- Department of Neurosurgery, PLA Navy General Hospital, Beijing, China
- Department of Surgery, Division of Neurosurgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA
Ekkehard M. Kasper
Department of Surgery, Division of Neurosurgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA
DOI:10.4103/2152-7806.126081Copyright: © 2014 Liu R. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
How to cite this article: Liu R, Kasper EM. Bilateral telovelar approach: A safe route revisited for resections of various large fourth ventricle tumors. Surg Neurol Int 30-Jan-2014;5:16
How to cite this URL: Liu R, Kasper EM. Bilateral telovelar approach: A safe route revisited for resections of various large fourth ventricle tumors. Surg Neurol Int 30-Jan-2014;5:16. Available from: http://sni.wpengine.com/surgicalint_articles/bilateral-telovelar-approach-a-safe-route-revisited-for-resections-of-various-large-fourth-ventricle-tumors/
Background:Tumors located in the posterior fossa and especially in the middle and upper fourth ventricle are comparatively rare and technically very challenging. For some lesions, the telovelar approach has been shown to be a suitable approach. The unilateral approach is sufficient in most cases of small lesions. However, large fourth ventricle tumors are more problematic since they distort the normal anatomy with both vermis and cerebellar peduncles thinned and stretched out. This puts the patient at increased risk for a neurological deficit, which is minimized with a bilateral telovelar approach. By illustrating the adequacy of this technique, we emphasize the suitability of a rather unusual bilateral approach, which will provide excellent panoramic visualization of entire fourth ventricle and thus avoids complications usually associated with resections of large fourth ventricle tumors.
Case Description:Here we present three cases of benign intraventricular tumors (meningioma, solitary fibrous tumor and ependymoma) in patients with site specific symptoms from local mass effect. Typical symptoms of posterior fossa lesions were present preoperatively and resolved after surgery. The bilateral telovelar approach was used to remove these tumors completely and the pertinent intraoperative steps are described for each case. All three patients had excellent postoperative outcome and could be discharged after short hospital stays.
Conclusion:The different pathological entities could be completely resected without added neurological deficit employing a bilateral approach. In cases of large or giant fourth ventricle tumors, the bilateral telovelar approach provides excellent intraoperative visibility allowing complete excision of extensive tumors with minimal morbidity.
Keywords: Cerebellomedullary fissure, fourth ventricle, microsurgery, telovelar approach
Tumors located deep in the posterior fossa and especially in the middle and upper fourth ventricle are challenging to most neurosurgeons. Especially exhilarating are large fourth ventricle tumors that extend as far as the cerebral aqueduct or grow via the lateral recess toward the cerebellopontine angle, protruding out of the foramina Luschkae and possibly posteriorly through the foramen Magendie.
In the past, traditional approaches involved splitting the inferior vermis to gain better direct access from posteriorly to the fourth ventricle. However, this surgical approach inflicts not insignificant damage to the midline cerebellar structures and has been implicated in the development of postoperative “cerebellar mutism syndromes”. In 1982, Matsushima described a new technique utilizing the natural tissue planes to gain ample access to the fourth ventricle and to expose even large lesions.[
Here we present three such tumor cases, which are extremely rare and technically very challenging, even more so with very large masses originating in the fourth ventricle. The bilateral telovelar approach was used as our access route to remove the differing tumors completely and no neurological deterioration was observed after the operation. By illustrating the adequacy of this important operative technique, we attempt to emphasize the suitability of a rather unusual bilateral approach, which will provide excellent panoramic visualization of entire fourth ventricle and thus helps in avoiding potential complications usually associated with resections of large fourth ventricle tumors.
