Endoscopic Approach for Colloid Cyst Resection

This protocol details a minimally invasive endoscopic technique for the removal of third ventricular colloid cysts. It provides a comprehensive overview of preoperative preparations, surgical steps, and postoperative outcomes, emphasizing reduced recovery time, minimal complications, and total cyst removal. This approach is a safe and effective alternative to traditional microsurgery.

This protocol describes a minimally invasive endoscopic technique for the removal of colloid cysts located in the third ventricle. These cysts are a rare type of intracranial lesion that can obstruct cerebrospinal fluid flow. If left untreated, they may cause hydrocephalus or, in severe cases, even sudden death. The objective of this approach is to provide a safe and effective alternative to traditional microsurgical methods. It does so by reducing postoperative pain, surgical morbidity, and hospital stays. The protocol delineates meticulous preoperative preparations, encompassing patient positioning and equipment setup, followed by a systematic step-by-step guide to the endoscopic surgical procedure. This protocol involves the use of intraoperative ultrasound guidance for precise navigation, incision of the cyst wall, aspiration of cyst contents, and meticulous hemostasis. Special care is taken to minimize damage to surrounding neural structures, ensuring complete cyst removal while reducing the risk of complications. The efficacy of this minimally invasive approach is substantiated by the observation that it is associated with reduced operation times, minimal neurological deficits, and rapid postoperative recovery. Typically, patients are able to resume mobilization the day after surgery and are discharged within two days. This protocol serves as a comprehensive guide for neurosurgeons aiming to enhance surgical precision while maximizing patient outcomes. The successful utilization of this protocol is dependent on meticulous preoperative planning, advanced intraoperative navigation techniques, and the employment of specialized endoscopic instruments.

Colloid cysts of the third ventricle are rare intracranial lesions, constituting about 0.5%-2% of all intracranial tumors^1,2,3. Their estimated occurrence is around 3.2 cases per million people annually⁴. The cyst is lined by simple epithelium, squamous epithelium, or stratified ciliated columnar cuboidal⁵. Colloid cysts originate from the roof of the third ventricle, near the foramen of Monro. They frequently block the flow of cerebrospinal fluid (CSF), which can lead to hydrocephalus and, in some instances, may cause sudden death^2,6.

Most colloid cysts are discovered incidentally during brain imaging performed for unrelated reasons². When symptomatic, they often cause non-communicating hydrocephalus, leading to symptoms such as headaches, nausea, vomiting, lethargy, and in severe cases, coma or sudden death¹. In cases where hydrocephalus progresses slowly, patients might experience more subtle symptoms such as difficulty walking, frequent falls, changes in mental status, memory problems, and urinary incontinence⁷.

The optimal management of colloid cysts remains a subject of debate, and there is no consensus on the optimal surgical technique. Various treatment approaches have been explored, including microsurgical resection, endoscopic resection, endoscopic-assisted microscopic resection, stereotactic aspiration, and the placement of ventriculoperitoneal (VP) shunts^8,9. Each method has its advantages and limitations in terms of safety, effectiveness, and recovery time.

In recent years, minimally invasive endoscopic removal has gained popularity due to its advantages of reduced postoperative pain, lower surgical morbidity, and shorter hospital stays compared to traditional surgical methods. This technique enables precise cyst removal with minimal disruption to surrounding neural structures, making it an appealing option for neurosurgeons¹⁰.

This study outlines a detailed protocol for the endoscopic resection of third ventricular colloid cysts, emphasizing its safety, efficacy, and postoperative outcomes. By providing a comprehensive step-by-step guide, this protocol aims to enhance surgical precision and improve patient recovery.

The Institutional Review Board of Istanbul University, Istanbul Faculty of Medicine approved the study. The patients gave written consent prior to the surgical procedure.

