Assessment of quantitative corticospinal tract diffusion changes in patients affected by subcortical gliomas using common available navigation software.

OBJECTIVE: The aim of this study is to analyze the quantitative DTI parameters of the CST in patients suffering from subcortical gliomas affecting the CST using generally available navigation software. METHODS: A retrospective study was conducted on 22 subjects with diagnosis of primary cerebral glioma and preoperative motor deficits. Exclusion criteria were: involvement of motor cortex, lesion involving both hemispheres, previous surgical treatment. All patients were studied using magnetic resonance imaging (MRI) with diffusion tensor imaging (DTI) sequences. Volume, fractional anisotropy (FA) and mean diffusivity value (MD) of the entire CSTs were estimated. Moreover, distance from midline, diameters, FA and MD were calculated on axial images at the point of minimal distance between tumor and CST. Statistical analysis was performed. RESULTS: There was a statistically significant difference of CST volume between affected and non-affected hemispheres (p<0.01). Mean overall/local FA, overall/local MD and sagittal diameter of CST were also significantly different between the two sides (p<0.05). Correlation tests resulted positive between the shift of CST and overall/local MD. Moreover there is significance between CST volume of tumor hemisphere and preoperative duration of motor deficits (p<0.05). CONCLUSION: The present study has demonstrated for the first time a significant difference of DTI based quantitative parameters of the CST between a tumor affected and a non-affected hemisphere in patients with a corresponding motor deficit. This preliminary data suggests a correlation between DTI based integrity of CST and its function.

Role of diffusion tensor imaging or magnetic resonance spectroscopy in the diagnosis and disability assessment of amyotrophic lateral sclerosis.

OBJECTIVE: To compare the results of magnetic resonance spectroscopy (MRS) and diffusion tensor imaging (DTI) in amyotrophic lateral sclerosis (ALS) patients. METHODS: Nineteen ALS patients and thirteen age-matched healthy controls underwent MRS and DTI between October 2013 and July 2014. Fractional anisotropy (FA), apparent diffusion coefficient (ADC), N-acetylaspartate (NAA), choline (Cho), and creatine (Cr) were collected as the quantitative results of the imaging study. The ALS functional rating scale-revised (ALSFRS-R) and disease progression rate were evaluated to assess patients' disability. The imaging study results were compared between ALS patients and healthy controls. The relationship between disability assessment and imaging study results was analyzed. RESULTS: NAA/Cr in the motor cortex and FA in the corticospinal tract (CST) of both sides were significantly lower in patients than controls. There was no significant difference between the two groups in Cho/Cr, tract length, tract volume, ADC or NAA. No relationship was found between ALSFRS-R and FA (r=0.243, p=0.316) in the right CST; NAA (r=0.095, p=0.699) or NAA/Cr (r=0.172, p=0.481) in the left motor cortex; or NAA (r=0.320, p=0.182) or NAA/Cr (r=0.193, p=0.492) in the right motor cortex. There was no relationship between the disease progression rate and FA, NAA, or NAA/Cr on either side. CONCLUSION: NAA/Cr and FA can help diagnose ALS. Regional brain NAA/Cr and FA values could not assess the ALSFRS-R or disease progression rate.

Multimodal assessment of primary motor cortex integrity following sport concussion in asymptomatic athletes.

OBJECTIVE: Recent studies have shown, in asymptomatic concussed athletes, metabolic disruption in the primary motor cortex (M1) and abnormal intracortical inhibition lasting for more than six months. The present study aims to assess if these neurochemical and neurophysiological alterations are persistent and linked to M1 cortical thickness. METHODS: Sixteen active football players who sustained their last concussion, on average, three years prior to testing and 14 active football players who never sustained a concussion were recruited for a single session of proton magnetic resonance spectroscopy ((1)H-MRS) and transcranial magnetic stimulation (TMS). Measures of M1 and whole brain cortical thickness were acquired, and (1)H-MRS data were acquired from left M1 using a MEGA-PRESS sequence. Cortical silent period (CSP) and long-interval intracortical inhibition (LICI) were measured with TMS applied over left M1. RESULTS: No significant group differences were observed for metabolic concentrations, TMS measures, and cortical thickness. However, whereas GABA and glutamate levels were positively correlated in control athletes, this relationship was absent in concussed athletes. CONCLUSION: These data suggest the general absence of neurophysiologic, neurometabolic and neuroanatomical disruptions in M1 three years following the last concussive event. However, correlational analyses suggest the presence of a slight metabolic imbalance between GABA and glutamate concentrations in the primary motor cortex of concussed athletes. SIGNIFICANCE: The present study highlights the importance of multimodal assesments of the impacts of sport concussions.

