Original Article

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Microsurgical and Endoscopic Posterior Transcortical Keyhole Approach to the Atrium of the Lateral Ventricle: A Cadaveric Study Lin Yang3

Hengzhu Zhang1

1 Department of Neurosurgery, Clinical Medical College of Yangzhou

University, Yangzhou, Jiangsu, China 2 Department of Neurosurgery, The Second Affiliated Hospital of Soochow University, Suzhou, Jiangsu, China 3 Department of Neurosurgery, Yizheng People’s Hospital, Yizheng, Jiangsu, China

Zhengcun Yan1

Lei She1

Address for correspondence Hengzhu Zhang, MD, PhD, Department of Neurosurgery, Clinical Medical College of Yangzhou University, 98 Nantong West Road, Yangzhou, Jiangsu 225001, China (e-mail: [email protected]).

J Neurol Surg A 2014;76:261–267.

Abstract

Keywords

► atrium of the lateral ventricle ► approach ► endoscope ► keyhole ► microscope

received October 31, 2013 accepted after revision May 21, 2014 published online January 16, 2015

Objective Accessing large lesions located in the atrium of the lateral ventricle without causing a neurologic deficit can be challenging. The aim of this study was to evaluate a modification of the posterior transcortical approach that may create sufficient exposure to the atrium of the lateral ventricle with less injury to the brain cortex and fibers using a technique that combines a microscope with an endoscope. Material and Methods Craniotomy procedures performed using the posterior transcortical keyhole approach were simulated on 10 adult cadaveric heads (20 hemispheres). The anatomical structures in the lateral ventricle were observed through the microscope and endoscope. Three distance measurements on the intraparietal sulcus were recorded. Results The anatomical structures related to the atrium of the lateral ventricle, including the calcar avis, corpus callosum bulb, caudate nucleus, pulvinar, and glomus, were clearly observed under the microscope. Via the endoscope, a wider visualization of anatomical structures could be obtained. The distance from the intersection of the intraparietal sulcus and postcentral sulcus to the cerebral longitudinal fissure was 35.36  1.06 mm, the depth of the intraparietal sulcus was 19.16  1.03 mm, and the distance from the bottom of the intraparietal sulcus to the lateral ventricle was 21.31  1.32 mm. Conclusions The microsurgical posterior transcortical keyhole approach could provide an ideal exposure to the atrium and the posterior part of the body of the lateral ventricle. The endoscopic posterior transcortical keyhole approach demonstrated a wider viewing range compared with the microscope. An endoscopic-controlled or -assisted surgery may reduce damage to normal brain tissue, facilitate total resection of the lesion, and improve the surgical outcome.

© 2015 Georg Thieme Verlag KG Stuttgart · New York

DOI http://dx.doi.org/ 10.1055/s-0034-1393928. ISSN 2193-6315.

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Xiaodong Wang1,2

Alternative Approach to Atrium of the Lateral Ventricle

Introduction

Wang et al. Table 1 Measurement data on the intraparietal sulcus (left/right)

A direct approach to the atrium of the lateral ventricle (LV) remains a challenge because of its deep location, the important surrounding neurovascular structures, and its deep venous system.1 That challenge has resulted in the development of various operative approaches: anterior, posterior, lateral, and inferior.2 Each of them has specific advantages and disadvantages.1 Some controversy exists regarding the appropriate approach to lesions in this region.3–5 One focus of attention is how to maximally preserve normal functions of the brain cortex and fibers as well as obtain a maximum lesion resection. The aim of this study was to evaluate a modification of the posterior transcortical approach that might create sufficient exposure to the atrium of the LV with less injury to the brain cortex and fibers using the technique of a microscope combined with an endoscope.

Material and Methods This study was performed on 10 formalin-fixed adult human head specimens (20 hemispheres), whose deaths were not caused by brain disease. All procedures were performed in the anatomy laboratory of Yangzhou University without any conflict of ethics. The laboratory equipment included a microscope (Leica), a 0-degree endoscope (Storz), microsurgical instruments, self-retaining retractor system, a headholder, a digital camera, a vernier caliper, and a video system. Each head specimen was fixed in the headholder. A 40-mm straight skin incision, 35 mm parallel to the midline, was created, and its lower edge was 50 mm above the external occipital carina, based on the findings of Ribas et al.6 The subgaleal and periosteal areas were separated by a mastoid distractor, and then a small bone opening 30 mm in diameter was made. Next, the dura mater was opened and the intraparietal sulcus identified. A 25-mm cortex incision was made in the intraparietal sulcus, and the trigone of the LV was entered. The anatomical structures in the LV were observed through the microscope and endoscope. Three distance measurements were recorded: the distance from the intersection of the intraparietal sulcus and postcentral sulcus (IISPS) to the cerebral longitudinal fissure (CLF), the depth of the intraparietal sulcus (DIS), and the distance from the bottom of the intraparietal sulcus (BIS) to the LV. The data were summarized by the mean plus or minus the standard deviation.

