Makindo Medical Notes

Autonomic Neuropathy is dysfunction of the autonomic nervous system (ANS) due to damage of sympathetic, parasympathetic, or enteric fibres. It affects blood pressure, heart rate, GI motility, bladder control, sweating, and sexual function. 👉 Always search for treatable causes — e.g., diabetes, drug effects, or systemic disease.

• Most are: Diabetes mellitus (up to 30% of long-standing diabetics). 🍬
• Other causes: systemic disease, inflammatory neuropathies, toxins, genetic conditions.
• Hallmark sign: orthostatic hypotension (↓SBP ≥20 mmHg or ↓DBP ≥10 mmHg within 3 minutes of standing, with symptoms). ⚠️

🔎 Causes

• Metabolic/Systemic: Diabetes, porphyria, uraemia.
• Neurological: CIDP, Guillain–Barré, amyloidosis, HIV, HSAN (hereditary sensory + autonomic neuropathies).
• Medications: Diuretics, antihypertensives, insulin, levodopa, dopamine agonists.
• Toxins/Substances: Alcohol, opiates, chemotherapy agents.
• Situational: Postprandial hypotension, volume depletion, vasovagal syncope.

💥 Effects

• Cardiovascular:
  • Resting tachycardia, impaired HR variability.
  • Orthostatic hypotension → dizziness, syncope, visual disturbance, presyncope. ⚡
  • Silent myocardial ischaemia due to impaired pain perception.
• Gastrointestinal:
  • Upper GI: Gastroparesis (nausea, early satiety, postprandial vomiting), reflux, oesophageal dysmotility.
  • Lower GI: Alternating diarrhoea/constipation, faecal incontinence. 💩
• Urogenital:
  • Bladder: Hesitancy, frequency, nocturia, retention → recurrent UTIs.
  • Male: Erectile dysfunction, retrograde ejaculation. 🍆
  • Female: Reduced desire, pain, poor lubrication.
• Sudomotor: Anhidrosis or hyperhidrosis, impaired thermoregulation.

🩺 Clinical Assessment

• Exclude hypovolaemia or acute illness first. 🚰
• Consider neurodegenerative causes: Parkinson’s disease, Multiple System Atrophy, Lewy Body Dementia.
• Ask about systemic symptoms: weight loss, fevers, night sweats → malignancy or amyloidosis.

📊 Investigations

• Bloods: U&E, HbA1c, glucose, FBC, CRP, CK; TFTs, cortisol (if Addison’s suspected).
• Imaging: CXR/AXR for GI symptoms.
• Autonomic Function Tests:
  • Deep breathing HR variability. 🌬️
  • Valsalva manoeuvre (blunted HR/BP response).
  • Tilt-table test (orthostatic hypotension diagnosis).
  • Thermoregulatory sweat test / QSART.
• Cardiac evaluation: Echo + 24h Holter for arrhythmias & HR variability.

💊 Management

• Address cause: optimise diabetes control, stop offending drugs, treat systemic disease.
• Non-pharmacological (first-line for orthostatic hypotension):
  • Hydration, increased salt intake, small frequent meals.
  • Compression stockings, gradual position changes.
• Pharmacological:
  • Fludrocortisone → expands plasma volume. 💧
  • Midodrine (α1 agonist) → raises BP by vasoconstriction. ⬆️
  • Pyridostigmine (sometimes used in resistant cases).
• Symptom-specific:
  • Gastroparesis → metoclopramide, domperidone. 🍽️
  • Diabetic diarrhoea → loperamide, clonidine.
  • Erectile dysfunction → PDE-5 inhibitors.
  • Bladder dysfunction → timed voiding, intermittent catheterisation if retention.

📉 Prognosis

Autonomic neuropathy is a marker of advanced systemic disease (esp. diabetes) and associated with ↑ mortality. Prognosis depends on cause, but early recognition & treatment can improve quality of life.

📚 References

• KDIGO Guidance on Neuropathy
• Autonomic Neuropathy – NCBI Bookshelf
• Clinical Autonomic Neuropathy Review – Brain Journal

💡 Exam Pearls

• Think diabetes if you see orthostatic hypotension + gastroparesis + ED. • Always exclude volume depletion before diagnosing autonomic neuropathy. • Midodrine & fludrocortisone are key drugs — but lifestyle advice is first-line.