Dr/ ABD ALLAH NAZEER. MD.

Radiological imaging of cerebello-pontine angle mass lesions.

The cerebellopontine angle is the anatomic space between the cerebellum and the pons.Borders:-Medial- Lateral surface of the

brain stem.- Lateral- Petrous bone.-Superior- Middle cerebellar peduncle and cerebellum.

-Inferior- Arachnoid tissue of lower cranial nerve.

-Posterior- Cerebellar peduncle.-Contents- CSF, arachnoid tissue, cranial nerves and their associated vessels.

Anatomy.

A. Solid Masses: Schwannoma

The schwannoma is a benign tumor, composed entirely of

Schwann cells. The neurofibroma is a well-differentiated

nerve sheath tumor composed predominantly of Schwann

cells and, to a lesser extent, fibroblasts and perineural

cells. In small lesions, the parent nerve can be detected

within the tumor; in larger tumors the relationship between

the nerve and the tumor becomes obscured.

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

RIGHT ICA NEUROFIBROMA of the VIII nerve: mass lesion with inhomogeneous enhancement due to small necrotic areas, developed in the right CPA centered on the

IAC with intracanalicular extension associating slight enlargement (confirmed by CT scan)

Left vestibular schwannoma.

Right vestibular schwannoma.

NEUROFIBROMATOSIS TYPE II: bilateral acoustic schwannoma; left CPA meningioma.

NEUROFIBROMATOSIS TYPE II: bilateral acoustic schwannoma.

(typical “ice cream on cone” appearance). Bilateral vestibular schwannomas are diagnostic of neurofibromatosis type 2.

Trigeminal schwannoma.

Trigeminal schwannoma.

Schwannoma with left ear pain.

Meningioma Meningiomas are well-circumscribed, globular

or lobulated, vascular, non-glial tumors of the

central nervous system arising from arachnoidal

cells, clearly demarcated from the brain

Diagnostic elements: • Arise from surface of petrous bone Obtuse angles to petrous bone Uncommonly involves the IAC Frequently with "dural tail" sign (linear enhancement along the dura matter on either side of the tumor) Calcifications common Pial vessel flow voids

LEFT PCA MENINGIOMA: nodular lesion with intense enhancement and extra-axial topography developed in the left CPA, with a broad base and obtuse angles to the petrous bone.

Left CP angle Meningioma.

GIANT MENINGIOMA of the left sphenoidal region, with multiple extensions to both sphenoidal sinuses, posterior ethmoidal cells, engulfing the left internal carotid artery, and with extension to the posterior fossa (left CPA) including nerves V, VI, and VII on the left side.

B. Cystic Masses: Arachnoid cyst

Loculated collections of CSF within a reduplication of

arachnoidal membrane.

Erosion of the adjacent calvarium is often present.

Diagnostic elements:

•Avascular cystic mass

•Nonenhancing

•Smooth regular shape

•Homogeneous, identical signal to CSF in all

weightings

•No calcifications •FLAIR sequence shows intense signal suppresion

Diffusion weighting will show a hipointensity (no restriction of diffusion).

RIGHT PCA ARACHNOID CYST: cystic lesion at the level of the right CPA, with identical signal to the CSF in all weightings, with slight mass effect on the right cerebellar hemisphere. Right side cranial nerves VIII and VII appear enveloped in the cysternal segment, but with no significant course alteration

Left arachnoid cyst.

Large cystic lesion of the left posterior cerebellopontine angle.

Epidermoid cyst

Extra-axial lesions which typically spread along the basal

surface. Rupture can produce aseptic meningitis.

Overwhelmingly benign.

Diagnostic elements:

•May dumbbell into middle fossa or contralateral cistern

•Nonenhancing (25% mild peripheral enhancement

•CT usually shows a mass hypodense to CSF

•Inhomogeneous lesion, highly variable in shape with a

cauliflower surface appearance

•T1 -hypo-isointense; T2 -hyperintense (if it has a high

protein content, it may have high signal

•on T1 and low signal on T2 MR sequences = "white

epidermoid.”

