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### Selected Images
![Sagittal T1 C+ MR shows a cystic mass with an enhancing nodule <img src='/img/arrows/WS.png'/>, consistent with hemangioblastoma, pushing the tonsils inferiorly through the foramen magnum <img src='/img/arrows/WO.png'/>. Note effaced 4th ventricle <img src='/img/arrows/WC.png'/>, enlarged foramen of Monro <img src='/img/arrows/CS.png'/>, and enlarged 3rd <img src='/img/arrows/CO.png'/> and lateral <img src='/img/arrows/CC.png'/> ventricles, consistent with obstructive hydrocephalus.](images/app.statdx.com_image_thumbnail_d93e03ab-ee6a-4de8-b332-8660df2448e1_annotated_true_size_900_quality_90_11e9ec7f.jpg)
![Sagittal T1 C+ MR shows a cystic mass with an enhancing nodule <img src='img/arrows/WS.png'/>, consistent with hemangioblastoma, pushing the tonsils inferiorly through the foramen magnum <img src='img/arrows/WO.png'/>. Note effaced 4th ventricle <img src='img/arrows/WC.png'/>, enlarged foramen of Monro <img src='img/arrows/CS.png'/>, and enlarged 3rd <img src='img/arrows/CO.png'/> and lateral <img src='img/arrows/CC.png'/> ventricles, consistent with obstructive hydrocephalus.](images/app.statdx.com_image_thumbnail_d93e03ab-ee6a-4de8-b332-8660df2448e1_annotated_true_size_900_quality_90_11e9ec7f.jpg)
**Herniation Syndromes, Intracranial**
*Sagittal T1 C+ MR shows a cystic mass with an enhancing nodule <img src='/img/arrows/WS.png'/>, consistent with hemangioblastoma, pushing the tonsils inferiorly through the foramen magnum <img src='/img/arrows/WO.png'/>. Note effaced 4th ventricle <img src='/img/arrows/WC.png'/>, enlarged foramen of Monro <img src='/img/arrows/CS.png'/>, and enlarged 3rd <img src='/img/arrows/CO.png'/> and lateral <img src='/img/arrows/CC.png'/> ventricles, consistent with obstructive hydrocephalus.*
*Sagittal T1 C+ MR shows a cystic mass with an enhancing nodule <img src='img/arrows/WS.png'/>, consistent with hemangioblastoma, pushing the tonsils inferiorly through the foramen magnum <img src='img/arrows/WO.png'/>. Note effaced 4th ventricle <img src='img/arrows/WC.png'/>, enlarged foramen of Monro <img src='img/arrows/CS.png'/>, and enlarged 3rd <img src='img/arrows/CO.png'/> and lateral <img src='img/arrows/CC.png'/> ventricles, consistent with obstructive hydrocephalus.*
![Sagittal T1 C+ MR shows a cystic mass with an enhancing nodule <img src='/img/arrows/WS.png'/>, consistent with hemangioblastoma, pushing the tonsils inferiorly through the foramen magnum <img src='/img/arrows/WO.png'/>. Note effaced 4th ventricle <img src='/img/arrows/WC.png'/>, enlarged foramen of Monro <img src='/img/arrows/CS.png'/>, and enlarged 3rd <img src='/img/arrows/CO.png'/> and lateral <img src='/img/arrows/CC.png'/> ventricles, consistent with obstructive hydrocephalus.](images/app.statdx.com_image_thumbnail_d93e03ab-ee6a-4de8-b332-8660df2448e1_size_174_quality_85_c6e99252.jpg)
![Sagittal T1 C+ MR shows a cystic mass with an enhancing nodule <img src='img/arrows/WS.png'/>, consistent with hemangioblastoma, pushing the tonsils inferiorly through the foramen magnum <img src='img/arrows/WO.png'/>. Note effaced 4th ventricle <img src='img/arrows/WC.png'/>, enlarged foramen of Monro <img src='img/arrows/CS.png'/>, and enlarged 3rd <img src='img/arrows/CO.png'/> and lateral <img src='img/arrows/CC.png'/> ventricles, consistent with obstructive hydrocephalus.](images/app.statdx.com_image_thumbnail_d93e03ab-ee6a-4de8-b332-8660df2448e1_size_174_quality_85_c6e99252.jpg)
