Schwannomas are WHO grade I tumors that most commonly occur in the vestibular nerve. They present with sensorineural hearing loss, tinnitus, facial palsy or cerebellar symptoms. On imaging, they appear as well-circumscribed masses that widen the internal auditory meatus on CT and show heterogeneous enhancement on MRI. Spinal schwannomas usually arise from dorsal sensory roots and present with radicular pain or myelopathy.

1. Neuro Radiology - Schwannoma
Dr.Roopchand PS
Senior resident Neurology

2. 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.

3. • 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.

4. 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.

5. • 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

6. 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

7. • Tumours tend to be solid.
• Cystic degeneration seen commonly in larger
tumours.
• Haemorrhagic areas may also be seen.
• Calcification is typically not present

8. CT:
• Erosion and widening of the internal acoustic
meatus.
• Variable density.
• Hard to identify due to adjacent bone artefact.
• Contrast enhancing.
– Variable

9. Trumpeted IAM Normal Side

10. Contrast
Plain

11. 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

12. T1+C
T1

14. 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

15. Spinal Schwanoma:
• Spinal schwannomas usually arise from the
dorsal sensory roots.
• Radicular pain.
• Myelopathy if large.
• NF2 association seen.

16. 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.

17. 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

18. T2

19. T1 T2

20. T1C FatSat
T2

22. Differentials:
• neurofibroma
• meningioma
• paraganglioma
• myxopapillary ependymoma
• intradural extra medullary metastases