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Minimally-invasive trans-sulcal resection of Intra-ventricular and Peri-ventricular lesions through a tubular retractor system: Multi-centric experience and results
Javed Khader Eliyas, Ryan Glynn, Charles G. Kulwin, Richard Rovin, Ronald Young, Juan Alzate, Gustavo Pradilla, Mitesh V. Shah, MD, Amin Kassam, Ivan Ciric, Julian Bailes
PII: S1878-8750(16)00104-2
DOI: 10.1016/j.wneu.2015.12.100
Reference: WNEU 3622
To appear in: World Neurosurgery
Received Date: 30 October 2015
Revised Date: 29 December 2015
Accepted Date: 30 December 2015
Please cite this article as: Eliyas JK, Glynn R, Kulwin CG, Rovin R, Young R, Alzate J, Pradilla G, Shah MV, Kassam A, Ciric I, Bailes J, Minimally-invasive trans-sulcal resection of Intra-ventricular and Peri-ventricular lesions through a tubular retractor system: Multi-centric experience and results, World Neurosurgery (2016), doi: 10.1016/j.wneu.2015.12.100.
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Minimally-invasive trans-sulcal resection of Intra-ventricular and Peri-ventricular lesions through a tubular retractor system: Multi-centric experience and results.
Javed Khader Eliyas1'2, Ryan Glynn3, Charles G Kulwin4'5, Richard Rovin6, Ronald Young3'4,
7 8 4 5 6 2
Juan Alzate , Gustavo Pradilla , Mitesh V Shah , , MD; Amin Kassam , Ivan Ciric and Julian Bailes1,2
1Section of Neurosurgery, University of Chicago, Chicago, IL, USA; 2Department of Neurosurgery, NorthShore University Health System, Evanston, IL, USA; 3Chicago Medical School, Rosalind Franklin University, Chicago, IL, USA; 4Department of Neurosurgery, Indiana University, Indianapolis, USA; 5Goodman Campbell Brain and Spine, Indianapolis, USA; 6Aurora Neuroscience Center, Milwaukee, WI, USA; 7American Center for Spine and Neurosurgery, Chicago, IL, USA; 8Department of Neurosurgery, Emory University, Atlanta, GA, USA.
CORRESPONDING AUTHOR:
Julian Bailes, MD Department of Neurosurgery 3rd Floor Kellogg Building Evanston Hospital 2650 Ridge Avenue Evanston, Illinois 60201 Phone: 001-847-570-1456 Fax: 001-847-570-1442 Email: jbailes@northshore.org
KEYWORDS: Trans-sulcal approach, tubular retraction system, intraventricular tumors, para-fascicular dissection
RUNNING HEAD: Trans-sulcal, para-fascicular resection of ventricular tumors.
CONFLICT OF INTEREST: The authors deny any conflict of interest or industrial affiliation related to the subject concerned in the article. AK is a consultant for Synaptive Medical and on advisory board of Medtronic and MVS is consultant for Stryker.
ABSTRACT:
Background: Conventional approaches to deep-seated cerebral lesions range from biopsy to trans-cortical or trans-callosal resection. While the former doesn't reduce tumor burden, the latter are more invasive and associated with greater potential for irreparable injury to normal brain. Disconnection syndrome, hemiparesis, hemi-anesthesia or aphasia is not uncommon after such surgery, especially when lesion is large. By contrast, the trans-sulcal parafascicular approach utilizes naturally existing corridors and employs a tubular retractor to minimize brain injury. Methods: A retrospective review of patients undergoing minimally invasive trans-sulcal parafascicular resection of ventricular and periventricular lesions, across 5 independent centers, were conducted.
Results: Twenty patients with lesions located in the lateral ventricle (n=9), the third ventricle (n=6) and periventricular region (n=4) are described in this report. Average age was 64 years (8M/12F). Average depth from cortical surface was 4.37 cm. A 13.5 mm diameter tubular retractor (Brainpath, NICO Corporation, Indianapolis, IN) of differing lengths was employed, aided by neuro-navigation. Gross-total resection was obtained in 17 patients. Pathologies included colloid cyst, subependymoma, glioma, meningioma, central neurocytoma, lymphoma and metastasis. Three patients experienced transient morbidity: memory loss (2), hemiparesis (1). One patient died 2 months postoperatively due to unrelated pulmonary illness. Follow-up ranged form 6 to 27 months (average 12 months).
