Chapter 3. Pain Pathophysiology Flashcards

Question

115. Which of the following statements regarding repetitive strain injuries is true? (A) Repetitive strain injury does not include the specific disorder cubital tunnel syndrome (B) Repetitive strain injury is a controversial diagnosis partially because there are few studies showing an association between physical risk factors and injury (C) Psychosocial factors are more clearly correlated than physical risk factors in repetitive strain injury (D) The “unifying hypothesis” of repetitive strain injury states that most often these diseases can be demonstrated to be due to focal injury (E) All of the above

Answer 1

115. (B) A. Repetitive strain injury includes specific disorders such as CTS, cubital tunnel syndrome, Guyon canal syndrome, lateral epicondylitis, and tendonitis of the wrist or hand. B. Ample evidence exists for the association between physical risk factors such as repetitive movements, poor posture, and inadequate strength and the occurrence of repetitive strain injury. C. The effects of work-related and psychosocial factors are not as clear as those of physical factors, although high workload, stress, and physical or psychological demands, low job security, and little support from colleagues might be important. D. Several hypotheses for the pathophysiology of repetitive strain injury exist, but none has been strongly supported by scientific evidence. Despite initial distal presentation, this disorder seems to be a diffuse neuromuscular illness. Mechanical (elastic deformation of connective tissue due to increased pressure within muscles) and physiological (electrochemical and metabolic imbalances) reactions might cause damage to muscle tissue and lead to complaints of strain. Continuous contraction of muscles from long-term static load with insufficient breaks could result in reduced local blood circulation and muscle fatigue. Consequently, pain sensors in the muscles could become hypersensitive, leading to a pain response at low levels of stimulation. Other hypotheses suggest frequent cocontractions in muscles or changes in proprioception as the source of injury. There is no unifying hypothesis.

Answer 2

116. (D) A. Chronic pain following surgical procedures for breast cancer was once thought to be rare. The results of recent studies, however, suggest that the incidence of chronic pain following breast cancer surgery may be more than 50%. Although most surgical advances are less invasive and have fewer complications, the rapid pace of change in treatment complicates outcome research. B. Peripheral neuropathy, often painful, is common after paclitaxel, a second-line therapy for metastatic disease, and also occurs with other chemotherapeutic agents. The incidence of peripheral neuropathy is lower with platinum compounds like cisplatin. C. Sensory neuropathies are more common in chemotherapy than motor neuropathies. D. Axillary dissection poses risks to the intercostobrachial nerve, from stretch during retraction as well as from frank transection. Many patients will be left with an area of numbness on the upper inner arm, signifying damage to the intercostobrachial nerve, but only a minority of these will be painful. Other nerves at risk for damage from axillary dissection include the medial cutaneous nerve of the arm, which contains fibers from C8 and T1 and arises from the medial cord of the brachial plexus. It can be harmed during section of the tributaries of the axillary vein, leaving patients with sensory loss on the lower medial skin of the upper arm. Pain accompanied by sensory loss in one of these areas provides the basis for a diagnosis of injury to these specific nerves.

Answer 3

117. (C) A. Peripheral nerves are composed of largeand small-diameter nerve fibers. Symptoms associated with large-diameter nerve fiber dysfunction include weakness, numbness, tingling, and loss of balance, while those associated with small-diameter nerve fiber damage include pain, anesthesia to pin and temperature sensation, and autonomic dysfunction (eg, changes in local vasoregulation). B. Diabetes duration and blood sugar control correlate with the development of neuropathy. C. Neuropathy with a predilection for smalldiameter nerve fibers can appear with impaired glucose tolerance, a prediabetic state that does not meet the criteria for diabetes mellitus as defined by the American Diabetes Association. Although this neuropathy is usually milder than the neuropathy seen in frank diabetes mellitus, impaired glucose tolerance has been associated with severe painful polyneuropathy without another known etiology. D. As these painful symptoms often result from small-diameter nerve fiber dysfunction, patients may have accompanying abnormalities of autonomic function in the feet (eg, decreased sweating, dry skin, and impaired vasomotor control).