**Herniation Syndromes, Intracranial**
*Sagittal T1 C+ MR shows a cystic mass with an enhancing nodule <img src='/img/arrows/WS.png'/>, consistent with hemangioblastoma, pushing the tonsils inferiorly through the foramen magnum <img src='/img/arrows/WO.png'/>. Note effaced 4th ventricle <img src='/img/arrows/WC.png'/>, enlarged foramen of Monro <img src='/img/arrows/CS.png'/>, and enlarged 3rd <img src='/img/arrows/CO.png'/> and lateral <img src='/img/arrows/CC.png'/> ventricles, consistent with obstructive hydrocephalus.*
*Sagittal T1 C+ MR shows a cystic mass with an enhancing nodule <img src='img/arrows/WS.png'/>, consistent with hemangioblastoma, pushing the tonsils inferiorly through the foramen magnum <img src='img/arrows/WO.png'/>. Note effaced 4th ventricle <img src='img/arrows/WC.png'/>, enlarged foramen of Monro <img src='img/arrows/CS.png'/>, and enlarged 3rd <img src='img/arrows/CO.png'/> and lateral <img src='img/arrows/CC.png'/> ventricles, consistent with obstructive hydrocephalus.*
![Sagittal T2 MR in a patient with occipital headaches shows a significantly pointed configuration of a low-lying cerebellar tonsil <img src='/img/arrows/WS.png'/> to the level of the midposterior ring of C2. Notice also the dorsally tilted dens <img src='/img/arrows/WO.png'/>, effacement of CSF at the foramen magnum, and associated cervicothoracic syrinx <img src='/img/arrows/WC.png'/>.](images/app.statdx.com_image_thumbnail_f32667fd-ebff-4c5c-bd14-80a9c76d4c17_annotated_true_size_900_quality_90_0d739782.jpg)
![Sagittal T2 MR in a patient with occipital headaches shows a significantly pointed configuration of a low-lying cerebellar tonsil <img src='img/arrows/WS.png'/> to the level of the midposterior ring of C2. Notice also the dorsally tilted dens <img src='img/arrows/WO.png'/>, effacement of CSF at the foramen magnum, and associated cervicothoracic syrinx <img src='img/arrows/WC.png'/>.](images/app.statdx.com_image_thumbnail_f32667fd-ebff-4c5c-bd14-80a9c76d4c17_annotated_true_size_900_quality_90_0d739782.jpg)
**Chiari 1**
*Sagittal T2 MR in a patient with occipital headaches shows a significantly pointed configuration of a low-lying cerebellar tonsil <img src='/img/arrows/WS.png'/> to the level of the midposterior ring of C2. Notice also the dorsally tilted dens <img src='/img/arrows/WO.png'/>, effacement of CSF at the foramen magnum, and associated cervicothoracic syrinx <img src='/img/arrows/WC.png'/>.*
*Sagittal T2 MR in a patient with occipital headaches shows a significantly pointed configuration of a low-lying cerebellar tonsil <img src='img/arrows/WS.png'/> to the level of the midposterior ring of C2. Notice also the dorsally tilted dens <img src='img/arrows/WO.png'/>, effacement of CSF at the foramen magnum, and associated cervicothoracic syrinx <img src='img/arrows/WC.png'/>.*
![Sagittal T2 MR shows a small posterior fossa with extension of the cerebellar peg <img src='/img/arrows/WS.png'/> through the foramen magnum to the level of C6. The cervicomedullary junction and 4th ventricle <img src='/img/arrows/WO.png'/> are low-lying and there is mild tectal beaking <img src='/img/arrows/WC.png'/> and moderate prominence of the massa intermedia <img src='/img/arrows/BS.png'/>.](images/app.statdx.com_image_thumbnail_3c1182ce-603f-414b-9ecd-728488f8ea13_annotated_true_size_900_quality_90_73ce0e43.jpg)
![Sagittal T2 MR shows a small posterior fossa with extension of the cerebellar peg <img src='img/arrows/WS.png'/> through the foramen magnum to the level of C6. The cervicomedullary junction and 4th ventricle <img src='img/arrows/WO.png'/> are low-lying and there is mild tectal beaking <img src='img/arrows/WC.png'/> and moderate prominence of the massa intermedia <img src='img/arrows/BS.png'/>.](images/app.statdx.com_image_thumbnail_3c1182ce-603f-414b-9ecd-728488f8ea13_annotated_true_size_900_quality_90_73ce0e43.jpg)
