PURPOSE: Hydrocephalus during infancy is a relatively common condition, most frequently treated by cerebrospinal fluid diversion with ventriculoperitoneal (VP) shunting. Secondary craniosynostosis is the premature fusion of ≥1 cranial sutures following VP shunt placement for hydrocephalus and has been reported with varying incidence in the literature. The effect of external forces on the etiology of craniosynostosis has been postulated, and decompressive forces resulting from alterations in cerebrospinal fluid pressure may precipitate premature sutural fusion. We examined the incidence of secondary craniosynostosis after VP shunt placement for infantile hydrocephalus to investigate the underlying pathophysiology of shunt-related craniosynostosis (SRC).
METHODS: The authors performed a retrospective chart review and direct examination of serial computerized tomography (CT) images for 127 patients at a single institution who underwent VP shunt for hydrocephalus in infancy. Demographic information, syndromic diagnoses, comorbidities, hydrocephalus etiology, timing of shunt placement, and necessity of shunt revisions were evaluated for each patient. Pre and postoperative CT scans were evaluated for sutural fusion, ventricular size, and degree of ventricular decompression. These data were then analyzed to determine any association between these independent variables and the development of craniosynostosis after shunt placement.
RESULTS: Sixty-three patients (49.6%) developed radiographic evidence of SRC within a median of 26 months after VP shunt placement in our study. A total of 5 patients had a syndromic diagnosis, with only one (Pfeiffer syndrome) being associated with primary craniosynostosis. Older age at shunt placement and greater number of shunt revisions were found to be associated with the development of SRC. Gender, gestational age, syndromic diagnosis, degree of ventricle decompression, and etiology of hydrocephalus did not differ between the fused and nonfused groups. Thirty patients had radiographic evidence of single suture fusion, whereas the remaining 33 had multisuture fusion. Among patients with single suture craniosynostosis, the sagittal suture was most commonly involved (86.7%), whereas in multisuture synostosis, >50% demonstrated fusion of the sagittal and bilateral coronal sutures. Of note, the presence of SRC was not documented in virtually all official CT reports.
CONCLUSION: The results of this study demonstrate that nearly 50% of patients who underwent VP shunt placement for a diagnosis of hydrocephalus in infancy developed SRC. This secondary fusion is often overlooked on routine CT interpretation, and accurate diagnosis requires a high level of suspicion. Our findings support the important role that proper dural stimulation and expansion plays in maintaining cranial sutural patency. Disruption of these normal processes may be a significant factor in the development of nonsyndromic craniosynostosis, with the sagittal suture being most vulnerable to early secondary fusion.