Anatomic basis of amygdaloid and hippocampal volume measurement by magnetic resonance imaging

Maternal responses to adolescent positive affect are associated with adolescents' reward neuroanatomy

The development of reward-based learning and decision-making, and the neural circuitry underlying these processes, appears to be influenced negatively by adverse child-rearing environments characterized by abuse and other forms of maltreatment. No research to-date has investigated whether normative variations in the child-rearing environment have effects on adolescent brain structure. We examined whether normative variations in maternal responses to adolescents' positive affective behavior were associated with morphometric measures of the adolescents' affective neural circuitry, namely the amygdala, orbitofrontal cortex (OFC), and anterior cingulate cortex (ACC). Healthy adolescents (N = 113) participated in laboratory-based interaction tasks with their mothers, and underwent high-resolution (3T) structural magnetic resonance imaging (MRI). The mother-adolescent interactions included a pleasant event-planning interaction (EPI) and a conflictual problem-solving interaction (PSI). Adolescents, whose mothers displayed more punishing responses to their positive affective behavior during both tasks, and only during the PSI, had larger left dorsal ACC and bilateral OFC volumes, respectively. In addition, boys whose mothers evidenced this pattern of behavior during the EPI had larger right amygdala volumes. These results suggest that normative variations in maternal responses to affective behavior are associated with the structural characteristics of adolescents' affective neural circuitry, which may have implications for the development of their social, cognitive and affective functioning.

Hippocampus volume and episodic memory in schizophrenia

Previous studies of schizophrenia have suggested a linkage between neuropsychological (NP) deficits and hippocampus abnormality. The relationship between hippocampus volume and NP functioning was investigated in 24 patients with chronic schizophrenia and 24 matched healthy controls. Overall intracranial, white and gray matter, and anterior (AH) and posterior (PH) hippocampus volumes were assessed from magnetic resonance images (MRI). NP domains of IQ, attention, and executive function were also evaluated with respect to volumetric measures. It was hypothesized that AH and PH volumes and episodic memory scores would be positively associated in controls and that the schizophrenia group would depart from this normative pattern. NP functioning was impaired overall and AH volume was smaller in the schizophrenia group. In the controls, the hippocampus-memory relationships involved AH and PH, and correlations were significant for verbal memory measures. In the schizophrenia group, positive correlations were constrained to PH. Negative correlations emerged between AH and verbal and visual memory measures. For both groups, cortical volume negatively correlated with age, but a negative correlation between age and hippocampus volume was found only in the schizophrenia group. In this sample of adults with schizophrenia, atypical relationships between regional hippocampus volumes and episodic memory ability were found, as was an atypical negative association between hippocampus volume and age.

MR-determined hippocampal asymmetry in full-term and preterm neonates

Hippocampi are asymmetrical in children and adults, where the right hippocampus is larger. To date, no literature has confirmed that hippocampal asymmetry is evident at birth. Furthermore, gender differences have been observed in normal hippocampal asymmetry, but this has not been examined in neonates. Stress, injury, and lower IQ have been associated with alterations to hippocampal asymmetry. These same factors often accompany preterm birth. Therefore, prematurity is possibly associated with altered hippocampal asymmetry. There were three aims of this study: First, we assessed whether hippocampi were asymmetrical at birth, second whether there was a gender effect on hippocampal asymmetry, and third whether the stress of preterm birth altered hippocampal asymmetry. This study utilized volumetric magnetic resonance imaging to compare left and right hippocampal volumes in 32 full-term and 184 preterm infants at term. Full-term infants demonstrated rightward hippocampal asymmetry, as did preterm infants. In the case of preterm infants, hippocampal asymmetry was proportional to total hemispheric asymmetry. This study is the first to demonstrate that the normal pattern of hippocampal asymmetry is present this early in development. We did not find gender differences in hippocampal asymmetry at term. Preterm infants tended to have less asymmetrical hippocampi than full-term infants, a difference which became significant after correcting for hemispheric brain tissue volumes. This study may suggest that hippocampal asymmetry develops in utero and is maintained into adulthood in infants with a normal neurological course.

Sodium MR imaging detection of mild Alzheimer disease: preliminary study

BACKGROUND AND PURPOSE

There is significant interest in the development of novel noninvasive techniques for the diagnosis of Alzheimer disease (AD) and tracking its progression. Because MR imaging has detected alterations in sodium levels that correlate with cell death in stroke, we hypothesized that there would be alterations of sodium levels in the brains of patients with AD, related to AD cell death.

MATERIALS AND METHODS

A total of 10 volunteers (5 with mild AD and 5 healthy control subjects) were scanned with a 20-minute sodium (23Na) MR imaging protocol on a 3T clinical scanner.

RESULTS

After normalizing the signal intensity from the medial temporal lobes corresponding to the hippocampus with the ventricular signal intensity, we were able to detect a 7.5% signal intensity increase in the brains of patients with AD (AD group, 68.25% +/- 3.4% vs control group, 60.75% +/- 2.9%; P < .01). This signal intensity enhancement inversely correlated with hippocampal volume (AD group, 3.22 +/- 0.50 cm3 vs control group, 3.91 +/- 0.45 cm3; r2 = 0.50).

CONCLUSIONS

This finding suggests that sodium imaging may be a clinically useful tool to detect the neuropathologic changes associated with AD.

Comorbid substance abuse and brain morphology in recent-onset psychosis

The aim of the presented study was to compare schizophrenia and schizoaffective patients early in the course of the disease with and without comorbid substance abuse disorder (SUD vs. NSUD) with regard to brain morphology. In a prospective design 41 patients (20 SUD vs. 21 NSUD) diagnosed as recent-onset schizophrenia or schizoaffective disorder consecutively admitted to hospital received standardized psychopathological evaluation (BPRS, SANS, MADRS, CGI, GAF) and MRI scanning with volumetric measurement of superior temporal gyrus (STG), amygdala-hippocampal complex, and cingulum. Patients with SUD (primarily cannabis) were significantly younger, predominantly male and had a lower socioeconomic status. Despite less attentional impairment (SANS subscore) and elevated anxiety/depression (BPRS subscore) in patients with SUD compared to NSUD, no other psychopathological differences could be detected. There were no differences in the assessed temporolimbic brain morphology between the two subgroups. In conclusion, in this study substance abuse in recent-onset psychosis had no effect on brain morphology and the earlier onset of psychosis in patients with comorbid SUD could not be explained by supposed accentuated brain abnormalities in temporolimbic regions.

Neuropsychological near normality and brain structure abnormality in schizophrenia

OBJECTIVE

Cognitive deficits are prominent in schizophrenia. Patients have an average score one standard deviation below normal on a broad spectrum of cognitive tests. It has been repeatedly noted, however, that 20%-25% of patients differ from this general pattern and score close to normal on neuropsychological testing. This study used brain morphometry to 1) identify brain abnormalities associated with more severe cognitive deficits and 2) help determine whether cognitively relatively intact patients perform better because they have less severe illness or because they have a different illness.

METHOD

Patients were assigned to a neuropsychologically near normal (N=21) subgroup if they scored within 0.5 standard deviation of healthy comparison subjects (N=30) on four tests of attention and verbal and nonverbal working memory, and to a neuropsychologically impaired (N=54) group if they scored at least 1.0 standard deviation below that of comparison subjects. Subgroup assignments were confirmed with the California Verbal Learning Test and degraded-stimulus Continuous Performance Test. Volumes of ventricular compartments, hippocampus, amygdala, thalamus, cerebellum, and regional cortical gray and white matter were dependent variables. Differences among groups were evaluated by using linear mixed-model multivariate analyses with gender, age, and height as covariates.

RESULTS

Both neuropsychologically near normal and neuropsychologically impaired patients had markedly smaller gray matter and larger third ventricle volumes than healthy comparison subjects. Only neuropsychologically impaired patients, however, had significantly smaller white matter and larger lateral ventricle volumes than healthy comparison subjects.

