Coma
- Total absence of awareness of self and the environment
- Light coma - some semi-purposeful movements to painful stimuli
- Deep coma - limited physiological responses
Pathophysiology of Coma
- Hemisphere disease (structural)
- Brain Stem Disease (structural)
- Metabolic Brain Disease
Herniation Syndromes associated with loss of consciousness:
- Uncal (unilateral transtentorial) herniation
- Central transtentorial herniation
- Tonsillar herniation
Localizing the injury and differentiating from other causes of stupor or coma, examine:
- size and reactivity of pupils
- pupillary reflex is most resistant to metabolic insult
- abnormal pupil response is first sign of herniation
- eye movements and reflex responses - vestibulo-ocular reflex by cold caloric stimulation
- motor examination
- Decorticate posturing - flexed arms to chest (loss of higher motor control, red nucleus intact)
- Decerebrate posturing - extensor tone (lesion at red nucleus, reticulospinal and vestibulospinal tract intact)
- Flaccid Hypotonic immobility (Diffuse Brainstem damage)
- breathing patterns
- Cheyne-Stokes respiration
- regular crescendo/decrescendo pattern of periodic breathing
- bilateral dysfunction of cerebral hemispheres or diencephalon
- metabolic brain dysfunction
- Central neurogenic hyperventilation
- sustained rapid deep breathing
- rare, low midbrain to middle third of pons
- Apneustic Breathing
- pause at full inspiration or end-inspiratory pauses (2-3 secs)
- rare, mid or low pons, esp. pontine infarction
- Ataxic breathing
- irregular, deep and shallow breaths occur randomly
- disruption of respiratory rhythm in medulla
Glasgow Coma Scale
- Three components used to score level of coma:
- Eye Opening (4 points) - 1=none, 2=to pain, 3=to speech, 4=spontaneous
- Verbal response (5 points) - 1=none, 2=incomprehensible sounds, 3=inappropriate words, 4=confused speech, 5=oriented
- Best motor response (6 points) - 1=none, 2=extension, 3=abnormal flexion, 4=withdraws, 5=localizes, 6=obeys