In Comatose Survivors Of Cardiac Arrest, Dwi-Based Measurements Of Hypoxic-Ischemic Thalamic Injury Are Associated With Neurologic Prognosis.

Background: Hypoxic-ischemic brain injury caused by cardiac arrest often leaves survivors initially comatose, and with highly variable long-term neurologic outcomes that may be difficult to predict. As the thalamus plays an important role in arousal, we hypothesized that using diffusion-weighted MRI (DWI) to detect acute thalamic ischemic lesions may be helpful in predicting these patients’ long-term neurologic impairment. Because long-term outcome may be influenced by self-fulfilling prophecy bias (SFPB) due to early withdrawal of life sustaining treatment, we also investigated the association of thalamic lesion burden with arousal recovery, which is less influenced by SFPB. Methods: Images from 79 comatose post-arrest patients were analyzed retrospectively. A neuroradiologist measured lesion burdens as fractions of total thalamic volumes. Group related differences in thalamic lesion burden between patients with good vs. poor outcomes (6-month modified Rankin scale ≤4 or >4, respectively), and between patients who did vs. did not exhibit early arousal recovery (AR+, AR-), as manifested by eye opening in response to a noxious stimulus during the first 7-days post-arrest, were assessed by 2-tailed Wilcoxon exact test. Results: AR and good outcomes occurred in 38% (30/79) and 18% (14/79) of patients, respectively. Lesion burdens were significantly greater in AR- vs. AR+ patients (mean±SD 37±23% vs. 20±19%, p = 0.001), and greater in patients with poor vs. good outcomes (34±23% vs 11±13%, p < 0.001). All patients with lesion burdens over 56% were AR-, and all patients with lesion burdens over 39% had poor outcomes. Discussion: In comatose cardiac arrest survivors, the extent of early hypoxic-ischemic damage to the thalamus, as measured on early DWI, is related to long-term neurologic outcome. We also found that more severe thalamic burden was associated with failure to recover arousal in the first week. Our results are consistent with the thalamus’ key role in consciousness as a modulator of peripheral sensory input to the cortex. As comatose cardiac arrest patients’ outcomes are often difficult to predict based on clinical factors alone, the extent of thalamic injury on DWI may be helpful in treatment planning and goals-of-care assessment.