Differential Diagnosis of Cerebellopontine Angle lesions

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

2. 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

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

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

7. Features of Acoustic Neuroma: • Centered over the petrous bone • Acute angle with the petrous bone • Extension into the internal auditory canal • Homogenous enhacement • No dural tail • No calcifications

9. Meningioma: • Second most common CPA lesion 3-7 % • Arise 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

10. Features of Meningioma: • Broad base over the petrous bone • Homogenous signal • A small toungue extension into the internal auditory canal without widening it • Homogenous enhacement • dural tail • Calcifications , psammoma bodies • Hyperostosis

11. 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

12. Features of Epidermoid: • Low density Cyst with lobulated margin • CSF like signal (with high signal in diffusion,flair and proton seq • May exert extensive mass effect • Also occur parasellar and rarely itradiploic TI WI T2 WI Proton WI

13. Arachnoid Cyst

14. Trigeminal Neuroma • Similar to vestibular neuoma but arises from the trigeminal nerve

15. Vascular Lesions: 1. Vertebrobasilardolichoectasia: 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) GlomusJugulare GlomusTympanicum

16. Basilar artery Dolicoectasia

17. AICA LOOP

18. Anterior inferior cerebellar artery Giant aneurysm

19. GlomusJugulare

20. Thank You