Conclusion: This technique is safe and effective for the treatment of intraventricular and periventricular lesions. Surgery-related morbidity is minimal and often transient. Lesions are satisfactorily resected and residuum occur when neoplasm involves vital structures. The tubular retractor minimizes trauma to brain incident on the surgeon's path.
INTRODUCTION:
Surgical management of deep-seated cerebral lesions has always presented special challenges to the neurosurgeon. By virtue of its location, in and around the ventricles, these pathologies present distinct difficulties associated with its resection (1). Vital neurovascular structures are in close proximity and increased depth of the surgical corridor reduces degrees of freedom and instrument maneuverability. Additionally, reaching ventricular regions requires significant brain tissue sacrifice, in the process of performing trans-cortical and trans-callosal access (2,3). Morbidity associated with these techniques can be as high as 70%, with about half of the patients having more than one complication (4,5). Minimally invasive trans-sulcal approach to intra-ventricular and periventricular lesions minimizes collateral injury to brain en-route to the pathology (6). Further, use of a tubular retractor system prevents instrument related injury to gyral banks that line the sulcus of interest (7-9). Accordingly, we present our initial experience with this technique to treat these lesions, focusing on the outcomes of this surgical approach and a review of comparable techniques.
METHODS: Patient group:
A retrospective review of hospital medical records and radiological imaging of patients with intra-ventricular or periventricular lesions was performed. Patients who underwent minimally invasive, trans-sulcal resection of these lesions through a tubular retractor system with a minimum 3 month follow up period were included in this study. Information regarding demography, presentation, depth of lesion, extent of resection, post-operative outcome, and
morbidity was collected across all participating centers. Approval from institutional review board was obtained at individual centers. Surgical Technique:
All procedures were performed the use of frameless stereotactic navigation and the choice of intubation was dependent on individual surgeon's preference. Based on pre-operative imaging including diffusion tensor imaging (DTI) and intra-operative navigation, a focused craniotomy was performed over the sulcus of interest for the subcortical approach. DTI permits identification of association and projection fibers. The trajectory from target sulcus to the lesion is not necessarily the shortest, but rather the route with the least transgression of white matter fascicles.. Following craniotomy, arachnoid over the selected sulcus was opened with sharp dissection and the sulcus minimally deepened by separating lining gyral banks with blunt dissection. Through this opening, a 13.5 mm (internal diameter) tubular retractor sheath with distally tapering inner obturator, (Brainpath system, NICO Corp, Indianapolis, IN) is inserted along the pre-planned trajectory (Figure 1). The tip of the obturator was specifically designed to gently dilate the path to the lesion. Length of the BrainPath was selected depending on the depth of the lesion from the cortical surface. After removing the inner cannula, with the help of a hook like device, the sheath is fixed to pre-set Greenberg retractor bars and arms (Codman Neuro, Raynham, MA). Subsequent resection was performed with a side-cutting aspirator (Myriad, NICO Corp, Indianapolis, IN) with visualization either through an operating microscope or a table-mounted exoscope (Karl Storz, Culver City, California, USA) on a self-retaining holder (Mitaka Point Setter, Karl Storz, Culver City, California, USA). The exoscope, contrary to the endoscope, is held high up - away from the region of interest. It also is attached to an external light source (endoscopes have internal light supply) that moves together with the exoscope. The
diameter of the port allowed for both binocular vision and as well as bimanual handling of the tissues. The direction of the port can be altered gently, to give more coverage of the lesion, to aid in complete resection.
