What is the management plan for a 30-year-old female patient with bilateral vestibular schwannoma (acoustic neuroma), with the right-sided tumor measuring 3.7cm and compressing the brainstem, causing mass effect and right facial palsy, and the left-sided tumor measuring 2.5cm, given significant growth from previous magnetic resonance imaging (MRI) scans?

Management of Bilateral Vestibular Schwannoma with Brainstem Compression

For this 30-year-old female with bilateral vestibular schwannoma showing rapid growth and brainstem compression, surgical decompression of the right-sided tumor (3.7cm) is urgently needed, followed by a staged approach for the left-sided tumor. 1, 2

Initial Assessment and Management

Right-sided Tumor (3.7cm with brainstem compression and facial palsy)

• Immediate surgical intervention is required for the right-sided tumor due to:
  • Large size (3.7cm, Koos grade IV)
  • Brainstem compression with mass effect
  • Existing facial nerve palsy
  • Significant growth from 2cm to 3.7cm in one year 1

Surgical Approach for Right Side

• Retrosigmoid (retromastoid) approach is recommended as it:
  • Provides excellent visualization of the brainstem and cranial nerves
  • Allows access to large tumors with brainstem compression
  • Is the preferred approach for neurosurgeons dealing with large tumors 1, 2

Surgical Goals for Right Side

• Near-total resection rather than gross total resection to prioritize facial nerve preservation given the existing facial palsy
• Intraoperative monitoring is mandatory, including:
  • Facial nerve monitoring (direct electrical stimulation and free-running electromyography)
  • Somatosensory evoked potentials
  • Electromyography of lower cranial nerves 1

Management of Left-sided Tumor (2.5cm)

• Staged approach - Address the left-sided tumor after recovery from right-sided surgery
• Options for left-sided tumor (medium-sized, 2.5cm):
  1. Stereotactic radiosurgery (SRS) - Preferred option given:
     • Medium size (2.5cm)
     • Lower risk profile than surgery
     • Better preservation of facial nerve function 1, 2
  2. Surgical resection - Alternative if SRS is contraindicated or patient preference is for definitive treatment

Follow-up Protocol

• Post-surgical MRI of right-sided tumor within 48-72 hours to document extent of resection
• Regular MRI surveillance:
  • Every 6 months for the first 2 years
  • Annually thereafter for at least 5 years 1
• More frequent imaging may be needed due to:
  • NF2 status (suspected based on bilateral tumors in a young patient)
  • Potentially increased growth rate of left-sided tumor after right-sided surgery 3

Special Considerations

1. Neurofibromatosis Type 2 (NF2) Evaluation

   • Bilateral vestibular schwannomas in a young patient strongly suggest NF2
   • Genetic testing should be performed
   • Consider bevacizumab as adjunctive treatment if NF2 is confirmed (evidence class II, recommendation level B) 1, 2

2. Accelerated Growth Risk

   • Research shows that after resection of one vestibular schwannoma in NF2, the contralateral tumor may grow faster (VDE increased from 2.5 to 4.4 mm/year) 3
   • This necessitates closer monitoring of the left-sided tumor after right-sided surgery

3. Auditory Rehabilitation

   • Plan for hearing rehabilitation as bilateral tumors will likely result in significant hearing loss
   • Consider cochlear implant or auditory brainstem implant options 2

Pitfalls to Avoid

1. Delaying treatment of the right-sided tumor with brainstem compression, which could lead to irreversible neurological deficits or death
2. Attempting gross total resection at the expense of facial nerve function
3. Inadequate follow-up - Even after complete resection, regular monitoring is essential
4. Treatment at low-volume centers - Outcomes are better at high-volume centers with experienced surgical teams 2
5. Overlooking accelerated growth of the left-sided tumor after right-sided surgery 3

This management plan prioritizes addressing the immediate threat to life and neurological function from the right-sided tumor while preserving facial nerve function as much as possible, followed by appropriate management of the left-sided tumor and comprehensive follow-up.