Neuroendoscopic interventions using an Nd-YAG laser for multilevel hydrocephalus: treatment results for 10 patients

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Introduction. Treatment or multilevel hydrocephalus is a complex problem. Neuroendoscopic interventions, make it possible to combine minimal invasiveness with the possibility of fenestration of several cysts during one procedure and thereby eliminate multi-level occlusion. We present our the experience of using a neodymium YAG laser (Nd-YAG laser) as an additional tool to improve the treatment results of patients with non-communicating hydrocephalus. Materials and methods. This study included 10 patients aged from 5 months to 8 years who underwent endoscopic interventions with the use of rigid endoscope with frameless navigation. A surgical laser with a radiation wavelength of 1.064 μm was used as the main tool for fenestrating the walls of the cysts. Results. 13 endoscopic laser interventions were performed in 10 patients with multilevel hydrocephalus. In 3 children, the two-stage treatment was chosen in due to the impossibility of simultaneous fenestration of all cysts. The interval between procedures was 1 month in two cases and 11 months in one case. We managed to compensate for cerebrospinal fluid disturbances in each patient, positive dynamics in the condition was noted. The duration of postoperative stay averaged 8 days (from 4 to 13 days). There were no deaths in the study group. All patients were discharged in good condition. Average follow-up duration was 14 months (from 8 to 25 months). During the observation, the condition of the patients remained stable; there was no need for repeated operations. Conclusion. Combined use of bypass operations, endoscopic techniques and neural navigation may improve the results of treatment of patients with multilevel hydrocephalus. Data presented in this article demonstrates the safety and effectiveness of the clinical use of laser radiation as an additional tool for interventions in patients with this condition.

Keywords:

multilevel hydrocephalus

endoscopy

navigation

Nd-YAG laser

Authors:

Kim S.A.

Federal Neurosurgical Center, Novosibirsk, Russia

Letyagin G.V.

Federal Neurosurgical Center, Novosibirsk, Russia

Danilin V.E.

Federal Neurosurgical Center, Novosibirsk, Russia

Rzaev D.A.

Federal Neurosurgical Center, Novosibirsk, Russia

SPIN RSCI: 8711-4097
Scopus AuthorID: 57215895381
ORCID: 0000-0002-1209-8960

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Abbreviations

IVH — intraventricular hemorrhage

VPS — ventriculoperitoneal shunt

YAG — yttrium aluminum garnet

CT — computed tomography

MRI — magnetic resonance imaging

NSG — neurosonography

ETVS — endoscopic third ventriculostomy

IR — inversion recovery

PC — phase-contrast

CISS — constructive interference in steady state

Introduction

Successful treatment of multilevel hydrocephalus cannot always be achieved using standard CSF bypass surgery and requires complex application of various surgical techniques. Endoscopic technology significantly surgical effectiveness, ensured minimally invasive dissection of several cysts during the same procedure and correction of multilevel occlusion. However, surgeons sometimes encounter certain difficulties during endoscopic interventions caused by restricted manipulations and technical features of endoscopic instruments. We report our experience of the use of surgical laser as additional tool to improve treatment outcomes in patients with multilevel hydrocephalus.

Objective of the study — to evaluate effectiveness and safety of neodymium YAG-laser (Nd-YAG laser) for endoscopic treatment of multilevel hydrocephalus.

Material and methods

There were 10 patients aged from 5 months to 8 years (mean 25 months) for the period from March 2016 to December 2017. Inclusion criteria: 1) noncommunicating hydrocephalus with the presence of two or more isolated cavities; 2) endoscopic surgery using a surgical laser.

Brain cyst was caused by previous ventriculitis in 9 patients including 5 patients with previous intraventricular hemorrhage (n=5), 2 patients with intrauterine infection and 2 patients with congenital hydrocephalus followed by shunt infection. Genesis of cysts remained unclear in one case. Symptoms of progressive hydrocephalus with intracranial hypertension prevailed in all children at admission. Moreover, focal symptoms caused by cysts, developmental delay and epileptic seizures were observed in some patients.

Standard preoperative examination included analysis of complaints, anamnesis, clinical and neurological survey. We also use standard sequences of MRI and additional MRI programs to evaluate CSF circulation or visualize orifice in the cystic wall (IR, PC, CISS). We usually do not apply contrast-enhanced X-ray examination (CT-ventriculography) because this method does not have any significant advantages over MRI due to lower spatial resolution and insufficient quality of multiplanar imaging [1, 2]. Moreover, this method is undesirable as routine approach in children due to contrast agent injection and irradiation [3, 4].

