Cerebral metabolic changes in delayed carbon monoxide sequelae studied by proton MR spectroscopy

The pathogenesis of delayed sequelae of carbon monoxide (CO) exposure is still unknown. We repeatedly examined a 55-year-old woman with the interval form of CO poisoning, using proton magnetic resonance spectroscopy (MRS). When the clinical picture was severe, MRS revealed markedly lowered N-acetyl-asparatate (NAA)/creatine and phosphocreatine (Cr) ratio and slightly increased choline containing compounds (Cho)/Cr ratio. Subsequently, NAA and Cho/Cr ratio tended to return to normal, reflecting clinical improvement. Proton MRS shows the previously unrecognised neuronal activity in CO poisoning and precisely reflects the severity of symptoms. We stress the superiority of proton MRS over the conventional radiological examinations in CO poisoning.     

Reproducibility over a 1-month period of 1H-MR spectroscopic imaging NAA/Cr ratios in clinically stable multiple sclerosis patients

N-acetylaspartate/creatine (NAA/Cr) ratios, assessed with proton magnetic resonance spectroscopy, are increasingly used as a surrogate marker for axonal dysfunction and degeneration in multiple sclerosis (MS). The purpose of this study was to test short-time reproducibility of NAA/Cr ratios in patients with clinically stable MS. In 35 MS patients we analysed NAA/Cr ratios obtained with (1)H-MR spectroscopic imaging at the centrum semiovale either with lateral ventricles partially included (group 1; n=15) or more cranially with no ventricles included (group 2; n=20). To test short-term reproducibility of the NAA/Cr measurements, patients were scanned twice 4 weeks apart. We determined mean NAA/Cr and Cho/Cr ratios of 12 grey matter and 24 white matter voxels. Mean NAA/Cr ratios of both the white and grey matter did not change after 4 weeks. Overall 4-week reproducibility of the NAA/Cr ratio, expressed as coefficient of variation, was 4.8% for grey matter and 3.5% for white matter. Reproducibility of cranial scanning of the ventricles was slightly better than with cerebrospinal fluid included. Our study shows good short-term reproducibility of NAA/Cr ratio measurements in the centrum semiovale, which supports the reliability of this technique for longitudinal studies.     

Proton MR spectroscopy of the brain in infants

Proton magnetic resonance spectroscopy (MRS) was used to study the brain of 2 normal and 15 abnormal infants aged from 33 weeks postmenstrual age (PMA) to 14 months postnatal age. Eleven of the infants were examined on at least two occasions. The principal clinical diagnoses in the abnormal infants were perinatal ischemic and hemorrhagic brain injury. All proton spectra demonstrated peaks that were assigned to N-acetylaspartate (NAA), choline containing compounds (Cho), and creatine plus phosphocreatine (Cr). The NAA/Cho and NAA/Cr ratios increased with age, while the Cho/Cr ratio decreased with age in the majority of infants. The NAA/Cho ratio was generally lower in abnormal infants, but the difference was not apparent before 40 weeks (PMA). This ratio was lowest in infants with the severest degree of neurological abnormality. Proton and phosphorus MRS was compared in seven infants. In those with severe brain lesions, early phosphorus spectra were abnormal. On follow-up the phosphorus spectra became normal, but the proton spectra showed persistently low NAA/Cho and NAA/Cr ratios. Proton MRS provides new information that may be complementary to phosphorus MRS in the diagnosis and monitoring of brain development in normal and neurologically damaged infants.     

Magnetic resonance spectroscopy features of normal-appearing white matter in patients with acute brucellosis

We aimed to evaluate whether the subtle metabolic cerebral changes are present in normal-appearing white matter on conventional MRI, in patients with acute brucellosis, by using MR spectroscopy (MRS). Sixteen patients with acute brucellosis and 13 healthy control subjects were investigated with conventional MRI and single-voxel MRS. Voxels were placed in normal-appearing parietal white matter (NAPWM). N-Acetyl aspartate (NAA)/creatine (Cr) and choline (Cho)/Cr ratios were calculated. There was no significant difference between the study subjects and the control group in NAA/Cr ratios obtained from NAPWM. However, the Cho/Cr ratios were significantly higher in patients with acute brucellosis compared to controls (p=0.01). MRS revealed metabolic changes in normal-appearing white matter of patients with brucellosis. Brucellosis may cause subtle cerebral alterations, which may only be discernible with MRS. Increased Cho/Cr ratio possibly represents an initial phase of inflammation and/or demyelination process of brucellosis.     

