Neuropathy Types & Classification
Definition
Peripheral neuropathy refers to damage or dysfunction of peripheral nerves — those outside the brain and spinal cord. Fibres affected may be motor, sensory, autonomic, or mixed, producing a wide spectrum of clinical presentations.
Fibre Types Affected
| Fibre Type | Manifestation |
|---|---|
| Motor | Weakness, wasting, reduced reflexes, foot drop |
| Sensory (large) | Proprioception loss, vibration loss, ataxia, positive Romberg |
| Sensory (small) | Burning pain, temperature loss, allodynia — early in DPN |
| Autonomic | Postural hypotension, gastroparesis, erectile dysfunction, anhidrosis |
| Mixed | Combination of the above |
Classification by Distribution
- Length-dependent (distal symmetric polyneuropathy): Glove-and-stocking pattern. Longest fibres fail first. Typical of diabetic neuropathy.
- Mononeuropathy: Single peripheral nerve. Examples: carpal tunnel (median), ulnar, common peroneal (foot drop).
- Mononeuritis multiplex: Multiple individual nerves, asymmetric, stepwise. Causes: vasculitis, leprosy, diabetes, sarcoidosis.
- Plexopathy: Brachial or lumbosacral plexus. Severe pain + weakness in a limb. Causes: trauma, infiltration, radiation, diabetic amyotrophy.
- Polyradiculopathy: Multiple nerve roots, often proximal.
Classification by Pathology
Axonal Neuropathy
- Axon itself is damaged ("dying back" — distal to proximal)
- NCS: reduced amplitude, relatively preserved conduction velocity
- Causes: diabetes, alcohol, toxic, uraemic, B12 deficiency
- Recovery: slow; Schwann cells intact but axon must regrow (1–3 mm/day)
Demyelinating Neuropathy
- Myelin sheath is damaged; axon may be spared initially
- NCS: slowed conduction velocity, temporal dispersion, conduction block
- Causes: GBS, CIDP, CMT1, POEMS, paraprotein
- Recovery: faster if axon intact — remyelination occurs
Nerve Conduction Studies (NCS) — Key Principles
- Amplitude: reflects number of functioning axons (axonal disease = low amplitude)
- Conduction velocity: reflects myelin integrity (demyelinating = slow <40 m/s)
- Distal latency: time from stimulus to response (prolonged in demyelination)
- F-wave / H-reflex: assess proximal segments
- EMG: complements NCS; fibrillations/positive sharp waves = active denervation; large polyphasic units = chronic reinnervation
Nursing Note
Explain NCS to patient: mild electric shock sensation. No sedation required. Metal implants usually not a contraindication (unlike MRI). Skin must be clean and warm.
DANG THERAPIST — Causes of Peripheral Neuropathy
D
Diabetes mellitus (most common in GCC)
A
Alcohol — axonal, nutritional overlap
N
Nutritional deficiencies (B12, B1, B6, folate)
G
Guillain-Barré Syndrome (acute, demyelinating)
T
Trauma / entrapment (carpal tunnel, peroneal)
H
Hereditary (CMT, familial amyloid — consanguinity in GCC)
E
Environmental toxins — lead, arsenic, chemotherapy, isoniazid
R
Renal failure (uraemic neuropathy)
A
Amyloidosis (AL or familial TTR)
P
Paraneoplastic (anti-Hu — lung/breast/ovary)
I
Inflammatory / Immune (CIDP, vasculitis, sarcoidosis)
S
Sarcoidosis / Sjögren's
T
Treatment — chemotherapy (vincristine, cisplatin, taxanes)
GCC-Specific Epidemiology
Diabetic Neuropathy
Most prevalent cause in GCC. Diabetes affects 17–20% of adults in Gulf states. 40–50% of diabetics develop neuropathy. DPN is the leading cause of non-traumatic lower-limb amputation.
Vitamin B12 Deficiency
Common due to: metformin use (blocks B12 absorption — screen annually in patients on metformin >4 years), dietary insufficiency in vegetarian populations, pernicious anaemia.
Hereditary Neuropathies
Charcot-Marie-Tooth (CMT) prevalence increased in GCC due to consanguineous marriage. Familial amyloid neuropathy (TTR) also seen. Genetic counselling important.
Diabetic Peripheral Neuropathy (DPN)
Clinical Significance
DPN affects up to 50% of patients with diabetes after 10 years. It is the most common cause of neuropathy worldwide and the principal contributor to diabetic foot disease, amputations, and quality-of-life impairment.
