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

Functional connectivity of sensorimotor network before and after surgery in the supplementary motor area

After resective glioma surgery in the Supplementary Motor Area (SMA), patients often experience a transient disturbance of the ability to initiate speech and voluntary motor actions, known as the SMA syndrome (SMAS). It has been proposed that enhanced interhemispheric functional connectivity (FC) within the sensorimotor system may serve as a potential mechanism for recovery, enabling the non-resected SMA to assume the function of the resected region. The purpose of the present study was to investigate the extent to which changes in FC can be observed in patients after resolution of the SMAS. Eight patients underwent resection of left SMA due to suspected gliomas, resulting in various levels of the SMA syndrome. Resting-state functional MR images were acquired prior to the surgery and after resolution of the syndrome. At the group level we found an increased connectivity between the unaffected (right) SMA and the primary motor cortex on the same side following surgery. However, no significant increase in interhemispheric connectivity was observed. These findings challenge the prevailing notion that increased interhemispheric FC serves as the only mechanism underlying recovery from SMA syndrome and suggest the presence of one or more alternative mechanisms.

What is the Philosophy of Neurosurgery? Systematic Review and Defining the Discipline

INTRODUCTION

Despite centuries of joint investigation of philosophy and neurological interventions, a founding account for the philosophy of neurosurgery has yet to be rigorously constructed or defended. This paper reviews recent work on the philosophy of neurosurgery, spanning metaphysics, epistemology, and value theory, to establish a framework and clinical relevance for study in the philosophy of neurosurgery.

METHODS

A systematic review of an online database was conducted using the broad search terms, "Philosophy AND (Neurosurgery OR Neurological Surgery)." Records were included if they demonstrated relevance to the philosophy of neurosurgery and analytical rigor, but were excluded if solely legal, clinical, or ethical principles were considered without substantive discussion of underlying ethical frameworks and philosophical principles.

RESULTS

Of 8025 candidates from online and print records, 16 records (14 from online sources and 2 from an edited volume) met inclusion criteria for the systematic review. Three dealt with metaphysics, 3 dealt with epistemology, 4 dealt with value theory, 5 dealt with metaphysics/epistemology, and 1 dealt with value theory/metaphysics. Questions of free will, consciousness, personal identity, neurosurgical knowledge, ascription of other minds, deontology, and minimalism, among others, were considered.

DISCUSSION

Based on identified studies, the philosophy of neurosurgery is defined as the discipline of rigorously and methodically addressing metaphysical, epistemological, and value-theoretic questions arising from physically intervening in the nervous system. We discuss future directions for questions within the philosophy of neurosurgery and consider their relevance for patient care and the practice of neurosurgery.

Persistent hemiplegia with normal intraoperative neurophysiological monitoring in supratentorial neurosurgery: a case report and review of literature

Intraoperative neurophysiological monitoring (IONM) is needed for evaluating and demonstrating the integrity of the central and peripheral nervous system during surgical manoeuvres that take place in proximity to eloquent motor and somatosensory nervous structures. The integrity of the monitored motor pathways is not always followed by consistent clinical normality, particularly in the first hours/days following surgery, when surgical resection involves brain structures such as the supplementary motor areas (SMA). We report the case of a patient who underwent surgical excision of a right frontal glioblastoma with normal preoperative, intraoperative (IONM), and postoperative central motor conduction, but with persistent postoperative hemiplegia (> 6 months). The literature regarding SMA syndrome and its diagnosis and prognosis is reviewed.

Brain stimulation and elicited memories

BACKGROUND

Since the late 1930s, electric brain stimulation (EBS) in awake patients has been known to occasionally elicit patient descriptions of a form of memory flashbacks, known as experiential phenomena. One understanding of these sensations are as caused by an augmentation of the capacity for memory retrieval. However, an alternative hypothesis holds that memory flashbacks during EBS are "synthetic constructions" in the form of mental events, falsely interpreted as memories.

METHODS

A critical narrative review is used to discuss the false memory hypothesis in relation to the current empirical literature and source attribution theory.

RESULTS

EBS as well as situational demands in the form of interaction between patient and neurosurgeon may both lead to the creation of mental events and influence their interpretation in a way that may create false memories. The false memory hypothesis provides a potential explanation for several apparent inconsistencies in the current literature such as (a) the fragmented nature of experiential reports, (b) the ability of EBS to induce memory retrieval errors in controlled studies, (c) that Penfield's elicitations of experiential phenomena are so rarely replicated in the modern era, and (d) the limited utility of techniques that elicit experiential phenomena in the treatment of memory disorders.

CONCLUSIONS

The hypothesis that experiential phenomena may largely be "synthetic constructions" deserves serious consideration by neurosurgeons.

Five psychological mechanisms that might bias learning from neurosurgical complications: case discussions and a narrative review

PURPOSE

The ability of neurosurgeons to analyze and reflect on their complications in a constructive way is important both for professional development and for patient safety. The purpose of the present paper is to highlight some psychological factors that might impair or bias the ability of the neurosurgeon to do this successfully.

METHODS

Five fictitious cases, loosely inspired by real events and situations, are used as a basis for a discussion of some of the most important potential sources of psychological bias in the context of understanding neurosurgical complications.

RESULTS

The issues of a) self-serving bias and the actor-observer effect; b) heuristics and biases in interpreting probabilistic events; c) emotional avoidance and denial; d) limitations of attention (dual systems theory) and e) errors of memory, are discussed.

CONCLUSION

There are a number of psychological factors, that are well known to science that may be ubiquitous sources of influence on the ability of neurosurgeons to grow by reflection on their own complications. Exactly how these factors can and should be efficiently adressed by the individual neurosurgeon and/or the organisation and team in which the neurosurgeon works may vary according to type of bias, context and circumstances. However, being aware of these issues and addressing them on an individual and organizational level remains important to the quality of our craft.

The supplementary motor area syndrome: a neurosurgical review

The supplementary motor area (SMA) syndrome is a frequently encountered clinical phenomenon associated with surgery of the dorsomedial prefrontal lobe. The region has a known motor sequencing function and the dominant pre-SMA specifically is associated with more complex language functions; the SMA is furthermore incorporated in the negative motor network. The SMA has a rich interconnectivity with other cortical regions and subcortical structures using the frontal aslant tract (FAT) and the frontostriatal tract (FST). The development of the SMA syndrome is positively correlated with the extent of resection of the SMA region, especially its medial side. This may be due to interruption of the nearby callosal association fibres as the contralateral SMA has a particular important function in brain plasticity after SMA surgery. The syndrome is characterized by a profound decrease in interhemispheric connectivity of the motor network hubs. Clinical improvement is related to increasing connectivity between the contralateral SMA region and the ipsilateral motor hubs. Overall, most patients know a full recovery of the SMA syndrome, however a minority of patients might continue to suffer from mild motor and speech dysfunction. Rarely, no recovery of neurological function after SMA region resection is reported.