Parcellating the vertical associative fiber network of the temporoparietal area: Evidence from focused anatomic fiber dissections.

Introduction: The connectivity of the temporoparietal (TP) region has been the subject of multiple anatomical and functional studies. Its role in high cognitive functions has been primarily correlated with long association fiber connections. As a major sensory integration hub, coactivation of areas within the TP requires a stream of short association fibers running between its subregions. The latter have been the subject of a small number of recent in vivo and cadaveric studies. This has resulted in limited understanding of this network and, in certain occasions, terminology ambiguity. Research question: To systematically study the vertical parietal and temporoparietal short association fibers. Material and methods: Thirteen normal, adult cadaveric hemispheres, were treated with the Klinger's freeze-thaw process and their subcortical anatomy was studied using the microdissection technique. Results: Two separate fiber layers were identified. Superficially, directly beneath the cortical u-fibers, the Stratum proprium intraparietalis (SP) was seen connecting Superior Parietal lobule and Precuneal cortical areas to inferior cortical regions of the Parietal lobe, running deep to the Intraparietal sulcus. At the same dissection level, the IPL-TP fibers were identified as a bundle connecting the Inferior Parietal lobule with posterior Temporal cortical areas. At a deeper level, parallel to the Arcuate fasciculus fibers, the SPL-TP fibers were seen connecting the Superior Parietal lobule to posterior Temporal cortical areas. Discussion and conclusion: To our knowledge this is the first cadaveric dissection study to comprehensively study and describe of the vertical association fibers of the temporoparietal region while proposing a universal terminology.

Preoperative neurocognitive function as an independent survival prognostic marker in primary glioblastoma.

Background: Aim of the present study is to investigate whether preoperative neurocognitive status is prognostically associated with overall survival (OS) in newly diagnosed glioblastoma (GBM) patients. Methods: Ninety patients with dominant-hemisphere IDH-wild-type GBM were assessed by Mini Mental Status Exam (MMSE), Trail Making Test (TMT) A and B parts, and Control Word Association Test (COWAT) phonemic and semantic subtests. Demographics, Karnofsky Performance Scale, tumor parameters, type of surgery, and adjuvant therapy data were available for patients. Results: According to Cox proportional hazards model the neurocognitive variables of TMT B (P < .01), COWAT semantic subset (P < .05), and the MMSE (P < .01) were found significantly associated with survival prediction. From all other factors, only tumor volume and operation type (debulking vs biopsy) showed a statistical association (P < .05) with survival prediction. Kaplan Meier Long rank test showed statistical significance (P < .01) between unimpaired and impaired groups for TMT B, with median survival for the unimpaired group 26 months and 10 months for the impaired group, for COWAT semantic (P < .01) with median survival 23 months and 12 months, respectively and for MMSE (P < .01) with medial survival 19 and 12 months respectively. Conclusions: Our study demonstrates that neurocognitive status at baseline-prior to treatment-is an independent prognostic factor for OS in wild-type GBM patients, adding another prognostic tool to assist physicians in selecting the best treatment plan.

An Applied Anatomic Guide to Anterior Temporal Lobectomy and Amygdalohippocampectomy: Laboratory Cranial and White Matter Dissections to Inform Surgical Practice.

BACKGROUND AND OBJECTIVES: Anterior temporal lobectomy and amygdalohippocampectomy is a challenging procedure because of the deep surgical trajectory and complex regional neurovascular anatomy. A thorough knowledge of the involved anatomic structures is crucial for a safe and effective procedure. Our objective is to explore the white matter pathways in or around the operative corridor and to illuminate the 3-dimensional relationships of the pertinent operative parenchymal and skull base anatomy, aiming to inform and simplify surgical practice. METHODS: Four normal, adult, cadaveric, formalin-fixed cerebral hemispheres (2 left and 2 right) treated with the Klinger's technique and 2 formalin-fixed and colored-latex-injected cadaveric heads (4 sides) were used. Focused white matter and cadaveric dissections were used to study the relevant anatomy implicated during an anterior temporal lobectomy. Four illustrative cases were also included. Digital photographs from every dissection step were obtained. RESULTS: Major white matter pathways that are inevitably traversed during the approach are the inferior longitudinal fasciculus, uncinate fasciculus, and inferior arm of the cingulum. Tracts that can be potentially injured, should the dissection plane tilt inadvertently superiorly or posteriorly, are the inferior fronto-occipital fasciculus, Meyer's loop, superior longitudinal fasciculus/arcuate fasciculus complex, and basal ganglia. Consistent cranial and parenchymal landmarks that can act as a roadmap during the procedure are recorded and paired with their intraoperative equivalent to provide a thorough, yet simple, stepwise guide for the surgeon. CONCLUSION: White matter dissections, cadaveric cranial dissections, and intraoperative images are put together to provide a simplified stepwise surgical manual for anterior temporal lobectomy. Laboratory investigations that focus on the intricate 3-dimensional relationships of the pertinent operative anatomy from the surgeon's eye may enrich anatomic knowledge and push surgical boundaries, to minimize complication rates and ultimately improve patient outcomes.

