What is the initial workup for a patient presenting with new onset paresthesia?

Initial Workup for New Onset Paresthesia

The initial workup for new onset paresthesia should include targeted laboratory testing (complete blood count, electrolytes, glucose/HbA1c, vitamin B12 levels) and neuroimaging only when indicated by clinical suspicion, rather than as routine measures for all patients. 1

Diagnostic Approach

Step 1: Focused History and Examination

• Determine distribution pattern (focal, multifocal, or diffuse)
• Identify associated symptoms:
  • Weakness, numbness, or pain
  • Neurological symptoms (dizziness, dysphagia, diplopia)
  • Recent viral illness or trauma
  • Underlying medical conditions (diabetes, thyroid disease)
• Document timing and progression:
  • Sudden vs. gradual onset
  • Transient vs. persistent symptoms
  • Exacerbating or alleviating factors

Step 2: Laboratory Testing (Targeted, Not Routine)

Laboratory testing should be guided by clinical suspicion rather than ordered routinely 2, 1:

• First-line tests when clinically indicated:

  • Complete blood count
  • Electrolytes and renal function
  • Random glucose or HbA1c
  • Vitamin B12 levels (especially with peripheral symptoms) 3
  • Coagulation studies (if cerebrovascular event suspected)

• Additional tests based on specific concerns:

  • Lyme disease serology (in endemic areas) 2, 1
  • Thyroid function tests
  • Lipid profile (if vascular etiology suspected)

Step 3: Imaging Studies (Selective Use)

Neuroimaging should not be performed routinely but reserved for specific indications 2, 1:

• Indications for brain imaging (CT or MRI):

  • Focal neurological deficits
  • Sudden onset with concern for TIA/stroke
  • Progressive symptoms
  • Associated headache, altered mental status
  • History of malignancy or immunocompromise

• MRI is preferred over CT for diagnostic sensitivity when evaluating for subtle neurological causes 1

• Vascular imaging (CTA from aortic arch to vertex, carotid ultrasound, or MR angiography) when cerebrovascular disease is suspected 1

Special Considerations

Central vs. Peripheral Causes

• Central causes (brain, spinal cord):

  • Often associated with other neurological symptoms
  • May present with bilateral or multiple limb involvement
  • Consider neuroimaging when suspected 4

• Peripheral causes (nerves):

  • Often follow specific nerve distribution
  • May be associated with sensory loss in the same distribution
  • Consider nerve conduction studies/EMG if symptoms persist 4

Common Pitfalls to Avoid

1. Missing vitamin B12 deficiency:

   • Paresthesia may be the earliest manifestation
   • Can occur without macrocytosis, especially with concurrent conditions affecting red blood cell size 3, 5
   • Consider testing even without anemia

2. Overlooking metabolic causes:

   • Diabetes can cause paresthesia before other symptoms appear
   • Thyroid dysfunction can present with paresthesia

3. Assuming all transient paresthesias are benign:

   • Transient symptoms may represent TIA requiring urgent evaluation
   • Hyperventilation can cause paresthesia through alkaline shift affecting sodium conductance 6

4. Failure to recognize ischemia:

   • Ischemia can trigger paresthesia through membrane depolarization 6
   • Consider vascular evaluation in patients with risk factors

Follow-up Recommendations

• For persistent or progressive symptoms: referral to neurology
• For transient symptoms with normal initial evaluation: consider cardiac evaluation (ECG, extended monitoring) if vascular etiology suspected 1
• For symptoms associated with specific nerve distributions: consider referral for electrodiagnostic testing

By following this structured approach, clinicians can efficiently evaluate new onset paresthesia while avoiding unnecessary testing and ensuring appropriate diagnosis and management of potentially serious underlying conditions.