What is Neoplastic Lumbosacral Plexopathy?
Neoplastic plexopathy is a condition that often occurs at advanced stages of cancer, typically when the cancer has grown locally or spread to nearby areas. In simple terms, it’s when cancer affects a network of nerves in your body. This condition most often involves the nerve networks in the neck (cervical), arm (brachial), and lower back (lumbosacral). These are the areas usually affected by neoplastic plexopathy based on what doctors often see in their practice.
What Causes Neoplastic Lumbosacral Plexopathy?
Diseases involving the lumbar or lumbosacral plexus, the nerve network in your lower back, can come from many sources. These range from tumors to physical injuries. While injuries are more commonly connected to nerve damage in the upper arm, growths affecting nearby pelvic organs are typically involved with nerve disorders in the lower back. The inner position of these nerves in your body usually protects them from harm. However, they can still be affected by severe traumas such as high-impact accidents, pelvic fractures, gunshot wounds, and occasionally childbirth from the baby’s head exerting pressure.
Radiation treatment for pelvic tumors can also have an impact on the lumbosacral plexus. Other causes of nerve conditions in the lower spine can be inflammation of the nerves from conditions like diabetes or surgical complications, infections of adjacent organs, or infiltrative causes like amyloidosis, a disease where abnormal proteins build up in your organs.
Cancers are often the cause of lumbar plexopathy, a condition where these nerves in the lower back are damaged or dysfunctional. This nerve condition is present in roughly 15% of cancer patients when they first discover they have cancer and in about 1% of all cancer cases. The most common cancers related to this condition are cancers of the colorectal area, cervix, and uterus, lymphomas, and sarcomas in the retroperitoneal, a space in your abdomen. Especially in patients with a history of cancer, having a neoplasm (a new and abnormal growth of tissue) should be strongly considered as a cause for conditions affecting the lumbosacral plexus.
The lumbosacral plexus is close to many abdominal and pelvic organs. It can be negatively affected by direct invasions from nearby pelvic organs, such as the bladder, colon, ovaries, and cervix, either by infiltration or compression. Cancers can metastasize, or spread, causing more damage to these nerves. The most common of these metastatic cancers come from the lungs, breasts, and are lymphomas.
Another cause can be compression of these nerves from enlarged lymph nodes in the retroperitoneal space. Lymphomas can invade the neural tissue leading to a condition called intraneural lymphomatosis. These typically affect patients of Non-Hodgkin’s Lymphoma, most commonly in those with a subtype called Diffuse Large B Cell Lymphoma. This can occur even if lymphoma patients are in hematological remission. Symptoms can manifest as painful neuropathy that may be symmetrical or asymmetrical.
Cancers can also spread through the nerve sheath, particularly in prostate cancers. In very rare cases, tumors originating within the nerves themselves can also lead to plexopathy.
Radiation treatment for tumors within the lumbosacral region, such as cancers of the ovaries, cervix, colon, testes, and prostate, and Hodgkin’s lymphoma, can result in damage to the nerves of the lumbosacral plexus. The effects of radiation can be seen up to six months after treatment. These injuries result from the direct toxic effects on the nerves and the tiny arteries within them contributing to nerve damage. If used together, chemotherapy can increase the risk of radiation-induced nerve damage.
Risk Factors and Frequency for Neoplastic Lumbosacral Plexopathy
In people with cancer, a condition known as neoplastic lumbosacral plexopathy occurs in 0.71% of cases, while a similar condition called neoplastic brachial plexopathy occurs in 0.43% of cases. Neoplastic lumbosacral plexopathy is more frequently found in patients with tumors in the pelvic and colorectal regions. However, it’s also associated with lymphomas and breast cancer.
Signs and Symptoms of Neoplastic Lumbosacral Plexopathy
Lumbosacral plexopathy, a condition that affects the nerves in the lumbar and sacral regions of the spine, usually manifests on one side of the body but can affect both sides in about a quarter of patients. Using medical terms, this condition can involve the upper plexus (L1-L4), lumbosacral trunk (L4-L5), and lower plexus (S1 – S4).
