Assessment of Mendelian and risk-factor genes in Alzheimer disease: A prospective nationwide clinical utility study and recommendations for genetic screening

PURPOSE

To assess the likely pathogenic/pathogenic (LP/P) variants rates in Mendelian dementia genes and the moderate-to-strong risk factors rates in patients with Alzheimer disease (AD).

METHODS

We included 700 patients in a prospective study and performed exome sequencing. A panel of 28 Mendelian and 6 risk-factor genes was interpreted and returned to patients. We built a framework for risk variant interpretation and risk gradation and assessed the detection rates among early-onset AD (EOAD, age of onset (AOO) ≤65 years, n = 608) depending on AOO and pedigree structure and late-onset AD (66 < AOO < 75, n = 92).

RESULTS

Twenty-one patients carried a LP/P variant in a Mendelian gene (all with EOAD, 3.4%), 20 of 21 affected APP, PSEN1, or PSEN2. LP/P variant detection rates in EOAD ranged from 1.7% to 11.6% based on AOO and pedigree structure. Risk factors were found in 69.5% of the remaining 679 patients, including 83 (12.2%) being heterozygotes for rare risk variants, in decreasing order of frequency, in TREM2, ABCA7, ATP8B4, SORL1, and ABCA1, including 5 heterozygotes for multiple rare risk variants, suggesting non-monogenic inheritance, even in some autosomal-dominant-like pedigrees.

CONCLUSION

We suggest that genetic screening should be proposed to all EOAD patients and should no longer be prioritized based on pedigree structure.

Prevalence of carotid web in a French cohort of cryptogenic stroke

BACKGROUND AND PURPOSE

Carotid webs (CaW) may be an under-recognized cause of anterior circulation cryptogenic ischemic stroke (ACIS). Prevalence is still unknown in European patients with ACIS.

OBJECTIVE

To evaluate the prevalence of CaW in ACIS and describe patients with CaW phenotype in a cohort of patients from a French stroke center.

METHODS

We conducted a retrospective monocentric cohort study from 01/01/2015 to 31/12/2019 (Montpellier University Hospital, France), in consecutive anterior ischemic stroke (AIS) patients ≤65 years old from a prospective stroke database. Using ASCOD phenotyping, ACIS patients were selected and cervical CTA were reviewed to find CaW.

RESULTS

Among 1053 consecutive AIS patients, 266 ACIS patients with CTA were included. Among patients included (mean age 50, women 58%), CaW was in the ipsilateral carotid (iCaW) in 21 patients: 7.9% (95%CI [4.6-11.1]), (mean age 51, 11 women, 16 Caucasian). iCaW were uncovered during study review of CTA in 6/21 (29%) patients. Comparison between patients with iCaW and those without iCaW showed no differences except that of a higher rate of intracranial large vessel occlusion (LVO) (62.4 vs 37.6%; p = 0.03). Patients with iCaW under conservative medical therapy had an annualized stroke recurrence rate (SRR) of 11.4% (95%CI [8.4-15.1].

CONCLUSIONS

iCaW was identified as a source of stroke in about 8% of a French population ≤65 years with ACIS. iCaW was associated with a higher rate of LVO and a high SRR under conservative medical therapy.

Carotid webs associated with ischemic stroke. Updated general review and research directions

Carotid web (CaW) is an intimal variant of fibromuscular dysplasia strongly associated with ipsilateral cerebral infarction. Although considered rare, it is a recent and increasing concern for physicians involved in stroke diagnosis and management. The present general review relies on a systematic literature analysis and aims to update readers on the latest knowledge in the field of symptomatic CaW (syCaW). CaW associated with ipsilateral cerebral infarction or transient ischemic attack has been identified in 189 patients. Ischemic strokes (IS) mostly occur in middle age (mean 46 years) and predominately in females (66%). The high frequency of African descendant patients among case reports and series (58%) suggests an ethnic susceptibility for CaW development. CaW features are characterised by a shelf-like intraluminal defect on contrast sagittal imaging, a linear defect that splits the lumen on axial section, a post-contrast stagnation rostral to the lesion and a frequent contralateral mirrored CaW (26.6%). An artery-to-artery embolism mechanism is widely accepted via CaW blood stasis, thrombus formation and clot fragmentation scattered by blood flow. Therefore, cerebral infarctions are often large related to a high proportion of proximal occlusion (62.5%). CaW confers a high rate of IS recurrence despite standard anti-platelet treatment that reaches 33.3% of patients prospectively followed with a median time to event of one year. Although no randomised therapeutic studies are available, surgery (n=39) or stenting (n=50) have been often proposed and seem to avoid recurrences. CaW clearly emerges as a cause of cryptogenic embolic stroke and should be systematically investigated in routine. A large number of points remain to be elucidated and CaW patients should be steadily included in registries and randomised therapeutic studies.