Fibre tracking in patients with persistent vegetative state

Objective: The diagnosis of persistent vegetative state is still limited to the clinical examination. Imaging techniques do not play a role in securing the diagnosis and or the probability of repair. Using fibre tracking (FT), it was tried to visualize and quantify the defect areas. Methods: Seven patients in a persistent vegetative state after cerebral trauma were examined in a 1.5-T MRI device (INTERA, Philips Co) with coronal diffusion-weighted spin echo sequences. MRI was performed after a mean of 6 months following cerebral trauma. Six non-colinear gradient impulses were used along the corticospinal fiber tracts. For reconstruction of the fibers courses, an IDL-based (Interactive Data Language; Research System Inc.) fiber tracking tool was used. Furthermore, ADC (apparent diffusion coefficient) and FA (fractional anisotropy) were determined in the defect area and compared with a control group of 20 healthy test persons. Results: The fiber representation showed an interruption of the corticospinal fiber tracts at the level of the mesencephalon in all patients. The ADC values in the defect area were normal to slightly increased as compared to the control group. The FA values were reduced by nearly 40%, indicating a permanent damage on the cellular level. Discussion: With the help of DTI, the interruption of corticospinal fiber tracts could first be visualized in patients with persistent vegetative state. The FA values can be regarded as markers of the damage on the cellular level and might be important for indicating reversibility of persistent vegetative state.