Chapter 4: Central Nervous System

Damage to the CNS

The brain controls limb movements and for reasons not entirely clear each side of the brain controls the opposite side of the body. The brain is supplied by blood from the heart and if a subject experiences a barotrauma where gas is propelled into the circulatory system and by chance is pumped by the heart to the brain. If it enters one of the arteries to the brain it will stop that side of the brain functioning. This will be evident by the subject being paralysed or having weakness or numbness or altered sensation down the opposite side of the body. This clearly is a serious crisis and requires immediate treatment by recompression. The special senses that is sight, smell, taste and hearing are all under the control of nerves which go directly to the brain.

The lower part of the brain and the spinal cord is an area where vital functions of control of breathing, heart rate, blood pressure etc are situated. If someone suffers a significant brain injury, then the final injury to occur to the brain before death is interruption of these vital functions. This is a sign of a severe and grave injury.

The spinal cord is involved in controlling movement and supplying the brain with sensations from all parts of the body. It is protected by a bony tube known as the vertebral column and to allow flexibility and movement this tube has joints at measured intervals. The spinal cord is thus protected and it takes severe force to put it in jeopardy. Spinal injuries result usually from falls, road traffic accidents and from blows to the head or blows above the shoulders. If one is presented with a subject with this kind of history or someone who is unconscious, it is essential that a spinal injury be assumed. The spinal cord is protected by immobilising the subject in a neutral position, applying a cervical collar and by carefully moving them in a way (log rolling) such that the spinal cord is not allowed to suffer any extravagant movements which may provoke further injury. (See Diagram 7 pages 57-58) A spinal injury is evident in the conscious subject by reduced function of the nerves below the level of injury e.g. if the back is broken the legs may be numb and do not work also the bladder will fill up and not empty properly. This latter situation is remedied by inserting a tube into the bladder through the normal urinary passage to allow it to drain properly. The nerves from the spinal cord supply the muscles in the limbs and the simplest way of testing these nerves is to test the power in each of the limbs. A reduction in power is a possible sign of spinal or nerve injury. If the weakness is on one side of the body, this raises a possibility of either a partial spinal injury or a brain injury. The nervous system is at risk from DCI due to the formation of bubbles in the blood supply to the nervous system.