Technical strategies for the transcallosal transforaminal approach to third ventricle tumors: expanding the operative corridor

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Object

There are a number of surgical approaches to the third ventricle, each with advantages and disadvantages. Which approach to use depends on the location of the lesion within the ventricle, the goals of the operation, and the surgeon's experience. The authors present their results in children with a modified approach through the expanded foramen of Monro.

Methods

A retrospective study was conducted to identify and analyze all children who underwent what the authors term the “expanded transforaminal” approach to the third ventricle between 2010 and 2013. Perioperative data included patient demographics, signs and symptoms on presentation, tumor characteristics (type, origin, and size), complications, and clinical and radiographic outcome at final follow-up.

Results

Twelve patients were identified (5 female, 7 male) with a mean age of 9 years (range 2–19 years). Two patients underwent gross-total resections, whereas 10 resections were less than total. There were no instances of venous infarction, significant intraoperative bleeding, or short-term memory deficits. Of the 12 patients, 7 suffered a total of 17 complications. Disruption of neuroendocrine function occurred in 4 patients: 2 with transient diabetes insipidus, 2 with permanent panhypopituitarism, and 1 with central hypothroidism (1 patient had 2 complications). The most common group of complications were CSF-related, including 2 patients requiring a new shunt. There was 1 approach-related injury to the fornix, which did not result in any clinical deficits. One child with an aggressive malignancy died of tumor progression 6 months after surgery. Of the remaining 11 patients, none have experienced tumor recurrence or progression to date.

Conclusions

The expanded transcallosal transforaminal approach is a safe and relatively easy method of exploiting a natural pathway to the third ventricle, but there remain blind zones in the anterosuperior and posterosuperior regions of the third ventricle.

Abbreviation used in this paper:EVD = external ventricular drain.

Object

There are a number of surgical approaches to the third ventricle, each with advantages and disadvantages. Which approach to use depends on the location of the lesion within the ventricle, the goals of the operation, and the surgeon's experience. The authors present their results in children with a modified approach through the expanded foramen of Monro.

Methods

A retrospective study was conducted to identify and analyze all children who underwent what the authors term the “expanded transforaminal” approach to the third ventricle between 2010 and 2013. Perioperative data included patient demographics, signs and symptoms on presentation, tumor characteristics (type, origin, and size), complications, and clinical and radiographic outcome at final follow-up.

Results

Twelve patients were identified (5 female, 7 male) with a mean age of 9 years (range 2–19 years). Two patients underwent gross-total resections, whereas 10 resections were less than total. There were no instances of venous infarction, significant intraoperative bleeding, or short-term memory deficits. Of the 12 patients, 7 suffered a total of 17 complications. Disruption of neuroendocrine function occurred in 4 patients: 2 with transient diabetes insipidus, 2 with permanent panhypopituitarism, and 1 with central hypothroidism (1 patient had 2 complications). The most common group of complications were CSF-related, including 2 patients requiring a new shunt. There was 1 approach-related injury to the fornix, which did not result in any clinical deficits. One child with an aggressive malignancy died of tumor progression 6 months after surgery. Of the remaining 11 patients, none have experienced tumor recurrence or progression to date.

Conclusions

The expanded transcallosal transforaminal approach is a safe and relatively easy method of exploiting a natural pathway to the third ventricle, but there remain blind zones in the anterosuperior and posterosuperior regions of the third ventricle.

The third ventricle is a narrow midline cavity located between the thalami and is challenging to approach microsurgically. It is surrounded by many critical neurovascular structures, which if injured as a result of direct compression, ischemia, invasion, or surgical manipulation, can result in significant morbidity (Fig. 1). Lesions found within the third ventricle of children are primarily neoplasms, the most notable exception of which are colloid cysts.

Fig. 1.
Fig. 1.

Illustrations of the third ventricle. The third ventricle is bordered anteriorly by the lamina terminalis and anterior commissure, laterally by the thalami, inferiorly by diencephalic structures anteriorly and the mesencephalon posteriorly, superiorly by the foramina of Monro and the tela choroidea/velum interpositum (with the internal cerebral veins), and posteriorly by multiple structures including the suprapineal recess, habenular commissure, pineal body and pineal recess, posterior commissure, and aqueduct of Sylvius (A). The thalamostriate vein picks up a number of draining veins as it flows toward the venous angle, where it is joined by the anterior septal vein (B). Coronal and sagittal views show a mass within the anterior third ventricle (C and D). © The Neurosurgical Atlas, Aaron A. Cohen-Gadol. Used with permission.

