Metabolic changes in the ischemic penumbra after carotid endarterectomy in stroke patients by localized in vivo proton magnetic resonance spectroscopy (1H-MRS)

Hippocampal neurometabolic and structural changes from pre-to post-COVID-19: A case-series study

BACKGROUND

Neurological complications of the COVID-19 infection may be caused in part by local neurochemical and structural abnormalities that could not be detected during routine medical examinations. We examined within subject neurometabolic and structural brain alterations from pre-to post-COVID-19 in the hippocampal region of three elderly individuals (aged 63-68 years) who had a COVID-19 infection with mild symptoms. Patients were participating in an interventional study in which they were closely monitored at the time they were diagnosed with COVID-19. Patients 1 and 2 just completed 18-20 resistance training sessions prior to their diagnosis. Patient 3 was assigned to a non-training condition in the same study.

METHODS

Whole brain magnetic resonance imaging (MRI) images and proton magnetic resonance spectroscopy (1H-MRS) of the left hippocampus were collected before and after infection. Structural and spectroscopic imaging measures post-COVID-19 were contrasted to the pre-COVID-19 measures and were compared with values for Minimal Detectable Change at 95% (MDC95) and 90% (MDC90) confidence from a group of six elderly (aged 60-79 years) without COVID-19 that participated in the same study.

RESULTS

After SARS-COV-2 infection, we observed a reduction of glutamate-glutamine (Glx) in Patients 1 and 2 (≥ 42.0%) and elevation of myo-inositol (mIns) and N-acetyl-aspartate (NAA) in Patient 3 (≥ 36.4%); all > MDC90. MRI findings showed increased (Patients 1 and 2) or unchanged (Patient 3) hippocampal volume.

CONCLUSIONS

Overall, findings from this exploratory study suggest that mild COVID-19 infection could be associated with development of local neuroinflammation and reduced glutamate levels in the hippocampus. Our 1H-MRS findings may have clinical value for explaining chronic neurological and psychological complaints in COVID-19 long-haulers.

Secondary injury to distal regions after intracerebral hemorrhage influence neurological functional outcome

Although many studies have focused on functional impairment after intracerebral hemorrhage, little is known about the relationship between secondary injuries to distal regions and neurological function. Our study aimed to evaluate the secondary injuries after intracerebral hemorrhage and explore their relationship to neurological functional outcome. Twenty-one patients with hemorrhages in supratentorial, deep locations and 10 healthy subjects were recruited. Longitudinal examinations of diffusion tensor imaging, hydrogen proton magnetic resonance spectroscopy imaging and neuropsychological assessment were performed after weeks 1 and 12 to elucidate the relationship between magnetic resonance imaging parameters and neurologic outcomes. By week 12, motor function had significantly improved, but cognitive function had deteriorated compared to week 1. Fractional anisotropy values for the ipsilateral cerebral peduncle correlated with motor function at week 1. No significant correlation between fractional anisotropy for the ipsilateral cerebral peduncle and the Fugl-Meyer Motor Scale was found at week 12. Fractional anisotropy values for the ipsilateral hippocampus were related to the Montreal Cognitive Assessment and Mini-Mental State Examination at weeks 1 and 12. Deep supratentorial hemorrhage may result in injury to distal regions, which correlate with impaired motor and cognitive function.

Metabolic changes in acute cerebral infarction: Findings from proton magnetic resonance spectroscopic imaging

The purpose of this study was to investigate the clinical role of proton magnetic resonance spectroscopy (¹H-MRS) in the diagnosis of acute cerebral infarction. Using databases available at the Fifth Affiliated Hospital of Zhengzhou University (Zhengzhou, China), the medical records of 47 patients with acute cerebral infarction treated between April 2010 and March 2012 were retrospectively reviewed. The patients underwent routine magnetic resonance imaging (MRI), diffusion-weighted imaging (DWI) and multiple-voxel ¹H-MRS examination within 12 h after the onset of stroke. The patients then received normal medical treatment for 2 weeks and underwent follow-up ¹H-MRS examination at 1–2 months after stroke. The concentrations of the main metabolites [N-acetylaspartic acid (NAA), creatine (Cr), choline (Cho) and lactate (Lac)] in the infarct center, the infarction border region and the contralateral brain areas (control) were analyzed. The 47 patients experienced changes in NAA, Cho and Lac levels at different stages after stroke. In the infarction center, the NAA/Cr and NAA/Cho ratios decreased, while the Lac/Cr ratio increased within 12 h compared with those in the contralateral side. Within 6–12 h after stroke, the Lac/Cr ratio increased and the NAA/Cho ratio decreased compared with those <6 h after stroke. During the 1–2 months post-stroke, significant reductions in the NAA/Cr, NAA/Cho, Cho/Cr and Lac/Cr ratios were observed in the infarction center. In the infarction border region, the Lac/Cr ratio increased significantly at 12 h and decreased during the 1–2 months after stroke. The NAA/Cr, NAA/Cho and Cho/Cr ratios were significantly increased in the infarction border regions of patients who received thrombolytic therapy for 1–2 months compared with those in patients who did not undergo thrombolysis. Our results highlight the usefulness of ¹H-MRS-based metabolomics as a feasible and efficient prognostic tool for assessing the treatment effect of acute cerebral infarction.