**Chiari 2**
*Sagittal T2 MR shows a small posterior fossa with extension of the cerebellar peg <img src='/img/arrows/WS.png'/> through the foramen magnum to the level of C6. The cervicomedullary junction and 4th ventricle <img src='/img/arrows/WO.png'/> are low-lying and there is mild tectal beaking <img src='/img/arrows/WC.png'/> and moderate prominence of the massa intermedia <img src='/img/arrows/BS.png'/>.*
*Sagittal T2 MR shows a small posterior fossa with extension of the cerebellar peg <img src='img/arrows/WS.png'/> through the foramen magnum to the level of C6. The cervicomedullary junction and 4th ventricle <img src='img/arrows/WO.png'/> are low-lying and there is mild tectal beaking <img src='img/arrows/WC.png'/> and moderate prominence of the massa intermedia <img src='img/arrows/BS.png'/>.*
![Sagittal T2 MR demonstrates a markedly enlarged posterior fossa with cystic dilatation of the 4th ventricle <img src='/img/arrows/WS.png'/>, upward rotation of severely hypoplastic vermis <img src='/img/arrows/WO.png'/>, markedly enlarged posterior fossa, and elevated torcula.](images/app.statdx.com_image_thumbnail_0c6467dd-b795-4546-9afd-1680b2372865_annotated_true_size_900_quality_90_45a0b4c2.jpg)
![Sagittal T2 MR demonstrates a markedly enlarged posterior fossa with cystic dilatation of the 4th ventricle <img src='img/arrows/WS.png'/>, upward rotation of severely hypoplastic vermis <img src='img/arrows/WO.png'/>, markedly enlarged posterior fossa, and elevated torcula.](images/app.statdx.com_image_thumbnail_0c6467dd-b795-4546-9afd-1680b2372865_annotated_true_size_900_quality_90_45a0b4c2.jpg)
**Dandy-Walker Continuum**
*Sagittal T2 MR demonstrates a markedly enlarged posterior fossa with cystic dilatation of the 4th ventricle <img src='/img/arrows/WS.png'/>, upward rotation of severely hypoplastic vermis <img src='/img/arrows/WO.png'/>, markedly enlarged posterior fossa, and elevated torcula.*
*Sagittal T2 MR demonstrates a markedly enlarged posterior fossa with cystic dilatation of the 4th ventricle <img src='img/arrows/WS.png'/>, upward rotation of severely hypoplastic vermis <img src='img/arrows/WO.png'/>, markedly enlarged posterior fossa, and elevated torcula.*
![Sagittal T1WI MR shows a CSF isointense arachnoid cyst <img src='/img/arrows/WO.png'/> filling the lower posterior fossa, effacing the cisterna magna, flattening the cervicomedullary junction <img src='/img/arrows/WS.png'/>, and extending caudally into the upper cervical canal.](images/app.statdx.com_image_thumbnail_9358bfe0-0e81-45e5-a915-382de4ca45a8_annotated_true_size_900_quality_90_5ee2bea0.jpg)
![Sagittal T1WI MR shows a CSF isointense arachnoid cyst <img src='img/arrows/WO.png'/> filling the lower posterior fossa, effacing the cisterna magna, flattening the cervicomedullary junction <img src='img/arrows/WS.png'/>, and extending caudally into the upper cervical canal.](images/app.statdx.com_image_thumbnail_9358bfe0-0e81-45e5-a915-382de4ca45a8_annotated_true_size_900_quality_90_5ee2bea0.jpg)
**Arachnoid Cyst**
*Sagittal T1WI MR shows a CSF isointense arachnoid cyst <img src='/img/arrows/WO.png'/> filling the lower posterior fossa, effacing the cisterna magna, flattening the cervicomedullary junction <img src='/img/arrows/WS.png'/>, and extending caudally into the upper cervical canal.*
*Sagittal T1WI MR shows a CSF isointense arachnoid cyst <img src='img/arrows/WO.png'/> filling the lower posterior fossa, effacing the cisterna magna, flattening the cervicomedullary junction <img src='img/arrows/WS.png'/>, and extending caudally into the upper cervical canal.*
