Locations and clinical significance of non-hemorrhagic brain lesions in diffuse axonal injuries

Abstract

Objective: Detection of focal non-hemorrhagic lesion (NHL) has become more efficient in diffuse axonal injury (DAI) patients using an MRI. The aims of this study are to find out the radiological distribution, progress of NHL and its clinical significance.

Methods: Between September 2005 and October 2011, 32 individuals with NHLs on brain MRI were enrolled. NHLs were classified by brain location into 4 major districts and 13 detailed locations including cortical and subcortical, corpus callosum, deep nuclei and adjacent area, and brainstem. The severity of NHL was scored from grades 1 to 4, according to the number of districts involved. Fourteen patients with NHL were available for MRI follow-up and an investigation of the changes was conducted.

Results: Thirty-two patients had 59 NHLs. The most common district of NHL was cortical and subcortical area; 15 patients had 20 NHSs. However the most common specific location was the splenium of the corpus callosum; 14 patients had 14 lesions. The more lesions patients had, the lower the GCS, however, this was not a statistically meaningful difference. On follow-up MRI in 14 patients, out of 24 lesions, 13 NHLs resolved, 5 showed cystic change, and 6 showed atrophic changes.

Conclusion: NHLs were located most commonly in the splenium and occur frequently in the thalamus and the mesial temporal lobe. Because most NHS occur concomitantly with hemorrhagic lesions, it was difficult to determine their effects on prognosis. Since most NHLs resolve completely, they are probably less significant to prognosis than hemorrhagic lesions.

Keywords: Corpus callosum; Diffuse axonal injury; Magnetic resonance imaging; Non-hemorrhagic; Traumatic brain injury.

Fig. 1

A non-hemorrhagic lesion of the corpus callosum. A 21-year-old male was admitted due to a bicycle accident. Upon admission his Glasgow coma scale score was 6 points. MRI shows a non-hemorrhagic lesion (arrows) at the splenium of the corpus callosum. Non-hemorrhagic lesions show high signal intensity at T2W1 (A) and FLAIR (B), but dark signals cannot be seen on SWI (C).

Fig. 2

A non-hemorrhagic lesion of the thalamus area. A 57-year-old male was admitted due to a pedestrian car accident, with a Glasgow coma scale of 7 on admission. MRI shows a non-hemorrhagic lesion at the right thalamus (arrow). Non-hemorrhagic lesions show high signal intensity at T2W1 (A) and FLAIR (B), but a dark signal cannot be seen on SWI (C). However, at one month follow-up, the previous high signal at T2W1 (D), FLAIR (E) is not seen and SWI (F) still showed no dark signals.

Fig. 3

A non-hemorrhagic lesion of the internal capsule. A 45-year-old male fell and was admitted to the emergency room. His initial Glasgow coma scale was 4 points and he was in a semi-coma. MRI shows a non-hemorrhagic lesion in the left internal capsule posterior limb at T2W1 (arrow, A) and FLAIR (B) with no dark signal at SWI (C). Hemorrhagic lesions are also noted in the corpus callosum, thalamus, brainstem and cerebellum.

Fig. 4

Non-hemorrhagic lesions of the brainstem and hippocampus. A 35-year-old woman was admitted in a semicomatose state after a fall. T2WI (A) and FLAIR (B) shows a bright dot on the left crus cerebri of the midbrain (arrows) and SWI (C) does not show low signal intensity. Another non-hemorrhagic lesion is suspected on the left hippocampus. FLAIR (B) shows a bright signal intensity lesion from the left pes hippocampus to the body of the hippocampus, which is not prominent on T2WI (A) except slightly swollen pes hippocampus. Several petechial hemorrhagic lesions are also noted in the right temporal subcortical area and left mesial temporal area.

Fig. 5

Cystic changes of non-hemorrhagic lesions on the corpus callosum. A 22-year-old man with a splenial non-hemorrhagic lesion (arrow, A : T2WI, B : FLAIR, C : SWI). Follow-up images in three months show a small cyst on the same area of splenium (D : T2WI, E : FLAIR, F : SWI).

Fig. 6

Atrophy of non-hemorrhagic lesion on brainstem. A 34-year-old man with a lesion on the right dorso-ventral midbrain. Follow-up images at two years show no abnormal signal in the midbrain, however, the volume of the midbrain seems to be smaller than the initial images especially on the right side (A : initial T2WI, B : initial FLAIR, C : 2-year follow-up T2WI, D : 2-year follow-up FLAIR).