The spine is made up of 33 bones called vertebrae and divided into four regions: cervical (neck), thoracic (mid back), lumbar (lower back), and sacral. The vertebrae surround the spinal cord, a thick band of nerve tissue that runs through the spine, providing 360o of protection. Spinal stenosis is a disease marked by narrowing of the spine around the spinal cord or at the foramen, openings in the spinal vertebra through which the spinal cord branches to the hands, legs, torso, and other locations in the body. Narrowing can occur centrally and at the foramen simultaneously. Stenosis most commonly occurs in the cervical and lumbar regions of the spine because these areas experience the most flexibility and movement. The extra motion can place more pressure on the spinal cord or nerve roots over time.
Any narrowing upon the neural elements, including the spinal cord and exiting nerve roots is called spinal stenosis. The narrowing can occur from a variety of things including disc herniations, disc bulges, abnormal alignment, scoliosis, and bone spur formation. The location of the stenosis defines the type of stenosis. There are three main types: central spinal stenosis, lateral recess stenosis, and foraminal stenosis, each of which can happen in any region of the spine (i.e. cervical, thoracic, or lumbar).
Central stenosis is narrowing in the central ring of the spinal vertebrae, the space through which the spinal cord passes. The spinal cord starts in the cervical spine and moves down through the thoracic spine and to a termination point called the conus medullaris, which occurs at about the second level of the lumbar spine. Central canal stenosis is most often found in the cervical and lumbar regions because these regions experience the most motion.
Foraminal stenosis is narrowing at the foramen, the vertebral spaces through which nerves branch off the spinal cord to the left or right and into the body. These provide motor and sensory function in the arms, legs, and torso. Foraminal stenosis is most common in the cervical and lumbar spine because these two regions are involved in movement and the latter also bears the weight of the body. This is the most common form of spinal stenosis.
Lateral recess stenosis is narrowing around the channels that nerves traverse before they exit through the foramen. The lateral recess is where the nerve is generated just off the spinal cord, before moving through the foramen. Stenosis of this type affects nerve that branch off the spinal cord and provide motor function to the arms, legs, and torso.
Stenosis means narrowing; there are multiple changes that can cause a narrowing around neural elements (e.g. the spinal cord or nerve roots). Stenosis is most frequently found in the cervical and lumbar regions due to higher flexibility and range of motion in these regions; the lumbar spine also bears the weight of the body, putting more stress on this region. The stress caused by the motion and weight bearing of the spine puts stress on structures in the spine, such as the intervertebral discs, ligaments, and the facet joints which may lead to spinal stenosis.
Aging and related arthritis is the primary cause of spinal stenosis. Intervertebral discs contain a lot of water and stress from the aging process causes them to dry out, degenerate, and shrink. As discs shrink in size, the space between vertebral bodies and between the foramen, the space through which nerves exit the spinal cord, narrows. In addition, the ligaments and facet joints on the spinal vertebrae increase in size with arthritis which may place pressure on the spinal nerves. The posterior longitudinal ligament, the largest ligament in the central spinal canal, binds the vertebrae together, but an enlarge and thicken, causing the canal to have less space for nerves. Arthritis may also cause the formation of bone spurs, or bony growths, at the facet joints. Often, more than one type of arthritic change is contributing to the symptoms of a pinched nerve.
Disc herniation may also lead to spinal stenosis. Intervertebral discs are formed from two elements: an outer fibrous area and an inner jelly-like area. The outer fibrous portion may weaken or develop small tears with aging, trauma, and weight gain, potentially allowing the inner jelly-like substance to herniate or slip through. Acute trauma is a large amount of force applied to the spine from a single event, for example, from a blunt hit or a motor vehicle accident. Chronic trauma is repeated stress over time, including forces applied by repetitive tasks at work or with recreational activities. Increase in body weight also adds stress on the spine, weakening the discs, and making them more susceptible to a herniation. As the disc herniates, this creates a narrowing around the spinal nerve roots, leading to spinal stenosis.
Structural abnormalities of the spine can also lead to spinal stenosis. The more common structural abnormalities are scoliosis and spondylolisthesis. Scoliosis is an abnormal curvature in the spine which can accelerate the aging process and arthritic changes, leading to spinal stenosis. Spondylolisthesis is an abnormal alignment of spinal vertebrae, when one vertebrae slides forward or backward relative to the vertebrae directly below. As the facet joints of each vertebra in the spine come together, a space called the foramen is created that allows nerves to branch from the spinal cord into the body. If one vertebra is shifted forward relative to the vertebrae below, this causes an abnormal alignment of the facet joints, narrowing the foramen and leading to spinal stenosis.
