Value of Spinal Cord Diffusion Imaging and Tractography in Providing Predictive Factors for Tumor Resection in Patients with Intramedullary Tumors: A Pilot Study.

This pilot study aimed to investigate the interest of high angular resolution diffusion imaging (HARDI) and tractography of the spinal cord (SC) in the management of patients with intramedullary tumors by providing predictive elements for tumor resection. Eight patients were included in a prospective study. HARDI images of the SC were acquired using a 3T MRI scanner with a reduced field of view. Opposed phase-encoding directions allowed distortion corrections. SC fiber tracking was performed using a deterministic approach, with extraction of tensor metrics. Then, regions of interest were drawn to track the spinal pathways of interest. HARDI and tractography added value by providing characteristics about the microstructural organization of the spinal white fibers. In patients with SC tumors, tensor metrics demonstrated significant changes in microstructural architecture, axonal density, and myelinated fibers (all, p < 0.0001) of the spinal white matter. Tractography aided in the differentiation of tumor histological types (SC-invaded vs. pushed back by the tumor), and differentiation of the spinal tracts enabled the determination of precise anatomical relationships between the tumor and the SC, defining the tumor resectability. This study underlines the value of using HARDI and tractography in patients with intramedullary tumors, to show alterations in SC microarchitecture and to differentiate spinal tracts to establish predictive factors for tumor resectability.

Atlas-guided brain projection tracts: From regions of interest to tractography 3D rendering.

The use of diffusion tensor imaging (DTI) has seen significant development over the last two decades, in particular with the development of the tractography of association tracts for preoperative planning of surgery. However, projection tracts are difficult to differentiate from one another and tractography studies have failed to reconstruct these ascending/descending pathways from/to the spinal cord. The present study proposes an atlas of regions of interest (ROIs) designed specifically for projection tracts tractography. Forty-nine healthy subjects were included in this prospective study. Brain DTI was acquired using the same 3 T MRI scanner, with 32 diffusion directions. Distortions were corrected using the FSL software package. ROIs were drawn using the anterior commissure (AC)-posterior commissure (PC) line on the following landmarks: the pyramid for the corticospinal tract, the medio-caudal part of the red nucleus for the rubrospinal tract, the pontine reticular nucleus for corticoreticular tract, the superior and inferior cerebellar peduncles for, respectively, the anterior and posterior spinocerebellar tract, the gracilis and cuneatus nucleus for the dorsal columns, and the ventro-posterolateral nucleus for the spinothalamic tract. Fiber tracking was performed using a deterministic algorithm using DSI Studio software. ROI coordinates, according to AC-PC line, were given for each tract. Tractography was obtained for each tract, allowing tridimensional rendering and comparison of tracking metrics between tracts. The present study reports the accurate design of specific ROIs for tractography of each projection tract. This could be a useful tool in order to differentiate projection tracts at the spinal cord level.

The Impact of Neurophysiological Monitoring during Intradural Spinal Tumor Surgery.

Surgery for spinal cord tumors poses a significant challenge due to the inherent risk of neurological deterioration. Despite being performed at numerous centers, there is an ongoing debate regarding the efficacy of pre- and intraoperative neurophysiological investigations in detecting and preventing neurological lesions. This study begins by providing a comprehensive review of the neurophysiological techniques commonly employed in this context. Subsequently, we present findings from a cohort of 67 patients who underwent surgery for intradural tumors. These patients underwent preoperative and intraoperative multimodal somatosensory evoked potentials (SSEPs) and motor evoked potentials (MEPs), with clinical evaluation conducted three months postoperatively. The study aimed to evaluate the neurophysiological, clinical, and radiological factors associated with neurological outcomes. In univariate analysis, preoperative and intraoperative potential alterations, tumor size, and ependymoma-type histology were linked to the risk of worsening neurological condition. In multivariate analysis, only preoperative and intraoperative neurophysiological abnormalities remained significantly associated with such neurological deterioration. Interestingly, transient alterations in intraoperative MEPs and SSEPs did not pose a risk of neurological deterioration. The machine learning model we utilized demonstrated the possibility of predicting clinical outcome, achieving 84% accuracy.

