Microsurgical Treatment of Colloid Cysts of the Third Ventricle

Microsurgical Treatment of Colloid Cysts of the Third Ventricle

Original Article Microsurgical Treatment of Colloid Cysts of the Third Ventricle Alexander N. Konovalov, David I. Pitskhelauri, Michael Shkarubo, Sve...

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Original Article

Microsurgical Treatment of Colloid Cysts of the Third Ventricle Alexander N. Konovalov, David I. Pitskhelauri, Michael Shkarubo, Svetlana B. Buklina, Anna A. Poddubskaya, Mariya Kolycheva

BACKGROUND: This study analyzes the results of surgical treatment in 377 patients with colloid cysts (CCs) of the third ventricle who were treated at the Burdenko Neurosurgery Institute from 1981 to 2015. Operations were performed by a single surgeon (the first author of the article).

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METHODS: The transcallosal approach was used to remove CCs in 97% of cases. Total cyst removal was performed in 96% of cases (in 4% of cases, a small cyst capsule fragment was left on the veins and fornix); in 3 cases, the cyst recurred, which required its repeated removal.

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RESULTS: Hydrocephalus symptoms regressed in 98% of patients. The most frequent complications in the early postoperative period were memory impairments of varying severity, with a tendency to regress by the time of discharge. Two patients had an intraventricular hematoma, which required operative exploration in 1 patient. There were 4 cases of meningitis (including 1 shunt-associated meningitis) and 5 cases of transient pyramidal insufficiency.

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CONCLUSIONS: We made a preliminary assessment of the reasonability of the infratentorial supracerebellar approach for removal of CCs in 10 cases.

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INTRODUCTION

C

olloid cysts (CCs) are benign intracranial neoplasms accounting for 0.5%e2% of all intracranial tumors and 15%e20% of intraventricular tumors.1,2 Histologic and

Key words Colloid cyst - Microsurgery - Supracerebellar infratentorial approach - Third ventricle - Transcallosal approach -

Abbreviations and Acronyms CC: Colloid cyst CSF: Cerebrospinal fluid CT: Computed tomography EVD: External ventricular drainage

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immunohistochemical studies have shown that CCs originate from ectopic endodermal elements that migrate into the velum interpositum during development of the central nervous system.3-8 CCs are located in the anterior third ventricle and can block the interventricular foramen of Monro, causing obstructive hydrocephalus. The onset of clinical manifestations usually occurs at the age of 20e40 years. Cerebrospinal fluid (CSF) circulation disorders can be severe and even lead to sudden death of the patient.4,9-18 According to numerous studies, the risk of this outcome may reach 6%e45%.1,4,12,13,15,19-24 Numerous studies have been devoted to the surgical treatment of CCs of the third ventricle. They have mainly focused on a surgical resection technique. After direct microsurgical (transcortical or transcallosal) resection of CCs, a technique of stereotactic CC aspiration was implemented, which fell short of expectations.21,22,25-27 Two competing techniques are used for CC removal: a microsurgical transcallosal approach1,2 and an endoscopic approach.28-32 Both techniques were compared in several studies.23,33,34 Often, a limited number of cases are not sufficient to conclude certain disadvantages or advantages of techniques for treatment of CCs. The experience of surgical treatment of CCs accumulated at Moscow Burdenko Neurosurgery Institute represents a valuable source of information. The total number of patients who underwent CC removal at the institute from 1967 to 2017 amounted to 462. In most cases, the transcallosal approach was used. The purpose of this study is to describe the CC features (size, location) that underlie the most dangerous clinical manifestation (acute obstruction of CSF flow, which can lead to death); to evaluate, based on a large series of cases, the efficacy of the transcallosal approach; to determine the advisability of surgical removal of incidentally detected CCs; to study the possibility and reasonability

MRI: Magnetic resonance imaging VPS: Ventriculoperitoneal shunting Burdenko Neurosurgery Institute, Moscow, Russia To whom correspondence should be addressed: Michael Shkarubo, M.D. [E-mail: [email protected]] Citation: World Neurosurg. (2017) 105:678-688. http://dx.doi.org/10.1016/j.wneu.2017.06.012 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2017 Elsevier Inc. All rights reserved.

