Brainstem glucose metabolism predicts reward dependence scores in treatment-resistant major depression

BACKGROUND

It has been suggested that individual differences in temperament could be involved in the (non-)response to antidepressant (AD) treatment. However, how neurobiological processes such as brain glucose metabolism may relate to personality features in the treatment-resistant depressed (TRD) state remains largely unclear.

METHODS

To examine how brainstem metabolism in the TRD state may predict Cloninger's temperament dimensions Harm Avoidance (HA), Novelty Seeking (NS), and Reward Dependence (RD), we collected ¹⁸fluorodeoxyglucose positron emission tomography (¹⁸FDG PET) scans in 40 AD-free TRD patients. All participants were assessed with the Temperament and Character Inventory (TCI). We applied a multiple kernel learning (MKL) regression to predict the HA, NS, and RD from brainstem metabolic activity, the origin of respectively serotonergic, dopaminergic, and noradrenergic neurotransmitter (NT) systems.

RESULTS

The MKL model was able to significantly predict RD but not HA and NS from the brainstem metabolic activity. The MKL pattern regression model identified increased metabolic activity in the pontine nuclei and locus coeruleus, the medial reticular formation, the dorsal/median raphe, and the ventral tegmental area that contributed to the predictions of RD.

CONCLUSIONS

The MKL algorithm identified a likely metabolic marker in the brainstem for RD in major depression. Although ¹⁸FDG PET does not investigate specific NT systems, the predictive value of brainstem glucose metabolism on RD scores however indicates that this temperament dimension in the TRD state could be mediated by different monoaminergic systems, all involved in higher order reward-related behavior.

Lateralized subgenual ACC metabolic connectivity patterns in refractory melancholic depression: does it matter?

Although treatment resistance to antidepressant pharmacotherapy is quite common, the phenomenon of refractory major depressive disorder (rMDD) is not well understood. Nevertheless, the metabolic activity of the subgenual anterior cingulate cortex (sgACC) has been put forward as a possible metabolic biomarker of clinical prediction and response, albeit sgACC lateralization differences in functional connectivity have not yet been extensively examined. Also not in the refractory depressed state. To examine sgACC lateralization differences in metabolic connectivity, we recruited 43 right-handed antidepressant-free unipolar melancholic rMDD patients and 32 right-handed healthy controls to participate in this 18FDG PET study and developed a searchlight-based interregional covariance connectivity approach. Compared to non-depressed individuals, sgACC covariance analysis showed stronger metabolic connections with frontolimbic brain regions known to be affected in the depressed state. Furthermore, whereas the left sgACC showed stronger metabolic connections with ventromedial prefrontal cortical regions, implicated in anhedonia, suicidal ideation, and self-referential processes, the right sgACC showed significantly stronger metabolic connections with posterior hippocampal and cerebellar regions, respectively specialized in memory and social processing. Overall, our results substantiate earlier research that the sgACC is a metabolic key player when clinically depressed and that distinct lateralized sgACC metabolic connectivity patterns are present.

Prosthetic vascular graft infection: A systematic review and meta-analysis on diagnostic accuracy of 18FDG PET/CT

INTRODUCTION

There is a high risk of mortality and morbidity associated with Vascular Graft Infections (VGI) which requires early diagnosis. The aim of the present systematic review and meta-analysis was to evaluate the diagnostic accuracy, sensitivity and specificity of 18FDG PET/CT in diagnosing VGI.

METHODS

A systematic review was conducted according to the PRISMA guidelines through a search in Embase, PubMed, and Cochrane databases. We evaluated five parameters including specificity, sensitivity, negative and positive predictive values (NPV and PPV), and accuracy. We used STATA/MP 15.0 (StataCorp, College Station, TX) for all of our analyses.

RESULTS

Overall 10 studies including 320 patients undergone 18FDG PET/CT were included. The sensitivity, specificity, positive and negative likelihood ratios along with their 95% CI were 0.92 (95% CI 0.88-0.95), 0.76 (95% CI 0.76-0.70), 3.49 (95% CI 3.49-2.32) and 0.14 (95% CI 0.09-0.23), respectively. The diagnostic odds ratio (DOR) for diagnosis of VGI was 37.12 (95% CI 14.84-92.82). The mean cut-off value of the maximum standardized uptake value (SUVmax) for diagnosis of VGI was 5.39 while the overall mean SUVmax among patients with VGI was 8.47.

CONCLUSION

According to our results, 18FDG PET/CT is a useful diagnostic method in detecting active VGI with high diagnostic accuracy. Because of its ability to evaluate morphology and main texture using SUVmax, the 18FDG PET/CT provides an objective assessment of aspects and extent of disease activity, which results in preventing unnecessary surgery, proper treatment planning, and evaluating the effectiveness of treatment.

