The Chiari Malformations by R. Shane Tubbs & W. Jerry Oakes

Author:R. Shane Tubbs & W. Jerry Oakes
Language: eng
Format: epub
Publisher: Springer New York, New York, NY

Incidence of Bony Anomalies Associated with Chiari I Malformation

In a recent comprehensive review of 364 symptomatic patients with Chiari I malformation, Milhorat et al. found associated syringohydromyelia in 65 % of cases, scoliosis in 42 %, an abnormal retroflexed odontoid process in 26 %, and basilar invagination in 12 % [18]. This is a series which was not skewed to bony abnormalities at the craniocervical junction. In contrast, this author reviewed our Chiari I malformation database, which was different from the craniovertebral junction database, in 2005 [17]. A total of 639 patients had undergone an operative procedure for a Chiari I malformation. Two hundred and seventy-six of these had craniovertebral junction bony abnormalities of which 41 were reducible and 46 % had syringohydromyelia. There were 363 patients who did not have a bony abnormality at the craniocervical junction. The incidence of instability in these patients was 8 %. Sixty-seven percent had syringohydromyelia.

In a study “based on 190 surgically treated patients with basilar invagination,” Goel et al. [6] grouped these into those that did have a Chiari I malformation and those that did not have a Chiari malformation. Eighty-eight of the 190 patients with basilar invagination did not have a Chiari malformation. One hundred and two patients had a Chiari I malformation associated with the basilar invagination and 50 % had a syrinx. Perrini et al. reviewed their surgical management of craniovertebral junction malformations and recognized 34 adult patients in a 7-year span who underwent operation [20]. This was for basilar invagination, and 13 of the 34 had an associated Chiari I malformation. Of these, three had a syrinx. In a long-term follow-up of Chiari-related syringomyelia in adults, Aghakhani et al. analyzed 157 surgically treated cases of Chiari-related syrinx and found that only 11 of the 157 (7 %) had basilar invagination or “platybasia” and basilar impression [1]. Thus, the incidence of a Chiari I malformation having craniovertebral junction bony abnormalities is between 7 and 11 % [11, 12]. On the other hand, the incidence of craniovertebral junction bony abnormalities having a hindbrain herniation present is between 33 and 38 % [13]. Table 14.1 refers to the associated bony anomalies with the Chiari I malformation in whom instability may be present at the craniocervical junction. In this author’s series, these can be conveniently divided into those of congenital origin, the developmental and the acquired [12, 21].Table 14.1The Chiari malformations: associated bony anomalies/instability

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