Imaging Stroke Evolution after Middle Cerebral Artery Occlusion in Non-human Primates

This article reviews imaging approaches applied to the study of stroke in nonhuman primates. We briefly survey the various surgical and minimally invasive experimental stroke models in nonhuman primates, followed by a summary of studies using computed tomography, positron emission tomography and magnetic resonance imaging and spectroscopy to monitor stroke from the hyperacute phase (within minutes of the onset of cerebral ischemia) to the chronic phase (1 month and beyond).

Choline and creatine are not reliable denominators for calculating metabolite ratios in acute ischemic stroke

BACKGROUND AND PURPOSE

Choline and creatine are commonly used as denominators for other metabolites in ischemic stroke spectroscopy, assuming that they do not change. We investigated their concentration variation over time after stroke.

METHODS

Choline and creatine concentrations were measured by proton MR spectroscopic imaging in 51 patients at 5 times up to 3 months after stroke.

RESULTS

Choline and creatine levels changed significantly in the ischemic region. Choline was significantly reduced during the first 2 weeks after stroke onset (P=0.034). Creatine was significantly reduced during the whole period of the study (P=0.011).

CONCLUSIONS

Choline and creatine concentrations are not reliable denominators for metabolite ratios in acute stroke because their levels vary significantly in ischemic brain regions.

Metabolic alterations and neurodevelopmental outcome of infants with transposition of the great arteries

Abnormal neurodevelopment has been reported for infants who were born with transposition of the great arteries (TGA) and underwent arterial switch operation (ASO). This study evaluates the cerebral metabolism of TGA infants at birth and before ASO and neurodevelopment 1 year after ASO. Proton magnetic resonance spectroscopy (1H-MRS) was performed on 16 full-term TGA brains before ASO within 3-6 days after birth. The brain metabolite ratios of [NAA/Cr], [Cho/Cr], and [mI/Cr] evaluated measured. Ten infants were evaluated at 1 year using the Bayley Scales of Infants Development II (BSED II). Cerebral metabolism of infants with TGA was altered in parietal white matter (PWM) and occipital gray matter (OGM) at birth before ASO. One year after ASO, [Cho/Cr] in PWM remained altered, but all metabolic ratios in OGM were normal. The results of BSID II at 1 year showed delayed mental and psychomotor development. This delayed neurodevelopmental outcome may reflect consequences of the altered cerebral metabolism in PWM measured by 1H-MRS. It is speculated that the abnormal hemodynamics due to TGA in utero may be responsible for the impaired cerebral metabolism and the subsequent neurodevelopmental deficit.

MR imaging and 1H-MR spectroscopy in a case of cerebral infarction with transient cerebral arteriopathy

A case of cerebral infarction with transient cerebral arteriopathy in a 12-year-old female is described. The child showed with an acute onset of left hemiplegia, central facial palsy and aphasia. She was diagnosed with right internal carotid artery obstruction with no predisposing factors for cerebral infarction. A serial MR image and MR spectroscopy of the brain was performed. MR angiography revealed reversible vascular changes in the right middle cerebral artery after several months. The ratio of choline/creatine was elevated and that of N-acetylaspartate (NAA)/creatine was depressed in the cerebral lesion, however, they were normalized during the remission phase with long echo time-MR spectroscopy. The elevation of the lactate peak was clarified with short echo time-MR spectroscopy. The longitudinal follow up using MR angiography, and MR spectroscopy with long and short echo time was useful for the evaluation of reversible vascular change with cerebral infarction in children.

The haemodynamic effect of carotid endarterectomy

OBJECTIVES

to assess the haemodynamic effect of carotid artery surgery, and to relate postoperative changes to the state of cerebral circulation before revascularisation.

MATERIALS AND METHODS

using transcranial Doppler we studied bilateral middle cerebral artery (MCA) flow velocities before and on 1st day, 2nd or 3rd day and 4th or 5th day and 3 months after carotid surgery in 61 patients. In addition, ipsilateral MCA flow velocity was monitored continuously during surgery. Data were related to the internal carotid artery (ICA) perfusion pressure (cerebral perfusion pressure index, CPPI), measured directly before ICA clamping.

RESULTS

postoperatively, MCA flow velocities increased significantly overall (p<0.01), mainly due to pronounced and longer lasting flow velocities in the group of 18 patients with CPPI<0.7 (p<0.05). Flow velocities peaked - absolute as well as relative - on the first postoperative day and then gradually levelled off to reach preoperative values after 4-5 days in patients with high CPPI, whereas MCA flow velocities remained increased in the group of patients with low CPPI. At 3 months flow velocities in both groups were normalised. New neurological symptoms occurred in four patients, who all had low CPPI preoperatively (22% (4/18) vs 0%; Fisher's exact test: p=0.006).

CONCLUSION

some degree of hyperperfusion was seen in most patients, but the changes were significantly more pronounced in patients with preoperative hypoperfusion, who also suffered significantly more neurological complications.