The symptoms of spinal stenosis range from nonexistent to severe and debilitating. This can depend on the location of the spinal stenosis, amount of compression, and type of spinal stenosis. Spinal stenosis occur most frequently in the cervical and lumbar spine due to their range of motion.
Central stenosis is the narrowing of the central canal, which is the area for which the spinal cord passes. The symptoms of central stenosis are largely the same despite there being several possible causes. Symptoms can vary based upon the spinal region that narrowing occurs in and since spinal stenosis is largely triggered by age related changes, such as arthritis, symptoms tend to have a gradual onset.
Cervical central stenosis is the narrowing or compression of the spinal cord in the neck. Symptoms can be gradual and go unnoticed for a period of time. Common symptoms include neck pain or stiffness, decreased range of motion with a cracking sound as the neck moves, or Lhermitte’s sign, an electrical sensation that shoots down the back and the when the chin moves toward the chest. Other symptoms of central cervical stenosis include myelopathic symptoms, which are neurologic deficits that occur due to compression of the spinal cord. These can manifest as a combination of difficulty with fine motor tasks (such as writing, counting money, and buttoning a shirt), difficulty with walking, and changes in bladder habits. Numbness may occur in the hands, which can decrease the strength of the grip. It is typical for symptoms to not be traced back to cervical spine disease because of the gradual onset. Spinal stenosis and spinal cord compression can have devastating consequences. For example, myelomalacia, bruises on the spinal cord; stingers, a form of temporary paralysis; or in severe cases, total paralysis.
Thoracic and lumbar central stenosis are compression of the spinal cord in the mid, lower back, or as with the case of the termination of the spinal cord into the cauda equina, cauda equina syndrome. Compression of the spinal cord in the thoracic spine can cause myelopathic symptoms, which include unsteady walking and inability to urinate or incontinence. Often there may be localized back pain that accompanies central thoracic stenosis. Similar myelopathic symptoms can occur in the lumbar spine as well and with severe compression, this may lead to permanent damage. For example, the nerves in the cauda equina are responsible for function in the legs and organs within the pelvis, such as the bladder. Compression on the cauda equina, creates symptoms of numbness in the pelvic region or within the sexual organs, weakness in the legs, and loss of bladder or bowel function. This serious medical condition, known as cauda equine syndrome, may lead to permanent loss of bladder control or sexual function without proper treatment.
Lateral foraminal and lateral recess stenosis cause narrowing at different locations in the spine, but both affect the nerve roots that exit branch from the spinal cord. The symptoms that occur are directly related to the location of the stenosis. This can occur in any area of the spine, but most commonly occurs in the cervical and lumbar regions.
Cervical stenosis may occur at any of the eight nerve roots that branch from the spinal cord and symptoms may manifest bilaterally (both left and right) or unilaterally (either left or right). Symptoms commonly consist of localized pain, stiffness, and decreased range of motion in the neck. Typically, foraminal and lateral recess stenosis can cause radiating symptoms, such as weakness, shooting, or stabbing pain, burning, numbness, and/or tingling in the shoulders, arms, and hands. The specific location will depend on the location that the compressed nerve root corresponds to.
C5 nerve root controls the deltoid muscle, which is the muscle on the cap of the shoulder. Stenosis around this nerve may cause shoulder pain possibly weakness of the deltoid muscle.
C6 nerve root controls the bicep muscles and the wrist extensor muscles. Stenosis around this nerve may cause radiating pain on the thumb side of the arm and/or weakness at one or both muscles groups.
C7 nerve root controls the triceps muscles and the wrist flexor muscles. Stenosis around this nerve may cause radiating pain down the back of the arm to the middle finger and/or weakness at one or both muscle groups.
C8 nerve root controls the flexion of the fingers (making a fist). Stenosis around this nerve may cause radiating pain down the pinky side of the arm and/or weakness with grip.
Thoracic stenosis commonly causes localized mid back pain. Radiating symptoms from thoracic stenosis may occur at any of the twelve nerve roots that branch from the spinal cord in the midback. The level that the spinal stenosis occurs will determine where the symptoms occur because the nerves from the thoracic spine run directly above each rib and supply both sensation to the torso and motor strength to the intercostal and abdominal muscles. Compression of these nerves causes a sharp, shooting, stabbing, or electrical pain that radiates around a single rib, typically on one side of the body. In addition, this may cause decreased sensation with numbness or tingling.
