Phantom pain after limb amputation

So we know that pain information is transported by lateral spinothalamic tract. The sensation from the peripheral receptors goes to medulla oblangata and then ascends to thalamus. Finally arrives to the primary sensory cortex in the postcentral gyrus. So the damage occurring in peripheral nerves and the nerve endings of this pathway by the amputation of limb, could result in change of the sensory integration. After a nerve is completely cut, researchers found out that the dorsal root ganglion cells activity and sensitivity according to the mechanical and chemical changes was increased. So the sensitization of the spinal cord can result in allodynia or hyperalgesia. Also at the nerve transection area, it is likely to a neuroma to occur. So the disorganized A and C nerve fibers (which are responsible for pain transport) at the neuroma eventually causes increased spontaneous potential activities. In addition to all of these mechanisms; researchers resulted that, patients who are having stump pain is more likely to have phantom pain. When we look at the psychological factors like all of the persistent pain types; stress, depression, and the lack of coping strategies can trigger phantom pain. 

Before the treatment, evaluation of phantom limb pain is important. First a detailed history should be taken. Then physical examination should be done. Some questionnaires also help us to understand the situation well. There are currently several types of treatment methods to treat phantom pain. Pharmacological treatments are commonly used which are non-steroid anti-inflammatory drugs, opoids and antidepressants. There are also some invasive treatments as well. When we take a look at the non invasive treatment methods which are currently used, there are studies that resulted that TENS application to the peripheral nerves on the residual limb could decrease the phantom pain symptoms. The mechanism is to generate sensation in the phantom limb by stimulating sensory afferents above the stump.

Mirror therapy is also proven to be efficient for phantom pain. A mirror is placed vertically on the table so that the mirror reflection of the patient’s intact hand is ‘superimposed ’ on the felt position of the phantom which is hidden behind the mirror. By this therapy, the patient can gain visual feedback and understand the proprioceptive representations of the amputated limb. Pain relief is seen because of the activation of the mirror neurons on the contralateral hemisphere. These neurons can be activated either by performing an action or even seeing a person doing that action. There are also other non-invasive treatments which were proven to be useful which are; biofeedback, acupuncture, hypnosis and relaxation techniques.

To conclude, there is still no exact underlying mechanism of phantom pain. Some of the treatments methods are seen to be efficient to reduce pain symptoms. More detailed studies are required for us to understand phantom pain more clearly.

Res. Asst. Ayşem Ecem ÖZDEMİR