Back to top

How predictions are made

Doctors look at several indicators to predict the level of a patient’s recovery during the first few weeks and months after injury:

  • duration of coma
  • severity of coma in the first few hours after the injury (as measured by the Glasgow Coma Score)
  • duration of post-traumatic amnesia (PTA)
  • location and size of contusions and haemorrhages in the brain and severity of injuries to other body systems sustained at the time of the brain
  • Individuals in PTA are partially or fully awake, but are confused about the day and time, where they are, what is happening, and possibly who they They are likely to have problems with memory.

Precise predictions are difficult with brain injury, but some generalisations can be made:

  • the more severe the injury, the longer the recovery period, and the more impairment a survivor will have
  • recovery from diffuse axonal injury takes longer than recovery from focal contusions
  • recovery from TBI with hypoxic (lack of oxygen) injury (e.g. near drowning, strangulation or carbon monoxide poisoning) is less complete than without significant hypoxic injury
  • the need for surgery does not necessarily indicate a worse For example, a patient requiring the removal of a blood clot may recover as completely as one who never needs surgery.


The length of time a patient spends in a coma correlates to both post- traumatic amnesia (PTA) and recovery times. PTA is the gradual process of regaining consciousness after coma:

  • coma lasting seconds to minutes results in PTA that lasts hours to days; recovery occurs over days to weeks
  • coma that lasts hours to days results in PTA lasting days to weeks; recovery occurs over months
  • coma lasting weeks results in PTA that lasts months; recovery occurs over months to years.

General guide

Length of PTA is frequently used as a guide to the severity of brain injury. A commonly used interpretation of the scale involves the following:

Severity Category Mild Moderate Severe Very severe
Initial GCS 12-15 9-11 3-8 <1
Duration of PTA < 24 hours 1-7 days 1-4 weeks > 4 weeks


A general finding is that if the PTA stage lasts for more than one week ongoing cognitive problems can be expected.

It is important for the person and the family to be optimistic but realistic about recovery and to develop a better understanding of what is or isn’t possible. Some families with a loved one in hospital have likened this to hoping for the best while preparing for the worst.