Magnetic resonance imaging and brain injury in the chronic phase after aneurysmal subarachnoid hemorrhage: A systematic review

Therapeutic potential of stem cells in subarachnoid hemorrhage

Aneurysm rupture can result in subarachnoid hemorrhage, a condition with potentially severe consequences, such as disability and death. In the acute stage, early brain injury manifests as intracranial pressure elevation, global cerebral ischemia, acute hydrocephalus, and direct blood-brain contact due to aneurysm rupture. This may subsequently cause delayed cerebral infarction, often with cerebral vasospasm, significantly affecting patient outcomes. Chronic complications such as brain volume loss and chronic hydrocephalus can further impact outcomes. Investigating the mechanisms of subarachnoid hemorrhage-induced brain injury is paramount for identifying effective treatments. Stem cell therapy, with its multipotent differentiation capacity and anti-inflammatory effects, has emerged as a promising approach for treating previously deemed incurable conditions. This review focuses on the potential application of stem cells in subarachnoid hemorrhage pathology and explores their role in neurogenesis and as a therapeutic intervention in preclinical and clinical subarachnoid hemorrhage studies.

TREM2 alleviates long-term cognitive dysfunction after subarachnoid hemorrhage in mice by attenuating hippocampal neuroinflammation via PI3K/Akt signaling pathway

Subarachnoid hemorrhage (SAH) often leads to long-term cognitive deficits in patients, particularly due to injury to brain regions such as the hippocampus. This study aims to investigate the role of the triggering receptor expressed on myeloid cells 2 (TREM2) in mitigating hippocampal injury and associated cognitive impairments following SAH. To explore the protective effects of TREM2, we utilized the TREM2 agonist COG1410 to upregulate TREM2 expression and employed TREM2 knockout (KO) mice to verify the necessity of TREM2 for this protective role. The study further examined the involvement of the PI3K/Akt signaling pathway in TREM2-mediated neuroprotection. Our findings indicate that the upregulation of TREM2 significantly alleviated long-term cognitive deficits and promoted the recovery of hippocampal neural activity post-SAH. The neuroprotective effects were linked to reduced microglial activation and decreased secretion of inflammatory factors within the hippocampus. In contrast, TREM2 KO mice did not exhibit these protective effects. Furthermore, inhibition of the PI3K/Akt pathway also diminished these protective effects of TREM2 upregulation and worsened cognitive outcomes. In conclusion, TREM2 upregulation mitigates long-term cognitive dysfunction following SAH by attenuating hippocampal neuroinflammation via the PI3K/Akt signaling pathway. These findings suggest that TREM2 could be a potential therapeutic target for improving cognitive outcomes after SAH.

Advanced Diffusion Tensor Imaging in White Matter Injury After Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) is recognized as an especially severe stroke variant, notorious for its high mortality and long-term disability rates, in addition to a range of both immediate and enduring neurologic impacts. Over half of the SAH survivors experience varying degrees of neurologic disorders, with many enduring chronic neuropsychiatric conditions. Due to the limitations of traditional imaging techniques in depicting subtle changes within brain tissues posthemorrhage, the accurate detection and diagnosis of white matter (WM) injuries are complicated. Against this backdrop, diffusion tensor imaging (DTI) has emerged as a promising biomarker for structural imaging, renowned for its enhanced sensitivity in identifying axonal damage. This capability positions DTI as an invaluable tool for forming precise and expedient prognoses for SAH survivors. This study synthesizes an assessment of DTI for the diagnosis and prognosis of neurologic dysfunctions in patients with SAH, emphasizing the notable changes observed in DTI metrics and their association with potential pathophysiological processes. Despite challenges associated with scanning technology differences and data processing, DTI demonstrates significant clinical potential for early diagnosis of cognitive impairments following SAH and monitoring therapeutic effects. Future research requires the development of highly standardized imaging paradigms to enhance diagnostic accuracy and devise targeted therapeutic strategies for SAH patients. In sum, DTI technology not only augments our understanding of the impact of SAH but also may offer new avenues for improving patient prognoses.

