Peripheral Neuropathies: A Primer
LAS VEGAS — Understanding the anatomy of the body's nervous systems not only assists clinicians with diagnosing a patient with peripheral neuropathy, it also allows patients to understand how treatments and approaches can assist them in alleviating pain.
Speaking at PAINWeek 2015, Natalie H. Strand, MD, a physician at Freedom Pain Hospital—an Arizona-based institution dedicated to managing individuals with chronic pain—described the pathophysiology of peripheral neuropathies and the clinical presentation of painful peripheral neuropathies; reviewed the anatomy of the nervous system and available diagnostic testing for peripheral neuropathy; and reviewed treatment for painful peripheral neuropathy.
Peripheral neuropathy is a condition that encompasses a group of disorders that may involve a single nerve root (mononeuropathy), multiple individual nerves (mononeuropathy multiplex), or small fibers that do not conform to dermatomes (peripheral polyneuropathies).
The nervous system is made up of neurons, which contain cell bodies that contain a nucleus, mitochondria, and organelles; dendrites that pick up signal; and axons that send signals onward to other neurons or effector cells in the body. There are 3 basic classes of neurons: afferent neurons, efferent neurons, and interneurons. Neurons are vital to maintain the functional nervous system and essential to body function; these nerve cells rarely reproduce.
Neuroglia (also known as glial cells) act as "helper" cells of the nervous systems. Neurons are surrounded by from 6 to 60 neuroglia that protect, feed, and insulate the neuron.
There are 2 nervous systems to consider when managing a patient with peripheral neuropathy: the central nervous system and the peripheral nervous system. The nervous system has 3 main functions: sensory, integration and motor.
The peripheral nervous system comprises 2 additional nervous systems: the somatic nervous system, which includes all voluntary efferent neurons, and the autonomic nervous system (ANS), which is a division of the peripheral nervous system that includes all of the involuntary efferent neurons.
Dr. Strand noted that there are more than 100 types of peripheral neuropathy. Several of the mostly commonly encountered types include motor neuropathy, sensory neuropathy, sensorimotor neuropathy, autonomic neuropathy, as well as combinations.
There is a range of clinical features of peripheral neuropathy for clinicians to consider. These include sensory neuropathy, numbness, loss of sensation or feeling in body parts, loss of balance, emotional disturbances, and sleep disruptions, among others.
When assessing a patient for symptoms of motor neuropathies, clinicians should pay attention to any signs of muscle weakness; painful cramps; fasciculations in the muscle (something that can observed in the clinic); muscle atrophy; and changes in skin (waxy or thickened), hair (shorter or longer), or nails.
When conducting an assessment for autonomic neuropathy, symptoms to be alert to include the inability to sweat properly, loss of bladder control, dizziness or lightheadedness, difficulty eating, and life-threatening symptoms such as a difficulty breathing or an irregular heartbeat.
“The medical diagnosis underlying the neuropathy must first be established and managed, when possible,” Dr. Strand advised.
As with any comprehensive clinical evaluation, Dr. Strand noted that a complete history should be obtained, as well as physical and laboratory examination, electrodiagnostic studies (which are commonly used), quantitative sensory testing, and any additional testing as indicated (imaging, rheumatologic screen, thyroid function tests, chest radiographs, HIV testing, Lyme titers, skeletal survey).
The etiology of peripheral neuropathy is varied and includes alcoholism, autoimmune diseases, diabetes, exposure to poisons, medications, infections, inherited disorders, trauma or pressure on a nerve, tumors, and vitamin deficiencies. Other disease states include kidney disease, liver disease, connective tissue disorders, and amyloidosis.
Diabetic peripheral neuropathy is the most common form of diabetic neuropathy. Patients may describe such symptoms as numbness; a reduced ability to feel pain or changes in temperature; a sharp, jabbing pain that may be worse at night; and a tingling or burning feeling. Causes of diabetic peripheral neuropathy include damage to nerves and blood vessels, inflammation in the nerves, smoking, and alcohol abuse. Poor blood sugar control, kidney disease, smoking, and pressure points are risk factors for diabetic peripheral neuropathy.
Complications of peripheral neuropathy include loss of a limb (the worst case scenario), neurogenic arthropathy (Charcot joint), and social isolation (often undertreated), Dr. Strand said.
Clinicians should consider conducting a filament test, nerve conduction studies, and quantitative sensory testing to confirm a diagnosis.
Treatment options for a patient with the condition should revolve around the following: slowing progression, relieving pain and restoring function.
Dr. Strand's take-home message about diabetic peripheral neuropathy is to stress the need to understand and recognize the early signs of the condition, to communicate to patients that there are many modifiable risk factors, and to maintain glycemic control.
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