Multisegmental innervation is the second mechanism used to explain pain patterns of a viscerogenic source (Fig. 3-3). The autonomic nervous system (ANS) is part of the peripheral nervous system. As shown in this diagram, the viscera have multisegmental innervations. The multiple levels of innervation of the heart, bronchi, stomach, kidneys, intestines, and bladder are demonstrated clearly.

Fig. 3-3 Sympathetic (A) and parasympathetic (B) divisions of the autonomic nervous system. The visceral afferent fibers mediating pain travel with the sympathetic nerves, except for those from the pelvic organs, which follow the parasympathetics of the pelvic nerve. Major visceral organs have multisegmental innervations overlapping innervations of somatic structures. Visceral pain can be referred to the corresponding somatic area because sensory fibers for the viscera and somatic structures enter the spinal cord at the same levels converging on the same neurons. (From Levy MN, Koeppen BM: Berne and Levy principles of physiology, ed 4, St. Louis, 2006, Mosby.)

There is new evidence to support referred visceral pain to somatic tissues based on overlapping or same segmental projections of spinal afferent neurons to the spinal dorsal horn. This concept is referred to as visceral-organ cross-sensitization. The mechanism is likely to be sensitization of viscera-somatic convergent neurons.¹²

For the first time ever, scientists showed that individuals diagnosed with multiple visceral problems obtained relief from pain in all organ systems with overlapping segmental projections when only one visceral area was treated. In other words, nontreated visceral disease significantly decreased when one viscera of the overlapping segments was addressed. For groups of people with no overlapping segments, spontaneous relief of referred pain was not obtained until and unless all involved visceral systems were treated.¹²

Pain of a visceral origin can be referred to the corresponding somatic areas. The example of cardiac pain is a good one. Cardiac pain is not felt in the heart, but is referred to areas supplied by the corresponding spinal nerves.

Instead of actual physical heart pain, cardiac pain can occur in any structure innervated by C3 to T4 such as the jaw, neck, upper trapezius, shoulder, and arm. Pain of cardiac and diaphragmatic origin is often experienced in the shoulder, in particular, because the C5 spinal segment supplies the heart, respiratory diaphragm, and shoulder.

Direct Pressure and Shared Pathways

A third and final mechanism by which the viscera refer pain to the soma is the concept of direct pressure and shared pathways (Fig. 3-4). As shown in this illustration, many of the viscera are near the respiratory diaphragm. Any pathologic process that can inflame, infect, or obstruct the organs can bring them in contact with the respiratory diaphragm.

Fig. 3-4 Direct pressure from any inflamed, infected, or obstructed organ in contact with the respiratory diaphragm can refer pain to the ipsilateral shoulder. Note the location of each of the viscera. The spleen is tucked up under the diaphragm on the left side so any impairment of the spleen can cause left shoulder pain. The tail of the pancreas can come in contact with the diaphragm on the left side potentially causing referred pain to the left shoulder. The head of the pancreas can impinge the right side of the diaphragm causing referred pain to the right side. The gallbladder (not shown) is located up under the liver on the right side with corresponding right referred shoulder pain possible. Other organs that can come in contact with the diaphragm in this way include the heart and the kidneys.

Anything that impinges the central diaphragm can refer pain to the shoulder and anything that impinges the peripheral diaphragm can refer pain to the ipsilateral costal margins and/or lumbar region (Fig. 3-5).

Fig. 3-5 Irritation of the peritoneal (outside) or pleural (inside) surface of the central area of the respiratory diaphragm can refer sharp pain to the upper trapezius muscle, neck, and supraclavicular fossa. The pain pattern is ipsilateral to the area of irritation. Irritation of the peripheral portion of the diaphragm can refer sharp pain to the costal margins and lumbar region (not shown).

This mechanism of referred pain through shared pathways occurs as a result of ganglions from each neural system gathering and sharing information through the cord to the plexuses. The visceral organs are innervated through the ANS. The ganglions bring in information from around the body. The nerve plexuses decide how to respond to this information (what to do) and give the body finely-tuned, local control over responses.

Plexuses originate in the neck, thorax, diaphragm, and abdomen, terminating in the pelvis. The brachial plexus supplies the upper neck and shoulder while the phrenic nerve innervates the respiratory diaphragm. More distally, the celiac plexus supplies the stomach and intestines. The neurologic supply of the plexuses is from parasympathetic fibers from the vagus and pelvic splanchnic nerves.⁴

The plexuses work independently of each other but not independently of the ganglia. The ganglia collect information derived from both the parasympathetic and the sympathetic fibers. The ganglia deliver this information to the plexuses; it is the plexuses that provide fine, local control in each of the organ systems.⁴

For example, the lower portion of the heart is in contact with the center of the diaphragm. The spleen on the left side of the body is tucked up under the dome of the diaphragm. The kidneys (on either side) and the pancreas in the center are in easy reach of some portion of the diaphragm.

