Surgery

Last Updated: 03/28/17

Index

  1. Decompression
    • Lesion Management Options
    • Removal Methods
  2. Vestibular Schwannoma Surgery
    1. Translab Approach
      (Translabyrinthine)
    2. Mid Fossa Approach
      (Middle Fossa)
    3. Suboccipital Approach
      (Retrosigmoid / Keyhole Approach)
    4. Bone Decompression
    • Cochlear Nerve Monitoring (Sound)
    • Facial Nerve Graft
  3. Reference Sources

Definitions

  • Lesion = Tumor, Damage Area or
    Abnormality in Tissue

Surgery, also known as Microsurgery, is physical intervention of the body for a treatment. Like any other form of treatment, it is not without risk.

Surgery is currently the ideal treatment for tumors for people with NF2. While NF2 tumors are slow growing, it can allow the brain and body to have time to try to adapt and adjust which can allow a tumor to grow to a considerable size before treatment might be necessary. Continuous growth of any tumor or tumors can result in a serious health issue with the need for surgical intervention dependent on tumor size, location and how bad the side effects are or can become if a tumor increases any further. Individuals with NF2 can develop two but up to hundreds of tumors, but not every tumor that grows will require treatment.

Reasons surgery might be required could be; 1) dangers to one nerve, 2) danger to multiple nerves, 3) brain compression, or 4) brainstem compression.

Tumors in different locations brain and body grow at different rates, brain tumors often grow faster than spinal cord or body tumors, but even tumors in different areas of the brain would likely grow at different rates in the same individual.

Tumor growth for individuals with NF2 is the result of damage of a tumor suppressor element that is meant to prevent growth of tumors. Since it is not in the body to fight growth, radiation or radiosurgery treatment options which put individuals at risk of other tumor growth, might help treat one tumor but risk creating or risk growth of other tumors in the surrounding areas up to many cm away from the treated tumor.

It is always possible a tumor may seem to grow back after surgery, however, NF2 tumors, Schwannoma, but especially Vestibular Schwannoma (VS) are difficult to have completely removed if not removed by a surgeon who has removed NF2 VS. The growth of these tumors is often different from the Vestibular Schwannoma growth of individuals who might have these tumors are but not as a result of NF2. A different name for NF2 VS is currently being considered.

Some surgical options are described here.

1. Decompression

Decompression, also known as Resection or Excision, is currently the most effective means of tumor management for NF2 at this time. However, since this only helps one tumor at a time and individuals with NF2 tend to have a vast number of tumors, a better treatment needs to be found.

I. Lesion Management Options

With Decompression Surgery, there are two options:

  1. Excision: Complete Removal of a Tumor
  2. Excision, complete removal is the ideal option when possible. It guarantees the tumor would not need to be dealt with again to cause future complications unless it for some reason grows back.

  3. Debulked: Removal of Part of a Tumor, Partial (or Subtotal) removing some of the bulk of the tumor mass.
  4. There are different types of tumors, but Schwannoma tumors grow as a part of the nerve, and complete removal of these tumors can cause damage to a vital nerve. If a tumor is large enough, partial removal can relieve pressure of the immediate health issue. However, this typically results is tumor regrowth and there is no way to know at what rate before more issues arise to require additional surgery later. It is important to understand that Cranial Nerves, also known as major nerves in the brain, do not heal like nerves in other parts of the body and damage done will not repair itself.

  • Concern: Decompression Concerns - Glial Scars
  • In an attempt for the body to heal, each surgery will result in Glial Scars. This buildup of damaged cells in the brain can eventually result in seizures.

II. Removal Methods

  1. Craniotomy: When bone from the skull is temporarily removed from to access the tumor in the brain.
  2. Endoscopic Surgery: Some areas in the brain that were previously inoperable locations can now be accessed easily and safely through the sinuses or eye. These methods of tumor removal can be used to decrease operation time, are minimally invasive approaches and therefore result in safer surgeries.
  3. Endoscopic Endonasal Surgery is the removal of a tumor through the sinuses and the Transorbital Neuroendoscopic Surgery (TONES) Approach), is surgery through the eye.


2. Vestibular Schwannoma Surgery

Due to a lack of MERLIN (Moesin-Ezrin-Radixin-Like Protein), which is the result of the missing or mutated Tumor Suppressor Gene, individuals with NF2 develop an overabundance of Schwann Cells. The result of this overabundance of cells is the growth of Schwannoma tumors along nerves in the Central Nerve System. The highest concentration of Schwannoma tumors typically grow on the Vestibular Nerves, this is why they are called Vestibular Schwannoma. The Vestibular Nerves are responsible for balance, but balance issues can also be adapted for visually and other parts of the brain over time and with physical therapy. Tumors that grow on a Vestibular Nerve will typically also damage the Cochlear Nerve. The Cochlear Nerve is responsible for the function of the Cochlea and therefor hearing.

The Vestibular Nerve and the Cochlear Nerve are nerve branches of the Vestibulocochlear Nerve, CN8. The three surgical approaches used to remove Vestibular Schwannomas (Acoustic Neuromas) include the: Translab Approach, Mid Fossa Approach and Suboccipital Approach.[1] [2]

I. Translab Approach (Translabyrinthine([3]

With the Translab Approach, the surgical entry point to remove a tumor is through the ear canal.