Automated magnetic resonance imaging quantification of cerebral parenchymal and ventricular volume following subarachnoid hemorrhage: associations with cognition

This study aims to investigate cerebral parenchymal and ventricular volume changes after subarachnoid hemorrhage (SAH) and their potential association with cognitive impairment. 17 patients with aneurysmal SAH (aSAH) and 21 patients with angiographically negative SAH (anSAH) without visually apparent parenchymal loss on conventional magnetic resonance imaging (MRI) were included, along with 76 healthy controls. Volumetric analyses were performed using an automated clinical segmentation and quantification tool. Measurements were compared to on-board normative reference database (n = 1923) adjusted for age, sex, and intracranial volume. Cognition was assessed with tests for psychomotor speed, attentional control, (working) memory, executive functioning, and social cognition. All measurements took place 5 months after SAH. Lower cerebral parenchymal volumes were most pronounced in the frontal lobe (aSAH: n = 6 [35%], anSAH n = 7 [33%]), while higher volumes were most substantial in the lateral ventricle (aSAH: n = 5 [29%], anSAH n = 9 [43%]). No significant differences in regional brain volumes were observed between both SAH groups. Patients with lower frontal lobe volume exhibited significantly lower scores in psychomotor speed (U = 81, p = 0.02) and attentional control (t = 2.86, p = 0.004). Additionally, higher lateral ventricle volume was associated with poorer memory (t = 3.06, p = 0.002). Regional brain volume changes in patients with SAH without visible parenchymal abnormalities on MRI can still be quantified using a fully automatic clinical-grade tool, exposing changes which may contribute to cognitive impairment. Therefore, it is important to provide neuropsychological assessment for both SAH groups, also including those with clinically mild symptoms.

Benign Paroxysmal Positional Vertigo and Occult Subarachnoid Hemorrhage Complicated after Head Trauma

Benign paroxysmal positional vertigo (BPPV) is the most prevalent form of peripheral vertigo and is common in posttraumatic patients. Sometimes, posttraumatic BPPV and subarachnoid hemorrhage (SAH) exist together. How to effectively recognize SAH especially concealed bleeding before maneuver treatment for BPPV is worth paying attention by every clinician. Presently described is a case that when there are some clinical symptoms cannot be completely explained by simple BPPV, the combination of CT and FLAIR MRI sequences are needed in the early-stage detection of acute SAH.

Gray-to-white matter ratio predicts long-term recovery potential of patients with aneurysmal subarachnoid hemorrhage

Predicting recovery potential of patients with aneurysmal subarachnoid hemorrhage (aSAH) is challenging. We investigated whether the gray-to-white matter ratio (GWR) predicts recovery of cognitive function (CF) and quality of life (QOL) of these patients. We analyzed data of 69 patients with aSAH. Patients' demographics, comorbidities, and neurological status were recorded. One year after aSAH, Montreal Cognitive Assessment (MoCA) and Short Form-36 (SF-36) tests were administered to the patients, and brain volumes of patients were examined using MRI. Three years after aSAH, MoCA and SF-36 tests were conducted again. Differences between the test scores 1 and 3 years after aSAH were evaluated (ΔMoCA and ΔSF-36). Patients with ΔMoCA ≥ 4 points and those with ΔSF-36 ≥ 8 points were referred to as good MoCA and SF-36 recovery, respectively. ΔMoCA correlated with GWR in male and female patients (females: p < 0.001, R² = 0.581; males: p < 0.001, R² = 0.481). In female patients, GWR > 1.34 predicted good MoCA recovery with 82.3% sensitivity and 80% specificity, and in male patients, GWR > 1.36 predicted good MoCA recovery with 80% sensitivity and 95% specificity. ΔSF-36 correlated with GWR in male and female patients (females: p < 0.001, R² = 0.479; males: p < 0.001, R² = 0.627). In female patients, GWR > 1.35 predicted good SF-36 recovery with 74% sensitivity and 84% specificity, and in male patients, GWR > 1.38 predicted good SF-36 recovery with 72% sensitivity and 92% specificity. GWR is a good predictor of the recovery of CF and QOL in patients with aSAH and, thus, can help physicians to better organize rehabilitation of patients.