RESUMEN

OBJECTIVE: The object of this study was to present the surgical results of a large, single-surgeon consecutive series of patients who had undergone transcisternal (TCi) or transcallosal-transventricular (TCTV) endoscope-assisted microsurgery for thalamic lesions. METHODS: This is a retrospective study of a consecutive series of patients harboring thalamic lesions and undergoing surgery at one institution between February 2007 and August 2019. All surgical and patient-related data were prospectively collected. Depending on the relationship between the lesion and the surgically accessible thalamic surfaces (lateral ventricle, velar, cisternal, and third ventricle), one of the following surgical TCi or TCTV approaches was chosen: anterior interhemispheric transcallosal (AIT), posterior interhemispheric transtentorial subsplenial (PITS), perimedian supracerebellar transtentorial (PeST), or perimedian contralateral supracerebellar suprapineal (PeCSS). Since January 2018, intraoperative MRI has also been part of the protocol. The main study outcome was extent of resection. Complete neurological examination took place preoperatively, at discharge, and 3 months postoperatively. Descriptive statistics were calculated for the whole cohort. RESULTS: In the study period, 92 patients underwent surgery for a thalamic lesion: 81 gliomas, 6 cavernous malformations, 2 germinomas, 1 metastasis, 1 arteriovenous malformation, and 1 ependymal cyst. In none of the cases was a transcortical approach adopted. Thirty-five patients underwent an AIT approach, 35 a PITS, 19 a PeST, and 3 a PeCSS. The mean follow-up was 38 months (median 20 months, range 1-137 months). No patient was lost to follow-up. The mean extent of resection was 95% (median 100%, range 21%-100%), and there was no surgical mortality. Most patients (59.8%) experienced improvement in their Karnofsky Performance Status. New permanent neurological deficits occurred in 8 patients (8.7%). Early postoperative (< 3 months after surgery) problems in CSF circulation requiring diversion occurred in 7 patients (7.6%; 6/7 cases in patients with high-grade glioma). CONCLUSIONS: Endoscope-assisted microsurgery allows for the removal of thalamic lesions with acceptable morbidity. Surgeons must strive to access any given thalamic lesion through one of the four accessible thalamic surfaces, as they can be reached through either a TCTV or TCi approach with no or minimal damage to normal brain parenchyma. Patients harboring a high-grade glioma are likely to develop a postoperative disturbance of CSF circulation. For this reason, the AIT approach should be favored, as it facilitates a microsurgical third ventriculocisternostomy and allows intraoperative MRI to be done.

RESUMEN

OBJECTIVE: The goal of this study was to demonstrate the use of quantitative susceptibility mapping (QSM)-based images to precisely localize the globus pallidus internus (GPi) for deep brain stimulation (DBS) planning and to enhance postsurgical visualization of the DBS lead positions. METHODS: Presurgical T1-weighted (T1w), T2-weighted (T2w), and QSM images as well as postsurgical CT images were obtained in 29 patients with Parkinson's disease. To enhance the contrast within the GP, a hybrid contrast was created by linearly combining T1w and QSM images. Contrast-to-noise ratios (CNRs) of the GPi on T1w, T2w, QSM, and hybrid images were compared. The CNR differences were tested using the 1-way ANOVA method. The visualization of the DBS lead position was demonstrated by merging the postsurgical CT with presurgical MR images. RESULTS: The hybrid images yield the best CNRs for GPi depiction and the visualization of the postsurgical DBS lead position was significantly improved. CONCLUSIONS: QSM-based images allow for confident localization of borders of the GPi that is superior to T1w and T2w images. High-contrast hybrid images can be used for precisely directed DBS targeting, e.g., GPi DBS for the treatment of advanced Parkinson's disease.

RESUMEN

OBJECTIVE: Despite the extensive use of the subthalamic nucleus (STN) as a deep brain stimulation (DBS) target, unveiling the extensive functional connectivity of the nucleus, relating its structural connectivity to the stimulation-induced adverse effects, and thus optimizing the STN targeting still remain challenging. Mastering the 3D anatomy of the STN region should be the fundamental goal to achieve ideal surgical results, due to the deep-seated and obscure position of the nucleus, variable shape and relatively small size, oblique orientation, and extensive structural connectivity. In the present study, the authors aimed to delineate the 3D anatomy of the STN and unveil the complex relationship between the anatomical structures within the STN region using fiber dissection technique, 3D reconstructions of high-resolution MRI, and fiber tracking using diffusion tractography utilizing a generalized q-sampling imaging (GQI) model. METHODS: Fiber dissection was performed in 20 hemispheres and 3 cadaveric heads using the Klingler method. Fiber dissections of the brain were performed from all orientations in a stepwise manner to reveal the 3D anatomy of the STN. In addition, 3 brains were cut into 5-mm coronal, axial, and sagittal slices to show the sectional anatomy. GQI data were also used to elucidate the connections among hubs within the STN region. RESULTS: The study correlated the results of STN fiber dissection with those of 3D MRI reconstruction and tractography using neuronavigation. A 3D terrain model of the subthalamic area encircling the STN was built to clarify its anatomical relations with the putamen, globus pallidus internus, globus pallidus externus, internal capsule, caudate nucleus laterally, substantia nigra inferiorly, zona incerta superiorly, and red nucleus medially. The authors also describe the relationship of the medial lemniscus, oculomotor nerve fibers, and the medial forebrain bundle with the STN using tractography with a 3D STN model. CONCLUSIONS: This study examines the complex 3D anatomy of the STN and peri-subthalamic area. In comparison with previous clinical data on STN targeting, the results of this study promise further understanding of the structural connections of the STN, the exact location of the fiber compositions within the region, and clinical applications such as stimulation-induced adverse effects during DBS targeting.

