Lumbar rhizotomy is known by several different names. Lumbar denotes the region of the body being treated. Lumbar means the lower back part of the spine. Rhizotomy has several synonyms. Rhizotomy means a severing or interruption of a nerve. Rhizotomy is also known as neurotomy. They both mean the same thing. Sometimes, a rhizotomy is named by the way it is performed. If a rhizotomy is performed by using radiofrequency energy it is called a radiofrequency rhizotomy or radiofrequency neurotomy. If the rhizotomy is performed by using the injection of a chemical then it is called chemo-rhizotomy or chemical rhizotomy. Lastly, a rhizotomy may be performed using surgical techniques and will then be referred to as a surgical rhizotomy.
What all different forms of rhizotomies have in common is that they all involve the interruption of a nerve fiber. There are certain conditions, usually very painful conditions, where a nerve fiber is involved in the sensation of uncontrollable pain. In these cases where there is no effective treatment of the pain, a physician may interrupt sensation by mechanically dysrupting the nerve fiber (think of it as “cutting” a wire.”
Functionally, this is similar to how an anesthetic works. When a doctor injects an anesthetic, electrical transmission in a nerve fiber is blocked and the nerve fiber cannot transmit pain signals. Unfortunately, the anesthetic wears off and does not last more than a few hours. However, with a mechanical interruption of the nerve fiber the interruption of nerve transmission lasts much longer or can be permanent.
In a radiofrequency rhizotomy, energy in the form of high intensity radio waves administered through a tiny electrode is used to heat the target nerve fiber. With enough heat the nerve fiber burns and becomes coagulated. This is a thermal or burning type of destruction of the nerve fiber. In this type of rhizotomy the burn is very precise and there is little or no injury to non-target structures. Another form of rhizotomy is a chemical rhizotomy, like glycerol rhizotomy. In this rhizotomy, a chemical agent is injected that causes destruction of the nerve fiber. Lastly, there are surgical rhizotomies. In surgical rhizotomy the nerve fiber is simply cut.
The success of the lumbar rhizotomy is predicated by the response to a certain diagnostic test. This diagnostic test is called a medial branch block. The medial branch nerves are small pain sensing nerves that travel next to the vertebra on the outside of the spine. These nerves sense pain emanating from the spinal facet joints. In order to simulate the result from performing a rhizotomy on this nerve, the physician injects an anesthetic on the medial branch nerves and then reevaluates the patient. If the patient's pain is gone, or mostly gone, this predicts a high likelihood of a positive response from lumbar rhizotomy. If the patient still has significant pain, either a lumbar rhizotomy will not help or there is another significant pain source in addition to the lumbar facet joints.
In addition to predicting the likelihood of successful lumbar rhizotomy, a medial branch block is required to diagnose the underlying condition that would be treated with a lumbar facet block. Every major spine medical society has acknowledged that MRI, CT scans and x-rays are insufficient for diagnosing lumbar facet pain. Therefore, to make the diagnosis, a medial branch block is performed as a diagnostic procedure. If all or most of the pain is relieved, then the physician can reliably diagnose that the patient's pain is emanating from the spinal facet joints that are innervated by the targeted medial branch.
There are no specific findings that would lead a physician to perform a rhizotomy without having first performed a positive lumbar medial branch block. The presence of a positive lumbar medial branch block takes precedence over physical findings and examination findings and determining which patients should undergo lumbar rhizotomy.
It is important for a patient to note that lumbar rhizotomy should not be undergone without having had a proper diagnostic procedure. A proper diagnostic procedure is a medial branch block performed with an anesthetic only. If steroid injections are administered along with the anesthetic injection this may mask other types of pain coming from other sources. The patient may undergo lumbar rhizotomy and therefore not get the same level of improvement that the patient had from the injection. In addition, a patient undergoing a diagnostic medial branch block should challenge that block by recreating physical activities following the block that would normally be painful. A positive block would be seen in cases where the patient can now tolerate physical activities that would have previously been difficult to tolerate. Lastly, it is important that the physician reevaluate the patient not only on the day of the block but within a few days. A careful and timely evaluation is the best way to document that the patient did indeed have a positive block and therefore would benefit from a lumbar rhizotomy.
The nonsurgical lumbar rhizotomy procedure can be performed in the hospital, the outpatient surgery center or a physician office. The procedure may or may not be performed with sedation. The procedure is always performed with local anesthesia.
The patient typically will have nothing to eat after midnight and will come to the operating facility in the morning. An IV may or may not be inserted. The patient will be taken to an operating table. An x-ray machine will be present. Using x-rays the physician will be able to precisely pinpoint the location of the lumbar medial branch nerves. Using x-ray guidance the physician will place a needle over each target nerve.
There are 2 nerves providing pain sensation for each lumbar facet joint. Following local anesthesia, the physician will insert an electrode through the targeting needle so that the electrode will be adjacent to the target medial branch nerve. The electrode is attached to a cable which is in turn plugged into a radiofrequency generator machine. The radiofrequency generator will be activated and radiofrequency energy would be administered until electrode sensors detect that there has been local heating around the electrode up to 80°C for 60 seconds.
Following the procedure a Band-Aid will be placed over the insertion sites and the patient will go home. Normal activity can be resumed by the next day.
The best alternative to a lumbar rhizotomy is actually a surgical form of lumbar rhizotomy called endoscopic lumbar rhizotomy. In the endoscopic lumbar rhizotomy procedure a surgeon actually cuts, or avulses, the medial branch nerve.
To perform an endoscopic lumbar rhizotomy the patient is positioned on the table in a similar fashion to a radiofrequency rhizotomy. A tiny incision is made and a tube about half the diameter of a dime is inserted through the tiny incision. On one end of the tube is a precision lens. The other end of the tube is connected to a high-definition camera. Through the high-definition camera a high resolution view of the spine is projected to the surgeon using a heads-up display. The surgeon is able to locate the medial branch nerve and actually cut it under direct visualization.
The biggest advantage that endoscopic lumbar rhizotomy has over traditional forms of rhizotomy is permanence. About 50% of people that have traditional lumbar rhizotomy will have a recurrence of pain within 6-12 months. This is because the heat energy used to coagulate the nerves results in incomplete destruction of the nerves. As a result, there is some nerve regeneration and, in many cases, a return to pain. With the endoscopic procedure, the surgeon can directly visualize the nerve and cut it so that it does not regrow. As a result, endoscopic lumbar rhizotomy is a permanent procedure that never has to be repeated.
The recovery from endoscopic lumbar rhizotomy is rapid. The actual surgery takes about an hour. Patient's return home the same day. Patients can start to resume activity the next day. Patients can usually return to work within several days.
The endoscopic lumbar rhizotomy procedure is a safe and efficacious procedure. The effectiveness of the procedure is extremely high in patients that have been carefully selected with medial branch blocks. Because the medial branches that are targeted by the procedure are outside the spine, one does not see many of the typical complications associated with spine surgery. In short, endoscopic lumbar rhizotomy is a spine surgical procedure with a lot of bang for the block.