Patient 1 (Meningioma WHO II)
A 60-year-old male presented with progressive paraparesis and intractable headaches. The patient was known to suffer from neurofibromatosis type 2, and already had multiple meningiomas removed in the past. Magnetic resonance imaging (MRI) with I/V contrast revealed an oval shaped, partially cystic but homogeneously contrast enhancing, well demarcated tumor, which reached from the mid fourth ventricle to the aqueducts Sylvii mesencephali. The tumor extended also into the lateral recess [
For surgery, the patient underwent standard general endotracheal anesthesia and was placed into prone position in Mayfield 3-point skeletal fixation. He was resting on a Wilson frame with the neck in a highly flexed position. The Brain-LAB navigation system was used and fiducials were registered. Landmarks such as the superior sagittal sinus were marked and best trajectories were visualized. A standard bilateral suboccipital approach was chosen and the incision was carried out at the midline, starting about 3 cm above the inion and reaching down to the level of the C2 spinous process. A chiari-type bilateral suboccipital craniectomy was performed using a high-speed craniotome, thus achieving a bone window spanning high from near the inion to the foramen magnum. The margin of the bone flap was extended laterally to expose the sigmoid sinus. The posterior arch of C1 was resected bilaterally up to the sulcus arteriosus of the lateral mass. The best approach-angle was confirmed according to Brain-LAB criteria. A y-shaped durotomy was performed and the dural leaves where tagged up with 4-0 Nurolon (Ethicon) to expose the underlying cerebellum. The pia was transected and cerebrospinal fluid (CSF) was removed. Arachnoidal adhesions were lyzed. We then used a Greenberg retractor and both tonsils were gently retracted upwards and outwards under the microscope, after opening the bilateral cerebellomedullary fissures to gain access to the fourth ventricle. The floor of each cerebellomedullary fissure, composed by tela choroidea and inferior medullary velum, was exposed. Then the bilateral tela choroideae, lucent membranes covering the fourth ventricle around the foramen of Magendie, were opened with microinstruments to visualize and access the posterior-superior part of the fourth ventricle. Using this approach, an inferior vermian split was avoided and the caudal vermis could be easily elevated. Both the Posterior inferior cerebellar artery (PICAs) and the veins of each cerebellomedullary fissure were preserved. Tumorous tissue lodged in the fourth ventricle was immediately encountered and identified when looking from the obex superiorly. A small specimen was obtained upfront for intraoperative fresh frozen histopathological analysis.
In patient number 1, this revealed the diagnosis of a meningioma with some atypical features. Careful microscopic dissection in a circumferential plane and internal debulking were performed alternately. Cutting the margin of the inferior medullary velum on each side created a wide operative field allowing panoramic views superiorly toward the mesencephalic aqueduct as well as laterally toward the foramina Luschkae. At the end of the tumor dissection and its gross total removal, the caudal aqueductal opening and CSF egress via the bilateral foramina of Luschkae was seen. After absolute hemostasis was achieved, the ventricle was copiously irrigated until the irrigant remained clear and the durotomy was closed with a pericranial autograft. The latter was sutured in with a running 4-0 Nurolon stitch and augmented by a fibrin tissue sealant. The wound was closed in layers. The patient was kept intubated until imaging and the postoperative magnetic resonance image (MRI) revealed no residual tumor burden [
Patient 2 (Solitary fibrous tumor of the central nervous system)
A 2-year-old girl presented with slight headache and gait disturbances, which had developed over the month prior to admission. MRI with contrast enhancement showed an irregularly shaped, avidly enhancing tumor mass, measuring about 40 mm in diameter and located in fourth ventricle. There was rostral extension into the cerebral aqueduct and also extension into the lateral recess accompanied by obstructive hydrocephalus [
Patient 3 (Ependymoma WHO II)
A 72-year-old male presented with progressive nausea, occasional vomiting, and intractable morning headaches. The patient had an unremarkable past medical history and was treated by his primary care physician for a stomach bug for several weeks.
Eventually, imaging was requested for non-resolving symptoms and MRI with I/V contrast revealed a multilobulated, irregularly shaped, partially cystic but avidly contrast enhancing, mostly well demarcated tumor, which reached from within the mid fourth ventricle posteriorly toward the inferior velum and laterally into the recess of the fourth ventricle [
Preoperative axial T1 (a), axial T2 (b) and axial (c), coronal (d) and sagittal (e) with Gd-DTPA MRI scan showing a fourth ventricle tumor enclosed posterior inferior cerebellar artery. Postoperative axial T1 (f), axial T2 (g) and axial (h), coronal (i) and sagittal (j) with Gd-DTPA MRI scan demonstrating total resection and reserving posterior inferior cerebellar artery.
