Axoplasmic flow of tritiated proline in the corticospinal tract of the rat

Abstract Muscle motor-evoked potentials are commonly monitored during brain tumour surgery in motor areas, as these are assumed to reflect the integrity of descending motor pathways, including the corticospinal tract. However, while the loss of muscle motor-evoked potentials at the end of surgery is associated with long-term motor deficits (muscle motor-evoked potential-related deficits), there is increasing evidence that motor deficit can occur despite no change in muscle motor-evoked potentials (muscle motor-evoked potential-unrelated deficits), particularly after surgery of non-primary regions involved in motor control. In this study, we aimed to investigate the incidence of muscle motor-evoked potential-unrelated deficits and to identify the associated brain regions. We retrospectively reviewed 125 consecutive patients who underwent surgery for peri-Rolandic lesions using intra-operative neurophysiological monitoring. Intraoperative changes in muscle motor-evoked potentials were correlated with motor outcome, assessed by the Medical Research Council scale. We performed voxel–lesion–symptom mapping to identify which resected regions were associated with short- and long-term muscle motor-evoked potential-associated motor deficits. Muscle motor-evoked potentials reductions significantly predicted long-term motor deficits. However, in more than half of the patients who experienced long-term deficits (12/22 patients), no muscle motor-evoked potential reduction was reported during surgery. Lesion analysis showed that muscle motor-evoked potential-related long-term motor deficits were associated with direct or ischaemic damage to the corticospinal tract, whereas muscle motor-evoked potential-unrelated deficits occurred when supplementary motor areas were resected in conjunction with dorsal premotor regions and the anterior cingulate. Our results indicate that long-term motor deficits unrelated to the corticospinal tract can occur more often than currently reported. As these deficits cannot be predicted by muscle motor-evoked potentials, a combination of awake and/or novel asleep techniques other than muscle motor-evoked potentials monitoring should be implemented.

Download Full-text

Free will and neurosurgical resections of the supplementary motor area: a critical review

Acta Neurochirurgica ◽

10.1007/s00701-021-04748-9 ◽

2021 ◽

Vol 163 (5) ◽

pp. 1229-1237 ◽

Cited By ~ 1

Author(s):

Rickard L Sjöberg

Keyword(s):

Executive Function ◽

Free Will ◽

Corticospinal Tract ◽

Supplementary Motor Area ◽

Personal Responsibility ◽

Motor Area ◽

Simple Motor ◽

Motor Actions ◽

Intense Debate

Abstract Background Research suggests that unconscious activity in the supplementary motor area (SMA) precedes not only certain simple motor actions but also the point at which we become aware of our intention to perform such actions. The extent to which these findings have implications for our understanding of the concepts of free will and personal responsibility has been subject of intense debate during the latest four decades. Methods This research is discussed in relation to effects of neurosurgical removal of the SMA in a narrative review. Results Removal of the SMA typically causes a transient inability to perform non-stimulus-driven, voluntary actions. This condition, known as the SMA syndrome, does not appear to be associated with a loss of sense of volition but with a profound disruption of executive function/cognitive control. Conclusions The role of the SMA may be to serve as a gateway between the corticospinal tract and systems for executive function. Such systems are typically seen as tools for conscious decisions. What is known about effects of SMA resections would thus seem to suggest a view that is compatible with concepts of personal responsibility. However, the philosophical question whether free will exists cannot be definitely resolved on the basis of these observations.

Download Full-text

Relationship between fractional anisotropy and neuropsychological evaluation in sports-related concussion

Neurology ◽

10.1212/01.wnl.0000550605.03730.d7 ◽

2018 ◽

Vol 91 (23 Supplement 1) ◽

pp. S17.1-S17

Author(s):

Haruo Nakayama ◽

Yu Hiramoto ◽

Yuriko Numata ◽

Satoshi Fujita ◽

Nozomi Hirai ◽

...

Keyword(s):

Processing Speed ◽

Corticospinal Tract ◽

Diffusion Tensor ◽

Neuropsychological Testing ◽

Diffusion Tensor Mri ◽

Neuropsychological Evaluation ◽

Neuropsychological Function ◽

Significant Fluctuation ◽

The Relationship ◽

The Brain

ObjectiveTo evaluate the relationship between functional anisotropy (FA) and neuropsychological evaluation in concussion.MethodsDiffusion tensor MRI included FA of the Brain and neuropsychological evaluation were conducted on 10 patients with concussion who were diagnosed from April 2017 to March 2018. FA was extracted from 2 regions of interest in Corpus callosum (CC) and corticospinal tract (CT). Detailed neuropsychological testing with an emphasis on Working memory (WM) and Processing speed (PS) was also conducted. The FA value in that 2 regions were compared between the 2 groups of 5 patients (group F) who failed either in WM or PS and 5 cases (group NF) who did not admit it.ResultsMean FA values in CC and CT in the Group F were 0.70 and 0.52. Mean FA values in CC and CT in the Group NF were 0.48 and 0.55.ConclusionsOur result suggests that the FA value of CC did not explain the significant fluctuation of the neuropsychological function. However, FA value in CT were shown to explain the fluctuation of WM and PS.