1. Preoperative procedure

1. Use the following criteria to select patients: Individuals presenting colloid cysts that lead to hydrocephalus, either symptomatic or asymptomatic, obstructive hydrocephalus, or intermittent clinical manifestations such as headaches; patients with cysts located in proximity to critical neuroanatomical structures. Exclude patients who do not align with the criteria.
2. Perform the procedure under general anesthesia to ensure the patient is unconscious and fully relaxed during the surgery. Ensure the necessary endoscopic and optical instruments are prepared in the operating theater, ensuring that all equipment, including the 25° angled endoscope, working channels, light conductor system, and surgical tools, are sterile and ready for use prior to the procedure.
3. Ensure that the following tools are available for the procedure: endoscope with a 25° angled endoscope (outer diameter of 5.9 mm), a working channel (outer diameter of 6.9 mm), the optical lens system, a light conductor system, and a channel for continuous irrigation. Forceps, scissors, dissectors, and bipolar are introduced from the working channel.

2. Surgical procedure

1. Position the patient and prepare the surgical field as described below.
   1. Place the patient in a supine position with a soft head support to position the patient's head in 10° flexion.
   2. Identify the coronal suture through palpation of the skull. By gently palpating the patient's scalp, locate the suture at the junction of the frontal and parietal bones.Shave and disinfect the right frontal area using iodine or 10% chlorhexidine, covering an area 4 cm lateral to the midline and 5 cm anterior to the coronal suture.
   3. Place a waterproof surgical drape over the operative field to maintain a sterile environment.
2. Perform endoscopy as described below.
   1. Set the 20° rigid endoscope system and manually adjust the endoscope screens according to the surgeon's preferred position. Adjust white balancing and camera focus settings.
   2. Make a 4 cm curvilinear incision centered at the 4 cm lateral to the midline and 5 cm anterior to the coronal suture and in the right frontal area using a #20 scalpel.
   3. Utilize bipolar cautery to achieve hemostasis and perform dissection of the skin and subcutaneous tissue.
   4. Insert automated skin retractor. Use an Adson periosteal elevator to scrape the periosteum.
   5. Use a high-speed perforator to create a 14 mm burr hole slightly lateral to the Kocher point. Expand the burr-hole towards the medial side with Kerrison rongeur as much as the trocar introducer and burr-hole probe of ultrasound can fit. Periodically apply saline to the burr hole using a syringe to improve imaging clarity.
   6. Carefully remove the thin bone layer over the dura with a dissector. Utilize an intraoperative ultrasound puncture probe to visualize the lateral ventricles, the Foramen of Monro, and the third ventricle.
   7. Make a cross-shaped incision in the dura using a #11 scalpel. Coagulate the pia mater underneath using bipolar cautery. Establish the trajectory from the Foramen of Monro to the floor of the third ventricle using intraoperative ultrasound for guidance. Carefully visualize the anatomical landmarks and plan the path to ensure accurate and safe navigation.
   8. Attach the intraoperative ultrasound puncture probe to the endoscope's trocar introducer. Under intraoperative ultrasound guidance, insert the endoscope trocar introducer into the brain tissue. Observe cerebrospinal fluid exiting the endoscope sheath as it enters the lateral ventricle.
   9. While stabilizing the endoscope sheath, remove both the trocar introducer and the intraoperative ultrasound puncture probe. Insert the endoscope into the sheath of the endoscope sheath.
   10. Inside the lateral ventricle, identify key structures such as the lateral ventricular cavity, Foramen of Monro, choroid plexus, thalamostriate vein, and septal vein.
   11. Under direct visualization, visualize the colloid cyst and approach it through the foramen of Monro. Incise the cyst wall carefully and aspirate the contents using an 8F pediatric suction cannula.
       NOTE: Before excising the cyst wall, it is advised to aspirate the cyst contents. Failing to do so could lead to cyst rupture, which may impair vision and result in incomplete removal of the cyst wall.
   12. After aspirating cyst contents, coagulate components of the cyst. Grasp cyst wall firmly with small forceps and rotational movements. Control bleeding by coagulation and irrigation.
       NOTE: If there is concern about insufficient hemostasis, a ventricular catheter may be inserted.
   13. Complete the surgery by removing the endoscopic system after hemostasis in the operation area.