CONCLUSIONS

Although both neuropsychologically impaired and neuropsychologically near normal patients have marked neuropathology in their gray matter, the relative absence of white matter pathology in the neuropsychologically near normal group suggests the possibility of differences in the disease process.

Latent volumetric structure of the human brain: Exploratory factor analysis and structural equation modeling of gray matter volumes in healthy children and adults

Previous studies have investigated patterns of volumetric covariance (i.e. intercorrelation) among brain regions. Methodological issues, however, have limited the validity and generalizability of findings from these prior studies. Additionally, patterns of volumetric covariance have often been assumed to reflect the presence of structural networks, but this assumption has never been tested formally. We identified patterns of volumetric covariance, correlated these patterns with behavioral measures, and tested the hypothesis that the observed patterns of covariance reflect the presence of underlying networks. Specifically, we performed factor analysis on regional brain volumes of 99 healthy children and adults, and we correlated factor scores with scores on the Stroop Word-Color Interference Test. We identified four latent volumetric systems in each hemisphere: dorsal cortical, limbic, posterior, and basal ganglia. The positive correlation of the right posterior system with Stroop scores suggested that larger latent volumes are detrimental to inhibitory control. We also applied Structural Equation Modeling (SEM) to our dataset (n = 107) to test whether a model based on the anatomical pathways within cortico-striatal-thalamic-cortical (CSTC) circuits accounts for the covariances observed in our sample. The degree to which SEM predicted volumetric covariance in the CSTC circuit depended on whether we controlled for age and whole brain volume in the analyses. Removing the effects of age worsened the fit of the model, pointing to a possible developmental component in establishing connections within CSTC circuits. These modeling techniques may prove useful in the future for the study of structural networks in disease populations.

Temporal lobe epilepsy: differential pattern of damage in temporopolar cortex and white matter

Our purpose was to quantify structural changes of the temporopolar cortex (TPC) and its white matter (TPWM) in temporal lobe epilepsy (TLE) using MRI volumetry and texture analysis. We studied 23 patients with hippocampal atrophy, and 20 healthy controls. Gradient magnitude and entropy were calculated to model signal intensity blurring on T1-MRI. Two observers assessed signal changes and atrophy visually. Compared to controls, TLE patients had a decrease in TPC and TPWM volume ipsilateral to the seizure focus. The gradient magnitude and entropy were decreased ipsilateral to the focus only in TPWM, indicating blurring of this compartment. Eighty-seven percent of TLE patients had at least one volumetric or textural abnormality. Although sensitivity of visual and quantitative assessment of TPC atrophy was comparable (43 and 39%), specificity was higher for volumetry (54% vs. 95%). Compared to visual analysis of signal changes in TPWM on T1-MRI, texture metrics had higher sensitivity (65% vs. 17%) and specificity (100% vs. 69%). The proportion of patients with blurring of TPWM as determined by texture analysis was higher than that seen on visual inspection of T2 images (78% vs. 43%). We found no clear association between volumetric or textural changes of TPC and TPWM and outcome after surgery. Structural changes of the anatomically distinct TPC and TPWM are found ipsilateral to the seizure focus in the majority of TLE patients with hippocampal sclerosis. MRI post-processing allows dissociating different pathological tissue characteristics and shows that atrophy involves gray and white matter, whereas blurring is confined to white matter.

Hippocampal extracellular GABA correlates with metabolism in human epilepsy

As the major inhibitory neurotransmitter in human brain, GABA is an important modulator of hyperexcitability in epilepsy patients. Given the high energetic cost of neurotransmission and synaptic activity, GABA concentrations may be hypothesized to correlate with metabolic function. We studied human epilepsy patients undergoing intracranial EEG monitoring for seizure localization to examine microdialysis measures of extracellular GABA (ecGABA), pre-operative MR spectroscopic measures of neuronal mitochondrial function (NAA/Cr), and wherever possible, neuropathology and hippocampal volumetry. Two groups undergoing intracranial monitoring for seizure localization were studied: surgically treated hippocampal epilepsy (MTLE) and neocortical (non-hippocampal seizure onset) epilepsy. All data are hippocampal and thus these groups allow comparisons between the epileptogenic and non-epileptogenic regions. ecGABA was measured using in vivo microdialysis performed during intracranial monitoring. Pre-operative in vivo MR spectroscopic imaging was performed to measure the ratio of N-acetyl aspartate (NAA) to creatine. Standard methods for neuropathology and hippocampal volumetry were used. In the neocortical group, increased ecGABA correlated with greater NAA/Cr (R = +0.70, p < 0.015, n = 12) while in the MTLE group, increased ecGABA linked with decreased NAA/Cr (R = -0.94, p < 0.001, n = 8). In MTLE, ecGABA (increased) and NAA/Cr (decreased) correlated with increased glial cell numbers (R = +0.71, p < 0.01, n = 12, R = -0.76 p < 0.03 respectively). No relationship was seen between ecGABA and hippocampal volumes in either group. In epilepsy, ecGABA increases occur across a range of metabolic function. Outside the seizure focus, ecGABA and NAA/Cr increase together; in contrast, within the seizure focus, ecGABA increases with declining mitochondrial function.

Schizophrenia diagnosis and anterior hippocampal volume make separate contributions to sensory gating

Impaired P50 gating is thought to reflect a core deficit in schizophrenia, but the relevant neural network is not well understood. The present study used EEG and MEG to assess sensory gating and volumetric MRI to measure hippocampal volume to investigate relationships between them in 22 normal controls and 22 patients with schizophrenia. In the schizophrenia group, anterior but not posterior hippocampal volume was smaller, and both the P50 and M50 gating ratios were larger (worse) than in controls. Independent of group, left-hemisphere M50 gating ratio correlated negatively with left anterior hippocampal volume, and right-hemisphere M50 gating ratio correlated negatively with right anterior hippocampal volume. Schizophrenia diagnosis predicted M50 gating independent of hippocampal volume. These results are consistent with the finding that hippocampus is a critical part of a fronto-temporal circuit involved in auditory gating.

Preterm infant hippocampal volumes correlate with later working memory deficits

Children born preterm exhibit working memory deficits. These deficits may be associated with structural brain changes observed in the neonatal period. In this study, the relationship between neonatal regional brain volumes and working memory deficits at age 2 years were investigated, with a particular interest in the dorsolateral prefrontal cortex, parietal cortex and the hippocampus. While the eligible sample consisted of 227 very preterm children who were born at the Royal Women's Hospital, Melbourne prior to 30 weeks gestation or weighing <1250 g, 156 children had complete data sets. Neonatal magnetic resonance images of the brain were obtained at term equivalent age and subsequently parcellated into eight sub-regions, while the hippocampus was manually segmented. The relationship between brain volumes for these regions and performance on a working memory task (delayed alternation) at 2 years of age was examined. Very preterm children who perseverated on the working memory task had significantly smaller hippocampal volumes than very preterm children who exhibited intact working memory, even after adjusting for relevant perinatal, sociodemographic and developmental factors. Preterm children appear to have altered hippocampal volumes by discharge from hospital which may have a lasting impact on working memory function.

Structural and functional correlates of unilateral mesial temporal lobe spatial memory impairment

The aim of this study was to explore the effects of preoperative and postoperative lateralized mesial temporal damage on three measures of spatial learning: navigation, object location and plan drawing, and to determine the relationship between volumetry of the hippocampus and memory performance. Fifteen patients with well-characterized unilateral hippocampal sclerosis, 15 patients who had undergone unilateral anterior temporal lobectomy (ATL), and a comparison group consisting of 15 patients with idiopathic generalized epilepsy and 25 neurologically healthy participants explored a novel virtual environment. Volumetric analyses of both hippocampi were conducted on unilateral hippocampal sclerosis and idiopathic generalized epilepsy patients' T(1)-weighted magnetic resonance imaging scans. Performance of temporal lobe epilepsy (TLE) patients (either unilateral hippocampal sclerosis or anterior temporal lobectomy) on the different spatial memory variables, namely navigation, object location and plan drawing, was significantly worse relative to the comparison groups (either idiopathic generalized epilepsy or controls). Patients with right TLE did not differ from patients with left TLE on any of the spatial memory measures. An index of absolute hippocampal asymmetry did not correlate with any of the spatial memory measures. Together, our lesion and volumetry findings suggest that the domain of spatial memory is systematically related to the integrity of both right and left mesial temporal lobe, and is unlikely to be a strongly lateralized function. From the standpoint of cerebral organization (lateralization), the notion of material-specificity, which postulates that all components of verbal and spatial memory are lateralized in their entirety to the left and right hemispheres, respectively, requires modification. Instead it would appear that the notion of task-specificity is a more accurate description of patterns of lateralization of spatial memory.

