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Purpose: The petroclival region represents the "Achille's heel" for the neurosurgeons. Many ventral endoscopic routes to this region, mainly performed as isolated, have been described. The aim of the present study is to verify the feasibility of a modular, combined, multiportal approach to the petroclival region to overcome the limits of a single approach, in terms of exposure and working areas, brain retraction and manipulation of neurovascular structures. Methods: Four cadaver heads (8 sides) underwent endoscopic endonasal transclival, transorbital superior eyelid and contralateral sublabial transmaxillary-Caldwell-Luc approaches, to the petroclival region. CT scans were obtained before and after each approach to rigorously separate the contribution of each osteotomy and subsequentially to build a comprehensive 3D model of the progressively enlarged working area after each step. Results: The addition of the contralateral transmaxillary and transorbital corridors to the extended endoscopic endonasal transclival in a combined multiportal approach provides complementary paramedian trajectories to overcome the natural barrier represented by the parasellar and paraclival segments of the internal carotid artery, resulting in significantly greater area of exposure than a pure endonasal midline route (8,77 cm2 and 11,14 cm2 vs 4,68 cm2 and 5,83cm2, extradural and intradural, respectively). Conclusion: The use of different endoscopic "head-on" trajectories can be combined in a wider multiportal extended approach to improve the ventral route to the most inaccessible petroclival regions. Finally, by combining these approaches and reiterating the importance of multiportal strategy, we quantitatively demonstrate the possibility to reach "far away" paramedian petroclival targets while preserving the neurovascular structures.

Three-dimensional (3-D) endoscopes have been widely used for a large variety of approaches in neurosurgical practice. However, in the last decade, 3-D scopes were barely used for ventricular surgery. In this study, we illustrated our preliminary experience with a 3-D endoscope for third ventriculostomy using new dedicated endoscopic equipment.Over a 12-month period, a high-definition 3-D endoscopic third ventriculostomy (ETV) was performed in 14 patients with obstructive hydrocephalus. Patients were followed prospectively and compared retrospectively with a matched group of 16 similar patients who underwent ETV with a standard 2-dimensional (2-D) endoscope. Surgical outcome and intra- and postoperative course were retrospectively reviewed.3-D ETV provided excellent surgical results, and no significant difference was shown in terms of outcome, complication, and length of hospitalization between the 2 groups. Moreover, operative time (minutes) was significantly shorter in the 3-D group than the 2-D ETV group (19.9 ± 4.8 vs. 22.9 ± 1.4, respectively; P0.05), and the use of the 3-D endoscope provided subjective improvements of depth perception, hand-eye coordination, and surgeon comfort.Our preliminary study clearly demonstrated the effectiveness of 3-D ETV and provided a significant reduction of operative time. Depth information from the 3-D scope appears to facilitate rapid and stable ETV maneuvers, representing a critical development that may become a valuable tool for neuroendoscopy.

The pattern of growth of spheno-orbital meningiomas accounts for the main presenting symptoms, such as proptosis, eye motility deficit, visual impairment, diplopia. As these are benign tumors, the postoperative patient's quality of life is an important factor to consider during the preoperative planning. A detailed literature review of superior eyelid transorbital endoscopic approach for spheno-orbital meningiomas, including our own case, was made. A Medline search up to March 2022 in PubMed online electronic database was made using the following key phrases: "superior eyelid endoscopic transorbital approach spheno-orbital meningiomas," "superior eyelid endoscopic transorbital approach," "spheno-orbital meningiomas endoscopic approach." The inclusion criteria were surgical series, reviews, and case reports in English language, as well as papers written in other languages, but including the abstract in English. Cadaveric studies, multiportal combined approaches for SOM, were excluded. The literature review has disclosed five studies for a total of 65 patients, whose demographic, clinical, pathological, surgical, complications, and outcome data were analyzed. Functional and esthetic outcome data after superior eyelid transorbital approach are the following: improvement of proptosis (100%), of visual deficits (66.66%) and of ocular paresis (75%), with only 11 complications (4 trigeminal dysesthesia, 2 CSF leak, 2 wound complications, 1 upper eyelid necrosis, 1 hemorrhage of surgical field, 1 keratitis) reported, but at the expense of extent of resection (gross total resection 33.39%). Based on the outcome data, the superior eyelid transorbital endoscopic approach results in a suitable operative technique for selected spheno-orbital meningiomas.

