Clinical Pearls & Morning Reports
Published April 7, 2021
Widespread access to sensitive neurodiagnostic imaging has led to a notable rise in the detection of vestibular schwannomas; an increasing proportion of cases are diagnosed, often incidentally, when the tumor is small and the patient is at an advanced age. Read the NEJM Review Article here.
Q: What are the most common presenting symptoms of vestibular schwannoma?
A: Sporadic unilateral vestibular schwannomas account for more than 95% of cases. The most common presenting symptoms encompass ipsilateral sensorineural hearing loss in more than 90% of patients, dizziness or imbalance in up to 61%, and asymmetric tinnitus in 55%. There is a limited association between tumor size and the severity of hearing loss, tinnitus, or dizziness at diagnosis, and symptom progression is not strongly correlated with tumor growth.
Q: How is vestibular schwannoma diagnosed?
A: Thin-slice, gadolinium-enhanced magnetic resonance imaging (MRI) of the head is the standard diagnostic approach for the detection of vestibular schwannomas as small as 2 mm in diameter. Features seen on imaging are highly sensitive and specific, resulting in an accurate radiologic diagnosis in most cases, without the need for a confirmatory biopsy.
A: Treatment strategies can be divided into an observational wait-and-scan approach, irradiation, microsurgery, and a combination of these methods. To date, there is no high-level evidence indicating that one treatment approach is unequivocally superior to others. Typically, tumors that have a maximal diameter of less than 1.5 cm in the cerebellopontine angle are considered for a wait-and-scan approach. Given the unpredictable nature of tumor growth and the capacity for saltatory or delayed growth, lifelong follow-up is recommended. The aim of radiosurgery for a schwannoma is to prevent tumor growth; treatment does not confer a radiographic cure, and the tumor will be visible indefinitely on MRI. Tumors that are less than 2.5 cm are preferred in order to minimize the risk of radiation-induced brain-stem edema, trigeminal neuropathy or neuralgia, and hydrocephalus, as well as diminished long-term tumor control. Microsurgical resection can be performed on tumors of all sizes and is the treatment of choice for large tumors associated with symptomatic brain-stem compression, hydrocephalus, trigeminal neuralgia or neuropathy, or a combination of these complications. Microsurgery is generally preferred for the treatment of tumors that are larger than 3 cm in diameter. However, in the absence of high-level evidence to inform decision making, there are multiple reasonable treatment options for most patients with small or medium-size vestibular schwannomas, including the wait-and-scan approach, radiosurgery, and microsurgery. As such, patient preference plays a major role in shared decision making.
A: An important ramification of increased disease detection is a potential for overtreatment, which could result in unnecessary complications and health care expenditures. Many patients, who just decades ago would have lived out their lives without having their tumors detected, are now receiving treatment. Though the proportion of cases initially managed with a wait-and-scan strategy is higher than ever before, paradoxically, the total number of vestibular schwannomas per population that are treated with irradiation and microsurgery is probably greater today than in prior decades. Nevertheless, a growing proportion of patients now undergo active monitoring of the tumor with serial imaging, signifying a transition in clinical care from up-front microsurgical resection, which epitomized treatment in earlier eras, to management of chronic disease.