What is the recommended management approach for a patient with fibromatosis type 2?

Management of Neurofibromatosis Type 2 (NF2)

Primary Treatment Strategy

For NF2 patients with small vestibular schwannomas (<1.5 cm) and preserved hearing (speech discrimination ≥70%), hearing-sparing microsurgery is the first-line treatment, while bevacizumab should be reserved for patients with larger tumors, progressive disease, or when surgery would result in hearing loss. 1

Initial Assessment and Surveillance

• Obtain baseline head MRI at diagnosis, followed by imaging every 6 months for the first year, then annually thereafter 1
• Use volumetric tumor measurements rather than linear measurements to accurately detect growth and guide treatment decisions 1
• Assess hearing function with pure-tone audiometry and speech discrimination testing at each visit 2

Treatment Algorithm for Vestibular Schwannomas

Surgical Candidates (Treatment-Naive Patients)

Proceed with hearing-sparing microsurgery when ALL of the following criteria are met: 1

• Tumor diameter <1.5 cm
• Speech discrimination scores ≥70% in both ears
• Tumor incompletely fills the lateral internal auditory canal
• Tumor originates from superior vestibular nerve

Surgical approach: Use retrosigmoid or middle fossa approach for optimal hearing preservation 1

Medical Therapy Candidates

Use bevacizumab (7.5 mg/kg IV every 3 weeks) for: 1

• Tumors >1.5 cm with preserved hearing
• Progressive disease on serial imaging
• Patients where surgery would result in unacceptable hearing loss
• Bilateral disease where surgery on one side has already resulted in hearing loss

Expected outcomes: Hearing improvement occurs in 36% of patients, with no hearing deterioration during 12-month treatment 1

Observation Strategy

If hearing is preserved following surgery on the first tumor and the unoperated ear retains serviceable hearing, careful observation is required before further surgery 2

Management of Associated Tumors

Meningiomas (Present in 50-60% of NF2 Patients)

Surveillance approach: Clinical and MRI follow-up at 6 months, then yearly, as very few patients develop new meningiomas 2

Surgical indications: 1

• Significant tumor growth on serial imaging
• Parenchymal edema
• Neurologic deficit
• Intractable seizures
• Intracranial hypertension

Spinal Tumors (Present in 70% of NF2 Patients)

Surgical indications: 1

• Symptomatic tumors with radiological progression
• Consider surgery even for asymptomatic tumors showing progression to preserve neurological function

Important caveat: NF2 ependymomas are usually indolent and rarely require surgery 2

Hearing Rehabilitation Options

When First-Side Surgery Results in Hearing Loss

Step 1: If hearing is lost with <60% word discrimination on the unoperated side, perform promontory stimulation on the first ear 2

Step 2 - Cochlear Implant: If positive auditory stimulation is present, consider cochlear implant with hope for long-term sustained viability and excellent speech discrimination 2, 1

Step 3 - Auditory Brainstem Implant (ABI): If neither cochlear nerve is stimulated, proceed with multichannel ABI 2, 1

• Provides useful auditory sensations in most deaf NF2 patients
• Improves communication ability compared to lip reading alone
• Can offer significant ability to understand speech using only sound from the ABI

Controversial: Radiosurgery and Radiotherapy

The use of radiosurgery and radiotherapy for NF2 management is highly controversial. 2

Potential benefits: Stereotactic radiosurgery with dose <13 Gy may facilitate hearing preservation and minimize cranial nerve deficits for growing vestibular schwannomas 1

Major concerns: 2, 1

• Risk of inducing malignancy, including secondary meningiomas and multiple small tumors
• Lack of thorough data on risks, benefits, and outcomes specific to NF2
• Patients requiring microsurgical resection after stereotactic radiosurgery face increased likelihood of subtotal resection and decreased facial nerve function

Clinical recommendation: Avoid radiosurgery/radiotherapy as first-line treatment given these concerns, particularly in young patients with long life expectancy 2

Critical Management Pitfalls

Patient Burnout

After multiple surgeries and treatments, patient engagement becomes challenging 1

• Discuss realistic expectations early
• Involve patient advocacy groups to reinforce explanations
• Consider trials with predictable and optimal outcomes to maintain engagement

Post-Radiosurgery Complications

Patients who have failed radiosurgery may become therapy-resistant and face worse surgical outcomes 1

Premature Bilateral Surgery

If hearing is not preserved following surgery on the first tumor, do NOT proceed immediately with surgery on the second side if the unoperated ear retains serviceable hearing 2

Multidisciplinary Team Requirements

Essential team members include: 1

• Medical genetics
• Neurosurgery and neurotology
• Neurology
• Audiology
• Radiology
• Psychology
• Physiotherapy
• Specialist nurses