Chapter 53 Central Pain States

Question 1

Central pain

Answer 1

a term used to describe the pain associated
with a wide range of disorders of the central nervous system
(CNS).

Question 2

The International Association for the Study of Pain (IASP) defines central pain as

Answer 2

pain initiated or caused by a primary lesion or dysfunction of the CNS.

Question 3

disorders of central pain include

Answer 3

poststroke, spinal
cord injury (SCI), traumatic brain injury, and multiple sclerosis
(MS).

Question 4

The leading cause of central pain originating in the brain is

Answer 4

stroke

Question 5

Dejerine-Roussy

syndrome

Answer 5

extrathalamic lesions. These pain-generating lesions extend from the first synapse of the
dorsal horn, or trigeminal nuclei, to the cerebral cortex.

Question 6

etiology

Answer 6

The predominant etiology is vascular in origin, accounting for 90% of brain central pain (supratentorial 78% and infratentorial 12%). Extrathalamic sites are involved in 50% to 75% of cases

Question 7

Chronic poststroke

pain more commonly occurs in the presence of

Answer 7

right-sided

thalamic lesions

Question 8

Central pain of spinal origin is predominantly the result of

Answer 8

trauma

Question 9

Many central pain patients maintain their ability to

Answer 9

touch, vibration, and joint movements. This supports the belief that the central pain involves the
spinothalamic tract and its thalamocortical projections.

Question 10

The highest prevalence of central pain is reported in cases of lesions in the

Answer 10

spinal cord, medulla, and ventroposterior part

of the thalamus.

Question 11

spinal cord injury (SCI) pain is broadly divided into

Answer 11

nociceptive and neuropathic with subclassification into

second and third tiers based on the anatomic structures involved, site of pain, and etiology.

Question 12

Nociceptive pain may be

Answer 12

musculoskeletal or visceral in nature. The former may be secondary to overuse of certain parts of the body to compensate for regions of paresis or result from secondary changes in bone or joints.

Question 13

Neuropathic pain usually seen in areas of

Answer 13

sensory abnormalities

Question 14

Neuropathic pain has been

subdivided on the basis of

Answer 14

region, into at-level (radicular or central), above-level, and below-level pain to indicate the
presumed site of the lesion responsible for pain generation.

Question 15

Taxonomy of Spinal Cord Injury Pain

Nociceptive Musculoskeletal

Answer 15

Bone, joint, muscle trauma or
inflammation
Mechanical instability
Muscle spasm
Secondary overuse syndromes

Question 16

Taxonomy of Spinal Cord Injury Pain

Nociceptive
Visceral

Answer 16

Renal calculus, bowel
dysfunction, sphincter
dysfunction, etc.
Dysreflexic headache

Question 17

Taxonomy of Spinal Cord Injury Pain

Neuropathic: Above level

Answer 17

Compressive
mononeuropathies
Complex regional pain
syndromes

Question 18

Taxonomy of Spinal Cord Injury Pain

Neuropathic: At level

Answer 18

Nerve root compression
(including cauda equina)
Syringomyelia
Spinal cord trauma/ischemia
Dual level cord and root
trauma

Question 19

Taxonomy of Spinal Cord Injury Pain

Neuropathic: Below level

Answer 19

Spinal cord trauma/ischemia

Question 20

neuropathic pain definition outlined by the IASP was

Answer 20

“pain initiated or caused by a primary lesion or

dysfunction in the nervous system

Question 21

Grading System for Neuropathic Pain

Answer 21

Criteria to be evaluated for each patient
1. Pain with a distinct neuroanatomically plausible distribution*
2. A history suggestive of a relevant lesion or disease affecting the
peripheral or central somatosensory system†
3. Demonstration of the distinct neuroanatomically plausible
distribution by at least one confirmatory test‡
4. Demonstration of the relevant lesion or disease by at least one
confirmatory test

Question 22

Central pain states likely result from pathophysiologic

changes caused by

Answer 22

irritation of, or damage to, central pain pathways.

