F. Di Rocco

A mathematical model for mechanotransduction at the early steps of suture formation.

Growth and patterning of craniofacial sutures is subjected to the effects of mechanical stress. Mechanotransduction processes occurring at the margins of the sutures are not precisely understood. Here, we propose a simple theoretical model based on the orientation of collagen fibres within the suture in response to local stress. We demonstrate that fibre alignment generates an instability leading to the emergence of interdigitations. We confirm the appearance of this instability both analytically and numerically. To support our model, we use histology and synchrotron X-ray microtomography and reveal the fine structure of fibres within the sutural mesenchyme and their insertion into the bone. Furthermore, using a mouse model with impaired mechanotransduction, we show that the architecture of sutures is disturbed when forces are not interpreted properly. Finally, by studying the structure of sutures in the mouse, the rat, an actinopterygian (Polypterus bichir) and a placoderm (Compagopiscis croucheri), we show that bone deposition patterns during dermal bone growth are conserved within jawed vertebrates. In total, these results support the role of mechanical constraints in the growth and patterning of craniofacial sutures, a process that was probably effective at the emergence of gnathostomes, and provide new directions for the understanding of normal and pathological suture fusion.

Neonatal ruptured intracranial aneurysms: case report and literature review

IntroductionIntracranial aneurysms are exceptional in neonatal patients: There are only 16 cases previously reported. We describe the first case of neonatal posterior inferior cerebellar artery (PICA) aneurysm and review the literature.Case reportA 7-day-old girl presented with irritability, anorexia, fever and abnormally enlarging head circumference. Computed tomography (CT) and magnetic resonance (MR) imaging demonstrated intraventricular haemorrhage, secondary hydrocephalus and a pontine cistern haematoma. A PICA aneurysm was suspected on the CT angiogram (CTA) and the diagnosis was confirmed by conventional cerebral angiography. She was successfully treated by surgical clipping of the parent vessel and excision of the aneurysm. Postoperatively, she experienced transient swallowing difficulties and required a ventriculo-peritoneal shunt for hydrocephalus. Histopathological evaluation demonstrated a calcified arterial wall with thrombosis, signs of prior haemorrhage and the absence of the internal elastic lamina.ConclusionNeonatal intracranial aneurysms are rare. Clinical presentation of subarachnoid haemorrhage in this age group is often non-specific. First-line investigation should start with transfontanelle cranial ultrasound, followed by MR angiography then CTA if necessary. Posterior circulation aneurysms and large or giant aneurysms are more frequent in neonates and children than in adults. Early diagnosis and treatment are important for improved outcome. Surgery is better tolerated than in adults.

Prospective Hemorrhage Rates of Cerebral Cavernous Malformations in Children and Adolescents Based on MRI Appearance

BACKGROUND AND PURPOSE: Current classifications of cerebral cavernous malformations focus solely on morphologic aspects. Our aim was to provide a morphologic classification that reflects hemorrhage rates. MATERIALS AND METHODS: We retrospectively categorized 355 cavernous malformations of 70 children and adolescents according to their morphologic appearance on MR imaging and calculated prospective hemorrhage rates on the basis of survival functions for 255 lesions in 25 patients with a radiologic observation period of >180 days. RESULTS: Overall, there were 199 MR imaging examinations with 1558 distinct cavernous malformation observations during a cumulative observation period of 1094.2 lesion-years. The mean hemorrhage rate of all 355 cavernous malformations was 4.5% per lesion-year. According to Kaplan-Meier survival models, Zabramski type I and II cavernous malformations had a significantly higher hemorrhage rate than type III and IV lesions. The presence of acute or subacute blood-degradation products was the strongest indicator for an increased hemorrhage risk (P = .036, Cox regression): The mean annual hemorrhage rate and mean hemorrhage-free interval for cavernous malformations with and without signs of acute or subacute blood degradation products were 23.4% and 22.6 months and 3.4% and 27.9 months, respectively. Dot-sized cavernous malformations, visible in T2* and not or barely visible in T1WI and T2WI sequences, had a mean annual hemorrhage rate of 1.3% and a mean hemorrhage-free interval of 37.8 months. CONCLUSIONS: It is possible to predict hemorrhage rates based on the Zabramski classification. Our findings imply a tripartite classification distinguishing lesions with and without acute or subacute blood degradation products and dot-sized cavernous malformations.

