Primary Lymphoma of Internal Acoustic Meatus Mimicking Vestibular Schwannoma-A Rare Diagnostic Dilemma

Abstract

Background/Setting A subject presenting with a unilateral sensorineural hearing loss and with vertigo/imbalance and a lesion of internal acoustic meatus (IAM) most often represents a vestibular schwannoma. Several alternative pathologies involving the region, with clinical and neuroradiological similarities, could lead to an error in judgement and management. Rare tumors of the IAM pose unique diagnostic difficulty. A rare case that we present here had a typical history and imaging findings suggestive of vestibular schwannoma. A primary central nervous system (CNS) lymphoma was diagnosed in later stages of brain involvement warranting a retrospective analysis of the entity. Case Summary An 80-year-old male presented with unilateral sensorineural hearing loss, vertigo, and imbalance. On imaging, he was found to have a lesion in the left internal auditory meatus, reported as a vestibular schwannoma and operated upon. Subject's condition worsened with time and a repeat imaging was suggestive of a CNS lymphoma with lesions involving bilateral cerebellum and subcortical white matrix. Conclusion To conclude, primary CNS lymphoma presenting an isolated lesion in the IAM with no other parenchymal lesions at presentation is a rare incidence; to our knowledge this is the first case of such unique presentation.

Keywords: CNS lymphoma; imaging of internal acoustic meatus lesions; internal acoustic meatus; vestibular schwannoma.

Fig. 1

( A , B ) Coronal T1 postcontrast and coronal T2 images showing moderately enhancing lesion in the left internal auditory canal. ( C ) Small enhancing lesion in the right cerebral hemisphere. The lesion is fluid-attenuated inversion recovery hyperintense and hypoperfused.

Fig. 2

( A ) Axial T2-weighted imaging showing patchy area of altered signal intensity scattered in bilateral cerebellar hemisphere. ( B ) Axial fluid-attenuated inversion recovery images showing area of hyperintensities in cerebellar hemisphere. ( C , D ) On axial T1-weighted images, these areas of altered signal intensity show moderate heterogenous enhancement.

Fig. 3

( A , B ) Axial fluid-attenuated inversion recovery images showing area of altered signal intensity in left thalamus and basal ganglia region. ( C ) Axial arterial spin labeling image showing hyperperfusion in these regions of altered signal intensity. ( D ) On axial T1-weighted images, these areas of altered signal intensity show moderate heterogenous enhancement.

Fig. 4

( A , B ) Whole body positron emission tomography computed tomography image showing no area of abnormal metabolic activity apart from focal hyperperfusion seen in the thalamocapsular region.

Fig. 5

( A ) Axial FIESTA magnetic resonance imaging showing nodular T2 hypointense lesion in left cerebellopontine angle cistern extending into the internal acoustic meatus. ( B ) Diffusion-weighted imaging (B = 1,000) does not show any altered diffusivity or restricted diffusion.