Age-related changes in lateral ventricle morphology in craniosynostotic rabbits using magnetic resonance imaging

Structural brain differences in school-age children with and without single-suture craniosynostosis

OBJECTIVE Single-suture craniosynostosis (SSC), the premature fusion of a cranial suture, is characterized by dysmorphology of the craniofacial skeleton. Evidence to suggest that children with SSC are at an elevated risk of mild to moderate developmental delays and neurocognitive deficits is mounting, but the associations among premature suture fusion, neuroanatomy, and neurocognition are unexplained. The goals of this study were to determine 1) whether differences in the brain are present in young children with the 2 most common forms of SSC (sagittal and metopic) several years following surgical correction, and 2) whether the pattern of differences varies by affected suture (sagittal or metopic). Examination of differences in the brains of children with SSC several years after surgery may illuminate the growth trajectory of the brain after the potential constraint of the dysmorphic cranium has been relieved. METHODS The authors compared quantitative measures of the brain acquired from MR images obtained from children with sagittal or metopic craniosynostosis (n = 36) at 7 years of age to those obtained from a group of unaffected controls (n = 27) at the same age. The authors measured the volumes of the whole brain, cerebral cortex, cerebral white matter, cerebral cortex by lobe, and ventricles. Additionally, they measured the midsagittal area of the corpus callosum and its segments and of the cerebellar vermis and its component lobules. Measurements obtained from children with SSC and controls were compared using linear regression models. RESULTS No volume measures of the cerebrum or of the whole brain differed significantly between patients with SSC and controls (p > 0.05). However, ventricle volume was significantly increased in patients with SSC (p = 0.001), particularly in those with sagittal craniosynostosis (p < 0.001). In contrast, the area of the corpus callosum was significantly reduced in patients with metopic synostosis (p = 0.04), particularly in the posterior segments (p = 0.004). Similarly, the area of lobules VI-VII of the cerebellar vermis was reduced in patients with SSC (p = 0.03), with those with metopic craniosynostosis showing the greatest reduction (p = 0.01). CONCLUSIONS The lack of differences in overall brain size or regional differences in the size of the lobes of the cerebrum in children with metopic and sagittal synostosis suggests that the elevated risk of neurodevelopmental deficits is not likely to be associated with differences in the cerebral cortex. Instead, this study showed localized differences between sagittal and metopic craniosynostosis cases as compared with controls in the ventricles and in the midsagittal structures of the corpus callosum and the cerebellum. It remains to be tested whether these structural differences are associated with the increased risk for developmental delay and neurocognitive deficits in children with SSC.

Dietary cholesterol increases ventricular volume and narrows cerebrovascular diameter in a rabbit model of Alzheimer's disease

Using structural magnetic resonance imaging in a clinical scanner at 3.0T, we describe results showing that following 12weeks on a diet of 2% cholesterol, rabbits experience a significant increase in the volume of the third ventricle compared to rabbits on a diet of 0% cholesterol. Using time-of-flight magnetic resonance angiography, we find cholesterol-fed rabbits also experience a decrease in the diameter of a number of cerebral blood vessels including the basilar, posterior communicating, and internal carotid arteries. Taken together, these data confirm that, despite the inability of dietary cholesterol to cross the blood-brain barrier, it does significantly enlarge ventricular volume and decrease cerebrovascular diameter in the rabbit - effects that are also seen in patients with Alzheimer's disease.