Comparison of two different measurement techniques of hippocampal resection length in temporal lobe epilepsy: results of a prospective study

BACKGROUND

Magnetic resonance imaging (MRI) volumetry has evolved to a highly sensitive method for presurgical detection of hippocampal sclerosis in temporal lobe epilepsy (TLE). Seizure resolution and neuropsychological sequelae are believed to correlate with extent of resection. Therefore an easy volumetric method to determine extent of resection is desirable. The purpose of this work is to evaluate and compare two different measurement techniques for hippocampal resection length.

METHODS

Sixty-one patients with a mean seizure history of 25.1 years and medically intractable TLE were included. They underwent MRI with sagittal acquired 3D T1-weighted spoiled gradient recalled echo sequence in 1 mm(3) isotropic voxel. Hippocampal resection length was calculated with two different methods. In the slice counting method (SCM) the number of consecutive 1-mm-thick slices containing resected hippocampus formation was counted. In the vector method (VM) the sum of the oblique and thus longer distances between the centre points of segmented hippocampal areas on each MRI slice were calculated.

RESULTS

Since the hippocampus is a curved body, the resection lengths measured with VM were always larger than measured with SCM. The comparison of resection length expressed in "percent of total length" showed good agreement between the two methods, because unlike the absolute values of resection length, the percentage values are unaffected by the three-dimensional shape of the hippocampus.

CONCLUSION

The easier and quicker method of "slice counting" may be used to determine resection length expressed in "percent of total length", giving reliable values for resection length but causing less volumetric work.

Magnetic resonance imaging volumes of the hippocampus in drug-naïve patients with post-traumatic stress disorder without comorbidity conditions

Most brain imaging studies have showed smaller hippocampal volume in adults with chronic PTSD; however, some other studies have not replicated this finding. Most of these investigations included subjects with other psychiatric comorbidities, such as major depression or alcohol abuse. The prevalence of psychiatric comorbidities in PTSD is generally high and this makes it difficult, if not impossible, to disentangle the contribution of other disorders to hippocampal volume. Therefore, the main goal of the current study is to compare hippocampal volumes of healthy subjects and drug-naïve patients with PTSD caused by different types of mixed civilian traumas (i.e. car accident, physical abuse, sudden death of a family member, assault or robbery, natural disaster and traumatic abortion) and without comorbidity conditions. Magnetic resonance imaging (MRI) was used to measure the hippocampi, total cerebrum, gray matter, white matter and cerebrospinal fluid volumes in 34 patients with single diagnosis of PTSD, and 34 case-matched non-PTSD comparison subjects. The patients with single diagnosis of PTSD had an 11.8% smaller left hippocampus (p<0.001) and an 8.7% smaller right hippocampus (p=0.003) than the healthy controls. The results were controlled for the total brain volume and for gray matter volumes. Subjects with PTSD also displayed lower overall gray matter volume (p=0.006). There were no significant correlations between hippocampal volumes and illness duration or severity of PTSD. The findings indicate the presence of smaller hippocampal volumes in drug-naïve patients with single diagnosis of PTSD, compared with healthy subjects.

Relationship between post-operative depression/anxiety and hippocampal/amygdala volumes in temporal lobectomy for epilepsy

PURPOSE

Patients with temporal lobe epilepsy (TLE) often present mood disturbances, which may either exacerbate or remit following surgery. The objective of the study was to investigate the relationship between post-operative depressive/anxiety symptoms and hippocampal/amygdala volumes following anterior temporal lobectomy.

METHODS

Thirty-five patients operated for TLE were assessed for mood disturbances by the Beck depression inventory (BDI) and Beck anxiety inventory (BAI). Post-operative MRI data were collected and volumetric analysis of the hippocampi (HV) and amygdala (AV) was performed. Correlations between volumetric data, measures of mood, and demographic and clinical data were calculated.

RESULTS

BDI scores significantly correlated with the intact HV (p=0.029) as well as the absolute difference between the intact and remnant HV (p=0.021). This was evident in left-side resections (p=0.049); in right-side resections the correlation was marginally non- significant (p=0.057). Depressed patients also had smaller remnant AV (p=0.002). Furthermore, BAI was negatively correlated with the HV remnant in left-side resections (p=0.038). No other significant associations between post-operative mood disturbances and various demographic and clinical variables were observed.

CONCLUSION

The severity of depressive symptomatology in operated epilepsy patients correlates with the extent of hippocampal and amygdala resection; this association appears to be more evident in left-side resections.

Neuroanatomical correlates of temperament in early adolescents

OBJECTIVE

Temperament refers to enduring behavioral characteristics that underpin individual differences in human behavior, including risk for psychopathology. Research attempting to investigate the neurobiological basis of temperament represents an important step toward elucidating the biological mechanisms underlying these individual differences. In the present study, we examined the relation between four core temperament dimensions and anatomically defined regions of the limbic and prefrontal cortices.

METHOD

We used a cross-sectional design to examine a large sample (N = 153; mean age 12.6 years, SD 0.4, range 11.4-13.7) of healthy early adolescents who were selected from a larger sample to maximize variation in temperament. The main outcome measures were psychometric measures of temperament (four factors: effortful control, negative affectivity, surgency, and affiliativeness) based on the Early Adolescent Temperament Questionnaire-Revised, and volumetric measures of a priori brain regions of interest (anterior cingulate cortex [ACC], orbitofrontal cortex, amygdala, and hippocampus).

RESULTS

We found regional brain volumes to account for small but significant amounts of the variance in self-reported temperament scores. Specifically, higher effortful control was associated with larger volume of the left orbitofrontal cortex and hippocampus. Higher negative affectivity was associated with smaller volume of the left dorsal paralimbic relative to limbic portion of the ACC. Higher affiliativeness was associated with larger volume of the right rostral/ventral limbic portion of the ACC. Affiliativeness and surgency also showed a number of female-specific associations, primarily involving the rostral/ventral ACC.

CONCLUSIONS

Our results provide support for a neuroanatomical basis for individual differences in temperament and have implications for understanding the neurobiological mechanisms underlying the development of a number of psychiatric disorders.

Age-dependent reduction of amygdala volume in bipolar disorder

The amygdala is hypothesized to play a critical role in mood regulation, yet its involvement in bipolar disorder remains unclear. The aim of the present study was to compare measurements of amygdala volumes in a relatively large sample of bipolar disorder patients and healthy controls ranging in age from 18 to 49 years. Subjects comprised 54 adult patients meeting DSM-IV criteria for bipolar disorder and 41 healthy controls matched for age, sex, and education. Magnetic resonance imaging (1.5 T) was performed to obtain volumetric measurements of the amygdala using a manual region-of-interest tracing method with software that allowed simultaneous visualization of the amygdala in three orthogonal planes. The anterior head of the hippocampus was removed in the sagittal plane prior to amygdala volumetry measurement. Multiple regression analysis was computed on amygdala volume measurements as a function of diagnosis, age, sex, and cerebral volume. Bipolar patients showed an age-related reduction of amygdala volume, but controls did not. Among bipolar subjects, amygdala volume was unrelated to medication history. There were no significant hemispheric or sex interactions with the main effects. Results support a role for amygdala dysfunction in bipolar disorder which appears most robustly in older relative to younger adult patients. Differential aging effects in bipolar disorder may compromise amygdala integrity and contribute to mood dysregulation.