Background: Advances in visualization tools have brought new confidence, including endoscope-integrated indocyanine (E-ICG), which makes pituitary and skull-base surgery safer and more effective. We report here our preliminary experience with the use of E-ICG to 1) visualize the cavernous segment of the internal carotid artery (ICA); and 2) functionally and anatomically preserve the pituitary gland. Methods: A dedicated ICG-integrated endoscope was used in 15 patients with parasellar pituitary adenomas. Indocyanine was administered at 2 different time points during surgery: an early bolus of 12.5 mg at the sphenoid sinus opening to expose the position of the parasellar segment of the ICAs and to identify the position of the normal pituitary gland so that it could be preserved during tumor removal. Subsequently, a second late bolus of 12 mg of ICG was injected to obtain a real-time “wire angiographic” visualization of the flow of the ICAs. Results: Gross total resection was achieved in 12 cases (80%), whereas subtotal resection was performed in the other 3 cases (20%). The pituitary gland was clearly discernable in 11 cases (91.6%). None of the patients manifested new endocrinologic deficits or major vascular complications. Conclusions: E-ICG is a safe and essential aid for pituitary adenomas invading the cavernous sinus. Its performance as a pituitary marker and real-time video angiography showed promising results in terms of extent of resection, endocrinologic outcomes, and prevention of intraoperative complications.

BACKGROUND: The recent development of the superior eyelid endoscopic transorbital approach (SETOA) offered a new route for the management of cavernous sinus and middle cranial fossa tumors. As a result, a constant anatomic landmark of the surgical pathway after drilling the medial edge of the greater sphenoid wing (GSW) is represented by a triangular-shaped bone ridge appearing as a "crest." OBJECTIVE: To perform an anatomic study to define this surgical landmark, named the "sagittal crest" (SC) as seen from the transorbital endoscopic view. METHODS: Four adult cadaveric specimens (8 sides) were dissected performing an endoscopic transorbital approach to the middle fossa and the SC was removed to perform interdural opening of the cavernous sinus. Computed tomography scans were made before and after removal of the SC to perform quantitative analysis and building a 3-dimensional model of the bone resection of the GSW via the SETOA. RESULTS: The SC is a bone ridge triangle shaping dorsally the superior orbital fissure resulting as the residual fragment after drilling the lateral aspect of the greater sphenoid wing. Predissection and postdissection computed tomography scans allowed to objectively assess SC features and dimensions (mean 1.08 ± 0.2 cm). CONCLUSION: The SC is a constant anatomic landmark constituted of the residual medial portion of the GSW. Complete resection of this key landmark provides adequate working space and appears to be mandatory during SETOA to guide the subsequent interdural dissection of the lateral wall of cavernous sinus.

Background Chronic subdural hematoma (CSDH) is frequently encountered in neurosurgical practice. Evacuation through one or two burr holes is the most common surgical treatment. Hemorrhagic complications such as acute subdural hematoma (ASDH) or intracerebral hemorrhage (ICH) has been reported as rare but severe complications. Nonetheless, isolated subarachnoid hemorrhage (SAH), developed after burr-hole evacuation of CSDH, without other hemorrhagic complications, is an extremely rare finding reported only in two previous reports. Case description A 64 year’s old man was referred to our department for mental confusion, disorientation, dizziness and walking disability. CT scans showed a bilateral fronto-parietal CSDH. He underwent bilateral parietal burr-hole craniectomy and subdural drainage positioning. The day after surgery, the patient developed intense headache and vomit and a CT scan revealed a SAH in the temporal and parietal lobe located in both hemispheres. A CT angiogram excluded the presence of intracranial aneurysms. The drainage systems were removed and the patient underwent conservative management with clinical improvement. He was discharged in day 7 without neurological deficits. The one-month follow-up showed the patient was in good conditions and the CT scan revealed complete resolution of the previous hemorrhagic findings. Conclusion We suppose the rapid brain shift occurred during surgery was the main cause of development of SAH in our patient, but several possible pathological mechanisms are discussed. Although CSDH evacuation is considered a routinely procedure, neurosurgeons must be aware of this rare complication avoiding perioperative overdrainage of subdural hematomas.

