[The comparison of the external and internal standards using 1HMRS method in diagnostics of brain tumours]. / Porównanie przydatnosci wzorców zewnetrznego i wewnetrznego w diagnostyce HMRS guzów mózgowia.

The aim of the study was the comparison of usefulness of the external and internal standards using 1HMRS method in diagnostics of brain tumors. The study was performed using MRI Signa Excite 1.5T system with SVS and PRESS technique (TR=1500ms, TE=35ms) and covered 100 patients with brain tumors (low and high grade of malignancy). The concentration of metabolites from voxels located in contralateral unchanged cerebral tissue was analyzed. Additionally 30 healthy volunteers were examined (the external model). Comparison of external and internal models showed lack of statistically considerable differences for all analyzed metabolites except the mi concentration. In case of Cho, Cr, Lac, Lip, GIx concentration, it was noticed that in group of patients with brain tumors mean values were slightly (insignificantly) increased in comparison to external model. In case of NAA concentration, an opposite relation was stated. Comparing group of patients with high grade of malignancy, to patients with low grade of malignancy slightly increased values of all metabolites was observed. In group of patients with high grade of malignancy, statistically significant high ml concentration was observed compared to patients with low grade of malignancy. In group of patients with low grade of malignancy, statistically significant low mean values of ml concentration was observed, compared to external control group. As referential values it is possible to use results of all analyzed metabolites (NAA, Cho, Cr, Lip, Lac, Ala, GIx) except ml interchangeably for the external and internal standards.

Brain correlates of right-handedness.

Recent development of neuroimaging techniques has opened new possibilities for the study of the relation between handedness and the brain functional architecture. Here we report fMRI measurements of dominant and non-dominant hand movement representation in 12 right-handed subjects using block design. We measured possible asymmetry in the total volume of activated neural tissue in the two hemispheres during simple and complex finger movements performed either with the right hand or with the left hand. Simple movements consisted in contraction/extension of the index finger and complex movements in successive finger-thumb opposition from little finger to index finger. A general predominance of left-hemisphere activation relative to right hemisphere activation was found. Increasing the complexity of the motor activity resulted in an enlargement of the volume of consistently activated areas and greater involvement of ipsilateral areas, especially in the left hemisphere. Movements of the dominant hand elicited large contralateral activation (larger than movements of the non-dominant hand) and relatively smaller ipsilateral activation. Movements of the non-dominant hand resulted in a more balanced pattern of activation in the two hemispheres, due to relatively greater ipsilateral activation. This suggests that the dominant (right) hand is controlled mainly by the contralateral (left) hemisphere, whereas the nondominant hand is controlled by both left and right hemispheres. This effect is especially apparent during execution of complex movements. The expansion of brain areas involved in motor control in the hemisphere contralateral to the dominant hand may provide neural substrate for higher efficiency and a greater motor skill repertoire of the preferred hand.

Single voxel proton magnetic resonance spectroscopy in post-stroke depression.

Mood disorders are associated with structural, metabolic and spectroscopic changes in prefrontal regions. In the case of depression associated with stroke, there is little information about the biochemical profile of these regions, as assessed by proton magnetic resonance spectroscopy ((1)H-MRS). In a group of first-ever stroke patients, we studied the association between post-stroke depression and (1)H-MRS measurements in unaffected frontal lobes. Twenty-six patients with a first ischemic stroke located outside the frontal lobes were included in the study. Single voxel proton magnetic resonance spectroscopy ((1)H-MRS) was performed to assess N-acetylaspartate/creatine (NAA)/Cr, glutamate+glutamine (Glx)/Cr, choline (Cho)/Cr and myo-inositol (mI)/Cr ratios. Patients were assessed within the first 10 days after stroke and again four months later. The diagnosis of depression was made on the basis of clinical observation, interview and Hamilton Depression Rating Scale scores. In a group of 26 patients, eight (31%) met criteria for depression at the first assessment, and nine (35%) met criteria for depression at follow-up. Patients with depression in the immediate post-stroke phase had significantly higher Glx/Cr ratios in the contralesional hemisphere than non-depressive patients. No biochemical differences were found between the groups at 4-month follow-up. These findings suggest that post-stroke depression is accompanied by changes in frontal lobe glutamate/glutamine levels, perhaps reflecting abnormalities in glutamatergic transmission in the immediate post-stroke period.

Reduced prefrontal N-acetylaspartate in stroke patients with apathy.

