Jayaratnam Jayamohan

Prevalence and complications of single gene and chromosomal disorders in craniosynostosis

OBJECTIVES: We describe the first cohort-based analysis of the impact of genetic disorders in craniosynostosis. We aimed to refine the understanding of prognoses and pathogenesis and to provide rational criteria for clinical genetic testing. METHODS: We undertook targeted molecular genetic and cytogenetic testing for 326 children who required surgery because of craniosynostosis, were born in 1993–2002, presented to a single craniofacial unit, and were monitored until the end of 2007. RESULTS: Eighty-four children (and 64 relatives) had pathologic genetic alterations (86% single-gene mutations and 14% chromosomal abnormalities). The FGFR3 P250R mutation was the single largest contributor (24%) to the genetic group. Genetic diagnoses accounted for 21% of all craniosynostosis cases and were associated with increased rates of many complications. Children with an initial clinical diagnosis of nonsyndromic craniosynostosis were more likely to have a causative mutation if the synostoses were unicoronal or bicoronal (10 of 48 cases) than if they were sagittal or metopic (0 of 55 cases; P = .0003). Repeat craniofacial surgery was required for 58% of children with single-gene mutations but only 17% of those with chromosomal abnormalities (P = .01). CONCLUSIONS: Clinical genetic assessment is critical for the treatment of children with craniosynostosis. Genetic testing of nonsyndromic cases (at least for FGFR3 P250R and FGFR2 exons IIIa/c) should be targeted to patients with coronal or multisuture synostoses. Single-gene disorders that disrupt physiologic signaling in the cranial sutures often require reoperation, whereas chromosomal abnormalities follow a more-indolent course, which suggests a different, secondary origin of the associated craniosynostosis.

Mechanics of the brain: perspectives, challenges, and opportunities

The human brain is the continuous subject of extensive investigation aimed at understanding its behavior and function. Despite a clear evidence that mechanical factors play an important role in regulating brain activity, current research efforts focus mainly on the biochemical or electrophysiological activity of the brain. Here, we show that classical mechanical concepts including deformations, stretch, strain, strain rate, pressure, and stress play a crucial role in modulating both brain form and brain function. This opinion piece synthesizes expertise in applied mathematics, solid and fluid mechanics, biomechanics, experimentation, material sciences, neuropathology, and neurosurgery to address today’s open questions at the forefront of neuromechanics. We critically review the current literature and discuss challenges related to neurodevelopment, cerebral edema, lissencephaly, polymicrogyria, hydrocephaly, craniectomy, spinal cord injury, tumor growth, traumatic brain injury, and shaken baby syndrome. The multi-disciplinary analysis of these various phenomena and pathologies presents new opportunities and suggests that mechanical modeling is a central tool to bridge the scales by synthesizing information from the molecular via the cellular and tissue all the way to the organ level.

The preoperative incidence of raised intracranial pressure in nonsyndromic sagittal craniosynostosis is underestimated in the literature

OBJECT The presence of raised intracranial pressure (ICP) in untreated nonsyndromic, isolated sagittal craniosynostosis (SC) is an important functional indication for surgery. METHODS A retrospective review was performed of all 284 patients presenting with SC to the Oxford Craniofacial Unit between 1995 and 2010. RESULTS Intraparenchymal ICP monitoring was performed in 39 children following a standard unit protocol. Monitoring of ICP was offered for all patients in whom nonoperative management was considered on the basis of minimal deformity or in cases in which parents were reluctant to agree to corrective surgery. These patients presented at an older age than the rest of the cohort (mean age 56 months), with marked scaphocephaly (16/39, 41%), mild scaphocephaly (11, 28%), or no scaphocephalic deformity (12, 31%). Raised ICP was found in 17 (44%) patients, with no significant difference in its incidence among the 3 different deformity types. Raised ICP was not predicted by the presence of symptoms of ICP or developmental delay or by ophthalmological or radiological findings. CONCLUSIONS The incidence of raised ICP in SC reported here is greater than that previously published in the literature. The lack of a reliable noninvasive method to identify individuals with elevated ICP in SC mandates consideration of intraparenchymal ICP monitoring in all patients for whom nonoperative management is contemplated.

