Upper and Lower Limb Motor Function Correlates with Ipsilesional Corticospinal Tract and Red Nucleus Structural Integrity in Chronic Stroke: A Cross-Sectional, ROI-Based MRI Study

Background. Structural integrity of the ipsilesional corticospinal tract (CST) is important for upper limb motor recovery after stroke. However, additional neuromechanisms associated with motor function poststroke are less well understood, especially regarding the lower limb. Objective. To investigate the neural basis of upper/lower limb motor deficits poststroke by correlating measures of motor function with diffusion tensor imaging-derived indices of white matter integrity (fractional anisotropy (FA), mean diffusivity (MD)) in primary and secondary motor tracts/structures. Methods. Forty-three individuals with chronic stroke (time poststroke, 64.4 ± 58.8 months) underwent a comprehensive motor assessment and MRI scanning. Correlation and multiple regression analyses were performed to examine relationships between FA/MD in a priori motor tracts/structures and motor function. Results. FA in the ipsilesional CST and red nucleus (RN) was positively correlated with motor function of both the affected upper and lower limb ( r = 0.36 ‐ 0.55 , p ≤ 0.01 ), while only ipsilesional RN FA was associated with gait speed ( r = 0.50 ). Ipsilesional CST FA explained 37.3% of the variance in grip strength ( p < 0.001 ) and 31.5% of the variance in Arm Motricity Index ( p = 0.004 ). Measures of MD were not predictors of motor performance. Conclusions. Microstructural integrity of the ipsilesional CST is associated with both upper and lower limb motor function poststroke, but appears less important for gait speed. Integrity of the ipsilesional RN was also associated with motor performance, suggesting increased contributions from secondary motor areas may play a role in supporting chronic motor function and could become a target for interventions.

Bilateral Motor Responses to Transcranial Magnetic Stimulation in Preterm Children at 9 Years of Age

Objective This study was aimed to evaluate motor tracts integrity in nondisabled preterm-born (PT) children at 9 years of age. Methods Overall, 18 PT and 13 term-born (T) children without motor disability were assessed by transcranial magnetic stimulation (TMS). Motor-evoked potentials (MEPs) were measured bilaterally from the abductor pollicis brevis (APB) and the tibialis anterior (TA) muscles. Muscle responses could be stimulated from all patients. Results Overall, 83.3 and 23.1% of PT and T children, respectively, had mild clumsiness (p = 0.001). One PT and three T children had immediate bilateral responses in the upper extremities. Seven PT children had delayed ipsilateral APB responses after left and ten after right TMS. Three controls had delayed ipsilateral responses. Ipsilateral lower extremity responses were seen in one PT after right and two PT children and one T child after left TMS. The results did not correlate to groups, genders, clumsiness, or handedness. Conclusion Children of PT and T may have bilateral motor responses after TMS at 9 years of age. Ipsilateral conduction emerges immediately or more often slightly delayed and more frequently in upper than in lower extremities. Significance Bilateral motor conduction reflects developmental and neurophysiological variability in children at 9 years of age. MEPs can be used as a measure of corticospinal tract integrity in PT children.

Abstract P380: Eloquence Mapping in Acute Ischaemic Stroke

Introduction: Patient selection for acute stroke revascularisation therapies is commonly based on clinical-imaging mismatch paradigms. Anatomical scores or total volumes of brain affected are assumed to correlate with clinical deficit without reference to the functional eloquence of the regions involved. In this study we used the relationship between presenting hypoperfusion abnormality and the corresponding NIHSS to generate functionally weighted atlases from patients with acute ischaemic stroke. Methods: Patients with acute large vessel occlusion (LVO) of the anterior circulation and with CTP at the time of presentation were included in this study. CTP was analysed with e-CTP (Brainomix Ltd., Oxford, UK) and hypoperfusion maps defined (Tmax >6s). Voxelwise lesion to symptom mapping was used to generate probability maps associating regions of hypoperfusion with clinical deficit at presentation. Results: 58 patients with itemised NIHSS and CTP were included. Discrete patterns of deficit were associated with each NIHSS domain. Total NIHSS correlated most strongly with left MCA involvement, consistent with the weighting towards language in this clinical scale. Regions associated with upper and lower limb deficits identified the respective motor cortex regions and descending motor tracts. Example mapping is presented in the Figure (A: total NIHSS, B: left arm paresis, C: left leg paresis). Data from a larger cohort will be presented at the meeting. Conclusions: Functional mapping using associations between presenting NIHSS and hypoperfusion lesion can be used to create eloquence-weighted atlases. Such atlases from stroke patients may be helpful to develop tools to predict clinical deficit associated with a presenting ischemic core lesion defined on non-contrast CT or CTP. This approach could refine clinical-imaging mismatch concepts, expanding endovascular treatment to a wider group of patients who would not currently be treated.

Physiological alteration and anaesthetic drugs effects on intraoperative neurophysiological monitoring procedures

Intraoperative neurophysiological monitoring (IOM) and especially motor evoked potentials represents an important tool in the evaluation of the nervous system integrity and particularly of the motor tracts. A real and correct registration of the potentials with a proper interpretation of the modification is mandatory for an optimal outcome in eloquent areas, tumours, brainstem and medullary lesions. For all this to happen a suitable anaesthetic protocol must be used. Even though there is a large spectrum of anaesthetic agents at our disposal it is imperative to know their effect on the IOM signals recordings and the fact that some of them are dose-dependent. Drugs effects and physiological changes produced intraoperatively must be corrected before a shift in the direction of the surgical lesion resection it is taken. We present an overview of the action of the anaesthetic agents, most used protocols and the physiological alteration encountered in the operative theatre.

