Phantom Limb Pain

This post is provided by Ilya Shnaydman, Drexel University College of Medicine Class of 2013:

Phantom Limb is the sensation that an amputated limb is still attached to the body. It may occur after removal of other organs such as breast, eye, teeth, etc. It can even occur after a hysterectomy, where patients may suffer “phantom menstrual cramps.”  Approximately half of patients with phantom limb feel that they can move the missing body part, and the other half feel that the phantom limb is there, but “paralyzed” and frozen in space. These patients feel that if they could only relax the body part they would feel a great deal of relief. This is especially common if the body part is in a contracted, or fixed state prior to the amputation.

In the case of a paralyzed leg for example, the patient’s brain is sending signals telling the (paralyzed) limb to move, but since the leg can not move, the patient does not get the visual feedback of a moving limb. This leads to a “learned” pattern of paralysis. After an amputation, often this learned paralysis can remain with the patient feeling a clenched spasm of the missing extremity. The limb often feels as if it is burning, aching, in a painful position, or having electric-type pain. Phantom Limb Pain can occur anywhere from just after the amputation to even years later.

Our brains are hardwired from birth with sensations reaching the brain through predefined pathways. When you touch an object with your finger, those sensations reach the brain through complex pathways ending in a specialized area of the brain responsible for perceiving sensation. If that finger tip was amputated, and the remaining finger were to touch an object, the brain may perceive it as being the fingertip due to the similarity in the sensory pathways.

There are several theories for why phantom limb pain occurs. One theory is that the pain is caused by irritation of the severed nerve endings. The nerve endings can form a neuroma, or an abnormal growth of nerves. Some believe that the brain perceives these ‘nonsense’ stimulations as pain. This theory led to many patients undergoing revisional surgeries hoping to remove the inflamed nerve endings. Unfortunately in most cases it rarely helped.

Research at the National Institutes for Health (NIH) showed that the area of the brain responsible for interpreting sensation (primary somatosensory cortex) underwent reorganization after the loss of sensory input, as occurs after an amputation.  Phantom Limb Pain results when a conflict between signals received from the limb and a lack of visual input from the missing limb.

Stump Pain can result from other causes such as ischemia (lack of blood flow to the stump), infection, or pressure points over bony spurs. Phantom limb can only be diagnosed if all other causes of stump pain are ruled out.

The incidence of phantom limb pain varies from 50-85% depending on the diagnostic criteria used to define the syndrome. A minority of patients have such severe pain that it interferes with work, sleep and daily social life. The pain can be worsened by stress, anxiety and even weather changes. Phantom limb pain can be quite severe, leading to depression and even suicide.

Treatment

As with other forms of neuropathic pain, the treatment of Phantom Limb Pain has included pain medication, antidepressants, anticonvulsants, spinal cord stimulation, vibration therapy, acupuncture, hypnosis and biofeedback under the guidance of an experienced neurologist.

Biofeedback helps teach amputees with burning/tingling pain to unconsciously keep their phantom limb as warm as the intact limb. For cramping pain, the goal is to teach patients to prevent the onset of muscle tension leading to pain. Patients are hooked up to a biofeedback machine which consists of electrodes places on the body. The patient is then shown the relationship between temperature or muscular activity and the onset of phantom pain. Once they are convinced of this relationship, they undergo various exercises to increase their temperature/muscle tension awareness. After some time patients are able to sense these changes and control them effectively.

Some studies have shown that calcitonin (a hormone naturally occurring in the body that regulated calcium metabolism) and ketamine (an anesthetic drug) are effective in treating Phantom Limb Pain. If all other methods have failed, surgical intervention may be indicated.

Mirror Box Therapy

A novel way of relieving the clenched pain that patients with phantom limb face was created by  Vilayanur S. Ramachandran. He proposed placing a mirror between the patient’s two limbs, tricking the eyes into seeing that the amputated limb is actually still there.

The ‘phantom limb’ is placed behind the mirror, and the normal limb on the other side. The patient then makes the same clenched position with their normal limb. This brings the visual impression that the phantom limb is still there. By relaxing their normal limb, patients can trick their brain into relieving the pain of the phantom limb. This shows how the theory of  ‘learned paralysis’ applies to phantom limb and how it can be overcome with a simple visual aid.

If you have any questions about this condition, please comment below!

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