Could my nocturnal sweating be related to an abnormal sweat response as suggested by my neurologist's test results, specifically the autonomic function test (AFT)?

Understanding Abnormal Sweat Response in Autonomic Function Testing

Your nocturnal sweating may be related to autonomic dysfunction as indicated by your abnormal autonomic function test (AFT) results, specifically the arterial step one test which likely refers to the Quantitative Sudomotor Axon Reflex Test (QSART) or a similar sudomotor assessment.

Autonomic Function Testing and Sudomotor Assessment

Autonomic function tests evaluate how well your autonomic nervous system works, including the part that controls sweating (sudomotor function). Several tests are used to assess sudomotor function:

• Quantitative Sudomotor Axon Reflex Test (QSART): Evaluates postganglionic sudomotor function by measuring sweat production after acetylcholine iontophoresis 1

  • Has 54-90% sensitivity in detecting small fiber neuropathy
  • May correlate with pain severity in neuropathic conditions

• Sympathetic Skin Response (SSR): Measures electrodermal activity as a surrogate for sudomotor function 1

  • Has 87.5% sensitivity and 88.2% specificity for detecting autonomic neuropathy
  • May predict risk of foot ulceration in diabetic neuropathy

• Thermoregulatory Sweat Test (TST): Assesses sweating patterns over the body

  • When combined with QSART, sensitivity improves to 98%

Connection Between Abnormal Sweat Tests and Nocturnal Sweating

Abnormal results on sudomotor function tests can indicate:

1. Small fiber neuropathy: Damage to small nerve fibers that control sweating 1

   • Can cause both reduced sweating in some areas and compensatory excessive sweating in others

2. Autonomic dysregulation: Dysfunction in central or peripheral autonomic control 2

   • May lead to inappropriate activation of sweat glands during sleep

3. Sympathetic overactivity: Excessive stimulation of eccrine sweat glands by the sympathetic nervous system 3

   • Common in various sleep disorders and can manifest as nocturnal hyperhidrosis

Clinical Evaluation Approach

If you have abnormal sweat response on autonomic testing and nocturnal sweating:

1. Further autonomic assessment should include:

   • Deep-breathing test to assess heart rate variability 1
   • Valsalva maneuver to evaluate cardiovascular autonomic function 1
   • 24-hour ambulatory blood pressure monitoring to identify nocturnal "non-dipping" or "reverse-dipping" patterns characteristic of autonomic failure 1

2. Screen for underlying causes of autonomic dysfunction:

   • Diabetes mellitus (most common cause of autonomic neuropathy) 1
   • Neurodegenerative disorders (Parkinson's disease, multiple system atrophy) 4
   • Autoimmune conditions (consider antibody testing) 4
   • Sleep disorders (obstructive sleep apnea, restless legs syndrome) 3
   • Medications that affect autonomic function 4

3. Evaluate for other symptoms of autonomic dysfunction:

   • Orthostatic hypotension (measure blood pressure lying and standing) 4
   • Gastrointestinal issues (gastroparesis, constipation) 4
   • Genitourinary problems 4

Management Recommendations

Based on your abnormal sweat response and nocturnal sweating:

1. For nocturnal sweating:

   • Optimize sleep environment (moisture-wicking bedding, temperature control)
   • Rule out sleep disorders with polysomnography if clinically indicated 3
   • Consider medications that reduce sweating if severe (anticholinergics, alpha-blockers) 4

2. For underlying autonomic dysfunction:

   • Non-pharmacological measures (increased fluid intake, compression stockings) 4
   • Avoid triggers that worsen symptoms (alcohol, caffeine, hot environments) 4
   • Medication adjustments if any current medications contribute to symptoms 4

Important Considerations

• Nocturnal sweating alone does not indicate increased risk of death 5
• Most patients with persistent night sweats in primary care settings do not have serious underlying disorders 5
• Common benign causes include menopause, mood disorders, gastroesophageal reflux disease, hyperthyroidism, and obesity 5
• Thermogenic (heat-related) and psychogenic (stress-related) sweating involve different brain regions and mechanisms 6

Follow up with your neurologist to discuss the specific results of your autonomic function test and develop a personalized management plan based on your complete clinical picture.