Inferior temporal sulcus as a site of corticotomy: magnetic resonance imaging analysis of individual sulcus patterns

Cortical incisions and transcortical approaches for intra-axial and intraventricular lesions: A scoping review

Background

Transcortical approaches, encompassing various surgical corridors, have been employed to treat an array of intraparenchymal or intraventricular brain pathologies, including tumors, vascular malformations, infections, intracerebral hematomas, and epileptic surgery. Designing cortical incisions relies on the lesion location and characteristics, knowledge of eloquent functional anatomy, and advanced imaging such as tractography. Despite their widespread use in neurosurgery, there is a noticeable lack of systematic studies examining their common lobe access points, associated complications, and prevalent pathologies. This scoping review assesses current evidence to guide the selection of transcortical approaches for treating a variety of intracranial pathologies.

Methods

A scoping review was conducted using the PRISMA-ScR guidelines, searching PubMed, EMBASE, Scopus, and Web of Science. Studies were included if ≥5 patients operated on using transcortical approaches, with reported data on clinical features, treatments, and outcomes. Data analysis and synthesis were performed.

Results

A total of 50 articles encompassing 2604 patients were included in the study. The most common primary pathology was brain tumors (60.6%), particularly gliomas (87.4%). The transcortical-transtemporal approach was the most frequently identified cortical approach (70.48%), and the temporal lobe was the most accessed brain lobe (55.68%). The postoperative course outcomes were reported as good (55.52%), poor (28.38%), and death (14.62%).

Conclusion

Transcortical approaches are crucial techniques for managing a wide range of intracranial lesions, with the transcortical-transtemporal approach being the most common. According to the current literature, the selective choice of cortical incision and surgical corridor based on the lesion's pathology and anatomic-functional location correlates with acceptable functional outcomes.

Microsurgical and Tractographic Anatomical Study of Transtemporal-Transchoroidal Fissure Approaches to the Ambient Cistern

BACKGROUND

Approaching ambient cistern lesions is still a challenge because of deep location and related white matter tracts (WMTs) and neural structures.

OBJECTIVE

To investigate the white matter anatomy in the course of 3 types of transtemporal-transchoroidal fissure approaches (TTcFA) to ambient cistern by using fiber dissection technique with translumination and magnetic resonance imaging fiber tractography.

METHODS

Eight formalin-fixed cerebral hemispheres were dissected on surgical corridor from the temporal cortex to the ambient cistern by using Klingler's method. The trans-middle temporal gyrus, trans-inferior temporal sulcus (TITS), and trans-inferior temporal gyrus (TITG) approaches were evaluated. WMTs that were identified during dissection were then reconstructed on the Human Connectome Project 1021 individual template for validation.

RESULTS

The trans-middle gyrus approach interrupted the U fibers, arcuate fasciculus (AF), the ventral segment of inferior frontoocipital fasciculus (IFOF), the temporal extensions of the anterior commissure (AC) posterior crura, the tapetum (Tp) fibers, and the anterior loop of the optic radiation (OR). The TITS approach interrupted U fibers, inferior longitudinal fasciculus (ILF), IFOF, and OR. The TITG approach interrupted the U fibers, ILF, and OR. The middle longitudinal fasciculus, ILF, and uncinate fasciculus (UF) were not interrupted in the trans-middle gyrus approach and the AF, UF, AC, and Tp fibers were not interrupted in the TITS/gyrus approaches.

CONCLUSION

Surgical planning of the ambient cistern lesions requires detailed knowledge about WMTs. Fiber dissection and tractography techniques improve the orientation during surgery and may help decrease surgical complications.

