Extension of the Clinicoradiologic Spectrum of Newly Described End-Truncating LAMB1 Variations

Objectives

To refine the clinical spectrum of a very recently identified phenotype associated with LAMB1 end-truncating pathogenic variations.

Methods

Detailed clinical, neuropsychological, and MRI investigation of 6 patients from 2 unrelated families segregating end-truncating LAMB1 variations.

Results

All patients harbored a LAMB1 end-truncating pathogenic variation. The specific association of a hippocampal type episodic memory dysfunction and a diffuse leukoencephalopathy was observed in all 4 patients aged older than 50 years, slightly worsening over time in 2 patients with several years of follow-up. Additional unspecific neurologic symptoms are reported, such as episodes of numbness, language troubles, or faintness in these 4 patients and the 2 younger ones.

Discussion

The association of an extensive leukoencephalopathy with an episodic memory dysfunction of the hippocampal type is strongly suggestive of a LAMB1 end-truncating variation in adults older than 50 years. Early cognitive complaints and imaging abnormalities might exist decades before. Additional transient manifestations can be observed, and this association should lead to LAMB1 screening to avoid unnecessary invasive investigations.

Heterozygous HTRA1 nonsense or frameshift mutations are pathogenic

Heterozygous missense HTRA1 mutations have been associated with an autosomal dominant cerebral small vessel disease (CSVD) whereas the pathogenicity of heterozygous HTRA1 stop codon variants is unclear. We performed a targeted high throughput sequencing of all known CSVD genes, including HTRA1, in 3853 unrelated consecutive CSVD patients referred for molecular diagnosis. The frequency of heterozygous HTRA1 mutations leading to a premature stop codon in this patient cohort was compared with their frequency in large control databases. An analysis of HTRA1 mRNA was performed in several stop codon carrier patients. Clinical and neuroimaging features were characterized in all probands. Twenty unrelated patients carrying a heterozygous HTRA1 variant leading to a premature stop codon were identified. A highly significant difference was observed when comparing our patient cohort with control databases: gnomAD v3.1.1 [P = 3.12 × 10-17, odds ratio (OR) = 21.9], TOPMed freeze 5 (P = 7.6 × 10-18, OR = 27.1) and 1000 Genomes (P = 1.5 × 10-5). Messenger RNA analysis performed in eight patients showed a degradation of the mutated allele strongly suggesting a haploinsufficiency. Clinical and neuroimaging features are similar to those previously reported in heterozygous missense mutation carriers, except for penetrance, which seems lower. Altogether, our findings strongly suggest that heterozygous HTRA1 stop codons are pathogenic through a haploinsufficiency mechanism. Future work will help to estimate their penetrance, an important information for genetic counselling.

Management of acute central retinal artery occlusion: Intravenous thrombolysis is feasible and safe

Background

Although acute central retinal artery occlusion is as a stroke in the carotid territory (retinal artery), its management remains controversial. The aim of this study was to assess the feasibility and safety of intravenous thrombolysis delivered within 6 h of central retinal artery occlusion in French stroke units.

Methods

We performed a retrospective analysis of patients treated with intravenous alteplase (recombinant tissue-plasminogen activator), based on stroke units thrombolysis registers from June 2005 to June 2015, and we selected those who had acute central retinal artery occlusion. The feasibility was assessed by the ratio of patients that had received intravenous alteplase within 6 h after central retinal artery occlusion onset among those who had been admitted to the same hospital for acute central retinal artery occlusion. All adverse events were documented.

Results

Thirty patients were included. Visual acuity before treatment was limited to “hand motion”, or worse, in 90% of the cases. The mean onset-to-needle time was 273 min. The individuals treated with intravenous alteplase for central retinal artery occlusion represented 10.2% of all of the patients hospitalized for central retinal artery occlusion in 2013 and 2014. We observed one occurrence of major bleeding, a symptomatic intracerebral hemorrhage.

Conclusion

When applied early on, intravenous thrombolysis appears to be feasible and safe, provided that contraindications are given due consideration. Whether intravenous thrombolysis is more effective than conservative therapy remains to be determined. In order to conduct a well-designed prospective randomized control trial, an organized network should be in place.

[The finding of incidental intracranial lesions with magnetic resonance imaging]

INTRODUCTION

Incidental findings on brain MRI are not rare since the development of MRI as a diagnostic and clinical research tool.

STATE OF THE ART

Prevalence of cerebral incidental finding, based on research volunteers participating in studies, is estimated from 1.7 to 4 percent. The most frequently detected lesions are intracranial tumors (meningioma, arachnoid cysts, neuro-epithelial tumor) and vascular malformations.

PERSPECTIVES

A better knowledge of the spontaneous outcome of incidental findings would allow adequate management of these patients.

CONCLUSION

Clinicians should be aware of the outcome of incidental findings, to reassure patients or trigger a work-up if necessary.