Asunto(s)

RESUMEN

OBJECTIVE Unilateral Gamma Knife thalamotomy (GKT) is a well-established treatment for patients with medically refractory tremor who are not eligible for invasive procedures due to increased risk of compications. The purpose of this study was to evaluate whether staged bilateral GKT provides benefit with acceptable risk to patients suffering from disabling medically refractory bilateral tremor. METHODS Eleven patients underwent staged bilateral GKT during a 17-year period (1999-2016). Eight patients had essential tremor (ET), 2 had Parkinson's disease (PD)-related tremor, and 1 had multiple-sclerosis (MS)-related tremor. For the first GKT, a median maximum dose of 140 Gy was delivered to the posterior-inferior region of the nucleus ventralis intermedius (VIM) through a single isocenter with 4-mm collimators. Patients who benefitted from unilateral GKT were eligible for a contralateral GKT 1-2 years later (median 22 months). For the second GKT, a median maximum dose of 130 Gy was delivered to the opposite VIM nucleus to a single 4-mm isocenter. The Fahn-Tolosa-Marin (FTM) clinical tremor rating scale was used to score tremor, drawing, and drinking before and after each GKT. The FTM writing score was assessed only for the dominant hand before and after the first GKT. The Karnofsky Performance Status (KPS) was used to assess quality of life and activities of daily living before and after the first and second GKT. RESULTS The median time to last follow-up after the first GKT was 35 months (range 11-70 months). All patients had improvement in at least 1 FTM score after the first GKT. Three patients (27.3%) had tremor arrest and complete restoration of function (noted via FTM tremor, writing, drawing, and drinking scores equaling zero). No patient had tremor recurrence or diminished tremor relief after the first GKT. One patient experienced new temporary neurological deficit (contralateral lower-extremity hemiparesis) from the first GKT. The median time to last follow-up after the second GKT was 12 months (range 2-70 months). Nine patients had improvement in at least 1 FTM score after the second GKT. Two patients had tremor arrest and complete restoration of function. No patient experienced tremor recurrence or diminished tremor relief after the second GKT. No patient experienced new neurological or radiological adverse effect from the second GKT. Statistically significant improvements were noted in the KPS score following the first and second GKT. CONCLUSIONS Staged bilateral GKT provided effective relief for medically refractory, disabling, bilateral tremor without increased risk of neurological complications. It is an appropriate strategy for carefully selected patients with medically refractory bilateral tremor who are not eligible for deep brain stimulation.

Asunto(s)

RESUMEN

OBJECTIVE The role of tractography in Gamma Knife thalamotomy (GK-T) planning is still unclear. Pyramidal tractography might reduce the risk of radiation injury to the pyramidal tract and reduce motor complications. METHODS In this study, the ventralis intermedius nucleus (VIM) targets of 20 patients were bilaterally defined using Iplannet Stereotaxy Software, according to the anterior commissure-posterior commissure (AC-PC) line and considering the localization of the pyramidal tract. The 40 targets and tractography were transferred as objects to the GammaPlan Treatment Planning System (GP-TPS). New targets were defined, according to the AC-PC line in the functional targets section of the GP-TPS. The target offsets required to maintain the internal capsule (IC) constraint of < 15 Gy were evaluated. In addition, the strategies available in GP-TPS to maintain the minimum conventional VIM target dose at > 100 Gy were determined. RESULTS A difference was observed between the positions of both targets and the doses to the IC. The lateral (x) and the vertical (z) coordinates were adjusted 1.9 mm medially and 1.3 mm cranially, respectively. The targets defined considering the position of the pyramidal tract were more medial and superior, based on the constraint of 15 Gy touching the object representing the IC in the GP-TPS. The best strategy to meet the set constraints was 90° Gamma angle (GA) with automatic shaping of dose distribution; this was followed by 110° GA. The worst GA was 70°. Treatment time was substantially increased by the shaping strategy, approximately doubling delivery time. CONCLUSIONS Routine use of DTI pyramidal tractography might be important to fine-tune GK-T planning. DTI tractography, as well as anisotropy showing the VIM, promises to improve Gamma Knife functional procedures. They allow for a more objective definition of dose constraints to the IC and targeting. DTI pyramidal tractography introduced into the treatment planning may reduce the incidence of motor complications and improve efficacy. This needs to be validated in a large clinical series.

