To our knowledge, this is the largest documented cohort of patients with syndromic craniosynostosis. Anomalous intracranial venous anatomy is well described in this population.5 The increased recognition of these anomalies carries significance with respect to surgical planning and morbidity. Venous hypertension due to outflow obstruction increases the risk of significant blood loss during reconstructive surgery and contributes to the development of hydrocephalus with a subsequent increased risk for postoperative CSF leak.3,10 In the setting of severe DVS stenosis, transosseous collaterals and persistent fetal sinuses may represent the primary route of venous drainage. These anomalous vessels pose significant surgical risks, including intraoperative hemorrhage, air embolism, and potentially lethal venous hypertension due to inadvertent closure of transosseous collaterals.3,11 Although there are risks to imaging in the form of ionizing radiation (CT) and general anesthesia (MRI), these risks are warranted, given the potential for significant morbidity and mortality if this information is not included in the surgical planning.
The results of our study and of others demonstrate that preoperative planning must include an evaluation of IVA in most cases. Thompson et al.3 provided a salient example of the potential for significant surgical morbidity in an 8-year-old girl with Pfeiffer syndrome who suffered fatal intracranial hypertension after a large occipital emissary was sacrificed during the scalp incision for a cranial vault expansion. At autopsy, it was discovered that there were severe, bilateral stenoses of the jugular foramina and the occluded occipital emissary vein was the primary route of drainage. There are several other reports in which the detection of IVA on preoperative vascular imaging led to the cancelation of posterior vault expansion procedures.1,2,6 No large studies currently exist, however, providing a description of the types of anomalies seen by syndrome, and the relationship to outcome with respect to surgical planning and potential morbidity. In children, the radiation or general anesthesia required to obtain imaging necessitates that any study be justified. As a result, we assessed the incidence of IVA by syndrome and the clinical significance of these anomalies.
In our study, anomalous IVA was identified in 76% of patients. Both collateral drainage and DVS stenosis were common. Abnormal transosseous veins were observed in 63% of patients. The most common anomalous collaterals were occipital and mastoid emissary veins, posing significant surgical risk for posterior vault and suboccipital procedures. Condylar and parietal emissaries were less common; however, knowledge of their frequency and most associated syndromes is important as they are relevant for more anterior or combined approaches. In addition to these transosseous anomalies, we noted significant abnormalities in the normal intracranial drainage mechanisms. Twenty-eight patients (68%) had DVS stenosis, which was most commonly bilateral (78%) and involving the sigmoid-jugular complex (98%). Twenty patients (49%) had jugular foramen stenosis, which was severe or complete in all patients, bilateral in the majority (75%) and was always associated with DVS stenosis. Persistence of occipital and marginal fetal sinuses was less frequent, only occurring in 19% of patients.
Frequency of IVA by syndrome is important in informing preoperative work-up and assessment. We found that IVA, were most common in Pfeiffer (100%) and Crouzon (84%) and slightly less common in Apert patients (64%). We cannot make any statements as to associations with Saethre-Chotzen and Muenke syndromes as there were only 3 patients and 1 patient in our cohort, respectively. Given these numbers overall, we recommend preoperative vascular imaging in all syndromic patients.
Many reports have demonstrated similar variability in venous drainage in children with complex synostosis. Jeevan et al.6 demonstrated that of 11 patients with syndromic synostosis, 9 had enlarged emissary veins, and 4 of these patients had a transosseous route as their primary route of drainage on CTV. Taylor et al.8 studied 23 synostosis patients, 18 of whom were syndromic and found that 17 patients had either severe stenosis (51–99%) or no flow in the sigmoid sinus and/or jugular complex by digital subtraction angiography. In 11 patients, significant venous collaterals were seen in the region of the stylomastoid emissary vein. In a study done by Rollins et al.7, MRV showed jugular stenosis and transosseous venous drainage in 12/17 patients with complex craniosynostosis, only 11 of which were syndromic. The most common emissary veins were posterior condylar, seen in 11/17 patients. These results contrast with the present study where occipital (44%) and mastoid (39%) emissaries were seen most frequently, with condylar emissaries being observed in only 7% of patients. These condylar emissaries were most common in Crouzon syndrome (67%). This may be due to differences in patient population studied as 6/17 patients were nonsyndromic in the Rollins et al.7 paper.