Decreased hippocampal volume on MRI is associated with increased extracellular glutamate in epilepsy patients

PURPOSE

Temporal lobe epilepsy (TLE) is associated with smaller hippocampal volume and with elevated extracellular (EC) glutamate levels. We investigated the relationship between the hippocampal volume and glutamate in refractory TLE patients.

METHODS

We used quantitative MRI volumetrics to measure the hippocampal volume and zero-flow microdialysis to measure the interictal glutamate, glutamine, and GABA levels in the epileptogenic hippocampus of 17 patients with medication-resistant epilepsy undergoing intracranial EEG evaluation. The relationships between hippocampal volume, neurochemical levels, and relevant clinical factors were examined.

RESULTS

Increased EC glutamate in the epileptogenic hippocampus was significantly related to smaller ipsilateral (R(2)= 0.75, p < 0.0001), but not contralateral hippocampal volume when controlled for glutamine and GABA levels, and for clinical factors known to influence hippocampal volume. Glutamate in the atrophic hippocampus was significantly higher (p = 0.008, n = 9), with the threshold for hippocampal atrophy estimated as 5 microM. GABA and glutamine levels in the atrophic and nonatrophic hippocampus were comparable. Decreased hippocampal volume was related to higher seizure frequency (p = 0.008), but not to disease duration or febrile seizure history. None of these clinical factors were related to the neurochemical levels.

CONCLUSIONS

We provide evidence for a significant association between increased EC glutamate and decreased ipsilateral epileptogenic hippocampal volume in TLE. Future work will be needed to determine whether the increase in glutamate has a causal relationship with hippocampal atrophy, or whether another, yet unknown factor results in both. This work has implications for the understanding and treatment of epilepsy as well as other neurodegenerative disorders associated with hippocampal atrophy.

Amygdala volume in patients receiving chronic corticosteroid therapy

BACKGROUND

Hippocampal volume reduction and declarative memory deficits are reported in humans and animals exposed to exogenous corticosteroids. The amygdala is another brain structure involved in the stress response that has important interactions with the hypothalamic-pituitary-adrenal axis. To our knowledge, no studies in animals or humans have examined the impact of exogenous corticosteroid administration on the amygdala. We assessed amygdala volume in patients receiving chronic prescription corticosteroid therapy and control subjects with similar medical histories not receiving corticosteroids.

METHODS

Fifteen patients on long-term prednisone therapy and 13 control subjects of similar age, gender, ethnicity, education, height, and medical history were assessed with magnetic resonance imaging. Amygdala volume was manually traced and compared between groups using a two-way analysis of variance (ANOVA). Correlations between amygdala volume, age, and corticosteroid dose/duration were assessed using Pearson's correlation coefficient.

RESULTS

Compared with control subjects, corticosteroid-treated patients had significantly smaller amygdala volumes. Right amygdala volume correlated significantly with age in control subjects and with duration of corticosteroid therapy in patients.

CONCLUSIONS

Patients receiving chronic corticosteroid therapy had smaller amygdala volumes than control subjects that correlated with duration of corticosteroid therapy. These findings suggest that corticosteroid exposure may be associated with changes in the amygdala as well as hippocampus.

Rhinal cortex asymmetries in patients with mesial temporal sclerosis

PURPOSE

The rhinal cortex, comprising the entorhinal (ErC) and perirhinal (PrC) cortices, is one component of the limbic system that may be affected in patients with epilepsy and other temporal lobe pathologies. This study extended quantitative examination of the limbic system through development and validation of volumetric protocols to measure the ErC and PrC.

METHODS

Volumes were calculated from MRI studies using ANALYZE 7.5 and based on detailed anatomical definitions developed for the study. Subjects were 61 temporal lobe epilepsy patients with mesial temporal sclerosis (MTS: 33 left, 28 right) and 20 neurologically normal controls. Inter-rater reliabilities for the ErC and PrC volume protocols were found to be high (range 0.86-0.92).

RESULTS

Ipsilateral hippocampal volume was reduced in patients with MTS, while contralateral volume did not differ significantly from controls. In the patients, rhinal cortex volumes were reduced as a function of laterality of disease. The pattern of correlations between ErC and PrC differed between disease groups. Hippocampal and rhinal cortex volumes were not significantly correlated. A significant four-way interaction was found between side of MTS, hemisphere, structure and handedness.

CONCLUSIONS

This quantitative study demonstrates reliable in vivo evidence of morphometric changes in ErC and PrC in a substantial number of patients with unilateral MTS. The relationship observed between handedness, structure and disease status may suggest a role for cerebral dominance in modulating the expression of MTS.

Hippocampal neurochemistry, neuromorphometry, and verbal memory in nondemented older adults

BACKGROUND

Characterization of the behavioral correlates of neuromorphometry and neurochemistry in older adults has important implications for an improved understanding of the aging process. The objective of this study was to test the hypothesis that a measure of hippocampal neuronal metabolism was associated with verbal memory in nondemented older adults after controlling for hippocampal volume.

METHODS

4-T MRI, proton magnetic resonance spectroscopy ((1)H MRS), and neuropsychological assessment were conducted in 48 older adults (23 women; mean age 81 years). Average hippocampal N-acetyl aspartate/creatine ratios (NAA/Cr) and hippocampal volumes were obtained. Neuropsychological evaluation included tests of verbal memory (Buschke and Grober Free and Cued Selective Reminding Test-Immediate Recall [FCSRT-IR], Wechsler Memory Scale-Revised Logical Memory subtest) and attention and executive function (Trail Making Test Parts A and B).

RESULTS

Linear regression analysis indicated that after adjusting for age, hippocampal NAA/Cr was a significant predictor of FCSRT-IR performance (beta = 0.38, p = 0.01, R (2) = 0.21). Hippocampal volume was also a significant predictor of FCSRT-IR performance after adjusting for age and midsagittal area (beta = 0.47, p = 0.01, R (2) = 0.24). In a combined model, hippocampal NAA/Cr (beta = 0.33, p = 0.03) and volume (beta = 0.35, p = 0.03) were independent predictors of FCSRT-IR performance, accounting for 30% of the variance in memory.

CONCLUSIONS

These findings indicate that nondemented older adults with smaller hippocampal volumes and lower levels of hippocampal N-acetyl aspartate/creatine ratio metabolites perform more poorly on a test of verbal memory. The integrity of both the structure and metabolism of the hippocampus may underlie verbal memory function in nondemented elderly.

Correlation between voxel based morphometry and manual volumetry in magnetic resonance images of the human brain

This is a comparative study between manual volumetry (MV) and voxel based morphometry (VBM) as methods of evaluating the volume of brain structures in magnetic resonance images. The volumes of the hippocampus and the amygdala of 16 panic disorder patients and 16 healthy controls measured through MV were correlated with the volumes of gray matter estimated by optimized modulated VBM. The chosen structures are composed almost exclusively of gray matter. Using a 4 mm Gaussian filter, statistically significant clusters were found bilaterally in the hippocampus and in the right amygdala in the statistical parametric map correlating with the respective manual volume. With the conventional 12 mm filter,a significant correlation was found only for the right hippocampus. Therefore,narrowfilters increase the sensitivity of the correlation procedure, especially when small brain structures are analyzed. The two techniques seem to consistently measure structural volume.

Prefrontal and amygdala volumes are related to adolescents' affective behaviors during parent-adolescent interactions

Adolescence is a key period for the development of brain circuits underlying affective and behavioral regulation. It remains unclear, however, whether and how adolescent brain structure influences day-to-day affective behavior. Because of significant changes in the nature of family relations that also typically occur during adolescence, parent-child interactions provide a meaningful context where affective behavior and its regulation may be assessed. In a sample of 137 early adolescents, we investigated the relationship between aspects of the adolescents' brain structure and their affective behavior as assessed during observation of parent-child interactions. We found a significant positive association between volume of the amygdala and the duration of adolescent aggressive behavior during these interactions. We also found male-specific associations between the volume of prefrontal structures and affective behavior, with decreased leftward anterior paralimbic cortex volume asymmetry associated with increased duration of aggressive behavior, and decreased leftward orbitofrontal cortex volume asymmetry associated with increased reciprocity of dysphoric behavior. These findings suggest that adolescent brain structure is associated with affective behavior and its regulation in the context of family interactions, and that there may be gender differences in the neural mechanisms underlying affective and behavioral regulation during early adolescence. Particularly as adolescence marks a period of rapid brain maturation, our findings have implications for mental health outcomes that may be revealed later along the developmental trajectory.

