ABSTRACT
The term coma is used to refer to patients whose eyes are permanently closed and who cannot be awakened nor are in a functioning state.(1) According to Zasler,(2) coma is a state in which there is no meaningful response. Comatose patients normally maintain their eyes closed without evidence of opening spontaneously or to external stimuli, do not follow instructions, do not show goal-directed or voluntary conduct, do not speak and cannot sustain looking or tracking movements of more than a 45˚ angle. Excluded are secondary neurobehavioral signs and symptoms in coma that have been treated pharmacologically with sedatives. The definition of coma in terms of cerebral functioning refers to a state of acute brain failure not strictly related to any particular cerebral substratum or specific anatomical level of lesion. Coma normally occurs when broad areas in the upper and lower brain stems, or cerebral hemispheres, or simultaneously in the cerebral hemispheres and brain stem are damaged. The most frequent causes of coma are diffuse axonal pathology, hypoxia and secondary lesions which affect the brainstem (Figures 6.1, 6.2, 6.3, 6.4).