Evaluation of the long-term effect of selective tibial neurotomy for the treatment of spastic foot using a personal goal-centered approach.

OBJECTIVE: The objective of this study was to evaluate the long-term effectiveness of selective tibial neurotomy (STN) for the treatment of the spastic foot using a goal-centered approach. METHODS: Between 2011 and 2018, adult patients with a spastic foot (regardless of etiology) who received STN followed by a rehabilitation program were included. The primary outcome was the achievement of individual goals defined preoperatively (T0) and compared at 1-year (T1) and 5-year (T5) follow-up by using the Goal Attainment Scaling methodology (T-score). The secondary outcomes were the presence of spastic deformities (equinus, varus, and claw toes), modified Ashworth scale (MAS) score for the targeted muscles, and modified Rankin Scale (mRS) score at T0, T1, and T5. RESULTS: Eighty-eight patients were included. At T5, 88.7% of patients had achieved their goals at least "as expected." The mean T-score was significantly higher at T1 (62.5 ± 9.5) and T5 (60.6 ± 11.3) than at T0 (37.9 ± 2.8) (p < 0.0001), and the difference between T1 and T5 was not significant (p = 0.2). Compared to T0, deformities (equinus, varus, and claw toes; all p < 0.0001), MAS score (p < 0.0001), and mRS score (p < 0.0001) were significantly improved at T1 and T5. Compared to T1, MAS score increased slightly only at T5 (p = 0.05) but remained largely below the preoperative value. There was no difference between T1 and T5 regarding other clinical parameters (e.g., deformities, walking abilities, mRS score). CONCLUSIONS: This study found that STN associated with a postoperative rehabilitation program can enable patients to successfully achieve personal goals that are sustained within a 5-year follow-up period.

Locked-in syndrome after central pontine myelinolysis, an outstanding outcome of two patients.

OBJECTIVE: Central pontine myelinolysis (CPM) is a rare demyelinating disease that affects the pons and which can cause extreme disabilities such as locked-in syndrome (LIS) in the initial phase. The aim of the study was to describe the evolution over a 12-month period of two patients with CPM causing an initial LIS. METHOD: We retrospectively report the unexpected clinical outcome of these two patients in relation with the anatomical damages documented by brain MRI, associated with diffusion tensor imaging and reconstruction of corticospinal tracts in tractography. The following clinical parameters systematically assessed at 3, 6, 9, and 12 months: muscle testing on 12 key muscles (Medical Research Council), prehension metrics (box and block test and purdue pegboard), and independence for acts of daily living (functional independence measure). RESULTS: Both patients showed a progressive recovery beginning between 2 and 3 months after the onset of symptoms, leading to almost complete autonomy at 12 months (FIM > 110), with motor strength greater than 4/5 in all joint segments (MRC > 50/60). On brain MRI with tractography, CST appeared partially preserved at pons level. INTERPRETATION: The possibility of a near-complete functional recovery at 12 months is important to consider given the ethical issues at stake and the discussions about limiting care that may take place initially. It seems to be the consequence of reversible myelin damage combined with partially preserved neurons. Development of collateral pathways or resolution of conduction block may explain this recovery. MRI comprising DTI and tractography could play a key role in the prognosis of motor recovery.

Spinal cord tractography and neuromonitoring-based surgical strategy for intramedullary ependymoma.

Because the spinal cord contains a rich concentration of longitudinal and transversal fibers in a very small area, intramedullary surgery could result in a high likelihood of morbidity. In this video, the authors demonstrate the microsurgical technique and surgical skills used to perform excision of an intramedullary ependyma. The authors also present tools (electrophysiology and neuroimaging) that are useful for surgical decision-making and planning, and thus are used intraoperatively, that allow safer and more effective resection of an intramedullary tumor.

Evaluation of Selective Tibial Neurotomy for the Spastic Foot Treatment Using a Personal Goal-Centered Approach: A 1-Year Cohort Study.