Pathophysiology of DPN
1Chronic hyperglycaemia → polyol pathway activation (sorbitol/fructose accumulation → osmotic stress + NADPH depletion)
2Oxidative stress — excess reactive oxygen species damage nerve cell membranes and mitochondria
3Advanced glycation end products (AGEs) — cross-link proteins, damage Schwann cells and endoneural vessels
4Microvascular ischaemia — endoneural microangiopathy reduces oxygen delivery to peripheral nerves
5Protein kinase C activation → vasoconstriction, reduced endoneurial blood flow
6Cumulative result: axonal degeneration (dying-back), reduced nerve conduction velocity, loss of small then large fibres
Types of Diabetic Neuropathy
1. Distal Symmetric Polyneuropathy (DSPN) — Most Common
- Length-dependent: feet first, stocking then glove distribution
- Small fibre early: burning, shooting, electric pain; allodynia; temperature loss
- Large fibre later: vibration loss, proprioception loss, loss of ankle jerks
- Loss of protective sensation → silent injuries → ulceration
2. Acute Painful Neuropathy
- Triggered by rapid glucose lowering ("insulin neuritis")
- Severe burning/aching pain, allodynia, weight loss
- Usually resolves over months with stable glycaemia
3. Mononeuropathies
- CN III palsy: painful ophthalmoplegia + ptosis, pupil-sparing (microvascular, not compressive)
- CN VI palsy: diplopia on lateral gaze
- Usually resolve spontaneously over 3–6 months
- Entrapment: median nerve (carpal tunnel) more common in diabetes
Special DPN Syndromes
Proximal Diabetic Neuropathy (Diabetic Amyotrophy)
- Also called diabetic lumbosacral radiculoplexus neuropathy or Bruns-Garland syndrome
- Severe, asymmetric thigh/hip pain — often nocturnal, burning
- Proximal leg weakness and wasting (quadriceps)
- Weight loss is common
- Slowly recovers over 12–24 months
- Immunopathogenesis (microvasculitis) — may respond to immunotherapy
Autonomic Neuropathy
- Cardiovascular: resting tachycardia, orthostatic hypotension, silent MI
- GI: gastroparesis, diarrhoea (nocturnal), constipation
- Genitourinary: erectile dysfunction, bladder dysfunction
- Sudomotor: anhidrosis distally, gustatory sweating
- Hypoglycaemia unawareness (see Tab 5)
Clinical Assessment Tools
Neuropathy Disability Score (NDS)
Assesses 4 modalities bilaterally (0–2 each, max 10). Score ≥6 = severe neuropathy.
| Test | Tool | Abnormal |
|---|---|---|
| Vibration | 128 Hz tuning fork — big toe | Absent/reduced |
| Pinprick | Neurotip / Wartenberg wheel | Absent/reduced |
| Temperature | Cold/warm object | Unable to distinguish |
| Ankle reflex | Tendon hammer | Absent (score 1) or absent with reinforcement (2) |
NDS Interpretation
3–5: mild | 6–8: moderate | 9–10: severe
10g Monofilament Testing (MNSI)
- Semmes-Weinstein 10g monofilament
- 4 plantar sites per foot: 1st, 3rd, 5th metatarsal heads + pulp of hallux
- Apply perpendicular until filament bends (~10g force), hold 1 sec
- Patient eyes closed: "Do you feel this?"
- Abnormal: unable to feel ≥1 site → increased ulcer risk
- Do not test on callus, ulcer, or scar
MNSI Questionnaire (Patient)
- 15-item patient questionnaire
- Score ≥7 = neuropathy
- Michigan questionnaire + physical examination score ≥2.5 = neuropathy
Annual Foot Screen
All diabetics should have annual foot screening: monofilament + tuning fork + inspection (skin, callus, deformity, pulses). Document in patient notes.
