Neuropathy is a direct or indirect interruption in the nerve pathway resulting in a disruption or disturbance of the specific nerve function. The loss of function (neuropathy) can occur at any location in the nervous system, and the severity of loss can be either temporary or permanent (Table 26-1).
A. The nervous system is a complex and intricate matrix of nerve cells, responsible for sensory perception, motor coordination, and autonomic function.
B. The two subsystems of the nervous system are the central nervous system (CNS) and peripheral nervous system.
1. The CNS includes the brain and spinal cord. Deficits may include confusion, alteration in gait, and diminished reflexes.
2. The peripheral nervous system includes the autonomic, parasympathetic, and sympathetic systems. Deficits occur outside the CNS and may include myalgias, paresthesias, motor weakness, and paralytic ileus.
C. Types of Neuropathy
1. Mononeuropathy—caused by lesions of the nerve root or peripheral nerve fiber and asymmetric
2. Polyneuropathy—affecting many nerves and usually bilaterally symmetric
II. Etiology:
Cancer patients are particularly vulnerable to neuropathies for a variety of treatment- and disease-related reasons.
A. Pathophysiologic Mechanisms
1. Direct injury
a. Associated with direct destruction or cumulative dose or blood level of neurotoxic substances. In these cases are usually irreversible (eg, cisplatin).
b. May be further divided into metabolic and toxic
c. Certain cases are reversible for unexplained reasons (eg, oxaliplatin) (Grothey, 2003)
e. May involve specific nerve fibers (small sensory, large motor) that predict whether symptoms will be sensory, motor, autonomic, or combinations of these
f. May be related to the solubilizer rather than the medication; for example, paclitaxel is combined with cremophor for solubility reasons, and the cremophor is actually thought to be the neurotoxic agent (ten Tije et al., 2003)
TABLE 26-1 National Cancer Institute Common Toxicity Criteria for Neurotoxicity
Toxicity
Grade 0
Grade 1
Grade 2
Grade 3
Grade 4
Neuropathy, cranial
Absent
—
Present, not interfering with activities of daily living (ADL)
Present, interfering with ADL
Life-threatening, disabling
Neuropathy, motor
Normal
Subjective weakness, but no objective findings
Mild objective weakness, interfering with function, but not interfering with ADL
Objective weakness interfering with ADL
Paralysis
Neuropathy, sensory
Normal
Loss of deep tendon reflexes or paresthesias (including tingling) but not interfering with function
Objective sensory loss or paresthesia (including tingling), interfering with function, but not with ADL
Sensory loss or paresthesia interfering with ADL
Permanent sensory loss that interferes with function
Cancer Therapy Evaluation Program (2003, March 31). Common terminology criteria for adverse events (Version 3.0, DTCD, NCI, NIH, DHHS). Available: http://ctep.cancer.gov.
2. Inflammatory- or immune-mediated
a. Further classified as autoimmune (antibody-induced) or infective
b. Proposed mechanism for neuropathies from infection, autoimmune, post-transplant, and multiple myeloma or monoclonal gammopathy
c. More acute pain is experienced in this type of neuropathy
d. Motor fibers are more affected in this type of neuropathy
BOX 26-1 Chemotherapy and Biologic Response Modifiers Associated With Neuropathies
