Educational stereoscopic representation of a step-by-step brain white fiber dissection according to Klingler's method.

BACKGROUND: Understanding and teaching the three-dimensional architecture of the brain remains difficult because of the intricate arrangement of grey nuclei within white matter tracts. Although cortical area functions have been well studied, educational and three-dimensional descriptions of the organization of deep nuclei and white matter tracts are still missing. OBJECTIVE: We propose herein a detailed step-by-step dissection of the lateral aspect of a left hemisphere using the Klingler method and provide high-quality stereoscopic views with the aim to help teach medical students or surgeons the three-dimensional anatomy of the brain. METHODS: Three left hemispheres were extracted and prepared. Then, according to the Klingler method, dissections were carried out from the lateral aspect. Photographs were taken at each step and were modified to provide stereoscopic three-dimensional views. RESULTS: Gray and white structures were described: cortex, claustrum, putamen, pallidum, caudate nucleus, amygdala; U-fibers, external and internal capsules, superior longitudinal fasciculus, frontal aslant fasciculus, uncinate fasciculus, inferior fronto-occipital fasciculus, inferior longitudinal fasciculus, corticospinal fasciculus, corona radiata, anterior commissure, and optic radiations. CONCLUSION: This educational stereoscopic presentation of an expert dissection of brain white fibers and basal ganglia would be of value for theoretical or hands-on teaching of brain anatomy; labeling and stereoscopy could, moreover, improve the teaching, understanding, and memorizing of brain anatomy. In addition, this could be also used for the creation of a mental map by neurosurgeons for the preoperative planning of brain tumor surgery.

Limbic Stimulation Drives Mania in STN-DBS in Parkinson Disease: A Prospective Study.

In this one-year prospective study, Parkinson's disease (PD) patients with or without mania following STN-DBS were compared to investigate risk and etiological factors, clinical management and consequences. Eighteen (16.2%) out of 111 consecutive PD patients developed mania, of whom 17 were males. No preoperative risk factor was identified. Postoperative mania was related to ventral limbic subthalamic stimulation in 15 (83%) patients, and resolved as stimulation was relocated to the sensorimotor STN, besides discontinuation or reduction of dopamine agonists and use of low-dose clozapine in 12 patients, while motor and nonmotor outcomes were similar. These findings underpin the prominent role of limbic subthalamic stimulation in postoperative mania. ANN NEUROL 2022;92:411-417.

Comparison of clinical outcomes and accuracy of electrode placement between robot-assisted and conventional deep brain stimulation of the subthalamic nucleus: a single-center study.

BACKGROUND: Several surgical methods are used for deep brain stimulation (DBS) of the subthalamic nucleus (STN) in Parkinson's disease (PD). This study aimed to compare clinical outcomes and electrode placement accuracy after robot-assisted (RAS) versus frame-based stereotactic (FSS) STN DBS in Parkinson's disease. METHODS: In this single-center open-label study, we prospectively collected data from 48 consecutive PD patients who underwent RAS (Neuromate®; n = 20) or FSS (n = 28) STN DBS with the same MRI-based STN targeting between October 2016 and December 2018 in the university neurological hospital of Lyon, France. Clinical variables were assessed before and 1 year after surgery. The number of electrode contacts within the STN was determined by merging post-operative CT and pre-operative MRI using Brainlab® GUIDE™XT software. RESULTS: One year after surgery, the improvement of motor manifestations (p = 0.18), motor complications (p = 0.80), and quality of life (p= 0.30) and the reduction of dopaminergic treatment (p = 0.94) and the rate of complications (p = 0.99) were similar in the two groups. Surgery duration was longer in the RAS group (p = 0.0001). There was no difference in the number of electrode contacts within the STN. CONCLUSION: This study demonstrates that RAS and FSS STN DBS for PD provide similar clinical outcomes and accuracy of electrode placement.

How Should we Use Multicolumn Spinal Cord Stimulation to Optimize Back Pain Spatial Neural Targeting? A Prospective, Multicenter, Randomized, Double-Blind, Controlled Trial (ESTIMET Study).

