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eEdE – 151
A Case Series Illustrating the CT and MRI
Imaging Features of Sinonasal
Schwannoma
M Robinson, S Slasky, O Tairu
Email: [email protected]
Rutgers - New Jersey Medical School
Newark, NJ
Rutgers, The State University of New Jersey
Learning Objectives
The goals of this electronic educational exhibit are to:
• Review the incidence and clinical features of schwannoma
presenting in the sinonasal area
• Review the imaging findings for sinonasal schwannoma
• Identify distinguishing features between this entity and similar
neoplasms
Disclosure:
Dr. Tairu, Dr. Slasky, and Mr. Robinson have no relevant financial or nonfinancial relationships to disclose.
Schwannomas
Also called: neurilemmoma, neuroma
• Slow-growing, typically benign tumors of the Schwann cells of peripheral
nerve sheaths
• About 45% occur in the head and neck, most commonly in CN VIII,
usually referred to as vestibular schwannomas
• Associated with neurofibromatosis type 2, particularly those affecting CN
VIII
• Incidence is largely irrespective of sex or gender and excluding cases
associated with NF2, the average age at diagnosis is between 20 and 50
years old
Schwannomas in the sinonasal region
• About 4% of all schwannomas
Schwannomas in the sinonasal region
•
Commonly arise from the
lateral wall of the nasal cavity
and the ethmoid sinuses
– Origin from septum is rare
• Slow-growing, bone is
remodeled as opposed to
destroyed
– Commonly spread further into
ethmoid and sphenoid sinuses,
and only rarely intracranially
Common presenting symptoms
• Our patients presented with:
–Persistent unilateral nasal congestion
–Headaches
–Dizziness
–Hyposmia
–Hypogeusia
• Recurrent epistaxis is another common presenting symptom
• Occasionally patients are asymptomatic; incidental finding on
head imaging
Common structures of origin
● V1 and branches
○ Anterior/posterior ethmoidal nerves--enter lateral to crista galli, provide sensation
to the superior parts of the septum and lateral nasal wall, ethmoid air cells, and
sphenoid sinus
● V2 and branches
○ Posterior superior nasal nerve--passes through the pterygopalatine ganglion,
provides sensation superior and middle conchae as well as the middle aspect of
the septum
○ Greater and lesser palatine nerves--also from pterygopalatine ganglion, provide
sensation to the inferior nasal conchae and the inferior nasal septum
● Sympathetic fibers of the superior cervical ganglion
○ Innervate blood vessels throughout the sinonasal area
Common structures of origin
• Does not usually arise from olfactory nerve
– Olfactory nerve has olfactory ensheathing glia, similar to but distinct from
Schwann cells
• Tumors of the olfactory ensheathing glia have been reported in
the literature
– Differentiated histochemically by Leu7 stain
• Olfactory ensheathing glia are negative, Schwann cells are typically positive
• According to Murakami et al., the fila olfactoria acquires a
Schwann cell sheath about 0.5 mm after the olfactory bulb
which could serve as the origin for an olfactory schwannoma
General imaging features:
• The largest case series,12 cases of sinonasal schwannomas,
by Kim et al, assessed multiple features of these lesions, some
of which served as the basis for the analysis of our cases
– Lesion location: They concluded, in congruence with other published case
reports, that these lesions occurred mostly in the nasal cavity or within the
ethmoid air cells
– Lesion configuration: They concluded that lesions arising from the septum
have a rounder configuration while lesion within the sinus and nasal cavity
having a more tubular configuration (conforming to their space of origin)
General imaging features:
• Imaging characteristics on CT
– On CT, these lesions were largely isointense to muscle and demonstrated
only minimal appreciable enhancement
– Whereas on MRI, the lesions were isointense to the brainstem both on the
T1 and T2 weighted sequences (reflecting their relative hypercellularity)
and demonstrated avid contrast enhancement
Radiologic characteristics: CT
• Iso- to slightly hypoattenuating
to muscle on noncontrast
imaging
• Mildly enhances with contrast
• Visible bone remodeling rather
than destruction of adjacent
osseous structures (usually of
cribriform plate, orbital walls,
walls of sinuses, etc.)
