Clinical and imaging study of human immunodeficiency virus-1-infected youth receiving highly active antiretroviral therapy: pilot study using magnetic resonance spectroscopy

In the initial assessment of children with new-onset seizures, the suggestion that electroencephalography (EEG) should be standard and that magnetic resonance imaging (MRI) should be optional has been questioned. The purposes of this children (four boys) with vertically transmitted stable HIV infection had a neurologic examination, neuropsychologic testing, and a neuroimaging study. The structural magnetic resonance imaging (MRI) and metabolic changes (magnetic resonance spectroscopy) were compared with the cognitive, clinical, and laboratory results. Our results for the eight children who completed the magnetic resonance spectroscopic study showed that a high N-acetylaspartate (NAA) to choline ratio correlated significantly with IQ subtests of arithmetic (r = .74; P < .034) and comprehension (r = .77; P = .025). Our results suggest that lower NAA and higher choline values represent neuronal dysfunction and inflammation that can be recognized before anatomic changes appear on MRI. In addition, a low NAA to Cho ratio correlated with poor performance. These data suggest that magnetic resonance spectroscopy can be used as a follow-up tool in addition to the structural MRI. Moreover, a change in a child's performance with a concomitant change in NAA and choline, as measured with magnetic resonance spectroscopy, could indicate the need for more aggressive intervention.     

正常人丘脑质子磁共振波谱分析

背景：磁共振波谱使神经影像学从单纯形态学观察进入到分子水平上的探索,有研究利用磁共振波谱发现疾病发生时丘脑生化代谢物质与正常人存在差异。 目的：利用氢质子磁共振波谱(1H-MRS)观察正常人的丘脑代谢特点,为正常人及脑部疾患的相关治疗提供客观依据。 设计、时间及地点：自身对照,横断面调查,于2007-08/2008-08在解放军第九一中心医院影像中心完成。 对象：选择解放军第九一中心医院附近社区的精神正常的居民及学生共56名,男32名,女24名。所有受检者或其监护人均对调查方案知情同意,并签署知情同意书, 方法：采用1.5T超导型磁共振成像系统,入组24 h后采用多体素1H-MRS检测丘脑生化代谢物N-乙酰天冬氨酸、胆碱复合物与肌酸复合物。 主要观察指标：用随机软件测量N-乙酰天冬氨酸、胆碱复合物、肌酸复合物的峰下面积,以肌酸复合物峰为参照,计算机自动完成N-乙酰天冬氨酸/肌酸复合物值、胆碱复合物/肌酸复合物值、N-乙酰天冬氨酸/(胆碱复合物+肌酸复合物)值的计算。 结果：正常人丘脑1H-MRS左侧N-乙酰天冬氨酸/肌酸复合物、N-乙酰天冬氨酸/(胆碱复合物+肌酸复合物)高于右侧,胆碱复合物/肌酸复合物低于右侧,但差异但差异无显著性意义(P > 0.05)。经Pearson分析,丘脑双侧各观察指标与年龄均无相关性(P > 0.05);不同性别间比较,男性组左右两侧N-乙酰天冬氨酸/肌酸复合物、右侧胆碱复合物/肌酸复合物、左侧N-乙酰天冬氨酸/(胆碱复合物+肌酸复合物)均高于女性组,余观察指标低于女性组,但差异均无显著性意义(P > 0.05)。 结论：正常人丘脑代谢物双侧无差异,代谢物水平可能并不受性别和年龄的影响。     