Various operative approaches to the third ventricle have been described, each with its advantages and disadvantages. The selected approach depends on a number of variables, including the goal of surgery (such as biopsy, decompression of a cyst, reestablishment of CSF pathways, or complete surgical extirpation); the size, location, and displacement of the surrounding neurovascular structures by the lesion; and the surgeon's experience and preference. In general, the lateral ventricle can be accessed via the transcortical or transcallosal routes. Once the surgeon is in the lateral ventricle, the third ventricle can be entered in a number of ways. The transchoroidal or “suprachoroidal” approach involves opening the ependymal reflection (the choroidal fissure) along the medial border or forniceal side of the choroid plexus, called the taenia fornicis.9 This approach will provide access to the roof of the third ventricle, known as the velum interpositum, with the surgical corridor located between the internal cerebral veins. Alternatively, the choroidal fissure lateral to the choroid plexus can be opened (the taenia choroidea) in what is called the “subchoroidal” approach.1,2 The interforniceal approach has been described for pathology located in the hypothalamic region of the third ventricle, particularly hamartomas.10 This approach is easier if the patient has an existing cavum septum pellucidum so as to minimize manipulation of both forniceal columns. This approach, as well as the translamina terminalis route, provides excellent access to lesions located in the anterior-most portion of the third ventricle.6

In this paper we present a simple variant of another well-described operative corridor to the third ventricle. The transforaminal approach is a natural route to the third ventricle because one can usually visualize the lesion immediately and the foramen of Monro is often expanded by the lesion or by attendant hydrocephalus.5 However, this approach requires passing instruments in and out of it, thereby placing the ipsilateral forniceal column and the venous structures at the venous angle at risk. We review our experience with this modified expanded transforaminal approach, emphasizing surgical technique and clinical outcomes, and complications.

Methods

Study Design and Data Collection

Institutional review board approval from the University of Tennessee Health Science Center in Memphis, Tennessee, was obtained prior to data collection. We reviewed the operative notes of all children who underwent a craniotomy for resection of a third ventricular mass since 2010 at Le Bonheur Children's Hospital. Only those consecutive patients who underwent the approach as described below and who had a minimum of 6 months follow-up were eligible for inclusion. Those patients in whom another approach to the third ventricle was used or where the approach was not clearly delineated were excluded. Recorded variables were age, sex, race, symptoms and presence of hydrocephalus on presentation, tumor size and pathology, intra- and postoperative complications (categorized as vascular, endocrine, CSF-related, approach-related, wound, and nonneurological), and radiological and clinical status on follow-up. We also recorded whether the patient received any adjuvant therapy, such as radiation and/or chemotherapy.

Operative Technique

The patient is positioned supine, the neck is flexed with the vertex toward the ceiling, and the head is immobilized with a skull clamp. Extra caution is required when using pins on children less than 2 years of age or with chronic hydrocephalus and thin calvaria. There are several options for the skin incision: coronal, midline, or U-shaped (Fig. 2). The bone flap is typically made on the right side, and is approximately 6 cm anterior to posterior, either centered on the coronal suture or two-thirds anterior (4 cm) and one-third (2 cm) posterior to the suture, depending on whether a more posteriorly directed trajectory is required. The dura is opened in a semilunar fashion with the base located along the superior sagittal sinus. It may be necessary to sacrifice 1 or possibly 2 small bridging veins to gain access to the interhemispheric fissure, but this should be of little consequence in this region.

Fig. 2.
Fig. 2.

Positioning and planning of the skin incision (dashed red line) and underlying bone flap (solid black line). The craniotomy may be centered over or just anterior to the coronal suture. © The Neurosurgical Atlas, Aaron A. Cohen-Gadol. Used with permission.