Question 23

Injury to the CNS may result in

Answer 23

anatomic, neurochemical,
inflammatory, and excitotoxic changes that result in a sensitized
and hyperexcitable CNS

Question 24

Several neurotransmitters are involved in the processing of

noxious input along the pain pathway

Answer 24

glutamate, gammaaminobutyric
acid (GABA), norepinephrine, serotonin, histamine,
and acetylcholine

Question 25

The shift in firing | from a rhythmic burst to a single spike is determined by

Answer 25

noradrenergic, serotonergic, and cholinergic input to the | reticular and relay cells of the thalamus

Question 26

excitatory amino acids, such as glutamate, are released in the region of SCI and may lead to

Answer 26

neuronal hyperexcitability.

Question 27

At the spinal cord level, substance P and cholecystokinin (CCK) might play an additional role by

Answer 27

influencing the voltage gated sodium and calcium channels.

Question 28

Potassium channels | play a critical role in

Answer 28

setting the resting membrane potential | and controlling the excitability of neurons

Question 29

Central pain in SCI may result from

Answer 29

a combination of deafferentation-induced plastic changes in supraspinal areas along with abnormal input from a pain generator in the spinal cord

Question 30

In SCI, NMDA receptor activation might trigger

Answer 30

the intracellular cascade leading to the upregulation of neuronal activity/ excitability that results in spontaneous and evoked neuronal hyperactivity/hyperexcitability and causes abnormal pain perception.

Question 31

important mechanisms might be a loss of | endogenous inhibition, including

Answer 31

reduced GABA-ergic, | opioid, and monoaminergic inhibition.

Question 32

Central glutamate | levels

Answer 32

Central glutamate levels are known to increase in response to pain in healthy humans, and patients with fibromyalgia are known to have elevated central glutamate levels that directly correlate with response to painful stimuli

Question 33

Patients with fibromyalgia are also known to have | decreased

Answer 33

dopamine and opioid receptor availability in | the forebrain.

Question 34

Patients with complete SCI are known to have

Answer 34

a postinjury reorganization of the somatosensory cortex that correlates with pain intensity

Question 35

Proposed mechanism of central pain in spinal cord injury. Input from primary afferents can be distorted by two mechanisms. FIGURE 53-3

Answer 35

The spinothalamic tract projection neurons from below the spinal injury may be lesioned and give rise to deafferentation hyperexcitability in higher-order neurons including the thalamus. Second-order neurons in the dorsal horn at the rostral end of the spinal lesion may become hyperexcitable as a consequence of excitotoxic changes and disinhibition from damaged GABA-ergic neurons at the level of injury. Abnormal input from these second-order neurons in the rostral end of the spinal cord lesion may propagate via the propriospinal system to the deafferentated thalamic neurons resulting in pain referred to areas below injury level

Question 36

explain why pain occurs more often in patients with partial lesions than in those with complete cord and thalamic injuries.

Answer 36

Lesions in the spinothalamocortical pathways can cause ectopic discharges in various neurons of the spinal cord and brain. Such ectopic neuronal discharges create an illusion of noxious input because of the imbalance between the lateral (inhibitory) and medial (excitatory) STT

Question 37

explain why pain occurs more often in patients with partial lesions than in those with complete cord and thalamic injuries

Answer 37

It appears that severe CNS lesions, with total destruction of ascending sensory systems, do not lead to a central pain syndrome and that mild, moderate, or severe disruption of the anterolateral ascending system, with partial or complete preservation of the dorsal column/medial lemniscus functions, is most frequently associated with central pain syndrome

Question 38

central pain frequently develops weeks or months after development of the lesion and is associated with sensory changes involving the spinothalamic pathways, especially changes in temperature perception

Answer 38

Sensory stimuli act on neural systems that have been modified by previous inputs, the “memory” of which significantly influences pain behavior. The fact that a memory is not activated by the development of a lesion might explain the long delay in the onset of central pain in some patients. The long-term potentiation that is important for this memory might be mediated by NMDA receptors and their influence on calcium conductance.

Question 39

Microglia

Answer 39

the macrophages of the brain and spinal cord that release inflammatory mediators in the event of injury or infection. The activation of microglia and subsequent inflammation is thought to precipitate a cycle of further inflammation and activation of astrocytes.

Question 40

neuropathic component of central pain quality of the pain may be

Answer 40

burning, aching, shooting, pricking, and tingling. The discomfort is generally constant but may wax and wane and often has a deep and/or a superficial component.