Épilepsie et lésions focales chez l’enfant. Traitement chirurgical

Epilepsy surgery has gained a large role in the treatment of intractable seizures in the last few decades because of the development of operative techniques and better identification of the cerebral anomalies using electrophysiological recordings and neuroimaging. A series of 419 children, aged from five months to 15 years, with epilepsy (medically refractory in 85.5% of them) associated with focal cortical lesions, who underwent surgery between 1986 and 2006 was analyzed to identify the factors that correlated with outcome. Mean follow-up was 5.2 years. According to Engels classification; 75.8% of the children were seizure-free. When the lesion was well defined, correlations between clinical data, radiological features and electrophysiological features, suggesting a zone of seizure onset around (or even in) the lesion, was the best guarantee of achieving good seizure control by lesionectomy. Nevertheless, seizure outcome was also determined by other factors: the duration of the epilepsy and the surgery. Persistence of seizures was found to be significantly associated with the preoperative duration of epilepsy, the completeness of the lesional resection and de novo brain damage induced by the surgical procedure itself. Early surgery must be considered in children because of the benefits of seizure control on the developing brain and the risk of secondary epileptogenesis.

High-resolution imaging of craniofacial sutures: new tools for understanding the origins of craniosynostoses

Aim and scopeThe developmental genetics and the biomechanics of sutures are well-studied topics, while their microanatomy is still imperfectly known. Here, we aim to investigate the structure of skull vault sutures using a high-resolution imaging device.Material and methodsWe used synchrotron X-ray microtomography in order to obtain high-resolution images of skull vault sutures from an extant mammal (the mouse Mus musculus) and from an extinct fish (the placoderm Compagopiscis croucheri). We used segmentation and 3D reconstruction softwares in order to reveal the microanatomy of sutures in these species.ResultsThe high-resolution images allowed us to study the distribution of osteocytes, the organisation of vascular canals, the shapes of the suture borders, the insertion of Sharpeys fibres, the bone growth lines and the structure of the soft tissues surrounding the sutures.ConclusionSynchrotron imaging provides new perspectives for the study of the normal microanatomy of sutures. The submicronic resolution of the synchrotron scans gives access to the 3D organisation of structures that were previously only known in 2D, even in normal sutures. The description of anatomical entities such as vascular canals and Sharpeys fibres in abnormally fused sutures would be of interest in the understanding of craniosynostoses.

Crouzon syndrome and Bent bone dysplasia associated with mutations at the same Tyr‐381 residue in FGFR2 gene

To the Editor : We report the identification of novel p.Tyr381Asn (c.1141T>A) mutation in FGFR2 gene in a family affected by Crouzon syndrome (MIM:123500). This mutation is located at the same residue than the mutation (p.Tyr381Asp, c.1141T>G) recently described in the perinatal lethal Bent bone dysplasia (BBD) (1). Crouzon syndrome was suspected in the proband at the age of 3 years. Birth parameters were weight: 2940 g, length: 46 cm, and head circumference: 37 cm. At the age of 3 years, he presented with a scaphocephaly with bilateral exophthalmos, parrot-beaked nose and frontal bossing (Fig. 1). A pronounced nasal obstruction with septal deviation and a malocclusion was observed. A skull computed tomography (CT) examination

Passage de l’enfant à l’adulte et prise en charge de la spasticité

The authors report specific concerns on the transition to adulthood in cerebral palsy patients, with particular attention devoted to spasticity treatment follow-up.