Answer 4

118. (C) A. Reactivation of the varicella-zoster virus can cause dermatomal pain without a rash in a process termed “zoster sine herpete.” This cannot be made on the basis of clinical presentation alone and would require evidence of concurrent viral reactivation. B. Zoster reactivation typically occurs once for an individual. Atypical manifestations that occur in immunocompromised patients include prolonged course, recurrent lesions, and involvement of multiple dermatomes. Diagnostic laboratory tests are recommended when herpes simplex must be ruled out (eg, recurrent rash or sacral lesions) and for patients with atypical lesions. C. Until recently, these definitions have been arbitrary, but the results of recent research now provide support for the validity of distinguishing between three phases of pain in affected and adjacent dermatomes: (1) herpes zoster acute pain (also termed acute herpetic neuralgia), defined as pain that occurs within 30 days after rash onset; (2) subacute herpetic neuralgia, defined as pain that persists beyond the acute phase but that resolves before the diagnosis of PHN can be made; and (3) PHN, defined as pain that persists 120 days or more after rash onset. D. It can also be predicted that the number of adults developing herpes zoster in the United States may increase as a consequence of reduced opportunities for subclinical immune boosting resulting from near-universal varicella vaccination of children. Recent data showing an increase in herpes zoster in the United States are consistent with this prediction. An increase in the incidence of herpes zoster could be offset by zoster vaccination, but the extent to which widespread herpes zoster vaccination will occur is presently unknown.

Answer 5

119. (D) This patient has evidence of having an intrathecal pump with granuloma formation. A. There is a strong relationship between higher doses of intrathecal morphine and granuloma formation. The notion that high-dose morphine is causative is not universally accepted. Some authors have suggested that long-term administration of opiates may lead to localized fibrosis and the formation of a granulomatous mass surrounding the catheter tip. B. There have been cases of granuloma formation reported involving the intrathecal infusion of baclofen. These lesions did not appear to cause any compression of the spinal cord or neurological deficits, resolved when the catheter tip was replaced, and could represent a different disease process. C. Microscopic pathology of intrathecal morphine related granulomas often reveals necrotic tissue surrounded by macrophages, plasma cells, eosinophils, or lymphocytes. Nearby vessels may be surrounded by mononuclear inflammatory cells consisting predominantly of plasma cells. Gross pathologic examination of catheter tip granulomas related to intrathecal morphine infusions often demonstrates the mass conforming to the distal portion of the catheter. D. Because of its (morphine) hydrophilic structure, it has a prolonged duration of action and due to the drug’s high localization; its analgesic effect is maximized at a lower dose. This results in a lower incidence of systemic side effects, reduces drug dependence, and does not significantly influence motor, sensory, or sympathetic reflexes.

Answer 6

120. (C) A. In the three studies that looked at the causes of FBSS, the most common structural causes of FBSS are foraminal stenosis (25%- 29%), painful disc (20%-22%), pseudarthrosis (14%), neuropathic pain (10%), recurrent disc herniation (7%-12%), iatrogenic instability (5%), facet pain (3%), and sacroiliac joint (SIJ) pain (2%), among some others. B. Most patients with refractory low-back pain have symptoms of at least one major psychiatric disorder, most commonly depression, substance abuse disorder or anxiety disorder. Pure psychogenic pain (pain disorder, psychological type) is rare in patients with FBSS. All patients have some pain behavior, which may be appropriate or inappropriate. C. In patients with chronic pain, an improvement in visual analog scale (VAS) score of 1.8 U, equivalent to a change in pain of about 30%, may be considered a satisfactory result. D. FBSS is a nonspecific term that implies that the final outcome of surgery did not meet the expectations of both the patient and the surgeon that were established before surgery.

Answer 7

121. (B) A. True, this process usually begins at 16 to 20 weeks. In early pregnancy it is important to exclude unruptured ectopic pregnancy and ovarian torsion. B. Radicular symptoms are common during pregnancy; there is a low incidence of herniated disc associated with these complaints. C. Limited plain radiographs that are considered vital may be okay to perform during pregnancy according to some studies. D. It is true that if a new onset migraine occurs during pregnancy, one should investigate a secondary cause (including consideration for an MRI).

