Hippocampal Hypermetabolism Research Articles

Subcortical Hypermetabolism Associated With Cortical Hypometabolism Is a Common Metabolic Pattern in Patients With Anti-Leucine-Rich Glioma-Inactivated 1 Antibody Encephalitis.

PurposeBrain 18F-fluorodeoxyglucose positron emission tomography (FDG PET) is a sensitive technique for assisting in the diagnosis of patients with anti-leucine-rich glioma-inactivated 1 (LGI1) antibody encephalitis. However, the common pattern of this disorder assessed by FDG PET remains unknown. The present study aimed to explore the glucose metabolic patterns of this disorder based on PET voxel analysis.MethodsThis retrospective study enrolled 25 patients with anti-LGI1 encephalitis, who were admitted in Beijing Tiantan Hospital between September 2014 and July 2019. The glucose metabolic pattern was compared between the included patients and 44 age- and gender-matched healthy controls using Statistical Parametric Mapping. Then, the correlation between the metabolic pattern and scaled activities of daily living (ADLs) of the patients was assessed.ResultsThe median time from symptom onset to PET scans was 9 w (range:2-53w). The groupwise analysis revealed that patients with anti-LGI1 encephalitis had left hippocampal hypermetabolism and hypometabolism in almost all neocortical regions. The individual-level results showed most patients presented a decreased metabolism in neocortical regions, as well as an increase in metabolism in the hippocampus and basal ganglia. Furthermore, the metabolic gradient between hippocampus and neocortical regions was positively associated with the ADLs (frontal lobe, r=0.529, P=0.008; parietal lobe, r=0.474, P=0.019; occipital lobe, r=0.413, P=0.045; temporal lobe, r=0.490, P=0.015), respectively. In addition, the patients with facio-brachial dystonic seizures (FBDS) presented bilateral putamen hypermetabolism, when compared to patients without FBDS and healthy controls.ConclusionSubcortical hypermetabolism associated with cortical hypometabolism presented with a common metabolic pattern in patients with anti-LGI1 encephalitis in the present study. The resolution of the metabolic gradient of the hippocampal hypermetabolism and neocortical hypometabolism may bring about improved clinical neurologic disability.

Characterization of metabolic activity induced by kainic acid in adult rat whole brain at the early stage: A 18FDG-PET study

ObjectiveBrain metabolic processes are not fully characterized in the kainic acid (KA)-induced Status Epilepticus (KASE). Thus, we evaluated the usefulness of 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) as an experimental strategy to evaluate in vivo, in a non-invasive way, the glucose consumption in several brain regions, in a semi-quantitative study to compare and to correlate with data from electroencephalography and histology studies. Methods.Sixteen male Wistar rats underwent FDG-PET scans at basal state and after KA injection. FDG-PET images were normalized to an MRI-based atlas and segmented to locate regions. Standardized uptake values (SUV) were obtained at several time points. EEGs and cell viability by histological analysis, were also evaluated. ResultsFDG-PET data showed changes in regions such as: amygdala, hippocampus, accumbens, entorhinal cortex, motor cortex and hypothalamus. Remarkably, hippocampal hypermetabolism was found (mean SUV = 2.66 ± 0.057) 2 h after KA administration, while hypometabolism at 24 h (mean SUV = 1.83 ± 0.056) vs basal values (mean SUV = 2.19 ± 0.057). EEG showed increased spectral power values 2 h post-KA administration. Hippocampal viable-cell counting 24 h after KA was decreased, while Fluoro-Jade B-positive cells were increased, as compared to control rats, coinciding with the hypometabolism detected in the same region by semi-quantitative FDG-PET at 24 h after KASE. ConclusionsPET is suitable to measure metabolic brain changes in the rat model of status epilepticus induced by KA (KASE) at the first 24 h, compared to that of EEG; PET data may also be sensitive to cell viability.

ASL MRI and 18F-FDG-PET in autoimmune limbic encephalitis: clues from two paradigmatic cases.

