Makindo Medical Notes

Peripheral neuropathy

Note 📝: In the UK and US, the most common causes of peripheral neuropathy are diabetes and alcohol abuse 🍺. Worldwide 🌍, leprosy 🧑‍⚕️ remains a significant cause.

🔎 About Peripheral Neuropathy

• Also see “Length-Dependent Polyneuropathy” for further detail.
• Peripheral neuropathy = disease of peripheral nerves, usually secondary to systemic or primary neurological conditions.
• Clinical patterns vary: may be symmetrical or patchy, distal or proximal, and affect motor, sensory, or autonomic function.

⚙️ Aetiology

• Peripheral nerves have two major fibre types:
  • Small fibres 🔥: pain, temperature, autonomic function.
  • Large fibres 🎻: motor strength, vibration, proprioception.

🧩 Different Forms of Peripheral Neuropathy

Type	Description
Wallerian Degeneration	After nerve transection, distal axon + myelin degenerate; regeneration proceeds proximally → distally (often incomplete).
Axonal Degeneration	“Dying back” pattern; toxins, diabetes, alcohol, nutritional deficiencies common culprits.
Demyelination	Loss of myelin with preserved axons; e.g. Guillain–Barré, CIDP.
Neuronal Cell Body Disease	Anterior horn cell involvement (e.g. polio, MND, paraneoplastic).
Dorsal Root Ganglionopathy	Affects sensory ganglia; causes patchy sensory loss (e.g. paraneoplastic, Sjögren’s).

🧭 Patterns of Peripheral Neuropathy

Pattern	Description
Polyneuropathy 🧦	Distal, symmetrical “glove and stocking” loss; diabetes, alcohol, B12 deficiency, Lyme disease.
Mononeuropathy 🔒	Single nerve lesion (e.g. carpal tunnel, ulnar palsy, diabetic entrapments).
Mononeuritis Multiplex 🌿	Asymmetric multi-nerve involvement; think vasculitis.
Autonomic Neuropathy ⚡	Postural hypotension, bowel/bladder issues; causes include diabetes, amyloidosis, toxins.
Abrupt-Onset Neuropathy 🚨	Ischaemic; PAN, RA, HIV-related.
Cranial Nerve Involvement 👁️	E.g. bilateral facial palsy in diabetes, Lyme, sarcoid, GBS.

🩺 Common Causes

Cause	Description
Diabetes Mellitus	Symmetrical distal sensorimotor + autonomic neuropathy (most common UK cause).
Alcohol Abuse 🍺	Painful, distal symmetric sensorimotor neuropathy; worsened by vitamin deficiencies.
B12 Deficiency 🍊	Loss of proprioception, ataxia, brisk reflexes (mixed neuropathy + myelopathy).
Uraemia 💧	Common in CKD or dialysis patients.
Autoimmune (RA, SLE)	Can cause distal sensory-motor neuropathy.
Paraneoplastic 🧬	Often sensory; think lymphoma, lung cancer.
Vasculitis	Mononeuritis multiplex; painful, abrupt onset.
Chemotherapy 💊	Platinum agents, vinca alkaloids; distal symmetrical neuropathy.
Guillain–Barré (GBS)	Acute demyelinating polyneuropathy with autonomic features; albuminocytologic dissociation.
CIDP	Chronic demyelinating sensorimotor neuropathy; relapsing/progressive course.
Hereditary (e.g. CMT)	Distal weakness, pes cavus, family history.
Leprosy 🦠	Worldwide leading cause; thickened nerves, anaesthetic skin patches.

🧾 Clinical Features

• Sensory: Paraesthesia, burning pain, allodynia, proprioceptive loss → ataxia.
• Motor: Distal weakness, areflexia, foot drop, “high-stepping” gait.
• Autonomic: Postural hypotension, bowel/bladder dysfunction, erectile difficulties.
• Hereditary Clues: Pes cavus, hammer toes.
• Nerve Thickening: Rare; in leprosy, CIDP, CMT.

📈 Rate of Onset

• Days: GBS, vasculitis.
• Weeks: CIDP.
• Months–Years: Diabetes, alcohol, hereditary neuropathies.

