Back Muscle Spasm

Involuntary, sustained, painful contraction of the paraspinal and other back muscles. It is a symptom and sign, not a diagnosis, and may be the main complaint in acute low back or neck pain.

• Causes:
  • Musculoskeletal: acute lumbar or cervical strain, disc herniation, facet or sacroiliac joint irritation, fracture, vertebral infection, spondyloarthritis.
  • Metabolic and electrolyte: hypocalcaemia, hypomagnesaemia, hypokalaemia, hyponatraemia, dehydration, hypothyroidism, vitamin D deficiency, and after intense exercise or heat exposure.
  • Drugs: statins, diuretics, beta agonists, corticosteroids, lithium, antipsychotics (acute dystonia), metoclopramide, and fluoroquinolones.
  • Neurological: tetanus (with trismus and generalised rigidity), stiff person syndrome, dystonia, Parkinson disease, multiple sclerosis, cord lesions, and strychnine poisoning.
  • Visceral and referred: renal colic, pyelonephritis, pancreatitis, aortic dissection, and pleural disease.
• Spasm protects an injured segment and settles when the primary cause improves. About 80 to 90% resolve within 2 to 6 weeks.
• Risk factors: heavy lifting, poor posture, sedentary lifestyle, obesity, dehydration, fatigue, and previous episodes.

• Sudden, tight, cramping pain in the paraspinal muscles, which are palpably hard and tender, with restricted movement, a guarded posture (loss of lumbar lordosis, lateral shift or scoliosis), and pain on coughing or position change. Spasm may be unilateral or bilateral.
• Relief on lying with knees flexed or heat. Pain with attempted movement, and sometimes with breathing in thoracic spasm.
• Features pointing to other causes:
  • Tetanus: recent wound, trismus, risus sardonicus, opisthotonus, painful generalised spasms triggered by stimuli.
  • Electrolyte disorder: cramps in other muscles, paraesthesia, tetany with Chvostek and Trousseau signs (low calcium or magnesium), weakness and palpitations (low potassium).
  • Cauda equina, myelopathy or infection: neurological deficit, fever, bladder or bowel symptoms.
  • Abdominal or vascular emergency: loin to groin pain, haematuria, hypotension, pulsatile mass.
• Differential diagnosis: lumbar strain, disc herniation, facet syndrome, vertebral fracture, spondyloarthritis, myofascial pain, fibromyalgia, osteomyelitis, tumour, renal colic, aortic dissection, tetanus, and drug induced dystonia.
• Complications: prolonged pain, reduced mobility and deconditioning, sleep disturbance, and recurrence.

• Clinical, with a search for the cause. Ask about trauma, lifting, exercise, heat, fluid intake, drugs, wounds and tetanus immunisation, fever, urinary symptoms and neurological symptoms.
• Examine posture, muscle tone, trigger points, range of movement, neurological function, abdomen and pulses.
• Investigations are guided by findings and are not needed in simple acute spasm: calcium (corrected), magnesium, potassium, sodium, urea and creatinine, glucose, creatine kinase, thyroid function, 25-hydroxyvitamin D, full blood count and CRP. Urinalysis for blood or infection.
• X-ray or MRI for red flags, trauma, persistent pain beyond 6 weeks or neurological signs. ECG when hypokalaemia or hypocalcaemia is suspected.

• Treat the cause: strain, disc, infection, electrolyte disturbance or drug effect.
• General measures:
  • Heat (warm pack or bath) for 15 to 20 minutes several times daily, gentle stretching and movement as soon as tolerated, and avoidance of prolonged bed rest (no more than 1 to 2 days).
  • Maintain fluid and electrolyte balance, with oral fluids 2 to 3 L daily and oral rehydration solution after heavy sweating.
  • Posture correction, ergonomic review, and a graded return to activity.
• Medication (short courses):
  • NSAIDs: ibuprofen 400 mg orally 8 hourly with food, naproxen 500 mg 12 hourly, or diclofenac 50 mg 8 hourly, for 5 to 7 days, with gastroprotection where indicated. Topical diclofenac 1% gel 2 to 4 g 3 to 4 times daily. Paracetamol 1 g 6 hourly.
  • Muscle relaxants for 3 to 7 days at most: tizanidine 2 mg at night increasing to 2 to 4 mg 8 hourly, cyclobenzaprine 5 to 10 mg at night, baclofen 5 mg 8 hourly increasing to 10 mg 8 hourly (reduce in renal impairment), methocarbamol 1.5 g 4 times daily for 2 to 3 days then 1 g 4 times daily, orphenadrine 100 mg 12 hourly, or diazepam 2 to 5 mg at night for up to 3 days. All cause sedation and should be avoided in the elderly, when driving, with alcohol, and in respiratory disease.
  • Opioids only for severe pain, for 3 days at most.
• Electrolyte correction:
  • Hypocalcaemia with tetany: calcium gluconate 10% 10 to 20 mL (2.2 to 4.4 mmol) IV over 10 minutes with ECG monitoring, followed by an infusion if needed. Oral calcium 1 to 2 g elemental daily and vitamin D (cholecalciferol 1000 to 4000 IU daily) for chronic deficiency.
  • Hypomagnesaemia: magnesium sulphate 2 g (8 mmol) IV over 15 to 60 minutes for symptomatic or severe disease, followed by oral magnesium (magnesium glycerophosphate 4 mmol 6 to 8 hourly, as tolerated). Reduce dose in renal impairment.
  • Hypokalaemia: oral potassium chloride 40 to 80 mmol daily in divided doses for mild to moderate disease, IV potassium 10 to 20 mmol per hour with cardiac monitoring for severe disease.
• Trigger point treatment for persistent knots: lidocaine 1% 1 to 2 mL injected into each tender point (maximum 4.5 mg/kg plain), dry needling, massage, and ischaemic compression. Botulinum toxin is considered in refractory myofascial spasm (specialist use, 50 to 100 units across points, limited evidence).
• Physiotherapy: stretching, core and postural strengthening, and manual therapy for persistent or recurrent spasm.
• Tetanus: emergency admission, human tetanus immunoglobulin 500 units IM, wound debridement, metronidazole 500 mg IV 8 hourly for 7 to 10 days, diazepam 5 to 10 mg IV titrated (or higher doses in infusion) for spasm, magnesium sulphate infusion for spasm and autonomic instability, airway protection and intensive care, and tetanus toxoid vaccination.
• Special groups:
  • Pregnancy: heat, positioning, paracetamol and magnesium in documented deficiency. Avoid NSAIDs after 20 weeks and avoid muscle relaxants.
  • Elderly: avoid sedating relaxants, check drug causes (statins, diuretics), and screen for fracture and electrolyte disorders.
  • Renal impairment: avoid NSAIDs, adjust baclofen and magnesium.
  • Athletes: hydration, electrolyte replacement and gradual loading.
• Follow up: review at 1 to 2 weeks. Refer to physiotherapy, spinal or pain services for spasm persisting beyond 6 weeks, recurrent episodes, neurological findings or any red flag.