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of removing CCs not associated with hydrocephalus through the posterior third ventricle using a supracerebellar approach.

COLLOID CYSTS OF THE THIRD VENTRICLE

Table 1. Combination of Colloid Cysts of the Third Ventricle with Other Diseases of the Central Nervous System

METHODS

Disease

The study analyzes the results of surgical treatment of a consecutive retrospective series of 377 patients operated on by a single surgeon (A.N.K.) between 1981 and 2015 (by March 2017, 32 more patients had been operated on). The gender distribution was close to a 1:1 ratio with 188 males (49.8%) and 189 females (50.2%). The age varied from 1 to 74 years (median, 36.5 years). There were 20 children (5.3%) (<18 years). The diagnosis was based on clinical, computed tomography (CT), and magnetic resonance imaging (MRI) data. Six patients underwent surgery because of CC recurrence (in only 3 of these, cyst recurrence developed after surgery performed by the authors). In 51 cases (13.5%), CC resection was preceded by CSF diversion procedures (external ventricular drainage [EVD], ventriculoperitoneal shunting [VPS]). These procedures were performed mainly in other hospitals, before admission to the institute. To remove cysts, we primarily used the anterior interhemispheric transcallosal approach (361 cases; 95.7%); in rare cases (until 1982), transcortical (6 cases) and infratentorial supracerebellar (10 cases, patients were operated on in cooperation with D.I.P.) approaches were used (by March 2017, 1 more patient had been operated on). All surgeries were carried out under a microscope using a microsurgical technique. In the early postoperative period, all patients had CT scans to show any complication. Follow-up CT and MRI examination was performed in the long-term postoperative period to evaluate the extent of resection and the size of ventricles.

Tumors

Clinical Manifestations Of 377 patients analyzed, CCs in 21 (5.6%) were detected incidentally by MRI and CT studies related to a follow-up examination, traumatic brain injury, or another cerebral disease. Of these patients, 7 with incidentally diagnosed asymptomatic CCs of the third ventricle initially had no surgery. The patients were followed-up. About 2e10 years (mean, 5 years) after cyst detection, the patients developed symptoms of acute CSF circulation disorder, which required urgent hospitalization followed by cyst removal. The diameter of asymptomatic cysts ranged from 8 to 15 mm (mean, 13 mm). Most cysts were <13 mm. There were no differences in sizes of asymptomatic and symptomatic CCs. In 30 cases (8%), CCs were combined with other sentral nervous system diseases (Table 1). Thirty patients (8%) had episodes of acute noncommunicating hydrocephalus with symptoms of herniation. These conditions required urgent ventricular draining procedures (EVD, ventricular shunting), which were performed before admission to the Burdenko Neurosurgery Institute. The clinical manifestations of CCs, which are mainly caused by obstructive hydrocephalus, are presented in Table 2. In 6 cases (1.6%), a descent of the cerebellar tonsils was detected. These data are not significantly different from the statistical data on

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n

Glioblastoma

3

Meningioma

2

Quadrigeminal plate glioma

1

Petrosal paraganglioma

1

Breast cancer metastasis

1

Arterial aneurysm

1

Arnold-Chiari malformation (type I)

6

Nasal cerebrospinal fluid leakage

4

Arachnoid cyst

2

Other disease (cheiloschisis, Hirschsprung disease, myasthenia gravis, multiple sclerosis, trigeminal neuralgia)

