Hypoxic and anoxic brain injury: recovery and rehabilitation

The brain needs a continuous supply of oxygen to use glucose, its main fuel. Headway explains that a complete interruption is called anoxia and a partial supply that is inadequate is called hypoxia, and that in practice the terms are used interchangeably. Causes include cardiac or respiratory arrest, very low blood pressure from blood loss or heart failure, suffocation, choking, strangulation, a very severe asthma attack, complications of anaesthesia, near drowning, smoke or carbon monoxide inhalation, poisoning, drug overdose and electric shock.

Mild oxygen lack causes concentration, attention, coordination and short-term memory problems, headache, dizziness, light-headedness and sometimes restricted visual fields. Severe lack causes confusion, agitation, drowsiness, blue discolouration, brief limb jerks called myoclonus, seizures and, if prolonged, loss of consciousness and coma.

Nerve cells have high energy needs and are very sensitive to oxygen lack. Headway says the cerebral cortex, particularly the parietal and occipital lobes, the hippocampus, important for memory, the basal ganglia and the cerebellum, both involved in movement control, are especially vulnerable. After cardiac arrest, reduced blood flow can also damage the watershed zones at the borders of the main arterial territories.

This pattern explains the typical picture: memory difficulty, visual-perceptual problems, movement disorders such as myoclonus or tremor and balance or coordination problems. Headway notes that in anoxic injury the nerve cell bodies themselves are vulnerable and damage is irreparable, whereas in traumatic injury axonal damage is prominent and the brain can often create alternative connections.

Diagnosis is usually clear from the circumstances and the person's condition on arrival. Treatment aims to restore normal heartbeat, blood pressure and oxygen supply, and people who suffer a serious episode are usually admitted to intensive care, ventilated and treated for seizures, ideally in a specialist neurosciences centre. Some centres use medically induced cooling, which Headway describes as controversial and with its own risks, such as infection and clotting problems.

Outcome is difficult to predict. Headway lists age, the duration of the anoxic episode, the duration of coma, pupil reaction, EEG, CT or MRI imaging and somatosensory evoked potentials as helping to predict outcome. It says only about 12% of patients who have been comatose for more than six hours after a cardiac arrest make a good recovery, and notes that medically induced coma does not indicate outcome. Early improvement within the first month suggests a more favourable course.

Headway says the principles of rehabilitation after cerebral anoxia are the same as for other acquired brain injury, with an integrated team offering a range of specialist skills to help each person achieve the best possible outcome, and that adequate rehabilitation from the earliest possible stage is vital. Older people can benefit from rehabilitation, even though outcomes overall are less favourable above the age of 50.

Teams include clinical neuropsychologists, occupational therapists, speech and language therapists, physiotherapists, nurses and social workers. NICE guidance on neurological rehabilitation expects an early holistic needs assessment, agreed goals, a single point of contact and a written plan, delivered in inpatient, outpatient or community settings.

Memory impairment is typical, along with slowed information processing, executive and attention problems, mood changes and fatigue. Movement problems can range from poor coordination to myoclonus. Rehabilitation works on each domain: cognitive rehabilitation with compensatory aids, physiotherapy for movement and balance, occupational therapy for daily living and equipment, and psychological support for mood and adjustment.

Families often find the lack of insight, the memory difficulty and the emotional shifts the hardest part, and neuropsychology and Headway services provide guidance. Mental capacity may need formal assessment where decisions about care or finances are affected.

Headway says the most rapid recovery is usually in the first six months, that by about one year the likely long-term outcome will be clearer, and that improvement may continue for several years in smaller steps. It recommends waiting around a year before important decisions about the future. NICE asks teams to plan for review points and agree how people can return to services if needs change.

Driving, work and returning to usual roles are addressed through the DVLA process, vocational rehabilitation and workplace adjustment, as described in our guides for those topics.