Peripheral Polyneuropathy
What is neuropathy?
The peripheral sensory nervous system is a network of nerves that sends signals to the brain and spinal cord or central nervous system (CNS) from all other parts of the body. Peripheral sensory nerves send signals to the CNS, including those related to light touch, vibration, pain, temperature, and proprioception (position in space). Other peripheral nerves carry signals from the CNS to the rest of the body such as motor nerves, which lead to muscle contraction.
Large peripheral nerves are made up of a nerve axon and a myelin sheath (protective coating), while small nerve fibers do not have a myelin sheath. When one or both of these parts are damaged, there can be a disruption of this signal pathway, resulting in a peripheral neuropathy. This can occur from damage to a single peripheral nerve (mononeuropathy) or multiple nerves (polyneuropathy); in this blog, we will focus on peripheral polyneuropathy.
There are over 100 types of polyneuropathy. By far, diabetes is the leading cause with about 60-70% of patients experiencing neuropathy symptoms. Other causes include alcohol, poor nutrition (i.e. vitamin deficiencies like B12), certain toxins and heavy metals, genetic factors (i.e. Charcot-Marie-Tooth disease, autoimmune disease, Lyme disease, cancer, chemotherapy, liver, kidney or thyroid disease, HIV/AIDS), and certain medications. Notably, roughly 46% of polyneuropathies are classified as idiopathic,1 which means that despite extensive testing, no specific cause for the neuropathy is identified.
What are the symptoms of neuropathy?
Symptoms of polyneuropathy range from mild to severe, and are 75% of the time “length” dependent, meaning the farthest nerve endings in the feet are affected first. As neuropathy progresses, it can move upward to involve the legs, and can then affect the hands in a classic “stocking and glove” distribution. The symptoms vary depending on what type of peripheral nerve is damaged.
Sensory polyneuropathy symptoms include numbness, tingling, and burning pain; balance can also be affected. Neuropathic pain is often worse at night and can disrupt sleep. Motor polyneuropathy symptoms include muscle weakness, atrophy (wasting), fasciculations (twitching), and cramps.
How is neuropathy diagnosed?
In addition to a thorough history and physical exam, polyneuropathy is diagnosed with an electromyography/nerve conduction study (EMG). This test evaluates the large peripheral sensory and motor nerves and helps reveal whether symptoms are caused by damage to the myelin sheath (demyelinating), axon (axonal), or both.2 It is important to note that this test does not evaluate the small nerve fibers. When a small fiber neuropathy is suspected, an epidural skin biopsy can be performed, where a few small samples of skin are removed and examined under a microscope to evaluate nerve fiber density. When a diagnosis of polyneuropathy is given, it can also be helpful to order blood tests to evaluate for potential treatable causes.
How is neuropathy treated?
Maintaining a healthy weight, eating a well-balanced diet, getting regular exercise, and avoiding alcohol and tobacco are beneficial for all patients with polyneuropathy. Treatment also depends on the cause of the neuropathy, and while often not reversible, addressing the cause can lead to some recovery and prevent the neuropathy from worsening. For example, strict blood glucose control in patients with diabetic neuropathy is imperative. However, because polyneuropathies are commonly idiopathic, treatment often involves symptom management alone.
Medications can be helpful for those with bothersome symptoms. Pregabalin and Duloxetine are the only oral medications approved by the FDA for treating neuropathy related to diabetes. Gabapentin and tricyclic antidepressants like Amitriptyline can also be effective. Physical therapy and assistive devices are also important if there are symptoms of weakness or decreased balance.
When symptoms do not sufficiently respond to these conservative measures, more invasive treatments may be pursued, including spinal cord stimulation, which is FDA-approved for the treatment of symptoms related to painful diabetic neuropathy.3
Neuropathy Treatment in Arizona
Our board-certified PM&R specialists at Desert Spine and Sports Physicians are trained to help diagnose and treat neuropathy, including the performance of EMGs, at all of our Valley locations. We look forward to helping our patients by decreasing pain and improving function.
References:
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4756033/
- https://www.ninds.nih.gov/health-information/disorders/peripheral-neuropathy
- https://www.prnewswire.com/news-releases/fda-approves-abbotts-spinal-cord-stimulation-for-people-living-with-painful-diabetic-peripheral-neuropathy-301731127.html
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