Neuronavigation is helpful to orient the operator with respect to the desired trajectory to reach the ventricle through an appropriately located incision along the corpus callosum. A 2-cm callosotomy is situated just to the right of midline, exposing the lateral ventricle. Release of CSF at this point relaxes the frontal lobe and obviates the need for sustained brain retraction through the use of fixed retractors. A small section of choroid plexus just posterior to the venous angle and foramen is coagulated (Fig. 3A). The anterior septal vein is coagulated and sharply cut just above the venous angle, allowing gentle medial retraction of the ipsilateral fornix and lateral displacement of the thalamostriate vein (Fig. 3B). A nonabrasive cottonoid is placed over the exposed fornix and gentle traction is applied to the cottonoid rather than directly to the fornix. There is typically a small section of ependyma lying under the choroid plexus between the posterior edge of the foramen and the anterior margin of the ipsilateral thalamostriate vein. This ependyma can be opened with microdissectors and gentle spreading of the bipolar tips (Fig. 3C). Collectively, these maneuvers significantly expand the foramen of Monro, facilitating improved visualization of the posterior third ventricle and resection of the pathology at hand (Fig. 4). Dissection within the velum interpositum along the medial wall of the ipsilateral internal cerebral vein may be performed to further expand the operative corridor into the third ventricle. There are a number of small perforating arteries adjacent to the veins, which are thalamoperforators; care should be taken to protect and preserve these vessels.

Fig. 3.
Fig. 3.

Maneuvers to expand the foramen of Monro. A: Coagulation of a small amount of choroid plexus as it enters the foramen. B: Coagulation of the septal vein, which allows gentle medial retraction of the septum and fornix without risk of avulsion. C: Further dissection of the taenia fornicis at the posterior aspect of the foramen toward the velum interpositum. © The Neurosurgical Atlas, Aaron A. Cohen-Gadol. Used with permission.

Fig. 4.
Fig. 4.

Illustrations showing resection of the mass through the expanded foramen of Monro. © The Neurosurgical Atlas, Aaron A. Cohen-Gadol. Used with permission.

Once the mass is removed or debulked, the aqueduct should be visualized and an angled mirror or a 70° endoscope may be placed into the third ventricle to visualize the contralateral foramen of Monro. We routinely make a generous septostomy as our last maneuver. The ventricle and subdural space are filled with fluid to eliminate as much air as possible. The bone flap is replaced and the wound is closed in a standard fashion. A video demonstrating this anterior transcallosal expanded transforaminal approach for third ventricle tumors is available (Video 1).

Video 1. Clip showing the anterior transcallosal expanded transforaminal approach for third ventricle tumors. Copyright Aaron A. Cohen-Gadol. Published with permission. Click here to view with Media Player. Click here to view with Quicktime.

Results

Presentation

Twelve patients met our study criteria (Table 1). There were 5 female patients (42%) and 7 male patients (58%) with a mean age of 9 years (range 2–19 years). Nine patients (75%) were Caucasian, 2 (17%) were African American, and 1 (8%) was of Asian descent. The mean follow-up duration for patients was 16 months (range 6–34 months).

TABLE 1:

Summary of 12 patients who underwent the expanded transforaminal approach to the third ventricle*

