This chapter will discuss the different types of pain noted with different neurologic sequelae. Chronic pain treatments and diagnosis of pain syndromes that occur with spinal cord injury, back pain, complex regional pain syndrome, post herpetic pain, and phantom limb pain will be described as will the possible therapies utilized to treat the pain. The differing types of pain associated with each neurologic condition will be described. The treatment of somatic pain from tissue injury and visceral pain from organ systems is described. These types of pain will be contrasted with the neuropathic pain that is the most difficult to treat and is due to damage to the nerve itself. Strategies for treatment of each of these pain types are described as well as the use of multimodal treatment to help minimize the central nervous system side effects while increasing the effectiveness of the various medications.

The goal of this chapter is to give a practical approach to managing some of the more common types of pain in neurologic patients.

There are several issues that should be mentioned that apply to most, if not all, of the neurological patients with chronic pain. While this list of considerations is by no means exhaustive, it can be used to help guide the decision-making process when working with this group of patients.

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  Pain that is persistent and lasts longer than it is expected to last, or pain that is severe should be treated as soon as possible, and if possible, the underlying cause should be remedied.

  
  
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  The longer the pain persists, the more likely it is to become chronic. It is much easier to produce resolution of pain in an acute setting than it is to achieve resolution in long-standing or chronic pain.

  
  
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  In general, chronic pain is treated first with conservative measures and then with progressively more aggressive or invasive measures.

  
  
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  The biggest exception to this is if a patient begins to progressively lose strength or function; in this case rapid intervention may be required.

  
  
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  The mental health of the chronic pain patient should be often considered. Bringing in mental health professionals to assist with patient care is often helpful. In cases of overt suicidal or homicidal ideation, emergent psychiatric consultation is indicated.

A fundamental difference exists in the treatment goals for acute and chronic pain. In acute pain, the acronym RICE is often seen, meaning rest, ice, compression, and elevation, in the setting of acute soft tissue injury. While this works well for acute injury, this is not the case for chronic pain. The focus of chronic pain treatment is to make the patient as functional and active as possible.

While bringing the patient’s pain under control is an important component of treatment, it can be difficult to measure or quantify. Many methods are used for pain self-reporting, including the visual analogue scale and the numerical rating scale. While these are validated and important tools in pain measurement, function is also a very important part of setting up treatment goals and guiding therapy.

The medications used to treat chronic pain are often high risk with regards to side effects and abuse potential. Opioids in specific carry with them an increased level of abuse and misuse.

Some important points to remember when prescribing opioids for patients are covered in detail in another chapter on this book, but deserve a brief mention in this section.

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  It is often helpful to have the patient sign an opioid contract prior to initiation of opioid therapy.

  
  
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  Occasional drug screens help to validate compliance with the treatment protocol that has been established.

  
  
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  Not all patients are chronic opioid candidates. What makes a patient a poor chronic opioid candidate is somewhat controversial, and will vary from practitioner to practitioner.

  
  
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  Pharmacologically a multimodal treatment approach makes sense. It helps to minimize side effects while potentially increasing the effectiveness of various medications.

The four A’s are a useful mnemonic when working with patients who are on opioids or other controlled substance for a longer period of time.¹

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   Analgesia: Is the medication offering some level of pain relief?

   
   
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   Activities of daily living: Is the patient’s activity level/function increasing with pharmacologic intervention and are they able to perform their basic daily routine?

   
   
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   Adverse events/side effects: Is the medication well tolerated, or are the side effects causing more harm than good?

   
   
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   Aberrant behaviors: Is the patient taking the medication as directed, are they requesting early refills, losing prescriptions, obtaining medication from multiple sources, testing positive for illicit substances, or testing negative for drugs you expect to be in the blood or urine (ie, opioids or benzodiazepines you are prescribing)?

What are some of the factors in this case that would be a cause of concern?