Lumbar stenosis frequently causes symptoms of pain, stiffness, and decreased range of motion in the lower back. Pain is usually relieved by leaning forward into the “flexed position” of the lumbar spine. A common symptom of lumbar stenosis is neurogenic claudication, which means that the pain radiates into the legs while walking, but improves with rest, typically by sitting down. Sharp, stabbing, shooting, burning, or electrical pain in the buttocks, hips, legs, or feet is also common; the specific location will depend on the location that the compressed nerve root corresponds to.
L1 nerve root controls the psoas muscle (which aids in actions such as stair climbing) and sensation in the groin and front of the thigh. Stenosis around this nerve may cause Weakness in the psoas muscle and pain in the groin and front of the thigh; the former can cause difficulty with lifting the leg, for example, while walking up stairs.
L2 nerve root controls sensation of the front of the thigh, buttock and control of the iliopsoas muscles, which aids with stair climbing and placing foot forward while walking. Stenosis around this nerve may cause difficulty while walking up the stairs and/or pain that radiates into the front of the thigh.
L3 nerve root controls quadriceps femoris muscles, which are located on the front of the thigh and are responsible for knee extension, or straightening of the leg. Stenosis around this nerve may weakness of quadriceps femoris, which may cause weakness while straightening the leg and/or pain in buttocks that radiates to the lower portion of the front of the thigh.
L4 nerve root innervates the quadriceps femoris muscles and about half of the time also the tibialis anterior muscle. The quadriceps femoris extends the knee, or straightens the leg. The tibialis anterior muscle helps to bring the toes up when walking. Stenosis around this nerve weakness while straightening the knee or lifting the toes when walking, which may lead to a foot drop. Pain may radiate from the buttock to the top of the back of the thigh and then to the front of the shin.
L5 nerve root innervates the tibialis anterior muscle and foot and toe dorsiflexion (which is bringing the toes up toward the face). Stenosis around this nerve may cause a foot drop, or a foot that slaps the ground while walking. Pain may radiate from the buttock, down the back of the thigh and calf, and into the foot, mainly on the inside of the foot.
S1 nerve controls the calf muscles, some of the hamstrings (back of the thigh muscles), and the gluteus maximus (buttock muscle). The calf muscles allow for plantar flexion, or pressing down like on the gas pedal in the car or standing on tip-toes. Stenosis around this nerve weakness with plantar flexion which could cause difficulty or inability to stand on toes and pain that may radiate from the buttock down the back of the leg and into the bottom of the foot’s outside edge.
Patient history and physical examination are typically the first step in diagnosing spinal stenosis. 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 the upper and lower extremities for motor strength, reflexes, and range of motion.
Both history and physical exam contribute to the diagnosis of spinal stenosis, 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 by spinal stenosis. Together history, physical exam, and imaging are all necessary in order to make a correct diagnosis and design an optimal treatment plan for a disc herniation.
Dermatomes are areas of the skin and musculature that a single nerve supplies motor and sensory function to. Based on the location and type of symptom (e.g. radiating or shooting pain, numbness, tingling, or loss of muscle strength) knowledge of dermatomes can help identify which spinal nerve may be affected by spinal stenosis. However, each person is anatomically unique so this is used more as a guide than as a definite diagnostic technique.
Physical exam results that imply a cervical spinal stenosis include decreased range of motion in the neck with difficulty moving the chin toward the chest, leaning the head back, or turning left and right as if checking a blind spot while driving. A specialized test, the Spurling test, tilts the head to the side of the body with symptoms, head slightly leaned back, and then pushing down on the top of the head, which reproduces radiating pain and is considered a positive test. Motor strength testing would be performed on both the upper and lower extremities because weakness in certain muscle groups could imply spinal stenosis at the cervical level where the relevant nerve branches off of the spinal cord. For example, weakness in the deltoid muscle while raising your arms from your sides could indicate spinal stenosis at the C4-5 level. Increases or decreases in the bicep, brachioradialis, or tricep muscle reflexes are commonly used to test for spinal stenosis and can potentially identify the affected spinal level because they are connected to the C5, C6, and C7 nerve roots respectively. Other tests include checking for changes in sensation and a heel to toe walk to evaluate balance.
