Acta Neurochir (2013) 155:863–868
The aim of this prospective study was to evaluate whether the cerebellopontine angle (CPA) cistern area and trigeminal nerve cisternal length play a role in the pathogenesis of trigeminal neuralgia (TN).
Methods High-resolution 1.5 T magnetic resonance imaging of the posterior fossa was performed in 26 patients with TN and 18 age-matched healthy controls. Axial T2- weighted, three-dimensional constructive interference in steady-state (3D-CISS) was used to measure bilaterally the cross-sectional area of the CPA cistern and trigeminal nerve cisternal length.
Results In patients, the cross-sectional area of the CPA cistern and trigeminal nerve cisternal length was smaller on the affected side (p=0.04). Healthy controls tended to have larger cisternal areas and longer trigeminal nerve lengths than patients (p=0.059, p=0.071, respectively). Larger CPA cisternal areas tended to be seen in older patients. There was a strong correlation between the crosssectional area of the CPA cistern and the length of the trigeminal nerve (p=0.000).
Conclusions Smaller CPA cisterns and short cisternal trigeminal nerves impact the pathogenesis of essential TN by facilitating the neurovascular conflict, especially in younger patients. Trigeminal nerve cisternal measurement provides an easy and direct estimation of the CPA area. This information can be used for surgical planning and potentially for outcome prediction.
Neurosurgery 72[ONS Suppl 1]:ons35–ons46, 2013
This study proposes a 3-dimensional (3-D) template of the insula in the bicommissural reference system with posterior commissure (PC) as the center of coordinates.
OBJECTIVE: Using the bicommissural anterior commissure (AC)–PC reference system, this study aimed to define a template and design a method for the 3-D reconstruction of the human insula that may be used at an individual level during stereotactic surgery.
METHODS: Magnetic resonance imaging (MRI)–based morphometric analysis was performed on 100 cerebral cortices with normal insulae based on a 3-step procedure: Step 1: AC-PC reference system–based reconstruction of the insula from the 1-mm thick 3-D T1-weighted MRI slices. Step 2: Digitalization and superposition of the data obtained in the 3 spatial planes. Step 3: Representation of pixels as colors on a scale corresponding to the probability of localization of each insular anatomic component.
RESULTS: The morphometric analysis of the insula confirmed our previously reported findings of a more complex shape delimited by 4 peri-insular sulci. A very significant correlation between the coordinates of the main insular structures and the length of AC-PC was demonstrated. This close correlation allowed us to develop a method that allows the 3-D reconstruction of the insula from MRI slices and only requires the localization of AC and PC. This process defines an area deemed to contain insula with 100% probability.
CONCLUSION: This 3-D reconstruction of the insula should be useful to improve its localization and other cortical areas and allow the differentiation of insular cortex from opercular cortex. KEY WORDS:
Neurosurg Focus 34 (3):E4, 2013
Interest in studying the anatomy of the abducent nerve arose from early clinical experience with abducent palsy seen in middle ear infection. Primo Dorello, an Italian anatomist working in Rome in the early 1900s, studied the anatomy of the petroclival region to formulate his own explanation of this pathological entity. His work led to his being credited with the discovery of the canal that bears his name, although this structure had been described 50 years previously by Wenzel Leopold Gruber. Renewed interest in the anatomy of this region arose due to advances in surgical approaches to tumors of the petroclival region and the need to explain the abducent palsies seen in trauma, intracranial hypotension, and aneurysms. The advent of the surgical microscope has allowed more detailed anatomical studies, and numerous articles have been published in the last 2 decades. The current article highlights the historical development of the study of the Dorello canal. A review of the anatomical studies of this structure is provided, followed by a brief overview of clinical considerations.
J Neurosurg 117:1053–1069, 2012
Recent neuroimaging and surgical results support the crucial role of white matter in mediating motor and higher-level processing within the frontal lobe, while suggesting the limited compensatory capacity after damage to subcortical structures. Consequently, an accurate knowledge of the anatomofunctional organization of the pathways running within this region is mandatory for planning safe and effective surgical approaches to different diseases. The aim of this dissection study was to improve the neurosurgeon’s awareness of the subcortical anatomofunctional architecture for a lateral approach to the frontal region, to optimize both resection and postoperative outcome.
