Imagine you found yourself awake in a hospital bed. Confused, you try to remember what happened and why you are here. The last thing you can recall is you and your car spinning like a top… while overtaking a truck at a very high speed on a narrow highway. Relieved that you are still alive after a horrible accident, you try to wipe the sweat on your face with your right arm without looking. You felt very painful and unnatural to move your hand but thinking its just muscle pain due to the accident; you didn’t give much attention. Funnily you didn’t felt your hand at all on your face. And when you took a glance at your hand… there was nothing there. Yet you could still feel the sensations of your hand still being there,… or worse, twisting pain in a nonexisting hand.
This is precisely how an amputee might feel the phantom pain of its lost arm. Earlier doctors used to believe that this is a psychological phenomenon. A ghost of the past. The contradiction between the physical body and the mental image of the same. But now experts have triangulated the origin of the phantom pain as a physiological problem, arising from the neurons within the spinal cord and the brain. Some just feel the sensations of a nonexistent arm still being there. But that’s phantom limb sensations and is not the worst condition in this case. Phantom pain is a far wretched condition where you do not just feel the amputated arm, but also sense it as if its twisting and bending in an uncontrollable and abnormal state. And the pain which arises from it is something we can hardly imagine even if we try to put ourselves in their shoes.
There are many theories and pieces of evidence that point towards the neurological basis of phantom pain. Historically it was thought that traumatically injured neurons or neuromas were the origins of the phantom pain. But that couldn’t be the only reason as even those with limb deficiencies from birth could sometimes experience phantom pain, suggesting the existence of phantom pain origins at the upper levels of the neuraxis. Spinal cord damage is also considered to be one of the reasons for the same. The neural signals have to pass through the root ganglions within the spinal cord before reaching the brain. Hyperexcitability of these neural circuits due to malformed signals from the limbs is considered one of the major causes of phantom limb pain.
But the phantom pain signals couldn’t just arise in the periphery of the nervous system, and there must be a central mechanism for its perception. The neuromatrix theory proposes that there is a complex network connecting the thalamus and the cortex, and the cortex and the limbic system. It is a theory that goes beyond the homunculus theory and also incorporates the conscious awareness of the self arising from this connectome. This network although genetically predestined, is adaptively modified throughout one’s life via various sensory inputs thus creating a neuro-signature. It is this neurosignature of a specific part of the body that determines how it is actually perceived. The persistence of the same neurosignature, even after limb amputation, maybe the actual cause of phantom sensations and pain. Phantom pain may arise from abnormal reorganization in the neuromatrix to a pre-existing pain state.
Phantom pain is thought to be a temporary phenomenon and naturally fades within a year or two on average without any serious medical therapies. We still don’t have exact medical intervention to overcome the phantom pain but many psychological rehabilitation techniques are deployed like the distraction therapies and mirror box therapies. There are also claims that a maladapted neuroplasticity mechanism in pain circuits could be the cause, and readdapting this neuroplasticity mechanisms could completely overcome the phantom limb pains.
But who knows, maybe what we perceive itself is just a “glitch” in the (neuro) matrix! ; )