamus can prevent this complication.
There are several causes of poor vision during surgery such as incorrect system assembly, damaged lenses, fogging of the lenses, blood or brain material staining the lens tip, intra-ventricular bleeding and scope out of focus etc., Initially nothing may be seen in some patients when telescope is entered in the large lateral ventricle, careful introduction of the scope allows visualizations of structures when these structures come within the focal length range of the endoscope. Identification of the proper cause and appropriate corrective method improves visualization.
It is one of the most common complications of ETV and intra-ventricular endoscopy. It can be caused by the tip of the endoscope when burr-hole is placed too laterally or from the side of the scope when it is moved. Bilateral damage may occur when contralateral ventricle is entered and the surgeon tries to enter foramen of Monro. Injury can occur when flexible scope is removed in curved tip position. Small foramen of Monro can predispose to forniceal injury. It could be small even in a disproportionately large lateral ventricle. Injury can be prevented by avoiding ventricular tap by the scope or large diameter sheath directly. These larger diameter sheaths can injure both the fornix if it is not well-directed. Brain penetration should not exceed 5-6 cm from burr-hole and the direction of the sheath should be same as that of brain needle. If there is an entry into the contralateral ventricle, it is better to abandon that trajectory, remove the scope and re-enter at proper side. Forniceal injury and other neural injuries can be avoided by proper planning of burr-hole, avoiding significant side movements and selecting proper cases with significantly enlarged foramen of Monro and third ventricle.  Use of small size scope, enlargement of foramen of Monro by hydrodissection, shrinkage of choroid plexus at the foramen by bipolar coagulation can solve this problem. Rarely sheath of the telescope can be removed and the scope can be used directly. Flexible scope should be in the neutral position at the time of removal to avoid injury.
This is also a common complication of ETV. Temporary or permanent diabetes insipidus, amenorrhea, loss of thirst, death, hyperphagia, varying degree of drowsiness, hyperkalemia and hypernatremia can occur after ETV. It is difficult to ascertain safe site of perforation in acute hydrocephalus because the floor may not get the opportunity to become transparent. Making burr-hole more laterally can penetrate contralateral floor. Although blunt technique is better to avoid vascular damage, it may cause excessive traction on the hypothalamus in thick third ventricular floor. Sharp perforation may be appropriate in such settings. The closed end of the pointed grasping forceps may help in making perforation. Perforation in the midline, between infundibular recess and mammillary body, can avoid hypothalamic damage.
Cranial nerve damage
Oculomotor and abducens nerve can be injured when floor is bulging downward and the perforation is not made in the midline. Cranial nerve injuries can also occur if the perforating instruments are introduced blindly far below the floor. Nerve injuries can be caused by vigorously pushing an already stretched floor. Abnormal anatomy of the third nerve too close to the midline can pre-dispose to injury. Burr-hole should be placed as medially as possible and the perforations should be made in the midline. Instruments should not be pushed blindly below the floor especially away from the midline. Abnormal anatomy should be appreciated and the tough membrane should be perforated using sharp instruments.
It may be difficult to perform ETV when there is less space between the basilar artery and the dorsum sellae. Upward herniation of the basilar artery and its perforators in the floor of the third ventricle can also produce technical difficulties.  Crowding of the neural elements in the posterior fossa, unusually small foramen of Monro, a large interthalamic adhesion and thick third ventricle floor increases risk of failed ETV. Proper pre-operative knowledge of the above structures and careful case selection can reduce the risk of failed ETV.
Inappropriate movement of the endoscope
One of the limitations of the endoscopic surgery is that the area proximal to the telescope is not seen at all. It is not advisable to move endoscope to any side when it has passed through a narrow vital structure such as fornix.
Post-operative complications of the ETV and their management can be classified into early and late.
Early post-operative complications
Infections, fever, blocked stoma, CSF leak delayed awakening and post-operative intracranial hematomas can be seen in early post-operative period. Mortality, diabetes insipidus, weight gain, precocious puberty, hyperkalemia, severe Parkinsonism More Details, acute respiratory alkalosis, tachypnea and abnormal prolactin levels are also reported after ETV.
It is important to have a reasonably awake patient at the end of anesthesia to facilitate early neurological assessment. General anesthesia incorporating easily titratable drugs such as propofol, thiopentone, fentanyl, atracurium and inhalational agents should be preferred over long acting drugs as the procedure may end abruptly. Delayed awakening after neuroendoscopy can be attributed largely to raised ICP , and hypothermia. , Long acting anesthesia drugs, factors responsible for hypothermia and raised ICP should be avoided.