Download Full-text

Intraoperative mapping of pre-central motor cortex and subcortex: a proposal for supplemental cortical and novel subcortical maps to Penfield’s motor homunculus

Brain Structure and Function ◽

10.1007/s00429-021-02274-z ◽

2021 ◽

Author(s):

Prajwal Ghimire ◽

Jose Pedro Lavrador ◽

Asfand Baig Mirza ◽

Noemia Pereira ◽

Hannah Keeble ◽

...

Keyword(s):

Brain Mapping ◽

Retrospective Cohort ◽

Corticospinal Tract ◽

Brain Lesions ◽

Body Parts ◽

Single Institution ◽

Motor Representation ◽

Motor Mapping ◽

Subcortical Stimulation ◽

Motor Maps

AbstractPenfield’s motor homunculus describes a caricaturised yet useful representation of the map of various body parts on the pre-central cortex. We propose a supplemental map of the clinically represented areas of human body in pre-central cortex and a novel subcortical corticospinal tract map. We believe this knowledge is essential for safe surgery in patients with eloquent brain lesions. A single-institution retrospective cohort study of patients who underwent craniotomy for motor eloquent lesions with intraoperative motor neuromonitoring (cortical and subcortical) between 2015 and 2020 was performed. All positive cortical and subcortical stimulation points were taken into account and cartographic maps were produced to demonstrate cortical and subcortical areas of motor representation and their configuration. A literature review in PubMed was performed. One hundred and eighty consecutive patients (58.4% male, 41.6% female) were included in the study with 81.6% asleep and 18.4% awake craniotomies for motor eloquent lesions (gliomas 80.7%, metastases 13.8%) with intraoperative cortical and subcortical motor mapping. Based on the data, we propose a supplemental clinical cortical and a novel subcortical motor map to the original Penfield’s motor homunculus, including demonstration of localisation of intercostal muscles both in the cortex and subcortex which has not been previously described. The supplementary clinical cortical and novel subcortical motor maps of the homunculus presented here have been derived from a large cohort of patients undergoing direct cortical and subcortical brain mapping. The information will have direct relevance for improving the safety and outcome of patients undergoing resection of motor eloquent brain lesions.

Download Full-text

Neurophysiologic Mapping of Thalamocortical Tract in Asleep Craniotomies: Promising Results From an Early Experience

Operative Neurosurgery ◽

10.1093/ons/opaa330 ◽

2020 ◽

Author(s):

Mirela V Simon ◽

Daniel K Lee ◽

Bryan D Choi ◽

Pratik A Talati ◽

Jimmy C Yang ◽

...

Keyword(s):

General Anesthesia ◽

Corticospinal Tract ◽

Sensory Function ◽

Motor Deficit ◽

Motor Deficits ◽

Central Sulcus ◽

Postcentral Gyrus ◽

Subcortical Stimulation ◽

Subcortical Mapping

Abstract BACKGROUND Subcortical mapping of the corticospinal tract has been extensively used during craniotomies under general anesthesia to achieve maximal resection while avoiding postoperative motor deficits. To our knowledge, similar methods to map the thalamocortical tract (TCT) have not yet been developed. OBJECTIVE To describe a neurophysiologic technique for TCT identification in 2 patients who underwent resection of frontoparietal lesions. METHODS The central sulcus (CS) was identified using the somatosensory evoked potentials (SSEP) phase reversal technique. Furthermore, monitoring of the cortical postcentral N20 and precentral P22 potentials was performed during resection. Subcortical electrical stimulation in the resection cavity was done using the multipulse train (case #1) and Penfield (case #2) techniques. RESULTS Subcortical stimulation within the postcentral gyrus (case #1) and in depth of the CS (case #2), resulted in a sudden drop in amplitudes in N20 (case #1) and P22 (case #2), respectively. In both patients, the potentials promptly recovered once the stimulation was stopped. These results led to redirection of the surgical plane with avoidance of damage of thalamocortical input to the primary somatosensory (case #1) and motor regions (case #2). At the end of the resection, there were no significant changes in the median SSEP. Both patients had no new long-term postoperative sensory or motor deficit. CONCLUSION This method allows identification of TCT in craniotomies under general anesthesia. Such input is essential not only for preservation of sensory function but also for feedback modulation of motor activity.

Download Full-text