The body of the pancreas is in the center of the human body. The tail rests on the left side of the body. If an infection, inflammation, or tumor or other obstruction distends the pancreas, it can put pressure on the central part of the diaphragm.

Since the phrenic nerve (C3-5) innervates the central zone of the diaphragm, as well as part of the pericardium, the gallbladder, and the pancreas, the client with impairment of these viscera can present with signs and symptoms in any of the somatic areas supplied by C3-5 (e.g., shoulder).

In other words, the person can experience symptoms in the areas innervated by the same nerve pathways. So a problem affecting the pancreas can look like a heart problem, a gallbladder problem, or a mid-back/scapular or shoulder problem.

Most often, clients with pancreatic disease present with the primary pain pattern associated with the pancreas (i.e., left epigastric pain or pain just below the xiphoid process). The somatic presentation of referred pancreatic pain to the shoulder or back is uncommon, but it is the unexpected, referred pain patterns that we see in a physical or occupational therapy practice.

Another example of this same phenomenon occurs with peritonitis or gallbladder inflammation. These conditions can irritate the phrenic endings in the central part of the diaphragmatic peritoneum. The client can experience referred shoulder pain due to the root origin shared in common by the phrenic and supraclavicular nerves.

Not only is it true that any structure that touches the diaphragm can refer pain to the shoulder, but even structures adjacent to or in contact with the diaphragm in utero can do the same. Keep in mind there has to be some impairment of that structure (e.g., obstruction, distention, inflammation) for this to occur (Case Example 3-1).

Case Example 3-1 Mechanism of Referred Pain

A 72-year-old woman has come to physical therapy for rehabilitation after cutting her hand and having a flexor tendon repair. She uses a walker to ambulate, reports being short of breath “her whole life,” and takes the following prescription and over-the-counter (OTC) medications:

• Ibuprofen “on bad days”

• Furosemide

• And one other big pill once a week on Sunday “for my bones”

During the course of evaluating and treating her hand, she reports constant, aching pain in her right shoulder and a sharp, tingling, burning sensation behind her armpit (also on the right side). She does not have any associated bowel or bladder signs and symptoms, but reports excessive fatigue “since the day I was born.”

You suspect the combination of Feldene and Ibuprofen along with long-term use of Vioxx may be a problem.

What Is the Most Likely Mechanism of Pain: Embryologic Development, Multisegmental Innervation of the Stomach and Duodenum, or Direct Pressure on the Diaphragm?

Even though Vioxx is a cyclooxygenase-2 (COX-2) inhibitor and less likely to cause problems, gastritis and gastrointestinal (GI) bleeding are still possible, especially with chronic long-term use of multiple nonsteroidal antiinflammatory drugs (NSAIDs).

Retroperitoneal bleeding from peptic ulcer can cause referred pain to the back at the level of the lesion (T6-10) or right shoulder and/or upper trapezius pain. Shoulder pain may be accompanied by sudomotor changes such as burning, gnawing, or cramping pain along the lateral border of the scapula. The scapular pain can occur alone as the only symptom.

Side effects of NSAIDs can also include fatigue, anxiety, depression, paresthesia, fluid retention, tinnitus, nausea, vomiting, dry mouth, and bleeding from the nose, mouth, or under the skin. If peritoneal bleeding is the cause of her symptoms, the mechanism of pain is blood in the posterior abdominal cavity irritating the diaphragm through direct pressure.

Be sure to take the client’s vital signs and observe for significant changes in blood pressure and pulse. Poor wound healing and edema (sacral, pedal, hands) may be present. Ask if the same doctor prescribed each medication and if her physician (or physicians) knows which medications she is taking. It is possible that her medications have not been checked or coordinated from before her hospitalization to the present time.

^*Removed from the market in 2004 by Merck & Co., Inc., due to reports of increased risk of cardiovascular events.

