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


Reduced posterior fossa volume is also observed in other medical conditions, including those involved in cell signaling. For example, growth hormone deficiency has been linked to CM-I in 5%–20% of patients with growth hormone deficiency.[20,77] This endocrine deficiency in children is believed to be a physiological mechanism for insufficient development of the posterior fossa with resultant tonsillar herniation.[78] While the posterior fossa volume of patients with growth hormone deficiency has not been found to be significantly smaller, research has shown certain bone structures to be underdeveloped, similar to those commonly noted in patients with CM-I.[78] Additionally, somatotropin replacement therapy in patients with growth hormone deficiency and CM-I has resulted in improvement of tonsillar herniation with stabilization in syrinx size in some patients.[80] Conclusive evidence, however, of the pathophysiological mechanism and possible treatments has yet to be determined.

Acromegaly has also been implicated as an endocrine-related disorder causing CM-I, which also fits in the category of hyperostosis (excessive bone growth). In this scenario, an excessive amount of growth hormone is believed to thicken the bones of the posterior fossa, resulting in CM-I. Chiari Type I malformation has also been observed in patients with achondroplasia because of the small, shallow posterior cranial fossa present in these patients.[38]