Clinical diagnosis

An accurate and reliable evaluation of the level and content of consciousness in severely brain-damaged patients is of paramount importance for their appropriate management. Progress in medicine has increased the number of patients who survive severe acute brain damage. Although the majority of these patients recover from coma within the first days after the insult, some permanently lose all brainstem functions (brain death), while others evolve to a state of ‘wakeful unawareness’ (vegetative state; VS). Those who recover, typically progress through different stages before fully or partially recovering consciousness (minimally conscious state; MCS).

Bedside evaluation of residual brain function in severely brain-damaged patients is difficult because motor responses may be very limited or inconsistent [1,2]. In addition, consciousness is not an all-or-none phenomenon [3] and its clinical assessment relies on inferences made from observed responses to external stimuli at the time of the examination [4].

Consciousness is a multifaceted concept that has two major components: awareness of environment and of self (i.e., content of consciousness) and wakefulness (i.e., level of consciousness) (figure).

The Glasgow Coma Scale is the most used clinical evaluation scale in acute coma. In chronic disorders of consciousness, other standardized clinical testing by means of validated scales such as the Coma Recovery Scale or the Sensory Modality Assessment and Rehabilitation Technique (SMART) is recommended.

 

consciousness
Figure. Graphical representation of the two components of consciousness (arousal and awareness) and their alterations in coma, the vegetative state, the minimally conscious state and in the locked-in syndrome. Taken from Laureys et al., Lancet Neurology, 2004.

 

References

1.         Majerus, S., Gill-Thwaites, H., Andrews, K., and Laureys, S. (2005). Behavioral evaluation of consciousness in severe brain damage. Prog Brain Res  150, 397-413.
2.         Giacino, J.T. (1997). Disorders of consciousness: differential diagnosis and neuropathologic features. Semin. Neurol.  17, 105-111.
3.         Wade, D.T. and Johnston, C. (1999). The permanent vegetative state: practical guidance on diagnosis and management. B.M.J.  319, 841-844.
4.         Bernat, J.L. (1992). The boundaries of the persistent vegetative state. J Clin Ethics  3, 176-180.