Pierre Landrieu

Mutations involved in Aicardi-Goutieres syndrome implicate SAMHD1 as regulator of the innate immune response

Aicardi-Goutières syndrome is a mendelian mimic of congenital infection and also shows overlap with systemic lupus erythematosus at both a clinical and biochemical level. The recent identification of mutations in TREX1 and genes encoding the RNASEH2 complex and studies of the function of TREX1 in DNA metabolism have defined a previously unknown mechanism for the initiation of autoimmunity by interferon-stimulatory nucleic acid. Here we describe mutations in SAMHD1 as the cause of AGS at the AGS5 locus and present data to show that SAMHD1 may act as a negative regulator of the cell-intrinsic antiviral response.

The gene encoding gigaxonin, a new member of the cytoskeletal BTB/kelch repeat family, is mutated in giant axonal neuropathy

Disorganization of the neurofilament network is a prominent feature of several neurodegenerative disorders including amyotrophic lateral sclerosis (ALS), infantile spinal muscular atrophy and axonal Charcot-Marie-Tooth disease. Giant axonal neuropathy (GAN, MIM 256850), a severe, autosomal recessive sensorimotor neuropathy affecting both the peripheral nerves and the central nervous system, is characterized by neurofilament accumulation, leading to segmental distension of the axons. GAN corresponds to a generalized disorganization of the cytoskeletal intermediate filaments (IFs), to which neurofilaments belong, as abnormal aggregation of multiple tissue-specific IFs has been reported: vimentin in endothelial cells, Schwann cells and cultured skin fibroblasts, and glial fibrillary acidic protein (GFAP) in astrocytes. Keratin IFs also seem to be alterated, as most patients present characteristic curly or kinky hairs. We report here identification of the gene GAN, which encodes a novel, ubiquitously expressed protein we have named gigaxonin. We found one frameshift, four nonsense and nine missense mutations in GAN of GAN patients. Gigaxonin is composed of an amino-terminal BTB (for Broad-Complex, Tramtrack and Bric a brac) domain followed by a six kelch repeats, which are predicted to adopt a β-propeller shape. Distantly related proteins sharing a similar domain organization have various functions associated with the cytoskeleton, predicting that gigaxonin is a novel and distinct cytoskeletal protein that may represent a general pathological target for other neurodegenerative disorders with alterations in the neurofilament network.

Stroke in Childhood: Outcome and Recurrence Risk by Mechanism in 59 Patients:

This paper describes 59 patients, 3 months to 16 years of age, who were seen consecutively in the same center for cerebral arterial infarction. It focuses on the mechanism of stroke. The pathophysiologic process could be established for 78% of the children. Arteriopathic stroke (31 patients, or 53%) was the most common. The arteriopathies were either progressive (moyamoya in 4 patients, or 7%) or nonprogressive (27 patients, or 46%). The latter form occurred in two patterns: dissection of cervicocephalic arteries (12 patients, or 20%) and transient cerebral arteriopathy of unknown origin but probably angiitis (15 patients, or 25%). Cardiac or transcardiac embolic stroke occurred in 12% of the series and systemic diseases in 14%. There was a favorable outcome in 70% of patients having stroke due to nonprogressive arterial disease and stroke due to unidentified mechanisms. In contrast, only 26% of patients with embolic stroke, systemic disease, or moyamoya had a favorable outcome. Recurrences were more frequent and severe in this latter group. It is concluded that it is important to determine the mechanism of childhood stroke, because it strongly influences outcome, the recurrence risk, and treatment choice. (J Child Neurol 2000;15:290-294).

