Diffusion Tensor Imaging (DTI) in patients in a state of brain death

Aims: Traditionally the diagnosis of brain death is established on the basis of a combination of clinical signs and paraclinical methods. The picture giving did not play a role during the diagnostic safety device. The study investigated the potency of different magnetic resonance (MRI) techniques to evaluate brain death after brain injury or spontaneous intracranial haemorrhage.

Material and methods: In 10 patients, follow up examinations in deep coma and after evaluation of brain death (according to the German guidelines) were performed in 1.5 Tesla MRT (INTERA, Philips Co) with coronal diffusion-weighted spin echo sequences. Six non-colinear gradient impulses were used along the corticospinal fiber tracts. DTI was performed in addition to conventional sequences (T2 (tse), T1 (se) and FLAIR). Furthermore, ADC (apperant diffusion coefficient) and FA (fractional anisotropy) were determined in the pons and compared with a control goup of 20 healthy test persons.

Results: In MRI, all patients reveal a bipontine lesion in deep coma and the signs of infratentorial (tonsillar) herniation in brain death. The fiber representation showed an interruption of the corticospinal fiber tracts at the level of the pons in all patients. The ADC values were reduced by nearly 50%. The FA values in the pons were normal to the control group.

Conclusion: MRI in the evaluation of brain death has two dimensions: 1. predicting the evolution of brain death by structural MRI and 2. a possible future diagnosis of brain death based on quantitative analysis of DTI with ADC values.