Prognosis

The clinical examination in coma can help in estimating the chances of recovery. Absent or stereotyped motor responses or absent pupillary responses are some of the clinical signs heralding bad outcome.

The EEG has also shown its efficacy in predicting outcome after anoxic or traumatic brain damage [for review see e.g., 1, 2]. Flat (or isoelectric) and burst-suppression EEG predict bad outcome.

The absence of somatosensory evoked potentials (SEPs) is a potent indicator of death or irreversible vegetative state in comatose patients. In contrast, an intact mismatch negativity (MMN; a component which appears in auditory oddball paradigms) has recently been suggested to have a strong positive predictive value – that is, it’s presence predicts an outcome better than death or vegetative state [3-5].

Once the patient has evolved to a vegetative state prediction of outcome becomes more difficult but MRI studies are ongoing and promising [6].

Three months following a non-traumatic (anoxic) brain damage and 12 months after traumatic injury, the condition of vegetative state patients may be regarded as irreversible or ‘permanent’ [7].

In minimally conscious patients, chances of recovery are better than in the vegetative state.

 

References

1.         Young, G.B., Wang, J.T., and Connolly, J.F. (2004). Prognostic determination in anoxic-ischemic and traumatic encephalopathies. J Clin Neurophysiol  21, 379-390.
2.         Zandbergen, E.G., et al. (1998). Systematic review of early prediction of poor outcome in anoxic- ischaemic coma. Lancet  352, 1808-1812.
3.         Fischer, C., Luaute, J., Adeleine, P., and Morlet, D. (2004). Predictive value of sensory and cognitive evoked potentials for awakening from coma. Neurology  63, 669-673.
4.         Fischer, C., et al. (2006). Improved prediction of awakening or nonawakening from severe anoxic coma using tree-based classification analysis. Critical Care Medicine  34, 1520-1524.
5.         Naccache, L., et al. (2005). Auditory mismatch negativity is a good predictor of awakening in comatose patients: a fast and reliable procedure. Clin Neurophysiol  116, 988-989.
6.         Galanaud, D., Naccache, L., and Puybasset, L. (2007). Exploring impaired consciousness: the MRI approach. Curr Opin Neurol  20, 627-631.

7.         The Multi-Society Task Force on PVS (1994). Medical aspects of the persistent vegetative state (1). N. Engl. J. Med.  330, 1499-1508.