The emerging genetic landscape of cerebral white matter hyperintensities

PLEKHG1: New Potential Candidate Gene for Periventricular White Matter Abnormalities

Hypoxic-ischemic brain damage presents a significant neurological challenge, often manifesting during the perinatal period. Specifically, periventricular leukomalacia (PVL) is emerging as a notable contributor to cerebral palsy and intellectual disabilities. It compromises cerebral microcirculation, resulting in insufficient oxygen or blood flow to the periventricular region of the brain. As widely documented, these pathological conditions can be caused by several factors encompassing preterm birth (4-5% of the total cases), as well single cotwin abortion and genetic variants such as those associated with GTPase pathways. Whole exome sequencing (WES) analysis identified a de novo causative variant within the pleckstrin homology domain-containing family G member 1 (PLEKHG1) gene in a patient presenting with PVL. The PLEKHG1 gene is ubiquitously expressed, showing high expression patterns in brain tissues. PLEKHG1 is part of a family of Rho guanine nucleotide exchange factors, and the protein is essential for cell division control protein 42 (CDC42) activation in the GTPase pathway. CDC42 is a key small GTPase of the Rho-subfamily, regulating various cellular functions such as cell morphology, migration, endocytosis, and cell cycle progression. The molecular mechanism involving PLEKHG1 and CDC42 has an intriguing role in the reorientation of cells in the vascular endothelium, thus suggesting that disruption responses to mechanical stress in endothelial cells may be involved in the formation of white matter lesions. Significantly, CDC42 association with white matter abnormalities is underscored by its MIM phenotype number. In contrast, although PLEKHG1 has been recently associated with patients showing white matter hyperintensities, it currently lacks a MIM phenotype number. Additionally, in silico analyses classified the identified variant as pathogenic. Although the patient was born prematurely and subsequently to dichorionic gestation, during which its cotwin died, we suggest that the variant described can strongly contribute to PVL. The aim of the current study is to establish a plausible association between the PLEKHG1 gene and PVL.

The cerebellar white matter lesions in dentatorubral-pallidoluysian atrophy

Dentatorubral-pallidoluysian atrophy (DRPLA) is an autosomal dominant neurodegenerative disorder caused by a CAG nucleotide repeat expansion in atrophin 1. A previous report described cerebellar white matter lesions on magnetic resonance imaging (MRI) in elderly-onset DRPLA patients, but this finding has not been fully investigated in a total population of DRPLA patients, including juvenile or early-adult onset patients. Herein, we attempted to determine the frequency, distribution pattern, and features of the cerebellar white matter lesions in 30 consecutive DRPLA patients. We also assessed the relationships between the cerebellar white matter lesions and clinical parameters and other MRI findings. The cerebellar white matter lesions were found in 43% of the 30 DRPLA patients, and in 70% of the late adult-onset DRPLA patients. In approx. Two-thirds of the patients with cerebellar white matter lesions, the lesions were localized in the paravermal area (paravermal lesions). Multiple logistic regression analyses revealed that the Fazekas grade of 'cerebral' white matter lesions was independently associated with 'cerebellar' white matter lesions. In conclusion, cerebellar white matter lesions are one of the distinctive MRI features in DRPLA patients, especially in patients with older age at onset. Cerebellar white matter lesions, as well as cerebral white matter lesions, might originate from the disease process of DRPLA itself, and they often have a characteristic distribution of paravermal lesions.

Risk factors of white matter hyperintensities in South Asian patients with transient ischemic attack and minor stroke

PURPOSE

Aging and increased burden of cardiovascular risk factors are associated with severity of white matter hyperintensity (WMH). We assessed the burden and risk factor profile of WMHs in South Asian patients with transient ischemic attack (TIA) and minor stroke.

METHODS

Patients with acute ischemic stroke with the National Institute of Health stroke scale (NIHSS) score ≤ 5 who underwent MRI were included. The severity of WMHs was assessed based on age-related white matter change (ARWMC) scale (0-30). A score of > 8 or more was considered moderate-severe involvement. Logistic regression analysis was performed to assess the association with risk factors.

RESULTS

A total of 424 patients with a mean ± SD age of 57.4 ± 14.5 years [females, 108 (25.5%)] were analyzed. Fifty-four (12.7%) patients had moderate or severe WMHs (ARWMC score > 8). Age (OR 1.03, 95% CI 1.01-1.06; p = 0.004), hypertension (OR 2.3, 95% CI 1.1-5.1; p = 0.03) and smoking tobacco (OR 2.8, 95% CI 1.4-5.6; p = 0.003) were independently associated with ARWMC score > 8. The median (IQR) regional score in patients with ARWMC score > 8 was maximum in frontal areas 4 (4-6, p < 0.0001) and parietooccipital areas 4.5(4-6, p < 0.0001). The presence of microbleeds (OR 6.3, 95% CI 3.1-12.7; p < 0.0001) was independently associated with ARWMC score > 8.

CONCLUSION

South Asian patients with TIA and minor stroke are relatively young, and few patients have moderate and severe WMHs. Hypertension and tobacco smoking increases the risk of WMH. Targeting modifiable risk factors may reduce the burden of WMHs and vascular dementia.

Is There Equipoise Regarding the Optimal Medical Treatment of Patients with Asymptomatic White Matter Hyperintensities?

BACKGROUND

White matter hyperintensity (WMH) is a common manifestation of chronic ischemic microvascular disease that heralds greater risk of functional disability, stroke, and dementia. SPRINT MIND recently reported that intensive blood pressure reduction resulted in lower rates of mild cognitive impairment and WMH progression, suggesting that medical interventions could have a measurable impact on WMH. We conducted an anonymous survey of providers in the NINDS StrokeNet to better understand neurologist attitudes about asymptomatic WMH.

METHODS

We sent a 7-question survey to the 29 Regional Coordinating Centers of the StrokeNet, whose coordinators disseminated the survey to providers "involved in the care of a patient after their stroke."

RESULTS

We received 136 responses. For stroke prevention therapies, including aspirin and statin therapy and blood pressure target, there was substantial equipoise, with no single option receiving >50% endorsement and between 15-32% of respondents choosing the option of "not sure." 83% of respondents indicated high or moderate enthusiasm for a trial targeting this patient population. The clinical outcomes of reduction in ischemic stroke, cognitive impairment, or dementia were high importance (>70% endorsement), while the remaining radiographic, safety, and clinical endpoints all failed to reach 50% endorsement.

CONCLUSIONS

Our survey establishes meaningful neurologist attitudes that can inform future WMH research. There is considerable equipoise regarding optimal medical treatment for patients with asymptomatic WMH and providers in StrokeNet, who would be a vital stakeholder in WMH research in the United States, enthusiastically support a clinical trial to resolve open questions on optimal medical management.