In vivo hippocampal metabolic dysfunction in human temporal lobe epilepsy

BACKGROUND: The nature of functional metabolic disturbances in mesial temporal lobe epilepsy remains unclear. OBJECTIVES: To compare in vivo measures of hippocampal metabolic abnormalities in mesial temporal lobe epilepsy, as acquired with fludeoxyglucose F 18 positron emission tomography and proton magnetic resonance spectroscopic imaging, and to determine the relationship between N-acetylaspartate (NAA) disturbances and well-established derangements of glucose metabolism. DESIGN: Measures of hippocampal glucose metabolism from fludeoxyglucose F 18 positron emission tomography were normalized to whole brain counts to provide a glucose uptake metabolic index. Proton magnetic resonance spectroscopic imaging was performed at 4.1 T, and measures of creatinine/NAA ratio were made from mostly hippocampal-only voxels. Direct comparisons and correlation analysis of measures were performed. SETTING: Presurgical evaluations for treatment of intractable epilepsy. PATIENTS: Twenty-nine patients between July 1994 and June 1996 who were candidates for anterior-medial temporal lobectomy at the epilepsy centers of the University of Alabama at Birmingham and Vanderbilt University schools of medicine were studied. RESULTS: The mean ipsilateral hippocampal glucose metabolic index (0.85) was normal, while the contralateral metabolic index (0.95) was nearly significant for an abnormally elevated measure. The mean ipsilateral hippocampal creatinine/NAA (1.26) was abnormally elevated; the mean contralateral creatinine/NAA (0.88) was normal. Hippocampal glucose and creatinine/NAA measures did not correlate; asymmetry measures also did not correlate. CONCLUSIONS: Hippocampal metabolic disturbances in mesial temporal lobe epilepsy as measured by fludeoxyglucose F 18 positron emission tomography vs proton magnetic resonance spectroscopic imaging reflect different mechanisms of biochemical dysfunction. This lack of correlation is hypothesized to reflect a differential effect of varying degrees of disturbed cellular energy metabolism on mechanisms of glucose use and biosynthesis of NAA.     

精神分裂症阳性症状与脑质子波谱及事件相关电位的相关性

目的:探讨阳性症状为主型精神分裂症患者前额叶和丘脑氢质子磁共振波谱(1H-MRS)与事件相关电位的相关性。方法:78例7d内未使用抗精神病药及影响脑内乙酰胆碱神经递质药阳性症状为主型精神分裂症患者(研究组)及56名正常对照(对照组)。研究组在入组24h内采用多体素1H-MRS检测前额叶和丘脑生化代谢物N-乙酰基天门冬氨酸(NAA)、胆碱复合物(Cho)与肌酸复合物(Cr),计算NAA/Cr和Cho/Cr值;同时检测事件相关电位P300(P300)和听觉诱发电位(AEP),并与对照组进行比较。结果:研究组NAA/Cr值左侧前额叶、左侧丘脑均低于对照组,差异有统计学意义[(1.40±0.35)vs(1.60±0.39),t=3.11,P<0.01;(1.48±0.33)vs(1.64±0.36),t=2.50,P<0.05]。研究组P300靶刺激P3(Cz、FPz)、非靶刺激NP3(Cz、FPz)与AEPP2(FPz)的潜伏期均高于对照组,靶刺激P3(Cz、FPz)、非靶刺激NP3(Cz、FPz)及AEPN1-P2(Cz、FPz)波幅均低于对照组,差异均有统计学意义(P<0.05或P<0.01)。研究组左侧前额叶NAA/Cr值与Cz点的P3潜伏期呈负相关(r=-0.32,P<0.05),与P3、N1-P2波幅呈正相关(r=0.32、0.34,P均<0.05);与FPz点P3、NP3、P2潜伏期呈负相关(r=-0.37、-0.40、-0.41,P均<0.01),与P3、NP3、N1-P2波幅呈正相关(r=0.33、0.33、0.35,P均<0.05)。结论:阳性症状为主型精神分裂症患者左侧前额叶NAA代谢失衡与认知功能损害有关,低水平的NAA浓度可能是认知功能损害的发病机制之一。     

Neuronal dysfunction of the frontal lobe in schizophrenia

Localized in vivo proton magnetic resonance spectroscopy (MRS) was performed to evaluate metabolic alterations in the right and left frontal lobe before and after antipsychotic treatment of schizophrenic patients (n=24) and a group of healthy normal subjects (n=20). Proton metabolic ratios obtained from the 8 cm3 voxels in the right and left frontal lobes were compared with the clinical assessment for each subject. There was no significant difference in the metabolic ratios between the right and the left frontal lobes in either the schizophrenic group or the control group, indicating no laterality. Compared with those of the normal control group, NAA/Cr ratio of the schizophrenic patients showed significantly lower value. The NAA/Cr ratio of the schizophrenic patients was not changed after antipsychotic treatment. The present study supports the 'hypofrontality' hypothesis of schizophrenia.     

