A 22-year-old student was brought in to a college student health center in a wheelchair by campus safety personnel. She appeared drowsy and was crying softly. She complained of a severe headache and said she was “tired of going through this all the time.” The woman said she had seen spots and become dizzy, then had gotten “the worst headache of my life” while sitting in class. She rated the headache pain at 8 on a 10-point scale and also complained of nausea and photophobia.
The history revealed dizziness that made her “feel as if I’m tipping over” and similar headaches during the previous year. The patient said she had seen “a few doctors” for her symptoms, but that they “could never find anything.” The headaches usually occurred on the left side of her head, lasted hours to days, and were only partially relieved with acetaminophen. The patient could not remember whether she had eaten breakfast and was unsure of what day it was. She described herself as frustrated and began to weep again.
She was currently under the care of a psychologist but seemed uncertain why; she said that she was sexually active and used condoms. She had undergone an appendectomy at age 12. She denied taking any medications besides acetaminophen. She denied smoking or drug use, history of migraine headaches, vision or hearing changes, facial weakness, depression, or anxiety. Her family history included a grandfather with diabetes and hypertension and an uncle with heart disease. The family history was negative for migraine or psychiatric illness.
Because of the patient’s weakness, she was assisted onto the examination table by a nurse. Physical exam revealed a pale, slightly sweaty, overweight, tearful young woman who was slow to respond. Her blood pressure was measured at 134/104 mm Hg; pulse, 100 beats/min; respirations, 14 breaths/min; and temperature, 97.0ºF. Point-of-care testing of blood glucose was 91 mg/dL, and hemoglobin was measured at 12.3 g/dL. The ophthalmologic exam was positive for photophobia and revealed slightly disconjugate gaze with horizontal nystagmus during testing of cranial nerves (CN) III, IV, and VI. The otoscopic exam revealed a slightly injected right tympanic membrane, and there were no apparent hearing deficits.
The neurologic exam showed patellar and brachial deep tendon reflexes equal, grips weak and equal, and the pupillary response intact. The patient was able to stand without assistance, although her gait was slightly unsteady. Because the patient was of college age, the clinician ruled out meningitis by negative Kernig’s and Brudzinski’s signs and absence of fever. Subarachnoid hemorrhage was also a concern when the patient mentioned the “worst headache of my life,” indicating the need for emergent imaging.
The patient’s presentation, it was felt, warranted a 911 call. The emergency medical team arrived, and its members began to question the patient. Discrepancies in the patient’s history during the paramedics’ reexamination led them to question whether an emergency department (ED) visit was necessary, but at the clinician’s insistence, they agreed to transport the student to the ED.
The following day, the student health center clinician was contacted by a member of the hospital ED staff with an update on the patient’s status. Shortly after her arrival at the hospital, she underwent MRI and was diagnosed with a vestibular schwannoma. She had surgery that same evening, during which the surgeon removed most of the tumor. Although the ED staff was not at liberty to provide more complete information, they did inform the clinician that the patient would require radiation for the remainder of the tumor.
