Predicting the Outcome

Because people with HAI have often suffered extensive damage, complete recovery is not assured. In fact, predicting the outcome of HAI is a bit like estimating how high a rocket will go. There are some general factors that are helpful in making initial forecasts, but the actual course of the rocket is also dependent upon real-world conditions and many unforeseeable variables.

Studies that have been done suggest that recovery may be more limited than in cases where a person has suffered a traumatic brain injury of comparable severity. Nonetheless, there are some clues that can clearly offer a bit of guidance in judging the likelihood of at least a partial recovery. These include:
Length of coma. As you might expect, the longer a person is in a coma, the less promising the outcome, although individual cases can vary dramatically from the norm. One study suggested that if a coma lasts less than 12 hours, there is likely to be little long-term damage. Another study indicated that 21 percent of HIA patients who remained in a coma for four weeks or less experienced a good recovery, while the recovery for others was poor.

Many patients come out of a coma but remain in what is called a persistent vegetative state, a sort of wakeful unresponsiveness in which some brain functions continue to operate but with no apparent consciousness. Some doctors believe that if the persistent vegetative state in a patient with HAI continues for more than three months, there is virtually no chance of further recovery.

Visual cues. If both eyes have fixed or dilated pupils, the prognosis is generally poor. Since this can indicate significant damage to the brain-stem, the area of the brain responsible for regulating such basic functions as breathing, the outcome is not promising. Neurologists can also conduct tests to measure some standard eye-movement responses to determine what kind of damage has been suffered.

Age. Some studies suggest that patients younger than 25 have a better rate of recovery than those who are older.

Brain imaging tests, such as MRI or CT scans. Acute brain damage that has occurred in the immediate past does not typically show up on this type of scan. However, imaging tests conducted several months down the line may indicate the atrophy or loss of some brain matter.

Electroencephalography (EEG) and evoked potentials (EPs). An EEG that reveals continued cortical activity is a positive sign. An EP, which charts electrical activity arising in response to outside stimuli, can also give some indication of the state of the brain after HAI.