Association between preoperative neurocognitive status and IDH1 mutation status in high-grade gliomas.

Background: High-grade glioma (HGG) patients present with variable impairment in neurocognitive function (NCF). Based on that, isocitrate dehydrogenase 1 (IDH1) wild-type HGGs are more aggressive than IDH1 mutant-type ones, we hypothesized that patients with IDH1 wild-type HGG would exhibit more severe NCF deficits than their IDH1 mutant counterparts. Methods: NCF was assessed by Mini Mental Status Exam (MMSE), Trail Making Test (TMT), Digit Span (DS), and Controlled Word Association Test (COWAT) tests in 147 HGG patients preoperatively. Results: Analyses between IDH1 groups revealed a significant difference on MMSE concentration component (p ≤ .01), DS (p ≤ .01), TMTB (p ≤ .01), and COWAT (p ≤ .01) scores, with the IDH1 wild group performing worse than the IDH1 mutant one. Age and tumor volume were inversely correlated with MMSE concentration component (r = -4.78, p < .01), and with MMSE concentration (r = -.401, p < .01), TMTB (r = -.328, p < .01), and COWAT phonemic scores (r = -.599, p < .01), respectively, but only for the IDH1 wild-type group. Analyses between age-matched subsamples of IDH1 groups revealed no age effect on NCF. Tumor grade showed nonsignificance on NCF (p > .05) between the 2 IDH1 mutation subgroups of grade IV tumor patients. On the contrary, grade III group showed a significant difference in TMTB (p < .01) and DS backwards (p < .01) between IDH1 subgroups, with the mutant one outperforming the IDH1 wild one. Conclusions: Our findings indicate that IDH1 wild-type HGG patients present greater NCF impairment, in executive functions particularly, compared to IDH1 mutant ones, suggesting that tumor growth kinetics may play a more profound role than other tumor and demographic parameters in clinical NCF of HGG patients.

Direct Comparison Between the Kawase Approach and Retrosigmoid Intradural Suprameatal Corridor to Access the Petroclival Region Using Computed Tomography Quantitative Volumetric Analysis: A Cadaveric Study.

OBJECTIVE: The anterior petrosectomy, also known as the Kawase approach, and the retrosigmoid intradural suprameatal approach (RISA) have both been used to reduce the petrous apex and access the petroclival region. Our goal was to compare the volumes and 3-dimensional shapes of bony resection obtained through each approach while trying to resemble realistic surgical settings. METHODS: Five cadaveric specimens totaling 10 sides were dissected and analyzed. In every specimen, 1 side was used for the Kawase approach while the opposite side was used for the RISA. Petrosectomy volumes were assessed by comparing preoperative and postoperative thin-sliced computed tomography scans. RESULTS: Petrosectomy volumes were significantly larger through the Kawase approach than through the RISA (0.82 ± 0.11 vs. 0.49 ± 0.07 cm3, P < 0.001). In addition, surgical maneuverability and freedom were greater in the Kawase operative variant. Lastly, the morphology of the bony window achieved through each approach was clearly different: trapezoid for the anterior petrosectomy versus elongated ellipsoid for the RISA. CONCLUSIONS: The Kawase approach invariably results in larger volumes of bony removal than the RISA operative variant, and the volume of petrosectomy that is spatially congruent is only partially identical. The Kawase corridor is best suited for middle fossa lesions that extend into the posterior fossa, while the RISA is suitable for pathologies mainly residing in the posterior fossa and extending into the Meckel cave.