Answer 8

122. (C) A. A vasoocclusive crisis most commonly involves the back, legs, knees, arms, chest, and abdomen. The pain generally affects two or more sites. Bone pain tends to be bilateral and symmetric. Recurrent crises in an individual patient usually have the same distribution. B. Acute pain in patients with sickle cell disease is caused by ischemic tissue injury resulting from the occlusion of microvascular beds by sickled erythrocytes during an acute crisis. Acute bone pain from microvascular occlusion is a common reason for emergency department (ED) visits and hospitalizations in patients with sickle cell disease. Obstruction of blood flow results in regional hypoxemia and acidosis, creating a recurrent pattern of further sickling, tissue injury, and pain. The severe pain is believed to be caused by increased intramedullary pressure, especially within the juxta-articular areas of long bones, secondary to an acute inflammatory response to vascular necrosis of the bone marrow by sickled erythrocytes. The pain may also occur because of involvement of the periosteum or periarticular soft tissue of the joints. C. When a vasoocclusive crisis lasts longer than 7 days, it is important to search for other causes of bone pain, such as osteomyelitis, avascular necrosis, and compression deformities. When a recurrent bone crisis lasts for weeks, an exchange transfusion may be required to abort the cycle. D. Patients with homozygous sickle cell and sickle cell–β-thalassemia have a higher frequency of vasoocclusive pain crises than patients with hemoglobin sickle cell and sickle cell–β-thalassemia genotype.

Answer 9

123. (B) A. Depression produces well documented disturbances to sleep architecture including reduced slow-wave sleep and early onset rapid-eye-movement (REM) sleep. Sleep disturbance has been well documented in fibromyalgia. B. This is one of the Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition) (DSM-IV) diagnostic criteria of substance abuse. C. This is not included as one of the DSM IV diagnostic criteria for substance dependence. D. Conversion disorder is an alteration in voluntary motor or sensory function that suggests a neurologic or general medical condition.

Answer 10

124. (A) A. Chronic pain is a major complication of SCI with approximately two-thirds of all SCI patients experiencing some type of chronic pain, and up to one-third complaining of that their pain is severe. The prevalence of pain after SCI often increases with time after injury. B. In addition to central pain, there are multiple types of pain that develop after SCI including musculoskeletal, visceral, and peripheral neuropathic pain. C. Central pain has been reported with injury to all levels of the spinal cord. There is conflicting evidence in the literature as to the level of injury that results in greatest frequency or severity of central pain, whether incomplete spinal cord lesions may result in a higher incidence of central pain or whether there is a link between type of injury and the development of central pain. D. Central neuropathic pain after SCI has been categorized based on the location of the complaint as either at the level of the injury or below the level of the injury. Although it may be difficult to distinguish the two clinically (and both may be present in the same patient), central pain that occurs at the level of injury is because of segmental spinal cord damage, and not because of nerve root damage.

Answer 11

125. (D) A. Physiologic changes occur to the nociceptive neurons in the dorsal horn following SCI including an increase in abnormal spontaneous and evoked discharges from dorsal horn cell. Noxious stimulation causes primary afferent C-fibers to release excitatory amino acid neurotransmitters in the dorsal horn. Prolonged high intensity noxious stimulation activates the NMDA receptors which induces a cascade that may result in central sensitization. B. On a molecular level, abnormal sodium channel expression within the dorsal horn (laminae L1-L4) bilaterally has been implicated as a major contributor to hyperexcitability. These pain relay neurons tend to show increase activity with noxious and nonnoxious stimuli thus serving as a pain amplifier. C. Thalamic neurons appear to undergo changes after SCI in both human and animal models. In the animal model, enhanced neuronal excitability in the VPL has been demonstrated directly and as well as indirectly; enhanced regional blood flow has been found in the rate VPL after SCI suggesting increased neuronal activity. D. Much like the neurons in the dorsal horn, the thalamic neurons after SCI show increased activity with noxious and nonnoxious stimuli. VPL neurons are spontaneously hyperexcitable following SCI without receiving input from the spinal cord neurons suggesting that the thalamus may act as a pain-signal generator in central pain accompanying SCI.

