Differential Diagnosis of Cerebellopontine Angle lesions By NourEldin

Differential Diagnosis of Cerebellopontine Angle lesions By: Nour-Eldin A Mohammed Referrence: Stephan Chapman 2003

Cerebellopontine Angle � Extra-axial area lateral to the prepontine cistern containing CSF, arachnoid tissue, cranial nerves and their associated vessels. Borders � Medial: lateral surface of the brainstem � Lateral : petrous bone � Superior : middle cerebellar peduncle & cerebellum � Inferior : arachnoid tissue of lower cranial nerves � Posterior : cerbellar peduncle

Differential Diagnosis: 1. Vestibular Schwannoma (acoustic neuroma). Most Common Cause 2. Meningioma 3. Epidermoid cyst 4. Trigeminal neuroma 5. Vertebrobasilar system aneurysm 6. Metastases 7. Skull base/temporal bone tumours: eg, glomus tumors, metastases, cholesterol granuloma 8. Skull base infection: osteomyelitis of the petrous apex (Gradengo’s syndrome) , Malignant otitis externa

Acoustic Neuroma � Comprises � Involve nerve 60 -92% of CPA lesions the vestibular division of the 8 th cranial

Features of Acoustic Neuroma: 1. Centered over the petrous bone 2. Acute angle with the petrous bone 3. Extension into the internal auditory canal 4. Homogenous enhacement 5. No dural tail 6. No calcifications

Meningioma: � Second � Arise most common CPA lesion 3 -7 % from cap cells near arachnoid villi which are more prominent near cranial nerve foramina and venous sinuses. � Usually arise from posterior surface of the petrous bone and usually do not extend into IAC

Features of Meningioma: 1. Broad base over the petrous bone 2. Homogenous signal 3. A small toungue extension into the internal auditory canal without widening it 4. Homogenous enhacement 5. dural tail 6. Calcifications , psammoma bodies 7. Hyperostosis

Epidermoid Cyst: � Accounts for 2 -6 % of CPA masses � Congenital lesions that present in adulthood � Rests of ectodermal tissue containing stratified squamous lining and keratin � May arise within the temporal bone or in the CPA

Features of Epidermoid: 1. Low density Cyst with lobulated margin 2. CSF like signal (with high signal in diffusion, flair and proton seq 3. May exert extensive mass effect 4. Also occur parasellar and rarely itra diploic T 2 WI TI WI Proton WI

Arachnoid Cyst

Trigeminal Neuroma � Similar to vestibular neuoma but arises from the trigeminal nerve

Vascular Lesions: 1. Vertebrobasilar dolichoectasia: Enlongation and dilitation of the vertebrobasilar artery. Symptomas : Facial spasm, trigeminal neuralgia 2. AICA loop May loop over, under, or between CN VII & CN VIII. Symptoms - vertigo 3. Giant Aneurysms 4. Hemangioma 5. Paragangliomas (may extend to CPA) Glomus Jugulare Glomus Tympanicum

Basilar artery Dolicoectasia

AICA LOOP

Anterior inferior cerebellar artery Giant aneurysm

Glomus Jugulare

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