The Posterior Limb of the Internal Capsule as the Subcortical Transitional Zone of the Anterior and Posterior Circulations: Insights from Human 7T MRI

Posterior Limb of Internal Capsule Infarct Predicts Functional Outcome in Acute Terminal Internal Carotid Artery Occlusion After Thrombectomy

PURPOSES

This study investigated the impact of posterior limb of internal capsule (PLIC) infarct on outcomes of acute internal carotid artery (ICA) occlusion after endovascular thrombectomy (EVT) and the diagnostic accuracy of pretreatment noncontrast computerized tomography (NCCT) and computerized tomography angiography (CTA) findings.

METHODS

Patients who underwent EVT for acute ICA occlusion between September 2014 and August 2020 were included in the study. The patients were dichotomized as PLIC infarct or spared. The risk factors for PLIC infarct were investigated, and the association between infarct patterns and clinical outcomes were assessed using logistic regression analysis. Pretreatment NCCT and CTA findings, including PLIC hypodensity, choroid plexus enhancement (CPE), and posterior cerebral artery (PCA) flow status, were calculated for diagnosis of PLIC infarct.

RESULTS

Among 72 patients, the mean age was 70.9 years, and the mean stroke scale was 19.4. PLIC infarct was identified in 15 patients (20.8%). PLIC infarct was associated with worse 90-day functional outcome (P = 0.01, shift test). Lack of CPE is the only independent predictor of PLIC infarct (odds ratio: 127.48, P = 0.001). Lack of CPE and impaired PCA flow produce greater diagnostic accuracy for PLIC infarct than does NCCT hypodensity (area under the receiver operating characteristics curve: 0.85 and 0.76, P = 0.0005 and 0.02, respectively).

CONCLUSIONS

In acute ICA occlusion, PLIC infarct is an independent risk factor for worse clinical outcome at 90 days. The lack of CPE was associated with PLIC infarct, and pretreatment CTA can be useful for early diagnosis.

Neuroimaging at 7 Tesla: a pictorial narrative review

Neuroimaging using the 7-Tesla (7T) human magnetic resonance (MR) system is rapidly gaining popularity after being approved for clinical use in the European Union and the USA. This trend is the same for functional MR imaging (MRI). The primary advantages of 7T over lower magnetic fields are its higher signal-to-noise and contrast-to-noise ratios, which provide high-resolution acquisitions and better contrast, making it easier to detect lesions and structural changes in brain disorders. Another advantage is the capability to measure a greater number of neurochemicals by virtue of the increased spectral resolution. Many structural and functional studies using 7T have been conducted to visualize details in the white matter and layers of the cortex and hippocampus, the subnucleus or regions of the putamen, the globus pallidus, thalamus and substantia nigra, and in small structures, such as the subthalamic nucleus, habenula, perforating arteries, and the perivascular space, that are difficult to observe at lower magnetic field strengths. The target disorders for 7T neuroimaging range from tumoral diseases to vascular, neurodegenerative, and psychiatric disorders, including Alzheimer's disease, Parkinson's disease, multiple sclerosis, epilepsy, major depressive disorder, and schizophrenia. MR spectroscopy has also been used for research because of its increased chemical shift that separates overlapping peaks and resolves neurochemicals more effectively at 7T than a lower magnetic field. This paper presents a narrative review of these topics and an illustrative presentation of images obtained at 7T. We expect 7T neuroimaging to provide a new imaging biomarker of various brain disorders.

Association Between Anatomical Location and Hematoma Expansion in Deep Intracerebral Hemorrhage

Objective

To establish the relationship between hematoma sites of involvement and hematoma expansion (HE) in patients with deep intracerebral hemorrhage (ICH).

Methods

Eligible patients with deep ICH admitted to hospital within 6 hours of onset between 2018 and 2020 were included in this retrospective multi-center study. Individuals with secondary ICH were excluded. The volume of HE was evaluated based on admission and follow-up computed tomography scans. Associations between deep ICH sites of involvement and HE were examined using multivariable logistic regression analysis while adjusting for confounding covariates of HE.