Autoimmune limbic encephalitis (LE) is a neurological condition characterized by seizures and cognitive dysfunction. Fluorine-18 fluorodeoxyglucose (18F-FDG-PET) has recently proved to be an important diagnostic tool in this condition since it may highlight brain metabolism abnormalities in a very early stage of the disease. Two main 18F-FDG-PET patterns have been described: the mixed hypermetabolic/hypometabolic and the neurodegenerative one. Arterial spin labeling (ASL) is an MRI technique showing brain perfusion, rarely used in autoimmune neurological conditions. The aim of the present study was to study patients with LE with both techniques, in order to compare their results. Two patients with LE underwent to 18F-FDG-PET and ASL MRI scans using the pseudo-continuous arterial spin labeling (PCASL) technique. Areas of altered perfusion and metabolism were analyzed by visual inspection, and findings were compared between the two techniques. In the first patient, a relapsing LGI-1 LE, right hippocampal hypermetabolism was detected by 18F-FDG-PET (mixed hypermetabolic/hypometabolic pattern), while ASL MRI showed right hippocampal increased perfusion. In the second patient, a seronegative LE, 18F-FDG-PET scan detected a left hemispheric hypoperfusion (neurodegenerative pattern) and ASL MRI yielded similar results. The two 18F-FDG-PET patterns of altered metabolism were similarly detected by ASL imaging. ASL and 18F-FDG-PET findings are strongly concordant in LE. ASL imaging was able to detect the two main 18F-FDG-PET patterns previously described in patients with LE.

Metabolic Abnormalities in the Hippocampus of Patients with Schizophrenia: A 3D Multivoxel MR Spectroscopic Imaging Study at 3T.

Schizophrenia is well-known to be associated with hippocampal structural abnormalities. We used 1H-MR spectroscopy to test the hypothesis that these abnormalities are accompanied by NAA deficits, reflecting neuronal dysfunction, in patients compared with healthy controls. Nineteen patients with schizophrenia (11 men; mean age, 40.6 ± 10.1 years; mean disease duration, 19.5 ± 10.5 years) and 11 matched healthy controls (5 men; mean age, 33.7 ± 10.1 years) underwent MR imaging and multivoxel point-resolved spectroscopy (TE/TR, 35/1400 ms) 1H-MRS at 3T to obtain their hippocampal GM absolute NAA, Cr, Cho, and mIns concentrations. Unequal variance t tests and ANCOVA were used to compare patients with controls. Bilateral volumes from manually outlined hippocampal masks were compared by using unequal variance t tests. Patients' average hippocampal GM Cr concentrations were 19% higher than that of controls, 8.7 ± 2.2 versus 7.4 ± 1.2 mmol/L (P < .05); showing no differences, concentrations in NAA were 8.8 ± 1.6 versus 8.7 ± 1.2 mmol/L; in Cho, 2.3 ± 0.7 versus 2.1 ± 0.3 mmol/L; and in mIns, 6.1 ± 1.5 versus 5.2 ± 0.9 (all P > .1). There was a positive correlation between mIns and Cr in patients (r = 0.57, P = .05) but not in controls. The mean bilateral hippocampal volume was ∼10% lower in patients: 7.5 ± 0.9 versus 8.4 ± 0.7 cm3 (P < .05). These findings suggest that the hippocampal volume deficit in schizophrenia is not due to net loss of neurons, in agreement with histopathology studies but not with prior 1H-MR spectroscopy reports. Elevated Cr is consistent with hippocampal hypermetabolism, and its correlation with mIns may also suggest an inflammatory process affecting some cases; these findings may suggest treatment targets and markers to monitor them.

