Phantom Limbs: Sensations When There Should be None Essay -- Biology E

Phantom Limbs: Sensations When There Should be None The phenomenon known as the phantom limb occurs in 95-100% of amputees. It can occur soon after amputation or occur years later. It is when patients feel sensations where the arm or leg used to be as if it were still there. These sensations can be either non-painful sensations or painful sensations, which are called phantom limb pain. These non-painful sensations are described as similar feels as if the limb were there such as warmth, tingling, itching, and movement. Phantom limb pain is described as stabbing, cramping, burning and shooting pain. Non-painful sensations usually occur soon after amputation and continue throughout life. It has been found that the strongest sites for phantom limbs are the thumb and index finger. Sometimes the knees or elbow are felt but rarely are the forearm, lower leg, upper thigh, and upper arm felt. (1). It has been found that it is not necessary to have had an amputation to experience the phantom limb phenomenon. It has been reported that after avulsion of the brachial plexus of the arm, even though no injury to the arm itself occurred, that there is extreme pain felt in the arm. For surgery, patients that receive an anesthetic block of the brachial plexus experience phantom arm. It also occurs in the legs when there is an anesthetic block of the lower body, and when there is a block of the spinal cord at the thoracic level, patients have experience phantom body. (2). Not only can one experience phantom limb due to an anesthetic block, but it has been reported that people born without limbs also experience it as well. Ronald Melzack, psychologist from McGill University in Montreal found that children born without arms or legs experi... ...uses these fibers to be excited which activates the primary afferent fibers which then discharges. These discharges ultimately cause the phantom sensations. Non-cortical theory believes that spontaneous activity at the edge of the amputation causes phantom limbs. (1). There is still a debate going on as to why phantom limbs occur. Only through further study of the nervous system can we hope to fully understand and hopefully one day stop its occurrence. Until then, we can only try to find ways to ease the pain of amputees, paraplegics and people who were born without limbs. References 1) http://hcs.harvard.edu/~husn/BRAIN/vol6/p21-25-PhantomLimbs.pdf 2) http://cognet.mit.edu/MITECS/Entry/melzack 3) http://www.findarticles.com/cf_0/m1511/n2_v19/20159526/p1/article.jhtml 4) http://www.sciencenet.org.uk/slup/CuttingEdge/Jun00/phantom.html