9

the rate of Arnold-Chiari syndrome type I in the population.35 However, among patients with CC who had a history of acute occlusive events with impairment of vital functions and brain dislocation, a descent of the cerebellar tonsils occurred 7-fold more often than in the population (of 30 patients who had occlusive events, a descent of the cerebellar tonsils was detected in 2). Nasal CSF leak as a consequence of severe hydrocephalus.36 was observed in 4 cases (1%). Diagnostics In CT and MRI studies, CCs appeared as unilocular, rounded, and distinctly demarcated lesions in the interventricular foramen of Monro region with a diameter ranging from 5 to 52 mm (median, 15 mm) (Figure 1). Dimensionwise, the cysts fell into the following categories: 27 (7%) small (5e9 mm), 162 (43%) intermediate (10e15 mm), 125 (33%) large (16e20 mm), and 63 (17%) giant cysts (>20 mm). The neuroimaging characteristics differed depending on the structure and density of the colloid substance. In 258 cases (68.5%), CCs had a homogeneous structure: a viscous stringy colloid in 196 cases (52%), liquid watery content in 19 cases (5%), and in 49 cases (13%), the CC contents consisted of a dense substance, which had a hyperintense T1-weighted signal and a hypointense T2-weighted signal on MRI. In 31.5% of cases, the cyst structure was heterogeneous: a dense component primarily located in the posterior parts of the cyst, and a liquid/colloid content situated in the anterior parts of the cyst. Heterogeneous density and signal were observed on CT and MRI scans, respectively. Depending on the primary location, CCs were topographically divided into 2 main groups: 1) cysts of the anterior third ventricle, with the entire cyst being located in the third ventricle cavity at the foramen of Monro level; 2) cysts situated between the columns of the fornix and extending into the cavum pellucidum, with more than 50% of the cyst volume being located above the fornix, in the

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Table 2. Clinical Manifestations of Colloid Cysts of the Third Ventricle Clinical Signs Symptoms of increased intracranial pressure

n

%

301

79.9

Episodes of acute obstruction

132

41.7

Papilledema

141

44.6

Severe psychoemotional, memory disorders

25

7.9

Pyramidal signs

51

16.1

cavum septum pellucidum. Cysts of the first group prevailed: 324 patients (86%); only 53 patients (14%) had a cyst located between leaflets of the septum pellucidum, with the mean cyst size in this group being 17 mm (Figure 2). CC Progression Over time, CCs may increase in size as a result of the secretory activity of epithelial cells.1,37-40 In several cases, we were able to trace the changes occurring in CCs (Figures 3 and 4). In 1 case, instead of an increase in the cyst size, colloid thickening occurred (Figure 5). Usually, the group of CCs of the third ventricle also includes xanthogranulomas, which are cystic cholesterol-rich lesions of the choroid plexus of the third ventricle.41,42 On CT images, they appear as round hypodense lesions; they have a hyperintense signal on T1-weighted MRI scans and a hypointense signal on T2-weighted MRI scans. Xanthogranulomas do not differ from CCs in location and size but are less common. In our study, only 8 patients (2%) had xanthogranuloma. The following features were shown during surgery: a dense capsule closely fixed to the surrounding structures with the contents rich

in cholesterol and with the color ranging from yellow to dark brown. Hydrocephalus of varying severity (Evans index, 0.19e0.47), resulting from interventricular foramen obstruction, was observed in most cases (n ¼ 281; 74.5%); among these patients, 126 (33.5%) had ventricular asymmetry of varying degrees. In some cases, the foramen of Monro on the side of a more dilated ventricle was intraoperatively found to be blocked not only by a cyst but also by the choroid plexus. In the other 89 cases (23.6%), hydrocephalus was absent (Evans index, 0.19e0.3). The location of CCs is associated with the severity of hydrocephalus; in pronounced hydrocephalus, cysts can descend, almost reaching the sella turcica level. In 4 cases, it was necessary to differentiate CCs from other tumor and nontumor lesions of the third ventricle region, which had similar neuroimaging features; these included polycystic astrocytoma (3 cases) and intraventricular craniopharyngioma (1 case). Surgery EVD and Shunting. Pronounced hydrocephalus or episodes of acutely increased intracranial pressure was the cause for urgent CSF shunting that was performed in 51 patients (13.5%) before CC removal (45 patients underwent the procedure in hospitals at their place of residence): EVD in 18 patients, VPS in 28 patients, and Torkildsen ventriculocisternostomy in 15 patients. Of these patients, 12 underwent repeated CSF shunting (EVD, VPS, Torkildsen ventriculocisternostomy) because of infectious complications and shunt dysfunctions, which were performed in hospitals at the place of residence. In 6 cases, CSF shunting was performed at the Burdenko Neurosurgical Institute (3 EVD cases, 2 Torkildsen ventriculocisternostomy cases, and 1 VPS case). All complications of CSF shunting were associated with placement of EVD and VPS in hospitals at the place of residence:

Figure 1. Variability of the colloid cyst size. (A) A small colloid cyst. (B) A large colloid cyst.

