Pathophysiology of neck and back pain
Depending on the cause, neck or back pain may be accompanied by neurological or systemic symptoms.
If a nerve root is affected, the pain may radiate distally along the distribution of that root (radicular pain).
Muscle strength, sensitivity and osteo-tendon reflexes in the area innervated by that root may be impaired.
If the spinal cord is affected, both strength and sensitivity and reflexes may be impaired at the affected spinal level and at all lower levels (called segmental neurological deficits).
If the cauda equina is involved, segmental deficits develop in the lumbosacral region, typically with disruption of bowel function (constipation or faecal incontinence) and bladder function (urinary retention or urinary incontinence), loss of perianal sensation, erectile dysfunction, and loss of rectal tone and sphincter reflexes (e.g., bulbocavernous and anal reflexes).
Any painful disorder of the spine may also cause spasm of the paravertebral muscles.
Aetiology of neck and back pain
Most neck and back pain is caused by pathologies of the spinal structures.
Muscle pain is a common symptom and is typically caused by irritation of the deeper muscles by the dorsal branches of the spinal nerve and in the more superficial muscles by a local reaction to spinal injury.
Strains are very rare in the cervical and lumbar spine.
Fibromyalgia may coexist with neck and back pain, but is not likely to be the cause of isolated neck or back pain. Sometimes, pain is associated with extra-rural disorders (particularly vascular, gastrointestinal or genitourinary).
Although uncommon, extra-rhythmic causes may be serious diseases.
Most vertebral causes are mechanical in origin
Only a few involve non-mechanical problems, such as infection, inflammation, neoplasia or fragility fractures due to osteoporosis or cancer.
Neck and back pain, frequent causes
Most pain caused by spinal disorders is due to
- Disc pain
- Nerve root pain
- Arthritis of the joints
The following are the most frequent causes of cervicalgia and lumbago:
- Herniated inter-vertebral disc
- Compression fracture (usually thoracic or lumbar)
- Lumbar and cervical canal stenosis
- Arthrosis of the spine
- Spondylolisthesis
All these disorders may also be present without causing pain.
Various anatomical abnormalities (e.g., a herniated or degenerated inter-vertebral disc, osteophytes, spondylolysis, facet abnormalities) are frequently present in people without neck or back pain, and are therefore questionable as causes of pain.
However, the aetiology of back pain, particularly mechanical back pain, is often multifactorial, with an underlying disorder exacerbated by fatigue, physical deconditioning, muscle pain, poor posture, weakness of stabilising muscles, reduced flexibility and, sometimes, psychosocial stress or psychiatric abnormalities.
Therefore, identifying a single cause is often difficult or even impossible.
A generalised myofascial pain syndrome, such as fibromyalgia, often includes neck pain and/or back pain.
Serious rare causes
Serious causes of neck or back pain may require early diagnosis and timely treatment to prevent morbidity, disability or mortality.
Serious extra-spinal conditions include:
- Abdominal aortic aneurysm
- Aortic dissection
- Dissection of carotid or vertebral artery
- Acute meningitis
- Angina pectoris or myocardial infarction
- Certain gastrointestinal disorders (e.g., cholecystitis, diverticulitis, diverticular abscess, pancreatitis, penetrating gastroduodenal ulcer, retrociecal appendicitis)
- certain pelvic disorders (e.g. extra-uterine pregnancy, ovarian cancer, salpingitis (pelvic inflammatory disease))
- Certain lung diseases (e.g. pleurisy, pneumonia)
- Some urinary tract disorders (e.g. prostatitis, pyelonephritis, nephrolithiasis)
- Metastases from extraspinal cancer
- Inflammatory or infiltrative retroperitoneal disorders (e.g. retroperitoneal fibrosis, immunoglobulin G4-related disease [IgG4-RD], haematoma, adenopathy)
- Muscle inflammatory disorders (e.g. polymyositis and other inflammatory myopathies, polymyalgia rheumatica)
Severe spinal conditions include:
- Infections (e.g. discitis, epidural abscess, osteomyelitis)
- Primary neoplasms (of the spinal cord or vertebrae)
- Neoplasms with vertebral metastases (most often from the breast, lung or prostate)
- Mechanical vertebral diseases can be serious if they compress the nerve roots or, in particular, the spinal cord.
- Spinal cord compressions occur only in the cervical, thoracic and upper lumbar spine and can result from severe spinal stenosis or pathologies such as tumours and spinal epidural abscesses or haematomas.