Dorsolateral prefrontal cortex contribution to abnormalities of the P300 component of the event-related potential in schizophrenia

Abnormalities of the P300 component of the event-related potential are a common finding in schizophrenia. It seems possible that the dysfunction in the dorsolateral prefrontal (DLPF) region that has been reported in schizophrenia contributes to this finding. To explore this possibility, we calculated the relationship between, on the one hand, P300 latency and amplitude and, on the other hand, the degree of DLPF atrophy (as measured by magnetic resonance imaging) and metabolic activity during an attentional task (as measured by positron emission tomography). Seventeen schizophrenia patients with a brief duration of illness and minimal exposition to treatment and 25 healthy controls were studied. Patients exhibited significantly lower metabolic activity in the DLPF region, but they did not show cortical atrophy. P300 amplitude was also significantly reduced in the schizophrenia patients compared with the controls. Right DLPF region metabolic activity correlated significantly with P300 amplitude. This pattern remained after partialling out the influence of activity in the hippocampus, superior temporal gyrus and parietal lobe. It is therefore suggested that the prefrontal cortex could be implicated in the P300 amplitude reduction in schizophrenia.     

Proton magnetic resonance spectroscopy of the brain in dementia

Proton magnetic resonance spectroscopy (MRS) allows accurate and noninvasive biochemical assay of living tissues. In vivo measurements provided by MRS have greatly enhanced our understanding of the pathophysiology of dementia. Increases in choline and myo-inositol (markers of membrane turnover) have been demonstrated in several studies on patients with Alzheimer's disease (AD), suggesting the presence of a significant cellular membrane (and glial) pathology in this disorder. Large decreases in brain N-acetylaspartate (NAA) (a marker of neuroaxonal integrity) are commonly seen in AD as well as in other forms of dementia in cerebral gray and white matter, indicating the presence of significant axonal damage. Since greater NAA decreases have been demonstrated in brains of patients with clinically more severe disease, NAA could provide an index relevant to patients' clinical status. Brain metabolic changes can be independent of abnormalities detected by conventional magnetic resonance imaging (MRI), since proton MRS may show a normal metabolic pattern in patients with mild neurological impairment and severe MRI abnormalities. However, quantitative measurements of regional brain volumes can be useful in the diagnosis of dementia. Thus, proton MRS, alone or combined with new quantitative magnetic resonance techniques, can provide sensitive indices able to monitor disease progresson or effects of drug therapy.     

Thalamic proton magnetic resonance spectroscopy in vegetative state induced by traumatic brain injury

OBJECTIVES: To determine whether proton magnetic resonance spectroscopy (MRS), a newer radiographic technology, would be useful in the evaluation of the thalamus of patients in vegetative states resulting from traumatic brain injury. METHODS: 14 victims of severe traumatic brain injury who were in the vegetative state and whose magnetic resonance images of the thalamus were normal underwent bilateral thalamic proton (MRS) studies. The N-acetyl aspartate to creatine (NAA:Cr) and choline to creatine (Cho:Cr) ratios were obtained for each patient. The proton thalamic MRS findings of patients who were in a persistent vegetative state (n = 8) and in patients who had regained awareness after being in the vegetative state (n = 6) were compared with proton thalamic MRS findings in five healthy volunteers. RESULTS: While conventional magnetic resonance imaging suggested that each patient had a normal thalamus, proton MRS indicated that the thalamus of each patient in the series was damaged. The NAA:Cr ratio was significantly lower in the thalami of both the patients who remained in a persistent vegetative state for the duration of the study and in those who regained awareness after being in the vegetative state (p < 0.001). In addition, NAA:Cr ratios were lower in the group of patients who remained in a persistent vegetative state than in the group of patients who regained awareness after being in the vegetative state (p < 0.001). CONCLUSIONS: Results suggest that the NAA:Cr ratio within the thalamus is significant and that thalamic MRS may be helpful when attempting to determine the degree of severity of neuronal and axonal injury in patients in the vegetative state.     

Proton magnetic resonance spectroscopy of the motor cortex in 70 patients with amyotrophic lateral sclerosis