![Sagittal T1WI C+ MR shows enhancing tissue extruding through the foramen of Magendie, filling the cisterna magna <img src='/img/arrows/WS.png'/>. Resultant obstruction has caused enlargement of the cerebral aqueduct <img src='/img/arrows/WC.png'/> and dilated 3rd ventricle <img src='/img/arrows/WO.png'/>.](images/app.statdx.com_image_thumbnail_dcf88032-90a4-4cdc-837d-0db68076ba0d_annotated_true_size_900_quality_90_8996372c.jpg)
![Sagittal T1WI C+ MR shows enhancing tissue extruding through the foramen of Magendie, filling the cisterna magna <img src='img/arrows/WS.png'/>. Resultant obstruction has caused enlargement of the cerebral aqueduct <img src='img/arrows/WC.png'/> and dilated 3rd ventricle <img src='img/arrows/WO.png'/>.](images/app.statdx.com_image_thumbnail_dcf88032-90a4-4cdc-837d-0db68076ba0d_annotated_true_size_900_quality_90_8996372c.jpg)
**Ependymoma**
*Sagittal T1WI C+ MR shows enhancing tissue extruding through the foramen of Magendie, filling the cisterna magna <img src='/img/arrows/WS.png'/>. Resultant obstruction has caused enlargement of the cerebral aqueduct <img src='/img/arrows/WC.png'/> and dilated 3rd ventricle <img src='/img/arrows/WO.png'/>.*
*Sagittal T1WI C+ MR shows enhancing tissue extruding through the foramen of Magendie, filling the cisterna magna <img src='img/arrows/WS.png'/>. Resultant obstruction has caused enlargement of the cerebral aqueduct <img src='img/arrows/WC.png'/> and dilated 3rd ventricle <img src='img/arrows/WO.png'/>.*
![Sagittal T1WI MR demonstrates dural-based tumor <img src='/img/arrows/WS.png'/> with significant mass effect compressing and displacing the cerebellum. Note the trapped CSF clefts <img src='/img/arrows/WC.png'/>. The tumor encroaches on the cisterna magna.](images/app.statdx.com_image_thumbnail_552dcc86-9bc3-45d4-a79b-5f70d7aee358_annotated_true_size_900_quality_90_b1b07faa.jpg)
![Sagittal T1WI MR demonstrates dural-based tumor <img src='img/arrows/WS.png'/> with significant mass effect compressing and displacing the cerebellum. Note the trapped CSF clefts <img src='img/arrows/WC.png'/>. The tumor encroaches on the cisterna magna.](images/app.statdx.com_image_thumbnail_552dcc86-9bc3-45d4-a79b-5f70d7aee358_annotated_true_size_900_quality_90_b1b07faa.jpg)
**Meningioma**
*Sagittal T1WI MR demonstrates dural-based tumor <img src='/img/arrows/WS.png'/> with significant mass effect compressing and displacing the cerebellum. Note the trapped CSF clefts <img src='/img/arrows/WC.png'/>. The tumor encroaches on the cisterna magna.*
*Sagittal T1WI MR demonstrates dural-based tumor <img src='img/arrows/WS.png'/> with significant mass effect compressing and displacing the cerebellum. Note the trapped CSF clefts <img src='img/arrows/WC.png'/>. The tumor encroaches on the cisterna magna.*
![Axial T1WI C+ MR shows a typical case of primary CNS lymphoma with subependymal tumor spread. Note a posterior fossa mass near the foramen of Luschka <img src='/img/arrows/WS.png'/> as well as a 2nd dural-based mass <img src='/img/arrows/WO.png'/>.](images/app.statdx.com_image_thumbnail_78b4e7b9-3149-4afa-8312-4f8ac2681b52_annotated_true_size_900_quality_90_f84a81af.jpg)
![Axial T1WI C+ MR shows a typical case of primary CNS lymphoma with subependymal tumor spread. Note a posterior fossa mass near the foramen of Luschka <img src='img/arrows/WS.png'/> as well as a 2nd dural-based mass <img src='img/arrows/WO.png'/>.](images/app.statdx.com_image_thumbnail_78b4e7b9-3149-4afa-8312-4f8ac2681b52_annotated_true_size_900_quality_90_f84a81af.jpg)