RESULTS:
Demographics:
We identified 20 patients with ventricular (n=15) and peri-ventricular (n=5) pathologies resected using above-mentioned technique (Table 1). The average age of patients was 64 years, ranging from 19 to 74 years. There was a slight female predominance (12 females and 8 males). The most common presentation was headaches and short-term memory deficits (8 patients each). Two tumors were found incidentally and 1 on routine surveillance. Other clinical findings include hemiparesis, hydrocephalus, ataxia, urinary incontinence and aphasia. Pathology:
Regional division of the lesions consisted of 9 located in the lateral ventricle, 6 in the third ventricle and 5 in periventricular region (right frontal, left parietal, left thalamic metastasis, right peri-atrial and left thalamic high-grade glioma). Five colloids cysts were found exclusively in the third ventricle, while the 6th lesion in the same region was pilomyxoid astrocytoma. Lateral ventricular lesions included meningioma in 2 patients, subependymoma in 3 patients, 2 with high-grade glioma, a primary central nervous system lymphoma, a central neurocytoma, a low-grade glioma and a high-grade glioma in individual patients. Lesion depth from cortex ranged from 2.5 cm to 5.85 cm, average 4.37 cm. Outcome:
Gross-total resection was obtained in 17 patients out of 20 (85%). Three patients who had neoplasm invade left basal ganglia (75% resection), left thalamus (87%) and hypothalamus (75%) underwent sub-total resection for functional preservation. Two patients, one with primary CNS lymphoma of the right occipital horn and another with lateral ventricular neurocytoma, underwent near total resection (97%). Patient follow-up averaged 12 months (ranges from 6 to 27 months). All patients were followed for minimum 6 months postoperatively, many for longer periods. Early morbidity related to surgery was seen in 3 patients. One had transient short-term memory loss, which resolved within a month. Another had transient hemiparesis post-operatively that recovered completely. The third patient had worsening of preoperative memory deficit that improved during the follow up period. One patient with third ventricular astrocytoma required permanent CSF diversion. There was one death in the cohort; a 66 year-old male with non-small cell lung cancer metastasis to right frontal lobe (periventricular) developed an unrelated fatal pulmonary fungal infection in the third postoperative month, he subsequently died from primary disease at 8 months from surgery.
Illustrative cases
Case 1 (Figure 2): A 43 year-old woman presented to an out-of-state emergency department with altered mental status, recent memory loss and paraphasic speech errors. She had recently been more forgetful of everyday activities and conversations, but on the day of presentation became drowsy and was unable to speak clearly and coherently. Initial imaging showed a left thalamic ring-enhancing lesion causing hydrocephalus from posterior third ventricular obstruction. After external ventricular drain (EVD) placement to treat hydrocephalus, the patient was airlifted to the referral institution. She underwent minimally invasive trans-sulcal resection
of this mass and histopathological exam revealed to be a high-grade glioma. Fusion of preoperative DTI and intra-operative navigation helped to select a trajectory to the tumor that did not traverse major white matter tracts. Immediately after surgery, the patient had significant improvement in memory and language function. After removing the EVD, she was discharged to a rehabilitation facility in improved neurological status. She further underwent standard chemo-radiation for her tumor, and follow up imaging 8 months after her initial surgery did not show any recurrent tumor growth. The patient recovered well enough to be back at home independently, caring for her children.
Case 2 (Figure 3): A 54-year old woman was seen in neurosurgical consultation regarding an enlarging right atrial (lateral ventricular) tumor, which appeared consistent with benign meningioma on MR imaging. The patient was known to harbor this lesion, which was followed with serial imaging at yearly intervals. She was offered surgical resection, when 2 consecutive surveillance studies showed sustained growth, considering the risks involved in removing a very large, symptomatic mass. The lesion was approached through a trans-sulcal, para-fascicular path and removed using the tubular retraction system. The right atrium was entered through intra-parietal sulcus and the lesion was removed in total, after initial internal decompression. She was discharged on second post-operative day and continued to do well during her follow up visits and with no recurrence on MR imaging at 8 months.
Case 3 (Figure 4): A 19-year-old otherwise healthy man, presented with an acute episode of dizziness causing fall and one-day history of severe headache. He had had two prior episodes of similar headache over the preceding six months. Imaging demonstrated a non-enhancing third ventricular tumor, extending into the left lateral ventricle with obstructive hydrocephalus. The patient underwent a minimally invasive trans-sulcal resection of this mass, which revealed a
pilomyxoid astrocytoma, WHO grade II. The trans-sulcal corridor was planned via neuronavigation to minimize injury to descending and association white matter tracts. Gross total resection was accomplished, as demonstrated by post-operative imaging. He was discharged home on fourth post-operative day, with no neurologic morbidity but presented shortly with hydrocephalus requiring permanent diversion. Follow-up imaging 6 months after surgery did not show any recurrence; and patient was clinically at baseline.