Management of DPN
Glycaemic Control (Primary Prevention & Slowing Progression)
- HbA1c <53 mmol/mol (7%) in T1DM slows neuropathy progression (DCCT trial)
- Benefit less clear in T2DM but still recommended
- Avoid hypoglycaemia — worsens autonomic function
- CGM beneficial in patients with hypoglycaemia unawareness
Foot Care Education
- Daily foot inspection (mirror if needed)
- Never walk barefoot — especially in GCC (hot surfaces)
- Moisturise (not between toes)
- Appropriate footwear + custom insoles if deformity
- Report any wound or colour change immediately
Treatment of DPN Pain
- Optimise glycaemia first
- First-line: Duloxetine (preferred in DPN) or Amitriptyline
- Pregabalin / Gabapentin as alternative
- Combination therapy for inadequate response
- Topical capsaicin 0.075% for localised pain
- Refer to pain specialist if refractory
Monitoring Schedule
- Annual NDS + monofilament in all diabetics
- 6-monthly if established neuropathy
- Check B12 annually in metformin-treated patients
- Orthostatic BP if autonomic symptoms
Non-Diabetic Neuropathies
Guillain-Barré Syndrome (GBS)
Overview & Pathophysiology
- Acute inflammatory demyelinating polyneuropathy (AIDP) — most common subtype in West
- Post-infectious autoimmune attack on peripheral nerve myelin (AIDP) or axon (AMAN/AMSAN)
- Most common trigger: Campylobacter jejuni (most frequent, axonal subtype)
- Other triggers: CMV, EBV, Zika virus, influenza, COVID-19, MERS-CoV (GCC-relevant)
- Anti-ganglioside antibodies (anti-GM1, anti-GQ1b in Miller Fisher) attack nerve components
Clinical Features
- Ascending weakness/paralysis — legs first, then arms, then cranial nerves
- Areflexia (hallmark — early, even before weakness is pronounced)
- Sensory symptoms (tingling, pins and needles) — often before weakness
- Back pain common at onset
- Autonomic dysfunction — BP/HR lability, urinary retention, ileus
- Respiratory compromise — most feared complication
- Miller Fisher variant: ophthalmoplegia + ataxia + areflexia, anti-GQ1b positive
Diagnosis
- CSF: albuminocytological dissociation — raised protein (0.6–10 g/L), normal white cell count (<10 cells/µL). Peak at 2–4 weeks. May be normal in first week.
- NCS: demyelinating pattern — slowed conduction velocity, prolonged distal latency, conduction block, temporal dispersion. AMAN: low amplitude, normal velocity.
- Anti-ganglioside antibodies (AMAN: anti-GM1; Miller Fisher: anti-GQ1b)
Respiratory Monitoring — Critical Nursing Role
20-30-40 Rule — Intubation Threshold
- VC <20 mL/kg — consider intubation
- MIP <-30 cmH₂O (less negative) — concerning
- MEP <40 cmH₂O — concerning
- Monitor 4-hourly. If VC falling rapidly or patient unable to complete sentence — urgent anaesthetic review
- Do NOT wait for SpO₂ to drop — hypoxia is a late sign in neuromuscular failure
Treatment
- IVIG: 0.4 g/kg/day × 5 days (total 2 g/kg) — first choice in most centres
- Plasma exchange (PLEX): equally effective — 5 exchanges over 2 weeks — use if IVIG contraindicated (IgA deficiency)
- Combining IVIG + PLEX offers no benefit over either alone
- Steroids: NOT effective in GBS — do not use alone
- Supportive: DVT prophylaxis (LMWH + TED stockings), physiotherapy, pain management, NG feeding if bulbar dysfunction
Autonomic Monitoring
- Continuous cardiac monitoring — risk of fatal arrhythmia
- Labile BP: hypertension alternating with hypotension — do not over-treat hypertension
- Bradycardia on suctioning or Valsalva — atropine at bedside
- Urinary retention: catheterise
- Ileus: NGT + IV fluids
Prognosis
- Most patients (80%) make a good recovery
- 20% have residual deficit at 1 year
- 5% mortality (respiratory failure, autonomic instability, PE)
- Poor prognosis: older age, rapid progression, AMAN subtype, axonal damage on NCS, preceding Campylobacter infection
CIDP — Chronic Inflammatory Demyelinating Polyneuropathy
- Chronic equivalent of GBS — symptoms >8 weeks
- Slowly progressive or relapsing-remitting proximal + distal weakness
- Areflexia, sensory loss (large fibre predominant)
- CSF: raised protein; NCS: demyelination