Assessment of Pain and Symptoms

The interviewing techniques and specific questions for pain assessment are outlined in this section. The information gathered during the interview and examination provides a description of the client that is clear, accurate, and comprehensive. The therapist should keep in mind cultural rules and differences in pain perception, intensity, and responses to pain found among various ethnic groups.¹³

Measuring pain and assessing pain are two separate issues. A measurement assigns a number or value to give dimension to pain intensity.¹⁴ A comprehensive pain assessment includes a detailed health history, physical exam, medication history (including nonprescription drug use and complementary and alternative therapies), assessment of functional status, and consideration of psychosocial-spiritual factors.¹⁵

The portion of the core interview regarding a client’s perception of pain is a critical factor in the evaluation of signs and symptoms. Questions about pain must be understood by the client and should be presented in a nonjudgmental manner. A record form may be helpful to standardize pain assessment with each client (Fig. 3-6).

Fig. 3-6 Pain Assessment Record Form. Use this form to complete the pain history and obtain a description of the pain pattern. The form is printed in the Appendix for your use. This form may be copied and used without permission. (From Carlsson AM: Assessment of chronic pain. I. Aspects of the reliability and validity of the visual analogue scale, Pain 16(1):87–101, 1983. Used with permission.)

To elicit a complete description of symptoms from the client, the physical therapist may wish to use a term other than pain. For example, referring to the client’s symptoms or using descriptors such as hurt or sore may be more helpful with some individuals. Burning, tightness, heaviness, discomfort, and aching are just a few examples of other possible word choices. The use of alternative words to describe a client’s symptoms may also aid in refocusing attention away from pain and toward improvement of functional abilities.

If the client has completed the McGill Pain Questionnaire (see discussion of McGill Pain Questionnaire in this chapter),¹⁶ the physical therapist may choose the most appropriate alternative word selected by the client from the list to refer to the symptoms (Table 3-1).

TABLE 3-1

Recognizing Pain Patterns

From Melzack R: The McGill Pain Questionnaire: major properties and scoring methods, Pain 1:277, 1975.

Pain Assessment in the Older Adult

Pain is an accepted part of the aging process, but we must be careful to take the reports of pain from older persons as serious and very real and not discount the symptoms as part of aging. Well over half of the older adults in the United States report chronic joint symptoms.¹⁷ We are likely to see pain more often as a key feature among older adults as our population continues to age.

The American Geriatrics Society (AGS) reports the use of over-the-counter (OTC) analgesic medications for pain, aching, and discomfort is common in older adults along with routine use of prescription drugs. Many older adults have taken these medications for 6 months or more.¹⁸

Older adults may avoid giving an accurate assessment of their pain. Some may expect pain with aging or fear that talking about pain will lead to expensive tests or medications with unwanted side effects. Fear of losing one’s independence may lead others to underreport pain symptoms.¹⁹

Sensory and cognitive impairment in older, frail adults makes communication and pain assessment more difficult.¹⁸ The client may still be able to report pain levels reliably using the visual analogue scales in the early stages of dementia. Improving an older adult’s ability to report pain may be as simple as making sure the client has his or her glasses and hearing aid.

The Verbal Descriptor Scale (VDS) (Box 3-1) may be the most sensitive and reliable among older adults, including those with mild-to-moderate cognitive impairment.²⁰ But these and other pain scales rely on the client’s ability to understand the scale and communicate a response. As dementia progresses, these abilities are lost as well.

Box 3-1 Verbal Descriptor Scale (VDS)

Directions: Show the scale to your client. Read the descriptors and ask the client to point to the one that best matches his or her pain (achiness, soreness, or discomfort) today. Give the client at least 30 seconds to respond. A verbal reply is acceptable. It is best if the client is sitting upright facing the interviewer. Provide the client with good lighting, his or her eyeglasses, and/or hearing aid(s) if appropriate.

6 = PAIN AS BAD AS IT CAN BE

A client with Alzheimer’s-type dementia loses short-term memory and cannot always identify the source of recent painful stimuli.21,22 The Alzheimer’s Discomfort Rating Scale may be more helpful for older adults who are unable to communicate their pain.²³ The therapist records the frequency, intensity, and duration of the client’s discomfort based on the presence of noisy breathing, facial expressions, and overall body language.