Mapping the superficial morphology of the occipital lobe: proposal of a universal nomenclature for clinical and anatomical use

The superficial anatomy of the occipital lobe has been described as irregular and highly complex. This notion mainly arises from the variability of the regional sulco-gyral architecture. Our aim was to investigate the prevalence, morphology, and correlative anatomy of the sulci and gyri of the occipital region in cadaveric specimens and to summarize the nomenclature used in the literature to describe these structures. To this end, 33 normal, adult, formalin-fixed hemispheres were studied. In addition, a review of the relevant literature was conducted with the aim to compare our findings with data from previous studies. Hence, in the lateral occipital surface, we recorded the lateral occipital sulcus and the intraoccipital sulcus in 100%, the anterior occipital sulcus in 24%, and the inferior occipital sulcus in 15% of cases. In the area of the occipital pole, we found the transverse occipital sulcus in 88% of cases, the lunate sulcus in 64%, the occipitopolar sulcus in 24%, and the retrocalcarine sulcus in 12% of specimens. In the medial occipital surface, the calcarine fissure and parieto-occipital sulcus were always present. Finally, the basal occipital surface was always indented by the posterior occipitotemporal and posterior collateral sulci. A sulcus not previously described in the literature was identified on the supero-lateral aspect of the occipital surface in 85% of cases. We named this sulcus "marginal occipital sulcus" after its specific topography. In this study, we offer a clear description of the occipital surface anatomy and further propose a standardized taxonomy for clinical and anatomical use.

Navigation-assisted trans-inferotemporal cortex selective amygdalohippocampectomy for mesial temporal lobe epilepsy; preserving the temporal stem

OBJECTIVE

Selective amygdalohippocampectomy (SAH) can be used to obtain satisfactory seizure control in patients with mesial temporal lobe epilepsy (MTLE). Several SAH procedures have been reported to achieve satisfactory outcomes for seizure control, but none yield fully satisfactory outcomes for memory function. We hypothesized that preserving the temporal stem might play an important role. To preserve the temporal stem, we developed a minimally invasive surgical procedure, 'neuronavigation-assisted trans-inferotemporal cortex SAH' (TITC-SAH).

METHODS

TITC-SAH was performed in 23 patients with MTLE (MTLE on the language-non-dominant hemisphere, n = 11). The inferior horn of the lateral ventricle was approached via the inferior or middle temporal gyrus along the inferior temporal sulcus under neuronavigation guidance. The hippocampus was dissected in a subpial manner and resected en bloc together with the parahippocampal gyrus. Seizure control at one year and memory function at 6 months postoperatively were evaluated.

RESULTS

One year after TITC-SAH, 20 of the 23 patients were seizure-free (ILAE class 1), 2 were class 2, and 1 was class 3. Verbal memory improved significantly in 13 patients with a diagnosis of hippocampal sclerosis, for whom WMS-R scores were available both pre- and post-operatively. Improvements were seen regardless of whether the SAH was on the language-dominant or non-dominant hemisphere. No major complication was observed.

CONCLUSION

Navigation-assisted TITC-SAH performed for MTLE offers a simple, minimally invasive procedure that appears to yield excellent outcomes in terms of seizure control and preservation of memory function, because this procedure does not damage the temporal stem. TITC-SAH should be one of the feasible surgical procedures for MTLE.

ABBREVIATIONS

SAH: Amygdalohippocampectomy; MTLE: Mesial temporal lobe epilepsy (MTLE); TITC-SAH: Ttrans-inferotemporal cortex SAH; ILAE: International League Against Epilepsy (ILAE); MRI: Magnetic resonance imaging; EEG: Electroencephalography (EEG); FDG-PET: ⁸F-fluorodeoxyglucose (FDG)-positron emission tomography; ECoG: Electrocorticography; MEG: Magnetoencephalography; IMZ-SPECT: N-isopropyl-p(¹²³I)-iodoamphetamine single photon emission computed tomography; WMS-R: Wechsler Memory Scale-Revised.

Middle Temporal Gyrus Versus Inferior Temporal Gyrus Transcortical Approaches to High-Grade Astrocytomas in the Mediobasal Temporal Lobe: A Comparison of Outcomes, Functional Restoration, and Surgical Considerations

INTRODUCTION

High-grade astrocytomas of the mesial temporal lobe may pose surgical challenges. Several approaches (trans-sylvian, subtemporal, and transcortical) have been designed to circumnavigate the critical neurovascular structures and white fiber tracts that surround this area. Considering the paucity of literature on the transcortical approach for these lesions, we describe our institutional experience with transcortical approaches to Grade III/IV astrocytomas in the mesial temporal lobe.