Monitoring the effects of mobile phone use on the brain by proton magnetic resonance spectroscopy

PURPOSE: To determine whether extensive use of mobile phones affects brain metabolites detectable by proton magnetic resonance spectroscopy (1H MRS). MATERIALS AND METHODS: Twenty-one extensive mobile phone users (average use = 5.5 +/- 2.2 years at 2.4 +/- 1.1 hours/day) and 15 control subjects were recruited and submitted to a 1H MRS brain examination at 1.5 Tesla. Data were recorded in the most exposed right temporal and pontobulbar areas as well as in the contralateral left temporal area. The ratios of N-acetylaspartate (NAA), choline (Cho) and myo-inositol (mI) to creatine/phosphocreatine (Cr) were measured. RESULTS: No statistically significant changes in the NAA/Cr, Cho/Cr and mI/Cr ratios were measured between mobile phone users and control subjects and between the exposed and contralateral temporal areas. CONCLUSION: These results indicate that extensive exposition to mobile phone radiation does not cause MRS-detectable brain metabolic changes.     

MR动脉血质子自旋标记与波谱成像在颈内动脉系统狭窄或闭塞的应用研究

目的 探讨MR动脉血质子自旋标记(ASL)与氢质子磁共振波谱成像(1H-MRS)在颈动脉系统狭窄或闭塞的应用价值. 资料与方法 28例单侧颈内动脉(ICA)/大脑中动脉(MCA)重度狭窄或闭塞患者行ASL 和1H-MRS检查.对ASL后处理的相对脑血流量(CBF) 图进行定性和定量分析;对1H-MRS测量病变侧和对侧脑组织的氮-乙酰天门冬氨酸(NAA)、胆碱(Cho)、肌酸(Cr)的波峰下面积,比较两侧各代谢物峰下面积比值(NAA/Cho、NAA/Cr、Cho/Cr)的差异,并观察是否出现乳酸(Lac)峰. 结果 28例CBF图显示18例病变侧灌注较对侧降低,10例未见明显异常;1H-MRS显示病变侧的NAA/Cho、NAA/Cr低于对侧,差异有统计学意义(P<0.01),Cho/Cr高于对侧,差异有统计学意义(P<0.01),3例于病变侧检测到Lac峰. 结论 ASL 能够早期发现颈动脉系统狭窄或闭塞患者的CBF改变,1H-MRS能够显示缺血脑组织的代谢异常.     

氢质子磁共振波谱在小儿颞叶癫痫研究中的应用

目的 结合MRI和脑电图（EEG）所见，评价氢质子磁共振波谱（^1H MRS)在小儿颞叶癫痫诊断中的价值。方法 对10例颞叶癫痫患儿和8例健康自愿儿用2．0T场强MR扫描系统进行MRI及^1H MRS采集。测定N－乙酰天门冬氨酸（NAA）、胆碱（Cho)、肌酸（Cr)、乳酸（Lac)、肌醇（MI）、谷氨酸及谷氨酰胺（Glu/Gln)等代谢产物。结果 以NAA／（Cr Cho)值为标准，海马硬化侧组及脑电图异常侧组与对照组间比较，差异有显著性意义（平均差异分别为0．7663、0．6190，P＜0．05）。结论 ^1H MRS在小儿颞叶癫痫灶诊断的敏感性高于MRI，且有助于脑电图定位诊断。     