Physical exams checking for thoracic spinal stenosis will be much less involved than those looking for cervical and lumbar spinal stenosis. The exam typically begins with examining the back for an abnormal curve, uneven muscles, or skin changes such as bruising. After inspection, the doctor will perform palpations over the muscles and center of the back. The legs would be tested for motor strength to ensure that both legs are at full strength and functioning normally. Lastly the physician may check for changes in sensation from one side of the body to the other.
Physical exam abnormalities for the lumbar spine tend to occur exclusively in the lower body. As with evaluating the cervical and thoracic spine, 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 spinal stenosis at the lumbar level where the relevant nerve branches from the spinal cord. For example, spinal stenosis at L3-4 or L4-5 levels may cause weakness with knee extension or straightening the leg. 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 stenosis 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 lumbar spinal stenosis are abnormal walking patterns, including inability to walk on the heels and the toes.
Once spinal stenosis 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.
Though conservative therapy is initiated before surgical therapy in most cases, surgical options are generally used in severe cases of central stenosis in the cervical or thoracic regions and in cases of cauda equina syndrome. Traditional surgical options used large incisions and left a great amount of tissue and muscle disruption, but there are several minimally invasive surgical options for addressing spinal stenosis today. Minimally invasive surgeries are performed through a small incision and without cutting muscle tissue to allow for faster healing and return to normal activities post-operation. The best surgical procedure will be determined by the location of the type of stenosis (i.e. central, foraminal, or lateral recess), spinal region (i.e. cervical, thoracic, or lumbar), and the cause of stenosis. Both decompressive and stabilization procedures may be used.
Certain lifestyle factors may increase the incidence of spinal stenosis, 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 acceleration of the aging process and causing spinal stenosis because of the extra stress is placed on the spinal structures, such as the disc and facet joints. Reducing weight through a low-calorie diet and exercise can reduce pressure on the spine, decreasing the symptoms of spinal stenosis.
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 spinal stenosis. 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 spinal stenosis.
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 disc herniation. 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 spinal stenosis. 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 spinal stenosis. 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.
Cervical Stenosis Treatment
A foraminotomy is a minimally invasive surgical decompression procedure that is performed in the cervical spine to alleviate the compression on a cervical spinal nerve from spinal stenosis. This may be due to bone spur formation or a disc herniation. This procedure is performed through a small midline incision on the back of the neck. A small amount of bone from the back of the vertebrae is removed, called the laminae, so opening for the spinal nerve, the foramen, is reached. The compression is alleviated either by removing disc material or bone spurs that are the source of spinal stenosis. Once the nerve is decompressed, the incision is closed and the procedure is completed.
An ACDF is a minimally invasive surgical stabilization procedure. This is performed through a small incision on the front of the neck. The surgeon tunnels between the thin neck muscles until the spinal column is reached. The old disc is removed and once removed, any contents can be removed around the nerve roots to relieve the spinal stenosis. A special implant with bone graft will then be placed in the disc space with screws to secure placement. Once the procedure is completed, the disc level is fused.
A cervical disc replacement is a minimally invasive surgical stabilization procedure that is performed similarly to the ACDF, however the implant is slightly different, as it preserves some motion of the cervical spine instead of creating a fusion in the ACDF. Spinal stenosis is alleviated through the removal of the disc material or bone spurs.
Thoracic and Lumbar Stenosis Treatment
A microdiscectomy is a minimally invasive surgical decompression procedure that is typically performed on both the thoracic and lumbar spine to address disc herniations, which cause spinal stenosis. A small incision is made in the midline of the back until the backside of the vertebrae, laminae, is reached. At this point, a small amount of the laminae is removed until the spinal nerve is well visualized. The compression on the nerve is removed and once completed, the incision is closed.
Endoscopic discectomy is a minimally invasive surgical decompression procedure that uses specialized instrumentation to remove a disc herniation, which is a source of spinal stenosis. A small incision is made on the midline of the back and the use of specialized imaging, called a fluoroscope is used. 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 dilate the tissue and a retractor is placed over the cylinders and the cylinders are removed. A light source is place down the retractor and instruments are placed down through the retractor to remove the disc fragments pushing on the nerve. The retractor is then repositioned, so that the compression can be removed around the nerve on the opposite side of the body. 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 or bone spurs are 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 procedures used to alleviate the symptoms and structural problems from spinal stenosis are minimally invasive decompressive and stabilization procedures. The spinal nerve roots are decompressed properly any mal-aligned vertebral body is stabilized to prevent further motion. Multiple factors are taken into consideration to plan an appropriate surgical option to treat the structural problems associated with spinal stenosis.
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