The role of radiology in the diagnosis and management of vestibular schwannoma

Non-Hodgkin Lymphoma Mimicking Vestibular Schwannoma

Progressive unilateral hearing loss and an MRI are usually enough to diagnose vestibular schwannoma (VS). We were consulted by a 45-year-old man with otalgia and left-sided hearing loss as well as ipsilateral facial paralysis that had begun two weeks prior. Due to a possible atypical presentation of VS, an MRI was ordered, which revealed an intracanalicular lesion occupying the left cerebellopontine angle cistern. With no signs of systemic disease and considering the total left ear deafness, the patient underwent retrolabyrinthine mastoidectomy. During the procedure, a mass incompatible with VS was found and a biopsy was performed, which led to a diagnosis of non-Hodgkin's lymphoma (NHL). The patient was referred to an oncologist for treatment and, in time, achieved complete remission of the lesion. This case shows us that symptoms of VS may vary in tumor size and location and that atypical presentations warrant investigation. Non-Hodgkin's lymphoma (NHL), although not among the most common differential diagnoses, should be remembered due to its varied clinical presentation broadly dependent on its subtype and dissemination.

Is vestibular schwannoma really a benign tumor? Case report and review

Introduction

Vestibular schwannoma (VS) is a benign tumor that develops from Schwann cells of the eighth cranial pair, mainly in the cerebellopontine angle.

Case Presentation

We report the case of a 30-year-old female patient who developed left otalgia associated with neglected tinnitus, the evolution of which was marked by the development of a static cerebellar syndrome and a behavioral disorder, whose brain MRI revealed a locally advanced process in the cerebellopontine angle at the expense of the vestibulocochlear nerve, in favor of a VS, complicated by involvement of the tonsils, which unfortunately led to the patient's death.

Discussion

VS, formerly known as acoustic neuroma, is an extra-axial intracranial tumor that accounts for over 80% of pontocerebellar angle tumors, and is secondary in the majority of cases to inactivation of the neurofibromatosis type 2 (NF2) tumor suppressor gene, either by mutation of the NF2 gene or loss of chromosome 22q. In the majority of cases, it is unilateral and solitary, but in almost 8% of cases, it is associated with NF2. Cerebral MRI is the examination of choice for the detection, characterization, and diagnosis of VS without the need for biopsy, mainly with T1-weighted sequences before and after gadolinium injection. Treatment is based essentially on surgery or radiosurgery, depending on the size, impact, and expertise of the treatment team.

Conclusion

VS remains an important intracranial tumor entity, which can be life-threatening in cases of advanced local invasion.

Brazilian Society of Otology task force - Vestibular Schwannoma ‒ evaluation and treatment

OBJECTIVE

To review the literature on the diagnosis and treatment of vestibular schwannoma.

METHODS

Task force members were educated on knowledge synthesis methods, including electronic database search, review and selection of relevant citations, and critical appraisal of selected studies. Articles written in English or Portuguese on vestibular schwannoma were eligible for inclusion. The American College of Physicians' guideline grading system and the American Thyroid Association's guideline criteria were used for critical appraisal of evidence and recommendations for therapeutic interventions.

RESULTS

The topics were divided into 2 parts: (1) Diagnosis - audiologic, electrophysiologic tests, and imaging; (2) Treatment - wait and scan protocols, surgery, radiosurgery/radiotherapy, and systemic therapy.

CONCLUSIONS

Decision making in VS treatment has become more challenging. MRI can diagnose increasingly smaller tumors, which has disastrous consequences for the patients and their families. It is important to develop an individualized approach for each case, which highly depends on the experience of each surgical team.