Methods. Ten human hemispheres (5 left, 5 right) were dissected according to the Klingler technique. Proceeding lateromedially, the main association and projection tracts as well as the deeper basal structures were identified. The authors describe the anatomy and the relationships among the exposed structures in both a systematic and topographical surgical perspective. Structural results were also correlated to the functional responses obtained during resections of infiltrative frontal tumors guided by direct cortico-subcortical electrostimulation with patients in the awake condition.
Results. The eloquent boundaries crucial for a safe frontal lobectomy or an extensive lesionectomy are as follows: 1) the motor cortex; 2) the pyramidal tract and premotor fibers in the posterior and posteromedial part of the surgical field; 3) the inferior frontooccipital fascicle and the superior longitudinal fascicle posterolaterally; and 4) underneath the inferior frontal gyrus, the head of the caudate nucleus, and the tip of the frontal horn of the lateral ventricle in the depth.
Conclusions. Optimization of results following brain surgery, especially within the frontal lobe, requires a perfect knowledge of functional anatomy, not only at the cortical level but also with regard to subcortical white matter connectivity.
J Neurosurg 117:839–843, 2012
Disturbance of the arcuate fasciculus in the dominant hemisphere is thought to be associated with language- processing disorders, including conduction aphasia. Although the arcuate fasciculus can be visualized in vivo with diffusion tensor imaging (DTI) tractography, its involvement in functional processes associated with language has not been shown dynamically using DTI tractography. In the present study, to clarify the participation of the arcuate fasciculus in language functions, postoperative changes in the arcuate fasciculus detected by DTI tractography were evaluated chronologically in relation to postoperative changes in language function after brain tumor surgery.
Methods. Preoperative and postoperative arcuate fasciculus area and language function were examined in 7 right-handed patients with a brain tumor in the left hemisphere located in proximity to part of the arcuate fasciculus. The arcuate fasciculus was depicted, and its area was calculated using DTI tractography. Language functions were measured using the Western Aphasia Battery (WAB).
Results. After tumor resection, visualization of the arcuate fasciculus was increased in 5 of the 7 patients, and the total WAB score improved in 6 of the 7 patients. The relative ratio of postoperative visualized area of the arcuate fasciculus to preoperative visualized area of the arcuate fasciculus was increased in association with an improvement in postoperative language function (p = 0.0039).
Conclusions. The role of the left arcuate fasciculus in language functions can be evaluated chronologically in vivo by DTI tractography after brain tumor surgery. Because increased postoperative visualization of the fasciculus was significantly associated with postoperative improvement in language functions, the arcuate fasciculus may play an important role in language function, as previously thought. In addition, postoperative changes in the arcuate fasciculus detected by DTI tractography could represent a predicting factor for postoperative language-dependent functional outcomes in patients with brain tumor.
J Neurosurg 117:839–843, 2012
Disturbance of the arcuate fasciculus in the dominant hemisphere is thought to be associated with language-processing disorders, including conduction aphasia. Although the arcuate fasciculus can be visualized in vivo with diffusion tensor imaging (DTI) tractography, its involvement in functional processes associated with language has not been shown dynamically using DTI tractography. In the present study, to clarify the participation of the arcuate fasciculus in language functions, postoperative changes in the arcuate fasciculus detected by DTI tractography were evaluated chronologically in relation to postoperative changes in language function after brain tumor surgery.
Methods. Preoperative and postoperative arcuate fasciculus area and language function were examined in 7 right-handed patients with a brain tumor in the left hemisphere located in proximity to part of the arcuate fasciculus. The arcuate fasciculus was depicted, and its area was calculated using DTI tractography. Language functions were measured using the Western Aphasia Battery (WAB).
Results. After tumor resection, visualization of the arcuate fasciculus was increased in 5 of the 7 patients, and the total WAB score improved in 6 of the 7 patients. The relative ratio of postoperative visualized area of the arcuate fasciculus to preoperative visualized area of the arcuate fasciculus was increased in association with an improvement in postoperative language function (p = 0.0039).