- Responds to: steroids (prednisolone 60mg/day then taper), IVIG (maintenance), plasma exchange
- IVIG maintenance: 1–2 g/kg every 4–6 weeks
- Rituximab for refractory cases
- Monoclonal paraprotein (MGUS): can cause similar picture — check SPEP
Vasculitic Neuropathy
- Presents as mononeuritis multiplex — multiple individual nerve palsies, asymmetric, stepwise
- Often painful (burning / deep aching)
- Causes: systemic vasculitis (PAN, ANCA-associated: GPA/MPA/eosinophilic), rheumatoid vasculitis, SLE, cryoglobulinaemia, leprosy
- Nerve biopsy: epineural vessel inflammation + axonal ischaemia
- Treatment: treat underlying vasculitis — high-dose steroids ± cyclophosphamide
- Can convert to symmetrical polyneuropathy if untreated
Hereditary Neuropathies — CMT
- Charcot-Marie-Tooth (CMT): most common hereditary neuropathy (1 in 2500)
- CMT1: demyelinating — PMP22 duplication (17p11) — very slow NCV (<38 m/s)
- CMT2: axonal — various genes — normal/mildly reduced NCV
- CMTX: X-linked — connexin 32 (GJB1 gene)
- Features: pes cavus (high arched foot), hammertoes, distal wasting ("inverted champagne bottle" legs), distal weakness, sensory loss, reduced/absent reflexes
- Onset: often childhood/adolescence
- GCC: higher prevalence due to consanguinity — autosomal recessive forms
- No disease-modifying treatment — management: physiotherapy, AFOs, orthopaedic surgery, genetic counselling
- Avoid neurotoxic drugs: vincristine can precipitate severe deterioration
Vitamin B12 Deficiency Neuropathy
Subacute Combined Degeneration of the Cord (SACD)
- B12 deficiency affects: posterior columns + lateral corticospinal tracts + peripheral nerves
- Peripheral: distal sensory neuropathy, loss of vibration + proprioception
- Cord: UMN signs (brisk reflexes, Babinski) + sensory ataxia
- The combination of brisk reflexes + peripheral neuropathy = think B12 deficiency
- Causes in GCC: metformin (blocks ileal B12 absorption), vegan/vegetarian diet, pernicious anaemia, post-gastrectomy, coeliac disease
Treatment Protocol
- Hydroxocobalamin 1mg IM on alternate days × 6 doses (2 weeks)
- Then 1mg IM every 3 months (lifelong if pernicious anaemia / irreversible cause)
- If dietary cause: oral B12 1–2mg daily is adequate after loading
- Neurological improvement: may take 3–6 months; some deficit may persist
- Treat also: folate deficiency (give B12 first to avoid unmasking folate-responsive anaemia)
Neuropathic Pain Management
Characteristics of Neuropathic Pain
| Category | Symptom | Description |
|---|---|---|
| Positive | Allodynia | Pain from normally non-painful stimulus (light touch, clothing) |
| Hyperalgesia | Exaggerated pain response to painful stimulus | |
| Spontaneous pain | Burning, shooting, electric shock-like, lancinating | |
| Paresthesiae | Tingling, pins and needles, formication | |
| Negative | Numbness | Reduced or absent sensation |
| Weakness | Motor fibre involvement |
Assessment Tools
DN4 Questionnaire (Douleur Neuropathique 4)
- 7 items scored yes/no: burning, painful cold, electric shocks; tingling, pins/needles, numbness, itching; allodynia to light touch; pinprick hyperalgesia
- Score ≥4/10 = neuropathic pain (sensitivity 83%, specificity 90%)
PainDETECT
- Self-report questionnaire
- Score <13: neuropathic component unlikely | 13–18: possible | >18: likely
NRS (Numeric Rating Scale)
- 0–10; reassess after each treatment titration
- Aim for ≥30% pain reduction (clinically meaningful)
- Document impact on sleep, function, mood
NICE NG173 Pharmacological Treatment Ladder
| Line | Drug | Class | Dose Titration | Key Points & Cautions |
|---|---|---|---|---|
| 1st | Duloxetine | SNRI | Start 30mg od × 2 wks → 60mg od. Max 120mg/day | First choice in DPN. Also treats depression/anxiety (co-morbid benefit). Avoid: uncontrolled glaucoma, hepatic impairment, heavy alcohol use, SSRIs (serotonin syndrome). Nausea common at start — take with food. Withdraw gradually. |