BACKGROUND: Selective tibial neurotomy (STN) has already demonstrated its effectiveness to reduce foot deformities and spasticity, but assessment according to a goal-centered approach is missing. OBJECTIVE: To evaluate the effectiveness of STN associated with a postoperative rehabilitation program for the treatment of the spastic foot, according to a goal-centered approach. METHODS: Interventional study (before-after STN and rehabilitation program) with observational design including consecutive adult patients with spastic foot, who received STN followed by a rehabilitation program, was performed. The primary outcome measure was the achievement of individual goals at the 1-year follow-up using the Goal Attainment Scaling methodology (with T-score). The secondary outcomes measures were the Modified Ashworth Scale and the modified Rankin Score. RESULTS: A total of 104 patients were included. At the 1-year follow-up, 228/252 (90.5%) goals were achieved: 62/252 (24.6%) were achieved as initially expected, 86/252 (34.1%) were achieved better than initially expected, and 80 (31.7%) were achieved much better than initially expected. The mean T-score was significantly increased at the 1-year follow-up (61.5 ± 10.5) compared with the preoperative period (38.1 ± 2.9, P < .00001), and 95/104 (91.3%) patients had a T-score ≥50, meaning that these patients have achieved their goals. At follow-up, spastic deformities were all significantly decreased ( P < .0001), the Modified Ashworth Scale was significantly lower for each muscle targeted ( P < .0001), and the modified Rankin Score was significantly decreased ( P < .0001) allowing the patient population to improve from a moderate to a slight disability status. CONCLUSION: This study showed that STN, associated with a postoperative rehabilitation program, successfully achieve personal goals in patients with spastic foot.

Full cervical cord tractography: A new method for clinical use.

Despite recent improvements in diffusion-weighted imaging, spinal cord tractography is not used in routine clinical practice because of difficulties in reconstructing tractograms, with a pertinent tri-dimensional-rendering, in a long post-processing time. We propose a new full tractography approach to the cervical spinal cord without extensive manual filtering or multiple regions of interest seeding that could help neurosurgeons manage various spinal cord disorders. Four healthy volunteers and two patients with either cervical intramedullary tumors or spinal cord injuries were included. Diffusion-weighted images of the cervical spinal cord were acquired using a Philips 3 Tesla machine, 32 diffusion directions, 1,000 s/mm2 b-value, 2 × 2 × 2 mm voxel size, reduced field-of-view (ZOOM), with two opposing phase-encoding directions. Distortion corrections were then achieved using the FSL software package, and tracking of the full cervical spinal cord was performed using the DSI Studio software (quantitative anisotropy-based deterministic algorithm). A unique region of avoidance was used to exclude everything that is not of the nervous system. Fiber tracking parameters used adaptative fractional anisotropy from 0.015 to 0.045, fiber length from 10 to 1,000 mm, and angular threshold of 90°. In all participants, a full cervical cord tractography was performed from the medulla to the C7 spine level. On a ventral view, the junction between the medulla and spinal cord was identified with its pyramidal bulging, and by an invagination corresponding to the median ventral sulcus. On a dorsal view, the fourth ventricle-superior, middle, and inferior cerebellar peduncles-was seen, as well as its floor and the obex; and gracile and cuneate tracts were recognized on each side of the dorsal median sulcus. In the case of the intramedullary tumor or spinal cord injury, the spinal tracts were seen to be displaced, and this helped to adjust the neurosurgical strategy. This new full tractography approach simplifies the tractography pipeline and provides a reliable 3D-rendering of the spinal cord that could help to adjust the neurosurgical strategy.

Predictors of functional outcome after spinal cord surgery: Relevance of intraoperative neurophysiological monitoring combined with preoperative neurophysiological and MRI assessments.