METHODS

Between 1999 and 2009, 23 patients underwent surgery at the Johns Hopkins Medical Institutions for Grade III/IV astrocytomas involving the mesial temporal lobe (without involvement of the temporal neocortex). Clinical notes, operative records, and imaging were reviewed.

RESULTS

Thirteen patients had tumors in the dominant hemisphere. All patients underwent surgery via a transcortical approach (14 via the inferior temporal gyrus and 9 via the middle temporal gyrus). Gross total resection was obtained in 92 % of the cohort. Neurological outcomes were: clinically significant stroke (2 patients), new visual deficits (2 patients), new speech deficit (1 patient); seizure control (53 %).

CONCLUSIONS

In comparison to reported results in the literature for the transylvian and subtemporal approaches, the transcortical approach may provide the access necessary for a gross total resection with minimal neurological consequences. In our series of patients, there was no statistically significant difference in outcomes between the middle temporal gyrus versus the inferior temporal gyrus trajectories.

Surgical Approaches to the Temporal Horn: An Anatomic Analysis of White Matter Tract Interruption

BACKGROUND: Surgical access to the temporal horn is necessary to treat tumors and vascular lesions, but is used mainly in patients with mediobasal temporal epilepsy. The surgical approaches to this cavity fall into 3 primary categories: lateral, inferior, and transsylvian. The current neurosurgical literature has underestimated the interruption of involved fiber bundles and the correlated clinical manifestations.

OBJECTIVE: To delineate the interruption of fiber bundles during the different approaches to the temporal horn.

METHODS: We simulated the lateral (trans-middle temporal gyrus), inferior (transparahippocampal gyrus), and transsylvian approaches in 20 previously frozen, formalin-fixed human brains (40 hemispheres). Fiber dissection was then done along the lateral and inferior aspects under the operating microscope. Each stage of dissection and its respective fiber tract interruption were defined.

RESULTS: The lateral (trans-middle temporal gyrus) approach interrupted “U” fibers, the superior longitudinal fasciculus (inferior arm), occipitofrontal fasciculus (ventral segment), uncinate fasciculus (dorsolateral segment), anterior commissure (posterior segment), temporopontine, inferior thalamic peduncle (posterior fibers), posterior thalamic peduncle (anterior portion), and tapetum fibers. The inferior (transparahippocampal gyrus) approach interrupted “U” fibers, the cingulum (inferior arm), and fimbria, and transected the hippocampal formation. The transsylvian approach interrupted “U” fibers (anterobasal region of the extreme capsule), the uncinate fasciculus (ventromedial segment), and anterior commissure (anterior segment), and transected the anterosuperior aspect of the amygdala.

CONCLUSION: White matter dissection improves our knowledge of the complex anatomy surrounding the temporal horn. Identifying the fiber bundles at risk during each surgical approach adds important information for choosing the appropriate surgical strategy.

Modified trans-middle temporal gyrus approach for trigonal tumor to preserve visual field

OBJECTIVE

We evaluated a modified trans-middle temporal gyrus (MTG) approach with good postoperative visual preservation for patients with trigonal tumors.

METHODS

Three patients with a trigonal tumor were treated via the modified trans-MTG approach guided by a neuro-navigator. Modified trans-MTG approach involve the incision at the MTG within 5 mm to the superior temporal sulcus. This approach makes a proper trajectory to the trigone but also reduces the retraction injury of MTG as little as possible to prevent postoperative visual field defect. Preoperative and postoperative visual field examination using perimetry was performed to evaluate the visual field.

RESULTS

Three patients underwent surgery for lymphoma in the right trigone, meningioma in the left trigone, and focal enhancing nodule in the right paratrigonal area, respectively. In case of lymphoma, preoperative examination showed a left homonymous hemianopsia : one week later after surgery, a visual field examination was performed and revealed improvement of the visual field defect. In case of the meningioma, the preoperative examination showed no visual field defect : one month later, the visual field had no defect. In case of the enhancing nodule, preoperative visual field testing revealed a partial left homonymous hemianopsia. Visual examination within one month after surgery showed no visual field defect. All three patients treated with the modified trans-MTG approach showed no visual deterioration after surgery.

CONCLUSION

The modified trans-MTG approach provides a safe and useful technique for trigonal tumors without postoperative visual field deterioration and affords adequate exposure of the trigonal tumor with a short trajectory.

