Vestibular schwannoma arises on the eighth cranial nerve.
usually unilateral, but in 9% of cases is bilateral
hearing loss and tinnitus are early symptoms produced by involvement of the cochlear division of the nerve
In the later stages vertigo with abnormal caloric and electronystagmographic responses develop from damage to the vestibular division itself.
CT Scan in Schwanoma
Plain CT, most schwannomas are isodense with brain parenchyma.
Calcification or areas of hemorrhage are rare.
On contrast-enhanced CT, the enhancement pattern typically is homogeneous
On contrast-enhanced CT, the enhancement pattern typically is homogeneous.
Bone window images can demonstrate remodeling of the adjacent skull base, such as expansion of the IAC by vestibular schwannomas and the facial canal by facial schwannomas
Expansion of the jugular foramen by CN IX, CN X, or CN XI schwannomas also can be seen.
Thin-collimation CT imaging of the skull base can be helpful for evaluating bone destruction, which is useful for differentiating jugular foramen schwannomas from paragangliomas
MRI in Schwannomas
isointense or slightly hypointense to gray matter on T1-weighted images and slightly hypointense to CSF
on T2-weighted images.
Enhancement following gadolinium administration typically is homogeneous, although larger schwannomas can show areas of cystic degeneration and signal heterogeneity,
often on the bases of increased areas of Antoni type B histology.
high-resolution thin-section heavily T2-weighted 3-dimensional sequences, individual nerves within the cistern and IAC can be visualized as linear filling defects within the bright CSF
Small masses can be identified without the use of an intravenous contrast agent
Typically, the masses are located in the cerebellopontine angle (CPA) and are centered at the porus, with extension into the IAC. Their appearance has been termed comet tail or ice cream cone
The long axis of the tumors lies parallel to the petrous surface. Occasionally, tumors can be entirely intracanicular, in which case, the primary differential diagnosis is a meningioma of the CPA
Unlike vestibular schwannomas, meningiomas tend to form obtuse angles with the adjacent petrous bone, typically are hemispherical in appearance, and often extend into the middle fossa via herniation
Contrast-enhanced T1-weighted image at the level of the internal auditory canal shows a densely enhancing cisternal vestibular schwannoma (white arrow) compressing the adjacent pons and cerebellum and distorting the fourth ventricle.
Contrast-enhanced T1-weighted axial image through the internal auditory canal shows a heterogeneously enhancing intracanalicular/cisternal vestibular schwannoma (white arrow). Anterior to the schwannoma a tumor-related cyst is noted (black arrow).
Intracanalicular vestibular schwannoma. Axial CISS (constructive interference in the steady state) image shows a 3-mm mass in the internal auditory canal as a filling defect within the bright cerebrospinal fluid.
Vestibular schwannoma. Axial contrast-enhanced T1-weighted image confirms the intracanalicular mass seen in Image 3. .
68 year old male with left sided hearing loss
44-year-old male with progressive right-sided sensorineural hearing loss
Female, 55 years, complaining of a right hearing loss and facial hemispasm Copyright, CID, 26.04.99 (1) Enhancing small tumor at the right cerebellopontine angle (2) Tumoral component inside the right internal acoustic meatus (3) Membranous labyrinth (4) Pons (5) Cerebellar hemisphere (6) Normal left internal acoustic meatus
Facial nerve: Schwannomas
can occur along any segment but frequently involve the geniculate ganglion and extend proximally or distally from there.
MRI and CT imaging characteristics are similar to those for vestibular schwannomas.
The location of the mass results in variable growth patterns.
In the IAC, facial schwannomas are indistinguishable from vestibular lesions.
When crossing the petrous bone to involve both the middle and posterior fossa, facial schwannomas cross in the mid portion of the petrous bone as opposed to trigeminal schwannomas, which cross near the petrous apex.
Lesions in the geniculate ganglion can be mistaken for temporal lobe lesions, and imaging in the coronal plane is useful in evaluating the lesions
Facial schwannoma. Axial T1-weighted image at the level of the internal auditory canal shows a soft tissue mass along the course of the tympanic segment of the facial nerve.