REOPERATION FOR INTRACRANIAL HYPERTENSION IN TWIST1 CONFIRMED SAETHRE-CHOTZEN SYNDROME: A 15 YEAR REVIEW

Background: Saethre-Chotzen syndrome is a syndromic craniosynostosis defined by a genetic mutation affecting the TWIST1 gene on chromosome 7p21. It is typically associated with unicoronal or bicoronal synostosis, eyelid ptosis, dysmorphic external ears, and other variable facial and limb abnormalities. Surgical management of the craniosynostosis addresses the calvarial deformity and may relieve or reduce the risk of intracranial hypertension. The aim of this study was to assess surgical intervention, with particular consideration of the reoperation rate for intracranial hypertension, in Saethre-Chotzen syndrome patients. Methods: A retrospective case note analysis was performed on all patients with a confirmed TWIST1 gene abnormality who attended the Oxford Craniofacial Unit over a 15-year period. Each patients mutation and clinical features were recorded. Surgical intervention and sequelae were examined in greater detail. Results: Thirty-four patients with genetically confirmed Saethre-Chotzen syndrome were identified. All had craniosynostosis (bicoronal, 76 percent; unicoronal, 18 percent; bicoronal and sagittal, 6 percent), and the majority had eyelid ptosis, low frontal hairline, and external ear anomalies. Thirty-one patients had received surgical intervention. Nine of 26 patients (35 percent) with at least 12 months of follow-up after primary intervention and eight of 19 patients (42 percent) with at least 5 years of follow-up developed intracranial hypertension necessitating secondary calvarial surgery. Conclusions: Despite standard surgical intervention, patients with Saethre-Chotzen syndrome have a high rate (35 to 42 percent) of recurrent intracranial hypertension necessitating further surgical expansion. All patients with either bicoronal synostosis or unicoronal synostosis with syndromic features should be screened for TWIST1 mutations, as this confers a greater risk than nonsyndromic synostosis of the same sutures. Regular follow-up throughout the childhood years is essential.

The incidence of raised intracranial pressure in nonsyndromic sagittal craniosynostosis following primary surgery.

OBJECT Raised intracranial pressure (ICP) is recognized to occur in patients with nonsyndromic isolated sagittal craniosynostosis (SC) prior to surgery. However, the incidence of raised ICP following primary surgery is rarely reported and there appears to be a widely held assumption that corrective surgery for SC prevents the later development of intracranial hypertension. This study reports the incidence of postoperative raised ICP in a large cohort of patients with SC treated by 1 of 2 surgical procedures in a single craniofacial unit. METHODS A retrospective review was performed of all patients with SC who underwent either a modified strip craniectomy (MSC) or calvarial remodeling (CR) procedure under the care of the Oxford Craniofacial Unit between 1995 and 2010 and who were followed up for more than 2 years. The influence of patient age at surgery, year of surgery, sex, procedure type, and the presence of raised ICP preoperatively were analyzed. RESULTS Two hundred seventeen children had primary surgery for SC and were followed up for a mean of 86 months. The overall rate of raised ICP following surgery was 6.9%, occurring at a mean of 51 months after the primary surgical procedure. Raised ICP was significantly more common in those patients treated by MSC (13 of 89 patients, 14.6%) than CR (2 of 128 patients, 1.6%). Also, raised ICP was more common in patients under 1 year of age, the majority of whom were treated by MCS. No other factor was found to have a significant effect. CONCLUSIONS Postoperative raised ICP was found in more than 1 in 20 children treated for nonsyndromic SC in this series. It was significantly influenced by the primary surgical procedure and age at primary surgery. Careful long-term follow-up is essential if children who develop raised ICP following surgery are not to be overlooked.

Implications of a vertex bulge following modified strip craniectomy for sagittal synostosis.

Background: Modified strip craniectomy is a common treatment for early isolated sagittal synostosis. The authors assessed the significance of the development of a progressive vertex bulge following strip craniectomy as a predictor of raised intracranial pressure or multiple suture synostosis. Methods: All cases of sagittal synostosis treated by modified strip craniectomy (removal of the sagittal suture with lateral barrel staving) at the authors’ institution were reviewed. Eighty-nine patients with isolated sagittal synostosis were treated by modified strip craniectomy, usually before 6 months of age, between 1995 and 2005. Seven patients were noted to have developed a progressive vertex bulge. The vertex bulge was noted an average of 8 months postoperatively (range, 2 to 25 months). The clinical records of these seven patients were evaluated with regard to their clinical course, radiologic investigations, genetics testing, intracranial pressure monitoring, and the need for further surgery. Results: Computed tomographic scanning demonstrated new synostosis involving other calvarial sutures in five patients. Five patients underwent intracranial pressure monitoring, and this was elevated in four patients. One patient required a ventriculoperitoneal shunt for hydrocephalus. All patients underwent genetic screening, and two were found to have fibroblast growth factor receptor (FGFR) mutations (one FGFR2 and one FGFR3 mutation). All patients required reoperation (calvarial remodeling) for either raised intracranial pressure, deteriorating head shape, or both. Conclusions: A progressive vertex bulge after modified strip craniectomy is a sign of possible raised intracranial pressure, the development of progressive multiple suture synostosis, or both. It is an indication for genetic testing for FGFR mutations.

Posterior calvarial distraction in craniosynostosis - an evolving technique.

BACKGROUND Posterior advancement of the occiput is an established surgical option for the treatment of raised intracranial pressure (ICP) secondary to craniocerebral disproportion in syndromic craniosynostoses. Distraction osteogenesis has gained popularity in a variety of craniofacial procedures to achieve greater advancement in the anterior craniofacial skeleton, but has only relatively recently been used in the posterior calvarium. We report the Oxford Craniofacial Units experience of using distraction techniques to expand the occiput. METHODS We preformed a retrospective casenote review of all patients with syndromic craniosynostoses who underwent posterior distraction at our centre from 2007 to 2010, as identified by the Oxford Craniofacial Database. RESULTS Ten syndromic patients underwent posterior distraction (mean age of 18.1 months). Successful calvarial expansion (mean advancement of 19.7 mm) was achieved in all patients clinically and radiologically. There were 6 minor and 1 major complications. CONCLUSIONS Posterior distraction was successfully performed in 10 patients including babies as young as 3 months of age. It achieved a reduction in turricephaly, an improvement in the cephalic index, and a resolution of raised ICP. We have customised our surgical technique to address individual patient needs. The use of distraction techniques in the occiput appears to increase the reliability of expansion in this region.

