Posts Tagged ‘Brain mapping’
Background: During awake craniotomies, patients may either be awake for the entire duration of the surgical intervention (awake-awake-awake craniotomy, AAA) or initially sedated (asleep-awake-asleep craniotomy, SAS).
Objective: To examine whether prior sedation in SAS may restrict brain mapping, we conducted neuropsychological tests in patients by means of a standardized anesthetic regimen comparable to an SAS.
Methods: We prospectively examined patients undergoing surgery either under total intravenous anesthesia (TIVA) or under regional anesthesia with slight sedation (RAS). The tests included the DO40 picture-naming test, the digit span, the Regensburg Word Fluency Test, and the finger-tapping test. Each test was conducted 3 times for every patient in the TIVA and RAS groups, once before surgery and twice within about 35 minutes after the end of sedation. Patients undergoing AAA were examined preoperatively and intraoperatively.
Background: Recent findings associated with resting state cortical networks have provided insight into the brain’s organizational structure. In addition to their neuroscientific implications, the networks identified by resting state functional MRI (rs-fMRI) may prove useful for clinical brain mapping.
Objective: To demonstrate that a data-driven approach to analyze resting state networks is useful in identifying regions classically understood to be eloquent cortex as well as other functional networks.
Methods: Study included six subjects undergoing surgical treatment for intractable epilepsy and seven subjects undergoing tumor resection. rs-fMRI data were obtained prior to surgery and seven canonical resting state networks (RSNs) were identified by an artificial neural network algorithm. Of these seven, the motor and language networks were then compared to electrocortical stimulation as the gold standard in the epilepsy patients. The sensitivity and specificity for identifying these eloquent sites was calculated at varying thresholds, which yielded receiver operating characteristic (ROC) curves and their associated area under the curve (AUC). RSN networks were plotted in the tumor subjects to observe RSN distortions in altered anatomy.
Background: Microsurgery within eloquent cortex is a controversial approach due to the high-risk of permanent neurological deficit. Few data exist showing the relationship between mapping stimulation intensity required for eliciting a muscle motor evoked potential (MEP) and distance to the motor neurons; furthermore, the motor threshold at which no deficit occurs remains to be defined.
Objective: To evaluate the safety of low threshold MEP mapping for tumor resection close to the primary motor cortex.
Methods: Fourteen patients undergoing tumor surgery were included. Motor threshold was defined as the stimulation intensity that elicited MEPs from target muscles (amplitude >30[mu]V). Monopolar high-frequency motor mapping with train-of-five stimuli (HF-TOF) (pulse duration=500[mu]s; interstimulus interval=4.0ms; frequency=250Hz) was used to determine motor response negative sites where incision and dissection could be performed. At sites negative to 3mA HF-TOF stimulation, the tumor was resected.
Background: Despite intraoperative technical improvements, the insula remains a challenging area for surgery because of its critical relationships with vascular and neurophysiological functional structures.
Objective: To retrospectively investigate the morbidity profile in insular nonenhancing gliomas, with special emphasis on volumetric analysis of tumoral resection.
Methods: From 2000 to 2010, 66 patients underwent surgery. All surgical procedures were conducted under cortical-subcortical stimulation and neurophysiological monitoring. Volumetric scan analysis was applied on T2-weighted magnetic resonance images (MRIs) to establish preoperative and postoperative tumoral volume.
Ahead of Print: Safe Resection of Arteriovenous Malformations in Eloquent Motor Areas Aided by Functional Imaging and Intraoperative Monitoring
BACKGROUND: Arteriovenous malformations (AVMs) proximal to motor cortical areas or motor projection systems are challenging to manage due to the risk of severe sensory and motor impairment. Surgical indication in these cases therefore remains controversial.
OBJECTIVE: To propose a standardized approach for centrally situated AVMs, based on functional imaging and intraoperative electrophysiological evaluation.
METHODS: We conducted a retrospective analysis of 15 patients who underwent surgical treatment for AVMs in motor cortical areas or proximal to motor projections. Preoperative assessment included fMRI and 3D-tractography. Operations were performed under continuous electrophysiological monitoring aided by direct brain stimulation. We identified critical bloody supply to the motor areas by temporary occluding the feeding vessels under electrophysiological monitorization. Clinical outcome was evaluated using the modified Rankin Scale.
OBJECTIVE: Electrostimulation was used to study neuronal substrates involved in spatial awareness in humans.
METHODS: Spatial neglect was studied using a line bisection task in combination with electrostimulation mapping of the right hemisphere in 50 cases. Stimulation sites were identified using Talairach’s coordinates. The behavioral effects induced by stimulation, especially eye movements and deviations from the median, were quantified and compared to pre-operative data and to a control group.