Case No.Age (yrs), SexPresenting Signs & SymptomsHydrocephalus on PresentationTumor Type & OriginEstimated Tumor Volume (cm3)ComplicationsAdjuvant TherapyExtent of ResectionStatus at Last Follow-Up
12, MCN VII palsy & ptosisno, existing shuntmidbrain fibrillary astrocytoma14.8required shunt revisionyesless than totalno progression at 2 yrs
210, Fknown tumor, headache for 4 mosyesoptic pathway pilocytic astrocytoma20.1nonenoless than totalno progression at 2.5 yrs
34, Flethargy & ataxiano, existing shuntmidbrain pilocytic astrocytoma39.2suffered small thalamic stroke w/ hemiparesis; DI & hypothyroidism; seizurenoless than totalno progression at 2.5 yrs
43.5, Fheadache & lethargyyeshypothalamic rhabdoid glioblastoma39.2panhypopituitarism, injury to fornixnoless than totaldeceased at 6 mosdue to tumor progression
515, Mheadache & nauseayes, required EVDoptic pathway pilocytic astrocytoma61.7severe GI bleed leading to hypotension & multiple infarcts; intracranial hemorrhage due to anticoagulation for DVT requiring evacuation; panhypopituitarismnoless than total (after 2nd op)no progression at 2 yrs, persistent panhypopituitarism
612, Mheadacheyesoptic pathway pilocytic astrocytoma2.4noneyesless than totalno progression at 1.5 yrs
78, Mlethargy & nauseayescraniopharyngioma112.3noneyesless than totalno progression at 1 yr
819, Fhistory of headache, un-responsive in extremis, lethargyyes, required EVDcolloid cyst1.4CSF leak from incisionnogross-totalno recurrence at 1 yr
95, Munresponsive in extremis, lethargyyes, required EVDchoroid plexus papilloma16.1pseudomeningocelenogross-totalno recurrence at 1 yr
1014, Mheadachenooptic pathway pilocytic astrocytoma43.2noneyesless than totalno progression at 6 mos
1110, Masymptomaticyesthird ventricular pilocytic astrocytoma7.4nonenoless than totalno progression at 6 mos
1212, Fheadache & nauseayes, required EVDcraniopharyngioma17.9DI, pseudomeningoceleyesless than totalno progression at 6 mos

DI = diabetes insipidus; DVT = deep venous thrombosis; GI = gastrointestinal.

Most patients presented with symptoms of raised intracranial pressure, specifically headaches with or without emesis but with normal mentation (n = 7, 58%) and lethargy with a history of headaches (n = 5, 42%). Nine patients (75%) had acute hydrocephalus at presentation; 4 (33%) of these patients required placement of an emergency external ventricular drain (EVD). Of the remaining 3 patients who were not found to have acute hydrocephalus at presentation, 2 had existing ventriculoperitoneal shunts. Two patients with large midbrain tumors filling the third ventricle had bilateral oculomotor nerve palsies on presentation.

Perioperative Outcomes and Status at Last Follow-Up

All craniotomies except one were performed on the right side. One patient required a 2-stage resection. Tumor type, origin, and estimated volume for each patient are shown in Table 1. The most common pathology was pilocytic astrocytoma (n = 6, 50%) and the most common origin was the optic pathway/hypothalamic region. The mean tumor volume was 31.3 cm3. Varying degrees of resection were achieved: 2 gross-total (no residual tumor noted on postoperative imaging) and 10 less than total.

Postoperative complications are detailed in Tables 1 and 2. Seven patients suffered a total of 17 complications. Issues related to CSF dynamics were the most common postoperative complication: CSF leakage from the wound (n = 1), temporary pseudomeningoceles (n = 2), new shunts (n = 2), and shunt revisions (n = 1). Four patients developed neuroendocrine complications. Two suffered from temporary diabetes insipidus, while 1 patient's sodium level was overcorrected, leading to hyponatremia and a seizure. The same patient also acquired hypothyroidism requiring chronic supplementation. Two patients sustained a complete loss of hypothalamic-pituitary function with resultant life-long multi-hormone replacement.

TABLE 2:

Complications by category

Category (total)Complications (no.)
CSF-related (6)CSF wound leak (1); pseudomeningocele (2); new shunt (2); shunt revision (1)
neuroendocrine (5)temporary diabetes insipidus (2); hypothyroidism (1); panhypopituitarism (2)
vascular (3)stroke (2); hemorrhage (1)
woundnone
approach-related (1)forniceal injury (1)
non-neurological (2)GI hemorrhage (1); DVT (1)

Three patients developed vascular complications. Two patients suffered strokes, 1 of which (thalamic infarct) was believed to be due to injury or sacrifice of an en passage posterior thalamoperforator coursing through the patient's large midbrain tumor, and the other (multifocal bilateral watershed zone infarcts primarily between the anterior and middle cerebral artery distributions) due to hypotension from a severe postoperative gastrointestinal bleed. The same patient with the gastrointestinal bleed also developed an intracranial hemorrhage along the prior interhemispheric dissection requiring evacuation after undergoing anticoagulation therapy for a lower-extremity deep venous thrombosis. There were no cerebral or deep venous infarctions. The oculomotor palsies in the 2 patients with midbrain tumors were unchanged at last follow-up.