A stepwise laboratory manual for the dissection and illustration of limbic and paralimbic structures: lessons learned from the Klingler's technique.

BACKGROUND: Three-dimensional relationships within the limbic and paralimbic areas are often hard to grasp. Relevant anatomical structures exhibit a complicated architecture and connectivity and therefore surgical approaches targeting lesions or functional resections in this area pose a distinct challenge. PURPOSE: To provide an educational, comprehensive, systematic and stepwise manual for the dissection and illustration of major limbic structures since there is a gap in the pertinent literature. Further, we aim to offer a thorough yet simplified roadmap for laboratory and intraoperative dissections. METHODS: Twenty (20) normal adult, formalin-fixed cerebral hemispheres were studied through the fiber dissection technique and under the microscope. Stepwise and in tandem medial to lateral and lateral to medial dissections were performed in all specimens aiming to reveal the morphology and spatial relationships of major limbic and paralimbic areas. RESULTS: Fourteen (14) consecutive, discrete and easily reproducible laboratory anatomical steps are systematically described to reveal the intricate anatomy of the limbic and paralimbic structures and their main connections. CONCLUSION: This study offers for the first time in the pertinent literature a focused, step-by-step laboratory manual for the dissection and illustration of the limbic and paralimbic structures. The overreaching goal is to supplement the novice and experienced anatomist and neurosurgeon with a thorough and systematic reference to facilitate laboratory or intraoperative dissections.

The Topography of the Frontal Terminations of the Uncinate Fasciculus Revisited Through Focused Fiber Dissections: Shedding Light on a Current Controversy and Introducing the Insular Apex as a Key Anatomoclinical Area.

BACKGROUND: Recent studies advocate a connectivity pattern wider than previously believed of the uncinate fasciculus that extends to the ventrolateral and dorsolateral prefrontal cortices. These new percepts on the connectivity of the tract suggest a more expansive role for the uncinate fasciculus. Our aim was to shed light on this controversy through fiber dissections. METHODS: Twenty normal adult human formalin-fixed cerebral hemispheres were used. Focused dissections on the insular, orbitofrontal, ventromedial, ventrolateral, and dorsolateral prefrontal areas were performed to record the topography of the frontal terminations of the uncinate fasciculus. RESULTS: Three discrete fiber layers were consistently disclosed: the first layer was recorded to terminate at the posterior orbital gyrus and pars orbitalis, the second layer at the posterior two thirds of the gyrus rectus, and the last layer at the posterior one third of the paraolfactory gyrus. The insular apex was documented as a crucial landmark regarding the topographic differentiation of the uncinate and occipitofrontal fasciculi (i.e., fibers that travel ventrally belong to the uncinate fasciculus whereas those traveling dorsally are occipitofrontal fibers). CONCLUSIONS: The frontal terminations of the uncinate fasciculus were consistently documented to project to the posterior orbitofrontal area. The area of the insular apex is introduced for the first time as a crucial surface landmark to effectively distinguish the stems of the uncinate and occipitofrontal fasciculi. This finding could refine the spatial resolution of awake subcortical mapping, especially for insular lesions, and improve the accuracy of in vivo diffusion tensor imaging protocols.

The corticotegmental connectivity as an integral component of the descending extrapyramidal pathway: novel and direct structural evidence stemming from focused fiber dissections.

This study opts to investigate the thus far ill-defined intra-hemispheric topography, morphology, and connectivity of the extrapyramidal fibers that originate from the frontoparietal cortex and project to the tegmental area and to explore structural correlations to the pyramidal pathway. To this end, twenty normal adult, formalin-fixed cerebral hemispheres were studied through the fiber micro-dissection technique. Stepwise and in-tandem medial to lateral and lateral to medial dissections were carried out in all specimens. The cortical termination of the fibers under investigation was carefully defined, and their entry zone at the tegmental area was meticulously recorded. We consistently identified the corticotegmental tract (CTT) as a distinct fiber pathway lying in the white matter of the genu and posterior limb of the internal capsule and travelling medial to the corticospinal tract (CST) and lateral to the thalamic radiations. The CTT exhibits a fan-shaped configuration and can be classified into three discrete segments: a rostral one receiving fibers from BA8 (pre-SMA, frontal eye fields, dorsal prefrontal cortex), a middle one arising from areas BA4 and BA6 (primary motor cortex and premotor cortex), and a caudal one stemming from areas BA1/2/3 (somatosensory cortex). The anatomical location, configuration, trajectory, and axonal connectivity of this tract are attuned to the descending component of the extrapyramidal system, and therefore, it is believed to be implicated in locomotion, postural control, motor inhibition, and motor modification. Our results provide further support on the emerging concept of a dynamic, parallel, and delocalized theory for complex human motor behavior.