Through the choroidal fissure: a quantitative anatomic comparison of 2 incisions and trajectories (transsylvian transchoroidal and lateral transtemporal)

BACKGROUND

We compared the transsylvian transchoroidal (TSTC) approach with the lateral transtemporal (LTT) approach. Both approaches proceed through the choroidal fissure but through different incisions and along different trajectories.

METHODS

Four fixed, silicon-injected heads (8 sides) were used. Nine strategic anatomic points within the dissections were compared between the TSTC and LTT approaches in 7 other silicon-injected heads (14 sides). Neuronavigation was used to gather coordinates from selected points of both approaches to calculate surgical angles and distances to common targets.

RESULTS

The surgical angle of the TSTC approach for the inferior choroidal point was wider compared with the LTT approach (P < .05). The surgical angles for the P2a-P2p point were similar for both approaches. In the TSTC approach, the P2-P3 point angle was smaller than in the LTT approach (P < .05). The TSTC approach provided (except for the P2-P3 point) significantly shorter distances to all defined anatomic targets compared with the LTT approach. When the posterior cerebral artery was the target in the TSTC approach, the hippocampus was retracted 3 to 8 mm compared with 8 to 13 mm in the LTT approach.

CONCLUSION

We quantitatively described anatomic features of the TSTC approach and compared them with the LTT approach. For approaching the mesial temporal region, the TSTC approach offers an adequate surgical angle and shorter or similar distances proximal to P2-P3 and requires less temporal lobe and hippocampal retraction than the LTT approach. Such information can help surgeons select the optimal approach to the mesial temporal lobe and its surrounding structures. The TSTC approach should be considered for lesions located in the medial temporal region.

Anterior Selective Amygdalohippocampectomy: Technical Description and Microsurgical Anatomy

Objective:

We introduce a technique for performing a selective amygdalohippocampectomy (AH) through a minisupraorbital approach.

Methods:

A minisupraorbital craniotomy and an anterior selective AH were performed in 8 cadaver heads (16 sides). The anatomic specimens were analyzed, and the extent of resection of the hippocampus and amygdala was evaluated. Surgically relevant measurements were performed using anatomic specimens. An image-guided system was used to document the extent of the anterior AH. Laboratory data were used to support the clinical application of the technique.

Results:

The anterior route allowed removal of the amygdala and hippocampus, as confirmed by anatomic assessment. The image-guided system and anatomic evaluation confirmed that the amygdala and hippocampus can be accessed and removed through this route. The mean distance between the anterior aspect of the uncus and the tip of the temporal horn was 17.0 ± 4.6 mm; the mean distance from the head of the hippocampus to the posterior border of the cerebral peduncles was 26.0 ± 3.2 mm. Clinical application resulted in satisfactory removal of the amygdala and hippocampus.

Conclusion:

The anterior route for selective AH is a logical and straightforward approach to the mesial temporal lobe. Compared with other variations, it is less invasive and destructive, especially in terms of the fibers of the optic pathway, temporal stem, and lateral temporal neocortex.

Memory outcome following transsylvian selective amygdalohippocampectomy in 62 patients with hippocampal sclerosis

OBJECT

It remains unclear whether selective amygdalohippocampectomy, an operative technique developed for use in epilepsy surgery to spare unaffected brain tissue and thus minimize the cognitive consequences of temporal lobe surgery, actually leads to a better memory outcome. The present study was performed to determine the effects of selective surgery on memory outcome in patients with intractable mesial temporal lobe epilepsy due to hippocampal sclerosis treated using transsylvian selective amygdalohippocampectomy (TSA).

METHODS

The study population consisted of 62 patients with left hemisphere language dominance who underwent left-(31 patients) or right-sided (31 patients) TSA. All patients underwent comprehensive neuropsychological testing before and 1 month and 1 year after unilateral TSA. Verbal Memory I, Nonverbal Memory I, Total Memory, Attention, and Delayed Recall were assessed using the Wechsler Memory Scale-Revised, whereas Verbal Memory II was assessed using the Miyake Verbal Retention Test (MVRT), and Nonverbal Memory II was assessed using the Benton Visual Retention Test. Separate repeated-measures multivariate analysis of variance (MANOVA) were performed for these intervals with memory scores.

