What is a pinched nerve in the back?

Pinched Nerve in the Back: Understanding Radiculopathy

A pinched nerve in the back, medically known as radiculopathy, occurs when a spinal nerve root is compressed or irritated, typically by a herniated disc, bone spur, or narrowed spinal canal, resulting in pain, numbness, weakness, or tingling that radiates along the affected nerve pathway. 1

Pathophysiology and Causes

A pinched nerve in the back develops when neural tissue experiences mechanical compression, leading to:

• Nerve root compression: Most commonly occurs at L4/L5 and L5/S1 levels (90% of symptomatic lumbar disc herniations) 1
• Common causes:
  • Herniated disc: When the inner nucleus pulposus herniates through the outer covering, compressing adjacent nerve roots 1
  • Spinal stenosis: Narrowing of the spinal canal causing bony constriction of nerve roots 1
  • Bone spurs/osteophytes: Often developing at pseudoarthrosis sites or degenerative areas 2
  • Entrapment neuropathies: Can occur from spinal or extraspinal compression 1
  • Piriformis syndrome: Sciatic nerve compression by the piriformis muscle 1

Clinical Presentation

The symptoms of a pinched nerve depend on which nerve is affected and may include:

• Pain pattern: Radiating pain following a specific nerve distribution (sciatica is most common) 1
• Sensory symptoms: Numbness, tingling, or burning sensations in the affected dermatome 1
• Motor symptoms: Weakness in specific muscle groups corresponding to the affected nerve root 1
• Positive straight-leg-raise test: Reproduction of the patient's sciatica between 30-70 degrees of leg elevation (91% sensitivity but only 26% specificity) 1
• Positive crossed straight-leg-raise test: Less sensitive (29%) but more specific (88%) for diagnosing herniated disc 1

Diagnostic Evaluation

Proper diagnosis involves:

1. Clinical assessment:

   • Focused neurological examination evaluating:
     • Knee strength and reflexes (L4 nerve root)
     • Great toe and foot dorsiflexion strength (L5 nerve root)
     • Foot plantarflexion and ankle reflexes (S1 nerve root)
     • Distribution of sensory symptoms 1

2. Imaging studies:

   • Initial imaging: Standing lumbosacral X-rays to assess spine structure and alignment 3
   • Advanced imaging: MRI lumbar spine without contrast after 6 weeks of failed conservative management 3
   • Immediate MRI indications:
     • Progressive neurological deficits
     • Cauda equina syndrome (urinary retention, bilateral motor weakness, saddle anesthesia)
     • Suspected infection
     • History of cancer with new back pain 3

Red Flags Requiring Urgent Evaluation

Certain symptoms require immediate medical attention:

• Cauda equina syndrome: Urinary retention/incontinence, bilateral leg weakness, saddle anesthesia 1
• Cancer risk factors: History of cancer (positive likelihood ratio 14.7), unexplained weight loss, failure to improve after 1 month, age >50 years 1
• Infection signs: Fever, intravenous drug use, recent infection 1
• Progressive neurological deficits: Worsening weakness or sensory changes 3

Management Approach

Treatment should follow a stepwise approach:

1. Conservative Management (First-line)

• Initial 6-week trial of comprehensive conservative management 3:
  • Pain medications and NSAIDs
  • Physical therapy and home exercise program
  • Muscle relaxers and stretching
  • Approximately 80% of patients with lumbar discopathy experience symptom resolution with appropriate conservative treatment 3
  • Most herniated discs show some degree of resorption after 8 weeks 3

2. Interventional Approaches

• Selective nerve root blocks: Can provide diagnostic information and therapeutic relief 2
• Epidural steroid injections: Consider if initial conservative measures fail 3

3. Surgical Intervention

• Indications for surgery:

  • Cauda equina syndrome (emergency)
  • Progressive or severe neurological deficit
  • Incapacitating radicular pain unresponsive to conservative treatment for >12 weeks
  • Documented spinal instability
  • Severe spinal stenosis with neurogenic claudication 3

• Surgical approaches:

  • Posterior decompression for central canal and foraminal stenosis
  • Minimally invasive approaches when appropriate
  • Fusion procedures when instability is present 3

Prognosis

• Decompressive surgery has demonstrated effectiveness for lumbar stenosis with radiculopathy, with response rates exceeding 80-90% for appropriate candidates 3
• Without surgery, approximately 80% of patients with lumbar discopathy experience symptom resolution with appropriate conservative treatment 3

Common Pitfalls

• Delayed diagnosis of serious underlying conditions (cancer, infection, cauda equina syndrome)
• Premature surgical intervention before adequate conservative management
• Misdiagnosis of radiculopathy as muscle strain or other musculoskeletal conditions
• Failure to address psychosocial factors which are stronger predictors of low back pain outcomes than physical examination findings 1
• Overlooking extraforaminal nerve compression which may not be detected on standard lumbar spine imaging 1

Remember that pinched nerves often improve with conservative management, and surgery should be reserved for specific indications when non-surgical approaches have failed or when neurological deficits are progressive.