There was one approach-related complication, which occurred in a 3-year-old girl with a third-ventricle rhabdoid glioblastoma that originated from the hypothalamic region. Her ipsilateral (right) fornix was injured due to traction while trying to remove the tumor located in the anterosuperior part of the third ventricle. This injury did not appear to result in any noticeable short-term memory deficit, but formal testing was not performed. This child died of tumor progression 6 months after surgery.

Discussion

In our experience, the “expanded transforaminal” approach is an effective means of resecting pathology that originates in or expands into the third ventricle. This route allows adequate resection in a group of children whose tumors (optic pathway gliomas) are not readily amenable to complete extirpation. This approach has several advantages. It utilizes an existing passageway to the third ventricle—the foramen of Monro—that is often expanded by the tumor or associated hydrocephalus. We use 3 maneuvers that expand the operative corridor through the foramen: 1) coagulation of the choroid plexus; 2) disconnection of the septal vein; and 3) opening the ependyma (choroidal fissure) at the posterior margin of the foramen and medial to the ipsilateral internal cerebral vein. Longitudinal opening of the choroidal fissure allows safer manipulation of the ipsilateral fornix.

Alternative methods of expanding the foramen have been reported previously. Shucart and Stein described expanding the foramen by “gentle pressure with a small blunt dissector in all directions except medially” or by incising the ipsilateral column of the fornix.5 Others have also advocated sectioning the fornix.3,4 Similar to our approach, Türe et al. enlarged the foramen 4–5 mm by opening the choroidal fissure along the taenia fornicis as far as the junction between the anterior septal vein and internal cerebral vein.7 Hirsch et al. sacrificed the thalamostriate vein as a means of increasing the aperture of the foramen posteriorly.2

Transection of the anterior septal vein, which allows medial mobilization of the fornix and lateral retraction of the thalamostriate vein, did not result in any venous complications in our series. We could not find any report in the literature that described a complication with this maneuver. The anterior septal vein courses medially from the tip of the frontal horn, curves posteriorly along the septum pellucidum and over the column of the fornix, and then passes above the foramen of Monro to join the internal cerebral vein.7 Türe et al. described 4 variations of the junction of the anterior septal vein and the internal cerebral vein with respect to the foramen.7 In 80% of their brain specimens, this anastomosis was located beyond the posterior margin of the foramen of Monro. They argued that this posterior location allowed the foramen to be opened along the choroidal fissure without having to sacrifice any venous structures. Dissection through the tela choroidea into the vessel-rich velum interpositum is not necessary with our technique, but is an option if further posterior expansion of the operative corridor is needed.

The most notable limitation to our approach is the restricted view to the anterosuperior and posterosuperior portions of the third ventricle (Fig. 5). Even with a larger opening into the third ventricle through a transchoroidal approach, the columns of the fornix limit direct access to the area of the third ventricle around the anterior commissure.8 If the third ventricle is divided into 3 zones (anterior, middle, and posterior), then our expanded transforaminal approach provides excellent visualization of the anteroinferior part of the anterior zone (the infundibular recess), all of the middle zone, and the posteroinferior aspect of the posterior zone. The anterior view allows the surgeon to perform a direct third ventriculostomy through the tuber cinereum if CSF flow through the cerebral aqueduct cannot be reliably established. The single approach-related injury to the fornix in our patients occurred in an effort to resect tumor in this anterosuperior blind zone. Fortunately, this injury did not appear to result in any obvious functional deficits.

Fig. 5.
Fig. 5.

The cone of view (green) allowed by the expanded transforaminal approach by angling of the microscope. The blind zones (red) for this approach are the anterosuperior and posterosuperior regions of the third ventricle. © The Neurosurgical Atlas, Aaron A. Cohen-Gadol. Used with permission.

Irrespective of the approach used, these patients have a high risk of sustaining a complication (Table 2). We considered a complication as any untoward postoperative event, which some may consider too strict. A postoperative pseudomeningocele, for example, could arguably not be a complication. Nonetheless, 7 of our 12 patients did suffer from a “complication,” with CSF-related being the most common type. Despite the challenges these patients offer surgically and postoperatively, all surviving patients thus far have shown no evidence of disease recurrence or progression after an average follow-up duration of 16 months.

