Spondylolysis associated with Arnold-Chiari malformation and syringomyelia. A report of two cases

STUDY DESIGN: This is a report of two cases. OBJECTIVE: To document the occurrence and association of spondylolysis and Arnold-Chiari malformation Type I. SUMMARY OF BACKGROUND DATA: The association of spinal dysraphism has been reported with Arnold-Chiari Type II, but not with Arnold-Chiari Type I. METHODS: The senior author was involved in the care of these patients. All medical records, laboratory and radiologic investigations, and related literature were reviewed. RESULTS: The presence of cephalic and caudal neuropore maldevelopment may be present in various combinations. The presence of spondylolysis, with or without spina bifida occulta, associated with Arnold-Chiari malformation type I and syringohydromyelia, is demonstrated. CONCLUSIONS: In some patients, the presence of spondylolysis may represent a congenital anomaly and may be associated with cephalic neuropore maldevelopment, such as cerebromedullary malformation syndrome (i.e., Arnold-Chiari malformation Type I).