Unilateral sudden sensorineural hearing loss with vertigo as a first symptom of bilateral internal auditory canal metastases: a case report

There have been relatively few reports of bilateral internal auditory canal metastases of asymptomatic primary pulmonary adenocarcinoma presenting as unilateral sudden sensorineural hearing loss and vertigo. We report a case of a 60-year-old male patient who complained of sudden hearing loss in the right ear and vertigo. Upon a physical examination, no definite neurological signs or nystagmus were observed. Pure-tone audiometry showed deafness in the right ear at all frequencies and high-frequency sensorineural hearing loss in the left ear. The video head impulse test suggested bilateral vestibulopathy. Magnetic resonance imaging of the brain (with gadolinium contrast) revealed bilateral internal auditory canal enhancement and a variable-sized nodular and peripheral-enhancing lesion in the cerebrum and the right cerebellum. A computed tomographic and bronchoscopic biopsy identified asymptomatic primary pulmonary adenocarcinoma in the left upper lobe of the lungs. This is a rare report of bilateral internal auditory canal metastases in an asymptomatic patient with primary pulmonary adenocarcinoma who initially presented with symptoms of unilateral sudden sensorineural hearing loss with vertigo.

Bevacizumab for NF2-associated vestibular schwannomas of childhood and adolescence

Seventeen children at six institutions with neurofibromatosis type 2 (NF2)-related vestibular schwannomas received bevacizumab. Eight of the 13 patients with initial hearing loss (61%) showed objective hearing improvement within six months of treatment. No patients showed hearing deterioration during therapy; however, only two patients showed objective radiological response. Seven of eight patients had tumor progression or worsening hearing loss upon cessation of treatment. Bevacizumab was well tolerated with no patients discontinuing therapy. Bevacizumab appears to postpone hearing loss in childhood NF2-associated vestibular schwannomas, but responses are not durable, suggesting that either longer maintenance therapy or new strategies are required.

Cost-effectiveness analysis of a non-contrast screening MRI protocol for vestibular schwannoma in patients with asymmetric sensorineural hearing loss

PURPOSE

We aimed to determine if a non-contrast screening MRI is cost-effective compared to a full MRI protocol with contrast for the evaluation of vestibular schwannomas.

METHODS

A decision tree was constructed to evaluate full MRI and screening MRI strategies for patients with asymmetric sensorineural hearing loss. If a patient were to have a positive screening MRI, s/he received a full MRI. Vestibular schwannoma prevalence, MRI specificity and sensitivity, and gadolinium anaphylaxis incidence were obtained through literature review. Institutional charge data were obtained using representative patient cohorts. One-way and probabilistic sensitivity analyses were completed to determine CE model threshold points for MRI performance characteristics and charges.

RESULTS

The mean charge for a full MRI with contrast was significantly higher than a screening MRI ($4089 ± 1086 versus $2872 ± 741; p < 0.05). The screening MRI protocol was more cost-effective than a full MRI protocol with a willingness-to-pay from $0 to 20,000 USD. Sensitivity analyses determined that the screening protocol dominated when the screening MRI charge was less than $4678, and the imaging specificity exceeded 78.2%. The screening MRI protocol also dominated when vestibular schwannoma prevalence was varied between 0 and 1000 in 10,000 people.

CONCLUSION

A screening MRI protocol is more cost-effective than a full MRI with contrast in the diagnostic evaluation of a vestibular schwannoma. A screening MRI likely also confers benefits of shorter exam time and no contrast use. Further investigation is needed to confirm the relative performance of screening protocols for vestibular schwannomas.

Cranial Nerve Schwannomas: Diagnostic Imaging Approach

Schwannomas are benign nerve sheath tumors that may arise along the complex course of the cranial nerves (CNs), anywhere in the head and neck. Sound knowledge of the CN anatomy and imaging features of schwannomas is paramount for making the correct diagnosis. In this article, we review approaches to diagnosing CN schwannomas by describing their imaging characteristics and the associated clinical presentations. Relevant anatomic considerations are highlighted by using illustrative examples and key differential diagnoses categorized according to regions, which include the anterior skull base, orbit, cavernous sinus, basal cisterns, and neck. The clinical presentations associated with CN schwannomas vary and range from no symptoms to symptoms caused by mass effect or CN deficits. Individuals with the inherited disorder neurofibromatosis type 2 are predisposed to multiple schwannomas. When a lesion follows the course of a CN, the radiologist's roles are to confirm the imaging features of schwannoma and exclude appropriate differential considerations. The characteristic imaging features of CN schwannomas reflect their slow growth as benign neoplasms and include circumscribed margins, displacement of local structures, and smooth expansion of osseous foramina. These neoplasms exhibit various degrees of solid enhancement, often with internal cystic spaces on magnetic resonance (MR) and computed tomographic (CT) images and heterogeneous high signal intensity specifically on T2-weighted MR images. Clinical and/or imaging evidence of end-organ compromise of the involved CN may exist and aid in the identification of the nerve of origin. With a detailed understanding of the course of the CNs, the diagnostic features of CN schwannomas, and the correlation between these data and the associated clinical presentations of these tumors, the radiologist can have a key role in the diagnosis of CN schwannomas and the treatment planning for affected patients. (©)RSNA, 2016.