**Metastasis**
*Axial T1WI C+ MR shows a typical case of primary CNS lymphoma with subependymal tumor spread. Note a posterior fossa mass near the foramen of Luschka <img src='/img/arrows/WS.png'/> as well as a 2nd dural-based mass <img src='/img/arrows/WO.png'/>.*
*Axial T1WI C+ MR shows a typical case of primary CNS lymphoma with subependymal tumor spread. Note a posterior fossa mass near the foramen of Luschka <img src='img/arrows/WS.png'/> as well as a 2nd dural-based mass <img src='img/arrows/WO.png'/>.*
![Sagittal T1WI C+ MR shows obliteration of the suprasellar cistern <img src='/img/arrows/WS.png'/>, sagging/fat midbrain with closed angle between the peduncles and the pons <img src='/img/arrows/WO.png'/>, dural enhancement <img src='/img/arrows/WC.png'/>, and tonsillar descent <img src='/img/arrows/BO.png'/> with effacement of the cisterna magna.](images/app.statdx.com_image_thumbnail_43f42495-6e64-47ac-8abd-7ca9ca2ff540_annotated_true_size_900_quality_90_a13877a5.jpg)
![Sagittal T1WI C+ MR shows obliteration of the suprasellar cistern <img src='img/arrows/WS.png'/>, sagging/fat midbrain with closed angle between the peduncles and the pons <img src='img/arrows/WO.png'/>, dural enhancement <img src='img/arrows/WC.png'/>, and tonsillar descent <img src='img/arrows/BO.png'/> with effacement of the cisterna magna.](images/app.statdx.com_image_thumbnail_43f42495-6e64-47ac-8abd-7ca9ca2ff540_annotated_true_size_900_quality_90_a13877a5.jpg)
**Intracranial Hypotension**
*Sagittal T1WI C+ MR shows obliteration of the suprasellar cistern <img src='/img/arrows/WS.png'/>, sagging/fat midbrain with closed angle between the peduncles and the pons <img src='/img/arrows/WO.png'/>, dural enhancement <img src='/img/arrows/WC.png'/>, and tonsillar descent <img src='/img/arrows/BO.png'/> with effacement of the cisterna magna.*
*Sagittal T1WI C+ MR shows obliteration of the suprasellar cistern <img src='img/arrows/WS.png'/>, sagging/fat midbrain with closed angle between the peduncles and the pons <img src='img/arrows/WO.png'/>, dural enhancement <img src='img/arrows/WC.png'/>, and tonsillar descent <img src='img/arrows/BO.png'/> with effacement of the cisterna magna.*
![Sagittal T1WI C+ MR in 40-year-old man shows an enhancing mass at the bottom of the 4th ventricle <img src='/img/arrows/WS.png'/> filling the cisterna magna.](images/app.statdx.com_image_thumbnail_7a028d65-ddd4-458e-9bb8-cd91406e17cc_annotated_true_size_900_quality_90_a4e2aff3.jpg)
![Sagittal T1WI C+ MR in 40-year-old man shows an enhancing mass at the bottom of the 4th ventricle <img src='img/arrows/WS.png'/> filling the cisterna magna.](images/app.statdx.com_image_thumbnail_7a028d65-ddd4-458e-9bb8-cd91406e17cc_annotated_true_size_900_quality_90_a4e2aff3.jpg)
**Subependymoma**
*Sagittal T1WI C+ MR in 40-year-old man shows an enhancing mass at the bottom of the 4th ventricle <img src='/img/arrows/WS.png'/> filling the cisterna magna.*
*Sagittal T1WI C+ MR in 40-year-old man shows an enhancing mass at the bottom of the 4th ventricle <img src='img/arrows/WS.png'/> filling the cisterna magna.*
![Sagittal T1WI MR shows a typical case of a large 4th ventricular epidermoid cyst <img src='/img/arrows/WS.png'/>, which follows CSF intensity but is often slightly brighter and mildly heterogeneous in signal.](images/app.statdx.com_image_thumbnail_ae931e3a-ee28-4c7d-854c-665d58b34439_annotated_true_size_900_quality_90_8f1340e9.jpg)
