VIRGINIA BRAIN & SPINE CENTER
Pain is a complex physical phenomenon that is experienced differently by each person. Pain is a necessary part of our anatomy and physiology. It is a strong and convincing signal that injury is occurring to our body and something needs to be done to help it heal appropriately. New or acute pain will often resolve after the injury itself is treated and healed. Chronic pain can occur when an injury does not heal well or the nerves that signal the pain are themselves injured. Pain is a primitive yet complex phenomenon that is closely tied to our mental health and emotions. Chronic pain is therefore best treated by addressing the physical and emotional aspects of pain. Pain specialists often work closely with surgeons, physiatrists, physical therapists, and psychologists to minimize the effects of this otherwise debilitating medical problem.
Pain begins with the detection of a signal at the point of origin. In general, there are two types of pain that can be detected. There is deep, dull, and aching pain that is detected by large, slow nerve fibers and sharp, shooting pain that is detected by smaller, faster nerve fibers. These peripheral nerve fibers initiate a chain of signals up the spinal cord to the brain stem which then triggers an entire cascade of signaling throughout the brain. This is a very primitive part of our neuroanatomy that normally functions to protect us from injury. As such, there are close ties and interactions with almost the entire brain. The physical sensation of pain is therefore influenced by many complex processes including thoughts and emotions.
On a cellular level, there are a number of chemicals that are known to either stimulate or inhibit pain signals along these complex pathways and these chemicals are often targets of pain medication. With chronic pain, these signals may be continuously induced by an ongoing injury that appropriately triggers this cascade. Alternatively, the cascade can be inappropriately triggered after the injury is resolved due to failure of the appropriate feedback mechanisms. With the former scenario, relieving the point of injury will stop the triggering of the pain pathways. This is one of the goals of neck or back surgery. In the latter scenario, the pathway itself needs to be blocked in order to stop triggering the signals. This is the goal of various pain blocking procedures including spinal cord stimulation, intrathecal pump placement, radiofrequency ablation, and spinal injections.
Failed Back Syndrome
Failed Back Syndrome, also known as postlaminectomy syndrome, is a chronic pain condition that persists despite prior lumbar (low back) surgery. Symptoms include back and leg pain similar to those prior to surgery. Imaging studies demonstrate appropriate postoperative changes without specific complications. Sometimes there are persistent findings such as disc herniation, bone spurs, or scar formation. However, repeat surgeries to try and fix the underlying problem are unlikely to be of any benefit. If symptoms persist despite normal findings on postoperative studies then this should be considered failed back syndrome. If there are abnormal findings but repeated surgeries fail to relieve the symptoms then this should also be considered failed back syndrome. Unfortunately, many patients will pursue multiple unsuccessful surgeries in order to try and obtain relief. In general, someone who has had three lumbar surgeries without long term benefit should be considered to have a diagnosis of failed back syndrome.
Failed back syndrome is due to persistent underlying pathology that cannot be relieved with surgery. This may be due to ongoing pressure on the nerves or to abnormal signaling within the pain pathways. In either case, the goal of treatment should no longer be to relieve the underlying factors initiating the pain but to inhibit the pain signaling pathways directly. Unfortunately, complete freedom from pain is very unlikely and should not be expected. Treatment should be geared towards decreasing the intensity and frequency of pain such that effects on quality of life and functional ability are limited.
Initial treatment involves surgical evaluation, pain medication and physical therapy. Once further surgery has been ruled out as a reasonable option then referral to a pain management specialist is warranted. Various injections and minor pain procedures may be able to improve the symptoms. A multidisciplinary team approach is ideal involving pain management, physical medicine, and psychology specialists. Patients who require chronic narcotic pain medication may benefit from placement of an intrathecal pump. Others may benefit from a spinal cord stimulator.
Complex Regional Pain Syndrome
Complex Regional Pain Syndrome (CRPS) is a chronic pain condition that results in rather severe pain that is out of proportion relative to any known underlying injuries. There are no diagnostic criteria for CRPS. CRPS type I, also known as reflex sympathetic dystrophy, has no known underlying injury whereas CRPS type 2, also known as causalgia, does have a known underlying injury. The classic findings include burning pain in one or more extremities, autonomic dysfunction (color changes, sweating, and swelling), and trophic changes (loss of muscle). The pain can involve the arms and/or the legs and the skin can be very sensitive even to normal touch. It is not known exactly what causes CRPS and there are likely multiple mechanisms. The sympathetic nervous system clearly plays a role in some patients and can be targeted for treatment. Although there is no cure for CRPS there are treatments available that can help alleviate the pain symptoms. A multidisciplinary team approach is ideal involving pain management, physical medicine, and psychology specialists. First line therapy involves pain medications. Effective medications may include narcotics, anti-inflammatory medication, anti-depressants, and neuroleptic medications which interfere with the pain pathways. Physical therapy, topical agents, and TENS unit stimulation may be beneficial. Various injections and minor pain procedures are often tried for refractory symptoms. Sympathetic blockade or sympathectomy (cutting the nerves that supply the sympathetic input to the affected limb) may be useful in some patients. Patients who require chronic narcotic pain medication may benefit from placement of an intrathecal pump. Others may benefit from a spinal cord stimulator.
