What are the next steps for a patient experiencing right leg numbness after an injection?

Right Leg Numbness After Injection: Immediate Evaluation and Management

This patient requires urgent neurological assessment within hours to rule out epidural hematoma or abscess, which are neurosurgical emergencies that can cause permanent paralysis if not decompressed within 24-48 hours. 1

Immediate Red Flag Assessment

Perform an immediate focused neurological examination to identify life-threatening complications:

• Motor strength testing: Assess hip flexion, knee extension, ankle dorsiflexion, and plantar flexion bilaterally 1
• Sensory examination: Test light touch, pinprick, and proprioception in dermatomal distribution 1
• Sphincter function: Ask specifically about urinary retention, incontinence, or fecal incontinence 1
• Perineal sensation: Check for saddle anesthesia, which indicates cauda equina syndrome 1
• Straight leg raise test: Assess for worsening radiculopathy 1
• Vital signs: Check for fever, which may indicate epidural abscess 1

Critical Time-Sensitive Actions

If ANY of the following are present, this is a neurosurgical emergency:

• Progressive motor weakness in the leg 1
• Urinary retention or new incontinence 1
• Saddle anesthesia 1
• Fever with neurological symptoms 1
• Bilateral leg symptoms 1

For patients with these red flags:

• Obtain emergency MRI of the spine with and without contrast within 2-4 hours to evaluate for epidural hematoma or abscess 1
• Activate immediate neurosurgical consultation 1
• Surgical decompression within 24-48 hours of symptom onset significantly improves neurological outcomes 1

Management Based on Clinical Findings

If Red Flags Present (Emergency Pathway)

1. Do not delay imaging for any reason 1
2. Emergency neurosurgical consultation and admission for urgent surgical decompression if epidural hematoma or abscess is confirmed 1
3. Consider thromboprophylaxis during immobilization, as patients are at increased risk for deep vein thrombosis 1

If No Red Flags But Isolated Numbness (Urgent Pathway)

1. Still obtain MRI within 24 hours to rule out evolving pathology 1
2. Refer to specialist pain management within 2 weeks for severe radicular symptoms if workup is negative but symptoms persist 1
3. Document the exact distribution of numbness and any progression 1

Common Pitfalls to Avoid

Do not assume this is a benign complication:

• New-onset severe back or leg pain following spinal injection can be a symptom of life-threatening conditions such as epidural hematoma or abscess 1
• The absence of back pain does not rule out serious pathology 1

Do not delay evaluation:

• Contact patients the day following their spinal injection to exclude concerning features; if this did not occur and symptoms developed, this represents a systems failure requiring immediate correction 1

Do not confuse this with anaphylaxis:

• The evidence provided about anaphylaxis management 2, 3 is not relevant to isolated leg numbness after injection
• Numbness is not a feature of anaphylaxis, which presents with lip/facial swelling, throat closing sensation, difficulty breathing, rash, vomiting, or hypotension 2

Documentation Requirements

Document the following immediately:

• Time of injection and time of symptom onset 1
• Exact anatomical distribution of numbness 1
• Presence or absence of all red flag symptoms 1
• Neurological examination findings 1
• Patient's ability to ambulate 1