With respect to the significance of IVA in the present study, morbidity was not significantly associated with IVA. Although there was a trend toward increased EBL based on the number of emissaries and DVS type, these findings were not significant. In addition, although there was a significant relationship between IVA and elevated ICP, shunted hydrocephalus, Chiari malformations, and obstructive sleep apnea, there was no significant difference in complication rate between patients with and without IVA. Surgical morbidity was more closely related to the associated conditions than to the anomalous drainage itself. The skull fracture and resulting epidural hematoma, for example, was most likely secondary to significant thinning of the skull from chronic hydrocephalus. Similarly, the CSF leak was likely related to hydrocephalus and elevated ICP.
Although no procedures were abandoned in the present study, there were 5 cases in which the procedure was altered to accommodate the venous anatomy. This is compared to the study by Jeevan et al.6 in which abnormal venous anatomy led to the abandonment of operative intervention in 4, and a change in the planned procedure in an additional 3 cases. Importantly, however, all our study patients had undergone preoperative venous imaging, therefore allowing for preoperative planning. Comparison of outcomes with and without venous imaging would be more informative with respect to the true morbidity associated with these radiographic findings. However, with the current accrual of information surrounding the prevalence of IVA in syndromic synostosis, a controlled prospective study would be unethical. Additionally, the association between the type and location of procedure and EBL was investigated and found to be insignificant. This further underscores the fact that the trend toward an association between blood loss and IVA may be independently significant in a larger cohort as it cannot be explained simply by the type of surgery performed.
Our study was limited by the fact that we did not have control subjects to assess normal variation in venous drainage. Instead, our definitions of “anomalous” versus “not anomalous” were based on the current literature and neuroradiology reports. Additionally, since this was a retrospective review, the number of previous cranial vault procedures and VP shunts at the time of venography was not standardized. Therefore, whether the venous anatomy had been affected by prior operative intervention is not known. However, Jeevan et al.6 studied 11 patients with syndromic craniosynostosis using CTV and “found no relation between … the existence of previous cranial surgery and the presence of collateral venous drainage channels.” Although cranial vault remodeling does not address jugular foraminal stenosis, it decreases craniocephalic disproportion and intracranial pressure. In this respect, prior intervention may be expected to decrease venous anomalies in the form of emissaries and dural stenoses. However, it is also possible, depending on preoperative anatomy, that sacrificing emissaries intraoperatively would worsen preexisting anomalies and potentially increase the likelihood of related issues such as elevated intracranial pressure and hydrocephalus. This will be an important relationship to study in a standardized, prospective fashion to help inform our understanding of the etiology of these anomalies in craniofacial syndromes.
This study represents the largest cohort of children with syndromic craniosynostosis and the results demonstrate a high incidence of IVA in this population. These data therefore allow for a more accurate assessment of the most common venous drainage patterns and their clinical significance. Additionally, the categorization of DVS stenosis based on proximity to the skull base or jugular foramen allows for a more standardized method of documentation.
Increased recognition of these anomalies carries significance with respect to surgical planning and reducing morbidity in the treatment of these patients. Based on the incidence and pattern of venous anomalies found in the present study, we recommend venous imaging as part of preoperative planning in all children with syndromic craniosynostosis. Where previous studies have not been able to stratify their recommendations based on phenotype due to small sample sizes, we assert that preoperative venous imaging is most crucial in patients with Pfeiffer, Crouzon, and Apert syndrome.
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Copyright © 2018 The Authors. Published by Wolters Kluwer Health, Inc. on behalf of The American Society of Plastic Surgeons.
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