RESULTS

The results of MANOVA indicated that patients who underwent right-sided TSA showed significant improvements in Verbal Memory I (preoperatively vs 1 month postoperatively, p < 0.0001; and preoperatively vs 1 year postoperatively, p = 0.0002), Nonverbal Memory I (preoperatively vs 1 month postoperatively, p = 0.0003; and preoperatively vs 1 year postoperatively, p = 0.006), and Delayed Recall (preoperatively vs 1 month postoperatively, p = 0.028) at both 1-month and 1-year follow-ups. In addition, Verbal Memory II (MVRT) was also significantly improved 1 year after surgery (p = 0.001). In the group of patients who underwent left-sided TSA, both Verbal Memory I and II were maintained at the same level 1 month after surgery, whereas the Verbal Memory I score 1 year after surgery increased with marginal significance (p = 0.074). In addition, Verbal Memory II showed significant improvement 1 year after surgery (p = 0.049). There were no significant changes in Nonverbal Memory I and II, Attention, or Delayed Recall at either the 1-month or 1-year follow-up.

CONCLUSIONS

Results of the present study indicated that left-sided TSA for hippocampal sclerosis tends to improve verbal memory function with the preservation of other types of memory function. Moreover, right-sided TSA for hippocampal sclerosis can lead to significant improvement in memory function, with memory improvement observed 1 month after right-sided TSA and persisting 1 year after surgery.

[Corticectomy: technical considerations]

The surgical treatment of epilepsy requires careful preparation and presents a certain number of technical specificities. The neurosurgeon must master not only the technical aspects but also the therapeutic and functional trade-off in order to modulate the procedure according to morphological and electrophysiological intraoperative data. A large number of technical variants have been developed to correspond to epileptological or functional anatomical considerations. Until this point, the choice of a particular technique does not seem to have a significant impact on the therapeutic effectiveness of surgery, and differences in results can be related to the presurgical evaluation and surgical indications. On the other hand, technical development promises to play an important role in limiting the long-term neurocognitive consequences of surgery.

Imaging the mind, minding the image: an historical introduction to brain imaging and the law

Since ancient times, people have yearned to attribute human behaviors to a physical source within the head. Recently, neuroimaging technologies have given us the technical ability to look at the living brain, its structures, and some of its functions without the need for invasive procedures. However, the science has a long way to go before these technologies can allow us fully to appreciate the anatomical and physiologic underpinnings of human thoughts, states of mind, motives, will, or behaviors.

In this Article, we use an historical overview to introduce the various new technologies for imaging the brain. Today, the goal of medical science is the same as it has always been: to make medical technologies valid, useful, effective, and safe; and to guide appropriate uses while protecting the public from the misuse of them. Brain images are particularly vulnerable to misuse because they are so visually attractive. This visual power can easily result in misunderstanding about what the images show and what they mean.

An anteromedial approach to the temporal horn to avoid injury to the optic radiation fibers and uncinate fasciculus: anatomical and technical note

Object

The aim of this study was to define an anteromedial approach to the temporal horn via a transsylvian approach to avoid injury to the optic radiation fibers as well as the uncinate fasciculus. This route was compared with standard surgical approaches to the temporal horn, and their relationship to the optic radiation and uncinate fasciculus was reviewed.

Methods

Three cadaveric brain specimens were prepared with freezing and thawing cycles according to the Klingler technique. Dissection was performed in a lateral-to-medial fashion with the help of wooden spatulas. Photographs were taken through the operating microscope at every level of the dissection. The dissection was continued until the optic radiation was encountered. Particular attention was paid to the relationship of the uncinate fasciculus with the optic radiation. An anteromedial transsylvian approach was defined to enter the temporal horn without injuring the optic radiation or the uncinate fasciculus.

Conclusions

A transsylvian anteromedial approach through the pyriform cortex at the level of the anterior and superior surface of the uncus enables a safe entry into the temporal horn without injury to the optic radiation fibers or the main part of the uncinate fasciculus.