Reduced GABAA benzodiazepine receptor binding in veterans with post-traumatic stress disorder

Gamma-aminobutyric acid (GABA(A)) receptors are thought to play an important role in modulating the central nervous system in response to stress. Animal data have shown alterations in the GABA(A) receptor complex by uncontrollable stressors. SPECT imaging with benzodiazepine ligands showed lower distribution volumes of the benzodiazepine-GABA(A) receptor in the prefrontal cortex of patients with post-traumatic stress disorder (PTSD) in one, but not in another study. The objective of the present study was to assess differences in the benzodiazepine-GABA(A) receptor complex in veterans with and without PTSD using [(11)C]flumazenil and positron emission tomography (PET). Nine drug naive male Dutch veterans with deployment related PTSD and seven male Dutch veterans without PTSD were recruited, and matched for age, region and year of deployment. Each subject received a [(11)C]flumazenil PET scan and a structural magnetic resonance imaging scan. Dynamic 3D PET scans with a total duration of 60 min were acquired, and binding in template based and manually defined regions of interest (ROI) was quantified using validated plasma input and reference tissue models. In addition, parametric binding potential images were compared on a voxel-by-voxel basis using statistical parametric mapping (SPM2). ROI analyses using both template based and manual ROIs showed significantly reduced [(11)C]flumazenil binding in PTSD subjects throughout the cortex, hippocampus and thalamus. SPM analysis confirmed these results. The observed global reduction of [(11)C]flumazenil binding in patients with PTSD provides circumstantial evidence for the role of the benzodiazepine-GABA(A) receptor in the pathophysiology of PTSD and is consistent with previous animal research and clinical psychopharmacological studies.

Bilateral hippocampal volume increase in patients with bipolar disorder and short-term lithium treatment

Most previous magnetic resonance imaging (MRI) studies of patients with bipolar disorder (BD) report similar hippocampus (HC) volumes across patients and controls, but because patients studied were heterogeneous with respect to course of illness variables and medication status, the conclusions of these studies remain equivocal. Lithium (Li) is the reference-standard drug for BD and its role as an important agent in neuroprotection and neurogenesis has been documented in human and in animal studies. We compared the volume of the HC, hippocampal head (Hh), and body/tail (Hbt) in three groups with no history of medication use before entry into this study: (a) a group of patients treated with Li for 1-8 weeks and then scanned; (b) a group comprised of patients who were unmedicated at the time of scan; and (c) a group of patients treated with either valproic acid or lamotrigine. Healthy age- and sex-matched comparison subjects were also scanned. HC volumes did not differ between the unmedicated and healthy comparison groups. There was a bilateral increase in volumes of HC and Hh in the Li-treated group compared to the unmedicated group, an effect that was apparent even over a brief treatment period. Our study provides further confirmation that Li can exert structural effects on the HC, which are detectable in vivo. The study emphasizes the need to control for even brief exposure to medication in volumetric studies of the HC.

Morphologic features of the amygdala and hippocampus in children and adults with Tourette syndrome

CONTEXT

Limbic portions of cortical-subcortical circuits are likely involved in the pathogenesis of Tourette syndrome (TS). They are anatomically, developmentally, neurochemically, and functionally related to the basal ganglia, and the basal ganglia are thought to produce the symptoms of tics, obsessive-compulsive disorder, and attention-deficit/hyperactivity disorder that commonly affect persons with TS.

OBJECTIVE

To study the morphologic features of the hippocampus and amygdala in children and adults with TS.

DESIGN

A cross-sectional, case-control study using anatomical magnetic resonance imaging.

SETTING

University research center.

PARTICIPANTS

A total of 282 individuals (154 patients with TS and 128 controls) aged 6 to 63 years.

MAIN OUTCOME MEASURES

Volumes and measures of surface morphologic features of the hippocampus and amygdala.

RESULTS

The overall volumes of the hippocampus and amygdala were significantly larger in the TS group. Surface analyses suggested that the increased volumes in the TS group derived primarily from the head and medial surface of the hippocampus (over the length of the dentate gyrus) and the dorsal and ventral surfaces of the amygdala (over its basolateral and central nuclei). Volumes of these subregions declined with age in the TS group but not in controls, so the subregions were significantly larger in children with TS but significantly smaller in adults with TS than in their control counterparts. In children and adults, volumes in these subregions correlated inversely with the severity of tic, obsessive-compulsive disorder, and attention-deficit/hyperactivity disorder symptoms, suggesting that enlargement of the subregions may have a compensatory and neuromodulatory effect on tic-related symptoms.

CONCLUSION

These findings are consistent with the known plasticity of the dentate gyrus and with findings from previous imaging studies suggesting the presence of failed compensatory plasticity in adults with TS who have not experienced the usual decline in symptoms during adolescence.

Increased Fast ripple to ripple Ratios Correlate with Reduced Hippocampal Volumes and Neuron Loss in Temporal Lobe Epilepsy Patients

PURPOSE

To determine whether hippocampal sclerosis might form an anatomical substrate for pathological high-frequency oscillations in patients with temporal lobe epilepsy (TLE).

METHODS

Intracerebral wide bandwidth electroencephalogram was recorded in patients with medically intractable complex partial seizures. A computer-automated program detected interictal normal ripples (80-150 Hz) and pathologic fast ripples (FR, 151-500 Hz) from microelectrodes within hippocampus, entorhinal, and subicular cortices. Hippocampal MRI volumetric analysis and cell density measurements were correlated with rates of FR and ripple discharge.

RESULTS

In all 13 patients, higher rates of FR (p = 0.03) and ratios of FR to ripple discharges (p = 0.02) were observed in sites ipsilateral to seizure onset compared with rates within contralateral non-ictal sites. Higher ratios of FR to ripple discharge were associated with smaller ipsilateral hippocampal volumes (p = 0.02) and lower fascia dentata (FD; p = 0.02) and Ammon's horn (p = 0.0005) neuron densities. While reduced FD and Ammon's horn neuron densities correlated with higher ratios of discharges, stepwise multiple regression analysis revealed that decreased neuron densities within CA1 and prosubiculum regions most strongly predicted ratios of FR to ripples (r(2)= 0.78, p = 0.008).

CONCLUSIONS

In surgical patients with TLE, higher ratios of FR to ripple discharges are associated with histopathologic changes found in hippocampal sclerosis. These findings support the hypothesis that pathological alterations linked with hippocampal cell loss and synaptic reorganization promote FR and reduce ripple generation.

Major depression in temporal lobe epilepsy with hippocampal sclerosis: clinical and imaging correlates

PURPOSE

Refractory temporal lobe epilepsy (TLE) is often associated with hippocampal sclerosis (HS). Patients with major depression (MD) may also show structural abnormalities in the limbic system. Co-occurrence of TLE with HS and MD is not uncommon. We have investigated the clinical and morphological characteristics of TLE patients in relation to MD.

METHODS

34 TLE patients with HS were assessed at a Comprehensive Epilepsy Programme. All relevant clinical data were obtained, including the history of antecedent events to epilepsy. MD was diagnosed based on detailed psychiatric investigation. MRI was used to measure the volume and tissue signal (T2 relaxometry) of the hippocampus and amygdala. The imaging data were expressed as a percentage of the values obtained in a series of 55 controls.

RESULTS

A history of MD was present in 15 (44%) of 34 patients. Patients with MD had a longer duration of their epilepsy (p<0.05) and a lower frequency of antecedent events (13% with MD, 58% without MD, p<0.05). Both groups had a similar degree of ipsilateral HS (small hippocampal volume, increased hippocampal T2 relaxation time) and demonstrated bilateral amygdaloid atrophy. However, the contralateral amygdala showed lower signal in the presence of MD (97 (9) ms; no MD 103 (8) ms; ANCOVA, p = 0.02).