| 1st | Amitriptyline | TCA | 10mg nocte → increase by 10–25mg every 2 wks. Max 75mg (neuropathic pain); do not exceed 150mg without specialist input | Anticholinergic SE: dry mouth, constipation, urinary retention, blurred vision, sedation. Check QTc before starting and at dose increases. Falls risk in elderly — use with caution >65 yrs. Overdose risk — assess for suicide risk. Interactions: MAOIs, tramadol, other QTc-prolonging drugs. |
| 1st | Pregabalin | α2δ ligand (GABA analogue) | 75mg BD → 150mg BD → 300mg BD. Max 600mg/day. Titrate over 4–6 wks | SE: dizziness, somnolence, weight gain, peripheral oedema, blurred vision. Dependence risk — Schedule 3 Controlled Drug (UK). Gradual withdrawal essential. Renally dosed (reduce if eGFR <60). Abuse potential in patients with history of substance misuse. |
| 1st | Gabapentin | α2δ ligand | 300mg od → 300mg TDS → up to 1200mg TDS (3600mg/day max) | Similar to pregabalin. Renal dose adjustment required. Less abuse potential historically but now also Schedule 3 CD (UK 2019). Slower titration than pregabalin. Also useful in post-herpetic neuralgia. |
| 2nd | Tramadol | Weak opioid / SNRI | 50mg QDS → up to 400mg/day. Extended-release preferred | Short-term use only. Seizure risk (lower threshold). Serotonin syndrome with SSRIs/SNRIs/TCAs. Avoid in patients on MAOIs. Not for chronic use. Dependence. |
| 3rd | Capsaicin 8% patch | TRPV1 agonist | Single 60-min application (foot); effect lasts 3 months. Repeat as needed | Specialist use only. Initial burning/stinging at application. Pre-treat with topical lidocaine. Do not apply to face. Effective for post-herpetic neuralgia & HIV neuropathy. |
| 3rd | Lidocaine 5% patch | Local anaesthetic | 1–3 patches to affected area × 12 hrs on / 12 hrs off | Localised, minimal systemic absorption. Particularly useful for allodynia. Not for widespread pain. Post-herpetic neuralgia indication. |
| Specialist | Strong opioids / Ketamine / Spinal cord stimulation | Various | Specialist pain clinic referral | Reserve for refractory neuropathic pain. Balance benefit vs dependence, cognitive SE. Ketamine: IV infusion in specialist settings. SCS: for failed back surgery syndrome, CRPS, refractory DPN. |
Non-Pharmacological Management
Physiotherapy
- Desensitisation: graded tactile stimulation to allodynic areas (textures, temperature)
- TENS (Transcutaneous Electrical Nerve Stimulation): may reduce pain via gate-control theory; low-frequency (4Hz) for opioid effect; high-frequency (80–100Hz) for spinal inhibition
- Mirror therapy: used in CRPS and phantom limb pain
- Graded exercise: improves peripheral circulation, reduces central sensitisation
- Orthotics & splinting: reduce mechanical trauma to insensate limbs
Psychological Approaches
- CBT for chronic pain: targets pain catastrophising, hypervigilance, fear-avoidance behaviour
- Acceptance and Commitment Therapy (ACT): increasing evidence in chronic neuropathic pain
- Sleep hygiene: neuropathic pain disrupts sleep; sleep deprivation worsens pain — address both
- Pain education: understanding neuroplasticity reduces fear
Patient Counselling Key Points
Onset of Effect
All first-line neuropathic pain drugs take 2–4 weeks to show meaningful benefit. Some patients need 6–8 weeks at therapeutic dose. Explain this upfront to prevent premature discontinuation.
Realistic Expectations
Aim for 30–50% pain reduction, not complete elimination. Functional improvement (sleep, mobility) is also a key outcome. Most patients need to try 2–3 drugs before finding optimal treatment.
Pregabalin / Gabapentin — Driving
Advise patients not to drive when starting or increasing dose (dizziness, sedation). Once stable on dose, re-assess. Document advice in notes.
Neuropathic Pain Drug Selector
Select patient parameters to receive personalised prescribing guidance based on NICE NG173
Autonomic Neuropathy Nursing
Clinical Significance
Diabetic autonomic neuropathy (DAN) affects up to 50% of patients with long-standing diabetes and significantly increases cardiovascular morbidity and mortality. Cardiovascular autonomic neuropathy (CAN) is associated with a 2–3× increased risk of cardiac mortality.