OBJECTIVES: To assess the accuracy of intraoperative neurophysiological monitoring (IONM) in predicting immediate and 3-month postoperative neurological new deficit (or deterioration) in patients benefiting from spinal cord (SC) surgery; and to identify factors associated with a higher risk of postoperative clinical worsening. METHODS: Consecutive patients who underwent SC surgery with IONM were included. Pre and postoperative clinical (modified McCormick scale), radiological (lesion-occupying area ratio), and electrophysiological features were collected. RESULTS: A total of 99 patients were included: 14 (14.1%) underwent extradural surgery, 50 (50.5%) intradural extramedullary surgery, and 35 (35.4%) intramedullary surgery. Cumulatively, multimodal IONM (motor and somatosensory evoked potentials, D-wave whenever possible) significantly predicted postoperative deficits (p<0.001), with a sensitivity, specificity, positive predictive value, and negative predictive value of 0.81, 0.93, 0.83, and 0.92, respectively. Sixty (60.6%) patients displayed no IONM change, whereas 39 (39.4%) displayed IONM worsening. In multivariate analysis, predictors for postoperative clinical worsening were: abnormal preoperative electrophysiological assessment (p=0.03), intramedullary tumor (p<0.001), lesion-occupying area ratio ≥0.7 (p<0.001), and IONM alterations (p<0.001). Three months after the surgical procedure, in patients presenting at least one of the risk factors described above, 45/81 (55.6%) and 19/81 (23.5%) were clinically and electrophysiologically improved, respectively; while 13/81 (16.0%) and 10/81 (12.3%) were clinically and electrophysiologically worsened. CONCLUSION: Multimodal IONM is an essential tool to guide SC surgery, and enables the accurate prediction of postoperative neurological outcome. Specific attention should be given to patients presenting with preoperative electrophysiological abnormalities, large tumor volume, and intramedullary tumor location.

Minimally Invasive Approach for Dorsal Arachnoid Web: 2-Dimensional Operative Video.

A 67-yr-old patient presented with severe paraparesis and lower limb spasticity. The spinal cord magnetic resonance imaging (MRI) revealed the "scalpel sign" 1,2 at the T7 level, suggesting a diagnosis of a dorsal arachnoid web. This video demonstrates a microsurgical technique for the excision of a dorsal arachnoid web with a minimally invasive approach. A paramedian skin incision, understanding the muscular aponeurosis, was performed from T7 to T8. Then, we inserted the tubular dilators until the lamina, to perform a muscle-sparing approach. An expandable tubular retractor of adequate length was passed over the widest dilator and docked into place along the subperiosteal plane. The T7 lamina was drilled, and the resection of the superior and inferior adjacent spine levels was completed with a rongeur. Additional contralateral bone resection was performed after tubular retractor tilt to the midline.3 After dura mater opening, it was carefully suspended and the dorsal arachnoid leaflet was cut to drain the dorsolateral and lateral spinal cisterns.4 The dorsal arachnoid web was, first, disconnected from its lateral anchorages. It was then gently removed with microsurgical forceps, to help its microdissection from the spinal cord surface. At this step, peculiar attention was paid to limit the traction or displacements of the spinal cord and surrounding vessels. Once the dorsal arachnoid web was removed, the quality of the spinal cord decompression was confirmed by its re-expansion. In conclusion, the minimally invasive approach is a safe and appropriate technique for dorsal arachnoid web excision.2,5,6-7 The patient gave her informed and signed consent for the writing and publication of this article. Image at 1:00 reused with permission from Castelnovo G et al, Spontaneous transdural spinal cord herniation, Neurology, 2014;82(14):1290.

Microsurgical DREZotomy for Treatment of Brachial Plexus Avulsion Pain.

A 63-year-old man with a history of motorcycle accident 42 years ago suffered a left brachial plexus avulsion (BPA). Neuropathic pain in his left upper limb was felt in the C6-C7-C8 dermatomes. The rationale for performing "DREZotomy" is to preferentially interrupt the nociceptive inputs in the lateral part of the dorsal root entry zone (DREZ).1-3 For pain with complete deafferentation, as observed in BPA, the aim is to destroy the hyperactive nociceptive neurons deep in the apex of the dorsal horn (DH).4 Surgery is performed under general anesthesia, with the patient in prone position. Once the dura mater is opened, the arachnoid needs extensive dissection to open the dorsolateral and lateral spinal cisterns.5 In cases of BPA, the dorsolateral sulcus may be difficult to identify. Three anatomic elements can facilitate its recognition. Firstly, the remaining intact rootlets (above and below the avulsed segments) allow us to roughly localize the dorsolateral sulcus by joining these cranial and caudal normal rootlets. Secondly, blood vessels running on the spinal cord penetrate into the dorsolateral sulcus and often delineate the sulcus. Thirdly, scarring can be seen along the sulcus with small holes where the rootlets used to penetrate the cord. DREZotomy is performed using a graduated sharp bipolar instrument to allow precise microcoagulations of the DH. Preoperative surgical planning helps the surgeon by giving the angle between the DH and median plane.6 In the immediate postoperative period, the patient described the complete disappearance of neuropathic pain in his left upper limb, persistent at last follow-up (1 year) (Video 1).

