The anatomical localisation of paraesthesia is the most important clinical skill in managing this symptom — the distribution of tingling determines whether the cause is peripheral (nerve, root, plexus) or central (spinal cord, brainstem, thalamus, cortex). A GP who cannot localise the symptom neuroanatomically cannot safely manage paraesthesia. Key principles: (1) dermatome distribution = nerve root (radiculopathy) — e.g. C6 (thumb, index finger, lateral forearm), L5 (great toe, dorsum of foot, lateral calf); (2) peripheral nerve distribution = entrapment neuropathy — e.g. median nerve (thumb, index, middle, lateral half of ring finger — carpal tunnel), ulnar nerve (little and medial ring finger + medial hand); (3) stocking-and-glove distribution = length-dependent peripheral neuropathy (diabetes, alcohol, B12 deficiency); (4) one limb completely + face contralateral = brainstem; (5) all four limbs = spinal cord (above C5) or bilateral peripheral neuropathy; (6) one body half (hemisensory) = thalamus or cortex. Guillain-Barré syndrome is the most important acute paraesthesia emergency after stroke/TIA — it is post-infectious in 70% of cases (Campylobacter jejuni most common, CMV, EBV, Zika, COVID-19), presenting 1–3 weeks after the infection with ascending tingling starting in the toes. The critical prognostic factor is respiratory compromise — the diaphragm and intercostal muscles can be affected, causing respiratory failure in up to 30% of patients. FVC (<1.5 L = 50% of predicted) is the measurement that triggers ITU transfer. GPs who see a patient with ascending tingling + muscle weakness after a recent diarrhoeal illness must refer to hospital immediately.

Length-dependent peripheral neuropathy is the most common pattern seen in primary care and reflects a fundamental neurobiological principle — the longest peripheral nerves (those supplying the toes and feet) are most susceptible to metabolic damage because they have the greatest distance over which axonal transport must maintain the distal axon. In diabetes, for example, chronic hyperglycaemia causes AGE (advanced glycation end-products) accumulation, oxidative stress, and polyol pathway dysfunction that impairs this axonal transport, affecting the longest nerves first. This is why diabetic peripheral neuropathy begins in both feet, symmetrically, before progressing to involve the legs and later the hands. Understanding this principle means a GP can immediately recognise that "tingling in one foot only" is unlikely to be diabetic neuropathy and requires localised investigation (nerve entrapment, lumbar radiculopathy). The Flick sign for carpal tunnel syndrome (median nerve distribution tingling that is relieved by vigorously shaking or flicking the wrist) has a sensitivity of 93% and specificity of 96% for CTS — it is more sensitive than Tinel's sign (percussion over the carpal tunnel) and Phalen's test (wrist flexion for 60 seconds). It was described by Pryse-Phillips in 1984 and validated in multiple studies. A patient who describes waking at night with tingling in the thumb and fingers and shaking their hand to relieve it has carpal tunnel syndrome until proven otherwise. The hyperventilation-tetany pattern (perioral tingling + bilateral hand tingling + carpopedal spasm) is important to recognise — it is caused by respiratory alkalosis from hyperventilation reducing ionised calcium, producing the sensory and motor manifestations of hypocalcaemia. It is distinct from true hypocalcaemia (which has the same symptoms but different cause) and is treated by addressing the hyperventilation pattern, not calcium supplementation.

The combination of absent ankle jerks + extensor plantar responses (upgoing Babinski) is one of the most clinically important neurological sign combinations — it indicates simultaneous lower motor neurone (absent reflex = LMN at the peripheral nerve or anterior horn) and upper motor neurone (Babinski = UMN corticospinal tract) dysfunction. This combination occurs in three conditions: subacute combined degeneration of the spinal cord (B12 deficiency — posterior and lateral column degeneration), Friedreich's ataxia, and combined peripheral neuropathy with spinal cord compression. In primary care, the absent ankle jerks + upgoing plantars combination in a patient with tingling mandates immediate B12 measurement and urgent neurology referral. Thenar muscle wasting in carpal tunnel syndrome indicates advanced, long-standing disease with significant denervation — this finding should accelerate the referral to neurology/hand surgery for nerve conduction studies and surgical decompression consideration. Early carpal tunnel (tingling only, no wasting) can be managed conservatively with wrist splints. Wasting = nerve damage is occurring. The MRC muscle power scale (0 = no movement, 1 = flicker, 2 = movement with gravity eliminated, 3 = movement against gravity only, 4 = movement against resistance but reduced, 5 = normal) is the universal language for documenting neurological weakness. GPs should document power grades at every neurological examination — "power 4/5 in right ankle dorsiflexion" communicates much more than "some weakness in the right foot" and is the documentation standard expected in medicolegal review of neurological cases.

