Sex-related asymmetries in the morphology of the left and right hippocampi?

Cell densities were determined in left and right surgically removed hippocampal tissue of epileptic patients. Pyramidal cells were studied in CA1, CA4, and the dentate gyrus. Lower densities of nucleolated cells were found for males in the right CA1 and CA4 than on the left while there was no significant left-right difference in females. Moreover, we found a probable sex difference in intercorrelations of nucleolated cells among the three subfields. In males, they were positive and significant on the left while they were low on the right. In females, positive significant intercorrelations were obtained between some subfields and not between other subfields, on either side. The present findings suggest greater hippocampal lateralization in males than in females with higher hippocampal neuronal connectivity on the left in males than on the right.     

Single-voxel proton spectroscopy using a press sequence with a 135 ms echotime: normal values

The clinical value of MR spectroscopy is now well established and this technique has been added to the current French classification of medical acts (CCAM). This paper presents a set of normal control values for 3 metabolite ratios obtained using a PRESS sequence with a TE of 135 ms at 1.5T: NAA/Cho, NAA/Cr and Cho/CR. Spectroscopy data acquisition were obtained from the following 12 anatomical regions: parieto-occipital white matter, centrum semiovale, frontal white matter, thalamus, basal ganglia, cerebellum (hemisphere, including dentate nucleus), brain stem (including pons, medulla and midbrain), anterior and posterior temporal lobe, parietal, occipital and pre-frontal cortices. The presented data allow radiologists equipped with a similar MR system to implement a clinical spectroscopy program without undergoing research protocols in order to obtain control values.     

Regional differentiation of cell densities in the left and right hippocampi of epileptic patients

Neuronal cell densities in surgically removed left or right hippocampal tissue of epileptic patients suffering from temporal lobe epilepsy were determined in CA1, CA4, and the dentate gyrus (DG). Mean densities showed no statistically significant left-right asymmetry in CA1 and the DG, consistent with findings by others. Mean densities did show previously unreported asymmetry in CA4; densities were significantly lower in the right CA4 than in the left. Another new finding is an asymmetry in regional intercorrelations: positive and significant correlations among the three subfields were obtained only in the left hippocampus. In addition, we confirmed previous findings of positive correlation between neuronal densities in CA1 and age of onset of habitual epilepsy, on either side. Taken together, the results suggest subtle left-right asymmetries in the vulnerability of the hippocampi to epilepsy-associated damage and/or higher neuronal connectivity or interdependence on the left than on the right.     

Indications for cerebral MR proton spectroscopy in 2007

Magnetic resonance spectroscopy (MRS) is being increasingly performed alongside the more conventional MRI sequences in the exploration of neurological disorders. It is however important to clearly differentiate its clinical applications aiming at improving the differential diagnosis or the prognostic evaluation of the patient, from the research protocols, when MRS can contribute to a better understanding of the pathophysiology of the disease or to the evaluation of new treatments. The most important applications in clinical practice are intracranial space occupying lesions (especially the positive diagnosis of intracranial abscesses and gliomatosis cerebri and the differential diagnosis between edema and tumor infiltration), alcoholic, hepatic, and HIV-related encephalopathies and the exploration of metabolic diseases. Among the research applications, MRS is widely used in multiple sclerosis, ischemia and brain injury, epilepsy and neuro degenerative diseases.     

Rasmussen's encephalitis: proton MR spectroscopy and diffusion MR findings

Rasmussen's encephalitis is a chronic inflammation of the brain that leads to progressive neurologic deficits. The condition has previously been studied by various imaging modalities including MR imaging and MR spectroscopy. We studied three patients presenting with Rasmussen's encephalitis by using proton MR spectroscopy, and diffusion-weighted MR imaging. In these patients, on diffusion-weighted MR imaging, mean apparent diffusion coefficient (ADC) value was 1.74 x 10(-3) mm(2)/sec within the parenchyma, apparently higher than that of the normal parenchyma (0.88 x 10(-3) mm(2)/sec) of a control group of five healthy subjects. Proton MR spectra were obtained with a TR value of 1,500 msec and differing TE values (135, 40, and 20 msec), and were compared with a control group of fourteen cases. In the affected regions of the brain, MR spectroscopy revealed decreased NAA, and increased Cho peaks associated with apparently decreased NAA/Cho, NAA/Cr ratios, and increased Cho/Cr ratios. Slightly increased mI peaks, and increased mI/NAA ratios were noted. A prominent lactate peak was noted in one of the patients.     

