What is the workup for a patient presenting with paresthesia (abnormal sensations) over the face?

Workup for Facial Paresthesia

A thorough history and physical examination focused on specific neurological findings should be the initial approach to facial paresthesia, with targeted diagnostic testing based on clinical suspicion rather than routine laboratory or imaging studies. 1, 2

Initial Assessment

History - Key Elements to Assess:

• Onset characteristics (sudden vs. gradual progression) 1
• Distribution pattern (unilateral vs. bilateral)
• Associated symptoms:
  • Dizziness, dysphagia, or diplopia (suggesting causes other than Bell's palsy) 1
  • Hyperacusis or viral prodrome 1
  • Visual disturbances
  • Headache or altered mental status 2
• Past medical history focusing on:
  • Prior stroke
  • Brain tumors
  • Skin cancers on head/face
  • Parotid tumors
  • Recent facial/head trauma
  • Recent infections 1

Physical Examination:

• Complete cranial nerve assessment (all 12 nerves) 1
• Sensory testing of all trigeminal nerve divisions
• Motor function assessment of facial muscles
• Skin examination for lesions or scars (especially in patients with history of skin cancer) 3
• Neurological examination for other focal deficits

Red Flags Requiring Further Investigation

• Progressive segmental facial nerve dysfunction (median delay to diagnosis: 9 months) 3
• Well-localized paresthesia, formication, or neuralgia in trigeminal distribution (median delay to diagnosis: 19 months) 3
• Immunocompromised status 3
• History of facial radiation therapy 3
• Lack of improvement within 2-3 months 4
• Additional neurological deficits beyond facial involvement 4
• Recurrent episodes of facial paresthesia 4
• History of head/neck or cutaneous malignancy 4, 3

Diagnostic Testing

Laboratory Testing:

• Do not obtain routine laboratory testing for facial paresthesia without specific clinical indications 1, 2
• Consider targeted testing only when clinically indicated:
  • Lyme disease serology in endemic areas 1
  • Complete blood count, electrolytes, renal function if systemic disease suspected 2
  • Random glucose or HbA1c if metabolic causes suspected 2
  • Vitamin B12 levels if deficiency suspected 2

Imaging:

• Do not routinely perform diagnostic imaging for facial paresthesia 1, 2
• Consider neuroimaging only for specific indications:
  • Focal neurological deficits
  • Sudden onset with concern for TIA/stroke
  • Progressive symptoms
  • Associated headache
  • Altered mental status
  • History of malignancy or immunocompromised state 2
• Gadolinium-enhanced MR Neurography for persistent/progressive cranial nerve V or VII dysfunction with red flags 3

Differential Diagnosis Framework

Central Causes:

• Ischemic events (stroke, TIA)
• Structural lesions (tumors, compression)
• Inflammatory conditions (multiple sclerosis)
• Infections 5

Peripheral Causes:

• Idiopathic (Bell's palsy) - accounts for approximately 70% of facial nerve palsies 1
• Entrapment syndromes
• Metabolic disturbances
• Trauma
• Connective tissue diseases
• Toxin exposure
• Hereditary conditions
• Malignancies (particularly perineural spread of cutaneous squamous cell carcinoma) 3
• Nutritional deficiencies 5

Special Considerations

• Distinguish between paresis (incomplete palsy) and paralysis (complete loss of function), as this affects prognosis and treatment approach 6
• Paresthesias can occur from ectopic impulse activity in healthy axons due to:
  • Hyperventilation
  • Ischemia
  • Release from ischemia
  • Prolonged nerve stimulation 7
• Be cautious about premature closure on Bell's palsy diagnosis without considering other etiologies 4

Referral Indications

• Low threshold for referral to a Head and Neck Surgeon for:
  • Persistent symptoms beyond 2-3 months
  • Progressive symptoms
  • Presence of red flags
  • Abnormal imaging findings 3