Red flags²

The first priority in the workup of a patient with low back pain is to make sure that there are no “red flags” present, or concerning symptoms that need urgent/emergent treatment. Those red flags would be:

Symptoms that would be consistent with cauda equina syndrome:

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  Severe back pain

  
  
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  Bowel or bladder loss of control

  
  
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  Saddle anesthesia

  
  
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  Lower extremity weakness

  
  
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  Severe lower extremity pain

  
  
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  Sexual dysfunction

Other red flags may be the presence of new-onset severe weakness in the lower extremity, which is usually accompanied by some degree of sensory loss

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  Pain that is unrelenting, and can often be worse at rest or at night

  
  
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  Pain that is accompanied by constitutional symptoms: night sweats, fevers, chills, and unexplained weight loss

  
  
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  The patient has a history of systemic illness that predisposes toward a more serious condition with the spine, such as history of cancer, IV drug abuse, immunosupression (various etiologies), or recent or ongoing bacterial infection at an alternate site.

  
  
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  Symptoms of less than 3 months can be associated with a higher-risk, chronic lumbar pain; pain of more than 3-month duration is less likely to be high risk

  
  
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  History of a recent trauma that has incited the pain

  
  
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  Age less than 20 years old or more than 50 years old

Pain that is associated with these issues can often warrant further workup, often in the form of dedicated imaging studies. Of course these symptoms need to be taken in the context of the history and physical examination.

What is the prevalence of low back pain; what about radicular lower extremity pain?²

Lifetime prevalence of low back pain is between 13% and 31%. The incidence of radicular symptoms in these patients is between 12% and 40%. The high variability of these numbers is a reflection of the variability of the existing studies and the various definitions of low back pain.

How would you approach the history and physical portion of the examination?

History

Like any aspect of medicine the history is one of the most crucial aspects of making an accurate diagnosis and formulating an appropriate treatment plan.

Areas of the history that warrant special attention are as follows, with the exception of the red flags, which have previously been covered.

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  The severity of the pain, typically taken on the numerical rating scale or the visual analogue scale, from 0 to 10 on a scale of 10, that is my pain is a 3/10. This can frequently help determine treatment, as someone with mild to moderate pain is able to function more regularly, while someone with severe pain is likely to need more aggressive treatment more rapidly.

  
  
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  Quality of the pain is also integral in making an appropriate diagnosis. Qualities such as burning, searing, shooting, sharp, achy, or stabbing often point toward pain of a neuropathic origin. Pain that is described as crampy, squeezing, or dull can often be associated with myofascial pain.

  
  
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  Exacerbating or alleviating factors often help guide you toward a fairly specific etiology. For example, spinal stenosis is often associated with pain with extension, and so a patient will often find that going down a hill or a set of stairs will exacerbate the pain, while bending forward or the use of a shopping cart while at the grocery store will improve their pain and prolong their ambulation distance. A patient with a lumbar disc herniation often finds that flexion worsens their pain, and so will spend much of their time with the lumbar spine in the extended position.

  
  
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  Referral or radiation of the pain can also be very useful, although it can also complicate the issue of making an accurate diagnosis. It is relatively rare that pain that refers past the knee is not associated with compression or irritation of a lumbar or sacral nerve root. That is to say that almost all pain that starts in the lumbar region and travels to the ankle or foot is lumbar radicular pain.

  
  
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  The inciting event is often helpful with respect to the possible etiology of the pain and may help guide the necessary diagnostic studies needed in the near future.

  
  
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  Acute or chronic exacerbation.

  
  
  
  
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    It should be noted that if the patient has a history of chronic lumbar and/or lower extremity pain there is certainly the possibility of that pain worsening. Some cases are very straightforward, while others can become very complex. But if a patient is stable, with a certain level of pain for a prolonged period of time, and the pain worsens suddenly or over a short period of time, then further investigation is often warranted.

  
  
  
  
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  Past medical history

  
  
  
  
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    This aspect is always important, especially with regards to possible immunosupression, a history of cancer, or an ongoing infection. A history of prior back problems in the past can also help substantially in guiding treatment.

  
  
  
  
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  Past surgical history, allergies, medications (past and present), family history, and social history

  
  
  
  
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    These are all important for various reasons. For example, if a patient has been through an instrumented lumbar fusion in the past with a recent onset of lumbar pain, then a possible hardware failure would be on a short list for a differential diagnosis. A family history of ankylosing spondylitis would make that a more likely diagnosis in a 35-year-old male with progressive lumbar pain. A patient with an active history of IV drug abuse with new-onset severe lumbar pain would be more likely to have osteomylitis than someone without a history of such drug use.