Cognitive impairment and altered cerebral glucose metabolism in the subacute stage of COVID-19

During the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic, neurological symptoms increasingly moved into the focus of interest. In this prospective cohort study, we assessed neurological and cognitive symptoms in hospitalized coronavirus disease-19 (COVID-19) patients and aimed to determine their neuronal correlates. Patients with reverse transcription-PCR-confirmed COVID-19 infection who required inpatient treatment primarily because of non-neurological complications were screened between 20 April 2020 and 12 May 2020. Patients (age > 18 years) were included in our cohort when presenting with at least one new neurological symptom (defined as impaired gustation and/or olfaction, performance < 26 points on a Montreal Cognitive Assessment and/or pathological findings on clinical neurological examination). Patients with ≥2 new symptoms were eligible for further diagnostics using comprehensive neuropsychological tests, cerebral MRI and ¹⁸fluorodeoxyglucose (FDG) PET as soon as infectivity was no longer present. Exclusion criteria were: premorbid diagnosis of cognitive impairment, neurodegenerative diseases or intensive care unit treatment. Of 41 COVID-19 inpatients screened, 29 patients (65.2 ± 14.4 years; 38% female) in the subacute stage of disease were included in the register. Most frequently, gustation and olfaction were disturbed in 29/29 and 25/29 patients, respectively. Montreal Cognitive Assessment performance was impaired in 18/26 patients (mean score 21.8/30) with emphasis on frontoparietal cognitive functions. This was confirmed by detailed neuropsychological testing in 15 patients. ¹⁸FDG PET revealed pathological results in 10/15 patients with predominant frontoparietal hypometabolism. This pattern was confirmed by comparison with a control sample using voxel-wise principal components analysis, which showed a high correlation (R² = 0.62) with the Montreal Cognitive Assessment performance. Post-mortem examination of one patient revealed white matter microglia activation but no signs of neuroinflammation. Neocortical dysfunction accompanied by cognitive decline was detected in a relevant fraction of patients with subacute COVID-19 initially requiring inpatient treatment. This is of major rehabilitative and socioeconomic relevance.

The pons as reference region for intensity normalization in semi-quantitative analysis of brain 18FDG PET: application to metabolic changes related to ageing in conventional and digital control databases

Background

The objective of the study is to define the most appropriate region for intensity normalization in brain ¹⁸FDG PET semi-quantitative analysis. The best option could be based on previous absolute quantification studies, which showed that the metabolic changes related to ageing affect the quasi-totality of brain regions in healthy subjects. Consequently, brain metabolic changes related to ageing were evaluated in two populations of healthy controls who underwent conventional (n = 56) or digital (n = 78) ¹⁸FDG PET/CT. The median correlation coefficients between age and the metabolism of each 120 atlas brain region were reported for 120 distinct intensity normalizations (according to the 120 regions). SPM linear regression analyses with age were performed on most significant normalizations (FWE, p < 0.05).

Results

The cerebellum and pons were the two sole regions showing median coefficients of correlation with age less than − 0.5. With SPM, the intensity normalization by the pons provided at least 1.7- and 2.5-fold more significant cluster volumes than other normalizations for conventional and digital PET, respectively.

Conclusions

The pons is the most appropriate area for brain ¹⁸FDG PET intensity normalization for examining the metabolic changes through ageing.

The effect of systemic inflammation indexes and 18FDG PET metabolic parameters on survival in advanced lung adenocarcinoma

OBJECTIVE

To determine the effect of systemic inflammation indexes and fluorine-18 fluorodeoxyglucose (¹⁸FDG) positron emission tomography (PET) metabolic parameters on survival in advanced lung adenocarcinoma.

METHODS

A total of 133 patients who underwent ¹⁸FDG PET for initial staging were investigated retrospectively. Baseline patient characteristics, routine blood test results, ¹⁸FDG PET metabolic parameters, and treatment history were examined. Overall survival (OS) was demonstrated by Kaplan-Meier analysis, and the curves were compared by the log-rank test. Systemic inflammation response index (SIRI) was defined as neutrophil x monocyte/lymphocyte count.

RESULTS

Lymphocyte/monocyte ratio (LMR) and SIRI were found to be significant for OS. The cutoff point was 2.25 for LMR. Median OS was 8 months for ⩽2.25 and 14 months for >2.25 (p = 0.005). For SIRI, the cutoff point was 2. SIRI ⩽2 was associated with a median OS of 16 months compared to 10 months for patients with SIRI >2 (p = 0.043). Maximum of standardized uptake value, total lesion glycolysis, and metabolic tumor volume were not found to be significant for OS (p = 0.225, p = 0.061, p = 0.355, respectively). No correlation was found between inflammatory indexes and PET metabolic parameters.

CONCLUSION

Age and LMR parameters were prognostic for survival in Cox regression analysis. There was no correlation between ¹⁸FDG PET parameters and inflammatory indexes.

