Evidence for cellular damage in normal-appearing white matter correlates with injury severity in patients following traumatic brain injury - A magnetic resonance spectroscopy study

Neuropsychological studies in patients who have suffered traumatic brain in jury show that the eventual clinical outcome is frequently worse than might be predicted from using conventional (CT or T-1/T-2-weighted MRI) imaging. Furthermore, patients who have sustained an initial mild or moderate injur y may show long-term disability. This implies that there may be abnormaliti es in areas of the brain that actually appear normal on conventional imagin g. Proton magnetic resonance spectroscopy studies have shown that N-acetyla spartate and choline-containing compounds can provide measures of cellular injury. We report MRT and proton magnetic resonance spectroscopy studies of 19 head-injured patients performed once the patients were clinically stabl e (mean 11 days after injury, range 3-38 days), Proton magnetic resonance s pectra were acquired from frontal white matter that on conventional MRI app eared normal. that brain matter The on N-acetylaspartate/creatine ratio was reduced [patients (mean +/- standard deviation), 1.28 +/- 0.25; controls, 1.47 +/- 0.24; P = 0.04] and the choline/creatine ratio was increased (pati ents, 0.85 +/- 0.18; controls, 0.63 +/- 0.10; P < 0.001) compared with cont rols, when the severity of the injury was assessed using either the Glasgow coma scale or the length of post-traumatic amnesia, the increase in the ch oline/creatine ratio was significant even in the mildly injured group (P = 0.008 and P = 0.04, respectively). Furthermore, there was a significant cor relation (P 0.008) between the severity of head injury and the N-acetylaspa rtatelcholine ratio. We conclude that there is an early reduction in N-acet ylaspartate and an increase in choline compounds in normal-appearing white matter which correlate with head injury severity, and that this may provide a pathological basis for the long-term neurological disability that is see n in these patients.