Aim of the study: To document the acute magnetic resonance imaging (MRI) findings on the brain in cardiac arrest (CA) patients treated with therapeutic hypothermia (TH) and their relation to patients’ neurological outcome after 6 months.

Method: A prospective observational study with MRI was performed regardless the level of consciousness in 56 post-CA patientstreated with TH.

Results: MRI of the brain was obtained at a median of 4 days (3–13 days). At 6 months, 32/56 had survived with good neurological outcome. The MMSE was performed in 28/32 (88%) patients with a median of 28 (24–30). Acute ischemic lesions were found on diffusion-weighted MRI (DWI) in 34 (61%) patients and were more common in patients with poor outcome (p= 0.006). Acute ischemic injuries affected mostly gray matter, deep or cortical, and with or without involvement of the underlying white matter. Very few lesions were pure white matter lesions. Lesions in the occipital and temporal lobes, deep gray matter and cerebellum were most associated with poor outcome. Reductions in the apparent diffusion coefficient (ADC) were more common in patients with poor outcome, particularly in the occipital lobes. None of the patients with an ADC below 600×10−6mm2/s in any region survived to 6months.

Conclusions: In visual analyses of acute MRI, extensive acutelesions were found in the cortical regions and deep gray matter and were associated with poor outcome. In ADC measurements, low values were associated with poor outcome. Patients with good outcome showed a minor pathological pattern mainly in the frontal and parietal lobes.