Proton MR spectroscopy in neuroborreliosis: a preliminary study

We report results of a magnetic resonance spectroscopy (MRS) study in 12 patients with neuroborreliosis. We used a PRESS sequence, placing an 8 cm³ voxel in normal-appearing white matter of the frontal lobe. Peaks indicating N-acetylaspartate (NAA), choline (Cho), creatine (Cr), myo-inositol (mI), lipids (Lip) and lactate (Lac) were identified and ratios of NAA/Cr, Cho/Cr, mI/Cr, Lip/Cr, Lac/Cr calculated. Significant increases in Cho/Cr and Lip/Cr were noted. No abnormality was found in mean NAA/Cr and Lac/Cr, but in four patients there was a decreased NAA peak; mI/Cr ratio was slightly increased. Although the spectroscopic profile in patients with neuroborreliosis seems to be nonspecific, MRS might be useful for assessing tissue damage of the central nervous system.     

磁共振质子波谱在颞叶癫痫诊断中的应用

目的　评价磁共振质子波谱 (1HMRS)诊断颞叶癫痫的价值。方法　对 30例颞叶癫痫患者和 30例健康志愿者用 2 0T场强的MR成像系统分别进行双侧颞叶的质子波谱采集 ,定量分析N 乙酰天门冬氨酸 (NAA)、肌酸 (Cr)和胆碱复合物 (Cho)等代谢产物的变化。结果　癫痫病人NAA峰降低。以NAA/ (Cr Cho)值为判断标准 ,2 5例病人可以定侧诊断 ,敏感性 83% ,并发现 14例双侧病变 ,占 47%。结论　1HMRS可无创性探测脑组织内生化改变 ,对癫痫灶的定侧诊断具有很高的价值     

Relative Concentrations of Proton MR Visible Neurochemicals in Gray and White Matter in Human Brain

The relative distributions of N-acetylaspartate (NAA) + N-acetylaspartylglutamate (NAAG), creatine + phosphocreatine (Cr/PCr), and choline (Cho) in the gray and white matter of human brain were determined by utilizing proton magnetic resonance spectroscopic imaging (SI). The SI data was processed using an automated spectroscopic image processing algorithm, and image segmentation was performed using a supervised technique. Linear regression analysis indicated that the NAA + NAAG (2.01 ppm) and Cr/PCr (3.02 ppm) peaks are greater in gray matter compared with white matter. The large intersubject variation observed in the Cho (3.20 ppm) resonance prevented the assessment of its regional distribution with confidence.     

Asymmetry and gender effect in functionally lateralized cortical regions: a proton MRS imaging study

PURPOSE: to compare metabolite concentrations and ratios in gray matter regions known for their anatomical/functional asymmetry and evaluate gender effect. MATERIALS AND METHODS: Proton MRS imaging was performed at 1.5 T with TR/TE 2300/280 msec in 20 healthy right-handed subjects (mean age 29.6 +/- 5.3 years, 10 men). Concentrations of N-acetyl aspartate (NAA), choline (Cho), and creatine (Cr), and the peak area ratios NAA/Cho, NAA/Cr, and Cho/Cr were evaluated in hippocampal and parahippocampal gyri, thalamus, insula, Broca's and Wernicke's areas (and corresponding contralateral areas), primary and secondary visual areas, temporal, inferior parietal, cingulate, supplemental motor, dorsolateral prefrontal, and sensorimotor areas. Linear mixed-effects regression models were used for statistical analyses. RESULTS: NAA concentration and NAA/Cho were higher in the left thalamus by 21.9% and 20%, respectively (both P < 0.001). NAA concentration was 13% higher in the region contralateral to Wernicke's area (P < 0.02). No gender differences were found. CONCLUSION: Metabolite concentrations and ratios were symmetric and gender independent in most brain regions, however small hemispheric side differences in the thalamus and in Wernicke's area were found.     