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ORIGINAL ARTICLE ALEXANDER N. KONOVALOV ET AL.

Figure 2. Locations of colloid cysts of the third ventricle. (I, II) A schematic of 2 types of cyst location; (A, B) colloid cysts of the septum pellucidum. Almost the entire cyst volume is located above the roof of the third ventricle (A, arrows), spreading the leaflets of the

meningitis in 7 cases, shunt dysfunction in 5 cases, chronic subdural hematoma in 1 case, and visual impairments (when ventricular drains were incorrectly placed in the posterior horns) in 4 cases. Of 41 patients who previously underwent CSF shunting (VPS and Torkildsen ventriculocisternostomy), a shunting system was removed simultaneously with CC resection in 12 cases. (Shunts were removed 3e4 months after their placement, on average; there were no signs of shunt dependence in these patients.) Microsurgical Removal of CCs. As discussed earlier, the main technique of CC removal was the transcallosal approach, which was used in most patients (n ¼ 361; 95.7%). In 6 early cases, the

Figure 3. Case 1. A 34-year-old man, on examination at the Institute in the preecomputer era, was diagnosed with hydrocephalus of unclear genesis. The patient underwent Torkildsen ventriculocisternostomy. After 20 years, the patient was readmitted to the Institute with symptoms of a severe diencephalic lesion and a giant cyst of >50 mm in diameter. The giant colloid cyst

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septum pellucidum (B, arrows). (C, D) Colloid cysts of the third ventricle. The cyst is entirely located in the anterior third ventricle, under structures of the roof of the third ventricle (arrows indicate the fornices dislocated upward).

transcortical approach was used for CC removal. In 10 cases, CC was removed by an infratentorial supracerebellar approach. Transcallosal Approach. The transcallosal approach is well known and widely used for removal of midline neoplasms. It was described in detail by Hernesniemi et al.2 We describe some details that, in our opinion, are important for the transcallosal approach. To access the corpus callosum, dissect it, and resect the cyst through the foramen of Monro, a distance of 2e2.5 cm along the sagittal sinus was sufficient, so transection of one of the parasagittal veins was seldom required. We did not use navigation systems for performing the approach. To directly approach the foramen of Monro, the

of the third ventricle: (A) a magnetic resonance imaging scan before surgery, (B) a computed tomography scan after removal of the cyst. During surgery (transcallosal removal), extreme adherence of the cyst wall to the third ventricle structures was shown; as a result, cyst wall fragments remained unresected.

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Figure 4. Case 2. A male who had traumatic brain injury at the age of 14 years. On examination, the patient was diagnosed with an asymptomatic colloid cyst (Figure 2A). No surgical treatment for the colloid cyst was performed. The patient’s condition worsened after 10 years when severe headache appeared; later, nausea, vomiting, and depression of consciousness, up to a deep sopor, developed. A control magnetic resonance imaging (MRI) study showed an increase in the colloid cyst size and obstructive hydrocephalus

microscope axis is oriented toward the biauricular line. In the case of long-term hydrocephalus, the corpus callosum is significantly thinned; the interventricular septum can be fenestrated, and its significant part may be absent43; the roof of the third ventricle and CC may be dramatically displaced downward. If hydrocephalus is absent, and the corpus callosum has a normal thickness, the microscope orientation should be precise, and dissection of the corpus callosum between the pericallosal arteries should be performed right of the midline to avoid damage to the fornix. In most cases, CCs are located at the foramen of Monro level, but cysts can occur behind the venous angle, in the region of the third ventricle roof, and may not be immediately identified during exploration of the interventricular foramen. Often, a cyst is covered by the choroid plexus, which is sometimes coagulated and partially excised to widely expose the cyst wall (Figure 6). Large long-term CCs can dramatically deform the fornix, which may be damaged during mobilization and resection of the cyst. In the case of large cysts extending between the leaflets of the interventricular septum, cyst removal requires incising one of the interventricular septum leaflets together with the cyst wall; after

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(Figure 2B). The patient underwent urgent biventriculoperitoneal shunting (at the place of residence), which caused regression of obstruction symptoms. The third ventricle colloid cyst increased in size over time: (A) primary diagnosis of colloid cyst; (B) MRI after 10 years: a large cyst and hydrocephalus. At the Burdenko Neurosurgical Institute, the patient underwent microsurgical excision of the colloid cyst of the third ventricle simultaneously with removal of the shunting system.

