What autonomic neuropathy is
Autonomic neuropathy damages the nerves controlling involuntary body functions — blood pressure, heart rate, sweating, bladder emptying, gastrointestinal motility and sexual function. It most commonly coexists with peripheral sensory and motor neuropathy, particularly in diabetes, but can occur independently. Cardiovascular autonomic neuropathy (CAN) produces resting tachycardia, orthostatic hypotension (dizziness on standing), exercise intolerance and silent myocardial ischaemia. Sudomotor dysfunction produces anhidrosis (loss of sweating) or compensatory hyperhidrosis, typically in a stocking-glove distribution.
Gastrointestinal autonomic involvement produces gastroparesis (delayed gastric emptying with nausea, bloating, early satiety), constipation or alternating constipation and diarrhoea. Urogenital dysfunction causes urinary retention, incomplete bladder emptying, erectile dysfunction and vaginal dryness. Hypoglycaemia unawareness in diabetic patients with autonomic neuropathy is a dangerous complication — the normal adrenergic warning symptoms of hypoglycaemia (tremor, palpitations, sweating) are blunted, allowing severe hypoglycaemia to develop without recognition.
- Orthostatic hypotension — dizziness on standing, falls risk
- Resting tachycardia and exercise intolerance
- Gastroparesis — nausea, bloating, early satiety
- Bladder dysfunction — retention, incomplete emptying
- Sudomotor — anhidrosis or compensatory hyperhidrosis
Related: Neuropathy Treatment → · Dr. Jitendra Knowledge Hub → · ICHD-3 Topic →
Causes and evaluation
The most common cause of autonomic neuropathy is diabetes mellitus, where chronic hyperglycaemia damages small autonomic nerve fibres. Other causes include autoimmune conditions (Sjogren's syndrome, autoimmune autonomic ganglionopathy, Guillain-Barre syndrome), neurodegenerative diseases (pure autonomic failure, Parkinson's disease, Lewy body dementia), medications (antihypertensives, antidepressants, opioids), vitamin deficiencies (B12, E), chronic kidney disease and alcohol. Paraneoplastic autonomic neuropathy associated with anti-neuronal antibodies (particularly anti-Hu) is rare but important to identify.
Evaluation includes cardiovascular autonomic reflex testing (heart rate response to deep breathing and Valsalva manoeuvre, blood pressure response to standing), quantitative sudomotor axon reflex testing (QSART) or the thermoregulatory sweat test where available, and assessment of gastrointestinal and bladder function. Blood tests screen for diabetes (HbA1c, fasting glucose), thyroid dysfunction, B12 deficiency, autoimmune markers and paraneoplastic antibodies when indicated. Treatment targets the underlying cause where possible, manages symptoms with compression stockings for orthostatic hypotension, midodrine or fludrocortisone for blood pressure instability, and dietary modifications for gastroparesis. Dr. Jitendra Prasad Yadav (NMC 8029) evaluates autonomic neuropathy at Kathmandu Neurology Clinic & Cognitive Center, Durbar Marg, Opposite of Yak & Yeti Hotel.
- Diabetes — most common cause, chronic hyperglycaemia damage
- Autoimmune — Sjogren's, autoimmune ganglionopathy, paraneoplastic
- Medications — antihypertensives, antidepressants, opioids
- Cardiovascular autonomic testing — heart rate, blood pressure response
- Midodrine or fludrocortisone — for orthostatic hypotension