  
  

Physical Examination

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  The physical examination starts with a general observation of the patient, observing their demeanor, the way they are sitting, their affect, and their gait. This will frequently give you a good idea of the severity of the pain as well as the pain’s effect on the patient’s function.

  
  
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  The vital signs of a patient in acute pain can often demonstrate an increase in respiratory rate, heart rate, and blood pressure. This is often not the case for patients with severe chronic pain.

  
  
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  Inspection and palpation of the lumbar spine and surrounding muscles may bring up irregularities such as scoliosis, hyperlordosis, swelling, abscesses, spinous process tenderness, or spinous process step-offs, indicating a possible spondylolisthesis.

  
  
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  Basic range of motion of the lumbar spine with associated degrees of movement for a normal individual.

  
  
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  It should be noted that osteomyelitis or painful compression fractures often show up on examination with painful palpation over the spinous processes.

  
  
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  The neurological examination is covered in detail elsewhere in this book and so will not be covered here. What should be mentioned is that an examination of the lower extremities including strength, sensation, and reflexes should be performed.

  
  
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  An upper extremity examination should also be considered if there is any indication that the patient may have some degree of cervical stenosis or neural impingement, as concomitant cervical and lumbar pathology can certainly make lumbar and lower extremity pain worse than it would be otherwise.

Beyond the basic neurological examination are there other, more specialized tests that may prove helpful (Table 6-1 and Figure 6-1)?

What are some of the treatment options available for this patient?

Bedrest not generally recommended²

Rest for a very brief period is reasonable. It is clear that strict bed rest is ill advised in the case of low back pain, especially if the rest goes beyond a week. It has been shown that patients that resume daily activities and return to work do better than those who avoid activity.

Physical Therapy²

There is some evidence that physical therapy can help decrease low back pain, facilitate a return to work, and potentially reduce the need for surgical intervention. The goals of physical therapy include decreasing pain, improving lumbar range of motion, improving strength, and improving functional status.

The patient should focus therapy in the plane of comfort, meaning if it is painful to flex the lumbar spine then extension-based exercises should be utilized, and vice versa. Therapy should also improve the pain, not worsen the pain.

Pharmacotherapy

While there are several medications that help with pain, in certain circumstances some may prove more useful than the others. The general goal of pharmacotherapy for the patient with low back pain is to get the pain to a reasonable level and to help the patient maintain as normal a level of function as possible. Judgment must be used with initiating medications with regard to side effects, interactions, and treatment goals (Table 6-2).

Are there other options available if more conservative measures fail?

There are several types of steroid injections that can be performed, depending on the suspected diagnosis. In general whatever the injection being considered it should be clear to the patient that steroid injections do not cure the underlying pathology. The reason to consider injections is to potentially help ameliorate the pain and to get the patient back to a reasonable level of function.

In the case of our patient with radicular lower extremity pain, it is relatively likely that his pain is associated with an acute/subacute disc herniation. While there is conflicting evidence on the efficacy of epidural injections in treating low back pain alone, the evidence does point to short-term benefit for relief in the setting of radicular leg pain associated with a lumbar disc herniation.³ It should be noted that advanced imaging is recommended prior to epidural injections, magnetic resonance imaging (MRI) being the preferred modality, although a computed tomography (CT) scan of the lumbar spine can also be appropriate.

There are also several other types of injections that can be performed, depending on the diagnosis and the underlying pathology. Types of injections for low back pain include epidural injections, sacroiliac joint injections, lumbar facet injections, piriformis injections, quadrates lumborum injections, trigger point injections, and intaarticular hip joint injections. Again, similar to epidural injections, these injections do not cure or heal the underlying pathology.

What if the patient is hesitant to undergo steroid injections; are oral steroids a viable option for treatment?

A tapering dose of oral steroids is commonly prescribed for patients with acute radicular pain in the lower extremities. While anecdotally this can help, there is a lack of evidence to support this practice up to this point.⁴

What if the patient’s pain fails to resolve with more conservative measures, is very severe, or is associated with weakness or bowel or bladder incontinence?