Cholesterol increases ventricular volume in a rabbit model of Alzheimer's disease

One of the hallmarks of Alzheimer's disease is a significant increase in ventricular volume. To date we and others have shown that a cholesterol-fed rabbit model of Alzheimer's disease displays as many as fourteen different pathological markers of Alzheimer's disease including amyloid-β accumulation, thioflavin-S staining, blood brain barrier breach, microglia activation, cerebrovasculature changes, and alterations in learning and memory. Using structural magnetic resonance imaging at 3T, we now report that cholesterol-fed rabbits also show a significant increase in ventricular volume following 10 weeks on a diet of 2% cholesterol. The increase in volume is attributable in large part to increases in the size of the third ventricle. These changes are accompanied by significant increases in the number of amyloid-β immuno-positive cells in the cortex and hippocampus. Increases in the number of amyloid-β neurons in the cortex also occurred with the addition of 0.24 ppm copper to the drinking water. Together with a list of other pathological markers, the current results add further validity to the value of the cholesterol-fed rabbit as a non-transgenic animal model of Alzheimer's disease.

Age-related peridural hyperemia in craniosynostotic rabbits

OBJECTIVE

Craniosynostosis is the premature fusion of the calvarial sutures and is associated with aesthetic impairment and secondary damage to brain growth. Associated neurological injuries can result from increased intracranial pressure (ICP) and abnormal cerebral blood flow (CBF). Arterial spin-labeling (ASL) MRI was used to assess regional CBF in developing rabbits with early-onset coronal suture synostosis (EOCS) and age-matched wild-type controls (WT).

METHODS

Rabbits were subjected to ASL MRI at or near 10, 25, or 42 days of age. Differences in regional CBF were assessed using one-way ANOVA.

CONCLUSION

CBF was similar in WT and EOCS rabbits with the exception of the peridural surfaces in EOCS rabbits at 25 days of age. A twofold increase in peridural CBF at 25 days of age coincides with a transient increase in ICP. By 42 days of age, CBF in peridural surfaces had decreased.

Anti-TGF-??2 Antibody Therapy Inhibits Postoperative Resynostosis in Craniosynostotic Rabbits

BACKGROUND

Postoperative resynostosis is a common clinical finding. It has been suggested that an overexpression of transforming growth factor (TGF)-beta2 may be related to craniosynostosis and may contribute to postoperative resynostosis. Interference with TGF-beta2 function with the use of neutralizing antibodies may inhibit resynostosis. The present study was designed to test this hypothesis.

METHODS

New Zealand White rabbits with bilateral coronal suture synostosis were used as suturectomy controls (group 1, n = 9) or given suturectomy with nonspecific, control immunoglobulin G antibody (group 2, n = 9) or suturectomy with anti-TGF-beta2 antibody (group 3, n = 11). At 10 days of age, a 3 x 15-mm coronal suturectomy was performed. The sites in groups 2 and 3 were immediately filled with 0.1 cc of a slowly resorbing collagen gel mixed with either immunoglobulin G (100 mug per suture) or anti-TGF-beta2 (100 mug per suture). Three-dimensional computed tomography scan reconstructions of the defects were obtained at 10, 25, 42, and 84 days of age, and the sutures were harvested for histomorphometric analysis.

RESULTS

Computed tomography scan data revealed that the suturectomy sites treated with anti-TGF-beta2 showed significantly (p < 0.05) greater areas through 84 days of age compared with controls. Histomorphometry also showed that suturectomy sites treated with anti-TGF-beta2 had patent suturectomy sites and more fibrous tissue in the defects compared with sites in control rabbits and had significantly (p < 0.001) less new bone area (by approximately 215 percent) in the suturectomy site.

CONCLUSIONS

These data support the initial hypothesis that interference with TGF-beta2 function inhibited postoperative resynostosis in this rabbit model. They also suggest that this biologically based therapy may be a potential surgical adjunct to retard postoperative resynostosis in infants with craniosynostosis.

