Phantom Limb Sensations - Essay Example

When a sensory nerve is severed during amputation, a nodule called a neuroma will form near the end of the stump. These neuromas can be very sensitive to the touch and were thus believed to generate the mysterious signals. Although surgically removing the neuromas occasionally provided temporary relief, the phantom limb always returned." (Shreeve, 1993). Kandel has explained the grounds of phantom limb disorder, according to which it is important to consider the normal pathways involved in sensation.

These pathways involve both hemispheres of the brain containing a deep crack (gap) called the central sulcus. This crack is flanked on either side, by the help of two cortexes, the precentral gyrus (motor cortex), and the post central gyrus (somatosensory cortex). Incoming sensory afferents from the contra lateral (opposite) side of the body resulting in synapsing at the somatosensory cortex after finding its pathways through the thalamus. The somatosensory cortex (S1) is highly ordered in a roughly topographic fashion, containing a receptive field for every body part, with larger receptive fields devoted to areas that are more highly innervated such as the hands and lips.

The receptive fields are laid out in an ordered fashion along the length of S1, representing the entire body surface in an abstract map known as a homunculus. When a sensation travels from a particular location to the receptive field, the corresponding receptive field becomes active. Likewise, if an area of S1 is stimulated, the person will feel a sensation in the corresponding body part. (Kandel, 2005). Jensen, Krebs, Nielsen and Rasmussen (1983) have suggested that phantom limb can be divided into two categories as the term "phantom limb" refers to any painful or non-painful sensations occurring in the missing limb of the same individual.

Melzack in 1971 proposed Central theory as a physiological explanation of painful phantom limb, this theory also has been interpreted as a psychological explanation by Dawson and Arnold (1981) but as intended by the author it is considered as physiological in nature. It is stated that central theory credits such conscious processes that are based upon schematic representations with the passage of time along with the perception of phantom limb. These schematic representations come into existence from the peripheral sensory mechanisms.

Despite of the fact that both are interlinked with one another, both operate independently. Support for this schematic explanation has been provided in studies that show interference of locally anesthetizing peripheral nerves of an intact limb as result in the experience of phantom limb (Melzack, 1973). The main reason for the occurrence of Phantom limb is due to the fact that the brain no longer receives input from the anesthetized periphery, similar to an amputee's experience, so phantom limb occurs.

The two most common pain reactions following an amputation include phantom limb and residual limb pain. Phantom limb sensations, or non-painful sensations in the lost limb, are experienced almost immediately after an amputation. These sensations feel like the missing limb was actually present in its full representation by shape, length, and position in space. These sensations are