大鼠弥漫性颅脑损伤磁共振波谱初步研究

目的 探讨磁共振波谱(MRS)揭示弥漫性颅脑损伤(DBI)的细胞代谢改变及早期动态演变的价值。材料与方法 以SD雄性大鼠为对象，自由落体法复制DBI动物模型，于损伤后4、8、24、48h行MRS检查(其中各鼠均于损伤前行MRS检查以作对照)，观察氮-乙酰天门冬氨酸(NAA)／肌酸(Cr)、胆碱(Ch♂)／Cr、NAA在DBI中随时间发展的演变过程。结果 与损伤前相比，DBI后4h下降显著，8、24h轻度回升；48h复又回落。各个观察时段Cho／Cr、NAA变化无统计学意义。结论 DBI^1H-MRS各项指标中，NAA／Cr较敏感。通过观测NAK／Cr的变化，可早期诊断DBI，且对病情的发展作出准确的估测。     

White Matter Proton MR Spectroscopy in Children with Isolated Developmental Delay: Does it Mean Delayed Myelination?

RATIONALE AND OBJECTIVES: Isolated developmental delay (IDD) is a common disorder in preschool and school-age children. Conventional magnetic resonance imaging (MRI) usually does not disclose abnormalities, but a myelination delay is suspected as causative or associated factor. N-acetyl-aspartate is a surrogate marker of neuronal integrity but also of axonal integrity. The goal of our study is to determine whether magnetic resonance spectroscopy (MRS) is able to detect alterations in the white matter supporting the hypothesis of delayed myelination in children with IDD and normal MRI. MATERIALS AND METHODS: In this cross-sectional study, we enrolled 12 consecutive children meeting the criteria if IDD and aged between 3 and 12 years (mean 7.25 years) and 11 healthy children as control group (mean age 7.18, range 3-12 years) on whom we performed conventional MRI and MRS. We did not include children with abnormal MRI. Single voxel (8 cm(3)) was placed in the white matter of the left centrum semiovale. The mode of acquisition was probe-p (PRESS technique) with a TR of 2500 milliseconds and a TE of 30 milliseconds. We measured the metabolite concentration of n-acetyl-aspartate (NAA), choline (Ch), creatine (Cr) y myo-inositol (mI), and ratios of NAA, Ch, and mI to creatine. RESULTS: In children with IDD, we found a significant decrease of the following ratios: NAA/Cr (P < .016), NAA/Ch (P < .026), and NAA/mI (P < .023) in relation to controls. The mean NAA/Cr ratio in IDD children was 1.92 (SD 0.14), and in controls it was 2.09 (SD 0.14); t = 2.62, fd (freedom degrees) = 21, P < .016. No differences were seen in the remaining ratios. CONCLUSIONS: The lower NAA/Cr ratio in children with IDD in relation to controls may be a promising marker of this disorder and supports the hypothesis of delayed myelination. MRS can provide important information in children with neurodevelopmental disorders.     

Reproducibility of short echo time proton magnetic resonance spectroscopy using point-resolved spatially localized spectroscopy sequence in normal human brains.

The reproducibility of short echo time proton MR spectroscopy (1H-MRS) in normal human brains was examined. Thirteen healthy volunteers were studied, and each underwent three MRS examinations. Second and third measurements were done on the same day, about two months after the first measurement, and interday and intraday reproducibility were evaluated. MRS was performed with proton brain examination/single voxel (PROBE/SV) and point-resolved spatially localized spectroscopy (PRESS) (repetition time = 2000 ms, echo time = 30 ms). Five metabolite ratios were computed; N-acetyl-aspartate (NAA)/creatine (Cr), choline (Cho)/Cr, myo-inositol (mI)/Cr, NAA/(NAA + Cr + Cho), and NAA/Cho. Their normal range and reproducibility were measured. For each metabolite ratio, there was no significant difference between interday difference and intraday difference, suggesting that the interval of two months has minimal effect on MRS measurements. MRS may be utilized for the observation of central nervous system diseases.     