Endoscopic interventions were performed using a KarlStorz pediatric neuroendoscope with an external diameter of 4.5 mm, inner canal diameter of 1.3 mm and two additional channels for irrigation and aspiration (1mm). Frameless navigation is one of the important factors for successful surgery in patients with multilevel

hydrocephalus [5].

MY60 surgical laser (KLS Martin, Germany) was used as a main tool for dissection of the cystic walls. Irradiation wavelength was 1.064 μm.

Postoperative MRI was performed to evaluate communication between the cysts, their dimensions and position of the catheter. Maximum length and width of the cyst were measured on axial scans before and after surgery. We compared linear dimensions and area of the cyst before and after surgery. Cyst area was calculated using the following formula:

S=3.14 *A/2*B/2, S — cyst area; A — maximum length (cm); B — maximum width (cm).

Reduced dimension of cyst or the absence of growth was one of the criteria of effective surgery. We analyzed brain dislocation and cyst-associated damage to adjacent cerebral structures. Additional MRI programs were valuable to visualize the hole in the cystic wall (CISS) or analyze cerebrospinal fluid flow considering the artifacts from fluid movement within the stoma (IR, PC).

Postoperative follow-up after discharge was carried out through outpatient examinations and correspondence consultation of patients living in faraway regions. MRI was recommended after 3, 6 and 12 months to exclude cyst progression.

Surgical technique

The point of approach was determined to ensure achievement of the maximum number of cysts (Fig. 1).

Fig. 1. Intraoperative images of surgical stages from the navigation station screen. Purple dotted line indicates scheduled trajectory. Green dashed line indicates current position of the endoscope. Crossing of solid green lines corresponds to the tip of the endoscope. a, b — right-sided approach. Endoscope is passed through the right hemispheric cyst, third ventricle cyst and inserted into the left hemispheric cyst; c, d — returning the endoscope to the right hemispheric cyst is followed by change of trajectory, perforation of another cyst on the right and cerebellar cyst.

Exposure of brain ventricle or cyst was followed by introduction of optical fiber into the channel of the endoscope. The tip of the fiber was positioned at the place of further fenestration and laser irradiation was delivered. This process resulted a hole in the membrane due to the effect of evaporation within the contact of the fiber tip with cystic wall (Fig. 2).

Fig. 2. Intraoperative images. a, b — laser perforation of various cystic walls; c —process of laser perforation; d — orifice in the cystic wall after laser perforation.

Laser power was 10W. The time of laser effect was up to 1—2 seconds because longer exposure is associated with the risk of cavitation effect. The hole was enlarged up to the required dimension by angular displacement of the endoscope and fiber. Additional enlargement of the orifice might be achieved by using of balloon catheter or direct introduction of the endoscope tube through the orifice in the cyst wall. Other devices were unnecessary as a rule. Continuous irrigation with warm Ringer's solution was mandatory to prevent intraoperative overheating of intracranial structures [6]. Cyst fenestration was followed by silicone stent deployment within the orifice to prevent recurrent occlusion. This catheter was fixed to the dura mater with a ligature and the wound was sutured.

However, the catheter was connected directly to the valve if this catheter was used as a proximal part of bypass system.

Results

There were 13 endoscopic laser interventions in 10 patients with multilevel hydrocephalus. Mean surgery time was 131 min (range 60—215).

Two-stage surgical strategy was preferred in 3 patients with multiple cysts due to poor accessibility of all cavities through a single approach. Fenestration of the largest and clinically significant cysts was preferred during the first surgery. The second delayed intervention was required if progression of other cysts was confirmed. Interval between both operations was 1 month in 2 cases and 11 months in one patient.

Moderate postoperative hemiparesis was diagnosed in 1 patient. However, complete regression of neurological deficit occurred after 5 days and the child was discharged in preoperative functional state. Most likely, hemiparesis was due to intraoperative mechanical pressure of the endoscope as a result of its angular displacement. Short-term venous bleeding occurred in 1 case that did not significantly increase duration of surgery. However, blood clot got into bypass system caused valve obstruction, Therefore, redo surgery was required after 4 days due to aggravation of hypertension syndrome.

