Abstract

Background: Colloid cysts have always provoked the interest of neurosurgeons due to their benign histology, wide variety of clinical presentations, and differences in reported surgical outcomes. Although recent studies have reported favorable outcomes with different surgical resection approaches, the transcallosal approach remains the most popular approach to date. In this series, we report the clinical and radiological outcomes of the transcallosal approach for the resection of third ventricle colloid cysts in 12 patients.

Methods: We present a case series of 12 patients who were radiologically diagnosed with a third ventricle colloid cyst who underwent transcallosal resection by a single surgeon in one center over a 6-year period. Clinical, radiological, and surgical data were collected, and surgical outcomes and complications were analyzed.

Results: Of the 12 patients diagnosed with colloid cysts, 10 (83%) presented with headache, and five (41%) presented with memory disturbance. All 12 patients showed improvement or resolution of their symptoms following resection. Nine patients (75%) presented with hydrocephalus on radiology. All the patients required preoperative or intraoperative external ventricular drain insertion. Four patients (33%) experienced transient postoperative complications. None of the patients required long-term cerebrospinal fluids shunting. One (8%) of 12 patients experienced transient memory loss. No mortality was recorded during the follow-up.

Conclusion: Transcallosal resection of colloid cysts has a favorable prognosis. It allows for complete resection of the cyst with minimal transient postoperative complications. Most patients with postoperative complications show complete resolution of symptoms, with no long-term morbidity.

Keywords: Colloid cyst, Microsopic resection, Third ventricle tumor, Transcallosal approach

INTRODUCTION

Colloid cysts are benign lesions that originate from neuroectodermal tissue.[ 20 ] These tumors usually consist of an outer layer of fibrous tissue and an inner epithelium of mucin-producing cells. They account for approximately 2% of all intracranial space-occupying lesions and 15– 20% of all intraventricular lesions.[ 10 ] Patients with colloid cysts are likely to develop obstructive hydrocephalus due to the location of the cyst. These cysts are almost always located close to the foramen of Monro, in the rostral, midline, and anterior portions of the third ventricle. Thus, it obstructs the flow of cerebrospinal fluid (CSF).[ 1 ] About 60% of colloid cysts identified remain asymptomatic and are found incidentally during the assessment of other neurological problems.[ 10 ] In most cases, surgical resection is the treatment of choice for large symptomatic colloid cysts. However, treatment of small asymptomatic lesions remains controversial.[ 4 ] Both open microsurgery and endoscopic approaches are commonly used. The microsurgical approach includes transcortical, transventricular, or interhemispheric transcallosal approaches. The transcallosal approach has been reported to be used most frequently in recent studies,[ 20 ] with higher gross total resection than the endoscopic approach and lower overall morbidity than the transcortical approach.[ 19 , 20 ] We retrospectively report the clinical and radiological assessment and follow up of 12 patients who have undergone surgical resection of third ventricle colloid cysts using the microscopic interhemispheric transcallosal approach.

MATERIALS AND METHODS

Study design and patient selection

Patients (n = 12) with third ventricle colloid cysts who underwent microscopic interhemispheric transcallosal resection of the colloid cyst between January 2015 and December 2021 by a single surgeon at one institution were enrolled. Patients who were managed by observation and serial follow-up, and those who underwent a different surgical approach were excluded from the study.

Data collection

We conducted a retrospective analysis of all neurosurgical operative records from King Saud University Medical City from January 2015 to December 2021. All medical and surgical records were accessed from the hospital electronic database. Demographic data, clinical presentation, surgical details, preoperative and postoperative neurological status, and radiological studies were collected and analyzed. The diagnosis of colloid cysts in all 12 patients was confirmed by expert histopathologists following surgical resection, and official reports of preoperative imaging and radiological follow-up were written by expert neuroradiologists. Postoperative outcomes were assessed at discharge, follow-up, and by telephone interviews. The mean follow-up period was 3.5 years.

Surgical approach

All surgeries were aided with magnetic resonance neuronavigation. The patient was placed in the supine position and the head was secured with a 3-point Mayfield head clamp and positioned neutrally in the sagittal plane with the neck flexed at 20° [ Figures 1 and 2 ]. The skin incision is made in a horseshoe fashion behind the hairline. The horseshoe incision was one-third behind and two-thirds anterior to the coronal suture and crossed the midline.