Another tool under investigation is the Pain Assessment in Advanced Dementia (PAINAD) scale. The PAINAD scale is a simple, valid, and reliable instrument for measurement of pain in noncommunicative clients developed by the same author as the Alzheimer’s Discomfort Rating Scale.²⁴ A disadvantage of this pain scale is that the pain is inferred by the examiner or caregiver rather than self-reported directly by the individual experiencing the pain.²⁵

Facial grimacing; nonverbal vocalization such as moans, sighs, or gasps; and verbal comments (e.g., ouch, stop) are the most frequent behaviors among cognitively impaired older adults during painful movement (Box 3-2). Bracing, holding onto furniture, or clutching the painful area are other behavioral indicators of pain. Alternately, the client may resist care by others or stay very still to guard against pain caused by movement.²⁶

Box 3-2 Symptoms of Pain in Clients with Cognitive Impairment

• Verbal comments such as ouch or stop

• Nonverbal vocalizations (e.g., moans, sighs, gasps)

• Facial grimacing or frowning

• Audible breathing independent of vocalization (labored, short or long periods of hyperventilation)

• Agitation or increased confusion

• Unable to be consoled or distracted

• Bracing or holding onto furniture

• Decreased mobility

• Lying very still, refusing to move

• Clutching the painful area

• Resisting care provided by others, striking out, pushing others away

• Sleep disturbance

• Weight loss

• Depression

Untreated pain in an older adult with advanced dementia can lead to secondary problems such as sleep disturbances, weight loss, dehydration, and depression. Pain may be manifested as agitation and increased confusion.²¹

Older adults are more likely than younger adults to have what is referred to as atypical acute pain. For example, silent acute myocardial infarction (MI) occurs more often in the older adult than in the middle-aged to early senior adult. Likewise, the older adult is more likely to experience appendicitis without any abdominal or pelvic pain.²⁷

Pain Assessment in the Young Child

Many infants and children are unable to report pain. Even so the therapist should not underestimate or prematurely conclude that a young client is unable to answer any questions about pain. Even some clients (both children and adults) with substantial cognitive impairment may be able to use pain-rating scales when explained carefully.²⁸

The Faces Pain Scale (FACES or FPS) for children (see Fig. 3-6) was first presented in the 1980s.²⁹ It has since been revised (FPS-R)³⁰ and presented concurrently by other researchers with similar assessment measures.³¹

Most of the pilot work for the FPS was done informally with children from preschool through young school age. Researchers have used the FPS scale with adults, especially the elderly, and have had successful results. Advantages of the cartoon-type FPS scale are that it avoids gender, age, and racial biases.³²

Research shows that use of the word “hurt” rather than pain is understood by children as young as 3 years old.33,34 Use of a word such as “owie” or “ouchie” by a child to describe pain is an acceptable substitute.³² Assessing pain intensity with the FPS scale is fast and easy. The child looks at the faces, the therapist or parent uses the simple words to describe the expression, and the corresponding number is used to record the score.

A review of multiple other measures of self-report is also available,¹⁴ as well as a review of pain measures used in children by age, including neonates.³⁵

When using a rating scale is not possible, the therapist may have to rely on the parent or caregiver’s report and/or other measures of pain in children with cognitive or communication impairments and physical disabilities. Look for telltale behavior such as lack of cooperation, withdrawal, acting out, distractibility, or seeking comfort. Altered sleep patterns, vocalizations, and eating patterns provide additional clues.

In very young children and infants, the Child Facial Coding System (CFCS) and the Neonatal Facial Coding System (NFCS) can be used as behavioral measures of pain intensity.36,37

Facial actions and movements, such as brow bulge, eye squeeze, mouth position, and chin quiver, are coded and scored as pain responses. This tool has been revised and tested as valid and reliable for use postoperatively in children ages 0 to 18 months following major abdominal or thoracic surgery.³⁸

Vital signs should be documented but not relied upon as the sole determinant of pain (or absence of pain) in infants or young children. The pediatric therapist may want to investigate other pain measures available for neonates and infants.39,40

Characteristics of Pain

It is very important to identify how the client’s description of pain as a symptom relates to sources and types of pain discussed in this chapter. Many characteristics of pain can be elicited from the client during the Core Interview to help define the source or type of pain in question. These characteristics include:

• Location

• Description of sensation

• Intensity

• Duration

• Frequency and duration

• Pattern

Other additional components are related to factors that aggravate the pain, factors that relieve the pain, and other symptoms that may occur in association with the pain. Specific questions are included in this section for each descriptive component. Keep in mind that an increase in frequency, intensity, or duration of symptoms over time can indicate systemic disease.

Location of Pain

Follow-Up Questions

• Show me exactly where your pain is located.

Follow-up questions may include:

• Do you have any other pain or symptoms anywhere else?

• If yes, what causes the pain or symptoms to occur in this other area?

If the client points to a small, localized area and the pain does not spread, the cause is likely to be a superficial lesion and is probably not severe. If the client points to a small, localized area but the pain does spread, this is more likely to be a diffuse, segmental, referred pain that may originate in the viscera or deep somatic structure.

The character and location of pain can change and the client may have several pains at once, so repeated pain assessment may be needed.