Trigeminal Neuralgia is a facial pain syndrome due to irritation of the fifth cranial nerve, also known as the trigeminal nerve. The trigeminal nerve supplies sensation to most of the face as well as motor supply to some of the facial muscles. The trigeminal nerve has three main branches that supply the upper, middle, and lower face. Typical trigeminal neuralgia results in sharp, shooting, stabbing pain in one or two of the three divisions. The middle and lower divisions are most commonly involved and cause pain in the cheek and jaw. Trigeminal neuralgia often involves very brief but very severe episodes or spasms of pain. The pain can be induced by light touch on the skin or movement of the jaw. Atypical symptoms include constant pain, dull or aching pain, and neurological deficits such as numbness or weakness in the face. It is thought that most cases of trigeminal neuralgia are due to compression of the nerve where it enters the brain stem. The nerve travels in a tight corridor along the side of the brain stem with multiple arteries and veins that can push and pulsate on the nerve. Trigeminal neuralgia can also be symptomatic of a specific disease process. This is much less common and includes tumors in this location, tumors on the nerve itself, or injury to the nerve such as can occur with multiple sclerosis. There is a broad spectrum of similar diseases that can cause similar symptoms and trigeminal neuralgia is often confused with dental problems, TMJ, or many common headache syndromes.
There are several treatment options for trigeminal neuralgia. Most patients will respond to tegretol and a good response to this medication is almost diagnostic. There are several other medications that may be of benefit as well. Patients with persistent symptoms or side effects with medication alone may benefit from one of several procedures. Microvascular decompression is considered the best treatment for those patients who are good surgical candidates. Other options include minimally invasive needle procedures to destroy the nerve such as radiofrequency ablationor glycerol injection. Radiosurgery may be performed to target a high dose of radiation on the nerve where it exits from the brain stem.
Spinal Cord Stimulator
A spinal cord stimulator involves placement of a small electronic device that can be used to modulate the pain pathways. A small wire is placed near the back surface of the spinal cord through a minor surgical procedure and connected to a programmable battery. The wire can be placed such that it can interfere with pain signals from one or both legs or arms. It is less effective for neck and back pain. An outpatient trial is performed first in which the wire is placed percutaneously (through a needle incision) and connected to an external battery that the patient can carry and control. The spinal cord stimulator results in a nonpainful sensation that partially blocks or replaces the painful sensation. A successful trial will result in at least a 50% reduction in the intensity of the pain and is unlikely to completely eliminate it. However, this reduction can result in a significant improvement in quality of life by allowing more activity, better nighttime sleeping, or decreased narcotic pain medication. If the trial is successful then a permanent wire and battery are placed. A minor surgery is performed to implant the programmable battery in the soft tissue behind the hip. The wire can be placed percutaneously or through a small incision that would allow a larger wire and more contacts. Both the trial and the permanent placement are usually performed on an outpatient basis without a stay in the hospital.
The effectiveness of spinal cord stimulation for chronic pain is quite variable and controversial. Patients who may be considered appropriate candidates include those with failed back syndrome orcomplex regional pain syndrome. Patients who are considered candidates for a spinal cord stimulator trial have at best a 60-70% chance of significant benefit. Unfortunately, recurrent pain is rather frequent after 1-2 years with up to 50% of patients no longer receiving benefit in long-term follow-up. Treatable causes for recurrent pain such as wire breakage, disconnection, migration or battery failure need to be investigated in these cases.
Radiofrequency ablation is a minimally invasive procedure in which a portion of the trigeminal nerve is burned. This is often done with gentle anesthesia and local anesthetic to monitor for effectiveness during the procedure. A small incision is made in the cheek and a needle is guided with xrays to the trigeminal nerve where it exits from the skull base. Once the tip of the needle as next to the nerve, the needle is connected to a wire and a gentle radiofrequency impulse is generated at the tip of the needle to make a lesion in the nerve. This will invariably cause numbness in the face but also stops the pain.
Radiofrequency ablation of the trigeminal nerve is done as an outpatient procedure. There is an initial 90-95% success rate with this procedure. However, recurrences are common. Up to 80% of patients will have recurrent symptoms in 10 years. Because of the relatively high recurrence rate, this procedure is often reserved for patients who are not good surgical candidates or for those who refuse or have failed microvascular decompression.