![Sagittal T1WI MR shows a typical case of a large 4th ventricular epidermoid cyst <img src='img/arrows/WS.png'/>, which follows CSF intensity but is often slightly brighter and mildly heterogeneous in signal.](images/app.statdx.com_image_thumbnail_ae931e3a-ee28-4c7d-854c-665d58b34439_annotated_true_size_900_quality_90_8f1340e9.jpg)
**Epidermoid Cyst**
*Sagittal T1WI MR shows a typical case of a large 4th ventricular epidermoid cyst <img src='/img/arrows/WS.png'/>, which follows CSF intensity but is often slightly brighter and mildly heterogeneous in signal.*
*Sagittal T1WI MR shows a typical case of a large 4th ventricular epidermoid cyst <img src='img/arrows/WS.png'/>, which follows CSF intensity but is often slightly brighter and mildly heterogeneous in signal.*
![Axial T2WI MR demonstrates a T2- hyperintense mass <img src='/img/arrows/WS.png'/> encroaching laterally upon the ventral CSF at the foramen magnum. There was evidence of rupture (not shown) causing recurrent meningitis.](images/app.statdx.com_image_thumbnail_fc461ab0-6909-4db8-b585-ee6b0495e584_annotated_true_size_900_quality_90_ab4bf44b.jpg)
![Axial T2WI MR demonstrates a T2- hyperintense mass <img src='img/arrows/WS.png'/> encroaching laterally upon the ventral CSF at the foramen magnum. There was evidence of rupture (not shown) causing recurrent meningitis.](images/app.statdx.com_image_thumbnail_fc461ab0-6909-4db8-b585-ee6b0495e584_annotated_true_size_900_quality_90_ab4bf44b.jpg)
**Dermoid Cyst**
*Axial T2WI MR demonstrates a T2- hyperintense mass <img src='/img/arrows/WS.png'/> encroaching laterally upon the ventral CSF at the foramen magnum. There was evidence of rupture (not shown) causing recurrent meningitis.*
*Axial T2WI MR demonstrates a T2- hyperintense mass <img src='img/arrows/WS.png'/> encroaching laterally upon the ventral CSF at the foramen magnum. There was evidence of rupture (not shown) causing recurrent meningitis.*
![Sagittal T1WI C+ MR shows an enhancing vermian mass protruding through the foramen magnum <img src='/img/arrows/WS.png'/>. An associated cyst <img src='/img/arrows/WO.png'/> is deforming the 4th ventricle <img src='/img/arrows/WC.png'/>.](images/app.statdx.com_image_thumbnail_b01e6fff-9cce-4843-8749-c18dfa0f8c59_annotated_true_size_900_quality_90_36cd9838.jpg)
![Sagittal T1WI C+ MR shows an enhancing vermian mass protruding through the foramen magnum <img src='img/arrows/WS.png'/>. An associated cyst <img src='img/arrows/WO.png'/> is deforming the 4th ventricle <img src='img/arrows/WC.png'/>.](images/app.statdx.com_image_thumbnail_b01e6fff-9cce-4843-8749-c18dfa0f8c59_annotated_true_size_900_quality_90_36cd9838.jpg)
**Hemangioblastoma**
*Sagittal T1WI C+ MR shows an enhancing vermian mass protruding through the foramen magnum <img src='/img/arrows/WS.png'/>. An associated cyst <img src='/img/arrows/WO.png'/> is deforming the 4th ventricle <img src='/img/arrows/WC.png'/>.*
*Sagittal T1WI C+ MR shows an enhancing vermian mass protruding through the foramen magnum <img src='img/arrows/WS.png'/>. An associated cyst <img src='img/arrows/WO.png'/> is deforming the 4th ventricle <img src='img/arrows/WC.png'/>.*
![Axial T1WI C+ MR shows a neurenteric cyst encroaching <img src='/img/arrows/BS.png'/> upon the prepontine cistern. Although most often these are located anteriorly, they may arise posteriorly at the cisterna magnum.](images/app.statdx.com_image_thumbnail_baa88901-5c32-4263-95c8-65e0655116f4_annotated_true_size_900_quality_90_4bc83322.jpg)
![Axial T1WI C+ MR shows a neurenteric cyst encroaching <img src='img/arrows/BS.png'/> upon the prepontine cistern. Although most often these are located anteriorly, they may arise posteriorly at the cisterna magnum.](images/app.statdx.com_image_thumbnail_baa88901-5c32-4263-95c8-65e0655116f4_annotated_true_size_900_quality_90_4bc83322.jpg)