Conclusions. The role of the left arcuate fasciculus in language functions can be evaluated chronologically in vivo by DTI tractography after brain tumor surgery. Because increased postoperative visualization of the fasciculus was significantly associated with postoperative improvement in language functions, the arcuate fasciculus may play an important role in language function, as previously thought. In addition, postoperative changes in the arcuate fasciculus detected by DTI tractography could represent a predicting factor for postoperative language-dependent functional outcomes in patients with brain tumor.
Neurosurg Rev (2012) 35:593–599
In retrosigmoid craniotomy, neurosurgeons usually depend on surface landmarks and their experience to evaluate the position of transverse-sigmoid sinus junction (TSSJ) and place an appropriate initial burr-hole, which is not accurate each time because of variability in different craniums. The authors introduce a simple procedure based on 3D computed tomography (CT) to localize the TSSJ in retrosigmoid craniotomy.
Eighteen patients who underwent retrosigmoid craniotomy were analyzed. On the internal view of skull in 3D CT image, a simulative burr-hole was placed on the margin of transverse-sigmoid sinus groove junction. Then, on the external view of skull in 3D CT image, the center of the simulative burr-hole was marked and a coordinate system was established based on a line connected the digastric point and the asterion. Then the coordinate of the burr-hole’s center was measured in this coordinate system.
In operation, the burr-hole was placed according to the coordinate measured previously and craniotomy was performed. The margin of TSSJ was exposed in each case. No damage of venous sinus was encountered. Post-operative skull base CT demonstrated a good match between the actual and predicted burr-hole and bone defects only existed along the cut line.
This simple method could help in localizing the TSSJ and avoiding the risk of sinus injury and reducing the bone defect. It is sufficiently precise for practical application at surgical planning.
Neurosurg Focus 32 (6):E5, 2012
Lateral sphenoid encephaloceles of the Sternberg canal are rare entities and usually present with spontaneous CSF rhinorrhea. Traditionally, these were treated via transcranial approaches, which can be challenging given the deep location of these lesions.
However, with advancements in endoscopic skull base surgery, including improved surgical exposures, angled endoscopes and instruments, and novel repair techniques, these encephaloceles can be resected and successfully repaired with purely endoscopic endonasal approaches. In this report, the authors review the endoscopic endonasal transpterygoid approach to the lateral recess of the sphenoid sinus for repair of temporal lobe encephaloceles, including an overview of the surgical anatomy from an endoscopic perspective, and describe the technical operative nuances and surgical pearls for these cases.
The authors also present 4 new cases of lateral sphenoid recess encephaloceles that were successfully treated using this approach.
Neurosurgery 70[ONS Suppl 2]:ons202–ons208, 2012 DOI: 10.1227/NEU.0b013e31824042e6
Approaches to the foramen magnum and upper cervical spine traditionally include the posterior midline, far lateral, and endoscopic endonasal approaches. The far lateral approach is a well-established technique for the removal of pathology ventrolateral to the brainstem and the craniocervical junction, but it may be too extensive for lesions limited to areas far from the midline.
OBJECTIVE: To present an alternative to the commonly used approaches to the foramen magnum and upper cervical.
METHODS: We used an approach directly overlying ventral or lateral pathology.
RESULTS: Two cases are presented in which the direct lateral approach followed by an occipitocervical fusion was successfully performed.
CONCLUSION: This approach can be considered for patients in whom a ventral decompression is necessary but an endoscopic endonasal approach is undesirable or when a ventral, lateral, and ventrolateral resection of tumor, pannus, or infection is required.
Neurosurgery 70[ONS Suppl 2]:ons290–ons299, 2012.DOI: 10.1227/NEU.0b013e3182315112
Surgery within the insula carries significant risk of morbidity, particularly hemiparesis, because of the difficulty in detecting the internal capsule boundaries.
OBJECTIVE: We analyzed the anatomy of the insula and identified landmarks anticipated to facilitate surgery for intrinsic insular lesions.