Question 41

can provoke or exacerbate spontaneous pain

Answer 41

Nonpainful tactile, thermal, vibratory, | auditory, visual, olfactory, and visceral stimuli

Question 42

Patients with classic Dejerine-Roussy | syndrome have a

Answer 42

a rapidly regressing hemiparesis and a sensory deficit to touch, temperature, and pain. Allodynia, hyperalgesia, and spontaneous severe paroxysmal pain on the hemiparetic side also often occur. These patients can exhibit hemiataxia, hemiastereognosia, and choreoathetoid movements.

Question 43

Organic signs on sensory examination of patients | with thalamic lesions include

Answer 43

the so-called thalamic | midline split for sensory loss and pain.

Question 44

Patients with a history of spontaneous or evoked dysesthesia, hyperesthesia, or paresthesia should undergo

Answer 44

specific but simple bedside testing.

Question 45

Sensory testing in the region where the pain is localized usually shows a

Answer 45

``` paradoxic hypoalgesia (decreased sensitivity to painful stimulus). The region where the patient feels the pain often has decreased sensitivity to thermal stimuli, especially to cold. ```

Question 46

Testing for disturbed | temperature sensation can be accomplished with

Answer 46

a cold metal instrument, ice, or ethyl chloride spray.

Question 47

Touch can be tested with

Answer 47

cotton wool, while pinprick sensation should be assessed using the contralateral side as a control.

Question 48

Chronic poststroke pain patients have an intact

Answer 48

vibration sensation

Question 49

Chronic poststroke pain patients may exhibit mitempfindung (with sympathy)

Answer 49

a phenomenon in which stimulation in one area of the body results in a simultaneous sense of the provoked sensation in another part of the body

Question 50

Chronic poststroke pain patients may exhibit alloesthesia

Answer 50

in which a sensory stimulus on one | side of the body is perceived on the other side

Question 51

Testing for autonomic dysfunction may be important in | patients with SCI.

Answer 51

Lesions above the sixth thoracic level | (splanchnic outflow) are often associated with autonomic dysreflexia.

Question 52

Dysreflexia characterized by

Answer 52

sudden dramatic increases in blood pressure, high or low heart rate, and headache after sensory input such as a full bladder.

Question 53

Dysreflexia becomes especially important in SCI patients having surgery where

Answer 53

below the level of their lesion, including minor operations of the urinary (i.e., cystoscopy) or gastrointestinal (i.e., colonoscopy) systems where the viscera will be stimulated.

Question 54

the goal of therapy is to

Answer 54

improve function and reduce pain without | creating intolerable side effects

Question 55

options available for managing central | pain include

Answer 55

pharmacotherapy, behavioral therapy, physical therapy, neuromodulation, other interventional therapies, and ablative neurosurgery

Question 56

The mainstay of central pain

Answer 56

antidepressants that possibly act by modulating the thalamic burst firing activity via its actions on locus coeruleus noradrenergic neurons and the serotoninergic cells in the dorsal raphe

Question 57

Amitriptyline is often effective in

Answer 57

central poststroke control and SCI pain. Amitriptyline’s benefit derives, in part, from its ability to prevent reuptake of noradrenaline and serotonin.

Question 58

Tricyclic antidepressants (TCAs) dose

Answer 58

should be titrated to 50 to 100 mg/day

Question 59

a good regimen to control the common, steady, burning, dysesthetic component of this syndrome

Answer 59

a combination of a TCA (e.g., amitriptyline), | clonazepam, a benzodiazepine, and a (NSAID)

Question 60

Antiepileptic drugs (AEDs) are useful for

Answer 60

the treatment of neuropathic pain. Currently, the most commonly prescribed AEDs are gabapentin and pregabalin. Both gabapentin and pregabalin appear to be effective in treating central pain

Question 61

Opioids

Answer 61

may benefit some patients; however, it is not first-line therapy. Patients who respond to a trial of opioid infusion may be prescribed long-acting opioids, such as the slow-release formulations or the transdermal preparation.

Question 62

Central Pain Treatment Algorithm Step 1. Identify problems.

Answer 62

Determine existing problems and potential adverse sequelae. Identify biologic and psychological contributors to pain and their influence on the individual’s pain experience. Determine the impact of pain on the patient’s function. Determine how well the patient has adjusted to the disorder causing their central pain (SCI, stroke, MS). Determine the risk of and/or presence of additional consequences of pain and the disorder underlying the central pain (i.e., pressure sores, contractures, adverse drug effects).

Question 63

Central Pain Treatment Algorithm Step 2. Determine reasonable objectives/goals for patient and treating physician

Answer 63

Pain relief/reduction. Treatment of spasm—decrease frequency and/or severity. Increase exercise tolerance and improve function. Achieve independent living. Return to work

Question 64

Central Pain Treatment Algorithm Pharmacologic

Answer 64

First line :AEDs (gabapentin and pregabalin) Second line: TCAs, SNRIs Combinations with AED Third line: Opioids, SSRI Fourth line: Ketamine infusion, Lidocaine infusion

Question 65

Central Pain Treatment Algorithm Interventional

Answer 65

