Acoustic neuroma is an intracranial slow-growing tumor of the vestibulocochlear nerve arising from the Schwann cell of the nerve sheath. The growing acoustic neuroma occupies a large portion of the cerebellopontine angle and accounts for approximately 80% of all the tumors of the cerebellopontine angle. The incidence of acoustic neuroma is around 1 case per 100,000 individuals and it is constantly on a rise. Acoustic neuroma has no specific risk factor, but exposure to ionizing radiation has been implicated in the development of the tumor. The bilateral acoustic tumor has also been associated with a genetic disorder known as neurofibromatosis type 2.(1)
What Happens To Untreated Acoustic Neuroma?
The advancement in audiological evaluation and imaging techniques has led to the diagnosis of smaller acoustic neuromas. Surgical management of acoustic neuroma is associated with complications such as hearing loss, brainstem stroke, facial paralysis, and postoperative cerebrospinal fluid leak. These potential complications have led to the selection of patients for nonsurgical management of acoustic neuromas with watchful waiting with follow up radiological imagings. In the nonoperative group, the tumor grows at a rate of around 0-0.2 cm per year. It is also noted that over time the growth pattern of acoustic neuromas become predictable. There are various factors that can influence the growth pattern of the tumor including the cellular turnover rate, hemorrhage, infarction, cystic degeneration, and scarring. For this reason, it is important to assess tumor growth with serial imaging.(2)
Selective patients with slow-growing and smaller tumors can be managed conservatively with wait can watch technique; however, larger tumors may require surgical intervention. Since tumor regression has also been noted; therefore, it is important to select patients who should be conservatively managed and who require microsurgery depending on the tumor growth rate, patient age, overall health, bilateral hearing ability, and patient preference.(2)
When To Go To Doctor For Acoustic Neuroma?
The most common symptom of acoustic neuroma is a unilateral hearing loss at the time of diagnosis seen in approximately 80% of all cases. The hearing loss is mostly sensorineural, which can be caused either due to direct injury to the cochlear nerve or disruption of its blood supply. The hearing loss is mostly slow and progressive; however, sudden and fluctuating (noted in 5-15% of cases) may also be noted when there is an interruption in the blood supply of the cochlear nerve. There is also a reduction in speech discrimination scores that can be measured by ‘rollover’ audiological testing. The other common symptom noted along with hearing loss is tinnitus.
Although tinnitus is mostly associated with hearing loss, some patients may just have tinnitus without any accompanying hearing loss.(1)
Vertigo and disequilibrium are rare presenting symptoms of acoustic neuroma and the illusion of movement of falling, though not common can be seen with small acoustic neuroma. Disequilibrium, which is a sense of imbalance or unsteadiness, is more commonly seen with larger tumors. Some form of balance disturbance is seen in around 40-50% of patients. Headache is seen in around 50-60% of the patients with acoustic neuroma. Headache is directly proportional to the size of the tumor and is more prominent in patients with obstructive hydrocephalus that is commonly associated with larger tumors.(1)
Facial numbness is seen in approximately 25% of all the patients and is more common than facial weakness. Larger tumors are associated with objective hypoesthesia that involves teeth, buccal mucosa or facial skin; however, a subjective loss of sensation is most commonly associated with small to medium-sized tumors. A reduction in the corneal reflex may also be noted. Facial weakness is relatively uncommon, seen only in <1% of all cases. Facial weakness can be associated with other conditions, namely, facial neuroma, meningioma, hemangioma, granuloma, lipoma, or an arteriovenous malformation.(1)
All these symptoms should prompt a patient to visit a doctor of which unilateral sensorineural hearing loss and tinnitus are more commonly associated with acoustic neuroma.
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