Practical assessment of preoperative functional mapping techniques: navigated transcranial magnetic stimulation and functional magnetic resonance imaging.

Preoperative brain mapping is vital to improve the outcome of patients with tumors located in eloquent areas. While functional magnetic resonance imaging (fMRI) remains the most commonly used preoperative mapping technique, navigated transcranial magnetic stimulation (nTMS) has recently been proposed as a new preoperative method for the clinical and surgical management of such patients. This study aims at evaluating the impact of nTMS as a routine examination and its ultimate contribution to patient outcome. We performed a preliminary prospective study on eight patients harboring a cerebral lesion in eloquent motor areas. Each patient underwent preoperative cortical brain mapping via both fMRI and nTMS; then, we assessed the reliability of both methods by comparing them with intraoperative mapping by direct cortical stimulation (DCS). This study suggests that nTMS was more accurate than fMRI in detecting the true cortical motor area when compared with DCS data, with a mean of deviation ± confidence interval (CI) of 8.47 ± 4.6 mm between nTMS and DCS and of 12.9 ± 5.7 mm between fMRI and DCS (p < 0.05). The results indicated that within the limits of our statistical sample, nTMS was found to be a useful, reliable, and non-invasive option for preoperative planning as well as for the identification of the motor strip; in addition, it usually has short processing times and is very well tolerated by patients, thereby increasing their compliance and possibly improving surgical outcome.

Dynamic NAD(P)H post-synaptic autofluorescence signals for the assessment of mitochondrial function in a neurodegenerative disease: monitoring the primary motor cortex of G93A mice, an amyotrophic lateral sclerosis model.

Abnormal mitochondrial function was reported in patients and models for amyotrophic lateral sclerosis (ALS). It is therefore important to set up sensitive tools for the monitoring of active agents that enhance energy metabolism delay onset, and extend lifespan of transgenic G93A-SOD1 ALS mice. In this report, primary motor cortex slices from G93A mice at different stages of disease were studied, using NAD(P)H autofluorescence post-synaptic signals following ultraviolet stimuli, as a probe to evaluate mitochondrial function. We observed consistent age-related alterations of responses in G93A primary motor cortex slices versus controls. We conclude that NAD(P)H autofluorescence post-synaptic signal is a highly sensitive real-time technique to detect mitochondrial function failure in primary cortex from living tissues.

Resolving crossings in the corticospinal tract by two-tensor streamline tractography: Method and clinical assessment using fMRI.

An inherent drawback of the traditional diffusion tensor model is its limited ability to provide detailed information about multidirectional fiber architecture within a voxel. This leads to erroneous fiber tractography results in locations where fiber bundles cross each other. This may lead to the inability to visualize clinically important tracts such as the lateral projections of the corticospinal tract. In this report, we present a deterministic two-tensor eXtended Streamline Tractography (XST) technique, which successfully traces through regions of crossing fibers. We evaluated the method on simulated and in vivo human brain data, comparing the results with the traditional single-tensor and with a probabilistic tractography technique. By tracing the corticospinal tract and correlating with fMRI-determined motor cortex in both healthy subjects and patients with brain tumors, we demonstrate that two-tensor deterministic streamline tractography can accurately identify fiber bundles consistent with anatomy and previously not detected by conventional single-tensor tractography. When compared to the dense connectivity maps generated by probabilistic tractography, the method is computationally efficient and generates discrete geometric pathways that are simple to visualize and clinically useful. Detection of crossing white matter pathways can improve neurosurgical visualization of functionally relevant white matter areas.

Diffusion tensor imaging for the assessment of upper motor neuron integrity in ALS.

BACKGROUND: High angular resolution diffusion tensor imaging (HARD) is an MRI technique that exploits the mobility of water molecules to yield maps of structural order and directionality of white matter tracts with greater precision than six-direction diffusion tensor imaging (DTI) schemes. OBJECTIVE: To assess whether HARD is more sensitive than conventional MRI or neurologic assessment in detecting the upper motor neuron (UMN) pathology of patients with ALS. METHODS: Twenty-five patients with definite UMN clinical signs and 23 healthy volunteers underwent conventional MRI. HARD datasets were collected from a subset of these participants plus four patients with isolated lower motor neuron (LMN) signs. ALS symptom severity was assessed by a neurologist, the conventional MR images were reviewed by neuroradiologists, and the DTI maps were subject to quantitative region of interest analysis. RESULTS: Motor cortex hypointensity on T2-weighted images and corona radiata hyperintensity on proton density-weighted images distinguished patients with UMN involvement from volunteers with 100% specificity, but only 20% sensitivity. Fractional anisotropy (FA) was reduced in the posterior limb of the internal capsule in patients with UMN involvement compared to volunteers. A FA threshold value with a sensitivity of 95% to detect patients with ALS (including those with isolated LMN signs) had a specificity of 71%. CONCLUSIONS: High angular resolution diffusion tensor imaging may be more sensitive than conventional MRI or neurologic assessment to the upper motor neuron (UMN) pathology of ALS, but it lacks the specificity required of a diagnostic marker. Instead, it is potentially useful as a quantitative tool for monitoring the progression of UMN pathology.

