Beyond eloquence and onto centrality: a new paradigm in planning supratentorial neurosurgery

PURPOSE

Minimizing post-operational neurological deficits as a result of brain surgery has been one of the most pertinent endeavours of neurosurgical research. Studies have utilised fMRIs, EEGs and MEGs in order to delineate and establish eloquent areas, however, these methods have not been utilized by the wider neurosurgical community due to a lack of clinical endpoints. We sought to ascertain if there is a correlation between graph theory metrics and the neurosurgical notion of eloquent brain regions. We also wanted to establish which graph theory based nodal centrality measure performs the best in predicting eloquent areas.

METHODS

We obtained diffusion neuroimaging data from the Human Connectome Project (HCP) and applied a parcellation scheme to it. This enabled us to construct a weighted adjacency matrix which we then analysed. Our analysis looked at the correlation between PageRank centrality and eloquent areas. We then compared PageRank centrality to eigenvector centrality and degree centrality to see what the best measure of empirical neurosurgical eloquence was.

RESULTS

Areas that are considered neurosurgically eloquent tended to be predicted by high PageRank centrality. By using summary scores for the three nodal centrality measures we found that PageRank centrality best correlated to empirical neurosurgical eloquence.

CONCLUSION

The notion of eloquent areas is important to neurosurgery and graph theory provides a mathematical framework to predict these areas. PageRank centrality is able to consistently find areas that we consider eloquent. It is able to do so better than eigenvector and degree central measures.

Neurochemical supplementation in patients with depressed levels of participation after brain tumor surgery: Rationale and preliminary results

A unique challenge in some brain tumor patients is the fact that tumors arising in certain areas of the brain involve the neural structures of consciousness or alertness, limiting the patient's ability to participate in rehabilitation following surgery. A critical question is whether neurostimulant therapy can help patients participate in rehabilitation efforts. We performed a retrospective review of all patients undergoing brain tumor surgery by the senior author from 2012 to 2018. We limited this study to patients with tumors occupying critical structures related to consciousness, alertness, and motor initiation. A combination of methylphenidate and levodopa/carbidopa was used to monitor the progress of patients through neurorehabilitation efforts. We identified 101 patients who experienced an inability to participate in rehabilitation (ITPR) in the post-operative period. Of these, 86 patients (85%) were treated with methylphenidate and levodopa/carbidopa. Cases of ITPR were related to dysfunction of the brainstem (12/86 cases, 14%), thalamus (17/86 cases, 20%), hypothalamus (14/86 cases, 16%), basal ganglia (13/86 cases, 15%), and medial frontal lobe (30/86 cases, 35%). Of the 86 individuals treated, 47/86 patients (55%) showed early improvement in their ability to participate with rehabilitation. At three month follow-up, 58/86 patients (67%) had returned to living independently or were at least interactive and cooperative during follow-up examination. This feasibility report suggests that combined therapy with methylphenidate and levodopa/carbidopa may help patients participate in neurorehabilitation efforts in the immediate post-operative period following brain tumor surgery. Randomized, controlled clinical trials are needed to explore this concept more thoroughly.

Ethyl pyruvate diminishes the inflammatory response to lipopolysaccharide infusion in horses

REASONS FOR PERFORMING THE STUDY

Endotoxaemia contributes to morbidity and mortality in horses with colic due to inflammatory cascade activation. Effective therapeutic interventions are limited for these horses. Ethyl pyruvate (EP), an anti-inflammatory agent that alters the expression of proinflammatory cytokines, improved survival and organ function in sepsis and gastrointestinal injury in rodents and swine. Therapeutic efficacy of EP is unknown in endotoxaemic horses.

OBJECTIVES

Determine the effects of EP on signs of endotoxaemia and expression of proinflammatory cytokines following administration of lipopolysaccharide (LPS) in horses.

METHODS

Horses received 30 ng/kg bwt LPS in saline to induce signs of endotoxaemia. Next, horses received lactated Ringer's solution (LRS), (n = 6), 150 mg/kg bwt EP in LRS, (n = 6), or 1.1 mg/kg bwt flunixin meglumine (FM), (n = 6). Controls received saline followed by LRS (n = 6). Physical examinations, behaviour pain scores and blood for clinical pathological testing and gene expression were obtained at predetermined intervals for 24 h.

RESULTS

Lipopolysaccharide infusion produced clinical and clinicopathological signs of endotoxaemia and increased expression of tumour necrosis factor alpha (TNFα), interleukin 6 (IL-6) and IL-8 (P<0.001) compared with controls. Leucopenia and neutropenia occurred in all horses that received LPS. Horses treated with EP and FM had significantly (P<0.0001) reduced pain scores compared with horses receiving LPS followed by LRS. Flunixin meglumine was significantly more effective at ameliorating fever compared with EP. Both EP and FM significantly diminished TNFα expression. Ethyl pyruvate significantly decreased, but FM significantly increased, IL-6 expression. Neither EP nor FM altered IL-8 expression.

CONCLUSIONS AND POTENTIAL RELEVANCE

Ethyl pyruvate administered following LPS diminished the clinical effects of endotoxaemia and decreased proinflammatory gene expression in horses. Ethyl pyruvate suppressed expression of proinflammatory cytokines better than FM. However, FM was a superior anti-pyretic compared with EP. Ethyl pyruvate may have therapeutic applications in endotoxaemic horses.

Striking changes in the structure and organization of rat fetal membranes precede parturition

Premature rupture of fetal membranes can harm infant and mother. It is unclear whether structural changes predispose these membranes to breaking. We thus assessed rat visceral yolk sac placenta (VYSP) and amnion by light and by transmission electron microscopy on Days 18-21 of gestation. Light microscope sections were stained for connective tissue (extracellular matrix) components: collagen, glycoprotein, and glycosaminoglycans/proteoglycans. Some tissue was incubated with chondroitinase ABC. We observed that fetal membranes became increasingly fragile, rupturing readily on Day 21. On Days 18-20, the two epithelial layers of the capsular VYSP were separated by a well-developed, well-vascularized connective tissue layer that stained intensely for all matrix components studied; on Day 21, the connective tissue layer was thinner, moderately stained, and less vascularized. On Days 18-20, the two cellular layers of the amnion were separated by a narrow, compact connective tissue layer that stained modestly for all matrix components; on Day 21, this area was widened and stained faintly. Transmission electron microscopy showed that collagen fibrils of the amnion were abundant, closely packed, and well organized on Days 18-20, whereas on Day 21 they were few in number, widely spaced, and disorganized. Similar changes were present after incubation with chondroitinase ABC. In addition, amniotic epithelial cells were moribund and delaminating, basal laminae were deteriorating or absent, and few cells were at the outer surface of the amnion. All changes preceded parturition. We conclude that the structural integrity of rat fetal membranes is impaired before birth through the loss of connective tissue components and cells, changes that presumably underlie membrane rupture. Lastly, the similarity of structural changes in rat and human fetal membranes point to the potential usefulness of the rat model.