🧭 Diagnostic Clues

• Speed of onset (acute vs chronic).
• Systemic history (diabetes, alcohol, autoimmune disease).
• Cranial/autonomic involvement → red flag.
• Distribution: small fibre vs large fibre.
• Family history → hereditary cause.

🔬 Investigations

• First-line: FBC, ESR, CRP, U&E, LFTs, glucose/HbA1c, B12, folate, TFTs.
• Autoimmune: ANA, dsDNA, ENA, ANCA.
• Infectious: HIV, hepatitis serology, CXR (TB/sarcoid).
• NCS/EMG: To classify as axonal vs demyelinating, motor vs sensory.
• Selective: CSF (GBS/CIDP), ACE (sarcoid), genetic testing (CMT), nerve biopsy if unclear.

💊 Management

• Always treat the underlying cause (e.g. glycaemic control, alcohol cessation, B12 replacement).
• Neuropathic pain: duloxetine, gabapentin, pregabalin.
• Supportive: physiotherapy, orthotics, podiatry, lifestyle adjustments.
• Immune-mediated: IVIG, steroids, plasma exchange (GBS, CIDP).

Cases — Peripheral Neuropathy

• Case 1 — Diabetic Neuropathy (Metabolic): A 62-year-old man with poorly controlled type 2 diabetes reports numbness and burning pain in both feet, worse at night. Exam: stocking distribution sensory loss, reduced ankle reflexes, preserved power. Diagnosis: Distal symmetric sensory neuropathy due to diabetes. Management: Optimise glycaemic control; neuropathic pain agents (duloxetine, pregabalin); podiatry care to prevent ulcers.
• Case 2 — Alcoholic Neuropathy (Toxic + Nutritional): A 55-year-old man with long-standing alcohol excess presents with tingling and weakness in his legs. Exam: distal wasting, areflexia, sensory loss to vibration. Diagnosis: Peripheral neuropathy due to alcohol toxicity and thiamine deficiency. Management: Abstinence from alcohol, thiamine supplementation, physiotherapy.
• Case 3 — Vitamin B12 Deficiency (Nutritional): A 45-year-old vegan develops progressive numbness in feet and unsteady gait. Exam: reduced vibration sense, positive Romberg, brisk reflexes (subacute combined degeneration). Diagnosis: Peripheral neuropathy due to vitamin B12 deficiency. Management: Parenteral vitamin B12 replacement; treat cause (e.g., pernicious anaemia).
• Case 4 — Charcot–Marie–Tooth Disease (Hereditary): A 19-year-old man has progressive foot deformities and distal weakness. Exam: pes cavus, foot drop, absent ankle reflexes, glove-and-stocking sensory loss. Family history of similar symptoms. Diagnosis: Hereditary motor and sensory neuropathy (Charcot–Marie–Tooth). Management: Supportive: physiotherapy, orthotics, genetic counselling.
• Case 5 — Guillain–Barré Syndrome (Immune-Mediated, Acute): A 33-year-old man develops ascending weakness 2 weeks after a diarrhoeal illness. Exam: areflexia, bilateral foot drop, and distal paraesthesia. Diagnosis: Acute inflammatory demyelinating polyneuropathy (GBS). Management: Admit for monitoring; IV immunoglobulin or plasma exchange; respiratory support if vital capacity drops.

Teaching Commentary 🧠

Peripheral neuropathies can be classified by pattern (sensory, motor, sensorimotor), time course (acute vs chronic), and cause (metabolic, toxic, nutritional, hereditary, immune, infectious). - Diabetes = most common cause worldwide. - Alcohol + nutritional deficiencies common in Western settings. - Vitamin B12 deficiency gives mixed neuropathy + myelopathy. - Charcot–Marie–Tooth = hereditary with pes cavus. - GBS/CIDP = acute or chronic demyelinating immune neuropathies. Approach: history, examination (distribution, symmetry, reflexes), then confirm with nerve conduction studies, bloods, and targeted tests. Management is always cause-specific + supportive.