Surgical purpose was achieved in all cases. A total of 42 cysts were fenestrated (3.2 cysts per intervention). Interventions were followed by compensation of CSF circulation disorders and positive clinical changes. Mean length of postoperative hospital-stay was 8 days (range 4—13 days). Mortality was absent in our sample. All patients were discharged in satisfactory condition. Mean follow-up period 14 months (range 8— 25 months). Redo surgery was not required.

Preoperative dimensions of cysts ranged from 11.1x8.6 mm (minimum) to 151.5x55.4 mm (maximum). Postoperative values were 1.0x2.4 and 123.4x51.7 mm, respectively. Mean area of cysts before fenestration was 18,091 cm². This value decreased up to 9.783 cm² after surgery. Patients’ data are shown in Table 1.

Dimensions of cysts prior to surgery and in postoperative period are shown in Fig. 3.

Fig. 3. Dimensions of cysts prior to surgery and in postoperative period. Cysts before fenestration (blue), cysts after intervention (red). Dimensions of the figures are proportional to dimensions of the cysts (area in axial plane is calculated as S=3.14*A/2*B/2).

Clinical observation

A 4-month-old child P. was hospitalized with complaints of increased head circumference and daily vomiting.

It was the 2nd pregnancy followed by childbirth at 33 weeks (emergency cesarean delivery due to premature placental abruption). Child’s condition was serious at birth. Neurosonography revealed bilateral IVH grade III with subsequent hydrocephalus. Left-sided VPB surgery was performed at the age of 1.5 months. Postoperative period was complicated by purulent ventriculitis that required removal of the shunt, bilateral external drainage and systemic antibacterial therapy. Drainage tubes were removed after ventriculitis relief. Increased head circumference and vomiting were observed after discharge. The child was hospitalized in our department. Increased head circumference up to 44 cm and tension of the large fontanel (dimensions 5x5 cm) were observed at admission. Neurological examination revealed converging strabismus, absence of eye tracking reactions, Gref’s symptom and impaired motor activity. There was multilevel occlusal hydrocephalus with multiple tensioned cysts (Fig. 4a, b).

Fig. 4. MRI scans of the patient P. before and after surgery. Explanations in the text.

Endoscopic fenestration of the cysts of the right and left anterior horns of lateral ventricles and fourth ventricle was performed under neuronavigation control at the first stage.

Surgical technique. Left-sided parasagittal approach through the large fontanel was performed in patient's supine position. Head was fixed by pediatric gel holders. Puncture of the cyst of the left lateral ventricle was followed by drainage of slightly turbid cerebrospinal fluid under high pressure. Further manipulations were performed under constant neuronavigation control using NdYAG laser and Fogarty catheter. Successive fenestration of two midline small cysts (within the cistern of corpora quadrigemina) was performed. This procedure ensured an approach to the large cyst of the fourth ventricle. This cyst was characterized by sub- and supratentorial spread. The endoscope was passed back into the cyst of the left lateral ventricle and then trajectory was changed to the right. Fenestration of septum pellucidum and approach to the cyst of anterior horn of the right lateral ventricle were made. Thus, 5 cysts were communicated between each other. The endoscope was removed and dura mater was sutured. The wound was closed. Surgery time was 2 hours and 20 minutes, blood loss — 3 ml.

Ventriculoperitoneal bypass surgery was performed on the 7th day considering no signs of inflammation and cerebrospinal fluid contamination. The child was discharged in satisfactory condition on the 13th day after endoscopic intervention. Positive postoperative changes consisted of general improvement, emotional recovery, eye fixation, increased feeding up to 120 ml. The child began to hold his head. However, apathy, oppression of emotions, converging strabismus, lack of eye tracking reactions, refusal of eating, tension of the fontanel and frequent seizures developed a month later. MRI revealed enlargement of isolated bilateral temporal lobe cysts complicated by compression of adjacent structures and ventricular system deformation (Fig. 4c). Endoscopic fenestration of the cysts of the left frontal lobe, right and left temporal lobes under neuronavigation control and cystoperitoneal bypass surgery were performed.