There are several reasons to consider surgical consultation for a patient with low back pain. Acute-onset weakness and sensory loss and/or acute loss of bowel or bladder control are a couple of the more clear indications in which emergent surgical consultation should be sought. In the setting of failure of more conservative therapy it is often fruitful to have a discussion with the patient about their goals, expectations, and treatment options prior to surgical consultation.

While there are several different types of lumbar surgeries, some of the more common lumbar surgeries include spinal decompression, spinal fusion, and spinal reconstruction. The specific procedure being considered will be up to the consulting surgeon and the patient.

Are there any other treatment options for the patient who is not a candidate for surgical intervention, not interested in invasive therapeutics, or who does not feel the pain is severe enough for intervention?

There are various treatments available for low back pain. Some are more well studied than others.

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  Chiropractic care has been shown to be effective in the treatment of low back pain.⁵ There does not seem to be an advantage of chiropractic care over traditional modalities.

  
  
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  Acupuncture can offer anecdotal relief of low back pain. A review of the studies involving acupuncture does seem to show moderate relief of back pain, although there is limited evidence to suggest that it offers more relief than sham treatment.⁶

  
  
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  Biofeedback is a modality that attempts to focus conscious attention on the control of musculature in the patient, often using EMG electrodes. There is limited evidence to suggest that this modality offers relief in the chronic or acute setting of low back pain.⁷

  
  
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  Pain psychology can offer assistance for patients with low back pain, especially those patients with chronic pain. Fear of activity in the chronic pain patient can reinforce inactivity and worsen functional status.⁸

What if the patient has been through surgery and the pain remains unresolved, or if for some reason, the patient is not a surgical candidate?

Spinal cord stimulation in the setting of failed back surgery syndrome remains a relatively effective treatment for carefully selected patients.⁹ This modality, much like steroid injections, does not cure the underlying pathology. It is used as a method of increasing function and decreasing pain (Figure 6-2).

Are there specific imaging studies that are better than others for confirming a clinical suspicion?

Plain films of the lumbar spine are easy to obtain and relatively inexpensive. With flexion extension views you are also able to assess the dynamic stability of the spine, which is not something that is offered with more advanced imaging techniques such as an MRI or CT scan.¹⁰ Plain films of the lumbar spine are particularly useful in the setting of bony abnormalities, although soft tissue aberrations can occasionally be noted.

MRI of the lumbar spine is generally considered the gold standard for imaging of the neuraxis. MRIs have superior soft tissue characterization, including that of neural structures and intervertebral discs. MRIs can also be very sensitive for picking up early presentations of infection and cancer. There is no radiation exposure with an MRI, although it is of unknown safety to a fetus.¹⁰ With the use of contrast (gadolinium) MRIs can also help distinguish scar tissue from disc herniations. However, they are expensive tests and not all patients are able to undergo MRIs secondary to metallic implants, metallic foreign bodies, cerebral aneurysm clips, pacemakers (or other medical devices), and claustrophobia (Figure 6-3).¹⁰

CT of the lumbar spine is very good at resolution of the bony structures of the lumbar spine, generally superior to the images produced by a plain film. Resolution of soft tissues, though, is not at the level of an MRI. Radiation exposure is high, much higher than plain radiographs. CT scans are generally considered a reasonable substitute for a lumbar MRI if a patient is not able to undergo an MRI for some reason.

Are there any other diagnostic tests that may prove useful in the setting of low back pain?

Electromyography (EMG) and nerve conduction velocity (NCV) are tests frequently performed during the same consultation and often referred to as just simply EMG, although strictly speaking they are two separate ways of evaluating the nerves. When ordering an EMG/NCV, it is useful to have a specific question in mind.

Complex regional pain syndrome (CRPS) is divided into two types. Many of the definitions are shared between the two types, with the primary difference being that type II is associated with a discrete nerve injury, while type I is often a relatively minor initiating event or injury; at times the injury is not recalled, so onset almost seems spontaneous.¹¹

The hallmark of CRPS is allodynia or hyperalgesia over the affected area. With CRPS type I, the pain is disproportionate to the inciting injury, and in both CRPS types I and II, the affected area is typically not limited to the distribution of one nerve.