CONCLUSION

The integrity of the amygdala may influence mood disturbances in TLE patients with HS, as depression was associated with a relative preservation of the contralateral amygdala. In contrast, hippocampal abnormalities were not related to the presence of depression.

Impaired facial emotion recognition and reduced amygdalar volume in schizophrenia

Structural abnormalities of the amygdala and impaired facial emotion recognition have been reported in schizophrenia. Most studies demonstrated reduced amygdalar volumes in schizophrenia patients, and difficulty in recognizing negative facial emotions has also been reported. However, findings on the deficit in facial emotion recognition have been inconsistent, and the relationships between this impairment and amygdalar volume reduction remain unclear. In this study, we investigated these relationships by performing volumetric analysis of the amygdala and evaluation of facial emotion recognition performance in the same subjects with schizophrenia. The sample group comprised 20 schizophrenia patients and 20 matched healthy controls. We measured the volumes of the amygdalae with high-resolution magnetic resonance imaging (MRI) at 3.0 Tesla. Additionally, we included a task that evaluated the subjects' ability to recognize the intensity of basic facial emotions. We found that impaired facial emotion recognition in schizophrenia patients is emotion-specific (sadness, surprise, disgust, and anger). Moreover, the volume of each amygdala on either side of the brain was reduced. Finally, we found a correlation between left amygdalar volume and the recognition of sadness in facial expressions. This study demonstrated that amygdala dysfunction may contribute to impaired facial emotion recognition in schizophrenia.

Automated measurement of hippocampal atrophy using fluid-registered serial MRI in AD and controls

OBJECTIVE

To assess hippocampal atrophy rates calculated from fluid registration methods.

METHODS

Hippocampi were segmented on baseline and registered-repeat scans of 32 probable Alzheimer disease (AD) subjects and 55 controls. Fluid-based atrophy rates were calculated.

RESULTS

In AD patients, the mean (SD) atrophy rates for manual, fluidly propagated, and Jacobian methods were 5.09 (3.59), 5.34 (3.43), and 3.55 (2.70) (percentage per year). In controls, atrophy rates were 1.31 (2.00), 0.89 (0.75), and 0.56 (1.12) (percentage per year). In AD, fluid propagation and manual rates were similar in means (P = 0.55) and variances (P = 0.71). Jacobian rates were smaller in mean (P = 0.002) and variance (P = 0.026) than in manual rates. In controls, fluid-propagated rates were similar in mean to manual rates (P = 0.12), but less variable (P < 0.0001). Jacobian rates were smaller in mean (P = 0.014) and less variable (P < 0.0001) than in manual rates. Both fluid methods were superior to manual measures in separating AD from controls (P < 0.0001).

CONCLUSIONS

Fluid-based methods may be useful in large serial hippocampal studies.

Hippocampal volume measurement in patients with Ménière's disease: a pilot study

CONCLUSION

No signs of chronic stress as in hippocampal atrophy were present in patients with Ménière's disease.

OBJECTIVE

To evaluate the effect of chronic stress (allostatic load) by measuring hippocampal volume in patients with Ménière's disease.

SUBJECTS AND METHODS

Ten patients with Meniere's disease and 10 healthy controls were evaluated for absolute and relative hippocampal volumes measured on MRI scans, saliva cortisol levels and frequency of daily stressors. The study was performed in a prospective, controlled setting with two raters who were blinded as to subject identity.

RESULTS

Saliva cortisol levels and presence of daily stressor scores were similar in both groups. The first rater measured mean hippocampal volumes of 2.80 +/- 0.36 cm3 vs 3.15 +/- 0.52 cm3 (right) and 2.49 +/- 0.32 cm3 vs 3.06 +/- 0.46 cm3 (left), for the Ménière's disease and control group, respectively. The second rater measured 3.44 +/- 0.35 cm3 vs 3.60 +/- 0.52 cm3 (right) and 3.00 +/- 0.40 cm3 vs 3.42 +/- 0.45 cm3 (left), respectively. The volume of the left hippocampus was significantly smaller in patients with Ménière's disease compared with the controls for both raters (p < 0.05) and the right hippocampal volume was not different between the two groups. With correction for variation in head size (partial brain and partial intracranial volume) no significant differences in relative hippocampal volumes were observed between patients with Ménière's disease and the control group.

Hippocampal volume reduction and HPA-system activity in major depression

Structural imaging studies investigating hippocampal volumes in patients suffering from major depression have yielded mixed results. Here, 24 unipolar depressed in-patients and 14 healthy controls carefully matched for age, gender, and years of education underwent quantitative magnetic resonance imaging (MRI). Saliva cortisol was measured at 0800 and 1600 h in patients during a one-week wash-out and the following 4 weeks. Hippocampal volumes were significantly reduced in the patient group even after adjusting for intracranial brain volume (ICV) and age. Across groups, age was significantly negatively correlated with uncorrected hippocampal volumes. In patients, severity of disease (baseline HAMD scores) and baseline cortisol levels were not related to hippocampal volumes. However, there was a negative association between duration of the index episode before hospitalization and hippocampal volumes. Additionally, hippocampal volumes were significantly negatively correlated with duration of illness. Finally, we observed a trend for higher hippocampal volumes in those patients who showed a subsequent decrease in cortisol levels under pharmacotherapy.

Chronic insomnia and MRI-measured hippocampal volumes: a pilot study

STUDY OBJECTIVES

Morphometric analysis of magnetic resonance imaging brain scans was used to investigate possible neuroanatomic differences between patients with primary insomnia compared to good sleepers.

DESIGN

MRI images (1.5 Tesla) of the brain were obtained from insomnia patients and good sleepers. MRI scans were analyzed bilaterally by manual morphometry for different brain areas including hippocampus, amygdala, anterior cingulate, orbitofron-tal and dorsolateral prefrontal cortex.

SETTING

University Hospital Sleep Center and Radiology Department

PARTICIPANTS

8 unmedicated physician-referred patients with chronic primary insomnia (3 males, 5 females; 48.4 + 16.3 years) and 8 good sleepers matched for age, sex, body mass index, and education.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

Patients with primary insomnia demonstrated significantly reduced hippocampal volumes bilaterally compared to the good sleepers. None of the other regions of interest analyzed revealed differences between the 2 groups.

CONCLUSIONS

These pilot data raise the possibility that chronic insomnia is associated with alterations in brain structure. Replication of the findings in larger samples is needed to confirm the validity of the data. The integration of structural, neuropsychological, neuroendocrine and polysomnographic studies is necessary to further assess the relationships between insomnia and brain function and structure.

Cortisol levels in relation to hippocampal sub-regions in subjects with first episode schizophrenia

The etiology of hippocampal volumetric reductions in schizophrenia is largely unknown. In addition to genetic factors, environmental factors might also play a role. High levels of glucocorticoids are known to affect hippocampal volume in disorders such as Cushing's syndrome, but the relationship between cortisol and hippocampal volumes has not been studied in schizophrenia. We obtained diurnal salivary cortisol levels and MRI images to explore the link between cortisol levels and regional hippocampal volumes in healthy controls (N=29) and subjects with first episode schizophrenia (N=16) at the time of first admission. T1-weighted coronal MR images (slice thickness=1.5 mm) were acquired through the whole head using a 3D Fast SPGR IR Prep sequence on a 1.5 T GE imaging system. Using ANOVA, cumulative daily cortisol exposure calculated as area under the curve for each subject revealed significantly higher cortisol levels in the patient group [F(1,43)=4.4 p=0.04]. However, there were no statistically significant associations between the cortisol measures and regional hippocampal volumes in the subjects, except a trend level link between anterior hippocampal volume and cortisol in the positive direction, in parallel to previous findings in healthy adolescents. Our findings do not suggest a robust association between cortisol levels and hippocampal volumes in a first episode schizophrenia sample. Larger scale studies are needed to conclude a link between the two measures, yet it is possible that the negative association that was previously shown in other disorders may not apply to schizophrenia.