Results

We enrolled 583 individuals from three stroke centers. Data from a final total of 460 patients were used in the analysis; of these patients, 159 (34.6%) had HE. In the crude model without adjustment, external capsule, anterior limb of the internal capsule, and posterior limb of the internal capsule (PLIC) involvement were correlated with HE. After fully adjusted models for sex, age, intraventricular hemorrhage, Glasgow Coma Scale admission score, baseline ICH volume, and time from onset to initial computed tomography, multivariable logistic regression revealed that the PLIC is a robust predictor of HE in patients with deep ICH (adjusted odds ratio = 2.73; 95% confidence interval = 1.75–4.26; p < 0.001).

Conclusion

Involvement of the posterior limb of the internal capsule in deep hemorrhage could be a promising predictor of HE.

Lenticulostriate Arteries and Basal Ganglia Changes in Cerebral Autosomal Dominant Arteriopathy With Subcortical Infarcts and Leukoencephalopathy, a High-Field MRI Study

Background and Purpose: Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) mainly affects the cerebral small arteries. We aimed to analyze changes in the lenticulostriate arteries (LSAs) and the basal ganglia in patients with CADASIL using high-field magnetic resonance imaging (7.0-T MRI).

Methods: We examined 46 patients with CADASIL and 46 sex- and age-matched healthy individuals using 7.0-T MRI. The number and length of the LSAs, and the proportion of discontinuous LSAs were compared between the two groups. The Mini-Mental State Examination score, the modified Rankin Scale, the Barthel Index, and the MRI lesion load of the basal ganglia were also examined in patients with CADASIL. We analyzed the association between LSA measurements and the basal ganglia lesion load, as well as the association between LSA measurements and clinical phenotypes in this patient group.

Results: We observed a decrease in the number of LSA branches (t = −2.591, P = 0.011), and an increase in the proportion of discontinuous LSAs (z = −1.991, P = 0.047) in patients with CADASIL when compared with healthy controls. However, there was no significant difference in the total length of LSAs between CADASIL patients and healthy individuals (t = −0.412, P = 0.682). There was a positive association between the number of LSA branches and the Mini-Mental State Examination scores of CADASIL patients after adjusting for age and educational level (β = 0.438; 95% CI: 0.093, 0.782; P = 0.014). However, there was no association between LSA measurements and the basal ganglia lesion load among CADASIL patients.

Conclusions: 7.0-T MRI provides a promising and non-invasive method for the study of small artery damage in CADASIL. The abnormalities of small arteries may be related to some clinical symptoms of CADASIL patients such as cognitive impairment. The lack of association between LSA measurements and the basal ganglia lesion load among the patients suggests that changes in the basal ganglia due to CADASIL are caused by mechanisms other than anatomic narrowing of the vessel lumen.

Association Between Duration of Dysphagia Recovery and Lesion Location on Magnetic Resonance Imaging in Patients With Middle Cerebral Artery Infarction

OBJECTIVE

To investigate association between lesion location on magnetic resonance imaging (MRI) performed after an infarction and the duration of dysphagia in middle cerebral artery (MCA) infarction.

METHODS

A videofluoroscopic swallowing study was performed for 59 patients with dysphagia who were diagnosed as cerebral infarction of the MCA territory confirmed by brain MRI. Lesions were divided into 11 regions of interest: primary somatosensory cortex, primary motor cortex, supplementary motor cortex, anterior cingulate cortex, orbitofrontal cortex, parieto-occipital cortex, insular cortex, posterior limb of the internal capsule (PLIC), thalamus, basal ganglia (caudate nucleus), and basal ganglia (putamen). Recovery time was defined as the period from the first day of L-tube feeding to the day that rice porridge with thickening agent was prescribed. Recovery time and brain lesion patterns were compared and analyzed.

RESULTS

The mean recovery time of all patients was 26.71±16.39 days. The mean recovery time was 36.65±15.83 days in patients with PLIC lesions and 32.6±17.27 days in patients with caudate nucleus lesions. Only these two groups showed longer recovery time than the average recovery time for all patients. One-way analysis of variance for recovery time showed significant differences between patients with and without lesions in PLIC and caudate (p<0.001).

CONCLUSION

Injury to both PLIC and caudate nucleus is associated with longer recovery time from dysphagia.