Cerebellar abnormalities on proton MR spectroscopy in gluten ataxia

Gluten sensitivity can manifest with ataxia. The metabolic status of the cerebellum was investigated in 15 patients with gluten ataxia and 10 controls using proton MR spectroscopy. Significant differences were present in mean N-acetyl aspartate levels at short echo time and N-acetyl aspartate/choline ratios at long echo time between the patient and control groups. These data support the hypothesis that cerebellar neuronal physiology differs between patients with gluten ataxia and healthy controls.     

MRI and proton MR spectroscopy in acute disseminated encephalomyelitis

Introduction Acute disseminated encephalomyelitis (ADEM) is one of a group of demyelinating disorders of the central nervous system (CNS). It is said to be attributed to an overshooting immunologic response following an infection or vaccination. The clinical course and type of manifestation is heterogeneous. The early application of corticosteroids has been shown to be beneficial to outcome; thus, an early diagnosis is highly desirable.Methods The potential diagnostic value of advanced MR techniques such as proton MR spectroscopy and diffusion-weighted imaging (DWI) was investigated in two paediatric patients with ADEM, one of whom had a remitting and relapsing clinical course and presented with additional cranial nerve involvement. Proton MR spectroscopy revealed typical signs of acute demyelination, such as increased macromolecules, not found in other forms of non-necrotising pathology.Conclusion The addition of proton MR spectroscopy and DWI adds to the diagnostic power of MRI in the setting of post-infectious demyelinating disorders of the CNS or ADEM and may obviate the need for biopsy.     

Pelizaeus-Merzbacher disease: diffusion MR imaging and proton MR spectroscopy findings

A 5-Year-old boy is reported with genetically confirmed Pelizaeus-Merzbacher disease. On chemical-shift spectroscopic imaging choline (Cho) peaks were prominently decreased in the white matter resulting in markedly high NAA/Cho ratios, and low Cho/Cr ratios, compared to five control cases. Low Cho levels could be indicative of the dysmyelinating disorder in the disease. On b=1000 s/mm(2) images of diffusion MRI, a tigroid pattern was evident, and there was no apparent signal abnormality. However, on ADC maps high signal and high ADC values were evident in the white matter ranging from 1.16 to 1.52 X 10(-3) mm(2)/s, compared to the ADC values of nine control cases, consistent with some disintegration of the white matter secondary to lack of myelination. On the other hand, the ADC values of the cortex were normal (0.79-0.95 X 10(- 3) mm(2)/s). These findings on spectroscopy and diffusion MRI likely represented deficient myelination in the disease.     

Antenatal proton MR spectroscopy of the human brain in vivo

Introduction The assessment of metabolites in the human fetal brain in utero could have diagnostic value. We explored the feasibility and potentials of proton magnetic resonance spectroscopy (¹H MRS) for this purpose.Results ¹H MRS was successfully performed in the third trimester of pregnancy without using sedation. Signals for inositol, choline, creatine, and N-acetylasparatate (NAA) compounds were detected in MR spectra from single voxels in the brain. Absolute tissue levels of these metabolites resemble values measured in preterm and term babies, especially of relatively more mature brain regions, from which most of the MR spectra have been obtained. Brain maturation between 30 and 41 weeks of gestation was most clearly reflected by increasing levels of the neuronal marker NAA.Conclusion With proper care for the methodological aspects, antenatal ¹H MRS clearly has the potential to evolve into a clinical tool for assessing a number of key metabolites in the human fetal brain in utero.     