METHODS: Insular region anatomy was studied in 11 cadaveric brains harvested within 72 hours postmortem. MRI of the specimens was acquired using 3.0 T with T2-weighting and 25 directions of diffusion tensor imaging. Landmarks easily recognizable during surgery were identified on the surface of the insula. The interrelationships between surface landmarks and critical structures were analyzed.
RESULTS: The posterior inferior insular point (PIIP) and the upper central insular point (UCIP) were newly established as landmarks on the insula. The PIIP corresponded to the obvious bend in the posterior long insular gyrus. The UCIP is the meeting point between the central insular sulcus and superior peri-insular sulcus. The corticospinal tract was identified as a high-intensity area in the posterior limb of the internal capsule on T2-weighted imaging and its course confirmed with diffusion tensor imaging tractography. The corticospinal tract took a course deep to the posterosuperior insula on T2-weighted imaging, 4.8 mm from the UCIP and 6.2 mm from the PIIP.
CONCLUSION: The posterosuperior part of the insula forms the region at greatest risk to corticospinal tract injury. The PIIP and UCIP are crucial to understanding the relationship of the insula with the posterior limb of the internal capsule including the corticospinal tract.
KEY WORDS:
Neurosurgery 70:1312–1319, 2012 DOI: 10.1227/NEU.0b013e31824388f8
Emissary veins connect the extracranial venous system with the intracranial venous sinuses. These include, but are not limited to, the posterior condyloid, mastoid, occipital, and parietal emissary veins.
A review of the literature for the anatomy, embryology, pathology, and surgery of the intracranial emissary veins was performed.
Detailed descriptions of these venous structures are lacking in the literature, and, to the authors’, knowledge, this is the first detailed review to discuss the anatomy, pathology, anomalies, and clinical effects of the cranial emissary veins.
Our hope is that such data will be useful to the neurosurgeon during surgery in the vicinity of the emissary veins.
J Neurosurg Spine 16:402–407, 2012. http://thejns.org/doi/abs/10.3171/2011.12.SPINE11541
Although the uncovertebral region is neurosurgically relevant, relatively little is reported in the literature, specifically the neurosurgical literature, regarding its anatomy. Therefore, the present study aimed at further elucidation of this region’s morphological features.
Methods. Morphometry was performed on the uncinate processes of 40 adult human skeletons. Additionally, range of motion testing was performed, with special attention given to the uncinate processes. Finally, these excrescences were classified based on their encroachment on the adjacent intervertebral foramen.
Results. The height of these processes was on average 4.8 mm, and there was an inverse relationship between height of the uncinate process and the size of the intervertebral foramen. Degeneration of the vertebral body (VB) did not correlate with whether the uncinate process effaced the intervertebral foramen. The taller uncinate processes tended to be located below C-3 vertebral levels, and their average anteroposterior length was 8 mm. The average thickness was found to be 4.9 mm for the base and 1.8 mm for the apex. There were no significant differences found between vertebral level and thickness of the uncinate process. Arthritic changes of the cervical VBs did not necessarily deform the uncinate processes. With axial rotation, the intervertebral discs were noted to be driven into the ipsilateral uncinate process. With lateral flexion, the ipsilateral uncinate processes aided the ipsilateral facet joints in maintaining the integrity of the ipsilateral intervertebral foramen.
Conclusions. A good appreciation for the anatomy of the uncinate processes is important to the neurosurgeon who operates on the spine. It is hoped that the data presented herein will decrease complications during surgical approaches to the cervical spine.
Neurosurgery 70:824–834, 2012 DOI: 10.1227/NEU.0b013e318236760d
Lesions in the insula and basal ganglia can be risky to resect because of their depth and proximity to critical structures, particularly in the dominant hemi- sphere. Transsylvian approaches shorten the surgical distance to these lesions, preserve perisylvian temporal and frontal cortex, and minimize brain transgression. OBJECTIVE: To report our experience with transsylvian-transinsular approaches to vascular lesions.