Vestibular schwannoma is also known as acoustic schwannoma, acoustic neuroma, acoustic neurinoma, or vestibular neurilemmoma. These tumors arise from perineural elements of Schwann cells, which commonly form and lead to myelination in the vestibular area of CN VIII1 (see figure). They occur with equal frequency on the superior and inferior branches of the vestibular nerve and originate only rarely at the cochlear portion of the eighth cranial nerve. Vestibular schwannomas represent approximately 8% to 10% of brain tumors and 80% to 90% of tumors in the cerebellopontine angle in adults.2 Tumors are distributed evenly across genders, but the majority of diagnosed patients are white.3
Most likely because of improvements in diagnostic technology, the incidence of vestibular schwannoma has increased over the past 30 years. One British research team predicts that one in 1,000 persons will receive a diagnosis of vestibular schwannoma in their lifetime.4 These tumors are most commonly diagnosed in people ages 30 to 60, with a median age of 55.5
A relationship has been demonstrated between neurofibromatosis type 2 (NF2), an autosomal-dominant disease, and the development of vestibular schwannomas.6,7 NF2 has a birth prevalence of one in about 25,000 persons,4,8 and those who inherit the responsible gene inevitably develop vestibular schwannomas.9 Patients with a confirmed diagnosis of vestibular schwannoma should be screened by a geneticist for the NF2 gene; although the tumors are benign, they can cause compression of the vestibular nerve, leading to deafness and balance disorders.10 Schwannomas of the spinal nerves can also occur in persons with NF2.11 Compression of the spinal nerves in these patients can lead to significant morbidity and a shortened average life span.10
NF2 is diagnosed using the following criteria:
1) Bilateral vestibular schwannomas
2) Diagnosis of a family member with either NF2 or unilateral vestibular schwannoma, and
3) Juvenile posterior subscapular lens opacities.9,12,13
Because schwannomas grow slowly, the vestibular system can adapt to the slow destruction of CN VIII. For this reason, patients typically present with unilateral deafness or hearing impairment rather than dizziness.11 Many patients also present with tinnitus and/or vertigo.14,15
Some vestibular tumors remain stable or even regress; others progress, in some cases causing life-threatening complications.16 An extremely rare complication of a vestibular schwannoma was reported in one patient: an intratumoral hemorrhage that led to acute neurologic deterioration and death.17
Since the case patient underwent immediate surgical intervention, it appears she was experiencing significant involvement and it was likely anticipated that without surgical intervention, clinical progression would occur. Her young age could be considered a risk factor for a faster-growing neuroma.18
Clinical Presentation and Diagnosis
Primary care clinicians commonly see patients with complaints of dizziness, lightheadedness, faintness, or a sensation of spinning or tilting. Vestibular schwannoma should be considered in the differential diagnosis of the patient who presents with these complaints, as well as tinnitus or hearing loss.9 The patient with vestibular schwannoma may also have a history of headache, unsteady gait, facial pain, and numbness.19 A partial differential diagnosis is listed in the table20,21). The astute clinician will systematically rule out many of these conditions, since certain other features that may be present (eg, rapid onset, vomiting, fever) do not typically occur in the patient with vestibular schwannoma.
Because the symptoms typically associated with vestibular schwannoma are likely to occur bilaterally in patients with other conditions, unilateral symptoms should alert the clinician to investigate further. The patterns and growth rates of vestibular schwannomas are highly variable and currently unpredictable18 (according to Fortnum et al,14 at least 50% of tumors do not grow within several years after diagnosis); thus, no clear predictors of tumor growth have been identified to assist in the evaluation of an affected patient,16 although faster tumor growth rates have been reported in young patients, and Baser et al18 have called for additional research involving younger persons with vestibular schwannomas.
Standard testing is audiometry followed by MRI, which is considered the most effective means to confirm a diagnosis of vestibular schwannoma.5,14,22
Treatment for Vestibular Schwannoma
Treatment, whether with surgery or radiation, is associated with significant morbidity and possibly decreased quality of life.16 Therefore, distinguishing patients whose tumors will grow and pose a threat to them from those whose tumors are likely to remain stable is central to appropriate management.23
Treatment modalities are considered based on tumor size, growth, presence or absence of tinnitus, and the patient’s preferences and life expectancy.23 In most cases, decision making is complex and should be customized to meet the patient’s individual circumstances. Patients with similar clinical scenarios have been reported to opt for different treatment choices.24
Four treatment options are currently available for patients with vestibular schwannoma:
Serial observation with periodic MRI studies. Since vestibular schwannomas are benign and slow-growing, conservative management can be a reasonable option, particularly if the patient is elderly, the tumor is small, and/or little hearing loss has taken place. However, use of observation is associated with a risk for progressive and permanent hearing loss.2 Between 15% and 50% of patients who opt for serial observation will undergo subsequent surgical intervention, particularly in cases involving worsening tinnitus, balance problems, or hearing loss.23-25
Chemotherapy. Agents including bevacizumab (a humanized monoclonal antibody against vascular endothelial growth factor)8,26,27 and erlotinib (an epidermal growth factor receptor inhibitor) may delay progression or even facilitate regression of vestibular schwannomas.28 Hearing improvement has also been reported in patients with NF2 who were treated with bevacizumab8; research is ongoing.26
Fractionated radiotherapy. Hearing may be preserved in 60% to 95% of patients, depending on levels of dosing to the cochlea, but 3% to 7% of patients will need further treatment.29-31 Radiation treatment is a likely choice in patients with tumors measuring 2.0 cm or less. Larger tumors are considered a surgical disease, and directed radiotherapy may be administered postoperatively (as in the case patient) for residual portions of the tumor.16
Microsurgery. Compared with other treatment modalities, the emphasis of microsurgery is on removing tumors (particularly larger tumors) rather than controlling their growth.29 The three common approaches are retrosigmoid, middle fossa, or translabyrinthine.32-34 Preservation of hearing is reportedly better following retrosigmoid or middle fossa microsurgery, compared with a translabyrinthine procedure (because in the latter, the tumor cannot be exposed without damage to the inner ear).32,35
With any such surgery, risks include cranial nerve damage, leakage of cerebrospinal fluid, and infection.29,32 Postsurgically, about half of patients report frequent headaches, which are persistent in about half of these cases.36-38 Another concern is preservation of the facial nerves, with a risk for temporary facial weakness or dysfunction.3,24,39 Less than 2% of patients who undergo microsurgery require additional treatment.29
Stereotactic radiosurgery. These procedures, which are performed using the Gamma Knife,® the CyberKnife, or the linear accelerator,29,40,41 are considered appropriate for patients with smaller tumors and those who are not candidates for conventional surgery.1 Trigeminal neuropathy, injury to the facial nerves, and hydrocephaly are reported complications of Gamma Knife radiosurgery, but improvements in these technologies are ongoing.1,2,40
The outcome in a patient with vestibular schwannoma depends on the treatment administered, but prolonged follow-up is typically necessary. For patients being managed through observation, annual brain scans are recommended for 10 years, with subsequent scans every three to five years if no tumor growth is seen. For patients who have had surgery, annual brain scans are advised for the successive eight to 10 years, with decreasing frequency if no tumor remains. In patients who undergo radiation, annual scans are recommended for 10 years, then every two years if no tumor growth is detected.36
Psychosocial experiences vary widely among patients who have undergone treatment for vestibular schwannomas. Some are unable to perform necessary or recreational activities, and others must retire early from work.42 Others, however, have minimal disruption in their lives and enjoy a good quality of life. The most difficult consequence of vestibular schwannoma and its treatment, according to patients, is the associated hearing loss.8,19
THE CASE PATIENT
The 22-year-old patient in this case had an atypical presentation of vestibular schwannoma. Although she did present with vertigo, she also complained of headache, nausea, and photophobia—which are rarely reported in investigations of these tumors. She was also younger than the typical patient and did not report tinnitus.
The case patient reportedly underwent surgery and subsequent radiation to treat the remaining portion of her tumor. She suspended her attendance at the college and, as of this writing, has not re-enrolled. She was lost to follow-up.
For the primary care provider, diagnostic challenges require great clinical acumen. Vertigo, headache, hearing loss, and tinnitus are all symptoms seen in the primary care setting; when they occur together, the clinician should be alerted to investigate further. A high level of suspicion is appropriate when a patient complains of longstanding auditory symptoms, with or without headache. Unilateral hearing loss is a common symptom in patients with vestibular schwannomas, although some may present with facial weakness or pain, imbalance, and/or vertigo.
In addition to the history and physical exam, experts recommend that audiometry and MRI be considered, particularly if hearing loss is unilateral. Genetic screening for NF2 should be performed if vestibular schwannoma is found on MRI. Referral to a neurologist, a neurosurgeon, or an otolaryngologist is appropriate.
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