The main symptom, experienced by 98% of patients, is pain in the affected area. This pain typically begins in the leg and is soon followed by a feeling of numbness and muscle weakness. The pain is usually dull and aching, but sharp, radiating pain can also occur. Certain positions or actions, like lying down, walking for a long time, sitting, or performing activities that increase pressure in the abdomen (Valsalva maneuver) can make the pain worse. Depending on which nerve is affected, the pain can spread from the back of the ribs to the upper thigh, or can involve the lower back, buttocks, thighs, or hips.
Aside from pain, neurological deficits, such as motor and sensory disturbances, are common and usually appear later. The most frequent issues include:
- Motor weakness (86%)
- Sensory disturbance (73%)
- Low reflexes (64%)
These disturbances can cause issues like leg swelling and difficulty getting up from a chair or walking up and down stairs. The condition is most often associated with colorectal tumors and cervical cancer when the lower plexus is typically involved. Other symptoms may include a pain radiating down the back of the leg, a sensation of a “hot, dry foot,” and numbness in the groin, thigh, or top of the foot. Sometimes, a condition known as “foot drop” may occur.
In cases where both sides of the plexus are affected, patients may experience problems such as incontinence and impotence. On rare occasions, a noticeable rectal mass, decreased anal muscle tone, and loss of sensation in the perineum may be observed.
Testing for Neoplastic Lumbosacral Plexopathy
If you’re experiencing symptoms that could suggest a condition known as LSP (Lumbosacral plexopathy), especially if you have a history of cancer, your doctor will be extra attentive. This is because cancer could potentially cause LSP – termed as ‘neoplastic LSP’. Deciding whether the condition is due to cancer or caused by radiation treatments given for cancer is often challenging. LSP might appear with symptoms on one or both sides of your body.
Your doctor will likely recommend imaging tests such as a CT scan or an MRI scan of the LSP. These tests offer a detailed view of your body and help to identify possible tumors. MRI scans provide even more comprehensive details and are usually the preferred choice for imaging. In some scenarios, these scans can reveal swollen nerves with irregular enhancement and accompanying cyst-like components – a characteristic different from non-cancerous causes of LSP, which depict smooth peripheral enhancement. If a local tumor is detected by clinical evaluation or imaging, it may indicate the development of tumor plexopathy.
Another potentially useful diagnostic tool is Positron Emission Tomography (PET) using a substance called 2-fluorodeoxyglucose (2-FDG). This could help identify active cancer in the area around the LSP.
Electromyographic studies, which examine the health and functions of muscles and the nerve cells that control them, can also provide important insights. The first part of this study, named nerve conduction study, may show weakened signals indicative of nerve damage. The second part, needle electromyography, could reveal more widespread nerve damage compared to what’s seen during the regular examination. The absence of a particular type of muscle activity (fibrillation) in spine muscles, coupled with the involvement of muscles from different root levels and peripheral nerves, would hint at LSP. This procedure could be useful in planning radiation treatment in some cases.
Occasionally, taking a small sample of nerve tissue for examination (nerve biopsy) could aid in diagnosis in some cases with potential cancer links.
Last but not least, examining the fluid that surrounds your brain and spinal cord (Cerebrospinal fluid or CSF) may also help. The laboratory may find an excessive amount of cells or protein in the CSF in conditions of lumbar plexopathy caused by cancer.
Treatment Options for Neoplastic Lumbosacral Plexopathy
When treating cancer-related lower back and pelvic nerve damage, or ‘neoplastic LSP’, radiotherapy is typically necessary. This treatment often works better when patients personally feel there has been an improvement, rather than when measured by doctors. It’s important to know that it can take up to 4 months before any noticeable improvement occurs. The treatment tends to be more effective when the radiation dose used is more than 300 cGy.
Unfortunately, radiotherapy can cause issues such as altered sensations, severe burning sensations, and chronic pain syndromes. These side effects often require further treatment using medications, patches containing a local anesthetic known as lidocaine, electrical nerve stimulation devices (known as TENS units), injections into the nerve group (sympathetic ganglion blocks) and very occasionally, surgical procedures to break down or remove part of the nerve network.