BACKGROUND: Although substantial numbers of stroke patients suffer from apathy, its causes are still poorly understood. Previous studies suggest that dysfunction of the frontal lobes is implicated in the pathophysiology of motivation. Our aim was to investigate the association between proton magnetic resonance spectroscopy (H1-MRS) measurements in unaffected frontal lobes and apathy in a group of first-time stroke patients. METHODS: 31 patients with a first-time ischemic stroke located outside the frontal lobes and 20 healthy subjects were included in the study. The authors performed single voxel H1-MRS in order to measure the N-acetylaspartate/creatine (NAA)/Cr, glutamate+glutamine (Glx)/Cr, choline (Cho)/Cr and myo-inositol (mI)/Cr ratios in the frontal lobes. Patients were assessed between days 7 and 12 post stroke. Diagnosis of apathy was made on the basis of clinical observation, interview and Apathy Scale. RESULTS: 13 out of 31 patients (42%) demonstrated apathy. Patients with apathy had lower NAA/Cr ratios in the right frontal lobe than non-apathetic subjects. The patient group was divided into two subgroups: Those with left hemisphere strokes, and those with right hemisphere strokes. Of these subjects, significantly lowered NAA/Cr ratios were found in the right hemispheres of apathetic patients in the subgroup with left-sided brain lesions. CONCLUSIONS: These findings point to the association between apathy and frontal lobe integrity, suggest different reactions of the hemispheres and indicate that changes in the NAA/Cr ratio are related to the apathy.

GABA in ischemic stroke. Proton magnetic resonance study.

BACKGROUND: Experimental studies have suggested that ischemic stroke causes increment in extracellular level of gamma-aminobutyric acid in response to excessive glutamate concentration and function. The increased GABA concentration is followed by subsequent inhibition of GABA synthesis, thus leading to GABA-ergic dysfunction Enhancing GABA function seems to be a way of neuroprotec- tion after cerebral insult. Animal models have shown there is overactivity of excitatory neurotransmitters and decreased tone of GABA-ergic system also in the remote neocortical regions. Data concerning changes in brain areas outside the stroke lesion in humans are sparse. These region could be possible targets for therapeutic intervention. Progress in imaging techniques enables separation of a great number of chemical compounds .Our aim was to assess GABA levels outside the ischemic lesion by means of proton magnetic resonance spectroscopy ((1) H MRS). MATERIAL AND METHODS: The study compared 31 patients with first-ever ischemic stroke and 20 healthy subjects. Single voxel H(1) MRS was performed to measure GABA/Cr ratios in structurally normal prefrontal regions, distant from the stroke lesion. The amount of the remaining metabolites (NAA, Cho, mI, Glx) was also estimated. Patients underwent the examination in the acute phase of the disease and 3 months later. RESULTS: Both early after stroke and more than 3 months later, the patients had lower GABA levels. However, during the second examination, this difference was evident only in the frontal cortex ipsilateral to the lesion. CONCLUSIONS: These findings suggest that GABA function is decreased outside the infarct. Further studies are needed for confirmation of the results and elucidation of the possible role of GABA alterations in stroke recovery and therapy.

Central control of heart rate changes during visual affective processing as revealed by fMRI.

In the present study we addressed the question of central control of heart rate (HR) in emotions. Parallel measurement of HR changes and changes of local intensity of blood flow as indexed by fMRI in a procedure eliciting emotions allowed us to pinpoint areas of the brain responsible for HR variations during emotional arousal. In condition eliciting positive emotions we detected activation of occipito-temporal regions, anterior insula, and hypothalamus. In condition eliciting negative emotions we also detected activation of occipito-temporal regions and additionally activation of bilateral anterior insulae, right amygdala and right superior temporal gyrus. The results show that structures constituting neural network involved in HR control during emotional arousal are affect specific. Particularly the central circuit controlling HR in negative affect includes the amygdala, while central circuit controlling HR in positive affect includes the hypothalamus. Additionally activation of bilateral occipito-temporal cortex proves enhancement of visual processing of emotional material as compared to neutral material in both positive and negative affect. This might be attributed to top-down processes originating in the frontal lobe and related to shifting attention to the emotionally relevant stimuli. Activation of insular cortex is probably related to autonomic arousal accompanying watching emotional content (e.g. sweating, heart-rate changes etc.). Activation of the amygdala in the negative condition supports the well documented engagement of this structure in processing of fear and disgust.