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Toxic & Inflammatory Neuropathy

Like any other living tissues, nerves are subject to various categories of illness, including inflammatory, toxic, traumatic, metabolic, genetic, or neoplastic (tumor-like) disorders. In spite of important similarities, toxic and inflammatory neuropathy differ in their causes and patterns.

  1. Nerve Cell Anatomy & Function

    • Sensory neurons relay the information they receive to the central nervous system (CNS), while motor neurons carry commands from the CNS to muscles and glands. The structure of all neurons includes a cell body, an axon and dendrites. The cell body contains the nucleus and other subunits called organelles. Dendrites are short extensions of cells that receive signals from other neurons, while the much longer axon fiber transmits information. Insulating layers of myelin sheath may wrap the axon.

    Neuropathy Classification

    • Medscape dubs neuropathy "sensory" or "motor," depending on the type of neurons affected. Neuropathy that affects nerves within the brain is said to be cranial, while "peripheral neuropathy" refers to disorders of the nerves located outside the brain and spinal cord. Clinicians may also base their description of a neuropathy on its diagnostic features, or its location within a nerve. For instance, in demyelinating neuropathy (myelinopathy), the myelin sheath is damaged, while in axonal neuropathy (axonopathy), the axon degenerates.

    Causes of Toxic Neuropathy

    • Medscape describes three categories of toxic neuropathy: neuropathy of the cell body, myelinopathy and distal axonopathy. They may all result from the ingestion or abuse of various drugs and chemicals, as well as exposure to workplace or environmental toxins. The numerous potential culprits include lead, arsenic, inorganic mercury, the paint component xylene and cardiac medications perhexiline or amiodarone,

    Causes of Inflammatory Neuropathy

    • According to "Robbins & Cotran Pathologic Basis of Disease," infectious agents and certain immune mechanisms can trigger acute or chronic inflammatory neuropathy. With inflammation, white blood cells and chemicals infiltrate various areas of nerves, causing demyelination and dysfunction. Although most cases have unknown causes, Medscape associates some cases with such conditions as hepatitis B or C, HIV infection and systemic lupus.

    Signs and Symptoms

    • According to Medscape, neuropathy patients experience pain, tingling, or numbness, commonly starting in their hands or feet, and spreading toward the center of the body. Other symptoms may include muscle weakness, an unsteady gait, heart-rate disturbances and loss of reflexes. In toxic neuropathy, the symptoms depend on the amount and duration of exposure to a toxin. In "Robbins & Cotran Pathologic Basis of Disease," Dr. Vinay Kumar and colleagues associate acute inflammatory neuropathy with rapid ascending paralysis, while patients with chronic inflammatory neuropathy experience relapses of milder symptoms and remissions over several years.

    Diagnostic Procedures

    • Electromyography (EMG) and nerve conduction studies (NCV) are key tests for the diagnosis of toxic or inflammatory neuropathy. Laboratory tests, imaging studies, tissue biopsies and thorough patient histories are also important aspects of the diagnostic process.

    Treatment Options

    • For cases of toxic neuropathy, Medscape advises removal from workplace or environmental exposure, and discontinuation of medication. Other options include: diet changes, cool soaks, heat, massage, exercise, lipoic acid, evening primrose, vitamin supplements, opiates and topical capsaicin cream. Antidepressants and anticonvulsants are pharmacological options for both toxic and inflammatory neuropathy. In addition, treatments that modulate the immune response can relieve inflammatory neuropathy, says Medscape.

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