Asunto(s)

RESUMEN

OBJECTIVE Diffusion tensor imaging (DTI) for the assessment of fractional anisotropy (FA) and involving measurements of mean diffusivity (MD) and apparent diffusion coefficient (ADC) represents a novel, MRI-based, noninvasive technique that may delineate microstructural changes in cerebral white matter (WM). For example, DTI may be used for the diagnosis and differentiation of idiopathic normal pressure hydrocephalus (iNPH) from other neurodegenerative diseases with similar imaging findings and clinical symptoms and signs. The goal of the current study was to identify and analyze recently published series on the use of DTI as a diagnostic tool. Moreover, the authors also explored the utility of DTI in identifying patients with iNPH who could be managed by surgical intervention. METHODS The authors performed a literature search of the PubMed database by using any possible combinations of the following terms: "Alzheimer's disease," "brain," "cerebrospinal fluid," "CSF," "diffusion tensor imaging," "DTI," "hydrocephalus," "idiopathic," "magnetic resonance imaging," "normal pressure," "Parkinson's disease," and "shunting." Moreover, all reference lists from the retrieved articles were reviewed to identify any additional pertinent articles. RESULTS The literature search retrieved 19 studies in which DTI was used for the identification and differentiation of iNPH from other neurodegenerative diseases. The DTI protocols involved different approaches, such as region of interest (ROI) methods, tract-based spatial statistics, voxel-based analysis, and delta-ADC analysis. The most studied anatomical regions were the periventricular WM areas, such as the internal capsule (IC), the corticospinal tract (CST), and the corpus callosum (CC). Patients with iNPH had significantly higher MD in the periventricular WM areas of the CST and the CC than had healthy controls. In addition, FA and ADCs were significantly higher in the CST of iNPH patients than in any other patients with other neurodegenerative diseases. Gait abnormalities of iNPH patients were statistically significantly and negatively correlated with FA in the CST and the minor forceps. Fractional anisotropy had a sensitivity of 94% and a specificity of 80% for diagnosing iNPH. Furthermore, FA and MD values in the CST, the IC, the anterior thalamic region, the fornix, and the hippocampus regions could help differentiate iNPH from Alzheimer or Parkinson disease. Interestingly, CSF drainage or ventriculoperitoneal shunting significantly modified FA and ADCs in iNPH patients whose condition clinically responded to these maneuvers. CONCLUSIONS Measurements of FA and MD significantly contribute to the detection of axonal loss and gliosis in the periventricular WM areas in patients with iNPH. Diffusion tensor imaging may also represent a valuable noninvasive method for differentiating iNPH from other neurodegenerative diseases. Moreover, DTI can detect dynamic changes in the WM tracts after lumbar drainage or shunting procedures and could help identify iNPH patients who may benefit from surgical intervention.

Asunto(s)

RESUMEN

Chronic neuropathic pain is estimated to affect 3%-4.5% of the worldwide population. It is associated with significant loss of productive time, withdrawal from the workforce, development of mood disorders such as depression and anxiety, and disruption of family and social life. Current medical therapeutics often fail to adequately treat chronic neuropathic pain. Deep brain stimulation (DBS) targeting subcortical structures such as the periaqueductal gray, the ventral posterior lateral and medial thalamic nuclei, and the internal capsule has been investigated for the relief of refractory neuropathic pain over the past 3 decades. Recent work has identified the dorsal anterior cingulate cortex (dACC) as a new potential neuromodulation target given its central role in cognitive and affective processing. In this review, the authors briefly discuss the history of DBS for chronic neuropathic pain in the United States and present evidence supporting dACC DBS for this indication. They review existent literature on dACC DBS and summarize important findings from imaging and neurophysiological studies supporting a central role for the dACC in the processing of chronic neuropathic pain. The available neurophysiological and empirical clinical evidence suggests that dACC DBS is a viable therapeutic option for the treatment of chronic neuropathic pain and warrants further investigation.

Asunto(s)

RESUMEN

OBJECT: The goal in this study was to explore and further refine comprehension of the anatomical features of the temporal loop, known as Meyer's loop. METHODS: The lateral and inferior aspects of 20 previously frozen, formalin-fixed human brains were dissected under the operating microscope by using fiber microdissection. RESULTS: A loop of the fibers in the anterior temporal region was clearly demonstrated in all dissections. This temporal loop, or Meyer's loop, is commonly known as the anterior portion of the optic radiation. Fiber microdissection in this study, however, revealed that various projection fibers that emerge from the sublentiform portion of the internal capsule (IC-SL), which are the temporopontine fibers, occipitopontine fibers, and the posterior thalamic peduncle (which includes the optic radiation), participate in this temporal loop and become a part of the sagittal stratum. No individual optic radiation fibers could be differentiated in the temporal loop. The dissections also disclosed that the anterior extension and angulation of the temporal loop vary significantly. CONCLUSIONS: The fiber microdissection technique provides clear evidence that a loop in the anterior temporal region exists, but that this temporal loop is not formed exclusively by the optic radiation. Various projection fibers of the IC-SL, of which the optic radiation is only one of the several components, display this common course. The inherent limitations of the fiber dissection technique preclude accurate differentiation among individual fibers of the temporal loop, such as the optic radiation fibers.

Asunto(s)