OBJECTIVE: To evaluate proton magnetic resonance spectroscopy for detection and monitoring of upper motoneuron degeneration in patients with amyotrophic lateral sclerosis. METHODS: Seventy patients with amyotrophic lateral sclerosis according to the El Escorial criteria were compared with 48 healthy control subjects. Single-volume proton magnetic resonance spectroscopy (echo time, 272 milliseconds; repetition time, 2000 milliseconds) was performed in both motor cortices for detection of N-acetylaspartate (NAA), phosphocreatine + creatine ([P]Cr), and choline-containing compounds (Cho) to calculate the metabolite ratios NAA/Cho, NAA/(P)Cr, and Cho/(P)Cr. In addition, absolute metabolite concentrations of NAA, (P)Cr, and Cho were obtained in 30 patients and 15 controls with the unsuppressed water signal used as an internal reference. RESULTS: Absolute concentrations of NAA (P<.001) and (P)Cr (P<.05) were reduced in motor cortices of patients, whereas Cho concentrations remained unchanged. The NAA/Cho and NAA/(P)Cr ratios were reduced in all El Escorial subgroups (P<.001). The Cho/(P)Cr ratio was elevated in patients with definite amyotrophic lateral sclerosis (P<.05). Metabolite ratio changes corresponded to the lateralization of clinical symptoms and were weakly correlated with disease duration and disease severity. In follow-up observations of 16 patients during a mean (+/-SD) of 12.1 +/- 8.7 months, NAA/Cho dropped by 9.1% (P<.01), and Cho/(P)Cr increased by 7.0% (P<.01). Changes of metabolite ratios were significantly correlated with progression of disease severity. CONCLUSIONS: Measurement of NAA concentrations and NAA/Cho ratios appear to be most suitable for detection of motor cortex degeneration by single-volume proton magnetic resonance spectroscopy. Reduced NAA/Cho ratios correspond to aspects of the clinical presentation and reflect disease progression in follow-up measurements.     

Methamphetamine users in sustained abstinence: a proton magnetic resonance spectroscopy study

BACKGROUND: Abnormal patterns of metabolite levels have been detected by magnetic resonance spectroscopy in frontostriatal regions of individuals meeting DSM-IV criteria for methamphetamine dependence, but less is known about the effects of drug abstinence on metabolite levels. OBJECTIVE: To assess the effects of long-term methamphetamine use and drug abstinence on brain metabolite levels. DESIGN: To assess regional specific metabolite levels using magnetic resonance spectroscopy imaging techniques in 2 groups of currently abstinent methamphetamine users: methamphetamine users who recently initiated abstinence and methamphetamine users who had initiated abstinence more than 1 year prior to study. SETTING: Participants were recruited from outpatient substance abuse treatment centers. PARTICIPANTS: Eight methamphetamine users with sustained abstinence (1 year to 5 years) and 16 recently abstinent methamphetamine users (1 month to 6 months) were compared with 13 healthy, non-substance-using controls. MAIN OUTCOME MEASURES: Magnetic resonance spectroscopy measures of N-acetylaspartate-creatine and phosphocreatine (NAA/Cr), choline-creatine and phosphocreatine (Cho/Cr), and choline-N-acetylaspartate (Cho/NAA) ratios were obtained in the anterior cingulate cortex as well as in the primary visual cortex, which served as a control region. RESULTS: The absolute values of Cr did not differ between controls and methamphetamine users. Methamphetamine users had abnormally low NAA/Cr levels within the anterior cingulate cortex, regardless of the time spent abstinent (F(2,34) = 12.61; P<.001). No NAA/Cr group differences were observed in the primary visual cortex (F(2,33) = 0.29; P = .75). The Cho/NAA values for the anterior cingulate cortex were abnormally high in the methamphetamine users who recently initiated abstinence but followed a normal pattern in the methamphetamine users who had initiated abstinence more than 1 year prior to study (F(2,34) = 7.31; P = .002). CONCLUSIONS: The relative choline normalization across periods of abstinence suggests that following cessation of methamphetamine use, adaptive changes occur, which might contribute to some degree of normalization of neuronal structure and function in the anterior cingulum. More research is needed to elucidate the mechanisms underlying these adaptive changes.     

Neuroimaging evidence of progressive neuronal loss and dysfunction in temporal lobe epilepsy.

Whether temporal lobe epilepsy is the result of an isolated, early injury or whether there is ongoing neuronal dysfunction or loss due to seizures is often debated. We attempt to address this issue by using magnetic resonance techniques. Proton magnetic resonance spectroscopic imaging can detect and quantify focal neuronal dysfunction or loss based on reduced signals from the neuronal marker N-acetylaspartate (NAA), and magnetic resonance imaging (MRI)-based measurements of hippocampal volumes (MRIvol) can quantify the amount of atrophy in this structure. We performed magnetic resonance spectroscopic imaging and MRIvol in 82 consecutive patients with medically intractable temporal lobe epilepsy to determine whether there was a correlation between seizure frequency, or type or duration of epilepsy, with NAA to creatine (Cr) values or hippocampal volumes. Volumes and spectroscopic resonance intensities were categorized as to whether they were measured from the temporal lobe ipsilateral or contralateral to the predominant electroencephalographic focus. Ipsilateral and contralateral NAA/Cr was negatively correlated with duration of epilepsy. Hippocampal volumes were negatively correlated with duration ipsilaterally but not contralaterally. Frequency of complex partial seizures was not correlated with any of the magnetic resonance measures. However, patients with frequent generalized tonic-clonic seizures had lower NAA/Cr bilaterally and smaller hippocampal volumes ipsilaterally than patients with none or rare generalized tonic-clonic seizures. The results suggest that although an early, fixed injury may cause asymmetric temporal lobe damage, generalized seizures may also cause progressive neuronal dysfunction or loss.     