Facial schwannoma. Coronal contrast-enhanced T1-weighted image shows the schwannoma involving the mastoid segment of cranial nerve VII.
Facial neuritis. Axial contrast-enhanced T1-weighted image shows swelling and enhancement of the labyrinthine, geniculate, and tympanic segments of cranial nerve VII.
Facial neuritis. Coronal contrast-enhanced T1-weighted image shows swelling and marked enhancement of the mastoid segment of cranial nerve VII.
Trigeminal schwannomas can arise in the Meckel cave or in the cistern along the course of the nerve.
Extension and expansion of the foramen rotundum or ovale is common, and the masses can have a bilobed appearance.
Tumors also can grow posteriorly to involve the posterior fossa or anteriorly into the cavernous sinus.
Trigeminal schwannomas tend to have a more cystic component than do other schwannomas
Trigeminal schwannoma. Coronal T2-weighted image shows a hyperintense mass in the right cavernous sinus.
Trigeminal schwannoma. Axial contrast-enhanced T1-weighted image at the level of the mid pons shows a densely enhancing mass involving the left cranial nerve V within the cistern (black arrow) and Meckel cave (white arrow).
Trigeminal schwannoma. Axial CISS (constructive interference in the steady state) image shows a mass in the region of the cisternal segment of the right cranial nerve V (white arrow). The left cranial nerve V (without tumor) also is visualized (white arrow).
Trigeminal schwannoma. Coronal contrast-enhanced T1-weighted image (same patient as Picture 12) shows the mass arising from the cisternal segment of the right cranial nerve V. The left cranial nerve V (without tumor) also is visualized (white arrow).
Glossopharyngeal, vagus, or accessory nerve schwannomas
Glossopharyngeal, vagus, or accessory nerve schwannomas are rare and are difficult to distinguish from each other.
The tumors are classified based on their growth patterns, with
type A lesions growing predominantly intracranially,
type B lesions growing predominantly at the jugular foramen, and
type C lesions growing predominantly extracranially.
CT and MRI characteristics are similar to those seen in other schwannomas. In contrast to the more common paraganglioma in this region, schwannomas expand but do not infiltrate the adjacent bone
Glossopharyngeal schwannoma. Axial contrast-enhanced T1-weighted image shows a large extraaxial mass compressing the brainstem (black arrows) and extending into the skull base (white arrows).
Glossopharyngeal schwannoma. Coronal contrast-enhanced T1-weighted image (same patient as Picture 17) shows a mass extending through the skull base via the jugular foramen.
Glossopharyngeal schwannoma. Digital subtraction angiogram from an ascending pharyngeal artery injection reveals a moderately hypervascular schwannoma, which is atypical for schwannomas (same patient as Pictures 17-19).
Hypoglossal schwannomas are similar in growth patterns and imaging characteristics to jugular foramen schwannomas.
When large enough, the tumors can erode the hypoglossal canal to such an extent that differentiation from jugular foramen schwannomas can be difficult.
Schwannomas of CN VI
Schwannomas of CN VI are rare.
They have been reported to occur in the prepontine cistern, with a heterogeneous appearance on CT and MRI imaging and extension into the adjacent cavernous sinus.
Similar to other schwannomas, meningioma is the primary differential diagnosis, and the presence of areas of cystic change (manifesting as high T2 signal) can sway the likelihood of a diagnosis to schwannoma over meningioma. CN IV schwannomas similarly are rare (see Image 17).
Cranial nerve IV schwannoma. Axial and coronal contrast-enhanced T1-weighted images demonstrate a small mass involving the cisternal segment of cranial nerve IV adjacent to the midbrain.
Oculomotor nerve Schwannomas
Schwannomas of the oculomotor nerve have been reported in the literature but are exceedingly rare.
The tumors can present as masses in the suprasellar cistern and can be difficult to distinguish from meningiomas in this region.
Notice the whirly swirly pattern and how the cell nuclei are closely bunched together... almost as if they're forming a fence (Verocay bodies). Schwannomas are benign spindle cell tumors that occur along the edges of peripheral nerves. They can usually be removed without damaging the nerve itself.
A high power view of the Schwannoma, emphasizing the slenderness of the spindle cells and their elongate nuclei.