Investigative studies of white matter (WM) brain structures using diffusion MRI (dMRI) tractography frequently require manual WM bundle segmentation, often called “virtual dissection.” Human errors and personal decisions make these manual segmentations hard to reproduce, which have not yet been quantified by the dMRI community. It is our opinion that if the field of dMRI tractography wants to be taken seriously as a widespread clinical tool, it is imperative to harmonize WM bundle segmentations and develop protocols aimed to be used in clinical settings. The EADC‐ADNI Harmonized Hippocampal Protocol achieved such standardization through a series of steps that must be reproduced for every WM bundle. This article is an observation of the problematic. A specific bundle segmentation protocol was used in order to provide a real‐life example, but the contribution of this article is to discuss the need for reproducibility and standardized protocol, as for any measurement tool. This study required the participation of 11 experts and 13 nonexperts in neuroanatomy and “virtual dissection” across various laboratories and hospitals. Intra‐rater agreement (Dice score) was approximately 0.77, while inter‐rater was approximately 0.65. The protocol provided to participants was not necessarily optimal, but its design mimics, in essence, what will be required in future protocols. Reporting tractometry results such as average fractional anisotropy, volume or streamline count of a particular bundle without a sufficient reproducibility score could make the analysis and interpretations more difficult. Coordinated efforts by the diffusion MRI tractography community are needed to quantify and account for reproducibility of WM bundle extraction protocols in this era of open and collaborative science.

The efficacy of endoscopic techniques in the surgical management of intracanalicular vestibular schwannomas (ICVSs) has been underlined in recent studies. An endoscopic- assisted retrosigmoid approach (EARSA) appears to be particularly suitable for achieving complete resection of an ICVS. In this study, we describe the surgical treatment of 3 cases of ICVS with an EARSA, highlighting the advantages and limitations of flexible endoscopy in accomplishing a safe radical resection with hearing preservation. Three patients with an ICVS underwent surgery via a flexible endoscopic-assisted microneurosurgical retrosigmoid approach. Flexible endoscopic assistance allowed the identification of residual tumor located in the most lateral portion of the fundus of the internal auditory canal in all cases. Endoscopic controls and further microsurgical resection were attempted, and complete surgical resection was achieved in all cases without the occurrence of postoperative facial or auditory nerve dysfunction. Flexible endoscopy appears to be particularly useful and safe in the surgical management of ICVS by microneurosurgery via an EARSA.

Background Ventriculoperitoneal (VP) shunt is the most frequent treatment for hydrocephalus. VP shunt malfunction is a very common problem in neurosurgical practice, often requiring shunt revision procedures. In some cases, complete removal of a VP shunt may present difficulties, leading the surgeon to leave the ventricular catheter in situ. This decision is often made to avoid possible adverse events, primarily risk of life-threatening hemorrhage. However, a nonfunctioning catheter left in the ventricular system may lead to further complications. Case Description We report the case of an adult man who presented with a tumor-like cystic lesion, with mural and nodular postcontrast enhancement, caused by a huge granuloma formed around the tip of a retained ventricular catheter. Conclusions This occurrence is extremely rare, and this is the first reported case in the literature. Preoperative differential diagnosis was challenging and included infection, metastasis, dysembryogenetic lesions, and rare reversible porencephalic cysts. According to several physiopathogenetic theories recently reported in the literature, the granuloma may develop as the result of persistent chronic inflammatory reactions between the ventricular catheter left in situ and the brain parenchyma. Application of neuroendoscopic techniques is improving management of VP shunt revisions, allowing safe removal of catheters stuck or lost in the ventricular system. Neuroendoscopy may represent an additional option to avoid possible complications related to retained ventricular catheters.

The extreme lateral infrajugular transcondylar-transtubercular exposure (ELITE) is a surgical approach developed in the late 1980s by Prof. T. Fukushima and represents the dorsolateral inferior skull base procedure of choice to approach lesion located ventrolaterally at the level of the craniocervical junction (CCJ). This approach consist in a suboccipital craniotomy/craniectomy with partial condylectomy and jugular tubercule drilling that can be extended providing for subtotal condylectomy and vertebral artery transposition. The “limited” variation of the ELITE approach consist in a lateral suboccipital craniectomy opening the foramen magnum and removal of at least half of the posterior arch of the atlas without condyle drilling. This surgical technique was recently demonstrated to be particularly suitable for the surgical management of spinal tumor located ventrolaterally in the upper cervical spine. This operative video illustrates step-by-step the surgical technique adopted for the microsurgical resection of a C1-C2 intradural schwannoma located antero-laterally ( Video 1 ). ELITE approach offers a wide and adequate exposure and access to the CCJ, allowing direct visualization and access to the tumor with minimal neural manipulations, early detection of the vertebral artery and, for tumor located at C1-C2 level, without drilling the occipital condyle. In our experience, ELITE procedure is the preferred surgical approach for resection of tumors located ventrally or ventrolaterally to the first 2 cervical levels.