``` Specific to condition Limited evidence Mainly for refractory cases Neuromodulation Spinal cord stimulation (SCS)> DBS, MCS deep brain or motor cortex stimulation Intrathecal therapy Baclofen, Morphine, Clonidine, Ziconotide Acupuncture Ablative therapies (DREZ, cordotomy) ```

Question 66

Central Pain Treatment Algorithm Physical and Occupational Therapy

Answer 66

``` Structured therapy and home exercises Postural re-education Spasticity treatment Bowel/bladder management Braces and devices to assist in home and work function Home/work remodeling Speech therapy ```

Question 67

Central Pain Treatment Algorithm Psychosocial

Answer 67

``` Psychiatric therapy Pharmacologic Counseling CBT Pain coping skills Relaxation Family support and education ```

Question 68

Transcutaneous | electrical nerve stimulation (TENS) provides

Answer 68

long-term benefits to patients with central poststroke pain and those with incomplete SCI

Question 69

poor candidates for SCS

Answer 69

Patients with anesthesia dolorosa (pain in an anesthetic area) and patients with incomplete lesions are poor candidates. Patients who experience more than 50% pain relief during trial stimulation are potential candidates for an implant. In patients with treatment failure, deep brain stimulation (DBS) of the tactile relay nucleus of the thalamus or the lemniscal radiations offers hope.

Question 70

For brain-origin central pain

Answer 70

The neuralgic component is the component sometimes responsive to ablative neurosurgery. SCS is of no benefit for brain-origin central pain, although patients might report relief during a trial. Paresthesia producing DBS and motor cortex stimulation are appropriate for the steady component of the pain.

Question 71

The most commonly administered medications in Intrathecal pumps are

Answer 71

opioids (morphine, hydromorphone, and fentanyl), clonidine, and bupivacaine

Question 72

Baclofen

Answer 72

a GABA agonist, has antinociceptive effects, and its intrathecal administration reduces allodynic responses of neurogenic central pain

Question 73

Intrathecal baclofen can be helpful in treating pain and spasticity multiple types of central pain, including

Answer 73

post-stroke, SCI | and MS pain

Question 74

Ablative surgery includes

Answer 74

cordotomy, cordectomy, and dorsal root entry zone (DREZ) lesioning.

Question 75

The goal of cordotomy and cordectomy

Answer 75

interruption of STTs

Question 76

Cordectomy, the simplest destructive procedure, can benefit patients

Answer 76

with complete lesions. | It is not acceptable to most patients because it obviates their hope for eventual restoration of spinal cord function.

Question 77

Percutaneous/open cordotomy

Answer 77

achieves the same results as cordectomy and is offered to patients with incomplete lesions, but carries the risk of aggravating bladder dysfunction and inducing ipsilateral limb paresis.

Question 78

dorsal root entry zone (DREZ)

Answer 78

equally effective for the neuralgic and the evoked elements of spinal-origin central pain. most useful for the relief of end-zone pain (pain starting at the level of injury and extending distally). Pain extending diffusely, often sacrally distributed, and remotely distributed pain, described as phantom or diffuse burning pain, do not respond well to DREZ.

Question 79

dorsal root entry zone (DREZ) side effects

Answer 79

``` Although the procedure preserves the hope for future spinal cord function and avoids risk of limb paresis, it can interfere with residual bladder function and requires a laminectomy and considerable skill. ```