Cerebellopontine Angle Syndrome - Treatment: Surgical

Treatment: Surgical

Surgical removal remains the treatment of choice for tumor eradication. Three different approaches are used in the management of acoustic neuromas: the retrosigmoid, translabyrinthine, and middle fossa approaches. All have advantages and disadvantages as indicated below.

Advantages of the retrosigmoid approach

• The retrosigmoid approach can be applied to all acoustic tumors and to many other histologic tumor types. It can be used for operations that sacrifice hearing and operations that attempt to conserve hearing. Its only limitation in this respect is its inapplicability for small tumors that occupy the far-lateral portions of the internal auditory canal.
• The retrosigmoid approach provides the best wide-field visualization of the posterior fossa. The inferior portions of the cerebellopontine angle and the posterior surface of the temporal bone anterior to the porus acusticus are much more clearly observed than via the translabyrinthine approach. Panoramic visualization is especially helpful when displacement of nerves is not predictable, which occurs commonly with meningiomas.
• Hearing conservation surgery can be attempted even for relatively large tumors via the retrosigmoid approach. Destruction of the labyrinth is not required as part of the retrosigmoid approach.

Disadvantages of the retrosigmoid approach

• The retrosigmoid approach may require cerebellar retraction or resection. Manipulation of the cerebellum provides opportunities for postoperative edema, hematoma, infarction, and bleeding.
• Increased incidence of cerebrospinal fluid leak occurred in some series.
• The retrosigmoid approach is associated with greater likelihood of severe protracted postoperative headache.
• The highest incidence of tumor recurrence or persistence occurs with retrosigmoid approaches.

Advantages of the translabyrinthine approach

• The translabyrinthine approach provides the best view of the lateral brain stem facing the acoustic tumor.
• Retraction of the cerebellum is almost never necessary.
• The fundus and lateral end of the internal auditory canal are completely exposed; the facial nerve can be identified at a location where it is undistorted by tumor growth and compressed into the labyrinthine segment, decreasing the risk of delayed postoperative facial nerve palsy.
• Incidence of cerebrospinal fluid leak is decreased in some series.
• If the facial nerve has been divided or sacrificed, the translabyrinthine approach may allow restoration of the facial nerve continuity by rerouting the facial nerve and performing a primary anastomosis. Consequently, interposition graft can sometimes be avoided.
• Facial function is more frequently preserved in some series.

Disadvantages of the translabyrinthine approach

• Hearing sacrifice is complete and unavoidable.
• The inferior portions of the cerebellopontine angle and cranial nerves are not as well visualized as they are in the retrosigmoid approach. The temporal bone anterior to the porus acusticus is also less well visualized.
• A fat graft is required. Removal of fat from the abdomen creates opportunities for donor site complications, including hematoma, bleeding, and infection.
• The sigmoid sinus is more vulnerable to injury. Bleeding from the sigmoid sinus can be difficult to control and can significantly increase operative blood loss. If a dominant sigmoid sinus is occluded during the operation, postoperative intracranial pressure elevation or venous infarct can occur.
• A high jugular bulb or anteriorly placed sigmoid sinus can substantially compromise the space available for tumor removal. Occasionally, the space is so contracted that another approach has to be selected.

Advantages of the middle cranial fossa approach

• It is the only procedure that fully exposes the lateral third of the internal auditory canal without sacrificing hearing.
• It is extradural.

Disadvantages of the middle cranial fossa approach

• The facial nerve generally courses across the anterior superior portion of the tumor. Consequently, it is in the way during tumor removal and is more vulnerable to injury. Although long-term facial nerve outcomes are as good with the middle cranial fossa approach as with other approaches, temporary postoperative paresis is more common.
• The risk of dural laceration and avulsion becomes increasingly more likely as patients become older. The dura mater in elderly patients is more friable. This becomes especially noticeable during the sixth and seventh decades of life.
• The approach provides only very limited exposure of the posterior fossa.
• The operation is technically difficult and demanding.
• Some patients incur postoperative trismus related to manipulation and/or injury to the temporalis muscle.
• The temporal lobe must be retracted, presenting the opportunity for temporal lobe injury, usually in the form of a hematoma that is asymptomatic and, therefore, probably occurs more frequently than is realized. Scattered reports exist of seizure disorder following middle cranial fossa surgery, presumably due to temporal lobe injury.