evacuation of the cyst contents, the incision is used to withdraw and resect the cyst wall. In 9 cases with a cavity located between the leaflets of the interventricular septum, immediately after midline dissection of the corpus callosum, the wound tract entered the cavity of the fifth ventricle; the cyst dome was exposed; and the cyst was removed. The mean operating time (from the beginning of cyst removal to completion of hemostasis) was 24 minutes. Results of Surgical Removal of Third Ventricle CCs. Total CC removal was performed in 362 of 377 patients (96%). In 14 cases (4%), small fragments of the CC capsule, which were tightly adhered to the veins, fornix, or walls of the third ventricle, remained unremoved; the fragments were carefully coagulated. Complications. Complications related to third ventricle CC removal are presented in Table 3. The most severe surgical complication was intraventricular hematoma, which required a revision surgery in one case and an external draining procedure in another. On control CT, blood pooling in the posterior horns of the lateral ventricles was observed in 10 patients (2.9%). This surgical complication, not

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Figure 5. Case 3. A 46-year-old woman with a newly identified colloid cyst. No surgery was suggested at the place of residence. No increase in the cyst size occurred during a 14-year follow-up period, but there was significant densification of the colloid substance: (A) T2-weighted magnetic resonance imaging (MRI) (1999), a large colloid cyst; dynamic follow-up, (B)

apparent clinically, was associated with bleeding during cyst removal. Revision was not required in any of the cases, because a series of lumbar punctures solved the problem. Follow-up CT showed a small epidural hematoma, which also did not require surgical intervention. One patient required a VPS in the postoperative period, because a quadrigeminal glioma was diagnosed that led to aqueduct obstruction.

COLLOID CYSTS OF THE THIRD VENTRICLE

T1-weighted MRI (2007), a large heterogeneous colloid cyst; (C) T1-weighted MRI (2013), the cyst size did not change, but the signal intensity changed as a result of increased density of the colloid substance. Because of worsening of the clinical symptoms, the colloid cyst was removed by the transcallosal approach in 2013.

Recurrences. CC recurrence that required reoperation was observed in 3 cases (0.8%) at 4e11 years after primary surgery. In 2 cases, cysts were located in the interventricular septum. In one of the

Cognitive Functions. The state of cognitive functions before and after surgery was carefully examined in 53 patients using the Luria methodology developed at our institute; in addition, the memory sphere was examined in 20 patients using the Rey Auditory Verbal Learning Test. In general, no split-brain symptoms occurred in patients in whom the transcallosal approach was used. In the next few days after surgery, worsening of memory impairments occurred in almost half of the cases, and 6 patients (11.3%) developed Korsakoff syndrome. All memory impairments, regardless of their severity, gradually regressed. Postoperative Complications After Removal of Asymptomatic CCs. In the postoperative period, in the group of patients with incidentally identified CCs (n ¼ 21), 5 developed moderate amnestic disorders and 2 developed severe mental and amnestic disorders (Korsakoff syndrome). On control examination by a neuropsychologist after 6 months, regression of mental and amnestic disorders was observed. One patient had a hematoma in the third ventricle, which did not require a revision operation. In general, the rate of postoperative complications was similar in both the asymptomatic cyst group and the major study group.

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Figure 6. An intraoperative image. The transcallosal approach. CC, colloid cyst; ChP, choroid plexus; F, fornix; VSP, septum pellucidum vein.

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Table 3. Complications After Microsurgical Removal of Colloid Cysts of the Third Ventricle Complications

n (%)

Third ventricle hematoma

2 (0.53)*

Epidural hematoma (<10 mm thick)

1 (0.26)

Meningitis

4 (1.06) 1 of these is shunt-associatedy

Severe mental and memory disorders: Korsakoff syndrome (partially regressed at discharge)

22 (5.8)

Transient pyramidal symptoms

5 (1.32)

Epileptic seizures in the early postoperative period (transcallosal approach)

2 (0.53)

*One of the patients needed revision surgery. yBefore admission to the Burdenko Neurosurgery Institute, a patient underwent placement of a shunt, which was complicated by meningitis.

