Association between Noonan syndrome and Chiari I malformation: a case-based update

Background Chiari I malformations (CM-I) have been associated with a variety of developmental abnormalities in the literature. A few cases of CM-I in patients with Noonan syndrome (NS) have been reported; however, opinion remains divided as to whether the observed association is coincidental. Discussion Six previous cases of CM-I in patients with NS have been described in the literature. Many of these had other neurological abnormalities; however, neurological problems are not a prominent part of earlier descriptions of NS. A statistically significant association between NS and CM-I is difficult to obtain at present due to availability and logistical issues with scanning many asymptomatic patients. Although we believe a link exists between CM-I and NS, there is little understanding on how NS may cause CM-I. The most logical cause would be posterior fossa abnormality; however, the most common genetic mutation in NS tends to cause frontal and facial abnormalities, and the posterior fossa tends to be relatively spared. Other genetic mutations may also affect the posterior cranium and thus create the appropriate conditions for a CM-I to develop. Illustrative case We report a case of CM-I in a 9-year-old patient with Noonan syndrome, severe scoliosis and syringomyelia. Conclusion We believe that CM-I is a part of Noonan syndrome; however, statistical validation of this opinion is necessary.