Preoperative assessment of motor cortex and pyramidal tracts in central cavernoma employing functional and diffusion-weighted magnetic resonance imaging.

BACKGROUND: Functional MRI (fMRI) combines anatomic with functional information and has therefore been widely used for preoperative planning of patients with mass lesions affecting functionally important brain regions. However, the courses of functionally important fiber tracts are not visualized. We therefore propose to combine fMRI with diffusion-weighted MRI (DWI) that allows visualization of large fiber tracts and to implement this data in a neuronavigation system. METHODS: DWI was successfully performed at a field strength of 1.5 Tesla, employing a spin-echo sequence with gradient sensitivity in six noncollinear directions to visualize the course of the pyramidal tracts, and was combined with echo-planar T2* fMRI during a hand motor task in a patient with central cavernoma. RESULTS: Fusion of both data sets allowed visualization of the displacement of both the primary sensorimotor area (M1) and its large descending fiber tracts. Intraoperatively, these data were used to aid in neuronavigation. Confirmation was obtained by intraoperative electrical stimulation. Postoperative MRI revealed an undisrupted pyramidal tract in the neurologically intact patient. CONCLUSION: The combination of fMRI with DWI allows for assessment of functionally important cortical areas and additional visualization of large fiber tracts. Information about the orientation of fiber tracts in normal appearing white matter in patients with tumors within the cortical motor system cannot be obtained by other functional or conventional imaging methods and is vital for reducing operative morbidity as the information about functional cortex. This technique might, therefore, have the prospect of guiding neurosurgical interventions, especially when linked to a neuronavigation system.

[Functional magnetic resonance imaging in the assessment of motor centers in patients with brain tumors in motor area]. / Czynnosciowy rezonans magnetyczny (cMR) w ocenie osrodków ruchowych u chorych z guzami mózgu tej okolicy.

Magnetic resonance imaging (MRI) is become recognised as the most sensitive and specific imaging modality for the examination of central nervous system pathology. Blood oxygen level-dependent (BOLD) contrast imaging is a non-invasive functional MRI technique for localising active neuronal brain centres. The aim of our study was to determine usefulness of fMRI in detecting hand movements cortical activity in hemisphere with brain tumour and comparison with corresponding one. Six right-handed patients with brain tumours of central sulcus area, aged 20-50 years were examined using a commercial 1.5 T scanner. All patients underwent both conventional and functional magnetic resonance imaging (MRI) examinations. Simple hand movements were examined separately for right and left hand at a self-paced rate. Significant increase of signal intensity was found in: a) contralateral primary motor cortex in all cases during both motor tasks, b) ipsilateral primary motor cortex, supplementary motor cortex and premotor cortex of both hemispheres in a part of the cases c) displacement of the activity in the affected hemisphere in comparison to the opposite one was noticeable depending on the localisation and size of the tumour and accompanied oedema. Usefulness of functional MRI in detecting primary motor area in patients with brain tumours was proved. There is a difference between activation in affected cortex and corresponding normal cortex in the opposite hemisphere.

Assessment of corticodiaphragmatic pathway and pulmonary function in acute ischemic stroke patients.

The aims of this study were to investigate the effect of stroke on the corticodiaphragmatic pathway and to clarify the relationships between neurophysiological data and degree of motor disability, site of infarction in CT scan, diaphragmatic excursion, blood gases and pulmonary function in stroke patients. The corticodiaphragmatic pathway was assessed using magnetic stimulation of the scalp sites and cervical roots. The study included 34 sequentially selected patients out of 250 patients with acute ischemic stroke. Twenty-five (age and sex matched) volunteers served as controls. Sixteen patients had cortical infarction, thirteen had subcortical infarction and five had both cortical and subcortical infarction. The mean Scandinavian Stroke Scale was 32.2. Decreased diaphragmatic excursion was observed in 41% of the patients. Twenty-four patients (70.5%) had abnormal magnetic evoked potentials (MEPs) of the affected hemisphere. In five patients MEPs were unelicitable from the affected hemisphere. The remaining nineteen patients had abnormal values of both cortical latency and central conduction time (CCT). Cortical latency, CCT, amplitude of compound muscle action potentials (CMAPs) and excitability threshold of the affected hemisphere were significantly altered compared to both the unaffected hemisphere and the control group. The patients with hemiplegia had a greater degree of hypoxia, hypocapnia and decreased serum bicarbonate level compared to the control group. Additionally, hemiplegic patients had a different degree of respiratory dysfunction. A statistically significant association was found between neurophysiological data and disability score, diaphragmatic excursion, site of infarction in CT scan and degree of respiratory dysfunction. Central diaphragmatic impairment may occur in acute stroke and could contribute to the occurrence of hypoxia in those patients.