Proton MR spectroscopy of intracranial tumours: in vivo and in vitro studies

Proton magnetic resonance spectroscopy (1H MRS) was used to investigate intracranial tumours in vitro and in vivo. Biopsy specimens were studied from 47 patients, 11 of whom were also examined in vivo. Analysis was based on the signals from N-acetylaspartate (NAA), phosphocreatine plus creatine (Cr), choline-containing compounds (Cho), alanine (Ala), and lactate. Biopsy data from 26 astrocytomas showed that the NAA/Cr ratio differs significantly in all grades from its value in normal white matter and that the Cho/Cr ratio differs significantly in grade IV tumours from its value in the other grades. Meningiomas have an unusually high Ala/Cr ratio. Spectra obtained in vivo are consistent with in vitro results from the same patients, and their lactate signal provides additional information about abnormal metabolism. We conclude that 1H MRS has a clear role in the diagnosis and biochemical assessment of intracranial tumours and in the evaluation and monitoring of therapy.     

短暂性脑缺血发作与脑梗死的1H-MRS比较研究

目的比较短暂性脑缺血发作（TIA）和脑梗死的氢质子磁共振波谱（1^H-MRS）改变,探讨1^H-MRS在TIA中的应用价值。资料与方法对30例TIA和24例脑梗死患者行1^H-MRS检查,同期选择24名健康志愿者作为对照。分别比较TIA患者病变侧和对侧半卵圆中心、脑梗死患者梗死灶与对侧正常脑组织代谢物氮-乙酰天门冬氨酸（NAA）、胆碱（Cho）和肌酸（Cr）含量的差异,并观察有无乳酸（Lac）峰出现,再对TIA患者、脑梗死患者及正常对照组之间脑内NAA、Cho、Cr和Lac含量的差异进行比较。结果TIA患者病变侧半卵圆中心NAA降低、Cho升高,与对侧相应区域以及正常对照组比较差异均有统计学意义（P〈0.01）,而两侧Cr含量差异无统计学意义（P〉0.05）,脑梗死患者梗死灶内NAA、Cho和Cr与对侧正常脑组织和正常对照组比较均有下降,差异有统计学意义（P〈0.01）,但TIA患者NAA下降幅度明显小于脑梗死患者,差异有统计学意义（P〈0.01）;10例TIA患者、23例脑梗死患者于病侧发现Lac峰,TIA的Lac含量低于脑梗死,差异有统计学意义（P〈0.01）。结论TIA患者缺血脑组织存在代谢异常,但较脑梗死轻微,1^H-MRS能够早期发现这种异常,对TIA的早期诊断和治疗具有重要价值。     

Long and short echo time proton magnetic resonance spectroscopic imaging of the healthy aging brain

PURPOSE: To investigate the relationship between subject age and white matter brain metabolite concentrations and R(2) relaxation rates in a cross-sectional study of human brain. MATERIALS AND METHODS: Long- and short-echo proton spectroscopic imaging were used to investigate concentrations and R2 relaxation rates of N-acetyl aspartate (NAA) + N-acetyl aspartyl glutamate (NAAG), choline (Cho), creatine (Cr), and myoinositol (mI) in the white matter of the centrum semiovale of 106 healthy volunteers aged 50-90 years; usable data were obtained from 79 subjects. A major aim was to identify which parameters were most sensitive to changes with age. Spectra were analyzed using the LCModel method. RESULTS: The apparent R2 of NAA and the LCModel concentration of Cr at short echo time were significantly correlated with age after multiplicity correction. Large lipid resonances were observed in the brain midline of some subjects, the incidence increasing significantly with age. We believe this to result from lipid deposits in the falx cerebri. CONCLUSION: Since only short-echo spectroscopy showed a robust relationship between Cr and subject age, and detects more metabolites than long echo time, we conclude that short-echo is superior to long-echo for future aging studies. Future studies could usefully determine whether the Cr-age relationship is due to changes in concentration, T1, or both.     