The relationship between MRI and PET changes and cognitive disturbances in MS

Cognitive dysfunction in multiple sclerosis (MS) is present in approximately 50% of the patients. Only moderate correlations have been found between cognitive dysfunction and T(2) lesion load, black holes or atrophy. Cognitive dysfunction in MS is probably related to the overall disease burden of the brain including abnormalities in normal appearing white matter (NAWM) and cortical grey matter, which is undetected with conventional magnetic resonance imaging (MRI). Hence, imaging techniques that embrace such abnormalities are needed to achieve better correlation with cognitive dysfunction. MR spectroscopy (MRS) performed with multi-slice echo planar spectroscopic imaging (EPSI) and PET measurements of brain metabolism as the cortical cerebral metabolic rate of glucose are imaging methods that are able to provide information on axonal loss or dysfunction in both MS lesions and in NAWM and cortical grey matter. Measurements of global NAA using multi-slice EPSI is a new promising method for measurement of the global neuron capacity and can be repeated with only little discomfort and without any risk for the patient.     

Axonal metabolic recovery and potential neuroprotective effect of glatiramer acetate in relapsing-remitting multiple sclerosis

Glatiramer acetate (GA) is a disease-modifying therapy for relapsing-remitting multiple sclerosis (RRMS) with several putative mechanisms of action. Currently, there is paucity of in vivo human data linking the well-established peripheral immunologic effects of therapy with GA to its potential effects inside the central nervous system (CNS). Brain proton magnetic resonance spectroscopy (MRS) allows in vivo examination of axonal integrity by quantifying the resonance intensity of the neuronal marker N-acetylaspartate (NAA). In a pilot study to investigate the effect of GA on axonal injury, we performed combined brain magnetic resonance imaging (MRI) and MRS studies in 18 treatment na?ve RRMS patients initiating therapy with GA at baseline and annually for two years on therapy. A small group of four treatment na?ve RRMS patients, electing to remain untreated, served as controls. NAA/Cr was measured in a large central brain volume of interest (VOI) as well as the normal appearing white matter (NAWM) within the VOI. After two years, NAA/Cr in the GA-treated group increased significantly by 10.7% in the VOI (2.17 +/- 0.26 versus 1.96 +/- 0.24, P = 0.03) and by 71% in the NAWM (2.23 +/- 0.26 versus 2.08 +/- 0.31, P = 0.04). In the untreated group, NAA/Cr decreased by 8.9% at two years in the VOI (2.01 +/- 0.16 versus 1.83 +/- 0.21, P = 0.03) and 8.2% in the NAWM (2.07 +/- 0.24 versus 1.90 +/- 0.29, P = 0.03). Our data shows that treatment with GA leads to axonal metabolic recovery and protection from sub-lethal axonal injury. These results support an in situ effect of GA therapy inside the CNS and suggest potential neuroprotective effects of GA.     

The effect of the skull on event-related P300.

OBJECTIVES: Event-related potentials (EP) indicate neuronal processes with a high temporal resolution, while functional magnetic resonance imaging (fMRI) has a high spatial distribution. Information from both techniques may complement each other. However, this combination is fraught with difficulty because of a possible interference of the skull or the scalp with scalp-recorded EP. The aim of the present study was to investigate this influence of skull and scalp thicknesses on event-related P300 potentials. METHODS: Thirty healthy controls were examined using an auditory evoked P300 elicited by a standard oddball paradigm. Skull and scalp thicknesses were determined using coronal T2-weighted magnetic resonance imaging (MRI). RESULTS: P3b-amplitudes were significantly correlated with temporo-parietal skull thickness (r=-0.42; P=0.021; regression slope of -1.14 microV/mm skull thickness), whereas scalp had no influence on P300. The amplitude of the more frontal subcomponent P3a was not related to frontal skull thickness. CONCLUSIONS: Therefore, the utility of P300 as a research tool can be enhanced when adjustment for skull thickness is made.     