B12 deficiency is the single most important reversible cause of peripheral neuropathy and spinal cord disease in primary care — the serum B12 level must be measured in every patient with unexplained paraesthesia, regardless of age. The reference range threshold varies between laboratories (typically 180–200 pmol/L), but many patients with neurological manifestations have serum B12 in the "low-normal" range (180–300 pmol/L) while having true functional B12 deficiency. If clinical suspicion is high despite normal serum B12, methylmalonic acid (MMA) and homocysteine are more sensitive markers of functional B12 deficiency (elevated MMA = B12 functional deficiency at cellular level). The interaction between folic acid and B12 in neuropathy management is a prescribing safety issue — folic acid supplementation in a patient with combined B12 and folate deficiency can cause haematological recovery (normalising the macrocytic anaemia) while the B12 deficiency neuropathy continues to progress and becomes irreversible. Always check B12 before prescribing folic acid. Always treat B12 deficiency with IM hydroxocobalamin before or concurrently with folic acid. The paraproteinaemia investigation (SPEP) is important in unexplained peripheral neuropathy — approximately 10% of all peripheral neuropathy cases are caused by a paraprotein (IgM, IgG, or IgA monoclonal protein) from MGUS (monoclonal gammopathy of undetermined significance), multiple myeloma, or Waldenström's macroglobulinaemia. IgM paraproteinaemia is particularly strongly associated with peripheral neuropathy (anti-MAG antibodies in IgM MGUS cause a distinctive predominantly sensory, demyelinating neuropathy). SPEP should be part of the second-line peripheral neuropathy screen in any patient where the first-line investigations are normal.

The surgical referral threshold for carpal tunnel syndrome is based on the presence of thenar wasting — once the abductor pollicis brevis (the thenar muscle innervated exclusively by the median nerve) shows wasting, axonal degeneration of the median nerve is occurring and decompression surgery is indicated regardless of symptom duration. In contrast, mild CTS (tingling only, no wasting, normal sensation) can be managed conservatively: nocturnal wrist splint (neutral position splint, worn at night — treats the nocturnal component which is caused by wrist flexion during sleep), corticosteroid injection (methylprednisolone 40 mg or triamcinolone 10–20 mg into the carpal tunnel — provides 3–6 months of relief in 80% of patients, superior to splinting alone), ergonomic modifications. The NICE guideline on CTS (NG246, 2023) recommends corticosteroid injection as the first-line treatment for mild-moderate CTS before surgery. Mononeuritis multiplex (the simultaneous or successive involvement of multiple separate named peripheral nerves — e.g. right ulnar + left femoral + right sural) is a neurological pattern that is almost always caused by vasculitis (polyarteritis nodosa, Wegener's granulomatosis, rheumatoid vasculitis, SLE, cryoglobulinaemia, diabetic amyotrophy) or sarcoidosis, and occasionally by diabetic amyotrophy. It is a neurological emergency pattern — the nerve damage can be rapid and severe. Any patient with tingling in multiple separate non-contiguous nerve territories simultaneously needs urgent ESR, CRP, ANCA, ANA, rheumatoid factor, cryoglobulins, and urgent neurology referral.

NICE NG173 (Neuropathic Pain in Adults, 2013 updated 2023) recommends amitriptyline, duloxetine, gabapentin, and pregabalin as the four first-line options for peripheral neuropathic pain, with the choice guided by individual patient factors. Amitriptyline has the longest evidence base and is the cheapest (off-patent TCA), but carries anticholinergic risks in older patients (urinary retention, confusion, falls from orthostatic hypotension). Duloxetine is preferred in diabetic neuropathy (licensed indication) and when comorbid depression is present. Pregabalin and gabapentin are equally effective but are now Schedule 3 controlled drugs in England (since 2019) due to misuse concerns — they must be prescribed on CD prescription forms and must NOT be prescribed to patients with a history of opioid, benzodiazepine, or pregabalin/gabapentin misuse. The B12 dosing distinction is critical — the loading regimen for B12 deficiency with neurological features is more intensive than the standard regimen: 6 injections on alternate days (1000 mcg hydroxocobalamin IM each) over 2 weeks, rather than 3 injections over 2 weeks used for haematological deficiency alone. This more intensive loading is recommended by the BNF specifically because neurological recovery requires a higher tissue B12 saturation, and the window for preventing permanent cord damage is time-sensitive. Maintenance thereafter is every 2 months for pernicious anaemia with neurological features (vs 3-monthly for haematological features alone). Thiamine before carbohydrates in alcohol-related presentations is the Wernicke's encephalopathy prevention rule — administering IV glucose to a thiamine-depleted patient precipitates acute Wernicke's encephalopathy by rapidly depleting the last reserves of thiamine needed for glucose metabolism in the brain (specifically the mammillary bodies, thalamus, and oculomotor nuclei). Any patient who is intoxicated, malnourished, or acutely unwell from alcohol excess should receive Pabrinex IV (high-dose parenteral thiamine) before any IV glucose or oral carbohydrate.

