- Testing less than 6 hours of the loss of the last brainstem reflex
- Testing less than 24 hours of the loss of the last brainstem reflex, where aetiology primarily anoxic damage
- Patients with any neuromuscular disorders
- Prolonged fentanyl infusions
- Steroids given in space occupying lesions such as abscesses
- Aetiology primarily located to the brainstem or posterior fossa
- Hypothermia – a 24-hour observation period following rewarming to normothermia recommended
- Therapeutic decompressive craniectomy