Transient Cerebral Arteriopathy: A Disorder Recognized by Serial Angiograms in Children With Stroke

Repeated clinical evaluation and cerebral arteriography during the evolution of ischemic strokes of idiopathic origin allowed us to characterize a transient cerebral arteriopathy. We retrospectively studied the clinical characteristics, course, and neuroimaging features of this disorder in nine children. Of 34 children with ischemic strokes seen consecutively between 1984 and 1995, 9 (26%) were diagnosed as having transient attack of the cerebral arterial wall, termed transient cerebral arteriopathy. All of these patients had previously been in good health. The mean age at the time of the first stroke was 6 years (range, 29/12 years to 134/12 years). All children presented with acute hemiplegia. A recurrence of the stroke took place 3 months at the latest after the initial infarct in three children (mean clinical follow-up 27/12 years). Cerebral imaging in all the patients showed small subcortical infarcts located in basal ganglia or internal capsule. Arteriography revealed multifocal lesions of the arterial wall (focal stenosis or segmental narrowing), mostly located in the initial parts of basal arteries of the carotid system. Longitudinal arteriographic follow-up showed initial worsening of these arterial lesions (n = 5) for a maximum duration of 7 months followed by complete regression (n = 2), improvement (n = 5), or stabilization of the lesions (n = 2). Five patients had a complete clinical recovery. Further studies are necessary to confirm a presumed inflammatory cause of this arteriopathy. (J Child Neurol 1998; 13:27-32).

Extensive brain calcifications, leukodystrophy, and formation of parenchymal cysts A new progressive disorder due to diffuse cerebral microangiopathy

A new cerebral disorder, described in three unrelated children, has recognizable clinical, radiologic, and neuropathologic findings. The onset occurs from early infancy to adolescence with slowing of cognitive performance, rare convulsive seizures, and a mixture of extrapyramidal, cerebellar, and pyramidal signs. CT shows progressive calcifications in the basal and cerebellar gray nuclei and the central white matter. MRI reveals diffuse abnormal signals of the white matter on T,-weighted sequences. A special feature is the development of parenchymal cysts in the cerebellum and the supratentorial compartment, leading to compressive complications and surgical considerations. Neuropathologic examination of surgically removed pericystic samples reveals angiomatous-like rearrangements of the microvessels, together with degenerative secondary changes of other cellular elements. Both the anatomic findings and the course of the disease suggest a constitutional, diffuse cerebral microangiopathy resulting in microcystic, then macrocystic, parenchymal degeneration.

Organization of the mevalonate kinase ( MVK ) gene and identification of novel mutations causing mevalonic aciduria and hyperimmunoglobulinaemia D and periodic fever syndrome

Mevalonic aciduria (MA) and hyperimmunoglobulinaemia D and periodic fever syndrome (HIDS) are two autosomal recessive inherited disorders both caused by a deficient activity of the enzyme mevalonate kinase (MK) resulting from mutations in the encoding MVK gene. Thus far, disease-causing mutations only could be detected by analysis of MVK cDNA. We now describe the genomic organization of the human MVK gene. It is 22 kb long and contains 11 exons of 46 to 837 bp and 10 introns of 379 bp to 4.2 kb. Three intron-exon boundaries were confirmed from natural splice variants, indicating the occurrence of exon skipping. Sequence analysis of 27 HIDS and MA patients confirmed all previously reported genotypes based on cDNA analysis and identified six novel nucleotide substitutions resulting in missense or nonsense mutations, providing new insights in the genotype/phenotype relation between HIDS and MA.

Cerebral Proliferative Angiopathy Clinical and Angiographic Description of an Entity Different From Cerebral AVMs

Background and Purpose— The purpose of this article is to describe “cerebral proliferative angiopathy” (CPA) as a clinical entity, which may be regarded as separate from “classical” brain AVMs in angioarchitecture, natural history, clinical presentation, and, therefore, treatment and which can be discerned from other cerebral AVMs by characteristic imaging features. Methods— In a prospectively entered databank encompassing 1434 patients with brain AVMs, a subgroup of 49 patients harboring specific angiographic characteristics were identified. Their charts and imaging films were retrospectively reviewed. Results— We found a preponderance of CPA in young (mean age: 22) females (67%). Clinical symptoms were seizures, disabling headaches, and stroke-like symptoms; hemorrhagic presentations were exceptional. On cross-sectional imaging, CPA demonstrated as a diffuse network of densely enhancing vascular spaces with intermingled normal brain parenchyma. The discrepancy between the large size of the nidus and the small shunting volume, the absence of flow-related aneurysms, the presence of diffuse angiogenesis (eg, transdural supply, progressive arterial occlusion), and the small calibre of a multitude of feeding arteries and draining veins were the angiographic hallmarks of this disease. Conclusion— The diffuse angiogenetic activity is presumably related to reduced perinidal perfusion and subsequent chronic cortical ischemia. Natural history demonstrates a low risk of hemorrhage. CPA may be regarded as a separate clinical entity different to “classical” cerebral AVMs, because normal brain is interspersed with the abnormal vascular channels increasing the risk of neurological deficit in aggressive treatments, which in the light of the natural history does not seem to be indicated.

