Chiari I malformation - a review

Abstract

Introduction: Chiari malformations (types I-IV) are a group of complex brain abnormalities in the lower posterior skull that can lead to herniation of cerebellar tonsils into the spinal canal, sometimes causing non-communicating hydrocephalus. This condition is mostly presented at birth (congenital), although in many cases they may not become clinically apparent until adulthood.Aim: The aim of this work is to underline the pathophysiology, clinical manifestations and treatment of Chiari I malformation.Material and methods: Chiari type I malformation is the most common and the least severe of the spectrum, often diagnosed in adulthood. The cerebellar tonsils are displaced below the level of the foramen magnum, which causes compression of the cervicomedullary junction and interruption of normal flow of cerebrospinal fluid (CSF) leading to clinical syndrome. It is hypothesized that Chiari type I originates as a disorder of para-axial mesoderm, which results in formation of a small posterior fossa.Symptoms of Chiari I develop as a result of: (1) compression of medulla and upper spinal cord, (2) compression of cerebellum, and (3) disruption of CSF flow through foramen magnum. Compression of the cord and medulla may result in myelopathy and lower cranial nerve dysfunction. Compression of cerebellum may result in ataxia, dysmetria and nystagmus. Disruption of CSF flow through foramen magnum accounts for the most common symptom - pain.Results: MRI is the most widely used imaging study for diagnosing Chiari malformation.  Patients with CM who have minimal or symptoms without syringomyelia can be treated conservatively. Symptomatic patients should be offered surgical treatment. Its goals are decompression of cervicomedullary junction and restoration of normal CSF flow in the region of foramen magnum.Conclusion: It has been noted that early surgical intervention is associated with better outcome in cases of symptomatic Chiari I malformation.