Raised intracranial pressure is frequent in untreated nonsyndromic unicoronal synostosis and does not correlate with severity of phenotypic features.

Background: In a small number of children with unicoronal synostosis, the phenotype is mild and the aesthetic benefit of surgical correction is potentially outweighed by surgical risk. Raised intracranial pressure, however, would necessitate intervention. The authors documented the incidence of raised intracranial pressure in children with mild features and/or parental reluctance to proceed directly to surgery. Methods: A retrospective review of all children with (1) a clinical diagnosis of nonsyndromic unicoronal synostosis; (2) unicoronal synostosis confirmed on computed tomographic scanning; (3) negative family history for unicoronal synostosis; and (4) negative genetic screening (including P250R encoded by FGFR3, exons IIIa and IIIc in FGFR2 and TWIST1) was completed. Results: Of the 80 children studied, seven (9 percent) underwent formal intracranial pressure monitoring because of a combination of mild clinical features (n = 4) and/or parental reluctance to proceed with surgery (n = 3). Intracranial pressure monitoring was reported as high in three (42 percent), borderline in two (29 percent), and normal in two patients (29 percent). The findings did not correlate with the degree of clinical deformation or age at presentation. There was little correlation with clinical and radiographic features of raised intracranial pressure in this genetically screened nonsyndromic group. Conclusions: High or borderline raised intracranial pressure was present in five of seven cases. The risk did not correlate with degree of deformity or age at presentation. Formal intracranial pressure monitoring should be considered in all children with unicoronal synostosis not proceeding directly to surgical intervention, in combination with routine long-term follow-up and repeated intracranial pressure monitoring where indicated. CLINICAL QUESTION/LEVEL OF EVIDENCE: Risk, V.

Lessons learned in posterior cranial vault distraction.

Introduction Posterior distraction (PD) is rapidly emerging as an important technique to increase the intracranial volume and correct calvarial morphology in patients with severe brachycephaly or turribrachycephaly. Methods A retrospective review was performed of all 31 patients who underwent PD at the Oxford Craniofacial Unit between 2007 and 2012. Results Twenty-three patients (74.2%) underwent PD as a primary procedure at a median age of 8 months. Eight patients (25.8%) had PD as a secondary transcranial procedure at a median age of 48 months. Full distraction to 20 mm was achieved in 28 patients (90.3%). Of these, all but 1 demonstrated a significant improvement in morphology, with a resolution of the symptoms and signs of raised intracranial pressure in all proven to have it preoperatively. Unanticipated events occurred in 61.3% of patients, with 19.4% undergoing one or more unplanned procedures. Wound infection (29.0%) and tissue necrosis (22.6%) were the commonest. Cerebrospinal fluid leaks were rarer (6.5%) but prevented full distraction. Nine patients (29.0%) had a consolidation period of less than 30 days without experiencing relapse. In 11 patients who had a later fronto-orbital advancement and remodeling, wound closure was tight, resulting in dehiscence in 3 cases (27.3%). Conclusions Posterior distraction is an effective procedure in the management of severe brachycephaly or turribrachycephaly but has associated risks. Our protocol has evolved with experience to favor a reduced latency period and consolidation phase and the use of 2 distractor devices.

Long-term morphological outcomes in nonsyndromic sagittal craniosynostosis: a comparison of 2 techniques.

AbstractCorrection of scaphocephaly is one of the principle goals of surgery in sagittal craniosynostosis. Reported relapse in head shape after surgery and continued head growth into late adolescence underscores the need for long-term outcomes to be considered when comparing between different surgical approaches in this condition; yet there are relatively few reports of results to 5 years and beyond in the literature. Therefore, a retrospective review was performed of the anthropometric data of 224 patients with sagittal craniosynostosis who underwent primary surgery between 1994 and 2012. During this period, patients underwent either a modified strip craniectomy (MSC) or calvarial remodeling (CR) procedure. Sixty-two patients were treated by MSC and followed up for a mean of 44 months. One hundred sixty-two patients had CR, with follow-up for a mean of 45 months. Overall, 90 patients were seen up to 5 years, and 47 patients to 9 years or more after surgery. The cephalic index (CI) of MSC-treated patients improved from a mean of 67.0 to 72.7, with 31% achieving a CI greater than 75 at one year. Calvarial remodeling was significantly more effective at correcting the scaphocephalic deformity. Patients treated with CR improved from a mean CI of 66.7 to 76.1. Sixty-two percent of the patients achieved a CI greater than 75. In both groups, outcomes were stable throughout follow-up with no significant relapse up to 14 years after surgery.