Investigative studies of white matter (WM) brain structures using diffusion MRI (dMRI) tractography frequently require manual WM bundle segmentation, often called "virtual dissection". Human errors and personal decisions make these manual segmentations hard to reproduce, which have not yet been quantified by the dMRI community. The contribution of this study is to provide the first large-scale, international, multi-center variability assessment of the "virtual dissection" of the pyramidal tract (PyT). Eleven (11) experts and thirteen (13) non-experts in neuroanatomy and "virtual dissection" were asked to perform 30 PyT segmentation and their results were compared using various voxel-wise and streamline-wise measures. Overall the voxel representation is always more reproducible 1. CC-BY-NC-ND 4.0 International license available under a not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made The copyright holder for this preprint (which was this version posted April 30, 2019. ; https://doi.org/10.1101/623892 doi: bioRxiv preprint than streamlines (≈70% and ≈35% overlap respectively) and distances between segmen-tations are also lower for voxel-wise than streamline-wise measures (≈3mm and ≈6mm respectively). This needs to be seriously considered before using tract-based measures (e.g. bundle volume versus streamline count) for an analysis. We show and argue that future bundle segmentation protocols need to be designed to be more robust to human subjectivity. Coordinated efforts by the diffusion MRI tractography community are needed to quantify and account for reproducibility of WM bundle extraction techniques in this era of open and collaborative science.

International audience; Fiber tractography (FT) using diffusion magnetic resonance imaging (dMRI) is widely used for investigating microstructural properties of white matter (WM) fiber-bundles and for mapping structural connections of the human brain. While studying the architectural configuration of the brain's circuitry with FT is not without controversy, recent progress in acquisition, processing, modeling, analysis, and visualization of dMRI data pushes forward the reliability in reconstructing WM pathways. Despite being aware of the well-known pitfalls in analyzing dMRI data and several other limitations of FT discussed in recent literature, we present the superoanterior fasciculus (SAF), a novel bilateral fiber tract in the frontal region of the human brain that-to the best of our knowledge-has not been documented. The SAF has a similar shape to the anterior part of the cingulum bundle, but it is located more frontally. To minimize the possibility that these FT findings are based on acquisition or processing artifacts, different dMRI data sets and processing pipelines have been used to describe the SAF. Furthermore, we evaluated the configuration of the SAF with complementary methods, such as polarized light imaging (PLI) and human brain dissections. The FT results of the SAF demonstrate a long pathway, consistent across individuals, while the human dissections indicate fiber pathways connecting the postero-dorsal with the antero-dorsal cortices of the frontal lobe.

Dumbbell-shaped thoracic tumors usually arise from neurogenic elements within the spinal canal and are characterized by involvement of both spinal canal and posterior thoracic cavity. The tumor mass becomes frequently very large growing inside and outside of the spinal canal, through the connection of the neural foramen, involving the surrounding structures. Most of the dumbbell tumors are peripheral nerve sheath tumors, of which neurofibromas and schwannomas represent the vast majority. Gross total resection is considered the treatment of choice and can be achieved through several combined thoracic-neurosurgical approaches. However, these operations have significant approach-related morbidity; therefore, in the last decades, thanks to the constant progress of technological devices, minimally invasive techniques have been increasingly used for the surgical management of spinal tumors. In this surgical video (Video 1), we present a minimally invasive, single-step posterolateral approach through a small costotransversectomy (centered with echography and fitted with spine navigation) for the surgical management of a giant dumbbell thoracic neurofibroma. The usefulness of current technology guiding the surgical procedure is underlined with special emphasis.

