1. suppression of sensation, usually in the lower part of the body, by the injection of a local anaesthetic into the subarachnoid space. A very fine needle is used to reduce the amount of cerebrospinal fluid that escapes as the needle penetrates the dura. The technique has complications (headache, sepsis, paraplegia). The injection site for spinal anaesthetics is most often in the lumbar region of the vertebral column, the needle being inserted between the vertebrae (anywhere between the second and fifth). The extent of the area anaesthetized depends upon the amount and strength of local anaesthetic injected. Dilute local anaesthetic solutions are used when the sensory nerves are targeted rather than the motor nerves. Spinal anaesthesia is useful in patients whose condition makes them unsuitable for a general anaesthetic, perhaps because of chest infection; to reduce the requirements for general anaesthetic drugs; or in circumstances where a skilled anaesthetist is not readily available to administer a general anaesthetic.
2. loss of sensation in part of the body as a result of injury or disease to the spinal cord. The area of the body affected depends upon the site of the lesion: the lower it is in the cord the less the sensory disability.
Medical dictionary. 2011.