The earliest MR imaging and proton MR spectroscopy abnormalities in adult-onset Krabbe disease

BACKGROUND: Adult-onset Krabbe disease is an uncommon form of leukodystrophy. Its magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) manifestations are not well documented. AIM OF THE STUDY: To describe early MR findings in adult-onset Krabbe disease. MATERIALS AND METHODS: A 28-year-old woman who had spastic paraparesis and a 5-year history of gait problems underwent MRI of the brain and cervical spine. Proton MRS was performed at 1.5 T using a short echo time. Metabolites were analyzed in the areas of MR signal abnormalities and normal-appearing brain. Six healthy volunteers were examined as controls. RESULTS: MRI revealed changes in the upper corticospinal tracts, splenium and, minimally, adjacent to the atria of the lateral ventricles. MRS showed decreased creatine, choline, N-acetylaspartate and glutamate and probably elevated lactate in the upper corticospinal tract but not in the normal-appearing frontal lobe. The spinal cord was thin. Laboratory tests verified Krabbe disease. CONCLUSIONS: These results indicate early involvement of the upper corticospinal tract in adult-onset Krabbe disease. The cases reported earlier had imaging changes indicating a more advanced disease or no MR findings. Thinning of the spinal cord is a new finding in Krabbe disease.     

Study of hypothalamic metabolism in cluster headache by proton MR spectroscopy

The authors used 1H-MRS to investigate hypothalamic metabolism in 26 patients with cluster headache (CH) and 12 healthy subjects. Hypothalamic N-acetylaspartate/creatine was reduced in patients with CH vs controls (p < 0.01). Dividing the patients into episodic CH outside- and in-cluster periods and chronic CH, the hypothalamic N-acetylaspartate/creatine in all three subgroups of patients was reduced. The reduction of the neuronal marker N-acetylaspartate is consistent with hypothalamic neuronal dysfunction in patients with CH.     

Guidelines for using proton MR spectroscopy in multicenter clinical MS studies

Proton MR spectroscopy (MRS) allows noninvasive characterization of chemical-pathologic changes in the brain. In patients with multiple sclerosis (MS), proton MRS reveals chemical pathology in focal inflammatory lesions as well as in regions of the brain that are not associated with structural abnormalities on conventional MRI. In MS studies, it has been particularly useful as a method for the assessment of neurodegeneration based on decreases in the levels of the neuro-axonal marker compound, N-acetylaspartate. Also, MRS has provided evidence of chemical pathology and repair involving non-neuronal brain cells based on changes in metabolites, including choline, myo-inositol, glutamate, and GABA. Despite its greater pathologic specificity for axonal integrity compared to conventional MRI, MRS has been used only infrequently in clinical trials. This prompted us to review current MRS clinical applications in MS, discuss the potential and limitations of the technique, and suggest recommendations for the application of MRS to clinical trials.     

In vivo temperature measurements in brain tumors using proton MR spectroscopy

The chemical shift difference between the water resonance and the methyl resonance of N-acetylaspartate was used to determine the in vivo temperature in 43 patients with histologically proven brain tumors. Temperatures were also estimated from the contralateral side in 15 of these patients. There was a significant difference (p < 0.05) ] in temperature between meningiomas and the other tumors viz. low grade astrocytomas, grade IV astrocytomas and oligoastrocytomas. Temperature was also significantly different between the contralateral side and the meningiomas (p < 0.05).     

Treatment monitoring and response prediction with proton MR spectroscopy in AD

In this proton magnetic resonance spectroscopy ((1)H-MRS) study, the authors correlated cognitive improvement after 3 months of treatment with donepezil with changes of N-acetylaspartate (NAA) level and NAA/Creatine (Cr) ratio in the medial temporal and parietal lobe of 17 patients with Alzheimer disease. Treatment response was associated with an increase of NAA and NAA/Cr in the parietal lobe. Low baseline NAA/Cr in the parietal lobe predicted positive treatment outcome.     

Neuropsychological patterns in right versus left frontotemporal dementia.

Patients with frontotemporal dementia (FTD) often present with an asymmetric left or right-sided anterior cerebral perfusion abnormality that is associated with differential behavioral symptoms. However, whether patients with primarily right versus left FTD also have unique neuropsychological characteristics has not been previously investigated. Comparisons of 11 patients with right-sided FTD and 11 with left FTD indicated that the 2 patient groups showed relatively distinct cognitive profiles. Patients with right FTD exhibited relatively worse performance on PIQ than VIQ, and on select nonverbal executive tasks relative to their verbal analogs (e.g., design fluency < word generation; Picture Arrangement < word sequencing). In contrast, patients with left FTD showed the opposite pattern. In addition, the 2 patient groups differed on several absolute test scores; patients with right FTD demonstrated more errors and perseverative responses, and worse percent conceptual level responses, on the Wisconsin Card Sorting Test, while the left FTD patients obtained significantly worse scores on the Boston Naming Test, and Stroop word reading and color naming. Verbal and nonverbal memory, mental speed, visual perceptual-constructional skill, and IQ subtest scaled scores did not significantly differ between groups. These data indicate that FTD should not be viewed as a unitary disorder, and that neuropsychological testing holds promise for the differential diagnosis of right versus left FTD.     

