The document provides an overview of common lesions found in the cerebellopontine angle (CPA) region, including their anatomy, clinical features, radiology, and differential diagnosis. It discusses several pathologies that can occur in the CPA such as acoustic neuromas/vestibular schwannomas, meningiomas, epidermoids, arachnoid cysts, and trigeminal neuromas. For each condition, it outlines key diagnostic elements on imaging studies like CT and MRI scans that can help differentiate between possible lesions.

1. Mumtaz Ali
JPMC KARACHI

2. Outlines
 Anatomy of CPA
 Possible lesions of CPA
 Clinical features
 Differential diagnosis
 Radiology
 Diagnostic elements

3. CPA anatomy
CP angle:
 Irregularly shaped
 extra-axial
 potential space
 Between cerebellum & pons in posterior fossa
 lateral to pre-pontine cisterns

4. 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. CONTENTS
 CSF
 arachnoid tissue
 cranial nerves
 vessels

8. POSSIBLE LESIONS OF CP ANGLE
 Nerve structure: schwanoma
 Meninges : Meningioma ,arachnoid cyst & metastasis
 Cisternal space :epidermoid cyst ,dermoid cyst &
lipoma
 Vascular : aneurysms , AVM & paraganglioma
 Cerebellar ventricles : epindymoma ,lymphoma &
glioma
 Skull base : chondroma ,pituitary adenoma &
cholestrol granuloma

9. Clinical features
 Chochlear CN-VIII : asymmetric sensorineural
hearing loss & tinnitus
 Vestibular CN-VIII : dysequilibrium & vertigo
 CN-VII : facial weakness
 CN-VI : lateral rectus palsy
 CN-IX : dysphagia
 CN-X : hoarsness & aspiration
 CN-XI : shoulder weakness
 Brainstem : headache ,visual loss & ataxia

10. Continue…
 Cerebellum:
 Nystagmus
 Finger-nose test
 Dysdiodokinesia
 Intentional Tremor
 Scanning Speech
 Wide gait
 Falling on ipsilateral side
 Romberg sign

11. Differential Diagnosis
 Accoustic neuroma/Vestibular schwanoma
 Meningioma
 Epidermoid
 Arachnoid cyst
 Dermoid cyst
 Trigeminal neuroma
 Metastasis

12. Accoustic neuroma
 In 1777, Eduard Sandidort
 Most common CPA tumor
 60-92% of CPA lesions
 benign & encapsulated tumor
 Schwann cells
 rubbery tissue with nodular surface

13. Continue….
 yellow and gray areas with interspersed foci of
hemorrhage and cyst
 Vestibular division of CN-VIII
 Inferior vestibular nerve > superior vestibular nerve

14. Histopathological types
 Antonie A:
spindle-shaped cells with rod-shaped nuclie,
dense reticulin arranged in fascicles
 Antonie B:
stellate cells
smaller hyperchromatic nuclei
Less reticulin
prominent cytoplasmic processes
large myxoid stroma

17. Radiology
 CT scan
 Non-contrast: isodense ,no calcification
 IV contrast : inhance homogenously
 Gas cisternogram : no longer used
 MRI
T1 : isointense to brain & hyperintense to CSF
T2 : hyperintense to brain & iso/hypointense to CSF
Gadolinium : enhancement of tumor on T1

18. Diagnostic elements
• Centered on Porus Acousticus
• "Ice cream on cone" pattern (intracanalicular
extension)
• Acute angles to petrous bone
• Often involves the IAC
• Homogeneous enhancement
• No dural tail
• No calcifications
 S-100 & vimentin

22. Auditory brain response(ABR)
 Stimulus =chochlear nerve + auditory pathway
 sensitivity = 92% to 98%
 Specificity = 80% to 90%

24. Meningioma
 2nd most common CPA tumor (3-7%)
 well-circumscribed
 globular or lobulated
 non-glial tumor
 arachnoidal cells:CN foramina , venous sinuses

25. Continue….
 clearly demarcated from the brain
 Usually arise : posterior surface of petrous
 Usually do not extend : IAC
 Vimentin & EMA

26. Diagnostic elements
 Arise : petrous bone (broad base)
 Obtuse angles to petrous bone
 Uncommonly involves the IAC
 "dural tail" sign (50-75%)
 Calcifications common (25%)
 Pial vessel flow voids
 Psammoma body
 Herniate into middle fossa (50%)

27. Continue…..
 Hyperstosis
 Homogenous signal
 Homogenous enhancement
 Extension:small ,internal auditory canal

30. 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

31. Continue….
 Extra-axial lesions
 spread along the basal surface
 Rupture : aseptic meningitis
 Overwhelmingly benign

32. Diagnostic Elements
 Dumb bell : middle fossa or contralateral cistern
 Non-enhancing (25% mild peripheral enhancement)
 CT usually shows a mass hypodense to CSF
 Inhomogeneous lesion
 cauliflower surface appearance
 T1 - hypo-isointense

33. Continue….
 T2 - hyperintense
 (high protein,high signal=T1 & low signal=T2)
 FLAIR : iso-hyperintensity
 Diffusion weighting:characteristic moderate intensity
(restriction of diffusion)

35. Arachnoid cyst
 Loculated collections of CSF
 reduplication of arachnoidal membrane
 Erosion of the adjacent calvarium is often present

36. Diagnostic elements
 Avascular cystic mass
 Nonenhancing
 Smooth regular shape
 Homogeneous
 identical signal to CSF in all weighting

37. continue
 No calcifications
 FLAIR :intense signal suppresion
 Diffusion weighting : hypointensity (no restriction of
diffusion

39. Dermoid cyst
 Midline lesions
 rarely invade the CPA laterally
 elements from all layers of the skin
 FLAIR, CISS and DWI:diagnostic
 MR appearance depends : amount of fat
 increased signal : T1 & T2

41. Trigeminal neuroma
 Similar to vestibular neuoma
 arises from the trigeminal nerve

43. Thank You