BACKGROUND: Recent studies have highlighted multicolumn spinal cord stimulation (SCS) efficacy, hypothesizing that optimized spatial neural targeting provided by new-generation SCS lead design or its multicolumn programming abilities could represent an opportunity to better address chronic back pain (BP). OBJECTIVE: To compare multicolumn vs. monocolumn programming on clinical outcomes of refractory postoperative chronic BP patients implanted with SCS using multicolumn surgical lead. MATERIALS AND METHODS: Twelve centers included 115 patients in a multicenter, randomized, double-blind, controlled trial. After randomization, leads were programmed using only one or several columns. The primary outcome was change in BP visual analogic scale (VAS) at six months. All patients were then programmed using the full potential of the lead up until 12-months follow-up. RESULTS: At six months, there was no significant difference in clinical outcomes whether the SCS was programmed using a mono or a multicolumn program. At 12 months, in all patients having been receiving multicolumn SCS for at least six months (n = 97), VAS decreases were significant for global pain (45.1%), leg pain (55.8%), and BP (41.5%) compared with baseline (p < 0.0001). CONCLUSION: The ESTIMET study confirms the significant benefit experienced on chronic BP by patients implanted with multicolumn SCS, independently from multicolumn lead programming. These good clinical outcomes might result from the specific architecture of the multicolumn lead, giving the opportunity to select initially the best column on a multicolumn grid and to optimize neural targeting with low-energy requirements. However, involving more columns than one does not appear necessary, once initial spatial targeting of the "sweet spot" has been achieved. Our findings suggest that this spatial concept could also be transposed to cylindrical leads, which have drastically improved their capability to shape the electrical field, and might be combined with temporal resolution using SCS new modalities.

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.

The 360 photography: a new anatomical insight of the sphenoid bone. Interest for anatomy teaching and skull base surgery.

Skull base architecture is tough to understand because of its 3D complex shape and its numerous foramen, reliefs or joints. It is especially true for the sphenoid bone whom central location hinged with most of skull base components is unique. Recently, technological progress has led to develop new pedagogical tools. This way, we bought a new real-time three-dimensional insight of the sphenoid bone that could be useful for the teacher, the student and the surgeon. High-definition photography was taken all around an isolated dry skull base bone prepared with Beauchêne's technique. Pictures were then computed to provide an overview with rotation and magnification on demand. From anterior, posterior, lateral or oblique views and from in out looks, anatomical landmarks and subtleties were described step by step. Thus, the sella turcica, the optic canal, the superior orbital fissure, the sphenoid sinus, the vidian canal, pterygoid plates and all foramen were clearly placed relative to the others at each face of the sphenoid bone. In addition to be the first report of the 360 Photography tool, perspectives are promising as the development of a real-time interactive tridimensional space featuring the sphenoid bone. It allows to turn around the sphenoid bone and to better understand its own special shape, numerous foramen, neurovascular contents and anatomical relationships. This new technological tool may further apply for surgical planning and mostly for strengthening a basic anatomical knowledge firstly introduced.

Assessment of vinyl polysiloxane as an innovative injection material for the anatomical study of vasculature.

There are numerous injection materials for the study of vasculature in anatomical specimens, each having its own advantages and disadvantages. Latex and resins are the most widely used injection materials but need several days to set. The development of new materials taking shorter time to polymerize might be very useful to improve anatomic specimen study conditions. The aim of the present study was to evaluate vinyl polysiloxane (VPS), a silicon material widely used for dental impressions with the advantage to set very rapidly, as an injection material. We assessed the preparation, use, diffusion and setting time of the product in different anatomical regions (central nervous system, external carotid/jugular, lower limb) to observe its behavior in variably sized vessels. Our results suggest that VPS might be of interest for the study of vessels in anatomical specimens. The main strengths of the product are represented by (1) simplicity of use, as it is a ready-to-use material, (2) very rapid polymerization, (3) availability in a range of viscosities making easier the exploration of small vessels, (4) its better elasticity compared to resins, (5) and finally its availability in a range of colors making it a material of choice for vascular system dissections including those with very small caliber vessels.

Anatomic comparison of anterior petrosectomy versus the expanded endoscopic endonasal approach: interest in petroclival tumors surgery.

