The spine is made up of 33 bones called vertebrae and divided into four regions: cervical (neck), thoracic (mid back), lumbar (lower back), and sacrum. The spinal cord, a thick band of nerve tissue that runs through the spine, is surrounded by bones called vertebrae which provide 360o protection. The spinal cord ends most frequently at the 1st or 2nd lumbar vertebra, though it can end anywhere from the 12th thoracic vertebra to the 3rd lumbar vertebra, in a structure called the cauda equina. At the cauda equina the spinal cord branches into ten separate nerve roots, five of which exit through openings in the vertebra, called foramen, and combine in the buttock to form the sciatic nerve, the longest and largest nerve in the body. The sciatic nerve supplies sensory and motor function to the legs; compression of the sciatic nerve leads to a set of symptoms known as sciatica.
The sciatic nerve is the largest nerve in the body; it is made up of the nerve roots L4 through S3 meaning that it runs down the back of each leg and branches at each knee. Sciatica is a relatively well-known condition that produces pain symptoms down the back of the legs.
Sciatica comes in acute and chronic forms, defined by the duration of symptoms. Acute cases occur suddenly, often because of disc herniations, and last for six weeks or less. Chronic cases typically start as an acute condition, but progresses and causes pain for over three months. Any spine condition may cause chronic sciatica, including spinal stenosis, spondylolisthesis, and disc degeneration.
The sciatic nerve is the largest nerve in the body; it travels down the buttock from the spine and into the leg, where it branches into two separate nerves at the knee. Compression of the sciatic nerve, the cause of sciatic pain, can be caused by spinal stenosis, disc herniation, or structural abnormalities such as a spondylolisthesis and disc degeneration.
Spinal stenosis, narrowing around spinal nerves because of wear and age, is the most common cause of sciatica. Spinal stenosis can cause bone spur formation in the foramen, spaces through which nerves branch from the spinal cord into the body. The facet joints in the spine can also increase in size, narrowing the foramen. If this occurs in the lumbar region, specifically at the L4 and L5 levels, it may cause sciatica since the L4 and L5 nerve roots help to form the sciatic nerve, along with the S1, S2, and S3 nerve root.
Each pair of spinal vertebrae has an intervertebral disc in between for shock absorption, which is made of two parts, the outer fibrous area, annulus fibrosis, and an inner jelly-like substance, the nucleus pulposus. As the disc experiences wear and tear from increased weight gain, repetitive bending and twisting, and natural aging processes, the outer portion of the disc develops small tears and these weak areas make it easier for the inner disc portion to push through and compress nerves. The disc also begins to dry over time and it loses its height, causing the amount of space between each pair of vertebrae to decrease and shrink the foramen, the space through which nerve roots exit the spinal cord.
A spondylolisthesis is a malalignment of the vertebra in which one vertebra slides forwards or backwards over the one below vertebra. There are different causes for a spondylolisthesis, but the most common cause is a fracture of the pars interarticularis, which is the piece of bone that connects the upper and lower facet joints on each vertebra. The fracture usually occurs as a result of hyperextension injuries in the back with activities such as gymnastics. This malalignment occurs at the L5-S1 level most frequently and as the vertebrae slides forward, this narrows the space the nerve roots have to exit the spine, causing compression.
The multiple causes of sciatica all create similar symptoms, though these will vary by which nerve root is being affected and causing the symptoms. Severe leg pain is the most common symptom and back pain is sometimes present as well. Patients with spinal stenosis, disc degeneration, and spondylolisthesis are more likely to have symptoms of low back pain.
Leg pain is the most common symptom of sciatica and can range from mild to severe and debilitating. Pain is usually sharp, shooting, with numbness or tingling and radiates in the pattern that the sciatic nerve runs, starting in the buttock and moving down the back of the leg and into the foot. The pain generally worsens while sitting or standing in one area for too long and while changing positions from laying to sitting or sitting to standing though activity and laying down seem to help with improving pain. Pain also worsens while extending the lumbar spine, for example while leaning back at the waist, as more compression is placed on the already compressed nerve.