Abnormal N-acetylaspartate in hippocampus and anterior cingulate in posttraumatic stress disorder

Magnetic resonance spectroscopic imaging (MRSI) studies suggest hippocampal abnormalities in posttraumatic stress disorder (PTSD), whereas findings of volume deficits in the hippocampus, as revealed with magnetic resonance imaging (MRI), have been inconsistent. Co-morbidities of PTSD, notably alcohol abuse, may have contributed to the inconsistency. The objective was to determine whether volumetric and metabolic abnormalities in the hippocampus and other brain regions are present in PTSD, independent of alcohol abuse. Four groups of subjects, PTSD patients with (n=28) and without (n=27) alcohol abuse and subjects negative for PTSD with (n=23) and without (n=26) alcohol abuse, were enrolled in this observational MRI and MRSI study of structural and metabolic brain abnormalities in PTSD. PTSD was associated with reduced N-acetylaspartate (NAA) in both the left and right hippocampus, though only when normalized to creatine levels in the absence of significant hippocampal volume reduction. Furthermore, PTSD was associated with reduced NAA in the right anterior cingulate cortex regardless of creatine. NAA appears to be a more sensitive marker for neuronal abnormality in PTSD than brain volume. The alteration in the anterior cingulate cortex in PTSD has implications for fear conditioning and extinction.     

Proton magnetic resonance spectroscopy of the inferior frontal gyrus and thalamus and its relationship to verbal learning task performance in patients with schizophrenia: a preliminary report

Previous research has found frontal lobe involvement in memory impairment in schizophrenia. In the present study, proton magnetic resonance spectroscopy was performed in 13 young patients with schizophrenia and 13 normal control subjects. Spectra were obtained from a voxel of 2 x 2 x 1.5 cm(3) in the bilateral inferior frontal gyrus and thalamus. Subjects were given a verbal learning task and stimulus category repetition (SCR) was calculated from the performance of the task. Significantly reduced N-acetylaspartate (NAA)/choline-containing compounds ratios were found in the left inferior frontal cortex of patients compared with controls. The total number of words recalled by patients was significantly lower than that recalled by controls. In all subjects, SCR scores were positively correlated with NAA/phosphocreatine ratios of the left inferior frontal cortex, which showed a trend towards a decrease in patients. These results support the notion of metabolic abnormalities in the left inferior frontal region related to verbal memory deficits in patients with schizophrenia.     

Phosphorus and proton magnetic resonance spectroscopy in episodic ataxia type 2.

Localized phosphorus (31P) and proton (1H) magnetic resonance spectroscopy was performed in the cerebellum and the occipital lobe of 6 patients with episodic ataxia type 2. From use of 31P magnetic resonance spectroscopy, untreated patients showed decreased high-energy phosphate ratios in the cerebrum, and increased pH in the cerebellum and cerebrum, which normalized under acetazolamide. 1H magnetic resonance spectra demonstrated high lactate peaks in 3 of the 6 patients. These metabolic alterations, probably induced by the calcium channelopathy, may characterize episodic ataxia type 2.     

Early changes in peritumorous oedema and contralateral white matter after dexamethasone: a study using proton magnetic resonance spectroscopy.

AIMS: To study the mechanism of action of steroids in patients with peritumorous oedema. METHODS: To investigate early cerebral metabolic changes proton magnetic resonance spectroscopy (1H-MRS) was used before and 11 to 14 hours after treatment with dexamethasone (12 mg oral loading and 4 mg four times daily maintenance). Nine patients (two men, seven women, mean age 54) with pronounced oedema associated with various intracranial tumours (two astrocytomas, three meningiomas, two glioblastoma, and two metastases) were examined using MRI and MRS. SE1500/135 volume selected MRS (mean volume 21 ml) were performed on an oedematous region and a contralateral region. All spectra were acquired with and without water suppression. Metabolite peak area ratios were determined. RESULTS: Regions of oedema had significantly (P < 0.01) higher unsuppressed water than the contralateral regions, as expected. There was no change at this early time point after dexamethasone. The ratio of the area of choline containing compounds to that creatine and phosphocreatine compounds was determined after which the serial ratios of these before and after were calculated (a serial ratio of 1.0 would indicate no change in the choline to creatine ratios after steroid administration). The mean serial ratios for the area of oedema were 1.02 (SEM 0.08) and 1.10 (0.08) for the contralateral volume of interest, indicating no significant changes. However, significant changes (P < 0.02) were found in the N-acetyl-aspartate (NAA)/choline serial ratios (0.86 (0.06) in the area of oedema, 1.20 (0.10) in contralateral brain) and the NAA/creatine serial ratios (0.86 (0.08) for the oedema, 1.25 (0.11) in contralateral brain). CONCLUSIONS: Such rapid changes may be explained either by relatively large alterations in the relaxation characteristics of NAA or, more controversially, by actual changes in the amounts of NAA. It is proposed that steroids act primarily by causing early metabolic changes that are later expressed in improvements in intracranial volume relations.     