METHODS: The anterior approach opened the sphenoidal and insular portions of the sylvian fissure and exposed the limen insulae and short gyri, whereas the posterior approach opened the insular and opercular portions of the sylvian fissure and exposed the circular sulcus and long gyri.
RESULTS: Forty-one patients with vascular lesions (24 arteriovenous malformations [AVMs] and 17 cavernous malformations) were treated surgically with a transsylvian- transinsular approach. Complete resection was obtained in 87.5% of AVMs and 95% of cavernous malformations. Permanent neurological morbidity related to surgery was observed in 2 AVM patients (5%), with the remaining 39 patients (95%) improved or unchanged postoperatively (modified Rankin Scale scores 0-2 in 83%). There were no new language deficits in patients with dominant hemisphere lesions.
CONCLUSION: Transsylvian-transinsular approaches safely expose vascular pathology in or deep to the insula while preserving overlying eloquent cortex in the frontal and temporal lobes. The anterior transsylvian-transinsular approach can be differentiated from the posterior approach based on technical differences in splitting the sylvian fis- sure and anatomic differences in final exposure. Discriminating patient selection and careful microsurgical technique are essential.
Neurosurg Rev (2012) 35:147–154. DOI 10.1007/s10143-011-0360-3
The cavernous sinus (CS) has one of the most complex anatomical networks of the skull base and because of the diversity of its contents is involved in many pathological processes. Nevertheless, anatomical literature concerning the CS is still controversial, so a systematic literature review was performed to find out the microanatomy of the medial wall of the CS and its clinical importance on sellar pathologies.
Experimental studies from English-language literature between 1996 and 2010 were identified in MEDLINE, LILACS, and Cochrane databases. After analysis, two tables were prepared exhibiting the major points of each article. Fourteen experimental studies were included in the tables.
Four studies concluded that the medial wall of the CS is composed of a loose, fibrous structure, and the remaining ten presumed that the medial wall is formed by a dural layer that constitutes the lateral wall of the sella. The lack of definition standards and of methodological criteria led to variation in the results among different studies.
Thus, this hindered results comparison, possibly explaining the different observations.
J Neurosurg Spine 15:610–619, 2011. DOI: 10.3171/2011.7.SPINE1132
Iatrogenic injury of the V2 segment of the vertebral artery (VA) is a rare but serious complication and can be catastrophic. The purpose of this study was to characterize the relationship of the V2 segment of the VA to the surrounding anatomical structures and to highlight the potential site and mechanisms of injury that can occur during common neurosurgical procedures involving the subaxial cervical spine.
Methods. Ten adult cadaveric specimens (20 sides) were included in this study. Quantitative anatomical measurements between selected landmarks and the VA were obtained. In addition, lateral mass screws were placed bilaterally, from C-3 to C-7, reproducing either the Magerl technique or a modified technique. The safety angle, defined as the axial deviation from the screw trajectory needed to injure the VA, and the distance from the entry point to the VA were measured at each level for both techniques.
Results. The VA coursed closer to the midline at C3–4 and C4–5 (mean distance [SD] 14.9 ± 1.1 mm) than at C2–3 or C5–6. Within the intertransverse space it coursed closer to the uncinate processes of the vertebral bodies (1.8 ± 1.1 mm) than to the anterior tubercle of the transverse processes (3.4 ± 1.6 mm). The distance between the VA and the uncinate process was less at C3–6 (1.3 ± 0.7 mm) than at C2–3 (3.3 ± 0.8 mm). The VA coursed on average at a distance of 11.9 ± 1.7 mm from the anterior and 4.2 ± 2.6 mm from the posterior aspect of the intervertebral disc space. Lateral mass screw angles were 25° lateral and 39.1° cranial for the Magerl technique, and 36.6° lateral and 46.1° cranial for the modified technique. The safety angle was greater and screw length longer when using this modified technique.
Conclusions. The relation of the V2 segment of the VA to anterior procedures and lateral mass instrumentation at the subaxial cervical spine was reviewed in this study. A detailed anatomical knowledge of the V2 segment of the VA combined with careful preoperative imaging is mandatory for safe cervical spine surgery.