Deciphering the frontostriatal circuitry through the fiber dissection technique: direct structural evidence on the morphology and axonal connectivity of the fronto-caudate tract.

OBJECTIVE: The authors sought to investigate the very existence and map the topography, morphology, and axonal connectivity of a thus far ill-defined subcortical pathway known as the fronto-caudate tract (FCT) since there is a paucity of direct structural evidence regarding this pathway in the relevant literature. METHODS: Twenty normal adult cadaveric formalin-fixed cerebral hemispheres (10 left and 10 right) were explored through the fiber microdissection technique. Lateral to medial and medial to lateral dissections were carried out in a tandem manner in all hemispheres. Attention was focused on the prefrontal area and central core since previous diffusion tensor imaging studies have recorded the tract to reside in this territory. RESULTS: In all cases, the authors readily identified the FCT as a fan-shaped pathway lying in the most medial layer of the corona radiata and traveling across the subependymal plane before terminating on the superolateral margin of the head and anterior part of the body of the caudate nucleus. The FCT could be adequately differentiated from adjacent fiber tracts and was consistently recorded to terminate in Brodmann areas 8, 9, 10, and 11 (anterior pre-supplementary motor area and the dorsolateral, frontopolar, and fronto-orbital prefrontal cortices). The authors were also able to divide the tract into a ventral and a dorsal segment according to the respective topography and connectivity observed. Hemispheric asymmetries were not observed, but instead the authors disclosed asymmetry within the FCT, with the ventral segment always being thicker and bulkier than the dorsal one. CONCLUSIONS: By using the fiber microdissection technique, the authors provide sound structural evidence on the topography, morphology, and connectional anatomy of the FCT as a distinct part of a wider frontostriatal circuitry. The findings are in line with the tract's putative functional implications in high-order motor and behavioral processes and can potentially inform current surgical practice in the fields of neuro-oncology and functional neurosurgery.

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.

Recent trends (2010-2018) in traumatic brain injury in Greece: Results on 2042 patients.

BACKGROUND: Recent analysis on the epidemiology of traumatic brain injury (TBI) within Europe indicates an increase in fall-related injuries and in the incidence of hospitalization among older adults as well as a decrease in contribution of road traffic accidents (RTA). Given the paucity of recent national data, we analyzed TBI-related admissions from the Athens Head Trauma Registry during the largest part of the past decade (2010-2018), a period marked by a profound national socioeconomic crisis. METHODS: Demographic and clinical data of admitted TBI patients were collected and analyzed statistically. RESULTS: The mean age of patients (N=2042, 68% men) was 59 years (median 64 years). Patient age showed an upward trend across the study period. Most cases were mild, while moderate and severe injuries were indicated in, 11% and 20%, respectively. Falls were the predominant cause of injury (46% of cases), followed by RTA (38%). An upward trend in the frequency of fall-related injury was apparent across the study period; RTA-related injury frequency displayed a downward trend during the second part of the study period. Assault-related injury accounted for 6%. Surgery took place in 11% of cases. In-hospital mortality (IHM) was 21%. Fall-related mortality contributed to 56% of total IHM; RTA-related mortality contributed to 30%. The mean length of hospital stay was 13 days (median: 5 days). CONCLUSIONS: The present findings suggest a shift in the epidemiologic profile of TBI patients in Greece with a rise in the proportion of elderly patients, a concomitant increase in fall-related injuries and a reduction in RTA-related injury. They also highlight fall-related injury as the predominant cause of IHM. Our results point towards the urgent need for the intensification of fall prevention strategies, continuing medical education as well as public information campaigns on the risks of geriatric fall-related injury.

