Ruolo della Neuroradiologia nella diagnostica della malformazione di Chiari di I tipo

Abstract

Chiari's type I malformation is defined as the caudal displacement of the cerebellar tonsils into the occipital foramen, sometimes associated with displacement of the cerebellar vermis. Syringomyelia is present in 65% of patients with Chiari's type I malformation and in 25% of all cases of tonsillar ectopia detected by MR scan. In contrast, asymptomatic syringomyelia is sporadic. MR investigation of the whole spinal cord is indicated when Chiari's type I malformation is present. Although the incidence of symptomatic patients increases when the ectopia exceeds 5 mm, there are no statistically significant correlations between the size of cerebellar ectopia and the incidence of syringomyelia or the degree of other clinical manifestations such as headache, Ménière's syndrome and inferior cranial nerve impairment. Symptoms and hence prognosis and possible surgical treatment depend not only on the tonsillar displacement, but on its impact on CSF dynamics. Cine-MR scanning offers great potential in the assessment of CSF dynamics in the occipital foramen, revealing asymptomatic subjects at risk of developing syringomyelia. The surgical treatment of this category of patients remains a controversial topic.