Conclusions

There are several surgical approaches to the third ventricle, each with their own advantages and disadvantages. The expanded transcallosal transforaminal approach is a safe method of exploiting a natural pathway to the third ventricle, but blind zones are located anterosuperiorly and posterosuperiorly. Postoperative issues and complications are high in this patient population, but most are a consequence of the tumor's location as opposed to the surgical approach.

Acknowledgment

We wish to thank Andrew J. Gienapp for technical editing and copyediting, preparation of the manuscript and figures for publishing, and publication assistance with this manuscript.

Disclosure

Dr. Cohen-Gadol has a consulting agreement with Carl Zeiss Meditec. All compensation from this arrangement is donated to a not-for-profit educational project, The Neurosurgical Atlas. Drs. Patel, Boop, and Klimo have no financial relationships to disclose.

Author contributions to the study and manuscript preparation include the following. Conception and design: Klimo, Cohen-Gadol. Acquisition of data: Klimo, Patel. Analysis and interpretation of data: Klimo, Patel. Drafting the article: all authors. Critically revising the article: all authors. Reviewed submitted version of manuscript: all authors. Approved the final version of the manuscript on behalf of all authors: Klimo. Administrative/technical/material support: Cohen-Gadol. Study supervision: Klimo, Cohen-Gadol.

References

  • 1

    Cossu MLubinu FOrunesu GPau ASehrbundt Viale ESini MG: Subchoroidal approach to the third ventricle. Microsurgical anatomy. Surg Neurol 21:3253311984

    • Search Google Scholar
    • Export Citation
  • 2

    Hirsch JFZouaoui ARenier DPierre-Kahn A: A new surgical approach to the third ventricle with interruption of the striothalamic vein. Acta Neurochir (Wien) 47:1351471979

    • Search Google Scholar
    • Export Citation
  • 3

    Little JRMacCarty CS: Colloid cysts of the third ventricle. J Neurosurg 40:2302351974

  • 4

    Morita AKelly PJ: Resection of intraventricular tumors via a computer-assisted volumetric stereotactic approach. Neurosurgery 32:9209271993

    • Search Google Scholar
    • Export Citation
  • 5

    Shucart WAStein BM: Transcallosal approach to the anterior ventricular system. Neurosurgery 3:3393431978

  • 6

    Silva PSCerejo APolónia PPereira JVaz R: Trans-lamina terminalis approach for third ventricle and suprasellar tumours. Clin Neurol Neurosurg 115:174517522013

    • Search Google Scholar
    • Export Citation
  • 7

    Türe UYaşargil MGAl-Mefty O: The transcallosal-transforaminal approach to the third ventricle with regard to the venous variations in this region. J Neurosurg 87:7067151997

    • Search Google Scholar
    • Export Citation
  • 8

    Ulm AJRusso AAlbanese ETanriover NMartins CMericle RM: Limitations of the transcallosal transchoroidal approach to the third ventricle. Technical note. J Neurosurg 111:6006092009

    • Search Google Scholar
    • Export Citation
  • 9

    Wen HTRhoton AL Jrde Oliveira E: Transchoroidal approach to the third ventricle: an anatomic study of the choroidal fissure and its clinical application. Neurosurgery 42:120512191998

    • Search Google Scholar
    • Export Citation
  • 10

    Winkler PAIlmberger JKrishnan KGReulen HJ: Transcallosal interforniceal-transforaminal approach for removing lesions occupying the third ventricular space: clinical and neuropsychological results. Neurosurgery 46:8798902000

    • Search Google Scholar
    • Export Citation

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Article Information

Address correspondence to: Paul Klimo Jr., M.D., M.P.H., Semmes-Murphey Neurologic & Spine Institute, 6325 Humphreys Blvd., Memphis, TN 38120. email: pklimo@semmes-murphey.com.

Please include this information when citing this paper: published online August 8, 2014; DOI: 10.3171/2014.6.PEDS1452.

© AANS, except where prohibited by US copyright law.