•FLAIR sequence shows iso-hyperintensity

•Diffusion weighting will show a characteristic moderate

intensity (restriction of diffusion)

LEFT PCA EPIDERMOID CYST: well delineated lesion, which involves the left prepontine cistern and CPA, with slight mass effect on the left pons, and engulfing of the cranial nerves V to VIII on the left side, in the cisternal segment. The lesion has a fluid-type signal, slightly heterogenous, but with important water diffusion restriction.

Right epidermoid cyst.

Left epidermoid cyst.

Large left epidermoid cyst.

C. Lipomatous Masses:

Lipoma

Anomalously developed masses that arise from abnormal

differentiation of the meninx

Primitive Signal intensity similar to that of fat on all sequences -> high

signal on T1-weighted images;

would be of intermediate signal on T2-weighted images, similar to

subcutaneous and marrow fat; and

would not be visible, "disappear," on fat-saturated sequences

Nonenhancing (thick peripheral capsule that may enhance

Dermoid cyst

Midline lesions that rarely invade the CPA laterally, contain elements

from all layers of the skin FLAIR, CISS and DWI

certify diagnostic MR appearance depends on the amount of fat

present, although generally they are of increased signal

on both T1-and T2-weighted images Cholesterol granuloma

Results from the chronic obstruction of air cells and accumulation of secretions Expansile lytic lesions of the temporal bone Central region of high signal intensity and a peripheral hypointense rim on both T1-and T2-weighted images Nonenhancing

Left CP angle lipoma.

Lipoma at the CP angle.

Right lipoma at the CP angle. Left lipoma at the CP angle.

Cholesterol granuloma with right trigeminal neuralgia.

Cholesterol granuloma.

D. Flow void masses: Vascular loop syndrome

Affected nerves may by V (at root entry zone) or VII (at root exit zone) Vessel may by atherosclerotic -serpiginous, irregular MR Angiography -source images are most helpful Vertebrobasilar dolichoectasia may be one of the causes (atherosclerotic finding especially in the elderly) Venous anomaly Various developmental anomalies, which may involve the CPA as a drainage route, but rarely with clinical impact 2D and 3D Time of Flight sequences are useful for evaluating the vascular axes Contrast administration shows more detail VB, PICA, AICA aneurysms Non-neoplastic lesions, but with mass effect Thrombosis associates hyperintensity in T1 (methemoglobin); possible enhancement of the thrombus Pulsation artifacts may also be present in cases of aneurysm. Secondary involvement: Glomus tumor Sphenoid meningioma Lymphoma Ependymoma Choroid plexus papilloma

NEURO-VASCULAR CONFLICT: megadolico-vertebral and basilar arteries, with significant mass defect on the pons, which appears displaced medially and to the posterior. Note the segmentary contact with the left-side VII and VIII cranial nerves, in the cisternal segment, with their slight displacement to the posterior.

PICA aneurysm.

Aneurysm with hypoglossal palsy.

CAVERNOMA and VENOUS DEVELOPMENT ANOMALY of the left middle cerebellar peduncle. Left cerebellar venous development anomaly made of a series of small venules with deep topography which converge to a venous collector, in the immediate vicinity of the described cavernoma, which then crosses the left CPA cistern to connect through a left temporal cortical vein to the left transverse sinus.

CP Angle AV malformation.

AGGRESSIVE PARAGANGLIOMA (*) with invasion of the right CPA.

Paraganglioma with right facial nerve palsy, vertigo, and tinnitus.

Chondrosarcoma with intracranial hypertension.

Melanoma with a left cerebellar syndrome.

Metastases with lung cancer and right-sided hypoacusia, vertigo, and ear pain.

Endolymphatic sac tumor man with von Hippel-Lindau disease and vertigo.

Apex porosities with Gradenigo syndrome at clinical evaluation.

Choroid plexus papilloma with vertigo and intracranial hypertension.

Lymphoma with acquired immunodeficiency syndrome, vertigo, and headaches

Hemangioblastoma with von Hippel-Lindau disease and vertigo.

Ependymoma with vertigo, headaches, and left facial nerve palsy.

Dysembryoplastic neuroepithelial tumor with mild, long-lasting headaches

Atypical teratoid–rhabdoid tumor of cerebellopontine angle region.

Meningeal hemangiopericytoma of cerebellopontine angle.

Two cases of multiple hemangioblastomas.

Intra-ventricular ependymoma with extension to the CP angle.

Right side brain stem glioma with right CP angle extension.

Thank You.