PURPOSE: Since the petroclival region is deep-seated with close neurovascular relationships, the removal of petroclival tumors still represents a fascinating surgical challenge. Although the classical anterior petrosectomy (AP) offers a meaningful access to this petroclival region, the expanded endoscopic endonasal approach (EEEA) recently leads to overcome difficulties from trans-cranial approaches. Herein, we present an anatomic comparison of AP versus EEEA. We aim to describe the limits of these both approaches helping the choice of the optimal surgical route for petroclival tumors. METHODS: Six fresh cadaveric heads were harvested and injected with colored latex. Each approach was step-by-step detailed until its final surgical exposure. RESULTS: The AP provided a narrow direct supero-lateral access to the petroclival area that can also reach the cavernous sinus, the retrochiasmatic region and perimesencephalic cisterns. However, this corridor anterior to the internal acoustic meatus passed on each side of the trigeminal nerve. Moreover, tumor extensions toward the foramen jugularis, inside the clivus or behind the internal acoustic meatus were difficult to control. The EEEA brought a straightforward access to the clivus but the petrous apex was hidden behind the internal carotid artery. Several variants were described: a medial transclival, a lateral through the Meckel's cave and an inferior trans-pterygoid route. Elsewhere, tumor extension behind the internal acoustic meatus or above the tentorium could not be satisfactorily assessed. DISCUSSION AND CONCLUSION: PA and EEEA have their own limits in reaching the petroclival region in accordance with the tumor characteristics. The AP should be preferred for radical removal of middle-sized petrous apex intradural tumors like meningiomas. The EEEA would be of interest for extradural midline tumors like chordomas or for petrous apex cysts drainage.

What is the dorsal median sulcus of the spinal cord? Interest for surgical approach of intramedullary tumors.

PURPOSE: For intramedullary tumor (IMT) surgery, a balance has to be found between aggressively resecting the tumor and respecting all the sensory and motor pathways. The most common surgical approach is through the dorsal median sulcus (DMS) of the spinal cord. However, the precise organization of the meningeal sheats in the DMS remains obscure in the otherwise well-described anatomy of the spinal cord. A better understanding of this architecture may be of benefit to IMT surgeon to spare the spinal cord. METHODS: Three spinal cords were studied. The organization of the spinal cord meninges in the DMS was described via macroscopic, microsurgical and optical microscopic views. A micro dissection of the DMS was also performed. RESULTS: No macroscopic morphological abnormalities were observed. With the operative magnifying lens, the dura was opened, the arachnoid was removed and the pia mater was cut to access the DMS. The histological study showed that the DMS was composed of a thin rim of capillary-carrying connective tissue extending from the pia mater and covering the entire DMS. There was no true space between the dorsal columns, no arachnoid or crossing axons either. CONCLUSION: Our work indicates that the DMS is not a sulcus but a thin blade of collagen extending from the pia mater. Its location is given by tiny vessels coming from the surface towards the deep. Thus, the surgical corridor has to follow the DMS as closely as possible to prevent damage to the spinal cord during midline IMT removal.

Morphometry and localization of the temporal transverse Heschl's gyrus in magnetic resonance imaging: a guide for cortical stimulation of chronic tinnitus.

PURPOSE: Subjective tinnitus is considered a phantom auditory phenomenon. Recent studies show that electrical or magnetic stimulation of the cortex can alleviate some tinnitus. The usual target of the stimulation is the primary auditory cortex (PAC) on Heschl's gyrus (HG). The objective of this study was to specify the anatomy of HG by magnetic resonance imaging (MRI). METHODS: Cerebral MRI of 60 patients with chronic tinnitus, carried out before neuronavigated repetitive transcranial magnetic stimulation targeting the auditory cortex, were included. 3D-T1 MRI was reformatted in Talairach-Tournoux's stereotactic space, then the following steps were performed: morphometry of HG, localization of the probabilistic center of the PAC (pcPAC) chosen at the junction between the medial third and the lateral two-thirds of HG, relative to external and cortical landmarks, and identification of its coordinates relative to the bicommissural line (AC-PC). RESULTS: In relation to external landmarks, the pcPAC was identified around 5 cm above the root of the helix of the ear in the direction of a point on the vertex located 4 cm behind the coronal suture, for both sides. In Talairach-Tournoux's stereotactic space with the anterior commissure as the origin, the pcPAC coordinates were x = 43, y = -20, z = 6.8 on the right side, and x = -42.5, y = -21.5, and z = 6.5 on the left. Probabilistic maps of the presence of HG pointed to a relative contraction of data in space, despite inter- and intraindividual differences. CONCLUSION: The choice of our stimulation target was established in the middle of the theoretical position of the PAC. MRI allows a reliable identification of the target structure.

