Neuro Radiology - Schwannoma

Dr.Roopchand PSSenior resident Neurology

Introduction:

• WHO grade I tumours.• Peaks in the 4th or 5th decade of life.• Adolescent age – NF2• Mostly occur in 8th nerve• Other CN can be involved.• 30% of Intra spinal tumours.• 7-8% of all primary intracranial tumours and

75-90% of cerebellopontine angle masses.

• Bilateral vestibular schwannomas are highly suggestive of neurofibromatosis type 2 (NF2).

Clinical presentation• sensorineural hearing loss or tinnitus.• Facial Palsy• Cerebellar symptoms• Pressure effect, hydrocephalus.

Pathology:• Arise from the intracanalicular segment of the

vestibular portion of the vestibulocochlear nerve – Near the transition point between glial and

Schwann cells (Obersteiner-Redlich zone) .• In over 90% of cases these tumours arise from

the inferior division of the vestibular nerve . • They are well circumscribed encapsulated masses .• Bony erosion of internal auditory meatus can occur.• Usually never invades in to adjacent structures.

• They can display two types of growth pattern:• Antoni A– elongated cells with cytoplasmic processes arranged in

fascicles – little stromal matrix– Verocay bodies : nuclear free zones of processes lying

between regions of nuclear palisading• Antoni B– loose meshwork of cells– less densely cellular– microcysts and myxoid change

Radiographic features:

• Most vestibular schwannomas have an intracanalicular component.

• Widening of the porus acousticus resulting in the trumpeted IAM sign.– present in up to 90% of cases .– Helps in differentiating it from meningoma.

• Extracanalicular extension into cerebellopontine angle can lead to "ice cream cone" appearnace

• Tumours tend to be solid.• Cystic degeneration seen commonly in larger

tumours.• Haemorrhagic areas may also be seen.• Calcification is typically not present

CT:

• Erosion and widening of the internal acoustic meatus.

• Variable density.• Hard to identify due to adjacent bone artefact.• Contrast enhancing.– Variable

Normal SideTrumpeted IAM

ContrastPlain

MRI:• T1– slightly hypo-intense c.f. adjacent brain - 63%– iso intense c.f adjacent brain - 37%– may contain hypo intense cystic areas

• T2– heterogeneously hyper intense c.f to adjacent brain – cystic areas fluid intensity– may have associated peri-tumoural arachnoid cysts

• T1 C+ (Gd)– contrast enhancement is vivid– but heterogeneous in larger tumours

T1+CT1

Differentials:• meningioma

– more homogeneous in appearance . – meningiomas tend to have a broad dural base– usually lack trumpet IAM sign– calcification more common

• epidermoid– no enhancing component– very high signal on DWI– does not widen the IAM

• metastasis– uncommon– usually does not remodel the IAM as metastases are usually present for only

a short time• ependymoma

– centered on the fourth ventricle– does not extend into the IAM– usually younger patients

Spinal Schwanoma:

• Spinal schwannomas usually arise from the dorsal sensory roots.

• Radicular pain.• Myelopathy if large.• NF2 association seen.

Radiographic features:

• Appear as rounded lesions.• Often with associated adjacent bony

remodelling.• Large tumors– Either align themselves with the long axis of the

cord forming sausage shaped masses– Can extend over several levels– May protrude out of the neural exit foramen

forming a dumb-bell shaped mass.

MRI:

• Neuromas and schwannomas looks identical• Haemorrhage, intrinsic vascular changes

(thrombosis; sinusoidal dilatation), cyst formation and fatty degeneration – Schwannoma.

• T1 - 75% are isointense, 25% are hypointense• T2 - more than 95% are hyperintense, often

with mixed signal • T1 C+ (Gd) - virtually 100% enhance

T2

T2T1

T1C FatSatT2

Differentials:

• neurofibroma• meningioma• paraganglioma• myxopapillary ependymoma• intradural extra medullary metastases

Thank You