Answer 12

126. (D) A. Excessive alcohol use plays a significant role in up to 70% of adults with chronic pancreatitis. Genetic and structural defects predominate in children. B. Patients may have recurrent episodes of acute pancreatitis, which can progress to chronic abdominal pain. The pain is commonly described as midepigastric postprandial pain that radiates to the back and that can sometimes be relieved by sitting upright or leaning forward. In some patients there is a spontaneous remission of pain by organ failure (pancreatic burnout theory). Patients may also present with steatorrhea, malabsorption, vitamin deficiency (A, D, E, K, and B12), diabetes, or weight loss. Approximately 10% to 20% of patients may have exocrine insufficiency without abdominal pain. C. Autoimmune pancreatitis accounts for 5% to 6% of chronic pancreatitis and is characterized by autoimmune inflammation, lymphocytic infiltration, fibrosis, and pancreatic dysfunction. D. Because of its varied presentation and clinical similarity to acute pancreatitis, many cases of chronic pancreatitis are not diagnosed

Answer 13

127. (D) A. Mainly two types of pain receptors are activated by nociceptive input. These include low-threshold nociceptors that are connected to fast conducting A-δ pain fibers, and high-threshold nociceptors that conduct impulses in slow (unmyelinated) C fibers. Within the dorsal horn of the spinal cord, these pain fibers synapse with spinal neurons via synaptic transmission. B. Many neurotransmitters (ie, glutamate and substance P) are able to modulate the postsynaptic responses with further transmission to supraspinal sites (thalamus, anterior cingulated cortex, insular cortex, and somatosensory cortex) via the ascending pathways. C. The simplest form of plasticity in nervous systems is that repeated noxious stimulation may lead to habituation (decreased response) or sensitization (increased response). Prolonged or strong activity of dorsal horn neurons caused by repeated or sustained noxious stimulation may subsequently lead to increased neuronal responsiveness or central sensitization. Neuroplasticity and subsequent CNS sensitization include altered function of chemical, electrophysiological, and pharmacological systems. These changes cause exaggerated perception of painful stimuli (hyperalgesia), a perception of innocuous stimuli as painful (allodynia), and may be involved in the generation of referred pain and hyperalgesia across multiple spinal segments. While the exact mechanism by which the spinal cord becomes sensitized or in “hyperexcitable” state currently remains somewhat unknown, some contributing factors have been proposed. D. Windup refers to a central spinal mechanism in which repetitive noxious stimulation results in a slow temporal summation that is experienced in humans as increased pain. In 1965, animal experiments showed for the first time that repetitive C fiber stimulation could result in a progressive increase of electrical discharges from the second-order neuron in the spinal cord. This mechanism of pain amplification in the spinal cord is related to temporal summation of second pain or windup. Second pain, which is more dull and strongly related to chronic pain states, is transmitted through unmyelinated C fibers to dorsal horn nociceptive neurons. During the C fibers transmitted stimuli, NMDA receptors of second-order neurons become activated. It is well-known that NMDA activation induces calcium entry into the dorsal horn neurons. Calcium entry into sensory neurons in the dorsal horn induces activation of nitric oxide (NO) synthase, leading to the synthesis of NO. NO can affect the nociceptor terminals and enhance the release of sensory neuropeptides (in particular, substance P) from presynaptic neurons, therefore contributing to the development of hyperalgesia and maintenance of central sensitization. E. Substance P is an important nociceptive neurotransmitter. It lowers the threshold of synaptic excitability, resulting in the unmasking of normally silent interspinal synapses and the sensitization of secondorder spinal neurons. Furthermore, substance P can extend for long distances in the spinal cord and sensitize dorsal horn neurons at a distance from the initial input locus. This results in an expansion of receptive fields and the activation of wide dynamic neurons by nonnociceptive afferent impulses.