Figure 1:

Transcallosal approach to third ventricle colloid cyst resection. (a) Patient is laying supine with head fixed on a Mayfield clamp in neutral position showing the horseshoe incision and the craniotomy site, (b) Separation of the two hemispheres using malleable retractors to expose pericallosal cisterns, (c) Corpus callosum. (d) Pericallosal arteries, (e) Septum cavum, (f) Colloid cyst capsule excision, (g) Colloid cyst capsule attached to the column of the fornix, (h) Surgical field after cyst removal, (i) Insertion of external ventricular drains to clear postoperative debris.

Figure 2:

(a) Axial T1-weighted image with contrast, (b) Coronal T2-weighted image, (c) Sagittal T1 weighted image of a third ventricle colloid cyst in a 22-year-old patient who presented with chronic headache and high ICP symptoms. (d) Axial T1-weighted image with contrast, (e) Coronal T2- weighted imgae, (f) Sagittal T1-weighted magnetic resonance imaging post transcallosal resection of the colloid cyst with resolution of the presenting symptoms.

Neuronavigation was used to facilitate the best position for craniotomy and to protect the parasagittal bridging veins. The bone flap was made by placing four paramedian burr holes 1 cm lateral to the midline on either the right or left side and 2 cm lateral to the midline, exposing the superior sagittal sinus (SSS) to avoid risk of injury. The dura was then dissected from the inner table of the calvarium, taking special care of the exposed sinuses and was opened using a U-shaped flap based on the sagittal sinus. The sinus was pushed laterally to expand the interhemispheric fissure. A few small bridging veins may be sacrificed, but larger ones are preserved. The interhemispheric fissure was then opened and the Pericallosal Cistern dissection continued to deepen the exposure. Gentle retraction is applied using retractors to aid visualization and avoid retraction of the frontal lobe by more than 10–15 mm. After identifying the cingulate gyrus, it was sharply dissected both anteriorly and posteriorly. The ipsilateral callosomarginal artery was traced along the midline to the cingulum level. Pericallosal arteries were identified and carefully separated on each side of the midline avascular plane using the tip of micro-scissors. Furthermore, arachnoid dissection exposes the white corpus callosum. The callosotomy was then created with suction and bipolar cautery under low power in the midline between the paired pericallosal arteries. A fenestration of the septum pellucidum on the side of entry was performed to connect the ventricular systems. The opening was widened using a dissector and suction. Once satisfactory exposure is achieved, coagulation of the choroid plexus is performed to control bleeding. After identifying the capsule and attachment sites of the cyst, it was removed safely. Gross total resection was attempted in all cases where the capsule was completely removed. In a few cases where the capsule was attached to the contralateral fornix, a small part of the capsule was left to prevent neurocognitive deficits. The field was then thoroughly irrigated and hemostasis was achieved. All patients had a ventricular catheter inserted to clear debris that may be seen in the postoperative period which was removed on postoperative day 2. The dura was then closed in a watertight fashion taking care of the SSS, the bone flap was secured, and the galea and skin were closed as routine.

Data analysis

Statistical analysis was performed using Statistical Package for the Social Sciences (SPSS) version 24.0 software (SPSS Inc., Chicago, IL, USA). We calculated the frequencies and percentages of all nominal variables.

RESULTS

Presentation

Twelve patients (aged 11–55 years old) were included in the case series. Seven patients (58%) were females and 5 patients (42%) were males [ Table 1 ]. All 12 patients were symptomatic on diagnosis, with varied symptom durations. Nine patients (75%) presented with hydrocephalus, and 3 patients (25%) presented with hemorrhagic colloid cysts apparent on imaging. All patients had a colloid cyst in the third ventricle with a maximal diameter (average size, 1.2 cm).

Table 1:

Demographic data of 12 patients undergoing transcallosal resection of colloid cyst.

Radiological findings

Three patients had blood in their colloid cysts. The size of the colloid cyst was >2 cm in all three patients, while the other nine patients had a colloid cyst size of ≤2 cm. All three patients presented with signs of high Intracranial pressure (ICP) and hydrocephalus on imaging.

Surgical approach

Two patients presented with acute onset headache, papilledema, and active hydrocephalus, requiring emergency placement of external ventricular drains (EVDs) to relieve the obstruction. They underwent the same surgical approach as the other ten patients and had a similar postoperative course, with removal of the EVD before discharge. Gross total resection was achieved in 8 (66%) of the 12 patients, 4 (33%) patients had a near total resection with a small (<2 mm) attachment of the capsule to the contralateral corpus callosum [ Table 2 ]. Transcallosal resection was ordered for one patient (patient number 13, excluded); however, they ended up undergoing a transcortical interventricular approach due to cortical veins obscuring the transcallosal pathway.

