The September 12 post reviewed the study by Yilmaz et al. on the surgical treatment of the Chiari I malformation (CM-I) published in February 2011 issue of World Neurosurgery. The authors compared the results of posterior fossa decompression for the CM-I in 24 patients treated without duraplasty to 58 patients treated with duraplasty. The authors concluded “that the risk of CSF leak has to be accepted as a downside of the essential procedure, which is opening the dura and widening the cisternal space."
In a Commentary in the same issue, UCLA neurosurgeon Dr. Ulrich Batzdorf provides perspective by reviewing the factors that should be considered when planning surgical decompression for CM-I:
In planning posterior fossa decompression, one must consider several factors, including 1) degree of tonsillar descent; 2) architecture of the posterior fossa; 3) shape of the cerebellar hemispheres, including the presence of arachnoid cysts; 4) presence of syringomyelia; 5) associated congenital anatomical variants such as atlas assimilation; 6) stability of the craniocervical junction; 7) presence of hydrocephalus; and 8) presence of co-existing cord tethering mechanism.
The goal of the decompression, as Batzdorf notes, is “restoration of normal cerebrospinal fluid (CSF) circulation at the foramen magnum and relief of brainstem compression.” This is obtained by creation of “a sufficiently large subtonsillar cistern.”
The key critique of the Commentary: “The aim should be accomplished by a single surgical procedure, rather than subject the patient to repeat operations.” Dr. Batzdorf reserves this recommendation for adults and outlines various factors that make Chiari malformation different in early childhood or infancy. (emphasis added)
He favors also performing tonsillar shrinkage using bipolar coagulation instead of relying on the duraplasty alone and the “possibility that the tonsils will be able to ascend sufficiently over time.” He also emphasizes the importance of opening the dura to evaluate for “significant intradural pathology, such as an arachnoid web obstruction the fourth ventricle outlets, or even a retained rhombic roof.”
In summary, Dr. Batzdorf advises duraplasty be performed in adults undergoing posterior fossa decompression for Chiari malformation. The debate regarding the two techniques, as applied in adults, hinges on the issue of complications, in particular CSF leak. More on this in the next post.
John Oró, MD