This study describes the successful application of a minimally invasive endoscopic approach for the treatment of colloid cysts in a 20-year-old female patient with no known comorbidities (Figure 1 and Figure 2). The procedure lasted approximately 60 min. No drainage was necessary. No hematoma formation was observed. No neurological deficits were observed postoperatively. The patient was mobilized the day after surgery and discharged 2 days following the procedure. Follow-up evaluations at 6 months and 1 year showed no signs of recurrence or complications.

Retrospective data from 21 patients treated between 2008 and 2019 at Istanbul University's Faculty of Medicine demonstrate the safety and efficacy of this full-endoscopic technique⁹. These patients were primarily treated for hydrocephalus or headaches associated with intermittent obstruction of the foramen of Monro. In the last five years, approximately 10 additional patients have been treated using this method, further confirming its effectiveness and reliability.

The outcomes from these surgeries highlight the advantages of the endoscopic technique, including shorter surgery duration, reduced postoperative pain, and minimal hospital stay. The absence of complications such as hematoma or neurological deficits suggests that this approach provides a safer alternative to traditional microsurgery. Regular postoperative imaging is recommended to ensure complete cyst resection and monitor for potential recurrence.

Figure 1: Preoperative and postoperative MRI images of the colloid cyst. (A-C) Preoperative MRI images illustrating the colloid cyst's relationship with adjacent structures (A) Axial T2-weighted image, (B) Coronal T2-weighted image, (C) Sagittal contrast-enhanced image. (D-F) Postoperative MRI images following colloid cyst resection, demonstrating changes after surgery (D) Axial T2-weighted image, (E) Coronal T2-weighted image, (F) Sagittal contrast-enhanced image. Please click here to view a larger version of this figure.

Figure 2: Endoscopic surgical images. (A) Appearance of the colloid cyst during the procedure. (B) Reduction in the size of the cyst following bipolar coagulation. Please click here to view a larger version of this figure.

Table 1: Comparison of endoscopic resection and microsurgical resection approaches.

Endoscopic intraventricular surgery has undergone remarkable advancements over the past century, driven by both technological progress and clinical experience. The technique's roots date back to the early 20th century, when Walter Dandy pioneered neuroendoscopy in 1922¹¹, utilizing an endoscope to address hydrocephalus. In 1923, William Mixter further advanced the field by performing the first endoscopic third ventriculostomy (ETV), marking a significant milestone in its development¹². Challenges such as poor visualization and high complication rates hindered widespread adoption of early attempts at ETV. In the late 20th and early 21st century, significant improvements in endoscopy, imaging, and surgical techniques have resulted in increased safety and efficacy. This led to a resurgence in the use of ETV and endoscopic intraventricular surgery¹³.

The endoscopic treatment of colloid cysts was first introduced in 1983 when Paul et al. successfully performed endoscopic aspiration of a colloid cyst¹⁴. With advancements in endoscopic technology and the growing expertise of neurosurgeons in this field, endoscopic resection has become the preferred surgical method. The initial comparison between endoscopic surgery and transcallosal microsurgery was conducted by Lewis et al. in 1994. Their study demonstrated that endoscopic surgery was associated with shorter operation durations, reduced hospital stays and rehabilitation periods, as well as lower complication rates¹⁵.

Improvements in the optical systems and light intensity of rigid endoscopes have led to much more rigid endoscopic instruments, surpassing those of flexible endoscopes. Slight adjustments in trajectory or even an angled binocular when using a rigid endoscope can potentially damage the cortex and may not offer the same level of maneuverability and visualization as a flexible endoscope during cyst resection. Flexible endoscopic resection, on the other hand, can be effectively performed using coagulation, aspiration, and flexible grip forceps and scissors^16,17.