Correlates of intellectual ability with morphology of the hippocampus and amygdala in healthy adults

Several prior imaging studies of healthy adults have correlated volumes of the hippocampus and amygdala with measures of general intelligence (IQ), with variable results. In this study, we assessed correlations between volumes of the hippocampus and amygdala and full-scale IQ scores (FSIQ) using a method of image analysis that permits detailed regional mapping of this correlation throughout the surface contour of these brain structures. We delineated the hippocampus and amygdala in high-resolution magnetic resonance images of the brain from 34 healthy individuals. We then correlated FSIQ with overall volumes and with the surface morphologies of each of these structures. Hippocampus volumes correlated significantly and inversely with FSIQ independently of gender, age, socioeconomic status, and whole brain volume. Left and right hippocampus volumes correlated respectively with verbal and performance IQ subscales. Higher IQs were significantly associated with large inward deformations of the surface of the anterior hippocampus bilaterally. These findings suggest that a smaller anterior hippocampus contributes to an increased efficiency of neural processing that subserves overall intelligence.

Three-dimensional volumetric analysis and reconstruction of amygdala and hippocampal head, body and tail

Volumetric changes in the amygdala and hippocampus are relevant to many disorders, but their close proximity makes it difficult to separate these structures by magnetic resonance imaging, leading many volumetric protocols to exclude problematic slices from analysis, or to analyze the amygdalo-hippocampal complex conjointly. The hippocampus tail is also often excluded, because of the difficulty in separating it from the thalamus. We have developed a reliable protocol for volumetric analysis and 3-D reconstruction of the amygdala and hippocampus (as a whole and in its anatomical parts). Twenty volunteers from clinical and healthy populations were recruited. T1-weighted images were acquired at 1.5 Tesla with native spatial resolution of 1.5 mm x 1.0 mm x 1.0 mm. Volumetric analyses were performed blind to diagnosis, using the interactive software package DISPLAY. Inter-rater (intrarater) intraclass correlations for the method were: 0.95 (0.88) for hippocampus tail, 0.83 (0.93) for hippocampus body, 0.95 (0.92) for hippocampus head, 0.96 (0.86) for total hippocampus and 0.86 (0.94) for amygdala. Volumes (mean+/-S.D.) corrected for intracranial volume for this mixed group were for the hippocampal tail: 0.325+/-0.087 cm(3); hippocampal body: 0.662+/-0.120 cm(3); hippocampal head: 1.23+/-0.174 cm(3); total hippocampus: 2.218+/-0.217 cm(3), and amygdala: 0.808+/-0.185 cm(3). In conclusion, the study demonstrates that the amygdala and hippocampal parts can be quantified reliably.

Automatic volumetric measurement of segmented brain structures on magnetic resonance imaging

PURPOSE

The purpose of this study was to produce a fully automatic volumetric segmented brain image system (AVSIS) and to evaluate its utility for measuring hippocampal volumes and total intracranial volume (TIV).

MATERIALS AND METHODS

We developed a combination technique comprising an anatomical standardization technique to measure TIV, whole brain volume (WBV), and hippocampal volume obtained by magnetic resonance (MR) imaging. Altogether, 15 healthy volunteers and 15 patients with Alzheimer's disease (AD) underwent three-dimensional spoiled gradient echo (3D-SPGR) imaging. Three measurements were performed by manual volumetry as the gold standard, a previous semiautomatic method, and our new method, AVSIS.

RESULTS

WBV and hippocampal volume in the AD group were significantly smaller than those in the healthy volunteer group measured by the semiautomatic method, manual method, and AVSIS. Each volume measured by AVSIS or semiautomatic method correlated with that measured by the manual method. The correlation coefficients between TIVs, WBVs, or hippocampal volumes measured by AVSIS and the manual method were 0.910, 0.902, and 0.918, respectively; the correlation coefficients between TIVs, or WBVs, measured by the previous semiautomatic method and the manual method were 0.875, and 0.886, respectively.

CONCLUSION

We developed a system for a fully automatic measurement of segmented brain structures and obtained good results.

Hippocampal volume and shape analysis in an older adult population

This report presents a manual segmentation protocol for the hippocampus that yields a reliable and comprehensive measure of volume, a goal that has proven difficult with prior methods. Key features of this method include alignment of the images in the long axis of the hippocampus and the use of a three-dimensional image visualization function to disambiguate anterior and posterior hippocampal boundaries. We describe procedures for hippocampal volumetry and shape analysis, provide inter- and intra-rater reliability data, and examine correlates of hippocampal volume in a sample of healthy older adults. Participants were 40 healthy older adults with no significant cognitive complaints, no evidence of mild cognitive impairment or dementia, and no other neurological or psychiatric disorder. Using a 1.5 T GE Signa scanner, three-dimensional spoiled gradient recalled acquisition in a steady state (SPGR) sequences were acquired for each participant. Images were resampled into 1 mm isotropic voxels, and realigned along the interhemispheric fissure in the axial and coronal planes, and the long axis of the hippocampus in the sagittal plane. Using the BRAINS program (Andreasen et al., 1993), the boundaries of the hippocampus were visualized in the three orthogonal views, and boundary demarcations were transferred to the coronal plane for tracing. Hippocampal volumes were calculated after adjusting for intracranial volume (ICV). Intra- and inter-rater reliabilities, measured using the intraclass correlation coefficient, exceeded .94 for both the left and right hippocampus. Total ICV-adjusted volumes were 3.48 (+/-0.43) cc for the left hippocampus and 3.68 (+/-0.42) for the right. There were no significant hippocampal volume differences between males and females (p > .05). In addition to providing a comprehensive volumetric measurement of the hippocampus, the refinements included in our tracing protocol permit analysis of changes in hippocampal shape. Shape analyses may yield novel information about structural brain changes in aging and dementia that are not reflected in volumetric measurements alone. These and other novel directions in research on hippocampal function and dysfunction will be facilitated by the use of reliable, comprehensive, and consistent segmentation and measurement methods.

Odor processing in multiple chemical sensitivity

Multiple chemical sensitivity (MCS) is characterized by somatic distress upon exposure to odors. As in other idiopathic environmental intolerances, the mechanisms behind the reported hypersensitivity are unknown. Using the advantage of the well-defined trigger (odor), we investigated whether subjects with MCS could have an increased odor-signal response in the odor-processing neuronal circuits. Positron emission tomography (PET) activation studies with several different odorants were carried out in 12 MCS females and 12 female controls. Activation was defined as a significant increase in regional cerebral blood flow (rCBF) during smelling of the respective odorant compared to smelling of odorless air. The study also included online measurements of respiratory frequency and amplitude and heart rate variations by recording of R wave intervals (RR) on the surface electrocardiogram. The MCS subjects activated odor-processing brain regions less than controls, despite the reported, and physiologically indicated (decreased RR interval) distress. In parallel, they showed an odorant-related increase in activation of the anterior cingulate cortex and cuneus-precuneus. Notably, the baseline rCBF was normal. Thus, the abnormal patterns were observed only in response to odor signals. Subjects with MCS process odors differently from controls, however, without signs of neuronal sensitization. One possible explanation for the observed pattern of activation in MCS is a top-down regulation of odor-response via cingulate cortex.

Cognitive decline in temporal lobe epilepsy due to unilateral hippocampal sclerosis

OBJECTIVE

We assessed the cognitive performance of patients with temporal lobe epilepsy (TLE) caused by unilateral hippocampal sclerosis (HS), in comparison with that of matched, healthy controls. We report the relationship between cognitive measures and duration of epilepsy, correlating with hippocampal volumes, and the impact of educational level on cognitive decline.

METHODS

This study involved 61 outpatients (40 with < or = 8 years and 21 with >8 years of formal education) with unilateral HS and 61 controls. Volumetric MRI was performed on all patients and 10 controls. The results (mean, SD) of the neuropsychological tests of healthy subjects and patients were compared using the Student t and Mann-Whitney tests.