Imaging Patients with Psychosis and a Mouse Model Establishes a Spreading Pattern of Hippocampal Dysfunction and Implicates Glutamate as a Driver

The hippocampus in schizophrenia is characterized by both hypermetabolism and reduced size. It remains unknown whether these abnormalities are mechanistically linked. Here we addressed this question by using MRI tools that can map hippocampal metabolism and structure in patients and mouse models. In at-risk patients, hypermetabolism was found to begin in CA1 and spread to the subiculum after psychosis onset. CA1 hypermetabolism at baseline predicted hippocampal atrophy, which occurred during progression to psychosis, most prominently in similar regions. Next, we used ketamine to model conditions of acute psychosis in mice. Acute ketamine reproduced a similar regional pattern of hypermetabolism, while repeated exposure shifted the hippocampus to a hypermetabolic basal state with concurrent atrophy and pathology in parvalbumin-expressing interneurons. Parallel invivo experiments using the glutamate-reducing drug LY379268 and direct measurements of extracellular glutamate showed that glutamate drives both neuroimaging abnormalities. These findings show that hippocampal hypermetabolism leads to atrophy in psychotic disorder and suggest glutamate as a pathogenic driver.

Chronic Sequelae of Herpes Simplex Encephalitis Demonstrated on Interictal F-18 FDG PET/CT

We report a case of severe unilateral temporal lobe hypometabolism depicted on interictal FDG-PET/CT in a 56-year-old man presenting with cognitive-behavioral problems, affective disorder, receptive aphasia, and complex partial seizures. The seizures had been treated with gabapentin and phenytoin for 18 years. The extent and severity of hypometabolism were significantly greater than typically seen in patients with idiopathic temporal lobe epilepsy. The combination of electroencephalography, left temporal lobe encephalomalacia depicted on serial MRI, and the interictal FDG-PET findings implicated the temporal lobe as the site of seizure origin. Further clinical history disclosed a diagnosis of remote herpes simplex encephalitis (HSE) infection more than 24 years earlier confirmed by laboratory testing. The patient had been treated with antiviral therapy with full immediate neurologic recovery. Brain SPECT imaging has been previously reported in the literature to demonstrate focally increased cortical perfusion in acute HSE, followed by hypoperfusion of the affected region, in the recovery phase (between 3 and 6 months). A previous report of the FDG-PET findings in HSE showed hippocampal hypermetabolism acutely, then hypometabolism at 3 and 9 months. Our case provides evidence that the metabolic sequelae of HSE can become persistent, despite antiviral treatment, likely the result of gliosis and atrophy.

Prefrontal atrophy in first episodes of schizophrenia associated with limbic metabolic hyperactivity

Reduced volume and activity of the prefrontal (PF) cortical gray matter (GM) and hippocampal hypermetabolism are repeated findings in schizophrenia. There is still an information deficit about the significance of reduction of PF GM in schizophrenia, and a simultaneous study of PF anatomy and activity and limbic metabolism can contribute to fill that deficit. In order to do so, we used positron emission tomography (PET) with 18-fluoro-deoxyy-glucose (FDG) during an attention task and magnetic resonance imaging (MRI) to study a sample of first episodes of pscyhosis. We included 21 first episodes (FE) of psychosis and 16 healthy controls. A diagnosis of schizophrenia was confirmed in the follow-up in eleven of these patients and ruled out in the remaining 10 cases. Volumes of PF GM were determined and also activity in the same region and in the hippocampus. Residual GM was estimated in the PF region as a quantitative measurement of the degree of atrophy in each individual, using age and intracranial volume data from a set of 45 healthy controls and linear regression.Patients with schizophrenia had lower PF metabolic activation and greater hippocampal activity than controls. FE patients without schizophrenia were no different in any parameter as compared to controls. Patients with schizophrenia presented an inverse and significant association between GM deficit and hippocampal activity that was not observed in controls or in patients without schizophrenia. The same association was previously described by our group using PET in the resting state in recent-onset and chronic patients with schizophrenia. These findings support a loss in PF inhibitory capacity as a possible link between anatomical and functional alterations in schizophrenia.

