Coma Health Article

Definition

Coma, from the Greek word koma, meaning deep sleep, is a state of extreme unresponsiveness, in which an individual exhibits no voluntary movement or behavior. Furthermore, in a deep coma, even painful stimuli (actions which, when performed on a healthy individual, result in reactions) are unable to cause any response, and normal reflexes may be lost.

Description

The important characteristics of the conscious state is defined by two fundamental elements: awareness and arousal.

Awareness allows one to receive and process all the information communicated by the five senses. Awareness has both psychological and physiological components. The psychological component refers to an individual's mind and mental processes. The physiological component refers to the functioning of an individual's brain, and the physical and chemical condition of the brain. Awareness is regulated by cortical areas within the cerebral hemispheres, the outermost layer of the brain.

Arousal is regulated solely by physiological functioning and consists of more primitive responsiveness to the world, as demonstrated by predictable reflex (involuntary) responses to stimuli. Arousal is maintained by the reticular activating system (RAS), a network of brain structures, including the brainstem, the medulla, and the thalamus, and nerve pathways that function together to produce and maintain arousal.

Causes and symptoms

Coma is the result of something that interferes with the functioning of the cerebral cortex and/or the functioning of the structures that comprise the RAS. Several conditions can result in coma. Anatomic causes of coma are those conditions that disrupt the brain structures responsible for consciousness, either at the level of the cerebral cortex or the brainstem, while metabolic causes of coma consist of those conditions that change the chemical environment of the brain, thereby adversely affecting function.

There are many metabolic causes of coma, including:

• a decrease in the delivery to the brain of substances necessary for appropriate brain functioning, such as oxygen, glucose (sugar), and sodium• the presence of certain substances such as drugs, alcohol, carbon dioxide, and ketones that disrupt the functioning of neurons
• changes in chemical levels in the brain caused by seizures

Diagnosis

History and examination form the cornerstone of diagnosis when an individual is in a coma. However, history must be obtained from family, friends, or emergency medical service personnel.

The Glasgow Coma Scale is a system of examining a comatose person. It evaluates the depth of the coma, tracks the person's progress, and predicts the ultimate outcome of the coma. The Glasgow Coma Scale assigns a different number of points for exam results in three different categories: opening the eyes, verbal response, and motor response (moving a part of the body). Fifteen is the largest possible number of total points, indicating the highest level of functioning, which would be demonstrated by individuals who spontaneously open their eyes, give appropriate answers to questions about their situations, and can carry out a command such as moving a specific limb when ordered. Three is the least possible number of total points, and would be given to a person for whom not even a painful stimulus is sufficient to provoke a response. In the middle are those people who may be able to respond, but who require an intense or painful stimulus, and whose response may demonstrate some degree of brain malfunctioning. When performed as part of the admission examination, a Glasgow score of three to five points often suggests that an individual has likely suffered fatal brain damage, while eight or more points indicates that the person's chances for recovery are good.

Expansion of the pupils and respiratory pattern are also important. Metabolic causes of coma are diagnosed from blood work and urinalysis to evaluate blood chemistry, drug screen, and blood cell abnormalities that may indicate infection. Anatomic causes of coma are diagnosed from computed tomography (CT) or magnetic resonance imaging (MRI) scans.