Headings

Figures

  • View in gallery

    Illustrations of the third ventricle. The third ventricle is bordered anteriorly by the lamina terminalis and anterior commissure, laterally by the thalami, inferiorly by diencephalic structures anteriorly and the mesencephalon posteriorly, superiorly by the foramina of Monro and the tela choroidea/velum interpositum (with the internal cerebral veins), and posteriorly by multiple structures including the suprapineal recess, habenular commissure, pineal body and pineal recess, posterior commissure, and aqueduct of Sylvius (A). The thalamostriate vein picks up a number of draining veins as it flows toward the venous angle, where it is joined by the anterior septal vein (B). Coronal and sagittal views show a mass within the anterior third ventricle (C and D). © The Neurosurgical Atlas, Aaron A. Cohen-Gadol. Used with permission.

  • View in gallery

    Positioning and planning of the skin incision (dashed red line) and underlying bone flap (solid black line). The craniotomy may be centered over or just anterior to the coronal suture. © The Neurosurgical Atlas, Aaron A. Cohen-Gadol. Used with permission.

  • View in gallery

    Maneuvers to expand the foramen of Monro. A: Coagulation of a small amount of choroid plexus as it enters the foramen. B: Coagulation of the septal vein, which allows gentle medial retraction of the septum and fornix without risk of avulsion. C: Further dissection of the taenia fornicis at the posterior aspect of the foramen toward the velum interpositum. © The Neurosurgical Atlas, Aaron A. Cohen-Gadol. Used with permission.

  • View in gallery

    Illustrations showing resection of the mass through the expanded foramen of Monro. © The Neurosurgical Atlas, Aaron A. Cohen-Gadol. Used with permission.

  • View in gallery

    The cone of view (green) allowed by the expanded transforaminal approach by angling of the microscope. The blind zones (red) for this approach are the anterosuperior and posterosuperior regions of the third ventricle. © The Neurosurgical Atlas, Aaron A. Cohen-Gadol. Used with permission.

References

  • 1

    Cossu MLubinu FOrunesu GPau ASehrbundt Viale ESini MG: Subchoroidal approach to the third ventricle. Microsurgical anatomy. Surg Neurol 21:3253311984

    • Search Google Scholar
    • Export Citation
  • 2

    Hirsch JFZouaoui ARenier DPierre-Kahn A: A new surgical approach to the third ventricle with interruption of the striothalamic vein. Acta Neurochir (Wien) 47:1351471979

    • Search Google Scholar
    • Export Citation
  • 3

    Little JRMacCarty CS: Colloid cysts of the third ventricle. J Neurosurg 40:2302351974

  • 4

    Morita AKelly PJ: Resection of intraventricular tumors via a computer-assisted volumetric stereotactic approach. Neurosurgery 32:9209271993

    • Search Google Scholar
    • Export Citation
  • 5

    Shucart WAStein BM: Transcallosal approach to the anterior ventricular system. Neurosurgery 3:3393431978

  • 6

    Silva PSCerejo APolónia PPereira JVaz R: Trans-lamina terminalis approach for third ventricle and suprasellar tumours. Clin Neurol Neurosurg 115:174517522013

    • Search Google Scholar
    • Export Citation
  • 7

    Türe UYaşargil MGAl-Mefty O: The transcallosal-transforaminal approach to the third ventricle with regard to the venous variations in this region. J Neurosurg 87:7067151997

    • Search Google Scholar
    • Export Citation
  • 8

    Ulm AJRusso AAlbanese ETanriover NMartins CMericle RM: Limitations of the transcallosal transchoroidal approach to the third ventricle. Technical note. J Neurosurg 111:6006092009

    • Search Google Scholar
    • Export Citation
  • 9

    Wen HTRhoton AL Jrde Oliveira E: Transchoroidal approach to the third ventricle: an anatomic study of the choroidal fissure and its clinical application. Neurosurgery 42:120512191998

    • Search Google Scholar
    • Export Citation
  • 10

    Winkler PAIlmberger JKrishnan KGReulen HJ: Transcallosal interforniceal-transforaminal approach for removing lesions occupying the third ventricular space: clinical and neuropsychological results. Neurosurgery 46:8798902000

    • Search Google Scholar
    • Export Citation

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