Compare them with the much plumper spindle cells of the meningioma.
NF-1 and NF-2 chromosome 17 and 22
1) six or more café-au-lait spots,
2) two or more hemartomas of the iris (Lisch nodules),
3) two or more neurofibromas,
4) one or more plexiform neurofibromas,
5) axillary freckling,
6) one or more bone dysplasias,
7) psuedoarthrosis of a long bone,
8) optic glioma, or
9) a first-degree relative with the diagnosis of NF-1
Neurofibromatosis - Radiology
cerebellar, brain stem, and cerebral astrocytomas are seen with NF-1.
On MR T2 weighted images, patients may have high signal intensity foci in the peduncles or deep gray matter of the cerebellum, brain stem or basal ganglia
These features are believed to represent hamartomas, focal areas of gliosis, wallerian degeneration, neuronal migrational disorders, or possibly neoplasms.
9-year-old male with a history of headaches x two months and hyperreflexia. Multiple rounded foci of abnormally bright signal are seen in the lentiform nuclei bilaterally, the thalami bilaterally, mesencephalon, and dentate nuclei bilaterally (left greater than right), on FLAIR and T2 weighted images. No abnormal enhancement is seen.
37 year old man with a well established family history of neurofibromatosis type 2. Of 4 older siblings, all four had in the past been treated with surgery for bilateral acoustic neuromas and a variety of other CNS tumors
Coronal T1 weighted MRI with contrast demonstrating a falx meningioma
Neurofibromatosis 2 Axial MRI with contrast demonstrating a very large acoustic neuroma and two meningiomas of the posterior cranial fossa.
Neurofibromatosis 2 Coronal MRI demonstrating a falx meningioma, a meningioma of the tentorium and an acoustic neuroma on the right side.
Sagital contrast T1 MRI of the same patient demonstrating the extent of the tentorial meningioma
T1 axial, non contrast MRI demonstrating an optic nerve glioma.
Axial T1-weighted postcontrast image demonstrates bilateral internal auditory canal-enhancing masses diagnostic for neurofibromatosis type 2. No biopsy is necessary for the diagnosis. Notice the en-plaque meningioma anterior to the brainstem.
Axial postcontrast T1-weighted image demonstrates a large enhancing sellar meningioma surrounding both internal carotid arteries in this case of neurofibromatosis type 2 (NF-2) (black arrows). Enhancing tissue in the ethmoid air cells also represents meningioma, extending through the cribriform plate. Meningiomas in patients with NF-2 can be more aggressive and invasive than spontaneous meningiomas. Note the small round enhancing extra-axial mass posterior to the tectum (white arrows). While this could represent another meningioma, the shape and location suggest it is a trochlear schwannoma instead.
Sagittal T1-weighted postcontrast image in a patient with known neurofibromatosis 2 demonstrates two midline meningiomas (arrowheads), one over the convexity and one along the vein of Galen. The enhancing mass in the medulla (arrow) most likely is an ependymoma
III. Tumors of the coverings of the brain - Meningioma
Meningiomas are the most common non-glial primary tumor of the CNS. Meningiomas are also the most common extraaxial primary tumor of the CNS.
They represent 15-25% of all intracranial primary tumors. Most patients are in the 5th and 6th decades (40's - 50's).
The 2x-4x female predilection is most likely due to hormone receptors for progesterone and estrogen.
The tumor arises from the arachnoid cap cells and is usually a slowly growing intradural intracranial mass, with a broad base of attachment to the overlying dura.
Hyperostosis of the overlying skull occurs in 15-25% of cases and may be a "sympathetic reaction" - or - can indicate invasion of the skull.
Note that arachnoid villi are composed of an outer layer of thick dura invaginated by arachnoid membrane.
Meningiomas are composed of arachnoid cap cells (outer layer) but they arise from the dura.
Throughout the dura there are rests of arachnoid cap cells and this is most common in the dura of the superior sagittal sinus because of the arachnoid villi naturally invaginating the dura in this location (Pacchionian granules).