Postoperative Anti-Tgf-β2 Antibody Therapy Improves Intracranial Volume and Craniofacial Growth in Craniosynostotic Rabbits

Postoperative resynostosis and secondary craniofacial growth abnormalities are common sequelae after craniofacial surgery. It has been suggested that an overexpression of transforming growth factor-beta2 (Tgf-beta2) may be related to craniosynostosis and contribute to postoperative resynostosis. Interference with Tgf-beta2 function using neutralizing antibodies may inhibit resynostosis and improve postoperative craniofacial growth; the present study was designed to test this hypothesis. Twenty-nine New Zealand white rabbits with bilateral coronal suture synostosis were used: 1) suturectomy controls (n=9); 2) suturectomy with nonspecific, control IgG antibody (n=9); and 3) suturectomy with anti-Tgf-beta2 antibody (n=11). At 10 days of age, a 3 mm x 15-mm coronal suturectomy was performed. The sites in groups 2 and 3 were immediately filled with 0.1 cc of a slow resorbing collagen gel mixed with either IgG (100 microg/suture) or anti-Tgf-beta2 (100 microg/suture). Three-dimensional computed tomography scan reconstructions of the skulls and cephalographs were obtained at 10, 25, 42, and 84 days of age. Computed tomography scan data revealed patent suturectomy sites and significantly (P<0.05) greater intracranial volumes by 84 days of age in rabbits treated with anti-Tgf-beta2 compared with controls. Cephalometric analysis revealed significant (P<0.05) differences in craniofacial, cranial vault, and cranial base growth by 84 days of age in rabbits treated with anti-Tgf-beta2 compared with controls. These data support the initial hypothesis that interference with Tgf-beta2 function inhibited postoperative resynostosis and improved cranial vault growth in this rabbit model. Thus, this biologically based therapy may be a potential surgical adjunct in the treatment of infants with craniosynostosis.

Diagnostic imaging in the management of craniosynostoses

Craniosynostoses are the most frequent craniofacial malformations. However, with a prevalence of 3-6 cases per 10,000 live births they are amongst the rarely seen diseases and their definite diagnosis thus poses a challenge to the physician. When an abnormal calvarial configuration is detected, a radiological evaluation is necessary to characterize the deformity and to guide the corrective surgical procedure. The demand for clear diagnostic criteria is justified by the severity of the disease and the possible consequences of delayed diagnosis. In addition to the clinical signs (deformation of the head), conventional skull X-rays show typical radiological alterations and are used for basic diagnostics. Diagnostic tests that may be performed to confirm the diagnosis and assess the extent of the problem, include computed tomography (CT), 3D-CT, magnetic resonance imaging (MRI) scans, and ultrasonography. In the present review we will describe the most important clinical and radiological characteristics of craniosynostosis by means of clinical, radiological and operative situs examples.

Testing causal mechanisms of nonsyndromic craniosynostosis using path analysis of cranial contents in rabbits with uncorrected craniosynostosis

OBJECTIVE

Various causal mechanisms of familial nonsyndromic craniosynostosis have been presented. One hypothesis suggests that overproduction of bone at the suture is the primary origin of craniosynostosis, which affects brain and cranial growth secondarily through altered intracranial pressure (Primary Suture Fusion Model). Other hypotheses suggest that decreased cranial base growth or abnormal brain growth are the primary cause of craniosynostosis (Cranial Base, Brain Parenchyma Models, respectively). This study was designed to investigate which model best describes neurocranial changes associated with craniosynostosis in a rabbit model through multivariate path analysis.

DESIGN

Serial magnetic resonance imaging scans and intracranial pressure measurements were obtained at 10, 25, and 42 days of age from 18 rabbits: six controls, six with delayed-onset synostosis, and six with early-onset synostosis. Five variables were collected from each rabbit: calvarial thickness at the affected suture, cranial base length, brain volume, cerebrospinal fluid volume, and intracranial pressure. This data set was used to test causal pathway relationships generated by the proposed models. Goodness of fit was measured by experimental group for each model.

RESULTS

Primary Suture Fusion Model best explained the variables in both delayed-onset and early-onset synostotic rabbits (Goodness of fit = 93%, 97%, respectively). Cranial Base Model (Goodness of fit = 94%) best explained the data in control rabbits.