Specimens

IISPS to CLF, mm

DIS, mm

BIS to LV, mm

1

35.68/35.10

19.70/20.10

21.82/21.20

2

35.30/36.40

19.20/20.82

21.80/22.60

3

34.20/35.22

18.32/17.20

20.52/19.20

4

34.30/33.50

18.72/18.18

19.60/20.48

5

35.56/36.48

19.50/19.12

20.32/21.78

6

36.64/35.68

20.38/18.10

23.20/21.90

7

36.38/35.10

20.12/19.58

22.58/23.10

8

33.46/35.00

17.90/18.12

19.36/20.10

9

37.48/36.26

21.10/19.28

23.82/21.28

10

35.16/34.34

19.18/18.60

21.16/20.40

Mean

35.36

19.16

21.31

Abbreviations: BIS, bottom of the intraparietal sulcus; CLF, cerebral longitudinal fissure; DIS, depth of the intraparietal sulcus; IISPS, intersection of the intraparietal sulcus and postcentral sulcus; LV, lateral ventricle.

LV above the thalamus, anteriorly into the temporal horn below the thalamus, and posteriorly into the occipital horn. The floor of the atrium is formed by the collateral trigone. Anteriorly, the crus of the fornix and the pulvinar were seen. The medial wall is formed by the calcar avis (inferior) and the corpus callosum bulb (superior). The lateral wall is formed by the caudate nucleus, which circles around the pulvinar thalami. A prominent tuft of the choroid plexus is the glomus. There is no choroid plexus in the occipital horn (►Figs. 1–6). Through the same surgical corridor, the 0-degree endoscope was introduced into the LV. Owing to the wider visual

Results The mean distance from the IISPS to CLF was 35.36  1.06 mm, DIS was 19.16  1.03 mm, and BIS to LV was 21.31  1.32 mm (►Table 1). All 20 procedures were performed successfully. Blunt dissection through the bottom of the intraparietal sulcus was performed to reach the atrium of the LV, and two selfretaining retractors were placed to keep the corridor open. Using the microscope, the following anatomical aspects were visualized: the atrium of LV opens anteriorly into the body of Journal of Neurological Surgery—Part A

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Fig. 1 External occipital carina (inion). The intersection of the lambdoid suture (La) and the sagittal (Sa) suture (50 mm above the inion) were marked on the midline.

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Wang et al.

Fig. 2 A small bone window 30 mm in diameter. Fig. 4 After cutting the cortex at the bottom of the intraparietal cortex into the atrium of the lateral ventricle, the following structures were observed by microscope: the choroid plexus between the temporal horn (TH) and the body of the lateral ventricle (BLV), glomus (Gl), collateral trigone (CT), occipital horn (OH), calcar avis (CA), and corpus callosum (CC).

Fig. 3 The intraparietal sulcus (IPS) was revealed after the dura mater was cut.

to most lesions in the atrium. However, these approaches may cause a language dysfunction or homonymous visual field deficit because of an interruption of the corresponding brain function area.1,8,10 During the past decades, several novel approaches have been developed including the posterior transcallosal approach,1 posterior interhemispheric transprecuneus approach,11 posterior interhemispheric transfalx transprecuneus approach,12 and supracerebellar transtentorial transcollateral sulcus approach2 that can avoid injury to the optic radiation. However, these approaches have several disadvantages including a narrow working angle and surgical corridor, and the obstacle of bridging veins and venous sinuses.2,12 Moreover, the safety and efficacy of

angle, more anatomical structures were observed including the superior choroidal vein on the surface of the choroid plexus, the choroid fissure, and the body of the fornix in the direction of the body of LV. In addition, in the direction of the temporal horn, the exterior area of the collateral trigone, the border of the fimbria fornicis, and the body of the fornix could be seen (►Figs. 7–10).