The frontal longitudinal system as revealed through the fiber microdissection technique: structural evidence underpinning the direct connectivity of the prefrontal-premotor circuitry.

OBJECTIVE: The purpose of this study was to investigate the morphology, connectivity, and correlative anatomy of the longitudinal group of fibers residing in the frontal area, which resemble the anterior extension of the superior longitudinal fasciculus (SLF) and were previously described as the frontal longitudinal system (FLS). METHODS: Fifteen normal adult formalin-fixed cerebral hemispheres collected from cadavers were studied using the Klingler microdissection technique. Lateral to medial dissections were performed in a stepwise fashion starting from the frontal area and extending to the temporoparietal regions. RESULTS: The FLS was consistently identified as a fiber pathway residing just under the superficial U-fibers of the middle frontal gyrus or middle frontal sulcus (when present) and extending as far as the frontal pole. The authors were able to record two different configurations: one consisting of two distinct, parallel, longitudinal fiber chains (13% of cases), and the other consisting of a single stem of fibers (87% of cases). The fiber chains' cortical terminations in the frontal and prefrontal area were also traced. More specifically, the FLS was always recorded to terminate in Brodmann areas 6, 46, 45, and 10 (premotor cortex, dorsolateral prefrontal cortex, pars triangularis, and frontal pole, respectively), whereas terminations in Brodmann areas 4 (primary motor cortex), 47 (pars orbitalis), and 9 were also encountered in some specimens. In relation to the SLF system, the FLS represented its anterior continuation in the majority of the hemispheres, whereas in a few cases it was recorded as a completely distinct tract. Interestingly, the FLS comprised shorter fibers that were recorded to interconnect exclusively frontal areas, thus exhibiting different fiber architecture when compared to the long fibers forming the SLF. CONCLUSIONS: The current study provides consistent, focused, and robust evidence on the morphology, architecture, and correlative anatomy of the FLS. This fiber system participates in the axonal connectivity of the prefrontal-premotor cortices and allegedly subserves cognitive-motor functions. Based in the SLF hypersegmentation concept that has been advocated by previous authors, the FLS should be approached as a distinct frontal segment within the superior longitudinal system.

Spinal Atypical Rhabdoid Teratoid Tumor in an Adult Woman: Case Report and Review of the Literature.

BACKGROUND: Atypical rhabdoid teratoid tumors are very rare embryonal tumors that typically affect children younger than 3 years old and are encountered intracranially. CASE DESCRIPTION: Here, we describe the case of a 19-year-old woman who presented with gait disturbances and coccydynia. Imaging revealed a cauda equina mass. The tumor was partially resected. Histology reported loss of SMARCB1/INI1 expression and therefore the diagnosis of atypical rhabdoid teratoid was established. The patient underwent radiation treatment, but within 3 months 2 relapses were manifested. CONCLUSIONS: Atypical rhabdoid teratoids are exceptionally rare in adults and are seldom found in spine; only 8 such cases have been reported in the medical literature. They are invariantly characterized by multiple relapses and dismal prognosis. The clinician must be attentive of leptomeningeal disseminations and 22q11 deletion-associated comorbidities.

Dorsal component of the superior longitudinal fasciculus revisited: novel insights from a focused fiber dissection study.

OBJECTIVE: The aim of this study was to investigate the anatomical consistency, morphology, axonal connectivity, and correlative topography of the dorsal component of the superior longitudinal fasciculus (SLF-I) since the current literature is limited and ambiguous. METHODS: Fifteen normal, adult, formalin-fixed cerebral hemispheres were studied through a medial to lateral fiber microdissection technique. In 5 specimens, the authors performed stepwise focused dissections of the lateral cerebral aspect to delineate the correlative anatomy between the SLF-I and the other two SLF subcomponents, namely the SLF-II and SLF-III. RESULTS: The SLF-I was readily identified as a distinct fiber tract running within the cingulate or paracingulate gyrus and connecting the anterior cingulate cortex, the medial aspect of the superior frontal gyrus, the pre-supplementary motor area (pre-SMA), the SMA proper, the paracentral lobule, and the precuneus. With regard to the morphology of the SLF-I, two discrete segments were consistently recorded: an anterior and a posterior segment. A clear cleavage plane could be developed between the SLF-I and the cingulum, thus proving their structural integrity. Interestingly, no anatomical connection was revealed between the SLF-I and the SLF-II/SLF-III complex. CONCLUSIONS: Study results provide novel and robust anatomical evidence on the topography, morphology, and subcortical architecture of the SLF-I. This fiber tract was consistently recorded as a distinct anatomical entity of the medial cerebral aspect, participating in the axonal connectivity of high-order paralimbic areas.