Non-contrast CT demonstrating an oval lesion, isoattenuating to muscle, in
the posterior nasal cavity, with remodeling of the adjacent sinus walls
Radiologic characteristics: MRI, T1
• Isointense to muscle
• Enhance uniformly
• Note: larger masses may have
cystic areas
Radiologic characteristics: MRI, T2
• Hyperintense to
muscle on T2 with a
possible hypointense
capsule
Differential diagnoses
Other common masses that can occur in these area include:
• Non-neoplastic
– Allergic or inflammatory polyp
• Malignant neoplastic
–
–
–
–
–
Squamous cell carcinoma
Esthesioneuroblastoma
Melanoma
Sarcoma
Lymphoma
• Benign neoplastic
–
–
–
–
Squamous papilloma
Inverted papilloma
Fibrous dysplasia
Angiofibroma
Versus Esthesioneuroblastoma
• Schwannoma
– Origin typically ethmoid air cells or lateral
wall of nasal cavity
– Note also the tubular configuration
– Note the homogeneous contrast
enhancement
• Esthesioneuroblastoma
– Origin superomedial to middle turbinate,
typically from septum
Versus Esthesioneuroblastoma
• Schwannoma
– On CT: Bone remodeling
• Esthesioneuroblastoma
– On CT: Bone destruction
Versus Esthesioneuroblastoma
• Schwannoma
– On T1: iso-hypointense, homogeneous,
uniformly enhancing
• Esthesioneuroblastoma
– On T1: Isointense, heterogeneous,
variably enhances
Versus Esthesioneuroblastoma
• Schwannoma
– On T2: Hyperintense, relatively
homogeneous, possible hypointense
capsule
• Esthesioneuroblastoma
– On T2: Isointense, heterogeneous, no
capsule
– Classically have peritumoral cysts (not
shown)
Case 1
62 year old woman hospitalized for pneumonia and UTI, imaging
performed due to new-onset headaches and dizziness demonstrated:
Case 1
Case 1
• Findings:
– Well marginated lesion centered in the superior nasal cavity along the
superior aspect of the nasal septum with remodeling of the adjacent sinus
walls
– Hypoattenuating to muscle on noncontrast CT
– Homogenously hypointense to muscle and brainstem on T1
– Homogenously hyperintense to muscle and brainstem on T2 with a T2
hypointense rim, possibly representing a capsule
– Homogenous avid contrast enhancement on postcontrast T1 images.
– Intracranial extension through the fovea ethmodalis and cribriform plate
without evidence of brain invasion
Case 1
• Preoperative diagnosis: Anterior skull base mass with concern
for dural involvement
• Dura was partially resected, but pathology showed that there
was no invasion
• Histologically confirmed to be a schwannoma
Case 2
32 year old male presents with chronic left nasal obstruction. Imaging shows the following mass:
Case 2
Case 2
• Findings
– Well marginated lesion centered in the left nasal cavity, with a tubular
configuration, inseparable from the superior and middle turbinates and
involving the anterior ethmoid air cells with associated remodeling of the
medial wall of the maxillary sinus, lamina papyracea and nasal septum
– Hypoattenuating to muscle on CT
– Homogenously hypointense to muscle and brainstem on T1
– Homogenously hyperintense to muscle and brainstem on T2
– Homogenous avid contrast enhancement on postcontrast T1 images
– Intracranial extension through the fovea ethmodalis and cribriform plate
without evidence of brain invasion
– Obstructive opacification of the sphenoid sinus
Case 2
• Preoperative diagnosis: anterior skull base mass, underwent
endoscopic resection
• Biopsy taken and determined to be schwannoma
• Gross total resection with clean margins
Case 3
62 year old male with history of renal cell carcinoma with surveillance MRI
showing:
Case 3
Case 3
• Findings
– Large heterogeneous expansile mass centered in the central and left
anterosuperior nasal cavity and ethmoid air cells with remodeling of the
left lamina
– Heteregenous mass on CT with areas of increased attenuation
concerning for hemorrhage and/or calcifications
– Heterogenously hypointense mass on T1 with foci of precontrast T1
shortening concerning for mineralization and/or hemorrhage
– Heterogenous avid enhancement on postcontrast T1 images
– Intracranial extension into the anterior cranial fossa through the cribriform
plate and fovea ethmodalis without definite evidence of parenchymal
invasion
Case 3
•
Preoperative diagnosis: Anterior skull base mass, possibly malignant
•
Underwent endoscopic resection
•
Mass eroded through the superoposterior septum, the floor of the frontal sinus, cribriform
plate, and partially through the lamina papyracea
•
Abutted but did not invade the dura
•
Biopsies were taken and shown to be schwannoma, however, they also showed that the
mass was destroying bone, which is fairly unusual for this sort of tumor
•
Compared to the prior two cases, the mass in this case was larger and much more
heterogeneous in appearance
Summary of findings:
• Cases were typical in terms of presentation and location
• Lesion along the septum had a more oval shape, while the
lesion within the nasal cavity had a more tubular configuration
• Relatively homogenous appearance on CT and MR except for
the larger lesion which appeared more heterogenous
• Avid contrast enhancement which was homogenous with the
smaller lesions and heterogenous with the larger lesion
• Hypointensity around the lesions suggest a capsule, however,
this could also be related to the remodeled adjacent structures
• All three lesions demonstrated intracranial extension without
brain invasion, a finding described in several other case series
Treatment
• Management is typically operative
– If confined to nasal cavity, can usually be resected endoscopically
• Nerve of origin is often small, and not evident surgically
• Diagnosis can be confirmed histologically
– Stain strongly for S100, a marker of neural crest cells
– Commonly feature Verocay (Antoni A) bodies, or stacked rows of
palisading nuclei
Prognosis
• Recurrence is uncommon
– In a review of 16 cases presented by Forer et al., recurrence was only
noted in 2 cases after a follow-up period of 8 years
• Complications from endoscopic excision are rare
– May include permanent deficits of a trigeminal branch, if the branch must
be sacrificed
– Additionally, resection of intracranially invading masses may result in
leakage of CSF, which can be repaired intraoperatively
Conclusion
• Schwannomas of the sinonasal cavity are an uncommon entity
occurring in a broad range of patient demographics
• Although there are a several imaging features that are typical
and suggestive of this entity, many other sinonasal tumors
could have similar imaging appearances
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