To The Editor:
We read with interest the paper entitled "Clinical Value
of Routine Preoperative Magnetic Resonance Imaging in Adolescent
Idiopathic Scoliosis. A Prospective Study of Three Hundred and Twenty-seven
Patients" (2001;83:577-9), by Do et al. In our practice,
we also found only a few cases of abnormalities noted on magnetic
resonance imaging in patients with adolescent idiopathic scoliosis,
and we agree with the authors’ conclusion that magnetic
resonance imaging should not be performed routinely before arthrodesis
of the spine in patients with adolescent idiopathic scoliosis and
a normal physical and neurological examination.
However, we find the authors’ reference to patients
with abnormalities termed an "Arnold-Chiari type-I malformation" and
an "Arnold-Chiari malformation" to be confusing.
If the authors specifically meant abnormalities such as the caudal
displacement of the cerebellar tonsils associated with syringomyelia,
we think that "Chiari I malformation" is a less
misleading term.
Malformation of the posterior cranial fossa was first described
in the pathology literature in the late nineteenth century. Although
Cleland described a case of deformity of the medulla, tectum, and
meningocele (now known as a Chiari II malformation) in 18831, it was Chiari who categorized a
series of malformations in the posterior cranial fossa2, and his work is still valid. Arnold
later reported a case of cerebellar anomaly3,
and the term "Arnold-Chiari malformation" was
coined by his colleagues to designate cerebellar herniation and anomaly
of the posterior cranial fossa4.
The term "Arnold-Chiari malformation" is now specifically
used to designate the anomalies formerly defined by the category "Chiari
II malformation," although the former term is not used
so frequently.
T.T. Do, C. Fras, S. Burke, R.F. Widmann, B. Rawlins,
and O. Boachie-Adjei reply:
We appreciate Drs. Ehara and Shimamura’s very astute
observations concerning the Arnold-Chiari malformation and the original
articles that they referenced.
While we agree with them about the semantics of the terminology
in that the Chiari I malformations (low-lying tonsils) are to be
distinguished from the Arnold-Chiari type-II, III, and IV malformations
(which involve cerebellar and ventricular anomalies, including herniation),
we opted to keep the terminology that we used in our article to allow
the reader to distinguish between Chiari type-I and type-II malformations.