Cardiovascular Autonomic Neuropathy (CAN)
Features & Diagnosis
- Resting tachycardia: HR >100 bpm at rest — due to loss of vagal (parasympathetic) tone — earliest sign
- Loss of heart rate variability (HRV): the earliest measurable sign — detected on R-R interval analysis; normally HR increases on inspiration
- Fixed heart rate: "cardiac denervation" — HR does not vary with deep breathing, standing, Valsalva
- Orthostatic hypotension (OH): BP falls ≥20 mmHg systolic or ≥10 mmHg diastolic within 3 min of standing — due to loss of sympathetic vasoconstriction
- Exercise intolerance: reduced peak HR response
- Silent myocardial ischaemia: may present only as dyspnoea, fatigue, or nausea — angina may be absent
Orthostatic Hypotension — Nursing Management
- Measure lying-to-standing BP: lie for 5 min, then stand. Record BP at 1 and 3 min
- Non-pharmacological:
- Rise slowly from bed — sit at edge first for 30 seconds
- Head of bed elevated 30° (reduces nocturnal natriuresis)
- Compression stockings (waist-high class 2)
- Abdominal binder — reduces splanchnic pooling
- Adequate salt and fluid intake (2–3 L/day unless contraindicated)
- Avoid large meals, hot environments, alcohol
- Pharmacological:
- Fludrocortisone 0.1mg od — mineralocorticoid, expands plasma volume. Monitor for oedema, hypokalaemia, supine hypertension
- Midodrine 2.5–10mg TDS — α1 agonist, peripheral vasoconstriction. Take before rising; do not take within 4 hrs of bedtime (supine hypertension)
Gastroparesis
- Definition: delayed gastric emptying without mechanical obstruction — due to vagal damage to gastric pacemaker cells (interstitial cells of Cajal)
- Prevalence: 30–50% of diabetes patients have delayed emptying; symptomatic gastroparesis in ~5%
- Symptoms: early satiety, nausea, vomiting (of undigested food hours after eating), bloating, postprandial fullness, unpredictable glucose excursions
- Diagnosis: gastric emptying scintigraphy (gold standard) — >10% retention at 4 hours = gastroparesis. Exclude mechanical obstruction first (endoscopy/barium study)
- Management:
- Small, frequent meals (6 per day); low fat; low insoluble fibre; liquid meals if severe
- Eat sitting upright; remain upright 1–2 hrs after meals
- Metoclopramide 10mg TDS before meals — DA antagonist; risk of tardive dyskinesia (limit <3 months; contraindicated in Parkinson's)
- Domperidone 10mg TDS — peripheral DA antagonist; check QTc (risk of arrhythmia)
- Erythromycin 250mg TDS — motilin agonist; short-term; tachyphylaxis develops
- NG/NJ feeding or TPN if refractory and unable to maintain nutrition
Bladder Dysfunction & Erectile Dysfunction
Neurogenic Bladder
- Loss of afferent sensation → loss of desire to void → incomplete emptying → overflow incontinence
- Assess: post-void residual (PVR) — use bladder ultrasound. PVR >100 mL = significant
- Urinary tract infections are common consequence — clean intermittent self-catheterisation (CISC)
- Patient education: void by the clock every 3–4 hrs (not relying on urge)
- Bethanechol (cholinergic) — rarely used; side effects
- Urodynamics if diagnosis uncertain
Erectile Dysfunction
- Prevalence: 35–75% of male diabetics — due to autonomic neuropathy + vasculopathy + endocrine factors
- Often early sign of diabetic autonomic neuropathy
- Assessment: International Index of Erectile Function (IIEF) questionnaire; rule out hypogonadism (testosterone)
- PDE5 inhibitors: sildenafil (25–100mg prn), tadalafil (5mg daily or 10–20mg prn), vardenafil. Contraindicated with nitrates — risk of severe hypotension. Caution in cardiovascular disease.
- Refer to urology/sexual health if PDE5 inhibitors fail: vacuum erection devices, intracavernous alprostadil, penile prosthesis
Hypoglycaemia Unawareness
- Normally: hypoglycaemia → autonomic warning symptoms (sweating, tremor, palpitations, hunger) before neuroglycopenic symptoms
- CAN damage adrenergic fibres → loss of autonomic warnings
- Impaired glucagon counterregulation (alpha-cell dysfunction in T1DM)
- Result: patient cannot detect hypoglycaemia until neuroglycopenic (confusion, seizure) — dangerous
- Management:
- Continuous glucose monitoring (CGM) / Flash glucose (Libre) — alerts for low glucose
- Relaxed glycaemic targets: HbA1c individualised; avoid tight targets
- Structured hypoglycaemia avoidance training (DAFNE/BGAT programmes)
- Driving restrictions — must not drive if hypoglycaemia unawareness
- Educate carers/family — glucagon kit at home
Sudomotor Dysfunction
- Damage to sympathetic cholinergic sudomotor fibres → anhidrosis (inability to sweat) distally
- Compensatory hyperhidrosis proximally (trunk, face) — "gustatory sweating" with meals
- Anhidrosis leads to:
- Dry, cracked skin (especially heels) → portal of entry for infection
- Increased risk of foot ulceration
- Impaired thermoregulation — heat stroke risk in GCC climate
- Nursing interventions:
- Daily moisturising (urea-based cream); not between toes
- Inspect feet daily for cracks, fissures, early ulcers
- Avoid hot water bottles / direct heat to feet (thermal injury without sensation)
- Advise on cooling strategies in summer (GCC-specific)
- Assessment: Quantitative sudomotor axon reflex test (QSART) or thermoregulatory sweat test — specialist centres
GCC Context & Exam Preparation
GCC-Specific Neuropathy Burden
- Diabetes epidemic: UAE, Saudi Arabia, Kuwait, Bahrain, Oman, Qatar rank among the highest global diabetes prevalence (17–22% adults). Historical poor glycaemic control + late diagnosis → high DPN burden.
