Hypoxic-ischaemic brain injury: imaging and neurophysiology abnormalities related to outcome

The outcome for patients with hypoxic-ischaemic brain injury (HIBI) is often poor. It is important to establish an accurate prognosis as soon as possible after the insult to guide management. Clinical assessment is not reliable and ancillary investigations, particularly imaging and EEG, are needed to understand the severity of brain injury and the likely outcome.

We undertook a retrospective study of 39 patients on an intensive therapy unit (ITU) with HIBI who were referred for MRI. The patients were seen consecutively >57 months. HIBI was due to a variety of insults causing cardiac arrest, hypoperfusion or isolated hypoxia.

The outcome was poor, 29 patients died, 7 were left severely disabled and only 3 made a good recovery. Characteristic imaging changes were seen on MRI. These included extensive changes in the cortex and the deep grey matter present on diffusion-weighted imaging (DWI) and T2-weighted imaging within 6 days of the insult. In other patients, different patterns of involvement of the cortex and basal ganglia occurred. There was no significant difference in the outcome or imaging appearances according to aetiology. A poor prognosis was consistently associated with a non- or poorly responsive EEG rhythm and the presence of periodic generalized phenomena with a very low-voltage background activity.

In this retrospective study of patients with HIBI, MRI and EEG provided valuable information concerning prognosis.