Better Fields or Currents? A Head-to-Head Comparison of Transcranial Magnetic (rTMS) Versus Direct Current Stimulation (tDCS) for Neuropathic Pain.

While high-frequency transcranial magnetic stimulation (HF-rTMS) is now included in the armamentarium to treat chronic neuropathic pain (NP), direct-current anodal stimulation (a-tDCS) to the same cortical targets may represent a valuable alternative in terms of feasibility and cost. Here we performed a head-to-head, randomized, single-blinded, cross-over comparison of HF-rTMS versus a-tDCS over the motor cortex in 56 patients with drug-resistant NP, who received 5 daily sessions of each procedure, with a washout of at least 4 weeks. Daily scores of pain, sleep, and fatigue were obtained during 5 consecutive weeks, and functional magnetic resonance imaging (fMRI) to a motor task was performed in a subgroup of 31 patients. The percentage of responders, defined by a reduction in pain scores of > 2 SDs from pre-stimulus levels, was similar to both techniques (42.0% vs. 42.3%), while the magnitude of "best pain relief" was significantly skewed towards rTMS. Mean pain ratings in responders decreased by 32.6% (rTMS) and 29.6% (tDCS), with half of them being sensitive to only one technique. Movement-related fMRI showed significant activations in motor and premotor areas, which did not change after 5 days of stimulation, and did not discriminate responders from non-responders. Both HF-rTMS and a-tDCS showed efficacy at 1 month in drug-resistant NP, with magnitude of relief slightly favoring rTMS. Since a significant proportion of patients responded to one procedure only, both modalities should be tested before declaring a patient as unresponsive.

Anatomical study of the thoracolumbar radiculomedullary arteries, including the Adamkiewicz artery and supporting radiculomedullary arteries.

OBJECTIVE: The aim of this paper was to identify and characterize all the segmental radiculomedullary arteries (RMAs) that supply the thoracic and lumbar spinal cord. METHODS: All RMAs from T4 to L5 were studied systematically in 25 cadaveric specimens. The RMA with the greatest diameter in each specimen was termed the artery of Adamkiewicz (AKA). Other supporting RMAs were also identified and characterized. RESULTS: A total of 27 AKAs were found in 25 specimens. Twenty-two AKAs (81%) originated from a left thoracic or a left lumbar radicular branch, and 5 (19%) arose from the right. Two specimens (8%) had two AKAs each: one specimen with two AKAs on the left side and the other specimen with one AKA on each side. Eight cadaveric specimens (32%) had 10 additional RMAs; among those, a single additional RMA was found in 6 specimens (75%), and 2 additional RMAs were found in each of the remaining 2 specimens (25%). Of those specimens with a single additional RMA, the supporting RMA was ipsilateral to the AKA in 5 specimens (83%) and contralateral in only 1 specimen (17%). The specimens containing 2 additional RMAs were all (100%) ipsilateral to their respective AKAs. CONCLUSIONS: The segmental RMAs supplying the thoracic and lumbar spinal cord can be unilateral, bilateral, or multiple. Multiple AKAs or additional RMAs supplying a single anterior spinal artery are common and should be considered when dealing with the spinal cord at the thoracolumbar level.

Anatomical study of the central myelin portion and transitional zone of the vestibulocochlear nerve.

BACKGROUND: The aim of this study was to evaluate gross and microscopic anatomical features of the vestibulocochlear nerve or eighth cranial nerve (CNVIII) from fresh cadavers, especially the nerve's central myelin portion (CMP) and transitional zone (TZ), and to consider any pathological implications. METHODS: Six fresh cadavers were used to examine the CNVIII. Its cisternal length from brainstem to internal auditory meatus was measured. Longitudinal sections were stained to make following measurements: the diameter where the nerve enters the brainstem, the diameter where the TZ begins, the distance to the most distal part of TZ from the brainstem, and the depth of the TZ. The volume of the CMP was calculated as well. RESULTS: The cisternal length of ten CNVIIIs measured between 14.2 and 19.2 mm (16.48 ± 1.78 mm). The thickness where the CNVIII enters the brainstem was between 1.21 and 3.16 mm (2.31 ± 0.68 mm); the thickness where the TZ begins was between 1.07 and 2.21 mm (1.44 ± 0.38 mm); the distance of the most distal part of the TZ from the brainstem was between 9.28 and 13.84 mm (11.50 ± 1.56 mm); the depth of the TZ was between 0.56 and 1.28 mm (0.81 ± 0.27 mm). The volume of the CMP was between 17.34 and 53.87 mm(3) (33.98 ± 13.74 mm(3)). The measurements were compared to trigeminal, facial, glossopharyngeal and vagus nerves. CNVIII was the nerve with the longest CMP. CONCLUSIONS: The measurements showed that the CMP of CNVIII was very long. The implication of this length in the dysfunctional syndromes of this nerve, its propensity to harbor schwannomas, which most frequently arise at the porus of the auditory meatus, and the vulnerability to damages are discussed.