Answer 14

(B) A. The presence of several pain inhibitory and facilitatory centers in the brainstem is well recognized. The dorsolateral funiculus appears to be a preferred pathway for descending pain inhibitory systems. B. One function of the descending inhibitory pathway is to ‘focus’ the excitation of the dorsal horn neurons. The effect is to generate a more urgent, localized, and rapid pain signal by suppressing surrounding neuronal activity. C. Facilitatory pathways leading from the brainstem have also been identified. There is now behavioral evidence that forebrain centers are capable of exerting powerful clinically significant influences on various nuclei of the brainstem, including the nuclei identified as the origin of the descending facilitatory pathway. The activity in descending pathways is not constant but can be modulated, for example, by the level of vigilance or attention and by stress. This has been referred to as cognitive emotional sensitization. Forebrain products such as cognitions, emotions, attention, and motivation have influence on the clinical pain experience. D. Certain cognitive styles and personality traits have been associated with the amplification of pain and its extension in the absence of tissue damage. These include somatization, catastrophizing, and hypervigilance. Thus, via descending pathways behavioral and cognitive therapies might also effect synaptic transmission in the spinal cord and thereby have the capacity to prevent or reverse long-term changes of synaptic strength in pain pathways.

Answer 15

129. (D) A. Injured and neighboring noninjured sensory neurons can develop a change in their excitability sufficient to generate pacemaker-like potentials, which evoke ectopic action potential discharges, a sensory inflow independent of any peripheral stimulus. These changes may manifest at the site of the injury, at the neuroma, and in the DRG. Ectopic input is most prominent in A fibers but also occurs to a more limited extent in cells with unmyelinated axons (ie, C fibers). B. Central sensitization represents a state of heightened sensitivity of dorsal horn neurons such that their threshold of activation is reduced, and their responsiveness to synaptic inputs is augmented. There are two forms of central sensitization; an activitydependent form that is rapidly induced within seconds by afferent activity in nociceptors and which produces changes in synaptic efficacy that last for tens of minutes as a result of the phosphorylation and altered trafficking of voltage- and ligandgated ion channel receptors, and a transcription- dependent form that takes some hours to be induced but outlast the initiating stimulus for prolonged periods. C. After peripheral nerve injury C fiber input may arise spontaneously and drive central sensitization. D. Peripheral neuropathic pain, that clinical pain syndrome associated with lesions to the peripheral nervous system, is characterized by positive and negative symptoms. Positive symptoms include spontaneous pain, paresthesia, and dysesthesia, as well as a pain evoked by normally innocuous stimuli (allodynia) and an exaggerated or prolonged pain to noxious stimuli (hyperalgesia/ hyperpathia). The negative symptoms essentially reflect loss of sensation due to axon/neuron loss; the positive symptoms reflect abnormal excitability of the nervous system.

Answer 16

130. (D) A. It is well recognized that the prolonged use of opioids is associated with a requirement for ever-increasing doses in order to maintain pain relief at an acceptable and consistent level. This phenomenon is termed analgesic tolerance. All patients on opiates are at risk to develop tolerance. B. Tolerance may also be related to a state of hyperalgesia that results from exposure to the opioid itself. Patients who receive longterm opioid therapy sometimes develop unexpected, abnormal pain. Similar paradoxical opioid-induced pain has been confirmed in a number of animal studies, even during the period of continuous opioid delivery. This has been termed opiateinduced hyperalgesia (OIH). C. A number of recent studies have demonstrated that such pain may be secondary to neuroplastic changes that occur in the brain and spinal cord. One such change may be the activation of descending pain facilitation mechanisms arising from the rostral ventromedial medulla (RVM). D. Opioids elicit systems-level adaptations resulting in pain due to descending facilitation, upregulation of spinal dynorphin, and enhanced, evoked release of excitatory transmitters from primary afferents. These adaptive changes in response to sustained exposure to opioids indicate the need for the evaluation of the clinical consequences of long-term opioid administration.

Answer 17

131. (A) A. Unlike the somatic motor system which has its motor neurons in the CNS, the motor neurons of the ANS are located in the periphery. B. The peripheral efferent pathways of both the sympathetic and parasympathetic nervous system have two components: a primary presynaptic or preganglionic neuron, and a secondary postsynaptic or postganglionic neuron. C. The cell bodies of the autonomic postganglionic neurons are arranged in aggregates known as ganglia, wherein the synapses between pre- and postganglionic neurons take place. The transmission of signal from the CNS synapses at an autonomic ganglia in the periphery prior to reaching the target organ. D. There are multiple differences between the two systems. Some of the important points are highlighted above.

