Imaging of Hearing Loss

Transcription

1 Contemporary Imaging of Sensorineural Hearing Loss Imaging of Hearing Loss Discussion Outline (SNHL) Imaging Approaches Anatomic Relationships Lesions: SNHL KL Salzman, MD University of Utah School of Medicine Imaging Choice By Anatomic Area Temporal Bone CT External auditory canal Middle ear-mastoid Temporal (CPA/IAC) MRI Membranous labyrinth Internal auditory canal ICA & venous segments Anatomic Approach Results from lesion affecting the vestibulocochlear nerve (CN 8) or nucleus Typically in CPA or IAC Vestibular Schwannoma 90% MR best imaging modality Hearing Loss CT Technique Bone algorithm Slice thickness: mm Axial plane with multiplanar reformatted images IV contrast: None 4000 window width ideal CT is best imaging tool for CHL CPA-IAC: Anatomy Brainstem-IAC IAC CPA cistern Choroid plexus CN7 & CN8 Brainstem Restiform body (ICP) Cerebellum Flocculus

2 IAC Anatomy Contents Facial nerve Cochlear nerve Superior vestibular n. Inferior vestibular n. Horizontal crest/vertical bar Crista falciformis/bill s bar Pre-cochlear implant Schwannoma origin Imaging for Adult SNHL or CPA-IAC Lesion Recommendations T1 C+ MR is gold std + high-res T2 screening High-res T2 images contain more surgical data Fundal cap? Nerve of origin if small? Cochlear nerve canal?, Adult Vestibular Schwannoma Common Vestibular Meningioma Epidermoid Aneurysm T-bone fracture Less Common Cochlear otosclerosis Metastases Facial n. Large endolymphatic sac anomaly (IP-2) Intralabyrinthine Rare But Important Endolymphatic sac tumor Sarcoid Superficial siderosis Ramsay Hunt syndrome Most common CPA-IAC mass Unilateral SNHL & tinnitus From vestibular nerve sheath Differential Diagnoses: Meningioma Facial nerve CN9-11 Metastases Vestibular Schwannoma Intracanalicular Vestibular Schwannoma T1 C+ MR: Enhances T2/CISS/SPACE/FIESTA MR: Filling defect Fundal CSF cap? Cochlear nerve canal? Nerve of origin? Imaging Features: Large Intracanalicular: Cone CPA: Ice cream T2 MR: Filling defect T1 C+ MR: Enhances 15% cysts Intramural Marginal <1%: Arachnoid cyst/csf <1%: Hemorrhage

3 Vestibular Schwannoma Vestibular Schwannoma Caveat Uncommon Features 15% with intramural cystic component Punctate intramural Larger intramural Marginal cyst(s) Beware the Small VS! Follow up with imaging Neuro-otology literature full of reports: Nothing there with + imaging Micro-hemangioma, AVM,... Follow with imaging Problem getting worse with higher field strength MR Tumor Arachnoid cyst Intracanalicular Vestibular Schwannoma CPA Meningioma Nerve of Origin = Superior Vestibular Nerve 2nd most common CPA mass Unilateral SNHL & tinnitus May be incidental MR finding Arachnoid cap cells origin Differential Diagnosis: Sarcoidosis (Dural-based) Metastasis, dural type Vestibular CPA Meningioma MR Imaging Findings Flat, dural based lesion +/- tail sign Asymmetric to porus CSF-vascular cleft +/- IAC component Brain edema signals possible surgical problems & recurrence potential CPA Meningioma Trigeminal neuralgia

4 CPA Epidermoid Slow growing, often clinically silent for years May be incidental Presentation age: 40 Etiology Ectodermal rests left during neural tube closure Congenital cholesteatoma CPA Epidermoid MR Features Insinuating morphology T1 & T2 signal follows CSF FLAIR: Lack of suppression Diffusion (DWI): Restricted diffusion No enhancement CPA PICA-AICA Fusiform Aneurysm CPA Aneurysm T2-FSE MR T1 C- MR 3rd most common finding in unilateral SNHL screening Present with SNHL CPA mass with complex MR signals PICA > VA > AICA CPA PICA-AICA Aneurysm, Adult Common Vestibular Meningioma Epidermoid Aneurysm T-bone fracture Less Common Cochlear otosclerosis Metastases Facial n. Large endolymphatic sac anomaly (IP-2) Intralabyrinthine Rare But Important Endolymphatic sac tumor Sarcoid Superficial siderosis Ramsay Hunt syndrome

5 Facial Nerve Schwannoma MR: Enhancing tubular mass along course of facial nerve CT: Enlarged FN canal Geniculate ganglion region most commonly involved May mimic vestibular SNHL, tinnitus or FN dysfunction Intralabyrinthine Schwannoma Arise within membranous labyrinth MR: Enhancing mass Mass named by location CPA-IAC Intralabyrinthine Schwannoma Intracochlear Intravestibular Transmodiolar Transmacular Transotic Intractable dizziness Progressive growth Transmodiolar SNHL: Endolymphatic Sac Tumor CT: Spiculated Ca++ in mass, posterior wall MR: T1 hyperintense related to blood products Heterogeneous enhancement Most sporadic VHL in minority Axial Bone CT Intracochlear, Adult Common Vestibular Meningioma Epidermoid Aneurysm T-bone fracture Conservative management Surgical treatment reserved for: SNHL Less Common Cochlear otosclerosis Metastases Facial n. Large endolymphatic sac anomaly (IP-2) Intralabyrinthine Rare But Important Endolymphatic sac tumor Sarcoid Superficial siderosis Ramsay Hunt syndrome Endolymphatic Sac Tumor

6 Endolymphatic Sac Tumor - VHL Neurosarcoidosis Multi-systems granulomatous disease of unknown cause Nodes, skin, L-S, lacrimal glands and meninges (5%) Differential Diagnosis Diffuse: Mets, NHL Solitary: Meningioma Bilateral ELST = VHL Superficial Siderosis Bilateral SNHL, ataxia, pyramidal signs Chronic blood deposition on brain & cranial nerves Recurrent bleeding Raw brain or spine surface Vascular tumor, aneurysm, other Spine MR if not site seen! Summary Key Points SNHL: Vestibular ~90% Meningioma, epidermoid cyst, arachnoid cyst and aneurysm ~ 5% Other etiologies ~ 5% (metastases, sarcoid, labyrinthitis, ILS) Beware very small (1 mm) IAC lesion! Very small vestibular may be a vessel or other normal structure