Because this phenomena is most common in this location this is the region where meningiomas are most common
Meningiomas are the 4H Plus tumor: H - hemispheric H - homogeneous H - homogeneously enhancing H - hyperdense (CT) H - hyperostosis H - hormonally reactive (progesterone/estrogen)
Meningioma - Gross
This is a meningioma that arose from an arachnoid villus in the superior sagittal sinus. Note that unlike a glial tumor, it does not infiltrate surrounding brain but rather pushes against it; this usually makes meningiomas easier to remove than gliomas
This patient is a 27-year-old female who presented from a referring hospital secondary to a mass seen on CT exam. She had been complaining of double vision and intermittent headache for five months
IV. Germ cell tumors
B. Others: embryonal carcinoma, choriocarcinoma, teratoma
These tumors arise from germ cells and are most common in the region of the pineal gland.
They are thought to arise from cells that should have migrated to the gonads during development.
They are highly infiltrative and rapidly growing
The tumor is composed of primitive germ cells distributed in a lobular array separated by a lymphocytic-rich stroma.
V. Other malformative tumors and tumor-like lesions
B. Rathke's cleft cyst
C. Epidermoid and Dermoid cyst
D. Colloid cyst of the third ventricle
A 45 year old male presented with history of severe headaches of 2 years duration.
CT scan was done and it showed a well defined, mildly hyperdense, non enhancing lesion in the Foramen of Monro, with obstructive hydrocephalus, this was reported as a colloid cyst.
Bilateral ventriculo-peritoneal shunts were introduced, and subsequent scan showed regression of the hydrocephalus.
A year later, patient developed a progressive loss of memory; an MRI scan of the brain was performed.
This photograph of a lateral X-ray of the skull shows the expansion of the sella turcica and calcification in mass (look between arrows).
A sagittal section of the brain shows a large craniopharyngioma below the cerebral ventricle. Note the stippled pattern of the tumor
This low power view of a section of craniopharyngioma shows a cystic area on the left, in the zones to the center, and lower right epithelia producing acellular substance, and a loose mesenchyme filling the rest of the field.
year-old who presented with headache, vomiting, visual defects, and polyuria. Head MRI: midline tumor mass and obstructive hydrocephalus.
51-year-old male with unspecified neurological symptoms four months status post head trauma Rathke's cleft cyst
Rathke's cleft cyst
Dermoid cyst: These are benign tumors that arise from epithelial cells misplaced during development. The cysts are smooth and encapsulated. Dermoid cysts occur most often in the posterior fossa
Colloid Cyst of Third Ventricle
Colloid Cyst of Third Ventricle
Female, 79 years, complaining of recent disorientation and memory loss.
On CT and MR images : small, round, non-enhancing, hyperdense, hypointense (T2), hyperintense (T1) tumour located in the anterior part of the third ventricle, near the Monro's foramina.
This lesion leads to obstruction of the Monro's foramina and therefore to lateral ventricles dilatation. We read this lesion as a typical colloid cyst.
VI. Tumors of the pituitary gland
HX: 71 y/o RHM developed a cataclysmic headache on 11/5/92 associated with a violent sneeze. The headache lasted 3-4 days. On 11/7/92, he had acute pain and loss of vision in the left eye. Over the following day his left pupil enlarged and his left upper eyelid began to droop. He was seen locally and a brain CT showed no sign of bleeding, but a tortuous left middle cerebral artery was visualized. The patient was transferred to UIHC 11/12/92.
HX: This 47 y/o RHM presented to his local optometrist in 9/92 for routine evaluation. He had no complaint of visual loss, HA, nausea/vomiting, lymphadenopathy, weight change, galactorrhea, impotence, temperature intolerance, hot or cold flashes, or personality change. Visual field testing revealed a superior bitemporal incongruous hemianopia and he was referred to NeuroOpthalmology at UIHC.
VII. Metastatic tumors to brain from elsewhere in the body
Note that there are at least five multiple foci of tumor which usually indicates metastases rather than primary tumor. In this case the metastatic nodules are also hemorrhagic and they arose from the lung
VII. Metastatic tumors to brain from elsewhere in the body
VII. Metastatic tumors to brain
VII. Metastatic tumors to brain Bronchogenic Carsinoma