Answer 18

132. (C) A. The parasympathetic preganglionic fibers travel from the CNS to synapse in ganglia located close to their target organs. In most areas, parasympathetic innervation tends to be more precise than sympathetic innervation. B. Sympathetic fibers are generally distributed throughout the body. Parasympathetic fibers are generally only innervating the visceral organs. C. The preganglionic parasympathetic neurons have their cell bodies in the gray matter of the brainstem and their fibers travel with the oculomotor, facial, glossopharyngeal, and vagus nerves. The preganglionic fibers from the oculomotor, facial, and glossopharyngeal nerves synapse in the ciliary, sphenopalatine, otic, and submaxillary ganglia, all of which are located in the head. From these ganglia, the postganglionic fibers travel to the target organs (eg, the lacrimal and salivary glands). D. The efferent portion of the sympathetic division of the ANS consists of preganglionic neurons, the two paravertebral (lateral) sympathetic chains, prevertebral and terminal ganglia, and postganglionic neurons.

Answer 19

133. (B) A. Most tumors involving the brachial plexus originate from the lung or breast and as a result often invade the lower plexus, particularly the inferior trunk and medial cord. B. Pain was the most common presenting symptom (75%) in a large study of neoplastic brachial plexopathy and usually was located in the shoulder and axilla. Radicular pain was often distributed along the medial aspect of the arm and forearm into the fourth and fifth fingers. Motor and reflex findings commonly (75%) were in the lower plexus distribution (especially C8-T1). Most remaining patients had signs of more widespread (C5-T1) plexus involvement. C. Radiotherapy can produce plexus injury by both direct toxic effects on axons and on the vasa nervorum, with secondary microinfarction of nerve. Neurotoxicity is doserelated for greater than 1000 cGy, pathologic changes can be observed in Schwann cells, endoneurial fibroblasts, and vascular and perineural cells. Administration of 3500 Gy has produced injury to anterior and posterior nerve roots in rodents.

Answer 20

134. (C) A. Overdose of baclofen causes side-effects that range from drowsiness, nausea, headache, muscle weakness, and lightheadedness to somnolence, respiratory depression, seizures, rostral progression of hypotonia, and loss of consciousness progressing to coma. There are a range of symptoms with withdrawal as well; pruritus without rash, diaphoresis, hyperthermia, hypotension, neurological changes, including agitation or confusion, sudden generalized increase in muscle tone, spasticity, and muscle rigidity. With severe withdrawal, rhabdomyolysis and multiple organ failure can occur. B. Baclofen is a γ-aminobutyric acid (GABA) analogue that has inhibitory effects on spinal cord reflexes and brain. The precise mechanism of action of baclofen as a muscle relaxant and antispasticity agent is not fully understood. Baclofen inhibits both monosynaptic and polysynaptic reflexes at the spinal cord level, possibly by decreasing excitatory neurotransmitter release from primary afferent terminals, although actions at supraspinal sites may also contribute to its clinical effects. Baclofen also causes enhancement of vagal tone and inhibition of mesolimbic and nigrostriatal dopamine neurons (directly or via inhibiting substance P). C. ITB withdrawal syndrome has been fatal in some cases. Differential diagnoses include malignant hyperthermia, neuroleptic- malignant syndrome, autonomic dysreflexia, sepsis, and meningitis. D. Refer to explanation A.

Answer 21

135. (C) A. Although a post–lumbar puncture headache is a possibility, other processes including a CNS infection must be excluded. B. In general, prior to treating a post–lumbar puncture headache, conservative management should be trialed for at least 48 hours. C. The most appropriate step. D. MRI of the lumbar spine does not have a role at this stage. E. High-dose narcotic therapy does not have a role at this stage.

