J Korean Neurosurg Soc.  2010 Oct;48(4):375-379.

Chiari 1.5 Malformation : An Advanced Form of Chiari I Malformation

• Kim IK
• Wang KC
• Kim IO
• Cho BK

Abstract

The Chiari 1.5 malformation is defined as a tonsillar herniation within a Chiari I malformation with additional caudal descent of the brainstem through the foramen magnum. We describe a patient with Chiari I malformation who evolved to Chiari 1.5 malformation during longitudinal follow-up. A 15-year-old girl presented with neck pain during exercise for two years. She had been diagnosed with Chiari I malformation with mild hydrocephalus after minor cervical trauma at the age of six years. At that time, she was asymptomatic. After she complained of aggravated neck pain, neuroimaging (nine years after first imaging) revealed caudal descent of the brainstem and syringomyelia in addition to progression of tonsillar herniation. Posterior fossa decompressive surgery resulted in complete resolution of neck pain. Based on neuroimaging and operative findings, she was diagnosed as Chiari 1.5 malformation. Neuroimaging performed seven months after surgery showed an increased anterior-posterior diameter of the medulla oblongata and markedly decreased syringomyelia. This case demonstrates progressive developmental process of the Chiari 1.5 malformation as an advanced form of the Chiari I malformation.

Keyword

Chiari 1.5 malformation; Asymptomatic hydrocephalus; Syringomyelia

MeSH Terms

Adolescent
Brain Stem
Encephalocele
Follow-Up Studies
Foramen Magnum
Humans
Hydrocephalus
Medulla Oblongata
Neck Pain
Neuroimaging
Syringomyelia