New insights (and new interrogations) in perinatal arterial ischemic stroke

With an incidence of 1/2800 to 1/5000 live-births, perinatal arterial ischemic stroke is the most frequent form of cerebral infarction in children. About 40% of the children do not have specific symptoms in the neonatal period, and are only recognized later with the emergence of motor impairment, developmental delay, specific cognitive deficiency or seizures. In the remaining 60%, children present with early symptoms, mostly recurrent focal seizures in the first 3 days of life. The diagnosis is easily confirmed by cranial ultrasounds and MRI. Early MRI has both a key role in the diagnosis, dating the injury, but also an important prognostic value to predict the motor outcome of the child. Indeed, although the infarct does not recur, the majority of children show subsequent sequels: cerebral palsy, epilepsy, cognitive or behavioural problems. Finding predictors of outcome regarding these latter concerns (and the way to prevent or alleviate them) is of major interest. The main etiological hypothesis for perinatal AIS is a cerebral embolus, originating from the placenta through the foramen ovale. Most of the established risk factors are indeed either determinants or biomarkers of vasculo-placental pathology. Injury to the cervico-cerebral arteries, giving rise to thrombus/embolus during the birthing process is also suggested. Both placento-embolic and traumatic theories are supported by a few, but well-analysed pathological or arteriographic reports. Nevertheless, their relative frequency, the implication of other mechanisms, and their repercussions to evidence-based preventive strategies remain to be determined. Moreover, the mechanism of stroke in the different groups of newborns with stroke (term vs. preterm; symptomatic neonates vs. those with a delayed presentation) is likely to be different, and there is a need for future studies to assess all populations as different entities. Neonatal supportive care remains important for all infants while there is no evidence for preventive anticoagulant use at present. In an effort to reduce neurological dysfunction, and in adjunction with ongoing physical therapy and pharmacological treatment, new rehabilitative interventions, such as constraint-induced movement therapy and mirror therapy, are increasingly being used.

Ischaemic stroke from dissection of the craniocervical arteries in childhood: report of 12 patients.

Dissection of craniocervical arteries is the most common non-atherosclerotic cause of stroke in young adults. During childhood, it is described primarily as isolated reports. Among 59 patients with arterial ischaemic stroke seen consecutively in the same institution, 12 had a dissection of a cervical or cerebral artery. The diagnosis was established through imaging features. The dissection involved the cervical arteries in five patients and intracranial arteries in seven. A cervical or facial trauma preceded the onset of cerebral ischaemic symptoms in four patients with extracranial dissection by a few minutes to 10 days. For another six patients, the stroke occurred during physical exertion. The neurological deficit was preceded or associated with an intense headache or neck pain in nine patients. Initial treatment consisted of anticoagulation therapy in two patients with extracranial dissection, and aspirin in nine. There was only one recurrence of stroke after a mean follow-up of 3 years and 6 months. Four patients had persistent disabling neurological deficit. Dissection of cervical or cerebral arteries appears to be a common cause of stroke in childhood.

High dose methylprednisolone in severe acute transverse myelopathy

No effective treatment has been shown for patients with acute transverse myelopathy. In an open study five children with severe acute transverse myelopathy were treated with intravenous methylprednisolone and compared with a historical group of 10 patients. The results show that in the methylprednisolone treatment group compared with the historical group of 10 patients: the median time to walk independently was significantly reduced (23 v 97 days); the proportion of patients with a full recovery within 12 months was significantly higher (80 v 10%); all patients had complete motor recovery within one year in contrast with only two of 10 patients in the historical group; and serious adverse effects did not occur. This pilot study suggests that high dose methylprednisolone is effective in the treatment of acute transverse myelopathy.