Acoustic Neuroma

Schwannoma

Definition • A usually encapsulated benign tumor composed of differentiated neoplastic schwann cells.

Grading • Corresponds histologically to WHO grade I

Synonym • Neurilemmoma • Neurinoma

Incidence • Is a common tumor of peripheral nerves. • 8% of intracranial and 29% of primary spinal tumor. • High incidence of schwannomas in patients with NF2. • Peak incidence at 40-6- years. • No sex predominant.

Localization • Most commonly arise from peripheral nerves in head and neck and extensor aspects of the extremities. • Tumors are also arise from the spinal and cranial nerve.

Acoustic Neuroma • Definition – Are benign neoplasms of schwann cells that occur predominatly on the vestibular branch of the CN VIII

Pathology • Originates at the transitional zone between schwann cells and oligodendroglia in the vestibular nerves. • Macroscopic – Are lobulated. – Well encapsulated and solid, soft to firm – Sometime can see cystic formation. – Greyish-tan color. – Surrounding structure are usually stretched over the surface of tumor.

Pathology • Microscopic – Tumor are distinguishable from peripheral schwannoma. – Composed of 2 tissue types • Antoni A (are dense,numerous nuclei,firm cytoplasm) • Antoni B (are loose,semipalisading configurations of schwann cells.)

Clinical • Three most common symptoms – Hearing loss (gradual or progressive) (98%) – Tinnitus usually high pitch (70%) – Dysequilibrium (67%)

• Other symptoms – – – – – – –

Headache (32%) Facial numbness Diplopia N/V Otalgia Change of taste Facial weakness

Clinical • Signs – 66% have no abnormal examination except hearing loss. – Abnormal corneal reflex (33%) – Nystagmus (26%) – Facial weakness (12%) – Papilledema (10%) – Babinski sign (5%)

Facial palsy classification

Hearing classification

Imaging

Treatment • Radiotherapeutic option • Surgical

Treatment • Radiotherapeutic option – Radiosurgery • So-called Sterotactic radiosurgery(SRS). • Some reports suggested that there was little risk to cranial nerve function. • And still develop in dose schedule have apparently reduced the CN complication. • Role to use this technology – Small tumors – Patient cannot tolerate to surgery.

Treatment • Surgical consideration – The choice of surgical approach depend on • • • •

Patient age Hearing status Tumor size Surgeon preference

Treatment • Surgical approach – Middle fossa approach – Translabylinthine approach – Suboccipital approach

Contemporary case management • Intracanalicular tumor 5 mm or smaller – The management of these tiny enhancing lesions is still debatable. – Most patient who have small tumors and minimal symptoms, conservative treatment (wait and see) is safe. – First year F/U imaging every 3 month – If tumor not progress, in Second year F/U imaging every 6 month, and then yearly. – If tumor progression was seen and patient have symptoms, definite treatment should be done.

Contemporary case management • Intracanalicular tumors 5-10 mm – When they are truly within the cana, middle fossa approach and posterior fossa approach should be done. – Once tumor has extend beyond the porus, DO NOT use middle fossa approach. – SRS without biopsy is reasonable for lesion of this size.

Contemporary case management • Tumors with CPA extension 10-25 mm – The suboccipital approach is used in all patients who have salvageable hearing. – If hearing is already gone, the translabyrinthine approach is an alternative. – Translabyrinthine surgery is more likely to be used in elderly patient. – SRS still remain an option for these patient.

Contemporary case management • Tumors with CPA extension 25-35 mm – These larger tumors are more difficult to remove, but excellent result should be obtained, and normal facial function is expected in nearly all. – Suboccipital craniotomy is treatment of choice. – Translabyrinthine surgery is still reasonable. – Tumor size 2.5 cm, hearing can be save in about 50%. – If size > 3 cm, hearing can be save in about 10%.

Contemporary case management • Tumors with CPA extension 35-50 mm – Suboccipital craniotomy is reequired. – Greater risk of cranial nerve injury in larger tumor size. – The majority of patients have a temporary postoperative palsy, but almost 90% recover to normal.