- Nerve compression commonly occurs at the level of a herniated disc paracentrally or in the foramen, centrally or in the lateral cavity with stenosis, or in the outlet foramen of a nerve.
Other rare causes
Neck or back pain can result from many other disorders, such as
- Paget’s disease of the bone
- Torticollis
- Upper thoracic outlet syndrome
- Temporomandibular joint syndrome
- Herpes zoster (even before the rash)
- Spondyloarthropathies (ankylosing spondylitis most often, enteropathic arthritis, psoriatic arthritis, reactive arthritis and Reiter’s syndrome)
- Injury or inflammation of the brachial or lumbar plexus (e.g., Parsonage Turner syndrome)
Assessment of neck and back pain
General
Since the cause of neck and back pain is often multifactorial, a definitive diagnosis cannot be established in many patients.
However, every effort should be made to determine:
- Whether the pain has a vertebral or extra-vertebral cause.
- If the cause is a serious pathology
If serious causes have been excluded, back pain is sometimes classified as follows:
- Non-specific neck or lower back pain
- Neck pain or low back pain with radicular symptoms
- Lumbar spinal stenosis with claudication (neurogenic) or cervical stenosis with myelopathy
- Neck pain or low back pain associated with another spinal cause
History of neck and back pain
The history of the current disease should include quality, onset, duration, severity, location, radiation, temporal course of the pain, and mitigating and exacerbating factors such as: rest, activity, changes due to position, load, and at various times of the day (e.g., during the night or upon awakening).
Accompanying symptoms to be considered include stiffness, numbness, paresthesias, hyposthenia, incontinence or urinary retention, constipation and faecal incontinence.
The systems review should take note of symptoms that suggest a cause, including fever, sweating, and chills (infection); weight loss and poor appetite (infection or cancer); worsening neck pain on swallowing (oesophageal disorders); anorexia, nausea, vomiting, melena or haematochezia, and changes in bowel or stool function (gastrointestinal disorders); urinary symptoms and flank pain (urinary tract disorders), especially if intermittent, characteristic of colic, and recurrent (nephrolithiasis); coughing, dyspnoea and worsening during inspiration (pulmonary disorders); vaginal bleeding or discharge and pain related to the phase of the menstrual cycle (pelvic disorders); fatigue, depressive symptoms and headaches (multifactorial mechanical neck or back pain).
Remote pathological history includes neck or back disorders (including: osteoporosis, osteoarthritis, disc disorders, and recent or previous injuries); surgery; risk factors for back disorders (e.g., cancers, including breast, prostate, kidney, lung, and colon cancers, as well as leukaemias); risk factors for aneurysm (e.g., smoking and hypertension); risk factors for aneurysm (e.g., smoking and hypertension); and risk factors for aneurysm, smoking and hypertension), risk factors for infection (e.g., immunosuppression, use of EV drugs, recent surgery, haemodialysis, penetrating trauma or bacterial infection); and extra-articular features of an underlying systemic disorder (e.g., diarrhoea or abdominal pain, uveitis, psoriasis).
Objective examination
Temperature and general appearance are noted.
Whenever possible, patients should be observed moving around the room, undressing and climbing onto the couch to assess gait and balance.
The examination focuses on the spine and neurological examination.
If no mechanical spinal source of pain is evident, patients are evaluated by looking for sources of referred or localised pain.
In the evaluation of the spine, the back and neck are examined for any visible deformities, areas of erythema or vesicular rash.
The spine and paravertebral muscles are palpated to assess pain and changes in muscle tone.
The arc of movement is assessed macroscopically.
In patients with neck pain, the shoulders are examined.
In patients with low back pain, the hips are examined.
The neurological examination should assess the function of the entire spinal cord. Strength, sensation, and deep tendon reflexes should be assessed.
Reflex tests are among the most reliable physical examinations to confirm normal spinal cord function.
Dysfunction of the corticospinal tract is indicated by rising toes with plantar response and Hoffman’s sign, most often with hyperreflexia.
To assess Hoffman’s sign, the physician strikes the nail or volar surface of the 3rd finger; if the distal phalanx of the thumb flexes, the test is positive; it usually indicates corticospinal tract dysfunction caused by cervical canal stenosis or brain injury.
Sensory findings are subjective and may be undetectable.
The Lasègue test (elevation of the extended leg) helps to confirm sciatica.
The patient is supine with both knees extended and ankles dorsiflexed.
The doctor slowly lifts the affected leg, keeping the knee extended.