As for patient 1, this patient underwent standard general endotracheal anesthesia and was placed into prone position in Mayfield fixation pins with the neck in a highly flexed position. The Brain-LAB system was used and best trajectories were determined. A standard wide bilateral suboccipital approach was chosen. Durotomy was performed as described earlier and the arachnoidea was dissected off. The tonsils were retracted, the cerebellomedullary (CM) fissure split and the tela choroidea was opened on both sides to access the posterior-lateral part of the fourth ventricle. Both PICAs were immediately visualized and could be dissected of the tumor mass and the veins of the cerebellomedullary fissure could also be preserved. Tumor tissue in the fourth ventricle was readily identified and some of the left sided cystic portions of the lesion could be accessed and drained, which greatly facilitated our dissection. A small specimen for intraoperative histopathological analysis revealed a well differentiated ependymoma. Careful microscopic dissection in a circumferential plane was performed. Cutting the juncture of the tela and inferior medullary velum on each side created a wide operative field allowing bilaterally panoramic views especially laterally toward the recess. After gross total resection, brisk CSF flow from the aqueduct and through the foramina Luschkae was observed. Absolute hemostasis was achieved, the ventricle was copiously irrigated and the durotomy was closed as described earlier with pericranial autograft and fibrin sealant augmentation. The patient was successfully extubated in the OR and no neurological deficit was noticed upon examination. Postoperative MRI revealed no residual tumor burden [
Approaches to large tumors in fourth ventricle can be a formidable challenge to even experienced neurosurgeons. Since Dandy's original statement regarding the splitting of the cerebellar vermis (claiming that this could be achieved without significant disturbance in function)[
This unique approach accesses the fourth ventricle through natural openings in the inferior portion of the roof of the fourth ventricle, utilizing tissue planes formed by the inferior medullary velum and the tela choroidea during embryogenesis: The inferior medullary velum is a thin bilateral layer of neural tissue that extends from the cerebellar nodule medially and blends into the dorsal margin of each lateral recess, forming the peduncle of each flocculus laterally. Caudally and laterally, the inferior medullary velum attaches to the tela choroidea ventriculi quarti. The tela choroidea contains a vascular layer of choroidal arteries and veins between its layers and the choroid plexus projects from its ventricular surface. Most importantly, no known functional neural tissue or pathway resides within these structures that form the inferior portion of the roof of the fourth ventricle.[
However, despite all advantages listed and even with all possible intraoperative precautions implemented, some profound neurological sequelae have been reported, including substantial syndromes of cerebellar dysfunction, especially when attempts were made to resect large fourth ventricle tumors via a unilateral telovelar approach.[
To this end, we reported here three different large fourth ventricle tumors extending into the cerebral aqueduct and into the lateral recess. These tumors were resectable via a bilateral telovelar approach without noticeable complications. Although large fourth ventricle tumors often distort the normal anatomy, stretching out the vermis and the cerebellar peduncles are usually thinned, these need to be spared any further injury by minimizing traction. During the operation, a most careful dissection of the circumferential planes and internal debulking of tumor mass were performed alternately. Opening of the bilateral tela choroidea and gentle elevation of the inferior medullary velum did provide enough space to allow an excellent view into the operative site and thus enabled us to completely resect these extensive tumors without injury to adjacent normal tissue. We therefore want to bring this technical aspect again to the attention of dedicated tumor surgeons encountering such challenging lesions in select patients.
In cases of large or giant fourth ventricle tumors of different histopathological types, (such as meningiomas, solitary fibrous tumors or ependymomas but also other neoplasms arising in or from the choroid plexus) the bilateral telovelar approach provides excellent intraoperative visibility via a wide exposure of the fourth ventricle allowing complete excision of even extensive tumors and minimizes surgical morbidity.
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