Therapeutic use of carbohydrate-restricted diets in an autistic child; a case report of clinical and 18FDG PET findings

The ketogenic diet (KD) is a high-fat, adequate-protein, and low-carbohydrate diet that has been used successfully in the treatment of refractory epilepsies for almost 100 years. There has been accumulating evidence to show that the KD may provide a therapeutic benefit in autism spectrum disorders, albeit by a yet-unknown mechanism. We report a case of a 6-year-old patient with high-functioning autism and subclinical epileptic discharges who responded poorly to several behavioural and psychopharmacological treatments. The patient was subsequently placed on the KD due to significant glucose hypometabolism in the brain as revealed by an 18FDG PET. As soon as one month after starting the KD, the patient's behavior and intellect improved (in regard to hyperactivity, attention span, abnormal reactions to visual and auditory stimuli, usage of objects, adaptability to changes, communication skills, fear, anxiety, and emotional reactions); these improvements continued until the end of the observation period at 16 months on the KD. The 18FDG PET, measured at 12 months on the KD, revealed that 18F-FDG uptake decreased markedly and diffusely in the whole cerebral cortex with a relatively low reduction in basal ganglia in comparison to the pre-KD assessment. It warrants further investigation if the 18FDG PET imaging could serve as a biomarker in identifying individuals with autism who might benefit from the KD due to underlying abnormalities related to glucose hypometabolism.

Longer depressive episode duration negatively influences HF-rTMS treatment response: a cerebellar metabolic deficiency?

Repetitive transcranial magnetic stimulation (rTMS) is an evidence based neurostimulation modality used to treat patients with Major Depressive Disorder (MDD). In spite that the duration of current a depressive episode has been put forward as a negative predictor for clinical outcome, little is known about the underlying neurobiological mechanisms of this phenomenon. To address this important issue, in a sample of 43 melancholic stage III treatment resistant antidepressant-free refractory MDD patients, we reanalysed regional cerebral glucose metabolism (CMRglc) before high frequency (HF)-rTMS treatment, applied to the left dorsolateral prefrontal cortex (DLPFC). Besides that a lower baseline cerebellar metabolic activity indicated negative clinical response, a longer duration of the depressive episode was a negative indicator for recovery and negatively influenced cerebellar CMRglc. This exploratory ¹⁸FDG PET study is the first to demonstrate that the clinical response of HF-rTMS treatment in TRD patients may depend on the metabolic state of the cerebellum. Our observations could imply that for left DLPFC HF-rTMS non-responders other brain localisations for stimulation, more specifically the cerebellum, may be warranted.

Estimating the amount of FDG uptake in physiological tissues

INTRODUCTION

It is known that for a fixed amount of injected tracer, the amount available for a tissue of interest will be less if other tissues show intense uptake. The aim of this study was to estimate the magnitude of 2-deoxy-2-[(18)F]fluoro-D-glucose (18FDG) uptake amount in physiological tissues that may show an intense uptake in current clinical practice.

METHODS

A formula was established providing an estimate of the percentage of injected 18FDG molecules (P; in %) that are irreversibly trapped in an 18FDG-positive tissue during a PET examination.

RESULTS

P ≅ 0.17*exp(-λt(acq))*TLG/W, where λ is the (18)F physical decay constant, t(acq) is the injection-acquisition time delay, TLG is total lesion glycolysis (g) and W is the patient weight (kg). The magnitude of P was calculated in two patients showing an intense uptake in brown fat, myocardium and bowels: 0.5, 3.5, and 4.2% respectively.

CONCLUSIONS

A formula is available to quickly estimate the amount of 18FDG uptake in tissues. We suggest that the accumulation of different physiological uptakes may actually affect SUV quantification in a tissue of interest.

Tumor thrombus in the renal vein from an adrenal metastasis of lung cancer: 18FDG PET/CT findings

Tumor thrombus is a rare complication of solid cancer. The authors report a case of a 76-year-old woman presenting a thick walled cystic mass in the lower lobe of the left lung. 18FDG positron emission tomography (PET)/computed tomography (CT) was performed, showing tracer accumulation in the wall of the pulmonary lesion and in the mediastinal and hilar lymph nodes. Moreover, PET/CT depicted a gross mass in the left adrenal gland and a hypermetabolic focus corresponding to the anatomic location of the left renal vein. Contrast-enhanced CT, subsequently performed, confirmed PET findings in the lung, lymph nodes, and adrenal glands, also demonstrating marginal enhancement and intraluminal filling defect in the left renal vein, which was interpreted as tumor thrombus due to the 18FDG uptake at PET scan. CT-guided biopsy of the mass was positive for poorly differentiated carcinoma. 18FDG PET can be useful to diagnose tumor thrombus in oncological patients.