Effect of distortion corrections on the tractography quality in spinal cord diffusion-weighted imaging.

PURPOSE: To assess the impact of a different distortion correction (DC) method and patient geometry (sagittal balance) on the quality of spinal cord tractography rendering according to different tractography approaches. METHODS: Forty-four adults free of spinal cord diseases underwent cervical diffusion-weighted imaging. The phase-encoding direction was head→foot. Sequence with opposed polarities (foot→head) was acquired to perform DC. Eddy-current, motion effects, and susceptibility artifact correction methods were used for DC, and two deterministic and one probabilistic tractography approaches were evaluated using MRtrix and DSI Studio tractography software. Fiber length and number of fibers were extracted to evaluate the quality of the tractography rendering. For each subject, cervical lordosis was measured to assess patient geometry. The angle between the main direction of the spinal cord and the orientation of the acquisition box were computed at each spine level to assess acquisition geometry and define an angle threshold for which a tractography of good quality is no longer possible. RESULTS: There was a significant improvement in tractography quality after performing DC with susceptibility artifact correction using a deterministic approach based on tensor. Before DC, the angle threshold was defined at C6 (15.2°) compared with C7 (21.9°) after corrections, demonstrating the importance of spinal cord angulation for DC. CONCLUSION: The impact of DC on tractography quality is greatly impacted by acquisition geometry. To obtain a good-quality tractography, we propose as a future perspective to adapt the acquisition geometry to that of the patient by automatically adjusting the acquisition box.

Superiority of thoracolumbar injury classification and severity score (TLICS) over AOSpine thoracolumbar spine injury classification for the surgical management decision of traumatic spine injury in the pediatric population.

PURPOSE: Thoracolumbar fractures are the most common kind of spine injury in children. Several types of spine injury can occur, and for this reason, treatment algorithms have been put in place for the management of these patients. At present, the thoracolumbar injury classification and severity score system (TLICS) and the thoracolumbar AOSpine injury score (AOSpine score) aimed at providing treatment recommendations. We aimed to assess the reliability, in children, of the TLICS scoring and AOSpine scoring systems, and to define the superiority of one of the methods of scoring, to spread its use in routine clinical management in the pediatric spine trauma. METHODS: A retrospective chart review of consecutive children admitted to a Level 1 trauma center for traumatic thoracolumbar fractures, between 2006 and 2019, was performed. We compared the management we performed in clinical practice in children with spine trauma, to the decisional algorithms based on the TLICS and AOSpine scores. According to these scores, surgical treatment should be performed when the TLICS score ≥ 5 and the AOSpine score > 5; and surgical or conservative treatment was considered reasonable when the TLICS score = 4 and the AOSpine score = 4 or 5. Surgical indications were based on the clinical status, the anatomy of the fracture, and the risk of sagittal imbalance of the growing spine. RESULTS: Fifty-four patients met the inclusion criteria. We demonstrated that both the AOSpine score and the TLICS scores had a significant correlation for surgical management decision of spine trauma (p < 0.0001). We found a high concordance between surgical decision making in the pediatric clinical practice and the TLICS score. In our pediatric cohort, there were significantly more patients with TLICS ≥ 5 (n = 47, 87%) than with AOSpine score > 5 (n = 26, 46%, p < 0.0001). There were significantly more patients with TLICS ≥ 4 (n = 53, 98%), than with AOSpine score ≥ 4 (n = 42, 77%, p = 0.001). ConclusionsThe TLICS score was significantly more appropriate than the AOSpine score, for the surgical treatment decision in children, especially when considering the future risk of sagittal imbalance.

Overcoming challenges of the human spinal cord tractography for routine clinical use: a review.

