Role of Magnetic Resonance Spectroscopy in Traumatic Brain Injury

Neuro-imaging methods are of considerable value for the acute assessment and management of traumatic brain injury. An evaluation of functional and metabolic changes with magnetic resonance spectroscopy (MRS) can improve sensitivity for the detection of axonal injury.

To determine the usefulness of MRS in predicting neurological outcome in patients of closed head injury; to determine if there is any correlation between the computed tomography (CT) and MR findings with the neuro-metabolite maps obtained by MRS.

The study comprised 50 patients of closed head injury less than 24 h duration. Patients were categorised as mild, moderate and severe on the basis of Glasgow Coma Scale (GCS) score. All patients having GCS scores <15 underwent conventional CT, magnetic resonance imaging and proton MRS. The findings were correlated to assess the patient's outcome at the time of discharge and at 3 months by using Glasgow Outcome Scale (GOS).

Data analysis was done by using Analyze-it software (Leeds, UK). Correlation of neurometabolites with GCS and GOS was done using Spearman's Correlation Rank Test.

The patients in mild head injury group showed cerebral contusion with or without subdural haemorrhage or extradural haemorrhage or subarachnoid haemorrhage. Patients with moderate injury in addition showed presence of corpus callosal contusion with mild/moderate diffuse cerebral oedema seen in three and five patients, respectively. The patients in severe head injury group showed evidence of diffuse axonal injury in 11 patients with significant midline shift more than 5 mm in 10 patients and presence of moderate-to-severe diffuse cerebral oedema in all 14 patients. Comparison of the spectral analysis of the mild group with the control showed significant reduction in the N-acetylaspartate (NAA)/creatine (Cr) ratio in the splenium with significant increase in choline (Cho)/Cr ratio both in the splenium and occipital lobe. Spectral analysis of patients in moderate head injury group showed splenial NAA/Cr ratio of 3.48 ± 0.51 and Cho/Cr ratio of 0.83 ± 0.12. Occipital NAA/Cr ratio was 1.63 ± 0.03 and Cho/Cr ratio was 0.44 ± 0.03. Lactate was observed in four patients. MRS analysis of group 3 patients showed mean splenial NAA/Cr ratio 2.7 ± 0.14, Cho/Cr 0.72 ± 0.06. Occipital grey-white matter (OGWM) NAA/Cr ratio 1.19 ± 0.02 and Cho/Cr ratio was 0.65 ± 0.07 with lactate seen in 7 patients out of 14 patients. The mean GOS in this group was 2.07 ± 0.02.

NAA/Cr ratio was significantly reduced in all the patients as compared with controls. Splenium NAA/Cr ratio was affected early than OGWM NAA/Cr ratio but OGWM NAA/Cr ratio was found to be most valuable to differentiate patients of mild from moderate and severe head injury with p value of 0.002 and <0.001, respectively.