Discussion Neoplastic or vascular lesions in the atrium of LV are challenging for neurosurgeons because of their deep-seated nature, varied histologic characteristics, and surrounding eloquent structures. Many approaches to the atrium have been reported.1,4,5,7–9 The common approaches include the temporal transcortical route, lateral temporoparietal route, and parietal transcortical route, which enable a direct access

Fig. 5 After the choroid plexus (CP) was retracted, the following structures were observed: the choroid fissure (CF), fornix (Fo), pulvinar (Pu), and calcar avis (CA). Journal of Neurological Surgery—Part A

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Alternative Approach to Atrium of the Lateral Ventricle

Alternative Approach to Atrium of the Lateral Ventricle

Fig. 6 Structures of the trigone of the lateral ventricle: the glomus (Gl), collateral trigone (CT), pulvinar (Pu), calcar avis (CA), and occipital horn (OH). TH, temporal horn.

Fig. 7 Observing the atrium of the lateral ventricle with the endoscope: the temporal horn (TH), body of the lateral ventricle (BLV), glomus (Gl), collateral trigone (CT), occipital horn (OH), and calcar avis (CA).

Fig. 8 Turning the endoscope to the body of the lateral ventricle (BLV) and observing the following: the fornix (Fo), corpus callosum (CC), calcar avis (CA), choroid plexus (CP), and choroid fissure (CF). Journal of Neurological Surgery—Part A

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Fig. 9 The temporal horn (TH), body of the lateral ventricle (BLV), glomus (Gl), collateral trigone (CT), occipital horn (OH), and calcar avis (CA).

Fig. 10 Turning the neuroendoscope to the temporal horn (TH) provided a larger range than using the microscope: the glomus (Gl), collateral trigone (CT), and pulvinar (Pu).

these approaches have not been demonstrated by larger clinical series. Up to now, the parietal transcortical approach has been the most popular route to the atrium, especially for some large and solid tumors.1,13 This approach is a preferred choice for many surgeons because of a straight corridor, sufficient exposure of the lesion, and its easily mastered nature. The tremendous progress of minimally invasive surgical techniques and instruments has reduced the incidence of postoperative complications. One study reviewed the results and clinical outcome of 20 patients with surgically treated lesions within the trigone of the LV. Surgical removal was achieved via the transcortical parietal route in 13 cases. All tumors were completely removed, nine cases improved, and only one case had a new postoperative visual field disturbance.14 Another series reported 13 patients who underwent resection of intraventricular meningiomas. Five patients underwent transparietal tumor resections; two developed temporary postoperative cognitive deficits and one developed a new visual field deficit after surgery.10 According to

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Kawashima et al, the medial and inferior walls of the atrium are free from optic radiation fibers, and the cortical incision of the superior parietal lobule avoids the visual pathway traversing the parietal lobe and the speech area at the junction of the parietal and temporal lobes.1 We developed a small cortical incision (25 mm) in the intraparietal sulcus that theoretically avoided damage to the visual and speech areas. Ribas and colleagues reported that in most cases, the intraparietal sulcus is continuous from the inferior part of the postcentral sulcus and nearly parallel to the cerebral longitudinal fissure.6 Because of its relatively constant position, using the intersection of the intraparietal sulcus and the postcentral sulcus to accurately localize the intraparietal sulcus could be a good choice. The results of our study demonstrated that the atrium of the LV was ideally visualized via the intraparietal sulcus transcortical approach. Since their introduction, endoscopic techniques have advanced considerably beyond their initial use in obstructive hydrocephalus.15 Compared with the microscope, the endoscope has advantages including the minimally invasive corridor, deep illumination, and more angles of view that permit the surgeon to see into spaces outside the line of sight available with traditional microsurgical techniques, to look around surgical corners, and to improve illumination and magnification in deep cavities, all theoretically facilitating maximal tumor resection.16,17 Hopf and Perneczky proposed a classification of the use of the endoscope into three major groups: purely endoscopic neurosurgery, endoscope-controlled microneurosurgery, and endoscope-assisted microneurosurgery.18 Another publication classified endoscopic surgeries into intra- and extraaxial procedures depending on the relationship between surgical instruments and the endoscope.19 The purely endoscopic neurosurgery, or intra-axial endoscopic technique, has its limits in the removal of solid intraventricular tumors because of limited surgical freedom and the difficulty of controlling tumor bleeding. Endoscope-controlled and endoscope-assisted microneurosurgery have been widely used as an effective way to perform pituitary and extended skull base surgeries in neurosurgery.20–24 However, there are very few reports about the endoscopic resection of tumors in the LV.15,25 In fact, in regard to the deep and multicavity nature of the LV, the endoscope provides an alternative way to treat the lesions in this region surgically. In our study, a wider viewing range and visualization of more anatomical details were achieved with the endoscope without excessive retraction of normal brain tissue. When the endoscope was introduced into the LV, the typical choroid plexus ball of the triangle area was observed that could be used as a landmark to confirm that the endoscope has entered the LV. Along the choroid plexus ball, we could further observe the temporal horn, body, front corner, and blood vessels of the LV. In the case of the larger LV, through the endoscope, we could see the interventricular foramen, the head of the caudate nucleus in the lateral wall of the frontal horn, and the septal and thalamostriate vein. The space of the atrium is usually sufficient to observe and treat lesions via the endoscope. However, if the LV is too narrow, improper

Wang et al.