Hippocampal neurochemical pathology in patients at first episode of affective psychosis: a proton magnetic resonance spectroscopic imaging study

While several studies have suggested a relationship between the hippocampus and psychosis in schizophrenia, fewer studies have specifically investigated the presence of psychosis in mood disorders from a neurobiological perspective. Moreover, a limitation of these earlier studies is that the majority of them were performed in chronic patients. The present proton magnetic resonance spectroscopic imaging (1H-MRSI) study assessed neuronal integrity (as assessed with N-acetylaspartate, NAA) in the hippocampus of patients with a first episode of mood disorders with psychotic symptoms. We studied 17 patients and 17 healthy subjects matched for age and sex. Subjects underwent 1H-MRSI, and measures of NAA, choline-containing compounds (CHO), and creatine+phosphocreatine (CRE) in 11 brain regions were obtained, i.e. hippocampus (HIPPO), dorsolateral prefrontal cortex, superior temporal gyrus, inferior frontal gyrus, occipital cortex, anterior and posterior cingulate, centrum semiovale, prefrontal white matter, thalamus and putamen. NAA/CRE ratios in HIPPO of patients were significantly lower than in controls. Sporadic and non-hypothesis-driven results were found in occipital cortex and prefrontal white matter as a main effect of diagnosis, and in superior temporal gyrus as a hemisphere by diagnosis interaction. These results would not survive a Bonferroni correction for the number of ROIs. No correlations were found with the available demographic and clinical data. Therefore, hippocampal neuronal abnormalities are present at the onset of mood disorders with psychotic symptoms. These data suggest that neuronal abnormalities in HIPPO may be associated with psychosis in mood disorders. Since these data were obtained in patients at first episode, they cannot be explained by chronicity of illness or pharmacological treatment.     

Magnetic Resonance Spectroscopy of the Thalamus in Essential Tremor Patients

BACKGROUND AND PURPOSE: Although essential tremor (ET) is one of the most common movement disorders, its pathogenesis remains obscure. The ventral intermediate nucleus of the thalamus (VIM nucleus) is suggested to play an important role in the occurrence of disease. In this study, the authors investigated the presence of biochemical or metabolic alterations in the thalamus of patients with ET using magnetic resonance (MR) spectroscopy. METHODS: The study group included 14 patients with ET who suffered from tremor predominantly in their right arm and 9 healthy controls. All patients and controls were right handed. Following conventional cranial MR imaging, single voxel proton MR spectroscopy of the thalamus involving the VIM nuclei was performed bilaterally in both the patients with ET and controls. Metabolite peaks of choline (Cho), creatine (Cr), and Nacetylaspartate (NAA) were obtained from each spectroscopic volume of interest. The right and left thalamic NAA/Cr and Cho/ Cr ratios were compared first within the patient group and then between the control and patient groups. The differences in age and spectroscopic data between groups were assessed using the Mann-Whitney U test, whereas the comparison within groups between left thalamus and right thalamus was done by the Wilcoxon test. RESULTS: In patients with ET, the NAA/Cr ratio of the right thalamus was found to be significantly higher than the NAA/Cr ratio of the left thalamus (P= .02). However, NAA/Cr and Cho/Cr ratios were found to be similar (P> .05) when we compared the control and patient groups for the right thalamus and then the left thalamus. CONCLUSION: These data present preliminary evidence for metabolic alterations of the contralateral thalamus (namely, low NAA/Cr ratio) in ET patients with predominantly involved right arm. However, the series is small and further data are necessary to clear the subject adequately.