International audience; BACKGROUND:Advances in the oncologic and functional results of insular surgery have been reported recently. Such successes have been made possible by the advent of the transopercular approach under awake monitoring and by improved anatomic and functional knowledge of white matter pathways surrounding the insula. Nonetheless, given the rarity of insular tumors, it is difficult to get familiar with the complex 3-dimensional anatomy of the different neuronal and vascular structures encountered during a transopercular insular resection. We thus propose to develop a laboratory model allowing to train transopercular approaches of the insula.METHODS:Two hemispheres prepared with Klinger's technique were dissected under light microscope, preserving all pial membranes. The different steps of the dissection were video recorded.RESULTS:Preservation of pial membranes enabled us to simulate subpial resection, both during operculum removal and during insular cortex resection. The medial wall of the resection was defined by the inferior-fronto-occipital fasciculus, protecting from the lenticulostriate arteries.CONCLUSION:In this paper, we show that Klinger dissection with preservation of pial membranes provides a realistic model of insular surgery, allowing surgeons to learn and train on this highly specialized surgery.

Skull base tumors arising from the middle cranial fossa and invading of the infratemporal fossa (ITF) and middle cranial fossa are challenging for neurosurgeons, because of complex anatomy and critical neurovascular structure involvement. The first pioneering ITF approaches resulted in invasive procedures and carried a high rate of surgical morbidity. However, the acquisition of deep anatomical knowledge, and the development operative skills and reconstruction techniques allowed surgeons to achieve total or near total resection of many ITF lesions with a low morbidity rate. In Video 1 we illustrate our technique for the anterior ITF approach for the surgical treatment of a middle cranial fossa meningioma invading the ITF. This surgical video describes the anterior ITF approach in 2 steps. First, a standard extradural middle fossa approach subtemporal approach is performed on a cadaveric specimen, illustrating the anterior extension to the cavernous sinus. Second, the anterior ITF approach is performed for the surgical treatment of a temporal lobe meningioma with extension to the anterior ITF. This technique provides a minimally invasive approach for treating middle fossa lesions with anterior ITF extension.

Substantial progress in acquisition, processing, and analysis boosted the reliability of diffusion-weighted MRI and increased the accuracy of mapping white matter pathways with fiber tractography. Since the introduction of ‘region of interest’ (ROI) based virtual dissection by Conturo et al. in 1999, researchers have used tractography to identify white matter pathways, which faithfully represented previously known structures revealed by dyeing studies or post-mortem descriptions. The reconstructed streamlines are subjects of bundle-specific in vivo investigations to show differences between groups (e.g., comparing fractional anisotropy (FA) between patients and healthy controls) or to describe the relation between diffusion scalars and metrics of interest (e.g.: normal aging or changes due to learning). By applying a reverse strategy in using diffusion-weighted MRI tractography first, then supporting the findings with other techniques, we have identified a bilateral tract in the frontal cortex - the superoanterior fasciculus (SAF). The tract resembles the anterior shape of the cingulum bundle, but is located more frontally. To erase the chance that our findings are confounded by acquisition, processing or modeling artifacts, we analyzed a total of 421 subjects from four cohorts with different acquisition schemes and diverse processing pipelines. The findings were also completed with other non-MRI techniques, such as polarized light microscopy and dissection. Tractography results demonstrate a long pathway and are consistent among cohorts, while dissection indicates a series of U-shaped fibers connecting adjacent gyri. In conclusion, we hypothesize that these consecutive U-shaped fibers emerge to form a pathway, thereby resulting in a multicomponent bundle.

Video 1 describes the technique of microsurgery removal of acoustic neuromas (ANs) using new technologies. The Flexible 2μ-Thulium hand-held laser fiber (Revolix jr, LISA laser products, 7 OHG, Berlin, Germany) and Sonopet Ultrasound Aspirator (Stryker, Kalamazoo, Michigan, USA) can be used for a safe and facilitated opening of the internal auditory canal (IAC). We illustrate the operative technique used on a surgical series of 111 cases operated on during the past 8 years, from July 2010 to July 2018. We studied 170 consecutive patients suffering from ANs who were operated on with a microsurgical technique by the key-hole retrosigmoid approach. In 111 cases the “Sonopet” Ultrasound Aspirator was used to open the IAC and a 2μ-Thulium laser fiber was used for cutting the dura mater of the posterior aspect of petrous bone and the IAC, and it was also used to perform tumor capsule incision. From December 2017 we started to check the removal of tumor inside the IAC with a flexible endoscope 4 mm × 65 cm, (Karl Storz GmbH, Tuttlingen, Germany) in order to detect possible tumoral residue and achieve a radical tumor resection in the fundus. The use of these new technologies seems to be safe and subjectively facilitates the opening of the IAC in AN microsurgery.