Surgical technique. Head was fixed by pediatric gel holders in the patient's supine position. Soft tissue incision was made in the left frontal region above the large fontanel. Puncture of the convexital cyst in the left frontal region was followed by drainage of pellucid cerebrospinal fluid under high pressure. Further manipulations were performed under constant neuronavigation control using NdYAG laser and Fogarty catheter. Fenestration of the cyst wall was performed in the lower part. Another small cyst was dissected. Inferior wall was also fenestrated and a large cyst of the left temporal lobe was opened. The endoscope was passed into the cyst. Prolapse of the cyst of posterior cranial fossa was observed in the medial zone within tentorial notch. This wall was also fenestrated, cystic cavity with subtentorial spread was visualized. The endoscope was passed back into the cyst of the left frontal lobe. Trajectory was changed towards the front and down. Fenestration of the wall separating the cyst from anterior horn of the left lateral ventricle was carried out. Ventricular catheter tip perforating septum pellucidum was visualized in the ventricular cavity. The hole in septum pellucidum behind the catheter after previous intervention was visualized. The endoscope was passed to anterior horn of the right lateral ventricle through this orifice. There was a prolapse of the right temporal lobe cyst into this horn. Anterior wall of the cyst was fenestrated and cystic cavity was visualized. Fenestration significantly decreased tension of the cysts and clear pulsation appeared. All cysts were filled with colorless lucid cerebrospinal fluid. A silicone stent with additional lateral orifices was deployed under endoscopic control. The tip of the catheter was inserted into the cyst of posterior cranial fossa, passed through the cyst in the left temporal lobe, convexital cyst of the left frontal region and brought out. The length of intracranial part of catheter was 9 cm. The endoscope was removed. Dura mater suturing was followed by temporary closure of the wound. A 2 cm incision was made in the right parietal area in projection of the valve after turning the head to the left. Junction of the ventricular catheter and the valve was opened. The system was disconnected. Ventricular catheter was removed. Temporary sutures from the wound in the left frontal region were removed. The catheter was passed from the left to the right towards the valve in subcutaneous tunnel. The system was connected and all wounds were sutured. Surgery time was 3 hours and 35 minutes, blood loss — 10 ml.

Regression of hypertension syndrome was noted. The child became more active, emotional reactions and motor activity were improved. Improved appetite resulted feeding augmentation up to 120 ml. The patient was discharged in 6 days after intervention. Follow-up period after discharge was 18 months. Child's condition is still stable. There is developmental delay. No cyst enlargement is confirmed by MRI (Fig. 4 d—f).

Discussion

Loculated or complex hydrocephalus occurs if brain ventricles are divided into separate chambers [7]. Multiloculated or multicompartmental hydrocephalus is distinguished into a special group (two or more isolated cavities are formed due to septa). Intraventricular hemorrhage or previous inflammation are the most common causes of this separation [8].

Treatment of multicompartmental hydrocephalus is a difficult problem and preferable surgical approach is still discussable despite the variety of available technologies. We prefer endoscopic intervention followed by shunt implantation rather microsurgical fenestration or deployment of several proximal catheters and bypass systems. The drawback of bypass surgery is insufficient effectiveness and high incidence of redo surgery [5]. Dysfunction of the catheter may be caused by its displacement, development of scar tissues or obstruction by the walls of collapsed cyst. Moreover, the use of multiple catheters or bypass systems also complicates the situation.

Frameless navigation is one of important auxiliary methods to increase surgical effectiveness and safety considering severe violation of ventricular anatomy. This technique significantly facilitates intraoperative searching for a target for fenestration in the absence of natural landmarks [9, 10].

The following instruments are usually used for fenestration: microscissors, forceps, balloon catheters, monopolar cautery, tip of the catheter and leukotome [11—13]. However, endoscopic dissection of the cyst wall per se may be associated with certain difficulties. Therefore, we regularly use surgical Nd-YAG laser in the treatment of these patients.

Laser techniques in neurosurgery is mainly used for resection of brain tumors [14]. Moreover, lasers are applied in surgery for epilepsy, resection of spinal cord lipomas. Surgical lasers are also valuable in neuroendoscopic interventions: ETVS, cyst fenestration, coagulation of the vascular plexus, tumor biopsy. Neodymium (Nd-YAG), argon and diode lasers are the most common in neurosurgery [15, 16, 17]. CO2 laser is not used in neuroendoscopy due to high absorption in water. Contact method is preferable for neodymium laser since non-contact approach is associated with absorption of irradiation energy by liquid component, wide scattering and possible damage to surrounding tissues [18]. Contact ablation mechanism is determined by carbonization followed by effective heat absorption and vaporization that ultimately leads to tissue evaporation [19, 20].

