Page 378 Guide to Pain Management in Low-Resource Settings

366 Andreas Kopf

Lowered threshold may occur with allodynia but is not Neuraxis
required. Also, there is no category for lowered thresh- Nerve structures within the spinal column. Th erefore
old and lowered response—if it ever occurs. epidural, caudal, and spinal anesthesia may be called

Hypoesthesia neuraxial anesthesia techniques.
Decreased sensitivity to stimulation, excluding the spe- Neuritis
cial senses.
Infl ammation of a nerve or nerves.
Informed consent
Neurogenic or neuropathic pain
Th e process of making decisions about medical care Pain initiated or caused by a primary lesion, dysfunc-
that are based on open, honest communication between
tion, or transitory perturbation in the peripheral or cen-
the health care provider and the patient and/or the pa- tral nervous system. Neuropathic pain occurs when a
tient’s family members. Th e idea behind informed con-
lesion or dysfunction aff ects the nervous system. Cen-
sent is that the patient may act as a “symmetrical” con- tral pain may be retained as the term when the lesion
versation partner. In practice, this idea is often diffi cult
or dysfunction aff ects the central nervous system. Th e
to fulfi ll, when the specifi c situation of the patient and causative agent may be nerve compression, trauma,
the highly specialized knowledge of the caregiver may
nerve-invading cancer, herpes zoster, HIV, stroke, dia-
have to result in specifi c recommendations to the pa- betes, alcohol, or other toxic substances.
tient without alternatives (e.g., in advanced chronifi ca-
tion of pain). Neuropathy
Any disease or malfunction of the nerves.
Intrathecal
Th e intrathecal space is located between the arachnoid Nociception
and the pia mater of the spinal cord. It contains the ce- Nociception is the sensory component of pain. It en-
rebrospinal fl uid and the spinal nerves. For anesthesia compasses the peripheral and central neuronal events
the intrathecal space may be reached by needle punc- following the transduction of damaging mechanical,
ture, in special situations, such as advanced cancer pain; chemical, or thermal stimulation of sensory neurons
catheters also may be placed there. (nociceptors).
Local anesthetics Nociceptor

Local anesthetics interfere with the generation and A receptor preferentially sensitive to a noxious stimu-
propagation of action potentials within neuronal mem- lus or to a stimulus that would become noxious if pro-
branes by blocking sodium channels. By use of regional longed. Often called a pain receptor.
anesthetic techniques they are injected in close proxim-
Nonsteroidal anti-infl ammatory drugs
ity to the spinal cord (the intrathecal or epidural space),
(NSAIDs)
to peripheral nerves or nerve plexuses, or—on rare oc-
casions—intravenously infused. NSAIDs inhibit cyclooxygenases, the enzymes that cat-
alyze the transformation of arachidonic acid (a ubiqui-
Myofascial pain
tous cell component generated from phospholipids) to
Myofascial pain is characterized by muscle pain and prostaglandins and thromboxanes. Two isoforms, COX-
tenderness. Very often chronic back pain or shoulder- 1 and COX-2, are expressed constitutively in peripheral
arm syndromes originate in myofascial pain and not in tissues and in the central nervous system. In response
nerve entrapment, instability of the spine or skeletal or to injury and infl ammatory mediators (e.g., cytokines,
disk degeneration. Relaxation techniques and specifi c growth factors), both isoforms can be upregulated, re-
physiotherapy are therefore more successful than anal- sulting in increased concentrations of prostaglandins.
gesics or injection therapies in these pain syndromes. As a result, nociceptors become more responsive to

Neuralgia noxious mechanical (e.g., pressure, hollow organ disten-
sion), chemical (e.g., acidosis, bradykinin, neurotroph-
Pain in the distribution of a nerve or nerves. Neural-
ins), or thermal stimuli.
gia is often—incorrectly—used to describe paroxys-
mal pains.