Magnetization Transfer Imaging and Proton MR Spectroscopy in the Evaluation of Axonal Injury: Correlation with Clinical Outcome after Traumatic Brain Injury

Proton MR spectrum obtained from normal splenium. The NAA/Cr ratio is 1.75. All spectra were acquired using a STEAM sequence (2000/31).

T2-weighted MR images (3000/90/1) at the level of the splenium in two different patients.

A, Despite the normal appearance of the white matter in the splenium (arrows), this patient had an MTR greater than 2 SD below normal values.

B, This patient has typical high signal in the region of the splenium (arrows), considered an indicator of severe diffuse injury.

A, Proton MR spectra obtained from the splenium of two patients with head injury. The arrow identifies the methyl resonance of NAA, which is at 2.02 parts per million. The top spectrum was recorded in a patient with an initial GCS of 14 and a GOS of 5 and an NAA/Cr of 1.52. The bottom spectrum shows a lowering in the NAA peak that results in a decreased NAA/Cr ratio of 1.16 in a patient with a GCS of 4 and GOS of 2.

B, T2-weighted MR image (2700/85/1) from patient in top spectrum in A.

C, T2-weighted MR image (2700/80/1) from patient in bottom spectrum in A shows postoperative changes from evacuation of a subdural hematoma and bilateral hygromas.

Relationship between NAA/Cr ratio and GOS score. Spearman's rank-order correlation indicates a significant correlation between NAA/Cr and outcome (Y = 0.142X + 0.819, r_s = 0.4378, P < .01).