- Diabetic foot: DPN is the primary risk factor for diabetic foot ulcers and amputations — major public health issue in GCC.
- Metformin use: widespread first-line in T2DM → B12 deficiency neuropathy under-recognised. Screen B12 annually in patients on metformin >4 years or high-dose (>2g/day).
- Consanguinity: Hereditary neuropathies (CMT, familial amyloid) at higher prevalence. Genetic services increasingly available in GCC tertiary centres.
- GBS & MERS-CoV: Cases of post-MERS-CoV GBS reported from Saudi Arabia and UAE. Clinicians in GCC should consider GBS in patients with recent respiratory illness + ascending weakness.
- Leprosy: Still endemic in parts of South Asia; expatriate worker populations in GCC may present with leprosy-related mononeuritis multiplex.
DHA / DOH / SCFHS Exam Focus Areas
- Drug selection: Duloxetine first choice in DPN; amitriptyline QTc monitoring; pregabalin as Schedule 3 CD; avoid steroids in GBS
- GBS: CSF finding (albuminocytological dissociation); 20-30-40 rule for intubation; IVIG vs PLEX equally effective; most common trigger = Campylobacter
- B12 deficiency: subacute combined degeneration features; IM hydroxocobalamin protocol; metformin connection
- Monofilament: 10g Semmes-Weinstein; 4 sites per foot; annual screening
- Autonomic neuropathy: orthostatic hypotension definition (20/10 mmHg); management steps; gastroparesis drugs (metoclopramide/domperidone); PDE5 inhibitors contraindicated with nitrates
- CMT: no disease-modifying treatment; avoid vincristine; genetic counselling; pes cavus sign
- DN4: ≥4/10 = neuropathic pain confirmed
Quick Reference: Critical Drug Facts
| Drug | Class | Key Contraindication / Caution | Starting Dose | Monitoring |
|---|---|---|---|---|
| Duloxetine | SNRI | Hepatic impairment; uncontrolled glaucoma; MAOIs; heavy alcohol | 30mg od × 2 wks | LFTs, BP, suicidal ideation in young adults |
| Amitriptyline | TCA | Recent MI, QTc prolongation, urinary retention, closed-angle glaucoma | 10mg nocte | ECG (QTc), anticholinergic SE, falls risk |
| Pregabalin | α2δ ligand | Dependence history, severe renal impairment (dose reduce) | 75mg BD | Renal function, suicidal ideation, weight, oedema |
| Gabapentin | α2δ ligand | Renal impairment (dose reduce); respiratory depression with opioids | 300mg od | eGFR, sedation, respiratory rate if with opioids |
| Tramadol | Weak opioid/SNRI | Epilepsy (lowers threshold); concurrent SSRIs/SNRIs (serotonin syndrome); MAOIs | 50mg QDS | Serotonin syndrome signs, seizures, dependence |
| Metoclopramide | DA antagonist | Parkinson's disease; mechanical GI obstruction; <3 months continuous use | 10mg TDS | Tardive dyskinesia (stop if EPS symptoms) |
| Fludrocortisone | Mineralocorticoid | Heart failure, severe hypertension | 0.1mg od | BP (lying + standing), oedema, K+, weight |
| Midodrine | α1 agonist | Supine hypertension, urinary retention, severe heart disease | 2.5mg TDS | BP (lying!), urinary symptoms, piloerection/scalp pruritus |
Practice MCQs — DHA / DOH / SCFHS Style
1. A 58-year-old male with 15-year history of T2DM complains of burning pain and numbness in both feet. Examination reveals absent ankle reflexes and reduced vibration sense to the knee bilaterally. Which investigation is most appropriate to confirm the diagnosis?
Show Answer
B. Nerve conduction studies. NCS is the standard investigation to confirm peripheral neuropathy, characterise it (axonal vs demyelinating) and assess severity. Skin biopsy (D) assesses small fibres not detected on NCS but is a specialist investigation used when NCS is normal but small fibre neuropathy is suspected.