There may also be symptoms of weakness in the leg though specific symptoms will vary with the nerve root being compressed. These symptoms may or may not be present and can be present in combination if multiple nerve roots are affected.
L4: The L4 nerve root, which is the first to feed in to the sciatic nerve, supplies the quadriceps femoris muscles. These muscle help extend, or straighten, the knee. Compression at this level may cause weakness while straightening the knee, which may create the feeling of the knee buckling.
L5: The L5 nerve root supplies the tibialis anterior muscle which, pulls the foot up towards the face, and toe dorsiflexion, which brings the toes up toward the face. Compression of the L5 nerve root may cause weakness in bringing the foot up while walking, giving rise to a drop foot, a motion in which the foot ‘slaps’ the ground while walking.
S1: The S1 nerve root innervates the calf muscles, some of the hamstrings (muscles on the back of the thigh), and the gluteus maximus (buttock muscle). The calf muscles allow for plantar flexion, or pressing down of the foot, like pushing a gas pedal in a car. Compression of the S1 nerve root may cause difficulty standing on your toes.
Severe forms of sciatica, can lead to cauda equina syndrome, which is in the cauda equina, a series of nerves at the end of the spinal cord that resembles a horse’s tail. Cauda equina syndrome produces a large amount of inflammation around the cauda equina and distinct symptoms which include saddle anesthesia (numbness in the perineal regions, or the region that would make contact while sitting in a saddle), bowel and/or bladder incontinence, weakness in the legs, and unsteadiness while walking. This is a rare condition, but is serious and requires immediate attention to prevent irreversible damage to the nerves.
Patient history and physical examination are typically the first step in diagnosing sciatica. Types of symptoms, duration of symptoms, factors that improve/exacerbate symptoms, treatments that have been already tried, and past relevant medical problems/surgeries are all collected during the history. The physician completes a physical exam to check for specific symptoms by inspecting the back, assessing gait, and testing lower extremities for motor strength, reflexes, and range of motion.
Both history and physical exam contribute to the diagnosis of sciatica, but imaging is necessary to finalize the diagnosis. X-rays are typically obtained first to look at the overall alignment of the spine and to check for spinal abnormalities such as scoliosis (curve in the spine), that may affect viable treatment options. These 2D results are supplemented with advanced imaging tests such as MRI or CT scans because these show a 3D view of the spine. MRI scans which show soft tissues, such as nerves and discs, are generally preferred over CT scans which show bony elements. Advanced imaging can show exactly which nerve or nerves are affected. Together history, physical exam, and imaging are all necessary in order to make a correct diagnosis and design an optimal treatment plan for sciatica.
Physical exam abnormalities for the lumbar spine tend to occur exclusively in the lower body. It is important to start by looking at the back for changes in the skin, decreases in muscle size, or unevenness from one side of the back to the other. The next step would be palpation of the muscles and center of the back. Lumbar spine range of motion is tested with flexion, such as touching toes, and extension, leaning back at the waist to look for decreased motion due to pain. Motor strength testing would be performed on the lower extremities because weakness in certain muscle groups could imply sciatica at the lumbar level where the relevant nerve branches from the spinal cord. Changes in sensation may also be tested throughout the leg to check for areas with decreased sensation throughout or relative to the opposite leg. Increases or decreases in the patellar and Achilles reflexes are commonly used to test for spinal nerve compression and can potentially identify the affected spinal level because they are connected to the L3/L4 and S1 nerve roots respectively. Other exam results that imply sciatica are abnormal walking patterns, including inability to walk on the heels and the toes.
Once sciatic is diagnosed through history, physical exam, and imaging studies, a treatment plan is created. Treatment generally begins with addressing symptoms through conservative, non-invasive options and may include a combination of options. These options include alternative therapy, medication, physical therapy, injections, and lifestyle modifications.