cases, a small cyst capsule fragment adhered to the internal cerebral veins was not removed during primary surgery. During the revision surgery 11 years later, a large cyst was located behind the interventricular foramina adhered to the third ventricle roof. The cyst was completely removed through an enlarged interventricular foramen. In the other case, during the initial surgery, an accumulation of colloid substance was discovered between the layers of the interventricular septum and the capsule was absent. During repeated surgical intervention 7 years later, an accumulation of the colloid substance was again observed between the interventricular septum layers, with no capsule present. This was the only case in the entire series; in the other cases, the colloid substance was surrounded by a capsule of varying density. In the third case, the CC recurrence was observed after pregnancy, 4 years after the removal of a small cyst. In addition to these cases, in another case, cyst recurrence was suspected based on control neuroimaging, but an endoscopic examination did not detect any cyst. DISCUSSION Clinical Manifestations Clinical manifestations of CCs are widely described. They include gradually increasing signs of intracranial hypertension; increasing intensity of headaches, accompanied by nausea and vomiting; and memory disorders. The onset of symptoms usually takes place between the ages of 20 and 40 years.2,22,28,44 The most dangerous complication associated with CCs of the third ventricle is acute obstruction of the CSF pathway with a secondary dislocation of the brain and vital disturbances.4,9-18 In several cases, acute obstruction symptoms caused by CC may worsen so rapidly and irreversibly that even urgent ventricular drainage may fail. This situation is shown by the following case: a 34-year-old man was admitted to the Burdenko Neurosurgery Institute with severe headaches and with a CC of the third ventricle detected during CT. On the day of admission, the patient had an acute occlusive event with rapid depression of consciousness. Emergency ventricular drainage did not improve the patient’s

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condition: a deep coma with impairment of vital functions persisted. Removal of the CC on the next day did not affect the patient’s condition, and he died 2 days later. A postmortem examination showed necrosis of the hypothalamus. (Because the patient’s death was not associated with removal of the cyst, we excluded this case from the analysis of treatment results for third ventricle CCs.) The risk of sudden death affected our tactics of managing patients with CC: urgent surgery (in the first 1e2 days after admission), especially if attacks of acute headache with impaired consciousness occurred in medical history of patients. Defining the indications for surgery of incidentally detected asymptomatic CCs is a more complex problem. There are different points of view in the literature. On the basis of our experience, we prefer surgical removal of CCs in most cases, especially in young patients. Asymptomatic CCs Asymptomatic CCs were detected in 21 patients (5.6%). The size of identified CCs ranged from 8 to 15 mm and did not differ from that of symptomatic CCs. In addition, in 7 cases of asymptomatic CCs, surgery was not performed initially. In 2e10 years (mean, 5 years), these patients developed clinical manifestations in the form of episodes of CSF circulation disturbances, which required emergency hospitalization and surgical treatment of the patients. This experience shows that asymptomatic cysts may cause lifethreatening complications that may occur in conditions when adequate surgical care may not be available. According to our data, the risk of complications associated with removal of asymptomatic cysts is relatively small. As noted earlier, 7 patients had amnestic disorders in the postoperative period; the disorders were particularly severe (Korsakoff syndrome) in 2 of these patients, but a control examination by a neuropsychologist 6 months later showed regression of mental and amnestic disorders. One patient had a hematoma in the third ventricle, which did not require revision surgery. Conservative management of patients and periodic MRI control may be reasonable in elderly patients with asymptomatic CCs without ventriculomegaly.22,44,45 In general, the situation with reasonability of asymptomatic CC removal is similar to that with incidentally discovered silent arterial aneurysms. Acute CSF circulation disturbances with brain herniation and vital disorders were found in the medical history of 30 patients (8%). Before the patients were admitted to the Institute, EVD or VPS placement was performed (in hospitals at the place of residence) because of the life-threatening condition. CSF shunting procedures may be considered only as urgent measures or in the case of a patient’s refusal of direct or endoscopic surgery because after these procedures, a gradual increase in the CC size may continue in the long-term period, which may lead to the development of hypothalamus and midbrain injury symptoms (Figure 5, case 1). Size and Location of CCs Of particular interest is the dependence of life-threatening acute hypertensive crises on the size and location of cysts. In our observations, acute obstruction of CSF flow developed primarily in patients with medium and large cysts (10e20 mm). Similar episodes were absent in patients with cysts located in the

