How common is it to have two spinal lesions likely schwannoma (schwann cell tumors)?

Multiple Spinal Schwannomas: Prevalence and Clinical Significance

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

Epidemiology and Prevalence

• Vestibular schwannomas are usually solitary tumors; however, about 4-6% are associated with NF2 2
• Multiple schwannomas in the spine without vestibular schwannomas may represent schwannomatosis, which is an extremely rare tumor syndrome 3
• In patients with NF2, spinal tumors are remarkably common, with MRI studies showing spinal tumors in 89% of NF2 patients 4

Genetic Syndromes Associated with Multiple Schwannomas

Neurofibromatosis Type 2 (NF2)

• Autosomal dominant condition caused by pathogenic variants in the NF2 gene on chromosome 22q 2
• Birth incidence of about 1 in 25,000-33,000 with a diagnostic prevalence of around 1 in 60,000-70,000 2
• Diagnostic criteria include:
  • 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 conditions 2

Schwannomatosis

• Characterized by multiple schwannomas without the typical signs of NF1 or NF2 3
• Often associated with mutations in SMARCB1 or LZTR1 genes 1
• LZTR1 pathogenic variants can present with apparently isolated vestibular schwannomas at young ages (particularly <25 years) 2

Diagnostic Approach for Multiple Spinal Schwannomas

Imaging

• Complete spine MRI is necessary to identify any additional schwannomas 1
• Brain MRI with dedicated internal acoustic canal protocol is essential to evaluate for vestibular schwannomas 2, 1
• MRI protocol 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

Genetic Testing

• Testing for NF2 gene mutations is recommended 1
• Additional genetic testing for LZTR1, SMARCB1, and SMARCE1 mutations should be considered 1
• NF2 should be considered when an individual presents with a unilateral vestibular or other sporadic schwannoma at <30 years 2
• Mosaic NF2 can be confirmed if an identical NF2 pathogenic variant is found in both tumors 2

Clinical Implications and Management

Surveillance

• Regular surveillance imaging is recommended for patients with multiple schwannomas 1
• For patients with confirmed genetic syndromes, baseline MRI of brain and spine at diagnosis, then every 2-3 years 1
• Given the high incidence of developing additional lesions in patients with schwannomatosis, serial brain and spinal cord MRI studies during follow-up are imperative 3

Treatment

• Surgical management is typically reserved for symptomatic lesions causing pain or neurological deficits 1
• Asymptomatic lesions may be monitored with serial MRI studies 3
• Multiple schwannomas may become symptomatic during pregnancy, as reported in cases of sporadic NF2 5

Important Considerations

• The presence of multiple and different pathologic types of spinal tumors is highly suggestive of NF2 4
• Schwannomatosis patients typically do not exhibit phenotypic overlap with the neurofibromatoses 6
• The recurrence rate after microsurgical tumor removal is 0.5-5%, highlighting the importance of postoperative follow-up imaging 7

In conclusion, multiple spinal schwannomas are uncommon and warrant thorough investigation for underlying genetic syndromes, particularly NF2 and schwannomatosis, which have significant implications for patient management, surveillance, and genetic counseling.