Description of Pain

To assist the physical therapist in obtaining a clear description of pain sensation, pose the question:

Follow-Up Questions

• What does it feel like?

After giving the client time to reply, offer some additional choices in potential descriptors. You may want to ask: Is your pain/Are your symptoms:

• Knifelike	• Dull
• Boring	• Burning
• Throbbing	• Prickly
• Deep aching	• Sharp

Follow-up questions may include:

• Has the pain changed in quality since it first began?

• Changed in intensity?

• Changed in duration (how long it lasts)?

When a client describes the pain as knifelike, boring, colicky, coming in waves, or a deep aching feeling, this description should be a signal to the physical therapist to consider the possibility of a systemic origin of symptoms. Dull, somatic pain of an aching nature can be differentiated from the aching pain of a muscular lesion by squeezing or by pressing the muscle overlying the area of pain. Resisting motion of the limb may also reproduce aching of muscular origin that has no connection to deep somatic aching.

Intensity of Pain

The level or intensity of the pain is an extremely important but difficult component to assess in the overall pain profile. Psychologic factors may play a role in the different ratings of pain intensity measured between African Americans and Caucasians. African Americans tend to rate pain as more unpleasant and more intense than whites, possibly indicating a stronger link between emotions and pain behavior for African Americans compared with Caucasians.⁴¹

The same difference is observed between women and men.42,43 Likewise, pain intensity is reported as less when the affected individual has some means of social or emotional support.⁴⁴

Assist the client with this evaluation by providing a rating scale. You may use one or more of these scales, depending on the clinical presentation of each client (see Fig. 3-6). Show the pain scale to your client. Ask the client to choose a number and/or a face that best describes his or her current pain level. You can use this scale to quantify symptoms other than pain such as stiffness, pressure, soreness, discomfort, cramping, aching, numbness, tingling, and so on. Always use the same scale for each follow-up assessment.

The Visual Analog Scale (VAS)45,46 allows the client to choose a point along a 10-cm (100 mm) horizontal line (see Fig. 3-6). The left end represents “No pain” and the right end represents “Pain as bad as it could possibly be” or “Worst Possible Pain.” This same scale can be presented in a vertical orientation for the client who must remain supine and cannot sit up for the assessment. “No pain” is placed at the bottom, and “Worst pain” is put at the top.

The VAS scale is easily combined with the numeric rating scale with possible values ranging from 0 (no pain) to 10 (worst imaginable pain). It can be used to assess current pain, worst pain in the preceding 24 hours, least pain in the past 24 hours, or any combination the clinician finds useful.

The Numeric Rating Scale (NRS; see Fig. 3-6) allows the client to rate the pain intensity on a scale from 0 (no pain) to 10 (the worst pain imaginable). This is probably the most commonly used pain rating scale in both the inpatient and outpatient settings. It is a simple and valid method of measuring pain.

Although the scale was tested and standardized using 0 to 10, the plus is used for clients who indicate the pain is “off the scale” or “higher than a 10.” Some health care professionals prefer to describe 10 as “worst pain experienced with this condition” to avoid needing a higher number than 10.

This scale is especially helpful for children or cognitively impaired clients. In general, even adults without cognitive impairments may prefer to use this scale.

An alternative method provides a scale of 1 to 5 with word descriptions for each number ¹⁶ and asks:

Follow-Up Questions

• How strong is your pain?

This scale for measuring the intensity of pain can be used to establish a baseline measure of pain for future reference. A client who describes the pain as “excruciating” (or a 5 on the scale) during the initial interview may question the value of therapy when several weeks later there is no subjective report of improvement.

A quick check of intensity by using this scale often reveals a decrease in the number assigned to pain levels. This can be compared with the initial rating, thus providing the client with assurance and encouragement in the rehabilitation process. A quick assessment using this method can be made by asking:

Follow-Up Questions

• How strong is your pain?

1 = Mild

2 = Moderate

3 = Severe

The description of intensity is highly subjective. What might be described as “mild” for one person could be “horrible” for another person. Careful assessment of the person’s nonverbal behavior (e.g., ease of movement, facial grimacing, guarding movements) and correlation of the person’s personality with his or her perception of the pain may help to clarify the description of the intensity of the pain. Pain of an intense, unrelenting (constant) nature is often associated with systemic disease.

The 36-Item Short-Form Health Survey discussed in Chapter 2 includes an assessment of bodily pain along with a general measure of health-related quality of life. Nurses often use the PQRST mnemonic to help identify underlying pathology or pain (Box 3-3).

Box 3-3 Nursing Assessment of Pain (PQRST)