Hereditary neuropathy is a general term used to identify a group of genetic disorders that affect the peripheral nervous system (peripheral neuropathy): the nerves and ganglia outside the brain and spinal cord.
Definition & Facts
There are multiple types of hereditary neuropathy, including motor, motor sensory, and sensory autonomic. One of the most common is Charcot-Marie-Tooth disease, a motor sensory neuropathy with an estimated 90 variations.
Symptoms & Complaints
The muscle weakness occurs because the lack of normal nerve impulses causes the patient to use the hands and feet less regularly. The legs and feet seem to be affected more than the upper extremities. Tingling, burning sensations, and pain are generally more pronounced in these areas.
Some experience physical deformities, specifically of the foot. Unusually high arches, severely flat feet, and hammer toes are not uncommon. Ankle sprains are also more likely because the ankles are weakened and more susceptible to injury.
Neuropathy patients often experience difficulty walking, difficulty running, and difficulties with balance as well. Those suffering from sensory autonomic neuropathy can also exhibit gastroesophageal reflux disease and coughing.
While chronic ulcers and blisters can also be characteristic of neuropathy, the pain normally associated with these symptoms typically ranges from minimal to nonexistent because of the loss of sensation in the area. Other general symptoms include vision loss and hearing problems, as well as chronic fatigue.
Hereditary neuropathy is caused by genetic mutations. There are over 70 genes whose mutation can lead to the disorder. These mutations may be inherited in a variety of circumstances. Studies have shown that neuropathy can be passed from parent to child in one of three ways: autosomal dominant inheritance, autosomal recessive inheritance, or X-linked inheritance.
Autosomal dominant refers to the ability to inherit a trait from the gene of only one parent. In contrast, autosomal recessive inheritance requires that each parent passes the gene to the child. X-linked inheritance is characterized by the appearance of the specific gene on the X chromosome only.
Research has shown that the genes that lead to some types of neuropathy may be inherited in either dominant or recessive manners, and the mutation of a single inherited gene can sometimes lead to multiple types of neuropathy.
Diagnosis & Tests
Diagnosis of hereditary neuropathies includes a physical examination and blood tests as well as various neurological testing to first determine that a neuropathy exists. The most common neurological tests include nerve conduction velocity and electromyography, or EMG.
The nerve conduction velocity test is conducted by passing stimuli through electrodes placed on specific areas of the body. The physician conducting the exam measures the time it takes each stimulus to travel from one electrode to another. This allows him to calculate the speed with which the electricity travelled through that specific nerve. Speeds outside of the normal ranges can indicate severe nerve damage.
An EMG is typically performed at the same time. In this procedure, a needle electrode is placed in a muscle, allowing the doctor to record the muscle tissue’s electrical activity when stimulated. A nerve biopsy, where a small incision is made and part of the nerve is removed for testing, may also be used to diagnose neuropathy.
In addition to physical testing, doctors will also ask about the patient's medical history and family history to determine if the disorder is genetic. Determining the type of inheritance (autosomal dominant, autosomal recessive, or X-linked) can also help doctors with certain diagnoses. If the results of these interviews indicate that the disorder is genetic, then genetic testing is recommended.
Through genetic testing, doctors can also determine the rick for patients’ family members who may not yet be exhibiting symptoms. This process also provides more information through prenatal testing, which prepares patients for the possibility of raising a child with the disorder, and genetic counseling, which can help with future family planning.
Treatment & Therapy
There is currently no cure for hereditary neuropathy, but certain treatments and therapies can help minimize the symptoms. Among the medications used are pain relievers, including over-the-counter anti-inflammatory drugs for mild problems and prescription painkillers for the more severe.
Certain anti-seizure medications originally developed to treat epilepsy can also assist with pain. These drugs include pregabalin and gabapentin. Some patients have found that tricyclic antidepressants, such as doxepin, nortriptyline, and amitriptyline, also eliminate their pain. Doctors believe these medications do so by blocking the brain’s ability to feel pain.
While there is no hard clinical evidence to prove its success in treating neuropathy, there are studies to indicate some relief can be found through transcutaneous electrical nerve stimulation or TENS. This is a non-invasive procedure wherein electrodes are attached to the specific area and mild electrical current is sent through the nerves. Patients sometimes turn to alternative treatments like acupuncture and herbs to combat their symptoms.
Prevention & Prophylaxis
There are, however, ways to proactively fight the disorder and prevent symptom flare-ups. Avoiding conditions that aggravate the effects of the disorder can make living with the disease easier. Diabetes mellitus, vitamin deficiency, medication toxicity, and prolonged immobilization can all lead to problems for neuropathy patients. Living a healthy lifestyle, including an adequate amount of physical activity and a balanced diet are the best ways to counteract the effects.