Preliminary Observations on the Association between Simple Metopic Ridging in Children without Trigonocephaly and the Chiari I Malformation

Abstract

Historically, there have been no accounts of an association between simple metopic ridging and the Chiari I malformation. We prospectively evaluated 50 children with simple metopic ridges and found that 30% of these patients had a Chiari I malformation. During the period in which this screening for simple metopic ridges was performed, only 9% of the total patient population (324) was diagnosed as having a Chiari I malformation. We hypothesize that small decreases in anterior fossa volume in children with a simple metopic ridge and no other clinical findings of trigonocephaly may increase their chance of having a Chiari I malformation that becomes symptomatic. In addition, simple metopic ridging should perhaps be added to the list of bony anomalies associated with the Chiari I malformation, such as atlantal assimilation and retroverted odontoid processes. Future studies aimed at calculating anterior fossa volumes in children with a Chiari I malformation and imaging all children with simple metopic ridges are now necessary to ascertain if there is an increased risk of these patients becoming symptomatic with a hindbrain hernia or having a hindbrain hernia, respectively.

Chiari malformation associated with craniosynostosis

“…2,17,25,41 Most of these cases involve the lambdoid suture, but CM has been reported even in conjunction with sagittal, metopic, and unilateral coronal synostosis. 2,17,25,41 Leikola et al 17 reported on a series of 124 patients with single-suture craniosynostosis and, on imaging, found that 7 (5.6%) had CM. Sgouros et al 38 showed that cranial base growth is altered in both multi-and single-suture craniosynostosis, even in cases that do not exhibit premature fusion of a cranial base synchondrosis.…”

“…36 Chiari malformation occurs in patients with both syndromic and nonsyndromic forms of craniosynostosis. 5,7,9,17,18,41,42 Up to 70% of individuals with Crouzon syndrome and 50%-82% of those with Pfeiffer syndrome have associated CM. 4,5,7 There are also several reports of CM with nonsyndromic synostosis involving the sagittal, coronal, and even the metopic sutures.…”

“…4,5,7 There are also several reports of CM with nonsyndromic synostosis involving the sagittal, coronal, and even the metopic sutures. 17,25,41 Cerebellar tonsillar ectopia in patients with craniosynostosis is thought to arise from disproportionately slow growth or the small size of the posterior fossa in many cases. 5 Hydrocephalus, venous hypertension, and associated congenital brain anomalies have also been proposed as possibly important factors leading to CM development in these patients.…”

Children with metopic ridge

“…According to Hopper et al, pathological synostosis must be distinguished from metopic ridging, which is a variant of normal development of the metopic suture with no other features of trigonocephaly (9). Tubbs et al used the term simple metopic ridging without trigonocephaly, reporting their observations on the possible association with Chiari I malformation (14). Van der Meulen mentioned that the primordia of trigonocephaly can be seen in children with a metopic ridge due to increased bone deposition along the suture, with an unknown etiology and no other clinical or radiological features (15).…”

Associated disorders of Chiari Type I malformations: a review

“…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.…”