Diagnosis of Acoustic Neuromas

Signs and Symptoms of Acoustic Neuromas

The symptoms of acoustic neuromas often appear so gradually that a person does not recognize them or they become accustomed to them and may not seek medical attention until they become more severe. In fact, many of the small, asymptomatic acoustic neuromas are discovered incidentally when a person is being evaluated for another problem.

The symptoms of acoustic neuromas include:

• Hearing loss on one side (unilateral)
• Impaired speech discrimination
• Tinnitus (ringing in the ears)
• Vertigo
• Vestibular dysfunction (problems with balance)
• Facial nerve dysfunction
• Headache
• Difficulty swallowing

Small tumor symptoms typically include unilateral sensorineural hearing loss, some level of impaired speech discrimination, vertigo, and tinnitus. Additional symptoms noted with larger tumors may include trigeminal or facial nerve dysfunction, vestibular imbalance, and elevated intracranial pressure (with very large tumor). Symptoms continue to intensify with progressive growth of the tumor.

In a 1998 Members' Survey of the Acoustic Neuroma Association, reported symptoms prior to treatment were hearing loss (88%), imbalance (64%), tinnitus (64%), feeling of fullness in the ear (43%), headache (33%), facial numbness (22%), facial weakness (16%), facial twitching (13%) change in taste or smell (10%), and difficulty swallowing (7%). Many of these patients had large tumors. It is important to note, however, that data varies widely regarding the percentage of patients presenting with various symptoms at the time of diagnosis.

Hearing Loss

The most common symptom of acoustic neuroma is the gradual reduction of hearing in one ear, which occurs in up to 95% of patients. Hearing loss may occur with or without the presence of tinnitus (ringing or roaring sound in the ear). The hearing loss may be so subtle that it is often overlooked or is believed to be associated with the normal process of aging. The patient typically presents with a slowly progressive, high frequency, sensorineural hearing loss on the affected side but some patients (5-15%) experience a sudden or fluctuating hearing loss.

Unilateral hearing loss is such a hallmark symptom of acoustic neuromas that clinicians will often make a diagnosis of acoustic neuroma until proven otherwise. At the time of diagnosis of acoustic neuromas, only 3-5% of patients are thought to have full hearing capacity.

The hearing loss typically worsens over a period of many years and may eventually result in total deafness in the affected ear. If a person experiences a complete and sudden loss of hearing, it is often associated with a viral infection or vascular occlusion. Some patients may also experience both low and high frequency hearing loss. A small number of people may experience hearing loss in both ears. It is thought that hearing loss may actually initially develop 3-4 years before the diagnosis of acoustic neuroma is confirmed.

Impaired Speech Discrimination

Patients with acoustic neuroma may have a decreased ability to perceive and discriminate speech sounds (words), particularly sounds at higher frequencies. A person may complain of difficulty understanding someone speaking on the telephone even though they can hear them, locating where sounds are coming from, or understanding the speech of soft-spoken people or young children. Speech discrimination is affected disproportionately more than would be expected from the coexisting hearing loss. Problems with speech discrimination are not always present at diagnosis so that normal scores on tests of speech discrimination should not rule out a diagnosis of acoustic neuroma.

Approximately 50% of patients with small tumors may experience reduced speech discrimination while up to 70% of people with larger acoustic neuromas may complain of compromised accuracy of speech discrimination.

Tinnitus

Tinnitus - a ringing or roaring in the ears - is an indication of cochlear nerve dysfunction and is a common symptom of acoustic neuromas. In the majority of cases, the tinnitus is high pitched and only occurs in the ear affected by the tumor (unilateral). A small number of patients, however, may experience bilateral tinnitus. It is generally regarded as an early symptom of acoustic neuroma. Tinnitus rarely appears without accompanying hearing loss though hearing loss may be experienced without tinnitus. Investigators from the Mayo Clinic reported that that 70% of patients with acoustic neuromas experienced tinnitus. To read more about this study, click on the following link: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=Abstract&listuids=7301081&queryhl=4&itool=pubmed_docsum

Vertigo

True vertigo, a disabling sensation in which an individual feels that his/her surroundings are in constant motion, occurs in about 19% of people with acoustic neuromas. It is more commonly experienced in the early growth stages of the tumor when it is small.

Vestibular (Balance) Dysfunction

As the tumor grows and places pressure on the vestibulocochlear nerve, patients may also experience balance problems or unsteadiness on their feet. In many cases, however, this symptom goes undetected because the vestibular system is very good at compensating for the loss of equilibrium which may further delay diagnosis. Approximately 50% of patients with large tumors suffer from problems of vestibular dysfunction. These problems appear more frequently with larger tumors due to increased compression on the vestibular nerve.

Cerebellar dysfunction is characterized by intention tremor and gait ataxia (unsteadiness while walking). True cerebellar dysfunction is less common in people with acoustic neuromas and is often limited to patients with large tumors. When this occurs, patients tend to fall towards the side where the tumor is located.

Facial Nerve and Trigeminal Nerve Dysfunction

Other cranial nerves may also be affected by tumor growth. If the 7th cranial nerve, the facial nerve, is compressed by the tumor, a person may experience facial weakness on the affected side, slurred speech, difficulty closing the eyelid, and decreased or absent corneal reflex. It is estimated that approximately 25% of patients experience facial numbness while facial weakness is relatively uncommon.

Compression of the 5th cranial nerve, the trigeminal nerve, which is responsible for facial sensation, may result in facial paresthesia (a "pins and needles" tingling) or anesthesia (loss of feeling and sensation) especially in the cheeks as well as difficulty chewing. Symptoms of facial numbness and tingling are often indicative of a larger tumor pressing against the trigeminal nerve. The numbness and tingling can occur intermittently or be constant. Symptoms related to the trigeminal nerve correlate with the size of the acoustic neuroma. If the tumor is less than 1 cm. in size, there is typically no pain whereas if it is larger than 3 cm, up to 48% of patients complain of symptoms associated with acoustic neuromas. Some studies indicate that, on the average, approximately 10% of patients present to the clinician with trigeminal nerve involvement at the time of diagnosis.

Headache

Some patients with acoustic neuromas complain of headaches which may at times be accompanied by nausea and/or vomiting. It is estimated that headaches may be experienced by 50-60% of patients at the time of diagnosis. Headaches may be indicative of elevated intracranial pressure (pressure within the skull) and are usually associated with late stage tumor growth. The headaches may develop under certain circumstances including:

• Upon waking in the morning
• May wake up the patient during the night
• Exacerbated by reclining or lying down
• Exacerbated by standing up
• Exacerbated by coughing, sneezing, straining, or lifting
• May be accompanied by nausea and/or vomiting

Swallowing Difficulties

If the 9th, 10th, or 12th cranial nerves are compressed, a person may experience difficulty swallowing and/or speaking. Difficulty swallowing can also be related to pressure against the trigeminal nerve.

Life-Threatening Symptoms

When a large tumor significantly compresses or distorts the brainstem, symptoms can include nausea, vomiting, and lethargy that can lead to coma, respiratory depression, and death. Immediate medical attention should be sought for the patient. Increased cranial pressure can lead to papilledema (swelling of the optic nerve) and life-threatening hydrocephalus (an abnormal increase in the amount of cerebrospinal fluid within the ventricles of the brain).