The endoscopic trans-fourth ventricle aqueductoplasty and stent placement for the treatment of trapped fourth ventricle: long-term results in a series of 18 consecutive patients.

BACKGROUND: Different surgical approaches have been described in the past to treat a trapped fourth ventricle (TFV) but, unfortunately, these techniques showed a high rate of dysfunction and complications. During the last 10 years the development of neuroendoscopy has dramatically changed the outcome of these patients. MATERIALS AND METHODS: We conducted a retrospective evaluation of the safety, effectiveness, and long-term outcome of endoscopic aqueductoplasty and stent placement, performed in 18 consecutive patients with symptomatic TFV through a trans-fourth ventricle approach between 1994 and 2010. Thirteen patients underwent endoscopic aqueductoplasty and stent placement and 5 patients underwent aqueductoplasty alone using a tailored suboccipital approach through the foramen of Magendie in prone or sitting position. RESULTS: The mean age of the patients at the time of surgery was 15.2 years. All patients but 3 had a supratentorial ventriculoperitoneal shunt. Fifteen patients presented with slit supratentorial ventricles. At a mean followup of 90.8 months all patients experienced a stable clinical improvement. Only two complications were observed: A transient diplopia due to dysconjugate eye movements in one patient and a transient trochlear palsy in another one. CONCLUSIONS: Our experience and the literature review suggest that endoscopic trans-fourth ventricle aqueductoplasty and stent placement is a minimally invasive, safe, and effective technique for the treatment of TFV and should be strongly recommended, especially in patients with supratentorial slit ventricles.

Cranial and Cerebral Anatomic Key Points for Neurosurgery: A New Educational Insight.

BACKGROUND: The anatomy of both the skull and the brain offers many landmarks that could lead surgery. Cranial "craniometric" key points were described many years ago, and then, cerebral key points-along sulci and gyri-were detailed more recently for microneurosurgical approaches that can reach deep structures while sparing the brain. Nonetheless, this anatomic knowledge is progressively competed by new digital devices, such as imaging guidance systems, although they can be misleading. OBJECTIVE: To summarize cranial and sulcal key points and their related anatomic structures to renew their interest in modern neurosurgery and help surgical anatomy teaching. METHODS: After a literature review collecting anatomic key points of skull and brain, specimens were prepared and images were taken to expose skull and brain from lateral, superior, posterior, and oblique views. A high-definition camera was used, and images obtained were modified, superimposing both key points and underlying anatomic structures. RESULTS: From 4 views, 16 cranial key points were depicted: anterior and superior squamous point, precoronal and retrocoronal point, superior sagittal point, intraparietal point, temporoparietal point, preauricular point, nasion, bregma, stephanion, euryon, lambda, asterion, opisthocranion, and inion. These corresponded to underlying cerebral key points and relative brain parts: anterior and posterior sylvian point, superior and inferior rolandic point, supramarginal and angular gyri, parieto-occipital sulcus, and various meeting points between identifiable sulci. Stereoscopic views were also provided to help learning these key points. CONCLUSION: This comprehensive overview of the cranial and sulcal key points could be a useful tool for any neurosurgeon who wants to check her/his surgical route and make the surgery more "gentle, safe, and accurate."

Treatment of Chiari type I malformation in children: the experience of Lyon.

The Chiari I malformation represents a complex disease and its pathophysiology is not completely understood and consequently different surgical procedures have been proposed in the literature. The use of MRI have increased the diagnosis of Chiari I malformation but generally the Chiari I is characterized by the herniation of tonsils at 5 mm below the plane of the occipital hole. The consequent disturbance of the CSF circulation at the level of the cranio-vertebral junction favors the occurrence of the syrinx between 20 and 70% of cases in pediatric series. Different surgical techniques have been proposed. We report two series of patients treated with the same surgical procedure except for the use of a Goretex dural patch in the second group with better clinical results. Our experience seems to confirm that the Chiari I malformation is a complex disease in which the impairment of the CSF circulation plays an important role to explain the severity of the clinical picture. The bone decompression and the restauration of the CSF circulation with a dural patch with Goretex seems to be effective for improving the clinical picture with good results.