Preoperative PET activation for assessment of motor cortex area in precentral chondroma.

BACKGROUND: A main problem in the preoperative planning for precentral tumors is the exact assessment of the spatial relationship between the tumor and the functionally relevant brain areas, which may be difficult using only morphologically oriented imaging (CT, MRI). Therefore, we applied motor activation PET and PET/MRI overlay in a patient with a precentral tumor. DESCRIPTION: We report the case of a 21-year-old woman suffering from progressive right-sided headache and intermittent dysesthesia of the left leg. MRI showed a hypointense tumor with inhomogenous contrast enhancement in the right precentral area. For preoperative assessment of the spatial relationship between the tumor and the motor cortex area, the patient underwent two F-18-fluorodeoxyglucose positron emission tomography (PET) scans (1. resting condition and 2. motor activation of the left leg) and subsequent calculation of subtraction images of activation minus rest. Fusion of PET and MRI data (PET/MRI overlay) was performed for bimodal function and morphology presentation. PET revealed an activation pattern behind and below the tumor, indicating that the motor cortex area was shifted to the back. PET findings were confirmed by intraoperative electrophysiology. Cortical stimulation combined with intraoperative neuronavigation localized the motor area of the left foot and leg exactly at the dorsal border, below and lateral to the lesion. After complete resection of the solid tumor, histopathological examination revealed a chondroma. The postoperative course was uneventful, and the patient was discharged without neurological deficits. CONCLUSIONS: This case shows that biomodal imaging (PET/MRI) provides a noninvasive exact assessment of functionally important cortex areas for preoperative planning in patients with cerebral lesions.

Assessment of upper and lower motor neurons in Kennedy's disease: implications for corticomotoneuronal PSTH studies.

We used peristimulus time histograms (PSTHs) to estimate characteristics of the composite excitatory postsynaptic potentials (EPSPs) generated at the anterior horn cell by a descending cortical volley induced by subthreshold transcranial magnetic stimuli in 11 normal subjects, 9 patients with DNA-confirmed Kennedy's disease, and 10 patients with amyotrophic lateral sclerosis (ALS). In Kennedy's disease the mean of the estimated EPSP amplitude (3.5 +/- 1.6 mV), as well as the means of duration (4.1 +/- 1.3 ms) and onset latency (20.4 +/- 2.7 ms) of the primary peak of 35 different motor units were not significantly different from normal subjects, in whom corresponding values of 49 motor units measured 2.9 +/- 1.6 mV (EPSP amplitude), 3.5 +/- 1.4 ms (duration) and 19.3 +/- 2.8 ms (onset latency). In 48 motor units of patients with ALS the mean of the estimated EPSP amplitude, duration, and latency measured 2.7 +/- 1.8 mV, 7.8 +/- 5.7 ms, and 24.0 +/- 6.5 ms, respectively, differing significantly from normal subjects and patients with Kennedy's disease. The normal cortically induced EPSP in Kennedy's disease is very different from the range of EPSP abnormalities in ALS, indicating that lower motor neuron disease per se does not result in an abnormal cortically induced EPSP derived from PSTHs. The normal findings in Kennedy's disease support our previous suggestions that the EPSP abnormalities in ALS are supraspinal in origin.

Comparative assessment of sensorimotor function using functional magnetic resonance imaging and electrophysiological methods.

Accurate assessment of the location of the sensorimotor cortex is important in presurgical investigation of and planning for patients with lesions impinging on this region. In this review, the relationship between the assessment of sensorimotor cortex by invasive electrophysiological mapping and functional magnetic resonance imaging (fMRI) is discussed. A number of areas are covered: (a) brief backgrounds of MRI and fMRI are provided, (b) existing fMRI literature of sensorimotor cortex activation is surveyed, (c) results of fMRI sensorimotor studies and intracranial somatosensory evoked potential (SEP) recordings and cortical stimulation in neurosurgical patients are compared, and (d) the locus of fMRI activation is discussed in the light of cortical generators of SEP components.