Sledge runner fasciculus: anatomic architecture and tractographic morphology.

The sledge runner fasciculus (SRF) has been recently identified as a discrete fiber tract of the occipital lobe and has been allegedly implicated in the axonal connectivity of cortical areas conveying spatial navigation and visuospatial imagery. However, detailed knowledge regarding its anatomic and tractographic morphology is lacking. We thus opted to investigate the anatomy and connectivity of the SRF through cadaveric dissections and DTI studies. Twenty normal, adult, cerebral, cadaveric hemispheres treated with the Klingler's method were dissected through the fiber microdissection technique and 35 healthy participants from the MGH-USC Adult Diffusion Dataset (Human Connectome available dataset) underwent a tailored DTI protocol aiming to investigate the structural architecture of the SRF. SR was identified as a discrete fiber pathway, just under the U fibers of the medial occipital lobe, exhibiting a dorsomedial-ventrolateral trajectory and connecting the cortical areas of the anterior cuneus, anterior lingula, isthmus of the cingulum and posterior parahippocampal gyrus. The topography of the SR in relation to adjacent fiber pathways such as the cingulum, major forceps and stratum calcarinum is clearly delineated. Dissection and tractographic findings showed a good correspondence regarding SR topography, morphology and axonal connectivity. Our results support the hypothesis that the SRF is involved in the structural axonal connectivity of cerebral areas that strongly activate during spatial navigation and visuospatial imagery. Furthermore detailed anatomo-imaging evidence is provided on the microanatomic architecture of this newly discovered fiber tract.

Intrathecal Baclofen Therapy for Painful Muscle Spasms in a Patient with Friedreich's Ataxia.

Friedreich's ataxia (FA) is the most frequent hereditary ataxia syndrome, while painful muscle spasms and spasticity have been reported in 11-15% of FA patients. This report describes the successful management of painful spasms in a 65-year-old woman with FA via intrathecal baclofen (ITB) therapy following unsuccessful medical treatments. To our knowledge, this is the third reported case in the literature. Unfortunately, the pathophysiological characteristics of muscle spasms in FA are not well explored and understood while the therapeutic mechanisms of the different treatments are rather vague. Taking into consideration the suggested spinal atrophy in FA, the clinical resemblance of FA and chronic spinal injury muscle spasms, together with the rapid ITB therapy effectiveness in alleviating FA muscle spasms, we attempted to suggest a putative pathophysiological mechanism acting at the spinal level and possibly explained by the presence of independent spinal locomotor systems producing muscle spasms. Specifically, overexcitement of these centers, due to loss of normal regulation from upper CNS levels, may result in the uncontrolled firing of secondary motor neurons and may be the key to producing muscle spasms. However, further research under experimental and clinical settings seems to be necessary.

Defining the relationship of the optic radiation to the roof and floor of the ventricular atrium: a focused microanatomical study.

Objective: The authors investigated the specific topographic relationship of the optic radiation fibers to the roof and floor of the ventricular atrium because the current literature is ambiguous. Methods: Thirty-five normal, adult, formalin-fixed cerebral hemispheres and 30 focused MRI slices at the level of the atrium were included in the study. The correlative anatomy of the optic radiation with regard to the atrial roof and floor was investigated in 15 specimens, each through focused fiber microdissections. The remaining 5 hemispheres were explored with particular emphasis on the trajectory of the collateral sulcus in relation to the floor of the atrium. In addition, the trajectory of the collateral sulcus was evaluated in 30 MRI scans. Results: The atrial roof was observed to be devoid of optic radiations in all studied hemispheres, whereas the atrial floor was seen to harbor optic fibers on its lateral part. Moreover, the trajectory of the intraparietal sulcus, when followed, was always seen to correspond to the roof of the atrium, thus avoiding the optic pathway, whereas that of the collateral sulcus was found to lead to either the lateral atrial floor or outside the ventricle in 88% of the cases, therefore hitting the visual pathway. Conclusions: Operative corridors accessing the ventricular atrium should be carefully tailored through detailed preoperative planning and effective use of intraoperative navigation to increase patient safety and enhance the surgeon's maneuverability. The authors strongly emphasize the significance of accurate anatomical knowledge.