Cranial nerve vascular compression syndromes of the trigeminal, facial and vago-glossopharyngeal nerves: comparative anatomical study of the central myelin portion and transitional zone; correlations with incidences of corresponding hyperactive dysfunctional syndromes.

OBJECTIVE: The aim of this study was to evaluate the anatomy of the central myelin portion and the central myelin-peripheral myelin transitional zone of the trigeminal, facial, glossopharyngeal and vagus nerves from fresh cadavers. The aim was also to investigate the relationship between the length and volume of the central myelin portion of these nerves with the incidences of the corresponding cranial dysfunctional syndromes caused by their compression to provide some more insights for a better understanding of mechanisms. METHODS: The trigeminal, facial, glossopharyngeal and vagus nerves from six fresh cadavers were examined. The length of these nerves from the brainstem to the foramen that they exit were measured. Longitudinal sections were stained and photographed to make measurements. The diameters of the nerves where they exit/enter from/to brainstem, the diameters where the transitional zone begins, the distances to the most distal part of transitional zone from brainstem and depths of the transitional zones were measured. Most importantly, the volume of the central myelin portion of the nerves was calculated. Correlation between length and volume of the central myelin portion of these nerves and the incidences of the corresponding hyperactive dysfunctional syndromes as reported in the literature were studied. RESULTS: The distance of the most distal part of the transitional zone from the brainstem was 4.19 ± 0.81 mm for the trigeminal nerve, 2.86 ± 1.19 mm for the facial nerve, 1.51 ± 0.39 mm for the glossopharyngeal nerve, and 1.63 ± 1.15 mm for the vagus nerve. The volume of central myelin portion was 24.54 ± 9.82 mm(3) in trigeminal nerve; 4.43 ± 2.55 mm(3) in facial nerve; 1.55 ± 1.08 mm(3) in glossopharyngeal nerve; 2.56 ± 1.32 mm(3) in vagus nerve. Correlations (p < 0.001) have been found between the length or volume of central myelin portions of the trigeminal, facial, glossopharyngeal and vagus nerves and incidences of the corresponding diseases. CONCLUSION: At present it is rather well-established that primary trigeminal neuralgia, hemifacial spasm and vago-glossopharyngeal neuralgia have as one of the main causes a vascular compression. The strong correlations found between the lengths and volumes of the central myelin portions of the nerves and the incidences of the corresponding diseases is a plea for the role played by this anatomical region in the mechanism of these diseases.

Anatomical and Histological Analysis of a Complex Structure Too Long Considered a Simple Ligament: The Filum Terminale.

BACKGROUND: The intradural filum terminale (iFT) connects the conus medullaris (CM) with the dural sac (DS), and the extradural filum terminale (eFT) connects the DS to the coccyx. The aim of the present study was to update the description of the FT and integrate these data in a physiological and pathological context. METHODS: Anatomical measurements and histological investigations were performed on 10 human cadavers. RESULTS: The mean length of the iFT and eFT was 167.13 and 87.59 mm, respectively. The mean cranial diameter of the iFT was 1.84 mm. It was >2 mm in 2 specimens. The mean half and caudal diameter of the iFT was 0.71 and 0.74 mm, respectively. The cranial diameter of the eFT correlated with the caudal diameter of the eFT (ρ = 0.94; P = 0.02). The level of the CM-iFT junction correlated significantly with the iFT length (ρ = -0.67; P = 0.03). The mobilization of the iFT was not transmitted to the extradural elements and vice versa. The iFT contained axons and ependymal cells, which were dense in the first third and then randomly arranged caudally in islets. This could explain why ependymomas can occur all along the iFT. Ganglion cells were abundant around the junction with the DS. The eFT contained smooth muscle cells, adipocytes, and axons. A mechanoreceptor was identified in 1 specimen. CONCLUSIONS: Consistently with their common embryological origin, a real anatomical and histological continuum is present between the CM and FT. The FT should, therefore, no longer be considered a simple ligament but, rather, a complex fibrocellular structure.