Answer 22

136. (A) A. Cervical transforaminal epidural steroid injections are controversial for several reasons. One of the major concerns is the potential involvement of the vertebral artery, which lies in the anterior neuroforamen. B. See explanation A. C. Injecting triamcinolone, which is a particulate steroid, could be problematic, especially if the steroid were to enter the vertebral artery circulation. D. Patients experiencing radicular symptoms in the course of a transforaminal procedure may suggest involvement of a nerve root. E. If the patient has a history of vasovagal responses, appropriate planning should be made to manage these symptoms should they occur during the procedure.

Answer 23

137. (B) A. Mastectomy has been reported to lead to phantom sensation in 22% to 64% of women who have had the operation. B. Phantom sensations are present in the majority of amputees; the sensation is almost always more vivid in the distal extremity. The vast majority of these patients do not have phantom limb pain. C. Stump pain is perceived to be present in the existing body part in the region of amputation; it is often associated with palpable neuromata at the amputation site— however, all amputees have neuromata and not all amputees have stump pain. D. Phantom limb sensations “telescope” with time—the proximal part of the limb disappears first.

Answer 24

138. (A) A. The location of the pain can be helpful for diagnosis. Anterior-superior pain often can be localized to the acromioclavicular joint, whereas lateral deltoid pain is often correlated with rotator cuff pathology. Neck pain and radiating symptoms should be explored because cervical pathology can mimic shoulder pain. Typically, pain that radiates past the elbow to the hand is not related to shoulder pathology. However, it is not uncommon to have pain that radiates into the neck because the trapezius muscle often spasms in patients with underlying chronic shoulder pathology. The presence of both is more likely to be related to cervical pathology. Dull, achy night pain is often associated with rotator cuff tears or severe glenohumeral osteoarthritis B. The patient’s medical history, including joint problems, can help to narrow the differential diagnosis. Autoimmune diseases and inflammatory arthritis can affect the shoulder, resulting in erosions and wear in the glenohumeral joint, whereas diabetes and thyroid disorders can be associated with adhesive capsulitis. C. Acromioclavicular joint pathology is usually well localized. A history of an injury to the joint (shoulder separation), heavy weight lifting, tenderness to palpation at the acromioclavicular joint, pain with crossbody adduction testing, extreme internal rotation, and forward flexion are consistent with the diagnosis. Radiographs may be difficult to interpret because most patients have acromioclavicular osteoarthritis by the age of 40 to 50 years. A distal clavicle lysis or an elevated distal clavicle supports the diagnosis, whereas the absence of tenderness to palpation at the acromioclavicular joint is inconsistent with the diagnosis. D. Rotator cuff disorders that affect the function of the rotator cuff include a partial or complete tear, tendinitis or tendinosis, and calcific tendinitis. Initially, it is more important to differentiate this group of disorders from the other groups than it is to identify the specific diagnosis. Typically, the patients are older than 40 years and complain of pain in the lateral aspect of the arm with radiation no farther than the elbow. Weakness, a painful arc of motion, night pain, and a positive impingement sign are components of the history and physical examination that are consistent with this diagnosis. Findings that are inconsistent with this diagnosis include being younger than 30 years, having no weakness, and presenting no impingement signs. Positive radiographs can be helpful to diagnose calcific tendinitis, acromial spur, humeral head cysts, or superior migration of the humeral head, but are typically normal.

Answer 25

139. (C) 1. L2 nerve: weakness of hip flexion (iliopsoas) and sensory loss on anterior groin and thigh. No deep tendon reflex. 2. L4 nerve: weakness of leg extension (quadriceps), ankle dorsiflexion (tibialis anterior); sensory loss medial calf/foot; loss of patellar reflex. 3. L5 nerve: weakness of dorsiflexion of big toe (EHL) sensory loss lateral aspect of calf and dorsum of foot. No deep tendon reflex. 4. S1 nerve: weakness of toe walking (gastrocnemius); sensory loss on dorsum of foot, loss of Achilles reflex. This is correct because the reflex does not have to be decreased/lost to suspect this nerve root’s involvement. The sensory abnormality is enough.

Answer 26

140. (E) Addiction is a disease of the CNS. All substances of abuse activate essentially the same neuroanatomic structures. All of the structures listed above are properly linked.