Fig. 11 Preoperative T1-weighted magnetic resonance imaging, gadolinium enhanced, showing a 20-mm mass in the atrium of the left lateral ventricle.

endoscopic operation may cause damage to the surrounding blood vessels of the thalamus and choroid plexus. According to our study, the following surgical strategies may be explored: 1. The posterior transcortical keyhole approach provides a short access to the atrium of the LV by cutting the cortex at the bottom of the intraparietal sulcus. The combination of microscopic and endoscopic techniques may further shorten the cortical incision and reduce brain retraction, which can reduce the incidence of postoperative complications. 2. The approach is suited to treat large and solid lesions within the atrium and the posterior part of the body of the LV. It may also be selected for a lesion involving the posterior third ventricle or the anterior part of the body of the LV if the LV is dilated.

Fig. 12 T1-weighted, gadolinium-enhanced magnetic resonance imaging 18 days after surgery. No residual tumor is seen. Journal of Neurological Surgery—Part A

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Alternative Approach to Atrium of the Lateral Ventricle

Alternative Approach to Atrium of the Lateral Ventricle 3. For poorly vascularized tumors, endoscope-controlled neurosurgery could be performed, meaning a shorter cortical incision. 4. For highly vascularized tumors, microsurgery assisted by the endoscope could be chosen that could help save operation time. The endoscope can be used to observe the surrounding and feeding vessels of the tumor, and to confirm whether residual tumor or occult bleeding exists. The endoscope plays an important role in the deep LV at the moment when “looking around a corner” is required.26 The main disadvantage of the present approach is late access to the blood supply. Fortunately, according to several clinical series, piecemeal removal allowed safe debulking without excessive bleeding in most cases until the tumor could be mobilized to expose and coagulate the feeding vessels,14 suggesting that early access to the tumor’s blood supply might not be necessary.10 Another possible drawback is that this approach still has a potential risk of visual field deficit or epilepsy. To increase the safety of the surgery, neuronavigation, intraoperative diffusion tensor imaging,27 and electrophysiology are quite helpful. Note that the trajectory of this approach usually has to be anteriorly oriented, neither laterally nor medially, and should be planned according to the neuroimaging findings of each patient and can be properly oriented with the aid of intraoperative ultrasonography.

Wang et al. References 1 Kawashima M, Li X, Rhoton AL Jr, Ulm AJ, Oka H, Fujii K. Surgical

2

3

4 5 6

7

8 9

10

11

A Clinically Applied Case A 59-year-old woman presented with a half-year history of intermittent dizziness. Neurologic examination did not reveal any deficit. Magnetic resonance imaging (MRI) showed a well-circumscribed enhancing mass that was 20 mm in diameter in the left atrium (►Fig. 11). A microsurgical posterior transcortical keyhole approach through the intraparietal sulcus was chosen to remove the lesion. Postoperatively, the patient experienced no other complications, except a temporary homonymous hemianopia that disappeared 5 days after the operation. The pathologic result was meningoma (grade 1), and 18 days later, an MRI scan demonstrated no residual tumor (►Fig. 12).

13

14

15

16

Conclusion The microsurgical posterior transcortical keyhole approach could provide an ideal exposure for the atrium and the posterior part of the body of the LV. The endoscopic posterior transcortical keyhole approach has a wider viewing range compared with the microscope. Through this approach, an endoscope-controlled or -assisted surgery may reduce damage to normal brain tissue, facilitate total resection of the lesion, and improve the surgical outcome. The safety and efficacy of this approach should be demonstrated by more clinical studies. Conflict of Interest The authors have nothing to disclose.

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Microsurgical and Endoscopic Posterior Transcortical Keyhole Approach to the Atrium of the Lateral Ventricle: A Cadaveric Study.

Accessing large lesions located in the atrium of the lateral ventricle without causing a neurologic deficit can be challenging. The aim of this study ...
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