Effect of seizure on hippocampus in mesial temporal lobe epilepsy and neocortical epilepsy: an MRS study

This study was performed to evaluate the effect of seizures on the bilateral hippocampus in mesial temporal lobe epilepsy (mTLE) and neocortical epilepsy by single voxel proton magnetic resonance spectroscopy (MRS). Forty-one patients with mTLE having unilateral hippocampal sclerosis and 43 patients with a neocortical epilepsy who underwent subsequent epilepsy surgery were recruited. Ninety-five percent confidence intervals of N-acetyl aspartate/choline (NAA/Cho) and NAA/creatine (NAA/Cr) ratios in 20 healthy control subjects were used as threshold values to determine abnormal NAA/Cho and NAA/Cr. NAA/Cho and NAA/Cr were significantly lower in the ipsilateral hippocampus of mTLE and neocortical epilepsy. Using asymmetry indices for patients with bilaterally abnormal ratios of NAA/Cho and NAA/Cr in addition to using unilateral abnormal ratio, the seizure focus was correctly lateralized in 65.9% of patients with mTLE and 48.8% of neocortical epilepsy patients. Bilateral NAA/Cho abnormality was significantly related to a poor surgical outcome in mTLE. No significant relationship was found between the results of NAA/Cho or NAA/Cr and surgical outcome in neocortical epilepsy. The mean contralateral NAA/Cr ratio of the hippocampus in mTLE was significantly lower in patients with a history of secondary generalized tonic-clonic seizure (SGTCS) than in those without. Our results demonstrate effects of seizures on the hippocampi in neocortical epilepsy and the relation between SGTCS and NAA/Cr of the contralateral hippocampus in mTLE. This proves the presence of a seizure effect on the hippocampus in neocortical epilepsy as well as in mTLE.     

Magnetization transfer imaging and magnetic resonance spectroscopy of normal-appearing white matter in late-life major depression

PURPOSE: To examine the relationships between the damaged macromolecular pool seen on magnetization transfer (MT) imaging and cerebral metabolic changes recorded by magnetic resonance spectroscopy (MRS), in frontal white and gray matter regions of late-life MDD patients. MATERIALS AND METHODS: MT imaging and MRS were performed on eight patients with late-life MDD and eight age-matched healthy controls. MT ratios were calculated using the on-resonance and off-resonance images. Correlations were computed between MT ratios and the ratios of several metabolites, including choline (Cho), myo-inositol (mI), N-acetylaspartate (NAA), and N-acetylaspartylglutamate (NAAG), to creatine (Cr). RESULTS: Statistically significant correlations were found in white matter between the MT ratios and mI/Cr (r = -0.90, N = 7, P = 0.016), and between the MT ratios and (NAA + NAAG)/Cr (r = -0.89, N = 8, P = 0.007). No significant correlations were found in gray matter or between the MT ratios and NAA/Cr or Cho/Cr in white matter. CONCLUSION: Changes in the white matter macromolecular protein pool, observed as reduced MT ratios, may be related to changes in the mI and the total NAA pools. These findings may have implications for the pathophysiology of late-life major depression.     

Assessment of malignancy in gliomas by 3T 1H MR spectroscopy

The purpose of this study was to assess clinical 1H MR spectroscopy (MRS) as a noninvasive method for evaluating brain tumor malignancy at 3T high-field system. Using 3T MRI/MRS system, localized water-suppressed single-voxel technique in patients with brain tumor (i.e., gliomas) was employed to evaluate spectra with peaks of N-acetyl aspartate (NAA), choline-containing compounds (Cho), creatine/phosphocreatine (Cr) and lactate. On the basis of Cr, these peak areas were quantitated as a relative ratio. The variation of metabolite measurements of the designated region in 10 normal volunteers was less than 10%. Normal ranges of NAA/Cr and Cho/Cr ratios were 1.67+/-018 and 1.16+/-0.15, respectively. NAA/Cr ratio of gliomas was significantly lower than that of the normal tissues (P= .005), but Cho/Cr ratio of gliomas was significantly higher (P= .001). Cho/Cr ratio of high-grade gliomas was significantly higher than that of low-grade gliomas. The present study demonstrated that the neuronal degradation or loss was observed in all gliomas. Higher-grade glioma was correlated with higher Cho/Cr ratio, indicating a significant dependence of Cho levels on malignancy of gliomas. Our results suggest that clinical 1H MR spectroscopy could be useful to predict tumor malignancy.