Neuropathic pain — the dysfunctional alarm

In a broad sense, pain is much more than a sensation. Pain can be a lifesaver. Pain can be pleasure. Pain can be the gate to heaven. Pain can be just an emotional suffering.

When we talk about the physiologic meaning of pain, we can think of the pain system as the alarm system of the body. It is essential for the survival of the organism and complete loss of pain sensation is not compatible with survival.

The alarm is activated when a potential harm to the organism occurs, leading to activation of the pain receptor in a process we call “transduction.” The pain receptor then sends the signal to the brain through the peripheral nerve into the spinal cord,  up to the part of the brain that makes us perceive sensations. That part is called the thalamus. That is the normal process, and is the adequately functioning alarm.

Sometimes, the pain transmission system itself gets injured — from a disease or trauma — and starts sending signals along the pathways that is interpreted by the brain as pain. This is when the alarm system is broken and is continuously beeping. This is what we call neuropathic pain.

Neuropathic pain is common and is caused by a variety of conditions that affect a variety of components of the nervous system. It also is the disorder when pain, instead of being the sign of a problem, is in fact the problem itself. It can result from diseases such as diabetes, trauma and stroke, and it can result from diseases such as carpal tunnel syndrome and “trigeminal neuralgia” — a nerve disorder that causes a stabbing pain in parts of the face. The disorder can be mild or it can drive individuals to suicide.

There are effective drugs to treat neuropathic pain, but when all medical therapy fails, other options exist including alternative therapies.

Neurosurgeons can help in certain cases of neuropathic pain. Trigeminal neuralgia is one condition where neurosurgeons have a variety of options that can help alleviate the pain. These include a surgical procedure where a compressing vessel is moved away from the nerve (called microvascular decompression). Also, we can perform a minimally invasive thermal lesioning of the nerve that stops the pain for some time (called radiofrequency rhizotomy).

A technology that was developed two decades ago, called spinal cord stimulation, can also be very effective in treating neuropathic pain. Spinal cord stimulation uses a phenomena called the gate theory where the dysfunctional alarm is silenced or dampened by creating what is an essentially a white noise or alternative non-annoying beep to cancel the annoying dysfunctional alarm beep.

Ahmed Raslan, M.D.
Assistant Professor, Neurological Surgery
OHSU Brain Institute