Autonomic neuropathy is a symptom complex associated with the dysfunction of the autonomic nervous system that is responsible for the control of everyday body functions including blood pressure, heart rate, sweating, bowel and bladder function.
The most common presentation is orthostatic hypotension . Symptoms may be mild, but can be disabling. Patients with POTS may develop true syncope. Sometimes, other autonomic symptoms may prevent prior to POTS. These may include anhidrosis, dry mouth or dry eyes. Also, bowel and bladder dysfunction are common in addition to impotence or ejaculatory dysfunction.
A detailed family history is important to help identify an inherited form of disease. Symptoms may be very subtle in family members and may require careful questioning to identify. In addition to careful history, physical examination is important. A drop in BP from sitting to standing more than 30 mm Hg is diagnostic of orthostatic hypotension. Motor examination is also important because a somatic peripheral neuropathy is frequently associated with an autonomic neuropathy.
The first goal of treatment is to identify possible underlying causes and begin their treatment. For example, with diabetic neuropathy it’s important to obtain careful control of glucose. In the setting of autoimmune disorders, use of immunomodulatory drugs is indicated. However, in many cases, there is no specific therapy to treat the disease.
In cases where underlying disease is not identified or not treatable, intervention is focused on addressing symptoms. For example with POTS, therapy is focused on increased fluid intake and taking care to avoid falling. By increasing fluid and salt intake, blood volume is increased. Alcohol is to be avoided as it can lead to dehydration. Then, patients should be instructed to slowly move from lying to sitting, and from sitting to standing positions. This allows time for body to equilibrate. Also, patients need to take care that when standing, they have support available to avoid falling and causing injury. When treatment is unsuccessful, pharmacological intervention may help with POTS.
Most cases are idiopathic and demonstrate a very slow progression. For others, prognosis depends on the underlying disease process causing the neuropathy. In many cases, addressing the underlying problem, such as controlling diabetes, eliminating alcohol, or treating other diseases can improve symptoms. For those presenting with an acute idiopathic disease, such as pandysautonomia or Guillain-Barré syndrome, prognosis is excellent after resolution of the acute disease.
Autonomic neuropathy may be idiopathic, or may be part of a familial disease. In addition, secondary autonomic neuropathy may be the result of a number of different disorders, including diabetes mellitus, amyloidosis, autoimmune disorders, or viral infections. The most common neuropathy is that associated with diabetes. Infections can trigger an autoimmune reaction that results in the destruction of autonomic nerves. A similar problem occurs with Guillain-Barré syndrome. Other causes of autonomic neuropathies include cancer, drugs, alcohol, and toxins.
Overall, there is not a significant age, sex, or ethnic predilection for autonomic neuropathies. However, one common presentation is with postural orthostatic tachycardia syndrome (POTS), which is primarily seen in women.
The pathophysiology of autonomic neuropathies depends on the etiology of the disease. Although uncommon, there are a number of inherited autonomic neuropathies. Of the acquired autonomic neuropathies, there are both primary or idiopathic presentations and those that are secondary to other disease processes. Below, we outline some of these diseases.
Inherited autonomic neuropathies
Acquired autonomic neuropathies
Primary acquired autonomic neuropathies
Secondary Acquired Autonomic Neuropathies
The most common symptom of autonomic neuropathy is postural hypotension. By increasing blood volume through fluid and salt intake, the symptoms of POTS can be minimized. In addition, patients need to be careful when changing postural position. When going from supine to sitting to standing, they need to move slowly and have something nearby to hold on to. As noted above, there are a number of drugs to help with some of the other symptoms of the disease, particularly with respect to bladder, bowel, or genitourinary systems.
The nervous system is divided into the central (CNS) and peripheral nervous systems (PNS) . The PNS consists of the nerves that connect the CNS to the rest of the body, including not only the muscles, but also various receptors and glands. Within the PNS there are both afferent (sensory division) and efferent nerves (motor division), bringing information to the CNS and returning commands for action. The efferent system is divided into two components. There are somatic nerves that bring information to the skeletal muscles and there are autonomic nerves that transmit commands to the smooth muscle (heart) and glands. The autonomic nervous system (ANS) has two types of nerves, sympathetic and parasympathetic nerves. The parasympathetic system regulates resting body functions. Whereas, the sympathetic system allows the body to respond to need for increased activity, associated with stress or strenuous work. With autonomic neuropathy, symptoms may go unnoticed, or they may be disabling.
Neuropathy refers to a disorder of the nervous system. The autonomic nervous system is the part of the body that controls many basic functions, such as heart rate, blood pressure, sweating, bowel, and bladder function. Thus, autonomic neuropathy may present with symptoms of low blood pressure, fast heart rate, increased or decreased sweating, and problems with bowel/bladder emptying. Autonomic neuropathy can be from a familial disorder or may be secondary to another disease. Most times it is idiopathic, meaning that we will never know the cause. A careful family history and blood tests will help in determining the underlying diagnosis.
The most common form of autonomic neuropathy is postural orthostatic tachycardia syndrome (POTS). With POTS, when you suddenly stand up, you may have a drop in blood pressure (orthostatic hypotension) and your heart may beat too quickly (tachycardia). Sometimes, this may cause dizziness or even fainting (syncope). In most cases, a cause for the POTS is never identified. Usually, the problem is mild and can be controlled by increased fluid and salt intake to increase blood volume and limit alcohol to avoid dehydration. In addition, changing posture slowly allows the body time to adjust and reduces the symptoms. People with this disorder should also take care to have something/someone to hold on to as they go from sitting to standing. After standing, you should wait for a moment before beginning to walk. In more severe cases, medications can be prescribed.
Autonomic neuropathy can also prevent with increased/decreased sweating. If this is troublesome, there are medications that will diminish symptoms. Problems with bladder/bowel emptying can be treated with drug therapy and medicines for erectile dysfunction can be used when needed.
Many times autonomic neuropathy can be a symptom of another disease. The most common cause is diabetes and it is important to bring sugars under careful control to help manage the diabetic neuropathy. Autonomic neuropathy is also associated with some cancers and with autoimmune diseases. It is important to look for these other causes.