Laser is advisable for fenestration of multiple intraventricular cysts due to several factors. For example, significant advantage of laser irradiation is no need to pierce the membrane that is required for standard neuroendoscopic instruments [21]. Septum stretching under mechanical pressure, membrane rupture and subsequent uncontrolled penetration of a sharp instrument significantly increase the risk of injury of brain structures behind the cyst [22, 23]. In these cases, local vaporization and balloon dilatation of the orifice ensure better surgical control. This advantage is also described for ETVS because blunt perforation of dense bottom of the third ventricle may require excessive tension with the risk of hypothalamic disorders [16]. Perforation of dense membranes (for example, after previous surgery) is also advantage of laser irradiation.

Another advantage of laser irradiation is dissection of the membranes under various angles of endoscope when the forceps or scissors slide off the walls of the cyst. Surely, the majority of neurosurgeons have ever encountered a situation when the sharp tips of the scissors slide the membrane over and over during endoscopic interventions. However, instruments only displace the membrane and leave no traces on its surface. Endoscope displacement can solve this problem if it is possible through used approach. Laser ensures cyst wall fenestration even from this position that is inconvenient for standard tools.

Cautery effect of laser irradiation is clearly visible in mild capillary bleeding. However, laser should be used with caution near major vessels because burning of the vascular wall can result severe bleeding.

Another characteristic feature of this technique is the absence of wrinkling effect. Squeezing of the membranes after cautery is often used to shrink and reduce dimensions of the cysts. However, the following deformation of the walls can significantly complicate subsequent orientation in conditions of initially violated anatomy. Laser causes minimal collateral photocoagulation and retraction of the perforation edges [15]. Therefore, an orifice is formed without membrane displacement. In addition to constant irrigation, this ensures preservation of the shape of the cysts and their position throughout the intervention.

Thus, surgical laser is almost universal tool for neuroendoscopy ensuring functions of cutting, perforation and cautery. Therefore, only a single laser may ensure most of these interventions. In this case, there is no intraoperative need to change the instruments (cautery electrode, forceps, scissors, Fogarty catheter) that ensures time saving [16]. Another important factor is reduced wear and damage to neuroendoscopic instruments. Deterioration of optical properties of the fiber tip may be corrected by its cutting for a few millimeters and surgery may be continued. This fiber may be used dozens of times considering its length that decreases cost of treatment [18].

There were no laser-associated complications in our sample. Scheduled surgery was performed with a positive clinical effect in all cases. It is important that obliteration of the holes and recurrent cysts were absent within the follow-up period. Thus, we report safe and effective clinical use of laser irradiation in the treatment of patients with multilevel hydrocephalus.

However, this technology cannot be recommended as a routine procedure in neuroendoscopic interventions despite above-mentioned results. Application of high-energy irradiation is associated with the risk of vital structures injury and should be justified in every clinical situation. Sufficient surgical experience in endoscopic interventions with standard equipment is also essential. This technique may be a good option in experienced hands for the treatment of patients with multilevel hydrocephalus.

Conclusion

Management of patients with multicompartmental hydrocephalus is still difficult problem despite the variety of available treatment options. Wise application of available technologies is essential for successful management of patients. Combination of bypass surgery, endoscopic techniques and neuronavigation improves treatment outcomes. Laser irradiation demonstrates the effectiveness and safety in patients with multilevel hydrocephalus although this method cannot be recommended as a routine procedure.

Authors’ participation:

Concept and design of the study — S.K., G.L., D.R.

Collection and analysis of data — S.K., V.D.

Statistical analysis — V.D.

Writing the text — S.K.

Editing — G.L., D.R.

The authors declare no conflicts of interest.

Commentary

The research is relevant and performed at a good methodological level. In my opinion, the authors’ data on the use of endoscopic laser dissection of the brain membranes are valuable to clarify the algorithms for application of this method in the diagnosis and treatment of complicated hydrocephalus. It should be noted that treatment of occlusive hydrocephalus also depends on the intensity of cerebrospinal fluid absorption. This moment should be discussed in more detail in discussion chapter. Analysis of the characteristics of cerebrospinal fluid absorption after restoration of ventriculo-subarachnoid communication would be very interesting. However, these comments do not reduce the value and significance of this report for neurosurgeons and other specialists.

V.A. Khachatryan (St. Petersburg, Russia)