The stoma can be blocked after ETV.  The mechanism of ETV failure is likely to be multifactorial; inadequate size of the stoma, presence of unappreciated secondary membranes, impaired flow through the stoma and hemorrhagic obstruction facilitating closure or narrowing of the stoma etc., Elevated CSF protein, impaired CSF absorption by the arachnoid granulations, and tumor progression resulting in blockage of the stoma can also cause ETV failure. Rarely bone dust can migrate into the third ventricle and block the ventriculostomy stoma. Bone dust for sealing of the burr-holes should be avoided. Such particles, if detected during the procedure, should be removed. 
Although most of the blocked stoma complications in ETV patients occur in early post-operative period, delayed block; though very rare can be fatal.  Longer follow-up is desirable especially in patients who undergo ETV for infective hydrocephalus and Dandy-Walker malformation because late closure of the stoma may occur in these patients. Intraoperative observation of thickened arachnoid membranes at the level of the interpeduncular cisterns and a progressive decrease in CSF flow through the stoma on cine magnetic resonance imaging should be considered as significant risks for blocked stoma. , Blocked stoma can be avoided by making comparatively larger opening (5 mm or more), perforation of membrane lying bellow the third ventricle floor and proper case selection by avoiding ETV in post-hemorrhagic and infective pathologies. Blocked stoma can be managed by repeat ETV or shunt surgery.
Subdural hematoma can develop after faster drainage of a large quantity of CSF from the ventricles. It can also develop due to separation of brain from the duramatter during the introduction of scope for ventricular access without using brain cannula. Extradural or dural bleeding can trickle in the subdural space. Subdural hematoma can be avoided by preventing rapid drainage of large quantities of CSF. Lost CSF should be replaced with lactated Ringer's solution in ETV to prevent brain collapse. The shunt should be removed or ligated following ETV to prevent over drainage. Adequate size of cortical incision for the introduction o f the scope should be made to avoid separation of brain away from dura. Brain needle should be used rather than direct puncturing of the cortex by the scope to prevent brain separation and subdural hematoma formation. All bleeding points should be controlled before opening the duramater.
It could be due to injury to cortical vessels by large size of the scope, used for entering into the ventricle directly, without the use of brain needle. Intra-cerebral hemorrhage can be caused by drainage of a large amount of CSF from the ventricle. Reducing the amount of CSF released, refilling of the ventricle and plugging of the cortical margins can prevent hemorrhage. Control of bleeding from the tract by bipolar coagulation can prevent this complication. One should avoid the use of scope to find the ventricle.
CSF leak after ETV can be due to raised ICP, which may stop spontaneously after sometime or may persist for a longtime. Raised ICP , large dural or cortical opening and thin cortical mantle etc., can be responsible for the leak. Raised ICP after ETV can be due to blocked stoma or secondary to complex hydrocephalus (combination of communicating and obstructive type).  Proper management of raised ICP, small dural opening, and plugging of the cortical margin by Abgel can avoid CSF leak. Dural repair in large ventriculomegaly especially in infants can reduce chances of CSF leak.  Post-operative CSF leak can also be reduced by galeal-pericranial flap. ,
Chronic subdural hematoma or subdural hygroma, death and delayed blocked stoma can occur after ETV.
Chronic subdural hematoma or subdural hygroma
Subdural hygroma can develop due to CSF passing through the least resistant tract in the subdural space. It can also be secondary to faulty CSF absorption. Defective absorption could be temporary or permanent. Subdural hygroma can develop after the use of Ommaya reservoir in ETV.  Persistent effusion may need some kind of shunting. Subdural hematoma can develop secondary to collapse of the ventricle due to egress of a large amount of CSF. Ventricle should be expanded before removing the sheath and the cortical margin should be plugged.
Biopsy and ETV can be done by single or two burr-hole approaches. Both ETV and tumor biopsy can be done using single burr-hole, especially when foramen of Monro is enlarged. Position of the burr-hole should be slightly more anterior than the traditional ETV site to allow both the ETV and the tumor biopsy procedures. Working channel should be placed anteriorly for ETV, whereas it should be directed posteriorly for the biopsy. Endoscopic intra-ventricular biopsy is best suited for intra-ventricular tumors or periventricular lesions projecting in the ventricle. Biopsies are generally performed with cupped biopsy forceps, which should be rotated, to free the biopsy sample, after holding the tissue. Complete resection is more likely in small intra-ventricular tumors that are highly friable, low grade and less vascular. When attempting resection, generous coagulation of the tumor is desirable. Parenchymal tumors that do not extend through the ependymal surface are generally associated with a higher rate of hemorrhage.
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]