If sciatica is present, from 10 to 60° of elevation the patient feels the typical sciatica pain.
Although the knee is often palpated from behind to assess the presence of sciatica, it is probably not a valid test for this.
For contralateral Lasègue’s sign, the unaffected leg is lifted; the test is positive if sciatica appears in the affected leg. A positive Lasègue sign is sensitive but not specific for herniated discs; the contralateral Lasègue sign is less sensitive but 90% specific.
The seated extended leg lift test is performed while patients are seated with hips flexed at 90°; the leg is slowly raised until the knee is fully extended.
If sciatica is present, the pain in the spine (and often the radicular symptoms) appears when the leg is extended.
In the application of traction on the spinal nerve roots the cone lowering test is similar to the taut leg raising test but is performed with the patient ‘falling’ (with the thoracic and lumbar spine flexed) and the neck flexed while the patient is sitting.
The forced tension test is more sensitive, but less specific, for herniated discs than the outstretched leg lift test.
In the general examination, the pulmonary system is examined.
The abdomen is checked for tenderness, masses and, particularly in patients > 55 years old, a pulsatile mass (suggesting abdominal aortic aneurysm).
With a clenched fist, the doctor percusses the costovertebral angle for tenderness, which suggests the presence of pyelonephritis.
A rectal examination is performed, including examination of the stool for occult blood and, in men, examination of the prostate.
Reflexes and rectal tone are assessed.
In women with symptoms suggestive of pelvic disease or unexplained fever, vaginal exploration is performed.
Pulsatility in the lower limbs is checked.
Warning signs
The following findings are of particular concern:
- Abdominal aorta > 5 cm (especially if painful) or lower limb pulsatility deficits
- Acute, stabbing pain from the upper to mid back
- Cancer, diagnosed or suspected
- Neurological deficits
- Fever or chills
- Gastrointestinal findings such as localised abdominal tenderness, peritoneal signs, melena or haematochezia
- Risk factors for infection (e.g. immunosuppression, use of EV drugs, recent surgery, penetrating trauma or bacterial infection)
- Meningism
- Severe or disabling night pain
- Unexplained weight loss
Interpretation of findings
Although serious extraspinal disorders (e.g. tumours, aortic aneurysms, epidural abscesses, osteomyelitis) rarely cause back pain, they are not uncommon in high-risk patients.
The presence of warning signs should increase suspicion of a serious cause.
Other findings are also helpful. Worsening of pain on flexion is compatible with intervertebral disc disease; worsening on extension suggests spinal stenosis or arthritis affecting the facet joints.
Pain on specific trigger points suggests muscle pain caused by vertebral disorders.
Examinations to assess neck and back pain
Usually, if the duration of pain is short < 4-6 weeks, no testing is necessary unless warning signs are present, patients have had a serious injury (e.g. vehicle accident, fall from height, penetrating trauma) or the assessment suggests a specific non-mechanical cause (e.g. pyelonephritis).
Standard (direct) X-rays can identify most disc height loss, anterior spondylolisthesis, misalignment, osteoporotic (or fragility) fractures, osteoarthritis, and other severe bone abnormalities (e.g., those due to infection or tumour) and may be useful in deciding whether further imaging studies such as MRI or CT are necessary.
However, they do not identify abnormalities in soft tissues (the discs) or nerve tissue (as is the case in many severe disorders).
Examinations are guided by the findings and the suspected cause.
Testing is also indicated in patients who have failed initial treatment or in those whose symptoms have changed.
Tests for specific suspected causes include the following:
- Neurological deficits, particularly those consistent with nerve root or spinal cord compression: MRI and less commonly myelo-CT, performed as soon as possible
- Possible infection: leukocyte count, ESR, imaging (usually MRI or CT), and culture of infected tissue
- Possible cancer: CT or MRI, blood count with formula and possibly biopsy
- Possible aneurysm: CT, angiography, or sometimes ultrasound
- Possible aortic dissection: angiography, CT scan, or MRI
- Symptoms that are disabling or persist > 6 weeks: imaging (usually MRI or CT scan) and, if infection is suspected, leukocyte count and erythrocyte sedimentation rate; some doctors start with antero-posterior and lateral X-rays of the spine to help localise and sometimes diagnose abnormalities
- Other extra-vertebral pathologies: appropriate tests (e.g. chest X-ray for lung pathologies, urine tests for urinary tract pathologies or for back pain without clear mechanical causes)
Treatment of neck and back pain
Underlying disorders are treated.
