Posterior vault "free-floating" bone flap: indications, technique, advantages, and drawbacks

Free-floating bone flap posterior cranial vault release in syndromic craniosynostosis

The aim of this study was to investigate the efficacy of non-detachable free-floating bone flap posterior cranial vault release (FFBF-PCVR) in syndromic craniosynostosis. A retrospective review was completed of subjects who underwent FFBF-PCVR at 4 time-points: within 3 months preoperatively, 7 days postoperatively, 3 months postoperatively and at the last follow-up postoperatively. Volumetric and craniometric data, the ratio of ventricular diameter, and the cerebellar tonsillar descent were measured after FFBF-PCVR by using computed tomographic and magnetic resonance imaging. A total of 19 patients underwent FFBF-PCVR. The mean age was 11.7 months (range 4-36 months). The mid cranial height, posterior cranial height, and anterior posterior diameter length significantly increased from preoperative to postoperative 7 days, from postoperative 7 days to postoperative3 months, and from postoperative 3 months to the last follow-up. There was a significant increase in pre- to 7 days postoperative intracranial volume (1195.21 ± 246.56 cm³, p < 0.001; respectively), 3 months postoperative intracranial volume (1228.03 ± 249.61 cm³, p < 0.001; respectively), and intracranial volume at last follow-up (1390.25 ± 219.99 cm³, p < 0.001; respectively). There was a significant increase in 7 days' postoperative to 3 months' postoperative intracranial volume (p < 0.001; respectively), and intracranial volume at last follow-up (p < 0.001; respectively). There was a significant increase in 3 months postoperative to intracranial volume at last follow-up (p < 0.001). The mean intracranial volume increased by an average of 36.6 percent (range, 18.1 to 79.2 percent) at last follow-up. The degree of hydrocephalus in the preoperative child was (45.77% ± 9.17%), and at the last follow-up after surgery, the degree of hydrocephalus was (35.02 ± 9.50%), p < 0.01). Preoperatively, 14 patients (73.7 percent) had radiographic evidence of Chiari malformation type I. The cerebellar tonsillar descent, measured using pre- and postoperative MRI, decreased in all patients after FFBF-PCVR (preoperative: 7.5 ± 1.4 mm, postoperative: 5.3 ± 1.7 mm; p = 0.001). FFBF-PCVR can efficiently expand the posterior cranial vault with only one surgical procedure. Moreover, it helps to relieve hydrocephalus and cerebellar tonsillar herniation.

Hinge Craniotomy for Posterior Cranial Vault Expansion: Using the Keel to the Surgeon's Advantage

Cranial vault reconstructions are a common craniofacial procedure utilized to treat chronically elevated intracranial pressure and its sequelae for children with craniosynostosis. These surgeries often involve split-thickness autologous grafts to facilitate intracranial volume expansion. The hinge craniotomy was developed by neurosurgeons in the early 2000s as an alternative to the hemicraniectomy to allow for greater space and simplified re-securing of the bone flap. In our report, we introduce a novel application of hinge craniotomy in total cranial vault reconstruction for a pediatric patient with microcephaly secondary to congenital cytomegalovirus infection. We performed bilateral barrel stave cuts to the occipital bone as well as an undercut along the midline keel to form a hinge craniotomy. Complex reconstruction followed to augment intracranial volume and restructure the cranial vault. This technique maximized intracranial volume expansion while minimizing the need for prolonged reconstruction. It also allowed for retained vascularization of the bone flap by maintaining the connection with the intact cranial base and pericranium to further support bony healing. Our study presents a novel utilization of hinge craniotomy, using the occipital keel as a natural hinge, to create ample space during cranial vault reconstruction. This technique offers potential advantages in terms of intracranial volume expansion and bony healing.