International audience; BACKGROUND:Face recognition is a complex function sustained by a distributed large-scale neural network, with a core system involving the ventral occipitotemporal cortex, the inferior longitudinal fasciculus (ILF), and the splenial commissural fibers. This circuit seems to be bilaterally organized, but with a right hemispheric dominance. According to this anatomic functional model, prosopagnosia is usually, but not exclusively, generated by a damage of the right part of this brain network.CASE DESCRIPTION:This report describes an original case of a multicentric diffuse low-grade glioma, with a right occipitotemporal tumor and a left anterior temporoinsular tumor. Awake surgery for the right occipitotemporal lesion, involving fusiform and inferior occipital gyri and ILF, was achieved in a first step without causing any neurologic deficit. A subsequent resection of the left anterior temporoinsular lesion, with removal of the anterior left ILF, was achieved 1 year later. Surprisingly, the patient experienced a strong and permanent prosopagnosia after this second surgery.CONCLUSIONS:The authors investigate the possible causes resulting in this prosopagnosia. Specifically, they suggest a decompensation within a reorganized neural network after the first operation, because of a disconnection syndrome induced by a bilateral surgical damage of the ventral occipitotemporal structural connectivity. These original data can be useful for neurosurgeons, especially when achieving resection for multicentric tumors involving both ventral streams, to inform patients before surgery about the possible risk of face recognition deficit, and to adapt the cognitive tasks intraoperatively during awake procedure.

International audience; BACKGROUNDInsular glioma surgery still represents a challenge. Nonetheless, advances in microsurgical anatomy and brain mapping techniques have allowed an increase in the extent of resection with acceptable morbidity rates. Transsylvian and transcortical approaches constitute the main surgical corridors, the latter providing considerable advantages and a high degree of reliability. Nevertheless, both surgical corridors yield remarkable difficulties in reaching the most posterior insular region.OBJECTIVETo study the feasibility of an endoscopic transtemporal approach in brain specimens, with the aim to provide a suitable access for posterior insular region.METHODSFour postmortem human hemispheres, embalmed using Klingler's technique, were dissected by means of a 30° rigid endoscope. The specimens underwent magnetic resonance imaging scans and, using the neuronavigation system, we were able to design a safe cortical window and an optimized endoscopic trajectory for the posterior insular dissection.RESULTSInsular dissection was led subpially through a small 2-cm cortical access, located in the anterior part of the middle temporal gyrus. During the posterior insula dissection, the endoscope allowed for optimized surgical view all along the long gyri, up to the posterior insular point. Anterior insular dissection was accomplished with more difficulties, as the endoscopic trajectory was not aligned to the axis of the short gyri.CONCLUSIONThis new surgical approach provides a favorable transcortical access to reach the most posterior insular portion. It seems to be a promising tool, in combination with intraoperative functional brain mapping, to further improve extent of resection rates in insular glioma surgery.

Background Isolated oculomotor nerve palsy (ONP) is caused most commonly by vascular disease, posterior circulation aneurysms, and inflammatory or traumatic injury. ONP usually occurs in chronic subdural hematoma (CSDH) as a common sign of cerebral herniation that typically is associated with a deterioration of consciousness. Case Description We report 2 cases of bilateral CSDH who presented with ONP without deterioration of consciousness. An extensive literature review revealed this is an extremely rare finding. We also investigated all the possible pathogenic mechanisms producing nerve impairment and found a strong association with bilateral subdural hematoma. Vascular compression between posterior circulation arteries and tentorial edge abnormalities also could be involved. Vulnerability of the oculomotor nerve seems to be a necessary condition leading to clinical onset and is caused by predisposing factors to nerve damage, including vascular disease, head trauma, or herpes zoster infection. Conclusions Although isolated ONP is a very rare presentation of CSDH, a differential diagnosis is absolutely necessary, because surgical treatment allows good recovery of third nerve palsy in most of the cases.