Managing this kind of nerve damage can be challenging and usually requires a combination of treatments including physical therapy and pain management. Even though there’s limited high-quality information from large scientific trials, we do have a variety of strategies for managing the associated pain. These methods can be physical, such as applying heat or cold or using TENS units. There are also medications taken orally that can help, ranging from different types of antidepressants, antiepileptic drugs like gabapentin and pregabalin, and strong painkillers when other treatments aren’t effective. Topical treatments, like lidocaine patches and capsaicin cream can also be used.
For some hard-to-manage cases, medical devices that stimulate the spinal cord or use medicine delivered directly into the spinal column may be needed. Physical therapy to strengthen muscles and improve balance and flexibility can be very beneficial, with custom support devices sometimes given to help with walking.
What else can Neoplastic Lumbosacral Plexopathy be?
When a person has a condition affecting the nerves in their lower back and hips (known as lumbosacral plexopathy), it can sometimes be linked to cancer. However, professionals have to consider other potential causes before confirming the diagnosis:
- Radiation-induced plexopathy: this is the most common cause and could be difficult to distinguish from others
- Chemotoxicity to the plexus, which could be the result of intra-arterial chemotherapy
- Paraneoplastic plexopathy, which is related to the presence of cancer elsewhere in the body
- Postinfectious plexopathy, which happens after an infection
- Compression of the spinal cord, due to spread of cancer cells in the fluid that surrounds the brain and spinal cord (leptomeningeal involvement) or in the protective layers of the spinal cord (epidural cord)
- Primary tumors in the plexus itself
It can be particularly tricky to distinguish between radiation-induced plexopathy and recurrent cancer, especially if the person underwent radiation therapy for pelvic or abdominal tumors. The radiation can damage the nerves directly or through tiny blood clots. Plexopathy due to radiation can come about anywhere from 3 months to 14 years after therapy, but usually around 1.5 years later. The use of smaller amounts of radiation and lower-dose chemotherapy can reduce this risk.
If doctors need to differentiate between radiation-induced and cancer-related plexopathy, they will look for certain signs:
- The nerves may feel abnormal (dysesthesias) and numb, often with swelling due to fluid accumulation (lymphedema)
- While both types can be painful, pain is less common and usually milder and later-appearing in radiation-induced conditions
- Radiation plexopathy is more likely to affect both sides of the body
- There may be break periods where symptoms do not worsen
- The condition generally worsens more slowly than cancer-related plexopathy
- Electrical testing of muscle activity (EMG) may show specific types of electrical discharges
- While MRI scan may show increased signal in both conditions, nerve enhancement is usually only seen in cancer-related condition. Signs of local tissue damage may be present in radiation-induced condition
Positron emission tomography (PET) scans are helpful to detect recurrent tumors, as they are typically negative in radiation-induced plexopathy.
Management of radiation-induced plexopathy is symptomatic, and treatments such as hyperbaric oxygen can offer relief. Procedures to repair or replace damaged nerves have had limited success.
What to expect with Neoplastic Lumbosacral Plexopathy
For patients who have neoplastic plexopathy, a condition caused by tumors affecting the nerves, the outlook is often not very good. This is usually due to the advanced stage of their cancer. Their life expectancy tends to be shorter as a result.
Treatment should focus not only on managing the main tumor, but also on enhancing the patient’s quality of life. This includes managing pain symptoms linked to their condition.
Possible Complications When Diagnosed with Neoplastic Lumbosacral Plexopathy
Side effects from radiation can include uncomfortable or abnormal sensations (dysesthesias), an intense burning pain (causalgia), and long-term pain conditions. To address these, a range of treatments are used, such as:
- Medications
- Patches containing a local anesthetic (lidocaine)
- Transcutaneous Electrical Nerve Stimulation (TENS) units, which use electrical signals to manage pain
- Sympathetic ganglion blocks, a type of nerve block to manage pain
- Rarely, dissection (cutting or separating tissue) of the nerve bundle (plexus) and breaking up and destroying nerve tissue (neurolysis).
Preventing Neoplastic Lumbosacral Plexopathy
It’s important to have a detailed conversation about the available treatment options and their possible side effects. This involves a team-based decision-making process, which is necessary to decide on the best course of treatment.