CONCLUSION

Results suggest that the primary site of craniosynostosis in craniosynostotic rabbits is most likely the synostosed suture. Other cranial vault anomalies are most likely secondary compensatory changes. Results of the present study may provide insight regarding the causal pathway of craniosynostosis.

Craniosacral therapy: the effects of cranial manipulation on intracranial pressure and cranial bone movement

STUDY DESIGN

Quasi-experimental design.

OBJECTIVES

To determine if physical manipulation of the cranial vault sutures will result in changes of the intracranial pressure (ICP) along with movement at the coronal suture.

BACKGROUND

Craniosacral therapy is used to treat conditions ranging from headache pain to developmental disabilities. However, the biological premise for this technique has been theorized but not substantiated in the literature.

METHODS

Thirteen adult New Zealand white rabbits (oryctolagus cuniculus) were anesthetized and microplates were attached on either side of the coronal suture. Epidural ICP measurements were made using a NeuroMonitor transducer. Distractive loads of 5, 10, 15, and 20 g (simulating a craniosacral frontal lift technique) were applied sequentially across the coronal suture. Baseline and distraction radiographs and ICP were obtained. One animal underwent additional distractive loads between 100 and 10,000 g. Plate separation was measured using a digital caliper from the radiographs. Two-way analysis of variance was used to assess significant differences in ICP and suture movement.

RESULTS

No significant differences were noted between baseline and distraction suture separation (F = 0.045; P>.05) and between baseline and distraction ICP (F = 0.279; P>.05) at any load. In the single animal that underwent additional distractive forces, movement across the coronal suture was not seen until the 500-g force, which produced 0.30 mm of separation but no corresponding ICP changes.

CONCLUSION

Low loads of force, similar to those used clinically when performing a craniosacral frontal lift technique, resulted in no significant changes in coronal suture movement or ICP in rabbits. These results suggest that a different biological basis for craniosacral therapy should be explored.

Intracranial Volume Changes in Craniosynostotic Rabbits: Effects of Age and Surgical Correction

BACKGROUND

The premature fusion of one or more cranial sutures, termed craniosynostosis, alters normal brain growth patterns and results in compensatory changes in the cranial vault. The authors previously reported that bilateral coronal suture fusion resulted in a reduction in intracranial volume in a rabbit model of nonsyndromic, familial coronal suture synostosis.

METHODS

The current follow-up study involved collecting cross-sectional three-dimensional computed tomographic head scans from 142 rabbits (70 normal, 44 with uncorrected synostosis, and 28 synostosed rabbits with coronal suturectomy) at 0, 10, 25, 42, 84, and 126 days of age. Intracranial contents were reconstructed, and indirect intracranial volume was calculated.

RESULTS

Results revealed a significant (p < 0.05) postsynostotic reduction of intracranial volume (23 percent) by 25 days of age in rabbits with uncorrected craniosynostosis compared with normal controls, which continued through 84 days of age. Also, rabbits with surgically released synostosis, using a simple strip suturectomy, showed significantly (p < 0.05) greater intracranial volume at 25 days of age compared with unoperated synostosed rabbits. However, no changes in intracranial volume were noted between 42 and 84 days of age in rabbits with surgically released synostosis, at which point their intracranial volume was 30 percent less than that in normal control rabbits.

CONCLUSIONS

These data suggest that in rabbits with uncorrected craniosynostosis, compensatory changes in the neurocranium were not capable of compensating for the loss of sutures as growth sites. The results also showed that that surgical release of the synostosed suture improved intracranial volume in the short term (25 to 42 days) but failed to change it in the long term (42 to 84 days), possibly because of rapid resynostosis of the suturectomy site. This study suggests that surgical release of the suture fusion site alone may not be adequate to allow for normal intracranial volume growth in synostotic rabbits. For this reason, it may be efficacious to design and develop adjunct protein and gene therapies to prevent resynostosis and improve postoperative intracranial volume in craniosynostotic individuals.