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ORIGINAL ARTICLE

0.53

interventricular septum, although ventricular dilation was also typical of these patients. Obviously, cyst mobility is crucial for acute blockage of the foramen of Monro. Developing increased pressure in the lateral ventricles makes obstruction complete and usually irreversible. During surgery, in a third of cases, we faced the situation in which the foramen of Monro was blocked not only by a cyst but also by the choroid plexus located above the cyst. These facts suggest that entrapment of a choroid plexus fragment followed by its increase in size as a result of impaired venous outflow may be one of the mechanisms for severity and irreversibility of obstruction episodes caused by CCs. Our observations also suggest that obstruction episodes with dislocation events may lead to the development of secondary Arnold-Chiari malformation. We have identified significant differences in the clinical manifestations of cysts typically located in the anterior third ventricle and cysts located between the pellucid septum leaflets: the latter occur less often (according to our data, in 14% of cases), reach larger sizes, and are associated with a lower risk of life-threatening episodes of acute CSF circulation disturbances. *In 1 of 4 patients, meningitis developed because of a shunt that was placed in the patient before admission to the Burdenko Neurosurgical Institute. yComparison of the data on the rate of amnestic disorders was not possible because of different methods of assessing memory impairments.

2.6 0.58 0 Present series (n ¼ 377)

96

0.79

1.06*

1.32

5.8y

0.38

3.0

0

5.1

1.2 0.9 2.7 0.3

4.3

3.91

1.4

58.2 0.6

Microsurgery (n ¼ 552)

96.8

1.48

1.6

1.6

5.0

COLLOID CYSTS OF THE THIRD VENTRICLE

Endoscopy (n ¼ 666)

Epileptic Intraventricular Blood Memory Mortality (%) Radicalness (%) Recurrence (%) Seizures (%) Meningitis (%) Hemisyndrome (%) Accumulation (%) Impairment (%) Reoperation (%) Treatment

Table 4. Comparative Characterization of Postoperative Complications of Microsurgical and Endoscopic Removal (According to the Literature Data23) and Microsurgical Resection of Colloid Cysts (Present Series)

ALEXANDER N. KONOVALOV ET AL.

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Surgery As discussed earlier, the main treatment of CCs of the third ventricle, which we used, was their transcallosal removal. The transcallosal approach has been widely used at the Burdenko Neurosurgery Institute to resect tumors (and other spaceoccupying lesions) of the third and lateral ventricles, thalamus, and midbrain. Our experience with the transcallosal approach in the treatment of more than a thousand patients suggests that a small dissection (1e1.5 cm) of the corpus callosum, which is necessary for accessing the third ventricle, is not accompanied by any neurologic symptoms. A small distance (2e2.5 cm) between the parasagittal veins is sufficient for CC removal. Therefore, transection of one of the parasagittal veins is necessary in rare cases. A complication that might be explained by impaired venous outflow developed only in 1 of the early cases. A 72-year-old female patient developed contralateral limb paresis after CC removal, which partially regressed in 7 days. Memory and Mental Disorders Memory and mental disorders are typical clinical manifestations of CCs of the third ventricle both before surgery and especially in the early postoperative period.2,22,23,46 As noted earlier, these changes were comprehensively studied in 53 cases, both before and during the postoperative period, using the Luria method (developed at our institute in 1962) for qualitative assessment of memory. Before surgery, most patients, especially those with hydrocephalus, had minor or moderate (primarily auditory-verbal) memory impairments. After surgery, improvement of the mnestic processes occurred in 14% of patients, which was associated with resolution of hydrocephalus. Approximately half of the patients (according to a neuropsychological study) had worsening of amnestic disorders in the early postoperative period. Korsakoff syndrome in the early postoperative period occurred in 22 of 377 patients (5.8%). Memory impairments, regardless of their severity, gradually regressed. It should be noted that no

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Figure 7. (A) The infratentorial supracerebellar approach design: the green arrow indicates the approach direction; red dashed lines designate the main stages (I, II, III) of the approach. (B) Intraoperative images of the main stages of the infratentorial supracerebellar approach. 3V,

split-brain symptoms were detected in these cases despite the use of the transcallosal approach. The pathogenesis of memory impairment in patients with CCs is complex. The role of fornix damage is obvious.46-50 More pronounced amnestic disorders occurred in patients in whom adhesions between the cyst walls and fornix as well as fornix deformities were found during surgery, and removal of the cyst was inevitably accompanied by damage to the fornix.51 Memory impairment was also associated with removal of small cysts using the infratentorial supracerebellar approach through the posterior third ventricle, aside of the fornix.