  • Pro: Facial Nerve has best chance at being saved.
  • Con: Hearing Loss and Balance problems are guaranteed.

II. Mid Fossa Approach (Middle Fossa Approach (MCF), or Middle Cranial Fossa Approach (MCFA)) [4] [5]

With the Mid Fossa Approach, the surgical entry point to remove a tumor is over and forward from the ear.

  • Pro: Best chance at saving hearing, only an option for smaller tumors.
  • Con: High risk of damage to the Facial Nerve and there is a chance of possible risk of problems with speech and memory.

III. Suboccipital Approach (Retrosigmoid Approach (RSA) also known as Keyhole Approach)[5]

With the Suboccipital Approach, the surgical entry point to remove a tumor is behind and below the ear.

  • Pro: Chance at saving Hearing and Facial Nerve.
  • Con: 50% of patients lose hearing and there is a high risk of consistent regular headaches.

IV. Bone Decompression

Decompression of the Middle Cranial Fossa, the canal that holds the tumor and the nerve, take the bone out around it and see if you can relieve the pressure. Unlike the Translab, Mid Fossa and Suboccipital Approach this is not a long term solution.[6]

Surgeries included above might require:

Cochlear Nerve Monitoring

There is a better quality of sound with a Cochlear Implant, but monitoring the Auditory Nerve during surgery would allow for an Auditory Brainstem Implant (ABI) if this nerve is not strong enough following tumor removal. Surgery later just to implant an ABI at a later point would result in an individual being deaf for months and is otherwise an invasive surgery.

Facial Nerve Damage

If the Facial Nerve (CN7) might be damaged during surgery, either an EMG or a Mechanical-Pressure Monitor might be used to monitor the nerve strength. If the Facial Nerve loses connectivity during surgery, a Nerve Graft might be done when the nerve is being damaged, or later in Facial Reanimation Surgery as well as the possibility of a Free Muscle Transplant.

3. Reference Sources

  1. Zanoletti, E., Martini, A., Emanuelli, E., & Mazzoni, A. (2012). Lateral approaches to the skull base. Acta Otorhinolaryngologica Italica, 32(5), 281. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3546400/
  2. Chamoun, R., MacDonald, J., Shelton, C., & Couldwell, W. T. (2012). Surgical approaches for resection of vestibular schwannomas: translabyrinthine, retrosigmoid, and middle fossa approaches. Neurosurgical Focus, 33(3), E9. http://thejns.org/doi/abs/10.3171/2012.6.FOCUS12190
  3. Brackmann, D. E., Cullen, R. D., & Fisher, L. M. (2007). Facial nerve function after translabyrinthine vestibular schwannoma surgery. Otolaryngology--Head and Neck Surgery, 136(5), 773-777. http://171.67.121.218/content/136/5/773.short
  4. Wang, A. C., Chinn, S. B., Than, K. D., Arts, H. A., Telian, S. A., El-Kashlan, H. K., & Thompson, B. G. (2013). Durability of hearing preservation after microsurgical treatment of vestibular schwannoma using the middle cranial fossa approach: Clinical article. Journal of neurosurgery, 1-8. http://thejns.org/doi/abs/10.3171/2013.1.JNS1297
  5. Rabelo de Freitas, M., Russo, A., Sequino, G., Piccirillo, E., & Sanna, M. (2011). Analysis of Hearing Preservation and Facial Nerve Function for Patients Undergoing Vestibular Schwannoma Surgery: The Middle Cranial Fossa Approach versus the Retrosigmoid Approach-Personal Experience and Literature Review. Audiology and Neurotology, 17(2), 71-81. http://www.karger.com/Article/Fulltext/329362
  6. Bedi, Anupama D., Steven A. Toms, and Amir R. Dehdashti. "Use of hemostatic matrix for hemostasis of the cavernous sinus during endoscopic endonasal pituitary and suprasellar tumor surgery." Skull Base 21.3 (2011): 189. http://www.ncbi.nlm.nih.gov/pmc/articles/pmc3312110/
  7. Ceylan, Savas, Kenan Koc, and Ihsan Anik. "Extended endoscopic approaches for midline skull-base lesions." Neurosurgical review 32.3 (2009): 309-319. http://link.springer.com/article/10.1007/s10143-009-0201-9
  8. Rivkin, Mark A., Alan R. Turtz, and Kenneth E. Morgenstern. "Trans-orbital endoscopic removal of posterior lateral orbital mass: A technical note." The Laryngoscope (2013). http://onlinelibrary.wiley.com/doi/10.1002/lary.24228/abstract
  9. Mandigo, C. E., & McCormick, P. C. (2012). Asymptomatic Intradural Schwannoma: Surgery Versus Radiosurgery Versus Observation. Best Evidence for Spine Surgery: 20 Cardinal Cases (Expert Consult-Online), 103. http://books.google.com/books?hl=en&lr=&id=wVgCSGT_ILoC&oi=fnd&pg=PA103&dq=NF2,+when+to+remove+Schwannoma,+spinal+cord&ots=wwRrfAs-2S&sig=-IrrTfFsIIHp6e3J1R3lxXOl5XI
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