DISCUSSION:
Intraventricular and peri-ventricular lesions are not infrequent in any neurosurgical practice. Management of these lesions has evolved over time; with developments in various aspects of surgical and non-surgical modalities though cytoreduction continues to be mainstay in oncological care and cure. Moreover, patients with lesions (including non-neoplastic) that are symptomatic neurologically should benefit by surgical resection or decompression. The application of microsurgical procedures and techniques and advent of self-retaining retractors have revolutionized cerebral surgery (10,11). Unfortunately, brain retraction is not without perils, especially with flat-blade retractors brain retraction edema and infarct is a well-defined entity with both radiological and clinical features (12). The use of a tubular retractor allows equal distribution of pressure on surrounding brain; on the contrary, flat-blade retractors exert maximum pressure on the edges (13,14). This significant difference is amplified when large deep lesions are resected over long duration surgery. Additionally, while conventional retractors are placed often after trans-cortical or trans-callosal brain tissue removal, the tubular retractors are inserted with sequential dilation of a track that displaces white matter fiber tracts (15,16).
Neuroendoscopy, advocated in recent years as a superior alternative to microsurgery, is not without difficulties. Though endoscopic resection has shown reduced morbidity and faster recuperation, it still has unique difficulties due to limited appropriate instruments to resect tumors completely and hence considered more suitable for cystic lesions, favorably in enlarged ventricles (17-19). Vascular control during endoscopy can be precarious, even insignificant bleeding can obscure visibility, and, contrary to usual air medium, neuroendoscopic procedures are performed under a liquid medium (20). Neuroendoscopy is not useful in cases of peri-ventricular lesions, except to biopsy, even with ventricular tumors is known to have higher recurrence rates (17,20). Additionally, in spite of being least invasive, neuroendoscopic resection of ventricular tumors is not devoid of significant morbidity, such as hemorrhage, infection, cranial nerve deficits and hormonal dysfunction (19,21,22). Utilization of DTI markedly improves the preservation of sub-cortical white matter tracts. Lesions in and around the foramen of Monro were approached through widening the superior frontal sulcus. Apart from the pyramidal tract, care is also taken to maintain the integrity of superior longitudinal fascicle (SLF), which commonly is a victim of collateral injury during such an approach to the ventricles with flat blade retractors. The anterior part of SLF in the dominant hemisphere has been associated with speech and motor planning and there are contradictory reports about posterior SLF involvement in semantic language processing (23,24). Approaching atrial or peri-atrial pathology, especially in the dominant hemisphere, can lead to development of aphasia. In our approach these lesions were reached by parting the intra-parietal sulcus, thereby preserving surrounding fiber tracts of great significane (Figure 5).
Previously published reports discuss usage of retractors in trans-cortical resection of lateral ventricular tumors but trans-sulcal route minimizes brain injury during resection
(7,14,15). Opening of sulci and fissures have made even unreachable regions of the brain within neurosurgeon's grasp. Patient morbidity is decreased through less potential injury to the critical white matter tracts and vascular pedicles of both cortical and subcortical structures (3,19). Coupled with advances in neuro-navigation and exoscope technology, the trans-sulcal insertion of a port system allows a working corridor, to run alongside white matter tracts and not through them. This is highlighted by reports of trans-sulcal approaches to deeper lesions, without an encircling retractor, which show similar morbidity profile as that of transcortical technique (1). This could be due to a couple reasons. First, deeper lesions need a retractor system to keep the track open and flat blade retractors exert exponential pressure on the tissue that is being retracted (12). Second, in the conventional retractor systems, introduction of instruments and surgeon movements are continuously transmitted to the banks lining the approach. This often causes further injury to adjacent brain structures and could prove costly in eloquent locations.
Various tubular retractor systems have been developed over the last couple of decades. An ideal system should possess a particular set of qualities that would make it unique and applicable. A retractor with a small internal diameter precludes bimanual operations and at times even binocular vision; while too large an opening is counter-intuitive to minimizing brain injury and negates the advantage of the approach in discussion (25-27). Secondly, the technique of insertion should be easy, uncomplicated and involve gradual dilation of the surgical corridor, without the serial use of increasingly large dilators (16). Our system utilizes frameless stereotaxy to plan and execute trajectory, thereby avoiding the inconvenience of operating through stereotactic frames (10,13,28). Additionally the Brainpath sheath has a fixed diameter along its length and it is transparent, allowing continuous inspection of tissue that is being retracted during the procedure (7,15). In using this system, we find ease in employing multiple resection tools
such as Myriad (side-cutting aspirator, NICO Corp, Indianapolis, IN), ultrasonic aspirator and bipolar cautery device; simultaneously wielding suction in the non-dominant hand, without being constrained by limited space (29).