Parietal association deficits in patients harboring parietal lobe gliomas: a prospective study.

OBJECTIVE: Although the parietal lobe is a common site for glioma formation, current literature is scarce, consists of retrospective studies, and lacks consistency with regard to the incidence, nature, and severity of parietal association deficits (PADs). The aim of this study was to assess the characteristics and incidence of PADs in patients suffering from parietal lobe gliomas through a prospective study and a battery of comprehensive neuropsychological tests. METHODS: Between 2012 and 2016 the authors recruited 38 patients with glioma confined in the parietal lobe. Patients were examined for primary and secondary association deficits with a dedicated battery of neuropsychological tests. The PADs were grouped into 5 categories: visuospatial attention, gnosis, praxis, upper-limb coordination, and language. For descriptive analysis tumors were divided into high- and low-grade gliomas and also according to patient age and tumor size. RESULTS: Parietal association deficits were elicited in 80% of patients, thus being more common than primary deficits (50%). Apraxia was the most common PAD (47.4%), followed by anomic aphasia and subcomponents of Gerstmann's syndrome (34.2% each). Other deficits such as hemineglect, stereoagnosia, extinction, and visuomotor ataxia were also detected, albeit at lower rates. There was a statistically nonsignificant difference between PADs and sex (72.2% males, 85% females) and age (77.8% at ≤ 60 years, 80% at age > 60 years), but a statistically significant difference between the > 4 cm and the ≤ 4 cm diameter group (p = 0.02, 94.7% vs 63.2%, respectively). There was a tendency (p = 0.094) for low-grade gliomas to present with fewer PADs (50%) than high-grade gliomas (85.7%). Tumor laterality showed a strong correlation with hemineglect (p = 0.004, predilection for right hemisphere), anomia (p = 0.001), and Gerstmann's symptoms (p = 0.01); the last 2 deficits showed a left (dominant) hemispheric preponderance. CONCLUSIONS: This is the first study to prospectively evaluate the incidence and nature of PADs in patients with parietal gliomas. It could be that the current literature may have underestimated the true incidence of deficits. Dedicated neuropsychological examination detects a high frequency of PADs, the most common being apraxia, followed by anomia and subcomponents of Gerstmann's syndrome. Nevertheless, a direct correlation between the clinical deficit and its anatomical substrate is only possible to a limited extent, highlighting the need for intraoperative cortical and subcortical functional mapping.

The habenula in neurosurgery for depression: A convergence of functional neuroanatomy, psychiatry and imaging.

BACKGROUND: The habenula is a small, mostly underrated structure in the pineal region. Multidisciplinary findings demonstrate an underlying complex connectivity of the habenula with the rest of the brain, subserving its major role in normal behavior and the pathophysiology of depression. These findings suggest the potential application of "habenular psychosurgery" in the treatment of mental disorders. OBJECTIVE/HYPOTHESIS: The remission of two patients with treatment-resistant major depression treated with deep brain stimulation of the habenula supported the hypothesis that the habenula is an effective target for deep brain stimulation and initiated a surge of basic science research. This review aims to assess the viability of the deep brain stimulation of the habenula as a treatment option for treatment resistant depression. METHODS: PubMed and the Cochrane Library databases were searched with no chronological restrictions for the identification of relevant articles. RESULTS: The results of this review are presented in a narrative form describing the functional neuroanatomy of the human habenula, its implications in major depression, findings of electrode implantation of this region and findings of deep brain stimulation of the habenula for the treatment of depression. CONCLUSION: Data assessing the hypothesis are scarce. Nonetheless, findings highlight the major role of the habenula in normal, as well as in pathological brain function, particularly in depression disorders. Moreover, findings of studies utilizing electrode implantation in the region of the habenula underscore our growing realization that research in neuroscience and deep brain stimulation complement each other in a reciprocal relationship; they are as self-reliant, as much as they depend on each other.