Clinical Application of Diffusion Tensor Imaging in Chiari Malformation Type I- Advances and Perspectives. A Systematic Review.

BACKGROUND: Diffusion tensor imaging (DTI) application in Chiari malformation type I (CMI) is still poorly defined. This study aimed to systematically review the literature and propose perspectives toward the clinical application of DTI in CMI.

METHODS: PubMed and Embase were searched for English-language articles published until October 20, 2020. Clinical studies and case series, evaluating fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), or radial diffusivity values in patients with CMI, were included.

RESULTS: Eight articles were included. Lower FA values were found at the syrinx level, which decreased with syrinx extent and intensity of symptoms, reflecting myelopathy severity. Decreased AD and MD in the middle cerebellar peduncles in symptomatic patients with CMI might explain the presence of cerebellar signs. Increased FA in various supratentorial structures positively correlated with pain severity. Worse performance in neuropsychological tests correlated with decreased FA, increased MD, and radial diffusivity, reflecting axonal degeneration. Postoperative FA decrease in the brainstem compression area reflects successful decompression. A positive correlation was found between the extent of tonsillar ectopia and increased FA, MD, and AD values, which could act as an early indicator of acute brainstem compression.

CONCLUSIONS: DTI might provide a valuable insight into the neurobiological foundation of symptomatic CMI presentation. The severity of white matter injury evident on DTI could serve as a reliable predictor of postoperative outcomes, therefore facilitating selection of appropriate surgical candidates. Postinterventional DTI reassessment might enable differentiation between unsuccessful surgical technique and irreversible myelopathy. The extent of tonsillar ectopia reflects the severity of microstructural brainstem injury.