2. A 35-year-old presents with 2 weeks of ascending weakness starting in both legs, now involving both hands. He had diarrhoea 3 weeks ago. Deep tendon reflexes are absent throughout. CSF shows protein 2.1 g/L and 3 white cells. What is the MOST appropriate initial treatment?
Show Answer
B. IVIG 0.4 g/kg/day for 5 days (total 2g/kg). This is GBS — typical post-infectious (Campylobacter) presentation with albuminocytological dissociation on CSF. IVIG and plasma exchange are equally effective first-line treatments. Steroids (A, D) are NOT effective in GBS and may cause harm.
3. When monitoring a patient with GBS on the ward, at what forced vital capacity (FVC) should you initiate urgent anaesthetic review / consider intubation?
Show Answer
C. <20 mL/kg — the "20-30-40 rule": FVC <20 mL/kg, MIP <-30 cmH₂O, MEP <40 cmH₂O. Do not wait for SpO₂ to fall — hypoxaemia is a late sign in neuromuscular respiratory failure. Proactive intubation is safer.
4. A 70-year-old woman on metformin 2g/day for 8 years presents with subacute onset of sensory ataxia, brisk knee jerks, and absent ankle jerks with extensor plantar responses. Which is the MOST likely diagnosis?
Show Answer
B. Vitamin B12 deficiency — SACD. The key clue is the combination of: (1) brisk knee jerks (UMN/lateral column) + (2) absent ankle jerks (peripheral nerve) + (3) extensor plantars + (4) sensory ataxia (posterior column). This pattern = SACD. Metformin causes B12 malabsorption. Pure DPN would have absent reflexes throughout without UMN signs.
5. According to NICE NG173, what is the first-line recommended drug specifically for diabetic peripheral neuropathy pain?
Show Answer
C. Duloxetine is specifically recommended as the first choice for DPN in NICE NG173. All four are used in neuropathic pain, but duloxetine has specific evidence in DPN and also treats co-morbid depression/anxiety. Tramadol (D) is only second-line, short-term.
6. Orthostatic hypotension is defined as a fall in blood pressure of how much within 3 minutes of standing?
Show Answer
B. ≥20 mmHg systolic OR ≥10 mmHg diastolic within 3 minutes of standing (or head-up tilt to ≥60°). This is the international consensus definition (AAN/ESC). Measure BP after lying for 5 minutes, then at 1 and 3 minutes standing.
7. A patient with diabetic neuropathy is started on amitriptyline 10mg nocte. What is the MOST important baseline investigation to perform before starting?
Show Answer
C. ECG (QTc interval). Amitriptyline prolongs the QTc interval and can precipitate torsades de pointes arrhythmia — particularly dangerous in patients with pre-existing cardiac disease, electrolyte abnormalities, or on other QTc-prolonging drugs. Baseline ECG is essential before starting. Avoid if QTc >450ms (male) or >470ms (female).
8. Which of the following is the MOST common preceding infection in Guillain-Barré Syndrome?
Show Answer
B. Campylobacter jejuni is the most common trigger (accounting for ~30% of GBS cases). It is associated with the axonal subtypes (AMAN/AMSAN) via molecular mimicry between Campylobacter lipo-oligosaccharide and gangliosides (GM1, GD1a). This subtype has a worse prognosis. CMV and EBV are associated with AIDP (classic demyelinating) subtype.
9. A diabetic patient reports bloating, early satiety, and nausea after meals, with erratic postprandial glucose readings. Gastric emptying scintigraphy shows 35% retention at 4 hours. Which dietary modification is MOST appropriate?
Show Answer
B. Small, frequent meals (6 per day), low fat, low insoluble fibre. Gastroparesis management prioritises: frequent small meals (less gastric volume at each sitting), low fat (fat slows gastric emptying), low insoluble fibre (reduces bezoar risk), liquid-consistency meals if needed. Remain upright for 1–2 hours after meals.
10. A young woman has progressive distal weakness, high-arched feet (pes cavus), and hammer toes. Her father has similar feet. NCS shows very slow conduction velocity (28 m/s) in the peroneal nerve. What is the diagnosis and appropriate management?
Show Answer
C. Charcot-Marie-Tooth disease (CMT1). Key features: positive family history, pes cavus, distal wasting, very slow NCV (<38 m/s in CMT1 = demyelinating hereditary). There is no disease-modifying treatment. Management is supportive: physiotherapy, ankle-foot orthoses (AFOs), orthopaedic surgery for severe deformity, genetic counselling. Crucially: avoid vincristine (can precipitate acute severe deterioration).