Syndromic Craniosynostosis: A Comprehensive Review

Craniosynostosis is a fetal skull condition that occurs when one or multiple sutures merge prematurely. This leads to limited growth perpendicular to the fused suture, which results in compensatory growth of cranial bones parallel to it. Syndromic craniosynostosis ensues when the cranial deformity is accompanied by respiratory, neurological, cardiac, musculoskeletal, and audio-visual abnormalities. The most common syndromes are Apert, Crouzon, Pfeiffer, Muenke, and Saethre-Chotzen syndromes and craniofrontonasal syndrome. Each of these syndromes has distinct genetic mutations that contribute to their development. Mutations in genes such as FGFR, TWIST, and EFNB1 have been identified as playing a role in the development of these syndromes. Familiarity with the genetic basis of each syndrome is not only essential for identifying them but also advantageous for current pharmacological investigations. Surgical treatment is often necessary for syndromic craniosynostosis to correct the cranial deformities. Advances have been made in surgical techniques for each specific syndrome, but further research is needed to develop personalized approaches that address the unique symptoms and complications of individual patients, particularly those related to neurological and respiratory issues. This group of syndromes included in cranial synostosis presents significant educational and clinical interest due to the wide range of symptoms and the variable course of the disease, especially in the last decades when crucial advances in diagnosis and treatment have been achieved, altering the prognosis as well as the quality of life of these patients. In summary, this article provides a comprehensive overview of syndromic craniosynostosis, including the genetic mutations associated with each syndrome and the surgical treatment options available.

Chiari I malformation: management evolution and technical innovation

BACKGROUND AND DEFINITION

In recent years thanks to the growing use of radiological assessment, Chiari I malformation became one of the major diseases for a neurosurgeon to deal with. CIM can be classified according to the extent of cerebellar tonsil tip into the foramen magnum being a protrusion over five mm considered pathological. Such a disease is a heterogeneous condition with a multifactorial pathogenetic mechanism that can subdivided into a primary and secondary form. Regardless of the form, it seems that CIM is the result of an imbalance between the volume of the braincase and its content. Acquired CIMs are secondary to conditions causing intracranial hypertension or hypotension while the pathogenesis of primary forms is still controversial.

PATHOGENESIS AND TREATMENT

There are several theories in the literature but the most accepted one implies an overcrowding due to a small posterior cranial fossa. While asymptomatic CIM do not need treatment, symptomatic ones prompt for surgical management. Several techniques are proposed being the dilemma centered in the need for dural opening procedures and bony decompression ones.

CONCLUSION

Alongside the paper, the authors will address the novelty presented in the literature on management, diagnosis and pathogenesis in order to offer a better understanding of such a heterogeneous pathology.

Changes in venous drainage after posterior cranial vault distraction and foramen magnum decompression in syndromic craniosynostosis

OBJECTIVE

The authors' objective was to measure the effect of posterior cranial vault distraction (PCVD) plus foramen magnum decompression (FMD) on dural sinus volume and venous flow in patients with syndromic craniosynostosis.

METHODS

The volumes of the sagittal, straight, transverse, and sigmoid sinuses of 5 consecutive patients with syndromic craniosynostosis who underwent PCVD+FMD were calculated in cubic centimeters with T2-weighted volumetric MRI sequences before surgery, immediately after surgery, and after the end of the distraction process. Tridimensional reconstructions of phase-contrast magnetic resonance angiography (PC-MRA) images were obtained with multiplanar reconstruction (MPR).

RESULTS

The average total volume of all dural sinuses increased immediately after surgery (from 10.06 cm3 to 12.64 cm3) and continued to increase throughout the 30-day distraction period (from 12.64 cm3 to 14.71 cm3) (p = 0.04), except that the right sigmoid sinus remained stable after the initial increase. The most important increases were observed for the left transverse sinus (+113.2%), right transverse sinus (+104.3%), left sigmoid sinus (+91.3%), and sagittal sinus (+41.8%). Less important modifications were evident for the right sigmoid sinus (+33.7%) and straight sinus (+23.4%). Significant improvements in venous flow were noted on the tridimensional reconstructions of the PC-MRA images. Venous obstruction grading score improved in 4 patients (average [range] 2.4 [ 2-5]) (p = 0.023) and remained stable in 1 patient. All patients had chronic tonsillar herniation (CTH) (mean [range] 16.6 [8-26] mm), and 3 had syringomyelia. CTH showed improvement on the last follow-up MRI evaluation in 4 patients (mean [range] 10.5 [0-25] mm) and worsened from 15 mm to 19 mm in 1 patient. Syringomyelia improved in 2 patients and remained unchanged in 1.

CONCLUSIONS

This study has provided the first radiological evidence of the impact of craniofacial surgery on dural sinus anatomy and venous drainage. The venous anomalies described in patients with syndromic craniosynostosis are not static, and PCVD+FMD triggers a dynamic process that can lead to significant modifications of intracranial venous drainage. The traction exerted by the distracted bone flap onto the occipitoparietal dura mater adherent to the inner calvaria may account for the enlargement of the dural sinus throughout the distraction period. The impact of these modifications on venous pressure, intracranial pressure, CTH, and hydrocephalus remains to be determined.