Sheikh et al. conducted a review of 40 studies involving 1,278 patients who underwent either microsurgical or endoscopic resection of third ventricular colloid cysts between 1990 and 2014. Their findings revealed that the microsurgical resection group had a significantly higher rate of gross total resection, along with lower recurrence and reoperation rates compared to the endoscopic resection group. All studies included in the review reported a higher rate of gross total resection and fewer instances of recurrence and reoperation with the microsurgical approach than with the endoscopic method¹⁸.

Although minimally invasive, the endoscopic approach is not without its limitations. The most significant challenge is the risk of incomplete resection, particularly in cases where cysts are large or tightly adhered to surrounding tissues. In such cases, the endoscopic technique might not provide adequate exposure, resulting in residual cyst material and subsequent recurrence. Moreover, the procedure is highly reliant on the surgeon's technical skill, as any mishandling of the delicate instruments can result in damage to adjacent structures, leading to complications such as hydrocephalus or memory impairment. Additionally, there is always the potential for bleeding from vascular structures that are in close proximity to the cyst. Although these risks can be minimized through careful preoperative planning and advanced intraoperative navigation, they remain a limitation of the technique^3,9,19,20.

Endoscopic resection of colloid cysts, although minimally invasive, is associated with certain risks. Incomplete removal of the cyst is a notable complication, often resulting from difficulty in extracting dense or adherent material. This can lead to recurrence, making regular postoperative imaging essential to detect any residual cyst material. Injuries to critical structures near the cyst, such as the Foramen of Monro, fornix, or adjacent neural tissue, may result in complications like memory impairment or hydrocephalus. These risks can be minimized with thorough preoperative planning and the use of advanced intraoperative navigation techniques, such as ultrasound or neuronavigation. Long-term follow-up, including serial imaging, is necessary to detect potential recurrence and assess the overall success of the procedure. Regular imaging in the months following surgery is vital to monitor the cyst's status and prevent future complications, ensuring that any residual cyst tissue is promptly identified and managed^3,9,21,22.

Additional complications include bleeding and infection. Bleeding, particularly from vascular structures near the cyst, is typically managed intraoperatively using bipolar cautery, but severe cases may require conversion to a microsurgical approach (Table 1). Infections, though uncommon, can be prevented through strict adherence to sterile techniques and the use of perioperative antibiotics. If an infection does occur, prompt treatment with antibiotics or drainage is necessary. With careful surgical execution, effective use of modern tools, and vigilant postoperative monitoring, these complications can be managed, ensuring positive outcomes for patients^23,24,25. Additionally, patient selection for endoscopic resection is influenced by factors including cyst size, location, and consistency. These parameters must be carefully assessed to ensure that the procedure is performed safely and effectively^5,18,19,26.

Endoscopic techniques have the potential to expand beyond colloid cysts to treat a broader range of intraventricular pathologies, such as other types of cysts or tumors within the brain ventricles. The continued development of advanced imaging techniques, such as intraoperative MRI or augmented reality, could further enhance the precision of endoscopic surgery, particularly in difficult-to-reach areas. Furthermore, the integration of neuronavigation systems with endoscopic technology could improve surgical outcomes, reduce operative time, and minimize complications. As research in neuroendoscopy progresses, it is likely that hybrid approaches will emerge, combining endoscopy with other minimally invasive methods to treat even more complex cases. Continued refinement of surgical instruments, along with enhanced training for neurosurgeons, will further improve the efficiency and safety of this technique.

In conclusion, endoscopic surgery for colloid cysts has become a popular neurosurgical technique due to its minimally invasive nature and positive outcomes. This method offers several benefits, including reduced recovery time, lower complication rates, and precise removal with less disruption to surrounding structures, making it an attractive alternative to microsurgery. The effectiveness of endoscopic procedures depends on factors such as the selection of appropriate patients, meticulous preoperative planning, and the use of advanced intraoperative technologies^9,18.

The authors declare that there are no conflicts of interest related to the materials or methods used in this study.

There is no funding source for this study.