The radiological interpretation of possible microbleeds after moderate or severe traumatic brain injury: a longitudinal study

Abstract

Introduction: In order to augment the certainty of the radiological interpretation of "possible microbleeds" after traumatic brain injury (TBI), we assessed their longitudinal evolution on 3-T SWI in patients with moderate/severe TBI.

Methods: Standardized 3-T SWI and T1-weighted imaging were obtained 3 and 26 weeks after TBI in 31 patients. Their microbleeds were computer-aided detected and classified by a neuroradiologist as no, possible, or definite at baseline and follow-up, separately (single-scan evaluation). Thereafter, the classifications were re-evaluated after comparison between the time-points (post-comparison evaluation). We selected the possible microbleeds at baseline at single-scan evaluation and recorded their post-comparison classification at follow-up.

Results: Of the 1038 microbleeds at baseline, 173 were possible microbleeds. Of these, 53.8% corresponded to no microbleed at follow-up. At follow-up, 30.6% were possible and 15.6% were definite. Of the 120 differences between baseline and follow-up, 10% showed evidence of a pathophysiological change over time. Proximity to extra-axial injury and proximity to definite microbleeds were independently predictive of becoming a definite microbleed at follow-up. The reclassification level differed between anatomical locations.

Conclusions: Our findings support disregarding possible microbleeds in the absence of clinical consequences. In selected cases, however, a follow-up SWI-scan could be considered to exclude evolution into a definite microbleed.

Keywords: Brain injuries; Cerebral hemorrhage; Diffuse axonal injury,; Longitudinal studies; Magnetic resonance imaging; Traumatic.

Fig. 1

Overview of study procedure. TBI traumatic brain injury, t1 3 (2–5) weeks after TBI, t2 26 (25–28) weeks after TBI, CAD computer-aided detection

Fig. 2

Anatomical distribution of possible microbleeds at t1 corresponding to no, possible, and definite microbleeds at t2. The x-axis shows the anatomical regions in descending order of number of possible microbleeds at t1. Thalamus is not on the x-axis, as it contained no possible microbleeds at t1. The y-axis shows per region the percentage of possible microbleeds at t1 that was classified as definite (circle), possible (square), or no (cross) microbleed at t2. t1: 3 (2–5) weeks after TBI, t2: 26 (25–28) weeks after TBI, def: definite microbleed, pos: possible microbleed, not: no microbleed

Fig. 3

Examples of possible microbleeds at t1 classified differently at t2. a Pathophysiological difference (disappearance); b possible pathophysiological difference, with slightly decreased signal intensity and increased blooming at t2, which may be caused by a technical difference between the scans or by a pathophysiological change; c equivocal classification, especially at t1 this configuration can as well be classified as a possible microbleed as as a continuation of the blood vessel medial to it; d misinterpreted otherwise: this subarachnoid blood was mistaken for a possible microbleed at t1; e misregistration or missegmentation: at both time-points, this possible microbleed was segmented too small; the segmentations did not overlap, resulting in a false mismatch in the automatic comparison step; f artifact hampering the interpretation (susceptibility at air-tissue interface); g artifact precluding evaluation at t2 (susceptibility at air-tissue interface). Images are axial images. Arrows point to the microbleeds discussed. In e, the automatic segmentation resulted in the closed curves. t1: 3 (2–5) weeks after TBI, t2: 26 (25–28) weeks after TBI