Acute musculoskeletal pain (with or without radiculopathy) is treated with
- Analgesics
- Lumbar stabilisation and exercise
- Heat and cold
- Modification of activities and rest (up to 48 h) as needed
Analgesics
Acetaminophen (paracetamol) or NSAIDs are the initial choice for analgesic therapy.
Rarely, opioids, with appropriate precautions, may be required for severe acute pain.
Adequate analgesia is important immediately following an acute injury, to help limit the cycle of pain and spasm.
Evidence of the benefit of chronic use is weak or absent, so the duration of opioid use should be limited.
Lumbar stabilisation and exercise
When the acute pain subsides sufficiently for movement to be possible, a programme of cervical or spinal stabilisation is started under the supervision of a physiotherapist.
This programme should be started as soon as possible and includes restoration of movement, exercises that strengthen the paraspinal muscles, as well as instructions on posture in general and in the work environment; the aim is to strengthen the supporting structures of the back and reduce the likelihood of the condition becoming chronic or recurrent.
In low back pain, core (abdominal and lumbar) muscle strengthening is important and often starts with an increase from working on a table in a supine or prone position, to working quadruple (on hands and knees) and finally to standing activities.
Hot and cold
Acute muscle spasms can also be relieved by the application of heat or cold.
Cold is generally preferred to heat during the first 2 days after onset of symptoms.
Ice and cold packs should not be applied directly to the skin. They should be closed (e.g. in plastic bags) and placed on top of a towel or cloth.
The ice is removed after 20 min, then reapplied for 20 min over a period of 60 to 90 min.
This process can be repeated several times in the first 24 h.
Heat, using a heating pad, can be applied for the same periods of time.
Since the skin of the back may be less sensitive to heat, heating pads should be used with caution to prevent burns.
Patients are advised not to use a heating pad at bedtime to avoid prolonged exposure due to falling asleep with the pad still on their back.
Diathermy can help reduce muscle spasm and pain after the acute phase.
Corticosteroids
In patients with severe radicular symptoms and low back pain, some physicians recommend a course of oral corticosteroids or an early specialist-guided approach to epidural injection therapy.
However, the evidence supporting the use of systemic and epidural corticosteroids is controversial.
If epidural corticosteroid injection is planned, physicians should obtain an MRI prior to injection so that the condition can be identified, localised and optimally treated.
Muscle relaxants
Oral muscle relaxants (e.g. cyclobenzaprine, methocarbamol, metaxalone, benzodiazepines) have controversial efficacy.
The benefits of these drugs should always be weighed against their potential effects on the central nervous system and other adverse effects, particularly in elderly patients who may present with more severe adverse events.
Myorelaxants should be restricted to patients with visible and palpable muscle spasm and used for no longer than 72 h, except in some patients with central pain syndrome (e.g. fibromyalgia) in whom cyclobenzaprine administered at night may facilitate sleep and reduce pain.
Rest and immobilisation
After a short initial period (e.g. 1-2 days), reduction of activity for comfort, prolonged bed rest, spinal tractions and corsets are of no benefit.
Patients with neck pain may benefit from a cervical collar and a shaped pillow until the pain is reduced, and then they can participate in a stabilisation programme.
Spinal manipulation
Spinal manipulations can help relieve pain caused by muscle spasm or an acute neck or back injury; however, high-speed manipulation may present risks for patients over 55 years of age (e.g., vertebral artery injury from neck manipulation) and for those with severe disc disease, cervical arthritis, cervical stenosis, or severe osteoporosis.
Reassurance
Clinicians should reassure patients with acute non-specific musculoskeletal low back pain that the prognosis is good and that activity and exercise are safe even when they may cause discomfort.
Doctors should be thorough, kind, firm and refrain from making judgements.
If depression persists for several months or a secondary gain is suspected, a psychological evaluation should be considered.
Elements of geriatrics
Low back pain affects 50% of adults > 60 years old.
An abdominal aortic aneurysm should be suspected (perform CT scan or ultrasound) in any elderly patient with non-traumatic low back pain, especially in smokers or hypertensive patients, even if there are no objective findings to suggest this diagnosis.
Imaging of the spine may be appropriate for elderly patients (e.g. to exclude cancer), even when the cause appears to be simple back pain of musculoskeletal origin.
The use of oral muscle relaxants (e.g., cyclobenzaprine) and opioids has controversial efficacy; anticholinergic, central nervous system and other adverse effects may outweigh potential benefits in elderly patients.
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Source:
MSD