We note that multiple groups have previously utilized various individual components of our technique, in addressing ventricular and peri-ventricular lesions. Few centers have reported their experience with use of tubular retractor but, based on their descriptions, lesions were reached by performing cortisectomy to accommodate the retractor system (14,25,30). As highlighted, we did not require any such maneuvers to position our retractor. Conversely, some authors have advertised their use of tran-sulcal approach to ventricular tumors, but with conventional retractor systems (1,31). Our technique of trans-sulcal approach and use of tubular retractor system is unique and not comparable with either combination mentioned above. Moreover, individual surgeons had the opportunity of using either microscope or exoscope or both, depending on the depth of the lesion and need for 3D vision. Limitations:
Our study is not without drawbacks. Being a retrospective study, it is subject to biases and additionally selection of patients for this technique was dependent on individual surgeon's discretion. Since all consecutive patients who presented with ventricular or per-ventricular pathology were operated utilizing this technique, we believe some of these limitations have been overcome. Additionally, an honest appraisal of surgical shortcomings - both incomplete resection and post-operative neurological deficit; has been presented. Another point of contention has been the short follow up offered in our study. We primarily wished to perform a 'proof of principle' study with this technique and this regard we feel our follow up period is sufficient to enumerate both complications from this technique and possible recovery from
neurological deficits. Most importantly we intend to present a novel technique in resecting deep cerebral lesions and discuss nuances of such an approach, which we believe the article achieves.
CONCLUSION:
Minimally invasive trans-sulcal parafascicular resection of ventricular and periventricular lesions using tubular retractors, inserted with the aid of neuro-navigation, is an amalgam of recent advances in various compartments pertaining to surgery of the human cerebrum. Utilization of frameless stereotaxy minimizes surgical invasiveness and also executes the procedure with precision, choosing trans-sulcal, para-fascicular trajectory reduces brain traversed to reach these lesions and deployment of tubular retraction provides greatest protection to displaced neural tissue. Development of innovative resections tools such as side-cutting aspirator and ablative lasers further enhance efficiency of lesion removal. Surgical and neurological morbidity comparable to other invasive approaches such as trans-cortical and trans-callosal, while maintaining bimanual lesion resection, improved hemostasis and visualization through an air medium.
ACKNOWLEDGMENTS
The authors would like to thank Vimal Patel, PhD, Medical & Scientific Writer at NorthShore Neurological Institute for his assistance with copy editing the manuscript.
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FIGURE LEGENDS:
Figure 1. Insertion of Brain port: The precise trajectory for port insertion is determined with the aid of neuronavigation (A). Following dural opening, the selected sulcus is opened widely before advancing the port (B). Once the port is advanced to the desired length, the obturator is removed and port fixed with a self-retaining retractor system (C). Visualization of intraventricular anatomy and incident pathology around the foramen of Munro is evident with either exoscope or microscope (D). Bottom row shows representative images from patient #20 detailing white matter tracts around the lesion and optimum trajectory to the lesion that avoids violation of major tracts. Conventionally, the lesion would probably be approached from the temporal side (shortest distance to the lesion) but this endangers major white matter tracts, especially optic tract significantly.
Figure 2. Patient #8: A 43-year-old lady with imaging showing left thalamic ring enhancing tumor, causing hydrocephalus (Top left). Patient underwent trans-sulcal parafascicular excision through a tubular retraction system, using neuronavigation (Top right and bottom right). Excellent tumor resection was obtained and residual tumor and tumor bed was irradiated. Follow up imaging 8 months after surgery shows good control without recurrence (Bottom left).
Figure 3. Patient #11: Pre-operative (top) and postoperative images (bottom) images of a 54-year-old lady who underwent trans-sulcal, parafascicular resection of an enlarging right atrial meningioma. The sagittal post-operative image on the bottom right shows the trajectory taken by the tubular retractor. As seen in these images, a gross total resection was effected without any problems.
