The central nervous system consists of the brain and the spinal cord. The brain is protected within the skull, and the spinal cord protected within the vertebrae which both are enclosed within the meninges.

The brain is divided into the following regions:

The ventricles are the spaces in the brain and the spinal cord where cerebrospinal fluid is produced and circulated.

The cerebral hemispheres form the largest part of the brain, and can be further subdivided into four lobes; frontal, parietal, occipital and temporal. The anterior cerebral artery, middle cerebral artery and posterior cerebral artery supply the cerebral hemispheres. Obstruction or occlusion of blood flow through a cerebral artery causes ischaemic damage to the cerebral tissue that the artery supplies. Clinically this manifests as an ‘ischaemic’ stroke resulting in a focal neurological deficit.

A coma can be defined as a state in which the patient is totally unaware of themselves or the external surroundings. The patient is unable to respond to external stimulation. A coma usually results from global impairment of the cerebral hemispheres and/or the reticular activating system.