MRI volumetry and proton MR spectroscopy of the brain in Lafora disease

PURPOSE: To determine brain involvement in Lafora disease by means of 3-T MRI volumetry and 1H magnetic resonance (MR) spectroscopy. METHODS: Ten patients with Lafora disease and 10 healthy controls were included in the study. The diagnosis of Lafora disease was proven genetically by the presence of mutations in the EPM2A gene in all patients, and their evolution was staged in three groups according to their functional state. MRI volumetry was performed by means of AX3DT1 images with assessment of the cerebellum and the brainstem, by using the program Stereonauta, and all the brain structures, by using voxel-based morphometry. [1H]MR spectroscopy was performed by using an Eclipse PRESS sequence probe system with 8-cc voxels positioned in the occipital and frontal cortexes, basal ganglia, pons, and cerebellar hemispheres. Spectral peak areas corresponding to NAA (N-acetylaspartate), creatine, and choline were obtained. RESULTS: MRI volumetry showed no statistically significant differences in patients compared with healthy controls in any of the analyzed structures. Analysis of [1H]MR spectroscopy data showed a statistically significant reduction in the NAA/creatine ratio in patients compared with controls in the frontal (p = 0.001) and occipital cortex (p = 0.043), basal ganglia (p = 0.002), and cerebellar hemispheres (p = 0.007). The NAA/choline and choline/creatine ratios were statistically significantly different in the frontal cortex (p = 0.005). No correlation was observed between the disease-evolution stage and MRI-measured volumes (range, -0.92 to 0.44) or [1H]MR spectroscopy values (range, -0.29 to 0.50). CONCLUSIONS: In our series of Lafora disease patients, [1H]MR spectroscopy was more sensitive than structural MRI to detect brain involvement. The brain cortex, especially frontal cortex, cerebellum, and basal ganglia, showed the greatest metabolic changes.     

Musical consonances and dissonances: Are they distinguished independently by the right and left hippocampi?

Our study sought to determine whether, where and how the consonance or dissonance of musical intervals might be reflected in the electrical activity (depth EEG) of the human brain. Presenting an adequate musical test program to a patient with depth electrodes implanted within the planum temporale (near Heschl's gyrus) and the hippocampal formations of both sides, we found that the reactions shown by the depth EEG of the limbic system correspond in precise and distinctly differing patterns to the consonances and dissonances presented. The main findings are: (1) the EEG of the left hippocampus reflects the consonance-dissonance dichotomy; (2) the activity of the left hippocampus but not the right is affected by a previous sequence of dissonances in responding to a single consonance; (3) the EEG activity of the right Heschl's gyrus (the left Heschl's gyrus was not analyzed), but neither the left nor the right hippocampus, responded differently to a given succession of intervals and its pitch inversion. These results may help to understand the different emotional responses which usually arise in response to consonant or dissonant musical intervals.     

Detection and characterization of neurotoxicity in cancer patients using proton MR spectroscopy

OBJECTIVE: The study objective was to detect abnormalities and identify relationships between brain metabolic ratios determined by proton magnetic resonance spectroscopic imaging ((1)H-MRSI) and neuropsychological (NP) function in cancer patients at risk for neurotoxicity. METHODS: Thirty-two patients received (1)H-MRSI using a multi-slice, multi-voxel technique on a 1.5T magnet. Cho/NAA, NAA/Cr, and Cho/Cr ratios were identified in seven pre-determined sites without tumor involvement. A battery of age-appropriate NP tests was administered within 7 days of imaging. Relationships were examined between test scores and metabolite ratios. CONCLUSIONS: This study identifies relationships between brain metabolite ratios and cognitive functioning in cancer patients. (1)H-MRSI may be useful in early detection of neurotoxic effects, but prospective longitudinal studies in a homogeneous population are recommended to determine the prognostic value.