Introduction: Thalamic hemorrhages account for 10-15% of intracerebral hemorrhages (ICH) and have a variety of clinical manifestations. We investigated the relationship between injury to thalamus and intra-thalamic regions with level of consciousness and functional outcomes among CLEAR-III trial participants.
Methods: We analyzed diagnostic CT scans of 500 patients from CLEAR-III trial prior to randomization and identified the anatomic localization of ICH. Thalamic hemorrhages were further divided into 5 groups: dorsal, anterior, medial, central, and posterolateral. Blinded level of consciousness measures (Glasgow Coma Score (GCS) and question 1a of the National Institutes of Health Stroke Scale (NIHSS)) and stroke severity indices (including mortality and modified Rankin Scale (mRS)) were analyzed. We assessed association of each region with level of consciousness and stroke severity measures using multivariate logistic regression models. Major disability was defined as mRS 4-5. Outcome models were adjusted for ICH volume, IVH (intraventricular hemorrhage) volume, and age.
Results: Thalamic ICH was present in 332 patients (71%, 33 with primary IVH were excluded). Initial median GCS was similar in patients with (10, IQR 7-14) and without (10, IQR 6-14) thalamic lesion (P=0.72). At day 30 and 180, thalamic ICH was associated with increased mortality (OR 2.48, CI 0.92-6.63 and OR 2.03, CI 1.02-4.06), major disability (OR 2.44, CI 0.87-6.81 and OR 2.50, CI 1.08-5.75), and death or major disability (OR 2.57, CI 0.91-7.19 and OR 2.71, CI 1.37-5.38), respectively. Thalamic ICH involved medial, central, posterolateral, dorsal, and anterior regions in 51.8%, 48.8%, 48.6%, 56.8%, and 47% of cases, respectively. On day 7, only involvement of the medial thalamus was associated with decreased consciousness defined as GCS <=8 and NIHSS question 1a>=2 (P=0.024 and 0.043, respectively). While all thalamic regions were associated with worse mRS, none were associated with decreased consciousness at day 180.
Conclusion: Thalamic hemorrhages are associated with poor functional outcomes. Medial thalamus involvement affects consciousness acutely but not in the long term. The mechanism by which medial thalamus alters consciousness merits investigation.