Table 2:

Surgical details of 12 patients undergoing transcallosal colloid cyst resection.

Postoperative outcome

The patients’ follow-up periods ranged from 1 to 6 years (mean 3.5 years). In all 12 patients, 100% of the presenting symptoms attributed to the colloid cyst were either significantly improved or completely resolved at their postoperative follow-ups. Only three patients continued to have mild headaches, which significantly improved after surgery [ Table 3 ]. No patient required further treatment on postoperative follow-up.

Table 3:

Preoperative symptom outcomes.

One patient developed supplementary motor area (SMA) syndrome manifesting as akinesia and mutism [ Figure 3 ]. He also experienced one episode of spontaneously aborted seizures. The patient presented with an indwelling course (months) of headache, fatigue, and increased sleepiness. He was found to have a hemorrhagic colloid cyst in the foramen of Monro, measuring 50 mm³ in size. The corpus callosotomy was 1.3 cm in length in the middle third of the corpus callosum. Postoperative computed tomography on day 1 showed intracerebral hemorrhage around the left precentral sulcus. Follow-up magnetic resonance imaging (MRI) showed extensive left-sided encephalomalacia around the same area, explaining his SMA syndrome. The patient’s symptoms completely resolved after 1 year of follow-up.

Figure 3:

(a-c) T2-weighted axial and coronal and sagittal T1-weighted magnetic resonance imaging (MRI) of 55-year-old gentleman presenting with vague headache, memory disturbance showing a large hemorrhagic third ventricle colloid cyst with obstructive hydrocephalus. (d-f) Postoperative follow-up axial and coronal T2-weighted and sagittal T1-weighted MRI showing significant encephalomalacia on the side of entry (right). The patient developed immediate postoperative mutism, hemiplegia, and seizure. His symptoms resolved few weeks postoperatively.

Another patient, who presented with acute high Intracranial pressure (ICP) symptoms, developed one episode of postoperative seizures. The patient underwent a 1.83 cm anterior third callosotomy. On follow-up, the patient was symptom-free and had no further episodes. A third patient developed new onset postoperative short-term memory disturbance and difficulty concentrating which was resolved by her first follow-up. Another patient had a transient left facial nerve upper motor neuron palsy and left hemiplegia. Postoperative images showed no obvious vascular insults, and a middle third callosotomy measuring 1.34 cm in length. Her symptoms improved on discharge and completely resolved on follow-up [ Table 4 ].

Table 4:

Postoperative complications.

There was no mortality, meningitis, wound infection, SSS tearing or thrombosis, pericallosal artery injury, or disconnection syndrome. On postoperative imaging, there was no evidence of traction edema, infarction, or encephalomalacia in 11 of 12 patients. One patient had left-sided encephalomalacia apparent on MRI, which correlated with transient postoperative SMA syndrome.

DISCUSSION

Colloid cysts have always provoked the interest of neurosurgeons due to their benign histology, difficult anatomical location, variant clinical presentation, and relatively favorable prognosis. Throughout history, there has been a wide array of treatment options available for third ventricle colloid cysts.[ 9 , 14 ] This reflects the similarly wide spectrum of presentations ranging from asymptomatic to sudden death, as well as the difference in short- and long-term outcomes of each treatment option.

Over the past few decades, there has been a consensus regarding the complete resection of symptomatic colloid cysts. Asymptomatic colloid cysts are frequently resected because of the fear of acute ventricular obstruction and sudden death.[ 2 ]

The optimal surgical approach to reach and resect a third ventricle colloid cyst remains debatable.[ 9 , 10 , 14 , 20 ] The transcortical interventricular approach was the first used by Dandy to resect colloid cysts.[ 8 ] It allows for a wide surgical view and better complete resection of the cyst; however, the need for corticectomy has been shown to increase the risk of postoperative seizures.[ 16 ] In recent studies, the incidence of seizures in the transcortical approach is similar to that in the transcallosal and endoscopic approaches.[ 10 ] The endoscopic approach has gained popularity in the past two decades.[ 14 , 20 ] It has shown decreased postoperative complication rates due to its minimally invasive nature and improved surgical technique. However, it is not optimal for larger size colloid cysts with higher rates of incomplete resection.[ 10 ]

The transcallosal approach was first described in 1949 by Greenwood.[ 11 ] It has the advantage of going through the shortest direct route to the third ventricle with minimal tissue destruction along the way with preservation of the cortex.[ 3 ] Compared to other approaches, the transcallosal approach allows for a wider view of the surgical field and easy access to the tumor capsule with higher rates of complete resection.[ 10 ] Reported side effects, such as transient memory loss, mutism, and hemiparesis, have been more commonly observed in older reports. However, recent studies have shown an insignificant difference.[ 10 ]

A meta-analysis by Elshamy et al.[ 10 ] compared the three approaches and found no significant difference in the risk of postoperative seizure, memory disturbance, and shunt dependence between the three approaches. However, the transcortical approach showed an increased rate of postoperative weakness and the endoscopic approach showed increased rates of incomplete resection.