The spinal cord (SC) is a dense network of billions of fibers in a small volume surrounded by bones that makes tractography difficult to perform. We aim to provide a review collecting all technical settings of SC tractography and propose the optimal set of parameters to perform a good SC tractography rendering. The MEDLINE database was searched for articles reporting "spinal cord" "tractography" in "humans". Studies were selected only when tractography rendering was displayed and MRI acquisition and tracking parameters detailed. From each study, clinical context, imaging acquisition settings, fiber tracking parameters, region of interest (ROI) design, and quality of the tractography rendering were extracted. Quality of tractography rendering was evaluated by several objective criteria proposed herein. According to the reported studies, to obtain a good tractography rendering, diffusion tensor imaging acquisition should be performed with 1.5 or 3 Tesla MRI, in the axial plane, with > 20 directions; b value: 1000 s mm-2; right-left phase-encoding direction for cervical SC; isotropic voxel size; and no slice gap. Concerning the tracking process, it should be performed with determinist approach, fractional anisotropy threshold between 0.15 and 0.2, and curvature threshold of 40°. ROI design is an essential step for providing good tractography rendering, and their placement has to consider partial volume effects, magnetic susceptibility effects, and motion artifacts. The review reported herein highlights that successful SC tractography depends on many factors (imaging acquisition settings, fiber tracking parameters, and ROI design) to obtain a good SC tractography rendering.

How I do it: selective tibial neurotomy.

BACKGROUND: Selective neurotomy is known as an effective method to reduce focal spasticity when medical treatment including botulinum toxin is not sufficient. The tibial nerve can be targeted to treat spastic equinovarus foot with (or without) claw toes. METHOD: Tibial nerve trunk is dissected in the popliteal fossa. Sensitive and motor branches are identified using electrical stimulation to monitor motor responses. The muscular nerves corresponding to the targeted muscles are partially sectioned according to a preoperative chart. A postoperative rehabilitation program is mandatory. CONCLUSION: Precise and rigorous selective neurotomy provided a definitive and safe treatment for spastic equinovarus foot.

Stereoscopic three-dimensional visualization: interest for neuroanatomy teaching in medical school.

PURPOSE: The anatomy of both the brain and the skull is particularly difficult to learn and to teach. Since their anatomical structures are numerous and gathered in a complex tridimensional (3D) architecture, classic schematical drawing or photography in two dimensions (2D) has difficulties in providing a clear, simple, and accurate message. Advances in photography and computer sciences have led to develop stereoscopic 3D visualization, firstly for entertainment then for education. In the present study, we report our experience of stereoscopic 3D lecture for neuroanatomy teaching to early medical school students. METHODS: High-resolution specific pictures were taken on various specimen dissections in the Anatomy Laboratory of the University of Lyon, France. Selected stereoscopic 3D views were displayed on a large dedicated screen using a doubled video projector. A 2-h stereoscopic neuroanatomy lecture was given by two neuroanatomists to third-year medicine students who wore passive 3D glasses. Setting up lasted 30 min and involved four people. The feedback from students was collected and analyzed. RESULTS: Among the 483 students who have attended the stereoscopic 3D lecture, 195 gave feedback, and all (100%) were satisfied. Among these, 190 (97.5%) reported a better knowledge transfer of brain anatomy and its 3D architecture. Furthermore, 167 (86.1%) students felt it could change their further clinical practice, 179 (91.8%) thought it could enhance their results in forthcoming anatomy examinations, and 150 (76.9%) believed such a 3D lecture might allow them to become better physicians. This 3D anatomy lecture was graded 8.9/10 a mean against 5.9/10 for previous classical 2D lectures. DISCUSSION-CONCLUSION: The stereoscopic 3D teaching of neuroanatomy made medical students enthusiastic involving digital technologies. It could improve their anatomical knowledge and test scores, as well as their clinical competences. Depending on university means and the commitment of teachers, this new tool should be extended to other anatomical fields. However, its setting up requires resources from faculties and its impact on clinical competencies needs to be objectively assessed.

How I do it: dorsolateral approach for ventrolateral intramedullary cavernoma.

BACKGROUND: For small and lateral lesions, in order to avoid postoperative sequelae related to dorso-median myelotomy, we propose to describe the use of a ventrolateral approach for intramedullary lesions. METHOD: Performing this approach entails that the denticulate ligament is cut from its dural attachment and retracted. Rotation of the spinal cord must be achieved with great caution and under electrophysiological monitoring. After pia mater incision, hydrodissection is useful to gently dissect the cavernoma and promote a cleavage plane. CONCLUSION: In the case of lateral intramedullary lesions, using this approach maximized the absence of postoperative deficit.

