Associated Disorders of Chiari Type I Malformations

A Review

Marios Loukas, M.D., Ph.D.; Brian J. Shayota, B.S.; Kim Oelhafen, B.S.; Joseph H. Mill er, M.D.; Joshua J. Chern, M.D., Ph.D.; R. Shane Tubbs, M.S., P.A.-C., Ph.D.; W. Jerry Oakes, M.D.


Neurosurg Focus. 2011;31(3):e3 

In This Article


Craniosynostosis and CM-I is a well-documented association first noted by Saldino et al.,[58] in which certain patients will have abnormalities in the skull base with subsequent decreased posterior fossa volume and tonsillar herniation. More specifically, this most often occurs when the lambdoid sutures fuse too early in skull development, which is representative of 1% of all types of craniosynostosis.[21] Synostosis can exist solitarily or as part of a syndrome such as Crouzon (72.7%), Apert (1.9%), Pfeiffer (50%), and Kleeblattschädel syndromes (100%).[8,9] Additional studies estimated the Crouzon syndrome association to be as high as 70%.[63] Moreover, CM-I is now believed to be associated with Pfeiffer Type II,[50] Jackson-Weiss,[46] Seckel,[22] Antley-Bixler,[6] and Shprintzen-Goldberg syndromes[17] as well. In each of these associated syndromes, CM-I is not present at birth because the lambdoid suture has not yet fused. The incidence and severity, however, has been correlated to the time of closure.[24,54] Therefore, the higher incidence of CM-I in patients with Crouzon syndrome can be explained by the timing of fusion of involved sutures as compared with Apert syndrome.[8] Normally, the skull continues to expand along with brain growth until the age of 16 years.[37]

Although lambdoid synostosis is the most common type of craniosynostosis to be associated with CM-I, evidence of additional premature suture closures leading to CM-I is growing. In utero synostosis of the sagittal and coronal sutures, for example, can force neural growth posteriorly and inferiorly as is present in the association with Loeys-Dietz syndrome.[57] As a result, the attachment of the tentorium cerebelli is displaced toward the foramen magnum with subsequent reduction in posterior fossa size and development of CM-I.[9] Additionally, Tubbs et al.[66] reported a 30% incidence of CM-I associated with simple metopic ridging without signs of trigonocephaly; Tubbs et al.[65] hypothesized that this was the result of a decrease in anterior cranial fossa volume.