The role of preoperative imaging for cochlear implantation in postlingually deafened adults

BACKGROUND

Preoperative imaging is standard practice for cochlear implant candidacy. Postlingually deafened adults rarely have temporal bone abnormalities that alter management.

OBJECTIVES/HYPOTHESIS

To determine the role of preoperative imaging for cochlear implantation in postlingually deafened adults. We hypothesize that imaging does not alter management in the absence of history or physical examination findings suggestive of an anatomic abnormality.

STUDY DESIGN

Nested case-control study.

METHODS

We identified postlingually deafened adults with preoperative imaging and cochlear implantation at our institution from 1995 to 2008. Controls had a negative history and normal exam. Cases had suggestive history or exam. Imaging studies and operative records were reviewed.

RESULTS

Approximately 164 patients met inclusion criteria-59 cases and 109 controls. Mean age at onset of hearing loss was 30.4 years (range, 0-73 yr), mean age at onset of deafness was 54.1 years (range, 9-89 yr), and mean age at implantation was 61.5 years (range, 20.6-89.7 yr). Twenty cases (34%) and 17 controls (16%) had abnormal imaging (p = 0.001). Six cases (8.5%) and 2 controls (1.8%) had changes in their management as a result of the imaging findings (p = 0.023). Both control patients had incidentally detected acoustic neuromas, which altered the side of the cochlear implantation. There was a strong association between preoperative history and exam findings and abnormality on imaging (p = 0.007). Abnormalities were 3 times more likely in patients with a positive history or exam (OR = 2.98; 95% CI, 1.36-6.54).

CONCLUSION

In patients with a negative history and examination, imaging rarely alters management. MRI may detect incidental vestibular schwannomas in patients with asymmetric hearing losses.

LEVEL OF EVIDENCE

3b, Individual case-control study.

Hearing disorders in brainstem lesions

Auditory processing can be disrupted by brainstem lesions. It is estimated that approximately 57% of brainstem lesions are associated with auditory disorders. However diseases of the brainstem usually involve many structures, producing a plethora of other neurologic deficits, often relegating "auditory symptoms in the background." Lesions below or within the cochlear nuclei result in ipsilateral auditory-processing abnormalities detected in routine testing; disorders rostral to the cochlear nuclei may result in bilateral abnormalities or may be silent. Lesions in the superior olivary complex and trapezoid body show a mixture of ipsilateral, contralateral, and bilateral abnormalities, whereas lesions of the lateral lemniscus, inferior colliculus, and medial geniculate body do not affect peripheral auditory processing and result in predominantly subtle contralateral abnormalities that may be missed by routine auditory testing. In these cases psychophysical methods developed for the evaluation of central auditory function should be employed (e.g., dichotic listening, interaural time perception, sound localization). The extensive connections of the auditory brainstem nuclei not only are responsible for binaural interaction but also assure redundancy in the system. This redundancy may explain why small brainstem lesions are sometimes clinically silent. Any disorder of the brainstem (e.g., neoplasms, vascular disorders, infections, trauma, demyelinating disorders, neurodegenerative diseases, malformations) that involves the auditory pathways and/or centers may produce hearing abnormalities.

Technical nuances of resection of giant (> 5 cm) vestibular schwannomas: pearls for success

Removal of vestibular schwannomas (VSs, or acoustic neuromas) remains one of the most challenging operations in neurosurgery. Giant or huge tumors (> 5 cm) heighten these challenges, and technical nuances play a special role in maximizing tumor resection while minimizing complications. In this article, the senior author describes his technical experience with microsurgical excision of giant VSs. The accompanying video further illustrates these details.