White matter fiber dissection of the optic radiations of the temporal lobe and implications for surgical approaches to the temporal horn

Object. The aim of this anatomical study was to define more fully the three-dimensional (3D) relationships between the optic radiations and the temporal horn and superficial anatomy of the temporal lobe by using the Klingler white matter fiber dissection technique. These findings were correlated with established surgical trajectories to the temporal horn. Such surgical trajectories have implications for amygdalohippocampectomy and other procedures that involve entering the temporal horn for the resection of tumors or vascular lesions.

Methods. Ten human cadaveric hemispheres were prepared with several cycles of freezing and thawing by using a modification of the method described by Klingler. Wooden spatulas were used to strip away the deeper layers of white matter progressively in a lateromedial direction, and various association, projection, and commissural fibers were demonstrated. As the dissection progressed, photographs of each progressive layer were obtained. Special attention was given to the optic radiation and to the sagittal stratum of which the optic radiation is a part. The trajectories of fibers in the optic radiation were specifically studied in relation to the lateral, medial, superior, and inferior walls of the temporal horn as well as to the superficial anatomy of the temporal lobe. In three of the hemispheres coronal sections were made so that the relationship between the optic radiation and the temporal horn could be studied more fully.

In all 10 hemispheres that were dissected the following observations were made. 1) The optic radiation covered the entire lateral aspect of the temporal horn as it extends to the occipital horn. 2) The anterior tip of the temporal horn was covered by the anterior optic radiation along its lateral half. 3) The entire medial wall of the temporal horn was free from optic radiation fibers, except at the level at which these fibers arise from the lateral geniculate body to ascend over the roof of the temporal horn. 4) The superior wall of the temporal horn was covered by optic radiation fibers. 5) The entire inferior wall of the temporal horn was free from optic radiation fibers anterior to the level of the lateral geniculate body.

Conclusions. Fiber dissections of the temporal lobe and horn demonstrated the complex 3D relationships between the optic radiations and the temporal horn and superficial anatomy of the temporal lobe. Based on the results of this study, the authors define two anatomical surgical trajectories to the temporal horn that would avoid the optic radiations. The first of these involves a transsylvian anterior medial approach and the second a pure inferior trajectory through a fusiform gyrus. Lateral approaches to the temporal horn through the superior and middle gyri, based on the authors' findings, would traverse the optic radiations.

Sulcal pattern and morphology of the superior temporal sulcus

The superior temporal sulcus (STs) is the main sulcal landmark of the external temporal cortex and is very important for functional (posterior language areas on the left) mapping and surgery. The methodology we use is based on the extraction of the 3D shape of sulci and their separation into subunits called sulcal roots. Seventeen normal brains (male: 11, female: 6, age: 22-60) were systematically analyzed. Additionally, parameters generated by visual observation were recorded. Non-parametric statistics were performed to evaluate the variation of the STs and influence of side, handedness and sex. We found that the 3D architecture of the STs was consistent with our generic model in four sulcal roots and four "plis de passage" (PP) and significant differences between right and left hemispheres. These morphological differences may be related to the language-relevant cortical areas difference and are pertinent for defining the limits of morphometric variability of the STs in "normal humans".

Inferior Temporal Sulcus Approach for Amygdalohippocampectomy Guided by a Laser Beam of Stereotactic Navigator

OBJECTIVE

To describe a surgical technique for a minimally invasive transcortical transventricular amygdalohippocampectomy via the inferior temporal sulcus (ITS) using a stereotactic navigator.

METHODS

Seven patients with medically intractable mesial temporal lobe epilepsy underwent an amygdalohippocampectomy via the ITS. By use of a laser-guided navigation system, the epileptogenic foci of the mesial temporal lobe were resected through a small linear operative route that was made by a brain speculum inserted from the ITS to the anterolateral floor of the temporal horn in the lateral ventricle.

RESULTS

All patients completed at least a 1-year follow-up (range, 14–45 mo) after surgery and had improved neuropsychological parameters as a result of the operation. All patients became seizure-free after surgery. A Humphrey visual field perimeter detected no hemianopsia.

CONCLUSION

Combined with the stereotactic navigation system, the ITS approach provides the least invasive amygdalohippocampectomy that preserves optic radiation. This approach seems beneficial especially in patients in whom the epileptic lesions are limited to the anterior mesial temporal lobe.