Vestibular Schwannoma (Acoustic Neuroma)
Vestibular schwannoma (acoustic neuroma) is a benign (WHO grade 1) tumor arising from the Schwann cells of the balance (vestibular) division of the 8th cranial nerve. It accounts for the great majority of cerebellopontine angle (CPA) tumors. Its most common symptom is unilateral, slowly progressive hearing loss. Most cases are sporadic; a small proportion are associated with inherited Neurofibromatosis type 2 (NF2).
Última atualização: 2026-06-07
Definition
Vestibular schwannoma is a benign tumor arising from the Schwann cells sheathing the vestibular division of the 8th cranial nerve (the vestibulocochlear nerve). It is classified as WHO grade 1 and does not metastasize. It typically begins in the internal acoustic canal and grows over time toward the cerebellopontine angle. Although 'acoustic neuroma' is the traditional name, 'vestibular schwannoma' is more accurate, since the tumor arises from the vestibular (balance) rather than the cochlear (hearing) nerve sheath.
Epidemiology
Vestibular schwannoma is the most common intracranial Schwann cell tumor and makes up the great majority of cerebellopontine angle tumors. The mean age at diagnosis is 50-60 years, and it is slightly more frequent in women. The vast majority of cases are sporadic and unilateral; about one in twenty is associated with inherited Neurofibromatosis type 2 (NF2). In NF2 the tumors are usually bilateral and appear at a younger age; bilateral vestibular schwannoma is a hallmark of NF2.
Symptoms
The most common and earliest symptom is unilateral, slowly progressive sensorineural hearing loss; high frequencies are affected first, and speech discrimination may be difficult even when pure-tone hearing is relatively preserved. Other common symptoms are unilateral ringing in the ear (tinnitus) and a sense of imbalance. Because the tumor grows slowly and the body's balance system adapts, sudden severe vertigo is rare. Large tumors may cause reduced facial sensation (trigeminal nerve), rarely facial weakness (facial nerve), and brainstem compression with hydrocephalus.
Classification
Tumor size and extent are often graded by the Koos classification. Grade 1 is confined to the internal acoustic canal (intracanalicular). Grade 2 extends into the cerebellopontine angle but is small and does not touch the cerebellum. Grade 3 is moderate in size and contacts the cerebellum. Grade 4 is large and compresses the brainstem. This classification guides treatment selection and prediction of outcomes.
Diagnosis
Gadolinium-enhanced brain MRI is the gold standard; thin-slice sequences that detail the internal acoustic canal and cerebellopontine angle can detect even millimeter-sized tumors. The typical appearance is an 'ice cream cone'-shaped, strongly enhancing mass extending from the internal acoustic canal into the angle. Hearing assessment is mandatory in all patients: pure-tone audiometry and the word recognition score (WRS) define the level of serviceable hearing, which directly affects treatment choice. The differential diagnosis includes other angle lesions such as meningioma, epidermoid cyst and arachnoid cyst.
Treatment Options
There are three basic approaches, and the choice is individualized according to tumor size, growth rate, hearing status, the patient's age and preference. For small, asymptomatic or minimally symptomatic tumors and in older patients, active surveillance (watch-and-scan) with regular MRI and audiometry is a safe option, because a significant proportion of tumors never grow or grow very slowly. For moderate-to-large or progressive tumors, microsurgical resection is the curative treatment; the retrosigmoid, translabyrinthine or middle fossa approach is selected according to the goal of hearing preservation and tumor size. For small-to-moderate tumors, stereotactic radiosurgery (Gamma Knife, CyberKnife) is an effective, non-invasive alternative; keeping the cochlear dose low is important for hearing preservation. In progressive NF2-related tumors, targeted systemic therapies such as the VEGF inhibitor bevacizumab may be used.
Prognosis
Vestibular schwannoma is a benign tumor, and with modern treatment the prognosis is very good, with low mortality. Facial nerve preservation rates in surgery are high, especially for small and moderate tumors; hearing preservation is closely related to tumor size and pre-operative hearing quality. Regardless of the treatment option, long-term MRI follow-up is recommended; recurrence rates are generally low. Care is planned by a team including neurosurgery, otolaryngology and, when needed, radiation oncology; outcomes vary from patient to patient and no outcome can be guaranteed.
Referências
- Greenberg MS. Greenberg's Handbook of Neurosurgery. 10th ed. Thieme; 2023:777-802.
- Winn HR, ed. Youmans Neurological Surgery. 6th ed. Saunders; 2011:1461-1471.
- Osborn AG, Hedlund GL, Salzman KL. Osborn's Brain: Imaging, Pathology, and Anatomy. 2nd ed. Elsevier; 2018:710-718.
- Goldbrunner R, et al. EANO guideline on the diagnosis and treatment of vestibular schwannoma. Neuro Oncol. 2020.
Este artigo é informativo e não substitui um exame médico. As decisões de diagnóstico e tratamento são individuais.