Segmented quantitative diffusion tensor imaging evaluation of acute traumatic cervical spinal cord injury

Objectives: To evaluate segmented diffusion tensor imaging (DTI) white matter tract fractional anisotropy (FA) and mean diffusivity (MD) values in acute cervical spinal cord injury (CSCI). Methods: 15 patients with acute CSCI and 12 control subjects were prospectively recruited and underwent axial DTI as part of the spine trauma MRI. Datasets were put through a semi-automated probabilistic segmentation algorithm that analyzed white matter, motor and sensory tracts. FA and MD values were calculated for white matter, sensory (spinal lemniscal) and motor tracts (ventral/lateral corticospinal) at the level of clinical injury, levels remote from injury and in normal controls. Results: There were significant differences in FA between the level of injury and controls for total white matter (0.65 ± .09 vs 0.68 ± .07; p = .044), motor tracts (0.64 ± .07 vs 0.7 ± .09; p = .006), and combined motor/sensory tracts (0.63 ± .09 vs 0.69 ± .08; p = .022). In addition, there were significant FA differences between the level of injury and one level caudal to the injury for combined motor tracts (0.64 ± .07 vs 0.69 ± .05; p = .002) and combined motor/sensory tracts (0.63 ± .09 vs 0.7 ± .07; p = .011). There were no significant differences for MD between the level of injury and one level caudal to the injury or normal controls. Conclusion: Abnormalities in DTI metrics of DTI-segmented white matter tracts were detected at the neurological level of injury relative to normal controls and levels remote from the injury site, confirming its value in CSCI assessment. Advances in knowledge: Segmented DTI analysis can help identify microstructural spinal cord abnormalities in the setting of traumatic cervical spinal cord injury.

Resection of tumors within the primary motor cortex using high-frequency stimulation: oncological and functional efficiency of this versatile approach based on clinical conditions

OBJECTIVEBrain mapping techniques allow one to effectively approach tumors involving the primary motor cortex (M1). Tumor resectability and maintenance of patient integrity depend on the ability to successfully identify motor tracts during resection by choosing the most appropriate neurophysiological paradigm for motor mapping. Mapping with a high-frequency (HF) stimulation technique has emerged as the most efficient tool to identify motor tracts because of its versatility in different clinical settings. At present, few data are available on the use of HF for removal of tumors predominantly involving M1.METHODSThe authors retrospectively analyzed a series of 102 patients with brain tumors within M1, by reviewing the use of HF as a guide. The neurophysiological protocols adopted during resections were described and correlated with patients’ clinical and tumor imaging features. Feasibility of mapping, extent of resection, and motor function assessment were used to evaluate the oncological and functional outcome to be correlated with the selected neurophysiological parameters used for guiding resection. The study aimed to define the most efficient protocol to guide resection for each clinical condition.RESULTSThe data confirmed HF as an efficient tool for guiding resection of M1 tumors, affording 85.3% complete resection and only 2% permanent morbidity. HF was highly versatile, adapting the stimulation paradigm and the probe to the clinical context. Three approaches were used. The first was a “standard approach” (HF “train of 5,” using a monopolar probe) applied in 51 patients with no motor deficit and seizure control, harboring a well-defined tumor, showing contrast enhancement in most cases, and reaching the M1 surface. Complete resection was achieved in 72.5%, and 2% had permanent morbidity. The second approach was an “increased train approach,” that is, an increase in the number of pulses (7–9) and of pulse duration, using a monopolar probe. This second approach was applied in 8 patients with a long clinical history, previous treatment (surgery, radiation therapy, chemotherapy), motor deficit at admission, poor seizure control, and mostly high-grade gliomas or metastases. Complete resection was achieved in 87.5% using this approach, along with 0% permanent morbidity. The final approach was a “reduced train approach,” which was the combined use of train of 2 or train of 1 pulses associated with the standard approach, using a monopolar or bipolar probe. This approach was used in 43 patients with a long clinical history and poorly controlled seizures, harboring tumors with irregular borders without contrast enhancement (low or lower grade), possibly not reaching the cortical surface. Complete resection was attained in 88.4%, and permanent morbidity was found in 2.3%.CONCLUSIONSResection of M1 tumors is feasible and safe. By adapting the stimulation paradigm and probe appropriately to the clinical context, the best resection and functional results can be achieved.

Brain Circuit Alterations and Cognitive Disability in Late-Onset Cobalamin D Disorder

Neuroimaging studies describing brain circuits’ alterations in cobalamin (vitamin B12)-deficient patients are limited and have not been carried out in patients with inborn errors of cobalamin metabolism. The objective of this study was to assess brain functionality and brain circuit alterations in a patient with an ultra-rare inborn error of cobalamin metabolism, methylmalonic aciduria, and homocystinuria due to cobalamin D disease, as compared with his twin sister as a healthy control (HC). We acquired magnetic resonance imaging (including structural, functional, and diffusion images) to calculate brain circuit abnormalities and combined these results with the scores after a comprehensive neuropsychological evaluation. As compared with HC, the patient had severe patterns of damage, such as a 254% increment of ventricular volume, pronounced subcortical and cortical atrophies (mainly at striatum, cingulate cortex, and precuneus), and connectivity alterations at fronto-striato-thalamic circuit, cerebellum, and corpus callosum. In agreement with brain circuit alterations, cognitive deficits existed in attention, executive function, inhibitory control, and mental flexibility. This is the first study that provides the clinical, genetic, neuroanatomical, neuropsychological, and psychosocial characterization of a patient with the cobalamin D disorder, showing functional alterations in central nervous system motor tracts, thalamus, cerebellum, and basal ganglia, that, as far as we know, have not been reported yet in vitamin B12-related disorders.