RESULTS

Patients performed worse than controls in the neuropsychological evaluation. When adjusted z scores were used to calculate the impairment index, patients had a greater percentage of abnormal tests compared with controls. The cognitive decline, assessed through the impairment index, correlated with duration of epilepsy. Higher level of education did not protect against this decline, thus not supporting the hypothesis of cerebral reserve in this population. A significant correlation between hippocampal volumetric measures and duration of epilepsy was observed only in patients with left HS.

CONCLUSION

Patients with TLE caused by HS present with cognitive morbidity that extends beyond memory deficits. Cognitive decline is associated with duration of epilepsy, and in patients with left-sided HS, duration may correlate with volumetric hippocampal loss.

An unspecified clinical syndrome in mentally retarded patients with bilateral mesial temporal sclerosis

PURPOSE

The association of febrile convulsions and mesial temporal sclerosis (MTS) is a well-known phenomenon. However, the effects of mental retardation on febrile convulsions and MTS have not been investigated previously. The aim of this study is to investigate the relation of mental retardation to febrile convulsions especially as febrile status epilepticus and MTS.

METHODS

We describe three patients who have bilateral mesial temporal sclerosis with mental retardation and a history of febrile status epilepticus (FSE), and have clinically typical mesial temporal lobe epilepsy (MTLE).

RESULTS

The FRSB and neuropsychology test revealed executive dysfunction in patients whose bilateral MTS had a benign course, which was unexpected.

CONCLUSIONS

Febrile status epilepticus might have a role in the development of their mental retardation. This study also pointed out that MTS might have subtypes as a result of our attempts at distinguishing patients with MTS.

Facial paresis in patients with mesial temporal sclerosis: clinical and quantitative MRI-based evidence of widespread disease

PURPOSE

To assess the frequency and significance of facial paresis (FP) in a well-defined cohort of mesial temporal lobe epilepsy (MTLE) patients.

METHODS

One hundred consecutive patients with MRI findings consistent with mesial temporal sclerosis (MTS) and concordant electroclinical data underwent facial motor examination at rest, with voluntary expression, and with spontaneous smiling. Hippocampal, amygdaloid, and temporopolar (TP) volumetric measures were acquired. Thirty healthy subjects, matched according to age and sex, were taken as controls.

RESULTS

Central-type FP was found in 46 patients. In 41 (89%) of 46, it was visualized at rest, with voluntary and emotional expression characterizing true facial motor paresis. In 33 (72%) of 46 patients, FP was contralateral to the side of MTS. By using a 2-SD cutoff from the mean of normal controls, we found reduction in TP volume ipsilateral to MTS in 61% of patients with FP and in 33% of those without (p = 0.01). Febrile seizures as initial precipitating injury (IPI) were observed in 34% of the patients and were classified as complex in 12 (26%) of 46 of those with FP and in five (9%) of 54 of those without (p = 0.02). The presence of FP was significantly associated with a shorter latent period and younger age at onset of habitual seizures, in particular, with secondarily generalized tonic-clonic seizures.

CONCLUSIONS

Facial paresis is a reliable lateralizing sign in MTLE and was associated with history of complex febrile seizures as IPI, younger age at onset of disease, and atrophy of temporal pole ipsilateral to MTS, indicating more widespread disease.

Hippocampal volumes and diffusion-weighted image findings in children with prolonged febrile seizures

OBJECTIVES

To assess hippocampal volumes (HV) and signal changes on diffusion-weighted imaging (DWI) within 5 days of prolonged febrile seizures (PFS) and compare them with the PFS duration and EEG.

METHODS

We studied 12 children (mean age: 32 +/- 21 months, range 10 months-5 years) within 5 days of a first episode of PFS (a seizure or series of seizures lasting for 30 min or longer, without return of consciousness between the seizures). The HV measurements were carried out using high-resolution magnetic resonance imaging and signal intensity abnormalities were evaluated visually on DWI. HV in patients were compared with those of 13 neurologically normal controls (mean age 31 +/- 16 months, range 15 months-5 years). HV abnormalities correlated with PFS duration. HV and DWI abnormalities were compared with EEG abnormalities.

RESULTS

Seizure duration ranged from 40 to 95 min. In seven out of twelve patients, seizures were refractory and lasted for 60 min or longer despite intravenous infusion of diazepam. In the patients with PFS for 60 min or longer, HV were significantly larger than that of controls. In all patients, there was a positive correlation between HV and seizure duration. DWI showed hyperintensity in unilateral hippocampus in three patients with intractable seizures, ipsilateral thalamus in two, and cingulate in one. EEG showed abnormalities in temporal areas ipsilateral to the DWI abnormalities in these patients.

CONCLUSIONS

Large HV and hippocampal hyperintensity on DWI were seen in patients with refractory PFS. Our results suggest that medically refractory PFS lasting for 60 min or longer may cause structural changes in limbic structures that could promote later epileptogenesis.

Increased hippocampal atrophy rates in AD over 6 months using serial MR imaging

We measured hippocampi on baseline-, 6- and 12-month scans in a group of AD (n=36) and control subjects (n=20). We found that mean annualised atrophy rates using 6-month intervals were comparable at a group level to those generated from a 12-month interval. Higher variance was seen using shorter intervals, although this was only significant in the control group. This has implications where shorter inter-scan intervals may be advantageous, such as rapid diagnosis, and tracking of disease progression including in a clinical trial.

Knowledge-based localization of hippocampus in human brain MRI

We present a novel and efficient method for localization of human brain structures such as hippocampus. Landmark localization is important for segmentation and registration. This method follows a statistical roadmap, consisting of anatomical landmarks, to reach the desired structures. Using a set of desired and undesired landmarks, identified on a training set, we estimate Gaussian models and determine optimal search areas for desired landmarks. The statistical models form a set of rules to evaluate the extracted landmarks during the search procedure. When applied on 900 MR images of 10 epileptic patients, this method demonstrated an overall success rate of 83%.

Evidence of disturbed amygdalar energy metabolism in patients with borderline personality disorder

In order to detect possible links between structural and neurochemical brain abnormalities we applied high resolution morphometric imaging and short-echo time absolute-quantification magnetic resonance spectroscopy (MRS) at the left hand side to the amygdala in 12 patients with borderline personality disorder (BPD) and 10 group-matched healthy controls. Confirming earlier reports we found a significant 11-17% reduction of amygdalar volumes in patients with BPD. In addition there was a significant 17% increase of left amygdalar creatine concentrations in BPD patients. Left amygdalar creatine concentration correlated positively with measures of anxiety and negatively with amygdalar volume. This pilot study of simultaneous amygdalar morphometry and spectroscopy in BPD reveals a possible link between amygdalar volume loss, psychopathology and neurochemical abnormalities in terms of creatine signals.

High-field magnetic resonance imaging of brain iron in Alzheimer disease

OBJECTIVES

Increased iron deposition in the brain may occur in several neurodegenerative diseases, including Alzheimer disease (AD). Iron deposits shorten T2 relaxation times on T2-weighted magnetic resonance (MR) images. Iron-dependent contrast increases with magnetic field strength. We hypothesized that T2 mapping using 3 T MR imaging (MRI) can disclose differences between normal controls and AD subjects.

METHODS

High-resolution brain imaging protocols were developed and applied to 24 AD patients and 20 age-matched controls using 3 T MRI. Eight anatomical regions of interest were manually segmented, and T2 histograms were computed. A visual analysis technique, the heat map, was modified and applied to the large image data sets generated by these protocols.

RESULTS

A large number (163) of features from these histograms were examined, and 38 of these were significantly different (P < 0.05) between the groups. In the hippocampus, evidence was found for AD-related increases in iron deposition (shortened T2) and in the concentration of free tissue water (lengthened T2). Imaging of a section of postmortem brain before and after chemically extracting the iron established the presence of MRI-detectable iron in the hippocampus, cortex, and white matter in addition to brain regions traditionally viewed as containing high iron concentrations.