What is the appropriate work up for a patient presenting with facial numbness?

Workup for Facial Numbness

MRI head without and with IV contrast or MRI orbits, face, and neck without and with IV contrast is the most appropriate initial imaging for patients presenting with facial numbness. 1

Initial Clinical Assessment

• Key history elements to obtain:

  • Onset and progression (sudden vs gradual)
  • Distribution (unilateral vs bilateral)
  • Associated symptoms:
    • Weakness of facial muscles
    • Visual disturbances
    • Hearing changes
    • Vertigo/dizziness
    • Headache
  • Prior history of:
    • Cancer
    • Multiple sclerosis
    • Recent dental procedures
    • Head/neck trauma

• Physical examination focus:

  • Detailed cranial nerve examination (especially trigeminal nerve branches)
  • Facial muscle strength testing
  • Sensory testing of face (light touch, pinprick, temperature)
  • Eye examination for corneal reflex
  • Hearing assessment
  • Balance and coordination testing

Diagnostic Algorithm

Step 1: Neuroimaging

• First-line imaging: MRI head without and with IV contrast OR MRI orbits, face, and neck without and with IV contrast 1
  • These procedures may be complementary depending on institutional protocols
  • High-resolution thin-cut contrast-enhanced MRI is especially useful to evaluate for perineural spread of tumor 1

Step 2: Laboratory Testing (based on clinical suspicion)

• Targeted laboratory testing rather than routine panels 2:
  • Complete blood count
  • Metabolic panel (electrolytes, renal function)
  • Random glucose or HbA1c
  • Vitamin B12 levels when clinically indicated
  • Autoimmune markers if systemic disease suspected

Step 3: Neurophysiological Testing (when indicated)

• Trigeminal somatosensory evoked potential (TSEP) - highly sensitive for detecting trigeminal nerve pathology 3
• Blink reflex (BR) - second most sensitive test, helps localize pontine lesions 3
• Masseter reflex (MR) - may be abnormal in trigeminal nerve pathology 3

Special Considerations by Etiology

Bell's Palsy

• If facial weakness accompanies numbness, consider Bell's palsy
• Electrodiagnostic testing may be offered to patients with complete facial paralysis 1
• Electroneuronography (ENoG) and electromyography (EMG) can provide prognostic information 1

Multiple Sclerosis

• MRI is essential for diagnosis
• TSEP and BR are particularly sensitive in detecting lesions in MS patients with facial numbness 3
• Look for characteristic demyelinating lesions in the pontine tegmentum 3

Vascular Causes

• Aneurysms (particularly anterior inferior cerebellar artery) can present with isolated trigeminal sensory loss 4
• MRI with MRA may be necessary to evaluate for vascular causes

Neoplastic Causes

• Progressive facial numbness may represent early symptomatology of malignancy 5
• Complete imaging workup is essential even for seemingly minor symptoms
• Consider paraneoplastic syndromes in patients with systemic symptoms 6

Important Clinical Pearls

• Facial numbness, especially if progressive, necessitates periodic evaluation and vigilance even years after presentation if no diagnosis can be made 5
• Patients with vertigo and facial numbness should be evaluated for Ménière's disease, which can present with similar symptoms 1
• Numbness may be the earliest sign of serious underlying pathology including malignancy, making thorough evaluation critical 5
• When facial numbness is accompanied by weakness of facial expression, MRI orbits, face, and neck without and with IV contrast has the highest appropriateness rating (9/9) 1

Remember that facial numbness can be the presenting symptom of serious underlying conditions, including tumors, vascular malformations, demyelinating diseases, and systemic disorders. A thorough evaluation with appropriate imaging is essential for accurate diagnosis and management.