What causes numbness after an intramuscular injection?

Numbness After Intramuscular Injection of Dolomed and Diazepam

Numbness following intramuscular injection of dolomed (diclofenac) and diazepam most likely results from direct nerve injury during injection, particularly if the dorsogluteal site was used, though transient local anesthetic-like effects from the medications themselves or vascular compromise are also possible.

Primary Mechanism: Direct Nerve Injury

Sciatic nerve injury is the most common nerve complication from intramuscular injections, especially when administered in the dorsogluteal region (upper outer quadrant of the buttock). 1

• The sciatic nerve is the most frequently affected nerve following IM injection, particularly in children, elderly patients, and underweight individuals 1
• Neurological presentation ranges from minor transient pain to severe sensory disturbance and motor loss 1
• The dorsogluteal site carries significantly higher risk compared to the ventrogluteal region (gluteal triangle), which has a more favorable safety profile 1

Contributing Medication Factors

Diazepam-Specific Considerations

The FDA label for intramuscular diazepam lists several neurological adverse reactions that could manifest as numbness 2:

• Peripheral sensory effects: dysarthria, vertigo, and other neurological symptoms are documented side effects 2
• Vascular complications: venous thrombosis and phlebitis at the injection site are among the most commonly reported adverse reactions 2
• Local tissue irritation from diazepam's formulation may contribute to nerve irritation or compression

Diclofenac (Dolomed) Considerations

• While not directly causing numbness, local tissue inflammation or hematoma formation from the injection could compress adjacent nerves
• Chemical irritation of nerve tissue if inadvertently injected near a nerve bundle

Secondary Mechanisms

Vascular Compromise

• Intravascular injection or perivascular hematoma can compress nerves and cause ischemic numbness 1
• Diazepam's documented association with venous thrombosis at injection sites increases this risk 2

Local Anesthetic-Like Effects

• Some formulations may contain preservatives or vehicles that have transient local anesthetic properties
• Lidocaine, when used in other contexts, causes peri-oral numbness and tinnitus as self-limiting side effects of intravascular absorption 3

Risk Factors for Nerve Injury

Specific patient and technique factors increase the likelihood of nerve injury 1:

• Patient factors: Elderly patients, underweight individuals, children (lower subcutaneous fat thickness exposes nerves) 1
• Injection site: Dorsogluteal region has highest risk; ventrogluteal site is significantly safer 1
• Needle length: Longer needles increase risk of reaching deeper structures including nerves 3
• Injection technique: Failure to use proper anatomical landmarks

Clinical Assessment

Determine the severity and distribution of numbness to guide management 1:

• Mild: Transient paresthesias or numbness limited to injection site area
• Moderate: Numbness extending along a dermatome with preserved motor function
• Severe: Numbness with motor weakness, indicating significant nerve injury requiring urgent evaluation

Document the specific distribution: Does it follow the sciatic nerve distribution (posterior thigh, leg, foot) or is it localized to the injection site? 1

Management Approach

Immediate Actions

Early recognition and appropriate management are crucial to reduce neurological deficit and maximize recovery 1:

• Discontinue any further injections at that site
• Document the exact injection location, needle length used, and technique employed
• Perform neurological examination to assess sensory and motor function

Treatment Options

Management includes drug treatment of pain, physiotherapy, use of assistive devices, and potentially surgical exploration 1:

• Pain management: If neuropathic pain develops, consider gabapentinoids or other neuropathic pain medications 4
• Physiotherapy: Initiate early to prevent contractures and maintain function 1
• Monitoring: Serial neurological examinations to track recovery or progression
• Surgical consultation: Consider if severe motor deficit or no improvement within 3-6 months 1

Expected Timeline

• Most minor nerve injuries from injection resolve within 4 months 5
• Transient symptoms (days to weeks) suggest neurapraxia with good prognosis
• Persistent symptoms beyond 3 months warrant electrodiagnostic studies (nerve conduction studies, EMG) 5

Prevention Strategies

Sciatic nerve injection injury is a preventable event 1:

• Avoid intramuscular injections entirely if other administration routes are available 1
• Use ventrogluteal site (gluteal triangle) instead of dorsogluteal region when IM injection is necessary 1
• Use proper anatomical landmarks: Identify the anterior superior iliac spine and greater trochanter for ventrogluteal injections 6
• Use appropriate needle length: 4-5 mm needles for subcutaneous alternatives minimize risk 3, 7
• Aspirate before injection to avoid intravascular administration

Critical Pitfalls to Avoid

• Do not dismiss numbness as "normal": It indicates potential nerve injury requiring evaluation 1
• Do not delay neurological assessment: Early recognition improves outcomes 1
• Do not continue injecting at the same site: This risks further nerve damage 1
• Do not assume spontaneous resolution: While common, some injuries require intervention 1