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posterior third ventricle; ChP, choroid plexus; F, fornix; G, vein of Galen; H, habenula; IA, interthalamic adhesion; IV, internal vein; M, foramen of Monro (left); P, pineal gland; Q, quadrigeminal plate; Th, thalamus.

RESULTS A study by Sheikh et al.23 compared the data of 583 patients with CCs of the third ventricle treated by the microsurgical technique and 695 patients treated by the endoscopic technique. These investigators concluded that microsurgical resection of CCs was characterized by higher radicalness and a lower rate of recurrences and repeated operations compared with those in endoscopic removal. Microsurgical removal was associated with more complications compared with those in endoscopic surgery. Comparing our data and the literature for microsurgical and endoscopic techniques for CC removal,23 the microsurgical

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COLLOID CYSTS OF THE THIRD VENTRICLE

technique, being undoubtedly more radical, may be as traumatic as the endoscopic technique, which is shown by the data given in Table 4. Comparison of the results of transcallosal CC removal in patients with hydrocephalus and those with normal ventricles did not show any fundamental differences. However, there were certain technical features of surgery in patients with normal ventricles. In the presence of hydrocephalus, the corpus callosum is thinned, whereas in the case of normal ventricles, it is necessary to dissect the unaltered corpus callosum, the thickness of which reaches 5e6 mm. In this regard, we considered it reasonable in certain cases, first in the case of normal ventricles, to use an approach not associated with dissection of any anatomic brain structures (e.g. the supracerebellar approach through the posterior third ventricle). We previously described the technique for removal of CCs of the third ventricle,52 and in this study, we confined ourselves to providing the approach design and intraoperative images of the main surgical stages.

The first similar surgery was performed in a female patient with CC combined with breast cancer metastasis in the right cerebellar hemisphere. The approach to the CC from the posterior cranial fossa seemed reasonable after resection of the metastasis, which facilitated the infratentorial supracerebellar approach. The approach is technically more complex than the transcallosal one. The surgical wound is about 50% deeper and requires application of longer microsurgical tools. All surgical stages should be performed under high microscope magnification. For surgeons experienced in removing tumors of the pineal region and posterior third ventricle, these difficulties are easily overcome. Because of the small number of cases, it is too early to conclude the reasonability of this approach for removal of CCs. We cannot recommend it as the method of choice. This approach is advisable for combined disease (e.g., a combination of a posterior cranial fossa tumor with CC of the third ventricle).

Infratentorial Supracerebellar Approach The features and technique of the supracerebellar approach used for removal of CCs of the third ventricle were described previously.52 The main stages of the supracerebellar approach are presented in Figure 7. This technique was used to remove CCs of the third ventricle in 10 cases analyzed in this study and in another case that occurred after preparation of the article. In the early postoperative period, 1 female patient developed marked psychoemotional and amnestic disorders, which regressed by the fourth day. Four patients had slight worsening of amnestic disorders.

The transcallosal approach enables radical resection of CCs of the third ventricle with a minimum number of complications. The clinical symptoms of CSF circulation disturbance are urgent indications for removal of CCs of the third ventricle. Removal of CCs is also indicated for asymptomatic cysts, primarily in patients of young and middle age. If surgery is refused, monitoring of the patient’s condition using repeated CT or MRI is necessary. Because of the rarity of this disease, patients with CCs of the third ventricle should be operated on in neurosurgical centers possessing resources and experience for removal of spaceoccupying lesions of the third ventricle.

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CONCLUSIONS

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Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Received 9 November 2016; accepted 2 June 2017 Citation: World Neurosurg. (2017) 105:678-688. http://dx.doi.org/10.1016/j.wneu.2017.06.012 Journal homepage: www.WORLDNEUROSURGERY.org

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