The isoniazid-pyridoxine co-prescription rule is a prescribing safety principle that is commonly neglected in primary care — isoniazid (INH) competitively inhibits pyridoxine (vitamin B6) metabolism and causes a peripheral neuropathy in approximately 17% of patients not receiving pyridoxine supplementation, through depletion of pyridoxal-5-phosphate, which is essential for peripheral nerve axonal integrity. NICE TB guidelines (NG33) explicitly recommend co-prescribing pyridoxine 10–25 mg/day with isoniazid for all patients receiving INH-containing regimens. Patients who develop peripheral neuropathy on isoniazid while not receiving pyridoxine have experienced a preventable iatrogenic injury. The McKenzie method for lumbar radiculopathy (extension exercises — "press-ups" from a prone position) is evidence-based physiotherapy for posterolateral disc prolapse causing radiculopathy — it works by using lumbar extension to centralise the disc herniation (pushing the nucleus pulposus anteriorly away from the nerve root). It is most effective when performed early (<6 weeks), repeated frequently (>10 repetitions × 5 times daily), and combined with directional preference assessment by a trained McKenzie physiotherapist. GPs referring for physiotherapy for back pain + radiculopathy should specify "McKenzie-trained physiotherapist for lumbar radiculopathy" rather than generic physiotherapy to ensure the appropriate technique is applied. The 6-week conservative management rule for cervical and lumbar radiculopathy reflects the natural history data — approximately 70–80% of radiculopathy episodes from disc herniation resolve within 6–12 weeks with conservative management. Surgery is indicated for progressive neurological deficit (muscle wasting, power <4/5), sphincter involvement, or failure to improve after 6 weeks of adequate conservative management.

The diabetic foot care pathway is one of the most evidence-based and most impactful preventive interventions in all of primary care — the lifetime risk of a foot ulcer in a diabetic patient is approximately 15%, and 85% of lower limb amputations in diabetic patients are preceded by a foot ulcer. Annual monofilament testing (10-g Semmes-Weinstein monofilament at 10 sites on each foot) identifies patients who have lost protective sensation (cannot feel the filament at ≥4 sites = risk foot), who are at highest risk of ulceration and require: specialist podiatry, prescription footwear assessment, patient education about foot inspection, and an emergency protocol if a foot wound is identified (urgent same-day diabetic foot clinic if any break in skin, redness, swelling, or skin temperature increase). The Otago Exercise Programme for falls prevention in older adults with sensory neuropathy is one of the most rigorously evidence-based community interventions available — it is a home-based balance and strength training programme developed in New Zealand and validated in multiple RCTs. It consists of 17 exercises (leg strengthening + balance exercises) performed 3 times/week, delivered by a physiotherapist initially then independently. NNT of approximately 6 for preventing one fall, and NNT approximately 11 for preventing one injurious fall. NHS falls prevention services (typically within community physiotherapy) deliver the Otago programme — GPs should refer proactively when loss of proprioception or vibration sense is identified on examination.

The DVLA notification requirement for peripheral neuropathy affecting driving is a medicolegal obligation that GPs must advise patients about and document — the DVLA medical standards for driving specify that any condition significantly affecting vehicle control requires notification. For lower limb neuropathy: if the patient cannot safely control the foot pedals (accelerator, brake, clutch) due to sensory loss or motor weakness, they must notify DVLA. Failure to notify DVLA and continued driving is illegal and voids the patient's insurance. The GP must advise the patient to notify DVLA, and should document this conversation in the medical record. If the patient refuses to stop driving when medically unsafe to do so, GPs have a legal obligation to contact the DVLA directly (DVLA Confidential Medical Advice, Swansea). The MRI unexpected finding protocol is important — GPs who request MRI spine for radiculopathy may receive reports containing unexpected findings (incidental meningioma, Chiari malformation, spinal cord lesion, unexpected vertebral metastasis, aortic aneurysm, adrenal lesion). Any unexpected significant finding requires: prompt review of the report, urgent specialist referral appropriate to the finding, and timely communication with the patient. A system for reviewing all imaging reports within 2 weeks of ordering is a clinical governance requirement — many serious diagnoses are made on incidental imaging findings, and the responsibility for acting on these lies with the requesting clinician.