Is it uncommon to have two schwannomas (nerve sheath tumors) on a Magnetic Resonance Imaging (MRI) scan of the spine?

Multiple Schwannomas on MRI Spine: Implications and Diagnostic Considerations

Having two schwannomas on MRI spine is uncommon and should prompt evaluation for an underlying genetic syndrome such as neurofibromatosis type 2 (NF2) or schwannomatosis. 1

Diagnostic Implications of Multiple Schwannomas

Multiple schwannomas detected on spinal MRI represent an important clinical finding that warrants thorough investigation:

• Genetic syndromes: Multiple schwannomas are most commonly associated with:

  • Neurofibromatosis type 2 (NF2) - characterized by bilateral vestibular schwannomas
  • Schwannomatosis - multiple non-vestibular schwannomas without other NF2 features
  • Less commonly: LZTR1-related disorders 1

• Diagnostic criteria for NF2 include any of the following 1:

  • Bilateral vestibular schwannomas
  • Family history of NF2 plus unilateral vestibular schwannoma OR any two of: meningioma, glioma, neurofibroma, schwannoma, posterior subcapsular lenticular opacities
  • Unilateral vestibular schwannoma plus any two of the above features
  • Multiple meningiomas plus unilateral vestibular schwannoma OR any two of the above features

Diagnostic Algorithm

1. Brain MRI with dedicated IAC protocol - Essential to evaluate for vestibular schwannomas 1, 2

   • Should include standard T1 and T2-weighted sequences
   • T1-weighted sequences before and after gadolinium administration
   • Axial submillimetric heavily T2-weighted sequences
   • Diffusion-weighted imaging

2. Complete spine MRI - To identify any additional schwannomas not detected on initial imaging 1

3. Genetic testing for:

   • NF2 gene mutations
   • LZTR1 gene mutations (associated with schwannomatosis) 1
   • SMARCB1 and SMARCE1 (less common genetic causes) 1

4. Family history assessment - Critical to identify potential hereditary patterns 1

5. Clinical examination for:

   • Cutaneous manifestations
   • Ophthalmologic findings (posterior subcapsular lenticular opacities)
   • Neurological deficits related to tumor location

Differential Diagnosis

1. Neurofibromatosis type 2 (NF2) 1

   • Bilateral vestibular schwannomas are hallmark
   • Onset often in young adults (median age <30 years)
   • Associated with meningiomas, ependymomas
   • Autosomal dominant inheritance pattern

2. Schwannomatosis 3, 4

   • Multiple schwannomas without vestibular tumors
   • Typically presents in middle age (30s-40s)
   • Often presents with pain as the predominant symptom
   • Usually sporadic (non-familial) cases
   • Genetic testing can help differentiate from NF2

3. Mosaic/Segmental NF2 5

   • Limited to specific body segments
   • May present with multiple schwannomas in a single limb or region

Clinical Implications and Management

• Genetic counseling is essential for patients with multiple schwannomas
• Regular surveillance imaging is recommended:
  • For LZTR1 patients: baseline MRI brain and spine at diagnosis, then every 2-3 years beginning at age 15-19 years 1
  • More frequent imaging if symptomatic
• Surgical management is typically reserved for symptomatic lesions causing pain or neurological deficits 4

Important Caveats

• The presence of multiple schwannomas in young patients (<30 years) should raise high suspicion for NF2, even without vestibular tumors 1
• Schwannomatosis and NF2 have different prognoses and management approaches, making accurate diagnosis crucial 3
• Multiple schwannomas may enlarge during pregnancy, causing new or worsening symptoms 5
• Patients with multiple schwannomas have a high likelihood of developing additional tumors over time, necessitating long-term surveillance 4

The finding of two schwannomas on spinal MRI is an important clinical indicator that should prompt comprehensive evaluation to distinguish between sporadic occurrence, schwannomatosis, and NF2, as these distinctions significantly impact patient management and prognosis.