Clinical Relevance of 'Cap' and 'Track' Development after Recent Small Subcortical Infarct

Abstract

Objective: After a recent small subcortical infarct (RSSI), some patients develop perilesional or remote hyperintensities ('caps/tracks') to the index infarct on T2/FLAIR MRI. However, their clinical relevance remains unclear. We investigated the clinicoradiological correlates of 'caps/tracks', and their impact on long-term outcomes following RSSI.

Methods: We identified participants with lacunar stroke and MRI-confirmed RSSI from 3 prospective studies. At baseline, we collected risk factors, RSSI characteristics, small vessel disease (SVD) features, and microstructural integrity on diffusion imaging. Over 1-year, we repeated MRI and recorded 'caps/tracks' blinded to other data. We evaluated predictors of 'caps/tracks', and their association with 1-year functional (modified Rankin Scale score ≥2), mobility (Timed Up-and-Go), cognitive outcomes (Montreal Cognitive Assessment [MoCA] score <26), and recurrent cerebrovascular events (stroke/transient ischemic attack/incident infarct) using multivariable regression.

Results: Among 185 participants, 93 (50.3%) developed 'caps/tracks' first detected at median 198 days after stroke. 'Caps/tracks' were independently predicted by baseline factors: larger RSSI, RSSI located in white matter, higher SVD score, and higher mean diffusivity in normal-appearing white matter (odds ratio [OR] [95% confidence interval {CI}], 1.15 [1.07-1.25], 6.01 [2.80-13.57], 1.77 [1.31-2.44], 1.42 [1.01-2.03]). At 1 year, 'cap/track' formation was associated with worse functional outcome (OR: 3.17, 95% CI: 1.28-8.22), slower gait speed (β: 0.13, 95% CI: 0.01-0.25), and recurrent cerebrovascular events (hazard ratio [HR]: 2.05, 95% CI: 1.05-4.02), but not with cognitive impairment.

Interpretation: 'Caps/tracks' after RSSI are associated with worse clinical outcomes, and may reflect vulnerability to progressive SVD-related injury. Reducing 'caps/tracks' may offer early efficacy markers in trials aiming to improve outcome after lacunar stroke. ANN NEUROL 2025;97:942-955.

FIGURE 1

Example of ‘caps’ and ‘tracks’ following recent small subcortical infarct (RSSI) at the infero‐superior direction. The first column represents the baseline FLAIR MRI images performed 78 days after stroke onset, the second and third columns represent the 1‐year follow‐up FLAIR MRI images performed 476 days after stroke onset. (A, B) The index RSSI (arrowheads) is visible in the right centrum semiovale on baseline and 1‐year MRI. (C–E) On the MRI slice superior to the index RSSI, there is no abnormality at baseline. At 1 year, new ‘caps’ appear as hyperintensities in 2 axial slices superior to the index RSSI (arrows and augmented squares). (I, J) In the sagittal plane, the ‘cap’ is visible as a trajectory ascending from the index RSSI (arrow). (F–H) On the MRI slice inferior to the index RSSI, there is no abnormality at baseline. At 1 year, new ‘tracks’ appear as hyperintensities in 2 axial slices inferior to the index RSSI (arrows and augmented squares). (K, L) In the coronal plane, the ‘track’ is visible as a trajectory descending from the index RSSI toward the internal capsule and cerebral peduncle, following the corticospinal tract (arrows).

FIGURE 2

Different types of ‘tracks’ depending on the location of recent small subcortical infarct (RSSI). (Top row, A) In a patient with RSSI in the right pons (arrowheads), a ‘track’ develops and is visible on the 6‐month and 1‐year FLAIR scans as a trajectory descending from the index lesion toward the medulla (squares). (Middle row, B) In a patient with RSSI in the peripheral right coronal radiata (arrowheads), a ‘track’ develops and is visible on the 6‐month and 1‐year FLAIR scans, extending in the anterior intrahemispheric direction (squares). (Bottom row, C) In a patient with RSSI close to the corpus callosum (arrowheads), a ‘track’ develops and is visible on the 6‐month and 1‐year FLAIR scans. The ‘track’ traverses from the right to left hemisphere across the corpus callosum (squares). Note that the visibility of ‘tracks’ increases over time.

Figure 3

Flowchart of participant selection. RSSI, recent small subcortical infarct.

Figure 4

Distribution timeline of first detection of ‘caps/tracks’ on MRI across all visits.

Figure 5

Illustration of the results of mediation analysis. The baseline summary small vessel disease (SVD) score is the exposure variable (X), the ‘cap/track’ formation is the mediator (M), and 1‐year functional impairment (modified Rankin Scale score ≥ 2) is the outcome variable (Y). Total effect = direct effect + indirect effect. The proportion of mediation effect is estimated by dividing the indirect effect by the total effect. The multivariable model included age, sex, National Institutes of Health Stroke Scale, index infarct diameter, and recurrent cerebrovascular event as covariates.