Presenting symptoms

Colloid cysts are located in the anterior two-thirds of the third ventricle or foramen of Monro in 80% of patients.[ 17 ] In our patients, 67% had a colloid cyst located in the Foramen of Monro, 3 patients (25%) had a colloid cyst anterior to Foramen Monro, and 1 patient (8.3%) had a colloid cyst posterior to Foramen Monro. Headache was the most common symptom in our patients. The onset of headache ranged from acute (3–14 days), as in patients presenting with high ICP headache, to chronic, with a more indwelling course progressing slowly over the years. Headache is the most commonly reported symptom in patients with colloid cysts.[ 1 , 6 , 12 ] The frequency of other symptoms such as memory disturbance, dizziness, visual disturbance, and high ICP were similar to those reported in the literature.[ 4 , 17 ] Only one patient presented with a drop attack. This is thought to arise from a ball valve effect in the ventricular system causing transient acute obstruction.[ 5 ] Two patients (16%) presented with acute symptoms with signs of obstructive hydrocephalus on imaging and required emergency CSF diversion (EVD) before surgical excision. The incidence of hydrocephalus at presentation ranges from 50% to 82%.[ 10 ] In our patients, 75% were found to have hydrocephalus on presentation.

Postoperative outcome

The prognosis for colloid cysts after surgical excision is favorable.[ 1 ] In our series, 100% of the presenting symptoms were significantly improved or resolved. Commonly reported complications after transcallosal colloid cyst resection include transient memory loss, seizures, transient hemiparesis, mutism, and sinus thrombosis.[ 21 ] This can be explained by the route of the delicate anatomy crossed during transcallosal resection. More recent studies have reported significantly fewer postoperative complications in transcallosal resection of colloid cysts. This may be attributed to advances in surgical skills and use of more precise surgical tools.[ 15 , 22 ] Indeed, the transient memory loss that is commonly reported in such cases has been theorized to be a result of intraoperative fornecial manipulation as with venous cortical infarcts and mutism when applying forceful traction on the cingulate gyrus and accompanying blood vessels.[ 13 ]

In our series, 1 patient (8%) developed SMA syndrome in the form of hemiparesis and mutism that completely resolved a few weeks after surgery. Mutism has been reported in the transcallosal approach and has not been attributed to partial callosotomy but to damage to surrounding structures such as the cingulate gyrus, wall of the third ventricle, and supplementary motor cortex.[ 3 , 18 ] This was the case in our patient where postoperative images showed bleeding in the contralateral supplementary motor cortex and surrounding encephalomalacia. All patients with postoperative complications showed complete resolution of symptoms postoperatively.

For callosotomy, the corpus callosum was incised in the midline between the pericallosal arteries for a length of 1.5–2.5 cm in the sagittal plane in the anterior corpus callosum. Larger incisions may impair interhemispheric functions and cause disconnection-like syndrome.[ 6 , 7 ] In our series, all 12 patients had a callosotomy below 2.5 cm (mean = 1.6 cm) in the middle third of the corpus callosum.

Our series was limited by its retrospective nature and small sample size. Many of the postoperative symptoms in the transcallosal approach affect more complex functions of the brain, which are difficult to measure. In this series, physical examination and subjective observations from patients during follow-up and phone interviews were used to evaluate symptom improvement, which may be susceptible to recall bias. Neurocognitive function testing was not performed in this patient group given the retrospective study design. A larger patient sample with more precise examination tools to measure postoperative outcomes is required.

CONCLUSION

Transcallosal resection of colloid cysts has a favorable prognosis. It allows for complete resection of the cyst with minimal transient postoperative complications. Most patients with postoperative complications show complete resolution of symptoms, with no long-term morbidity.

Declaration of patient consent

Patients’ consent not required as patients’ identities were not disclosed or compromised.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

Disclaimer

The views and opinions expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Journal or its management. The information contained in this article should not be considered to be medical advice; patients should consult their own physicians for advice as to their specific medical needs.

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