Anatomy of the human spinal cord arachnoid cisterns: applications for spinal cord surgery.

OBJECTIVE: The goal in this study was to describe the overall organization of the spinal arachnoid mater and spinal subarachnoid space (SSAS) as well as its relationship with surrounding structures, in order to highlight spinal cord arachnoid cisterns. METHODS: Fifteen spinal cords were extracted from embalmed adult cadavers. The organization of the spinal cord arachnoid and SSAS was described via macroscopic observations, optical microscopic views, and scanning electron microscope (SEM) studies. Gelatin injections were also performed to study separated dorsal subarachnoid compartments. RESULTS: Compartmentalization of SSAS was studied on 3 levels of axial sections. On an axial section passing through the tips of the denticulate ligament anchored to the dura, 3 subarachnoid cisterns were observed: 2 dorsolateral and 1 ventral. On an axial section passing through dural exit/entrance of rootlets, 5 subarachnoid cisterns were observed: 2 dorsolateral, 2 lateral formed by dorsal and ventral rootlets, and 1 ventral. On an axial section passing between the two previous ones, only 1 subarachnoid cistern was observed around the spinal cord. This compartmentalization resulted in the anatomical description of 3 elements: the median dorsal septum, the arachnoid anchorage to the tip of the denticulate ligament, and the arachnoid anchorage to the dural exit/entrance of rootlets. The median dorsal septum already separated dorsal left and right subarachnoid spaces and was described from C1 level to 3 cm above the conus medullaris. This septum was anchored to the dorsal septal vein. No discontinuation was observed in the median dorsal arachnoid septum. At the entrance point of dorsal rootlets in the spinal cord, arachnoid trabeculations were described. Using the SEM, numerous arachnoid adhesions between the ventral surface of the dorsal rootlets and the pia mater over the spinal cord were observed. At the ventral part of the SSAS, no septum was found, but some arachnoid trabeculations between the arachnoid and the pia mater were present and more frequent than in the dorsal part. Laterally, arachnoid was firmly anchored to the denticulate ligaments' fixation at dural points, and dural exit/entrance of rootlets made a fibrous ring of arachnoidodural adhesions. At the level of the cauda equina, the arachnoid mater surrounded all rootlets together-as a sac and not individually. CONCLUSIONS: Arachnoid cisterns are organized on each side of a median dorsal septum and compartmentalized in relation with the attachments of denticulate ligament and exit/entrance of rootlets.

Cysts associated with intramedullary ependymomas of the spinal cord: clinical, MRI and oncological features.

PURPOSE: Few published articles have explicitly focused on cysts associated with intramedullary (IM) ependymomas. The objective was to assess the clinical, MRI, and oncological results of patients operated for an IM ependymoma associated with a cystic portion. METHODS: During the study period, 23 IM tumors resected were cystic ependymomas. The modified McCormick scale was used to assess the neurological function of patients. The diagnosis of cystic spinal cord tumor was made on preoperative MRI. RESULTS: Two types of cysts were identified according to their location: either intra-tumoral cysts (ITC) or satellite cysts (SC). ITC (52.2%) were more frequent than SC (21.7%), but 26.1% of patients presented both. ITC were enhanced by gadolinium while SC were not. The solid portion of ependymomas with ITC was significantly larger than the one of ependymomas with SC (p = 0.002). The mean time to the first occurrence of symptoms was significantly shorter in patients with neurological deficit than those without a deficit (p = 0.04). GTR was achieved in 78.2% of cases. Complete excision of the cysts was easier when they were larger (p = 0.006). Sixty percent of cysts disappear postoperatively. Persistence of satellite cysts despite GTR of the tumor, and with no recurrence of a tumor on the post-operative MRI, was observed for 3 patients. CONCLUSION: ITC and SC are different in location, volume, gadolinium enhancement. Their surgical management is different since ITC are resected while SC are drained. Cystic recurrence and/or persistence are not synonymous with tumor recurrence.