Traditional spine surgeries, also called open back surgeries, use large incisions with destruction of the surrounding muscles and tissues leading to longer healing time. There are multiple different minimally invasive options that can be used for the treatment of sciatica. Both decompressive and stabilization procedures are options to treat sciatica. The type of surgery that will be appropriate for the treatment of sciatica will largely be due to the cause of sciatica. The different types of surgical options available are all minimally invasive, which uses small incisions and minimal muscle and tissue damage for faster healing.
Certain lifestyle factors may increase the incidence of sciatica, such as smoking and increased weight. Smoking decreases blood flow throughout the body which is needed to repair damaged tissues. Cessation may restore blood flow, allowing the tissues to access proper nutrition. Added weight may increase the risk for sciatic because of the extra stress placed on the disc. Reducing weight through a low-calorie diet and exercise can reduce pressure on the spine, decreasing the symptoms of sciatica.
Repetitive leisure or work-related motions such as excessive bending, lifting, and twisting, along with any activity that may be high impact on the spine, such as running or riding ATVs, can also lead to sciatica. Some of these repetitive task activities may be due to leisure and others due to demands of a job. For people with full labor or heavy-duty jobs, you may need to change jobs or support your work with proper lifting technique, relaxed breaks, and equipment such as a back brace to avoid worsening symptoms. You may also need to alter or avoid high impact activities, such as running to reduce the symptoms of sciatica.
Alternative therapies include massages, chiropractic care, and acupuncture. These may also be referred to as manual therapies since they address the spine with hands on technique. Massage relieves tension in muscles surrounding the spine and in arm and leg muscles experiencing radiating symptoms. These muscles may be under tension due abnormalities with walking and changes in posture due to pain from sciatica. Chiropractic care may use specific techniques, such as adjusting the spine or application of traction on the spine. Acupuncture may also provide pain relief as muscles are stimulated electrically.
Physical therapy focuses on changing body mechanics to improve posture and walking as well as to strengthen and retrain muscles, particularly those in the core. The initial step is meeting with a Physical Therapist for a consultation to assess posture, gait, and muscle weakness and to design a personalized exercise program. Other techniques that physical therapists may use are manual treatments such as massage, ultrasound, and electro-stimulation through a TENS (transcutaneous electrical nerve stimulation) unit. A combination of these methods can provide symptom relief.
A home exercise program may be used in conjunction with or instead of a formal physical therapy regimen. A daily low impact exercise regimen is important for strengthening muscles, especially those in the core. Low impact cardiovascular activities such as walking, swimming, elliptical, and biking are also important for increasing blood flow and strengthening muscles without adding stress on the spine. Home exercise can also lead to weight loss which may reduce pressure on the spine and reduce symptoms. Home exercise routines should be paired with stretches and physician supervision to avoid harm.
There are multiple types of prescribed and over the counter medications that may be used to treat the symptoms of scitaica. Some of these medications include Tylenol (acetaminophen), NSAIDs (nonsteroidal anti-inflammatory drugs), muscle relaxants, nerve membrane stabilizers, topical medications, and off label medications.
Common over the counter medications are acetaminophen and NSAIDs. Acetaminophen is considered an analgesic, meaning it relieves pain but does not reduce inflammation. NSAIDs are effective at both relieving pain and reducing inflammation; they can be found in brand and generic forms over the counter. These medications are best taken with food to avoid an upset stomach. They can be taken for longer durations, as long as there is no history of kidney disease. The mechanism of both NSAIDs and Acetaminophen differ, so they are taken together often to combat pain.
Muscle relaxants are used to provide relief from muscle spasms and increase range of motion; they are best used in combination with physical therapy or an exercise/stretching regimen. Drowsiness is a common side effect of muscle relaxants and they are not recommended while driving or working. Common muscle relaxants include Flexeril, Soma, Baclofen, Robaxin, and Tizanidine.
