Pure Autonomic Failure (PAF) is an uncommon neurodegenerative condition targeting the body’s autonomic nervous system. This system controls involuntary functions like blood pressure, heart rhythm, and digestion. The disorder, characterized by the gradual deterioration of these functions, tends to emerge in adults between their 40s and 60s.
Key Symptoms of Pure Autonomic Failure
The defining characteristic of Pure Autonomic Failure is neurogenic orthostatic hypotension, a significant and sudden drop in blood pressure upon standing. This causes dizziness, lightheadedness, blurred vision, and in severe cases, fainting (syncope). These symptoms are often most pronounced in the morning, after meals, or in warm environments.
Beyond the hallmark blood pressure changes, PAF affects other autonomic functions. Many individuals experience urinary issues, such as a frequent need to urinate, difficulty emptying the bladder, or incontinence. Constipation is also a frequent and sometimes early symptom.
Other symptoms include a reduced ability to sweat (anhidrosis), which impairs temperature regulation. In men, erectile dysfunction is a common manifestation. Some people also report a persistent “coat hanger” pain across the shoulders and neck that worsens when upright and improves when lying down.
Underlying Neurological Changes
Pure Autonomic Failure is a synucleinopathy, a disease class characterized by the abnormal accumulation of a protein called alpha-synuclein. In PAF, this protein misfolds and creates sticky clumps that aggregate within peripheral autonomic nerve cells. These protein aggregates are known as Lewy bodies, and their formation leads to the progressive damage and death of these cells.
This process causes the failure of the body’s automatic functions. A defining feature of PAF is that these pathological changes are largely restricted to the peripheral autonomic nervous system. Unlike related disorders, the brain and spinal cord are not significantly affected, which explains the specific symptom profile of PAF.
The Diagnostic Process
Diagnosing Pure Autonomic Failure begins with a process of exclusion. Physicians first rule out other potential causes of autonomic symptoms, such as diabetes or medication side effects, through a review of medical history and a detailed physical examination.
Specific tests are then used to confirm autonomic nervous system dysfunction. The tilt-table test is a primary tool used to safely induce and measure orthostatic hypotension. During this test, a person is strapped to a table that is slowly tilted upright while blood pressure and heart rate are continuously monitored.
Other tests may be performed to assess different autonomic functions. A Quantitative Sudomotor Axon Reflex Test (QSART) measures the function of nerves that control sweating. Blood tests can also measure levels of norepinephrine, a neurotransmitter in the autonomic system, which are low in individuals with PAF and do not increase appropriately upon standing.
Distinguishing PAF from Similar Disorders
An important part of the diagnosis is distinguishing PAF from other neurodegenerative diseases with similar autonomic symptoms, particularly Multiple System Atrophy (MSA) and Parkinson’s disease. The main difference lies in which parts of the nervous system are affected.
PAF is defined by symptoms that are almost exclusively autonomic. In contrast, MSA and Parkinson’s disease also involve significant motor system impairments, such as tremors, muscle rigidity, slowness of movement, and problems with balance. The absence of these motor symptoms is the primary clinical feature that separates PAF from the other two conditions.
Some individuals initially diagnosed with PAF may eventually develop motor symptoms, leading to a revised diagnosis of MSA or Parkinson’s. Imaging studies and specific autonomic tests can also help differentiate these conditions. For instance, cardiac imaging often shows preserved nerve function in MSA but reduced function in PAF and Parkinson’s.
Management Strategies
There is no cure for Pure Autonomic Failure, so management focuses on alleviating symptoms and improving quality of life. The approach begins with non-pharmacological strategies, which are lifestyle adjustments designed to manage the most disruptive symptoms, especially orthostatic hypotension.
These lifestyle adjustments include:
- Increasing daily fluid and salt intake to expand blood volume.
- Wearing compression garments, such as waist-high stockings or abdominal binders, to prevent blood from pooling in the lower body.
- Sleeping with the head of the bed elevated by four to six inches.
- Performing physical counter-maneuvers, like crossing their legs or squatting, to raise blood pressure when feeling lightheaded.
When lifestyle changes are not sufficient, medications may be introduced. Fludrocortisone can be prescribed to help the body retain more salt and water, increasing blood volume. Another common medication is midodrine, which acts as a vasoconstrictor to tighten blood vessels and prevent blood pressure from dropping.