Figure 4. Patient #14: A 19-year-old male with MR imaging demonstrating a non-enhancing third ventricular tumor (Top right, axial T2 FLAIR) extending in the left lateral ventricle (Top left, sagittal T2 FLAIR), causing obstructive hydrocephalus. Patient underwent trans-sulcal parafascicular excision through a tubular retraction system, using neuronavigation. Gross total resection was obtained (Bottom left, sagittal T2 FLAIR) through an atraumatic corridor that collapsed around a ventricular catheter without surrounding edema or ischemia (Bottom right, coronal T1 post-contrast).
Figure 5. Patient #19: A 46-year old female with hemorrhagic left thalamic metastatic lesion that presented with acute hydrocephalus, language problems and mild right-sided weakness (Top left - axial post contrast). She had recently initiated treatment for breast cancer with unilateral mastectomy. Pre-operative DTI showed displacement of optic pathway postero-laterally and pyramidal tract is seen antero-laterally in the posterior limb of internal capsule while superior longitudinal fasciculus (SLF) is not evident on the affected side (Top right). Her lesion was approached through a parietal craniotomy and port insertion through the inter-parietal sulcus (Bottom left). The trajectory utilized the window between optic tract, pyramidal tract fibers and SLF (Bottom right).
Table 1: Patient demographics and treatment details (GTR - Gross total resection)
Patient # Age/Sex Pre op deficits Location Lesion Depth Extent of resection Lesion Pathology Post op deficits
1 20/F Headache Left lateral ventricle 4 cm 97% Central neurocytoma None
2 48/M Severe short term memory deficit Third ventricle 5.5 cm GTR Colloid cyst No new deficits
3 23/M Moderate short term memory deficit Third ventricle 5.5 cm GTR Colloid cyst No new deficits
4 60/M Severe short term memory loss, ataxia, urinary incontinence Third ventricle 5.5 cm GTR Colloid cyst No new deficits
5 31/F Obtunded, hydrocephalus Third ventricle 5.5 cm GTR Colloid cyst No new deficits
6 62/F Confusion, memory loss Third ventricle 5.59 cm GTR Colloid cyst None
7 50/M Hydrocephalus Intraventricular 4 cm GTR High grade Glioma No new deficits
8 43/F Hydrocephalus, aphasia, amnesia, weakness Left Thalamic 4.2 cm 87% High Grade Glioma No new deficits
9 54/F Headaches, memory deficit, left sided weakness Intraventricular 4.29 cm GTR Low grade Astrocytoma No new deficits
10 29/F None Left lateral ventricle (atrial) 3.5 cm GTR Meningioma None
11 54/F None Right lateral ventricle (atrial) 4.5 cm GTR Meningioma None
12 58/F On routine surveillance Left parietal 2 cm GTR Metastatic tumor No new deficits
13 66/M Hydrocephalus, left-sided weakness, Right Basal Ganglia 3.73 cm 75% Metastatic tumor Left sided weakness
14 19/M Headaches, hydrocephalus Third ventricle 4.4 cm GTR Pilomyxoid Astrocytoma None
15 50/F Short term memory difficulties - mild Right occipital horn 3.6 cm 97% Primary CNS lymphoma None
16 53/F Lightheadedness and dizziness Intraventricular 4.38 cm GTR Subependymoma Short-term memory loss
17 74/M Mild short term memory deficit L lateral, 3rd ventricles 4.5 cm 75% Subependymoma Short term memory loss
18 55/M Right-sided weakness, hydrocephalus Left Lateral Ventricle 5.85 cm GTR Subependymoma None
19 46/F Aphasia, right sided weakness, hydrocephalus Left thalamic 3.7 cm GTR Metastatic tumor None
20 70/M Headache Right peri-atrial 4 cm GTR High grade Glioma None
HIGHLIGHTS:
• Minimally invasive trans-sulcal parafascicular approach uses naturally existing corridors.
• The approach employs a tubular retractor to minimize brain injury incident on the surgeon's path.
• Approach is safe and effective for treatment of intraventricular and periventricular lesions.
• Frameless stereotaxy minimizes surgical invasiveness and executes the procedure with precision.
• Approach maintains bimanual resection, improved hemostasis and visualization through an air medium.
ABBREVIATIONS:
CNS: Central nervous system
CSF: Cerebrospinal fluid
DTI: Diffusion tensor imaging
MRI: Magnetic resonance imaging
SLF: Superior longitudinal fasciculus