Nerve membrane stabilizers are another class of medications often used to treat the numbness, tingling, shooting, stabbing, or radiating pain associated with sciatica. Gabapentin (Neurontin) and Lyrica (Pregabalin) are commonly prescribed nerve membrane stabilizers and work by reducing pain signals released by nerves. Both medications, Gabapentin especially, can be taken in higher dosages multiple times per day, but this class of medication may cause dizziness and drowsiness. Nerve membrane stabilizers are typically started on a low and infrequent dose; the dosage is gradually increased until the pain is controlled and then gradually decreased prior to discontinuation.
There are other medications that may be used ‘off-label,’ meaning not for the use listed on the label. Some common medications used off label for pain are anti-depressants, such as Cymbalta and Amitriptyline. Similar to the nerve membrane stabilizers, these medications are slowly increased in dosage and they also target nerve-type pain, such as burning, numbness, and tingling associated with nerve pain. They may also cause drowsiness and are usually used at night for pain control.
Epidural Steroid Injections
Epidural steroid injections reduce pain by injecting steroid, or anti-inflammatory, medication at a specific level/levels in the spine. As the herniation places pressure on a nerve, this causes inflammation of the nerve and surrounding tissue which causes pain. A specialized needle is used to deliver medication to the correct area, past the muscles of the back and as close to the spinal nerves as possible. As steroids are a natural anti-inflammatory, this may reduce the inflammation around the nerve, diminishing pain caused by the disc herniation. Steroid injections have the ability to provide pain relief for up to several months, and provide better pain relief for radiating symptoms, such as leg pain, than treatments designed for back pain alone. Steroid injections are only safe to have completed 3 times in one year and must be at least one month apart between sequential injections. This is due to the muscle and tendon breakdown with exposure to the steroid medication too often or too soon.
A microdiscectomy is a minimally invasive surgical decompression procedure that is typically performed on the lumbar spine to address disc herniations that lead to sciatica. A small incision is made in the midline of the back until the joint of the spine, the facet, is reached. A small portion of the joint is removed to visualize the spinal nerve and disc herniation. The disc herniation is removed and once the nerve is free of compression, the incision is closed.
Endoscopic discectomy is a minimally invasive surgical decompression procedure that uses specialized instrumentation in order to perform the disc removal. A small incision is made on the midline of the back and a specialized imaging tool, called a fluoroscope is used to determine the correct vertebral level is targeted for the procedure. After the incision is made a thin wire, called the guide wire, is placed until it hits bone. A series of small cylindrical tubes are then placed over the guide wire to open the incision. A specialized retractor and light source is place down these tubes and all the instruments are placed down through the tubes and the disc material is removed to free the nerve root of compression. This special retractor is then readjusted to target the opposite side of the spine. All the instruments are removed and the surgery is completed.
A transverse lumbar interbody fusion (TLIF) is a minimally invasive stabilization procedure that uses a specialized implant to fix the appropriate disc level. This procedure is performed through a small incision on the midline of the lumbar spine. Once the spine is reached, the backside portion of the vertebrae is removed, the laminae, until the nerve is reached and the compression on the nerve is removed. The disc material is removed from the disc space and a special implant with bone graft is placed into the disc space with screws placed into the vertebral body above and below the disc space, that are connected via rods. Once the procedure is complete the spinal level is fused.
All of these procedures are minimally invasive and are either decompressive or stabilization procedures. Decompressive surgeries remove tissue, such as a disc herniation that is compressing the nerve root, without adding any hardware or fusing the spine. Stabilization procedures remove the old, worn out intervertebral disc and replace this with an implant and bone graft that will fuse the level, in addition to hardware, to lock down this level of the spine. The procedure that is most appropriate to perform will depend on multiple factors including cause of sciatica, amount of bony removal that will be necessary to achieve proper decompression of the nerve, any prior surgeries, and imaging. The history, physical examination, and imaging are all necessary components to planning the proper minimally invasive surgery for sciatica.
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