Limbic encephalitis and hyperactive foci on PET scan

Two cases of patients with paraneoplastic limbic encephalitis, difficult to control seizures, and unilateral hippocampal hypermetabolism on positron emission tomography (PET) are described. Two women aged 33 and 61 presented with uncontrolled complex partial seizures, profound memory loss and cognitive decline. One was later diagnosed with breast cancer and the other with lung cancer. Video-EEG on the first patient recorded multifocal sharp waves and bilateral independent seizure onsets. The second patient had no epileptiform discharges and bitemporal ictal onset, even though the clinical seizures suggested a right temporal onset. Magnetic resonance imaging (MRI) was normal in both patients. PET scans obtained in the interictal state showed right hippocampal hypermetabolism in both patients. In the second patient, the lung cancer was irradiated with resolution of seizures and improvement of memory function. A PET scan six months later was normal. Subsequent seizure recurrence and worsening of memory led to the discovery of widespread metastases. Limbic encephalitis should be considered in the differential diagnosis of intractable partial epilepsy, particularly if accompanied by severe memory loss and cognitive decline. Treatment of the underlying cancer may be lead to improved seizure control. Hippocampal hypermetabolism may be a common feature on PET, and may indicate subclinical seizure activity.

Transient glucose hypermetabolism after acute subdural hematoma in the rat

Ischemic brain damage occurs in most patients with acute subdural hematoma, yet many aspects of the distribution and extent of this damage remain unexplained. Previous studies in rat model, which produces a region of infarction under the hematoma, have implicated an "excitotoxic" mechanism, suggesting that high concentrations of excitatory amino acids may exacerbate ischemic damage. A study is described in which local glucose utilization is measured 2 or 4 hours after induction of acute subdural hematoma in the rat. These changes are compared to those produced by introducing the same volume of inert silicone gel into the subdural space. Massive increases (up to 142%) in glucose utilization occurred throughout both hippocampi and in a variable zone around the ischemic core, but these had normalized by 4 hours after blood injection. Hippocampal hypermetabolism was not seen after introduction of the silicone mass, suggesting that diffusible substances from the clotted blood may be responsible for these changes. This transient hypermetabolism accords with an excitotoxic process, which may amplify brain damage after acute subdural hematoma.

Endoscopic retrograde choledochopancreatography in the diagnosis of pancreatic disease.

<h3>BACKGROUND AND PURPOSE:</h3> Schizophrenia is well-known to be associated with hippocampal structural abnormalities. We used ¹H-MR spectroscopy to test the hypothesis that these abnormalities are accompanied by NAA deficits, reflecting neuronal dysfunction, in patients compared with healthy controls. <h3>MATERIALS AND METHODS:</h3> Nineteen patients with schizophrenia (11 men; mean age, 40.6 ± 10.1 years; mean disease duration, 19.5 ± 10.5 years) and 11 matched healthy controls (5 men; mean age, 33.7 ± 10.1 years) underwent MR imaging and multivoxel point-resolved spectroscopy (TE/TR, 35/1400 ms) ¹H-MRS at 3T to obtain their hippocampal GM absolute NAA, Cr, Cho, and mIns concentrations. Unequal variance <i>t</i> tests and ANCOVA were used to compare patients with controls. Bilateral volumes from manually outlined hippocampal masks were compared by using unequal variance <i>t</i> tests. <h3>RESULTS:</h3> Patients9 average hippocampal GM Cr concentrations were 19% higher than that of controls, 8.7 ± 2.2 versus 7.4 ± 1.2 mmol/L (<i>P</i> &lt; .05); showing no differences, concentrations in NAA were 8.8 ± 1.6 versus 8.7 ± 1.2 mmol/L; in Cho, 2.3 ± 0.7 versus 2.1 ± 0.3 mmol/L; and in mIns, 6.1 ± 1.5 versus 5.2 ± 0.9 (all <i>P</i> &gt; .1). There was a positive correlation between mIns and Cr in patients (<i>r</i> = 0.57, <i>P</i> = .05) but not in controls. The mean bilateral hippocampal volume was ∼10% lower in patients: 7.5 ± 0.9 versus 8.4 ± 0.7 cm³ (<i>P</i> &lt; .05). <h3>CONCLUSIONS:</h3> These findings suggest that the hippocampal volume deficit in schizophrenia is not due to net loss of neurons, in agreement with histopathology studies but not with prior ¹H-MR spectroscopy reports. Elevated Cr is consistent with hippocampal hypermetabolism, and its correlation with mIns may also suggest an inflammatory process affecting some cases; these findings may suggest treatment targets and markers to monitor them.