Evidence for Dopamine Abnormalities Following Acute Methamphetamine Exposure Assessed by Neuromelanin-Sensitive Magnetic Resonance Imaging.

Background: Neuromelanin-sensitive magnetic resonance imaging (NM-MRI) is a newly developed MRI technique that provides a non-invasive way to indirectly measure of dopamine (DA) function. This study aimed to determine NM concentrations in brain regions following acute methamphetamine (MA) administration using NM-MRI and to explore whether NM-MRI can be used as a biomarker of DA function in non-neurodegenerative diseases. Methods: Baseline NM-MRI, T1-weighted and T2-weighted images were acquired from 27 rats before drug/placebo injection. The control group (n = 11) received acute placebo (Normal saline), while the experimental group (n = 16) received acute MA. NM-MRI scans were performed 5, 30, 60 and 90 min after injection. Regions of interest (ROIs), including the caudate putamen (CP), nucleus accumbens (NAc), hippocampus (HIP), substantia nigra (SN) and crus cerebri (CC), were manually drawn by an experienced radiologist. NM-MRI signal intensity in five brain regions at different time points (baseline and 5, 30, 60, and 90 min) were analyzed. Results: In both the control and experimental groups, at each time point (baseline and 5, 30, 60, and 90 min), the SN exhibited significantly higher NM-MRI signal intensity than the other brain regions (P < 0.05). In addition, acute MA administration resulted in a continuous upward trend in NM-MRI signal intensity in each brain region over time. However, there was no such trend over time in the control group. The NM-MRI signal intensity of SN in the experimental group was significantly higher at the 60 and 90 min compared with that in the control group (P values were 0.042 and 0.042 respectively). Within experimental group, the NM-MRI signal intensity of SN was significantly higher at the 60 and 90 min compared with that before MA administration (P values were 0.023 and 0.011 respectively). Increased amplitudes and rates of NM-MRI signal intensity were higher in the SN than in other brain regions after MA administration. Conclusion: Our results indicated that NM was mainly deposited in the SN, and the conversion of DA to NM was most significant in the SN after acute MA exposure. Increased DA release induced by acute MA exposure may lead to increased accumulation of NM in multiple brain regions that can be revealed by NM-MRI. NM-MRI may serve as a powerful imaging tool that could have diverse research and clinical applications for detecting pathological changes in drug addiction and related non-neurodegenerative diseases.

Survivors of COVID-19 exhibit altered amplitudes of low frequency fluctuation in the brain: a resting-state functional magnetic resonance imaging study at 1-year follow-up.

Although some short-term follow-up studies have found that individuals recovering from coronavirus disease 2019 (COVID-19) exhibit anxiety, depression, and altered brain microstructure, their long-term physical problems, neuropsychiatric sequelae, and changes in brain function remain unknown. This observational cohort study collected 1-year follow-up data from 22 patients who had been hospitalized with COVID-19 (8 males and 11 females, aged 54.2 ± 8.7 years). Fatigue and myalgia were persistent symptoms at the 1-year follow-up. The resting state functional magnetic resonance imaging revealed that compared with 29 healthy controls (7 males and 18 females, aged 50.5 ± 11.6 years), COVID-19 survivors had greatly increased amplitude of low-frequency fluctuation (ALFF) values in the left precentral gyrus, middle frontal gyrus, inferior frontal gyrus of operculum, inferior frontal gyrus of triangle, insula, hippocampus, parahippocampal gyrus, fusiform gyrus, postcentral gyrus, inferior parietal angular gyrus, supramarginal gyrus, angular gyrus, thalamus, middle temporal gyrus, inferior temporal gyrus, caudate, and putamen. ALFF values in the left caudate of the COVID-19 survivors were positively correlated with their Athens Insomnia Scale scores, and those in the left precentral gyrus were positively correlated with neutrophil count during hospitalization. The long-term follow-up results suggest that the ALFF in brain regions related to mood and sleep regulation were altered in COVID-19 survivors. This can help us understand the neurobiological mechanisms of COVID-19-related neuropsychiatric sequelae. This study was approved by the Ethics Committee of the Second Xiangya Hospital of Central South University (approval No. 2020S004) on March 19, 2020.

Brainstem Congestion Due to Dural Arteriovenous Fistula at the Craniocervical Junction: Case Report and Review of the Literature.

BACKGROUND: Dural arteriovenous fistulas (DAVFs) at the craniocervical junction are rare. Clinical manifestations range from acute or chronic myelopathy to subarachnoid hemorrhage to brainstem dysfunction. We encountered 4 cases of DAVFs at the craniocervical junction with progressive brainstem dysfunction and investigated the typical magnetic resonance imaging (MRI) features using T2-weighting imaging, susceptibility-weighted imaging, diffusion-weighted imaging, and contrast-enhanced imaging. Literature review revealed 10 case reports of DAVFs at the craniocervical junction manifesting with brainstem dysfunction. CASE DESCRIPTION: Four patients presented with DAVFs at the craniocervical junction with progressive brainstem dysfunction. Two patients underwent midline suboccipital craniotomy and C1 laminectomy, and 1 patient underwent transarterial endovascular embolization with Onyx 18 under general anesthesia. All neurologic deficits gradually improved after the operation. In the fourth case, the patient received conservative treatment and did not undergo any surgical procedure. MRI showed high signal intensity on T2-weighted imaging, magnetic resonance angiography, and magnetic resonance venography. Abnormal dilated vessels and flow-void signs around the lesions were detected on susceptibility-weighted imaging and contrast-enhanced images. Two cases revealed no abnormalities and had improved neurological deficits than those showed on diffusion-weighted imaging. CONCLUSIONS: Susceptibility-weighted imaging, diffusion-weighted imaging, or contrast-enhanced scanning should be used during MRI examination of patients with progressive brainstem dysfunction to differentiate DAVFs at the craniocervical junction from other diseases, such as glioma or infection. Prompt diagnosis using MRI is of great significance in producing good functional outcomes of the patients.