# Progressive Evaluation of Ischemic Occlusion in a Macaque Monkey with Sudden Exacerbation of Infarction During Acute Stroke: A Case Report

## TL;DR

This study uses MRI to track how a stroke worsens in a macaque monkey, showing how blood flow and brain function change over time.

## Contribution

The study provides new insights into sudden infarction progression and the role of collateral circulation in acute stroke using a non-human primate model.

## Key findings

- A sudden increase in infarction volume was observed after the hyper-acute phase but before 48 hours post-stroke.
- Functional connectivity in key brain regions declined immediately after stroke and showed fluctuating changes over time.
- Poor collateral circulation may contribute to sudden worsening of brain damage during acute stroke.

## Abstract

Sudden deterioration of ischemic lesions during acute stroke is sometimes observed in clinical practice but is not well understood. In this study, multiparameter MRI was used to evaluate the alterations of cerebral blood flow (CBF), brain function, and brain structure in a macaque monkey at multiple time points following a stroke. A substantial increase in infarction occurred after the hyper-acute phase but before 48 h post-stroke. Key brain regions responsible for movement and sensation showed reduced functional activity. Poor collateral circulation to the affected area may contribute to the sudden worsening of brain damage during acute stroke. Also, these findings highlight the critical role of cerebral blood flow and functional connectivity measurements in understanding the evolution of ischemic lesions following stroke onset.

Early neurological deterioration is associated with poor functional outcomes in stroke patients, but the underlying mechanisms remain unclear. This study aims to understand the progression of stroke-related brain damage using a rhesus monkey model with ischemic occlusion. Multiparameter MRI was used to monitor the progressive evolution of the brain lesion following stroke. Resting-state functional MRI, dynamic susceptibility contrast perfusion MRI, diffusion tensor imaging, and T1- and T2-weighted scans were acquired prior to surgery and at 4–6 h, 48 h, and 96 h following the stroke. The results revealed a sudden increase in infarction volume after the hyper-acute phase but before 48 h on diffusion-weighted imaging (DWI), with a slight extension by 96 h. Lower relative cerebral blood flow (CBF) and time to maximum (Tmax) prior to the stroke, along with a progressive decrease post-stroke, were observed when compared to other stroke monkeys in the same cohort. Functional connectivity (FC) in the ipsilesional secondary somatosensory cortex (S2) and primary motor cortex (M1) exhibited an immediate decline on Day 0 compared to baseline and followed by a slight increase on Day 2 and a further decrease on Day 4. These findings provide valuable insights into infarction progression, emphasizing the critical role of collateral circulation and its impact on early neurological deterioration during acute stroke.