Anomalous venous drainage preventing safe posterior fossa decompression in patients with Chiari malformation Type I and multisutural craniosynostosis

Abstract

The authors report on two children in whom an anomalous posterior fossa venous drainage pattern prevented safe posterior fossa decompression. Both patients had Chiari malformation Type I, multisutural craniosynostosis, and crowded posterior fossa structures. Both patients had been treated with ventriculoperitoneal shunts for hydrocephalus. Pfeiffer syndrome had been diagnosed in one of the patients, and the other was suspected to have osteogenesis imperfecta. Although both patients were believed to have symptoms resulting from brainstem compression, posterior fossa decompression was not offered due to profound venous anomalies noted on imaging studies that greatly increased the expected risks associated with surgery. These cases are presented to alert neurosurgeons to carefully evaluate the posterior fossa venous anatomy prior to considering posterior fossa decompression with or without occipitocervical fusion or calvarial vault remodeling procedures in patients with multisutural craniosynostosis.

Chiari malformation associated with craniosynostosis

“…In some cases, preoperative detection of major venous collaterals at the site of a proposed CM decompression may suggest that even bone removal at the foramen magnum is not safe and should not be performed. 1,37 In general, most surgeons agree that CM should not be treated unless it is symptomatic or, in some cases, associated with a spinal syrinx. It is possible that the indications for surgical treatment of CM may be different for individuals with associated craniosynostosis.…”

Spring-assisted cranial vault expansion in the setting of multisutural craniosynostosis and anomalous venous drainage: case report

“…Sandberg et al reported on 2 patients with multisutural craniosynostosis, Chiari I malformation, and prior VP shunt placement in whom posterior fossa decompression was avoided due to anomalous venous drainage patterns. 23 Preoperative CT angiography demonstrated hypoplastic jugular foramina and abnormal transosseous venous drainage to the neck and retromastoid region. In addition, Sanchez et al described the onset of facial edema 21 months after correction of BLSS at 2 months of age via strip craniectomy and spring placement; bilateral jugular foraminal stenosis was subsequently identified.…”

“…Unfortunately, it is this same patient population that is at most risk of developing anomalous intracranial venous drainage patterns. 1,2,4,10,12,14,19,20,22,23 These intracranial-to-extracranial collateral vessels develop in the occipital region, hindering safe exposure of the posterior calvaria during posterior vault remodeling and Chiari decompression. There are multiple reports in which cranial vault remodeling and Chiari decompression repairs were abandoned due to anomalous venous drainage patterns, either identified through preoperative imaging or intraoperatively.…”

“…There are multiple reports in which cranial vault remodeling and Chiari decompression repairs were abandoned due to anomalous venous drainage patterns, either identified through preoperative imaging or intraoperatively. 1,2,8,23 The precedent for this practice was set by the case of a patient who died after posterior vault remodeling and in whom anomalous venous drainage Patients with multisutural craniosynostosis can develop anomalous venous connections between the intracranial sinuses and cutaneous venous system through enlarged emissary veins. Cranial vault remodeling in this subset of patients carries the risk of massive intraoperative blood loss and/or occlusion of collateral draining veins leading to intracranial venous hypertension and raised intracranial pressure, increasing the morbidity of cranial expansion.…”

Suboccipital decompression during posterior cranial vault remodeling for selected cases of Chiari malformations associated with craniosynostosis

“…19 Along the same lines, separate reports have been published, recommending avoiding surgical intervention because of the perceived risk to the venous system. 15 In an effort to maximize venous drainage, we developed a technique to preserve these outflow tracts by leaving an island of surrounding bone through which anomalous venous channels course, while still decompressing the foramen magnum with this same surgical exposure. It has been our experience that this anatomy is predictable and may be adequately imaged with standard preoperative MRI.…”