**Neurenteric Cyst**
*Axial T1WI C+ MR shows a neurenteric cyst encroaching <img src='/img/arrows/BS.png'/> upon the prepontine cistern. Although most often these are located anteriorly, they may arise posteriorly at the cisterna magnum.*
*Axial T1WI C+ MR shows a neurenteric cyst encroaching <img src='img/arrows/BS.png'/> upon the prepontine cistern. Although most often these are located anteriorly, they may arise posteriorly at the cisterna magnum.*
### Additional Images
![Sagittal T1WI MR shows a small posterior fossa with extension of the cerebellar peg <img src='/img/arrows/WS.png'/> through the foramen magnum to the level of C3. The cervicomedullary junction and 4th ventricle <img src='/img/arrows/WO.png'/> are low-lying, and there is tectal beaking <img src='/img/arrows/WC.png'/>.](images/app.statdx.com_image_thumbnail_f0e743d3-48ed-4542-b207-11bb55f9d934_annotated_true_size_900_quality_90_a2144ce8.jpg)
![Sagittal T1WI MR shows a small posterior fossa with extension of the cerebellar peg <img src='img/arrows/WS.png'/> through the foramen magnum to the level of C3. The cervicomedullary junction and 4th ventricle <img src='img/arrows/WO.png'/> are low-lying, and there is tectal beaking <img src='img/arrows/WC.png'/>.](images/app.statdx.com_image_thumbnail_f0e743d3-48ed-4542-b207-11bb55f9d934_annotated_true_size_900_quality_90_a2144ce8.jpg)
**Chiari 2**
*Sagittal T1WI MR shows a small posterior fossa with extension of the cerebellar peg <img src='/img/arrows/WS.png'/> through the foramen magnum to the level of C3. The cervicomedullary junction and 4th ventricle <img src='/img/arrows/WO.png'/> are low-lying, and there is tectal beaking <img src='/img/arrows/WC.png'/>.*
*Sagittal T1WI MR shows a small posterior fossa with extension of the cerebellar peg <img src='img/arrows/WS.png'/> through the foramen magnum to the level of C3. The cervicomedullary junction and 4th ventricle <img src='img/arrows/WO.png'/> are low-lying, and there is tectal beaking <img src='img/arrows/WC.png'/>.*
![Sagittal T1WI MR demonstrates a markedly enlarged posterior fossa with cystic dilatation of the 4th ventricle <img src='/img/arrows/WO.png'/>, upwardly rotated hypoplastic vermis <img src='/img/arrows/WS.png'/>, and low-lying torcular Herophili <img src='/img/arrows/WC.png'/>.](images/app.statdx.com_image_thumbnail_597739b9-7ca6-42c3-9220-6e8459aded8e_annotated_true_size_900_quality_90_271d003d.jpg)
![Sagittal T1WI MR demonstrates a markedly enlarged posterior fossa with cystic dilatation of the 4th ventricle <img src='img/arrows/WO.png'/>, upwardly rotated hypoplastic vermis <img src='img/arrows/WS.png'/>, and low-lying torcular Herophili <img src='img/arrows/WC.png'/>.](images/app.statdx.com_image_thumbnail_597739b9-7ca6-42c3-9220-6e8459aded8e_annotated_true_size_900_quality_90_271d003d.jpg)
**Dandy-Walker Continuum**
*Sagittal T1WI MR demonstrates a markedly enlarged posterior fossa with cystic dilatation of the 4th ventricle <img src='/img/arrows/WO.png'/>, upwardly rotated hypoplastic vermis <img src='/img/arrows/WS.png'/>, and low-lying torcular Herophili <img src='/img/arrows/WC.png'/>.*
*Sagittal T1WI MR demonstrates a markedly enlarged posterior fossa with cystic dilatation of the 4th ventricle <img src='img/arrows/WO.png'/>, upwardly rotated hypoplastic vermis <img src='img/arrows/WS.png'/>, and low-lying torcular Herophili <img src='img/arrows/WC.png'/>.*
![Sagittal T2 MR in a patient with occipital headaches shows a significantly pointed configuration of a low-lying cerebellar tonsil <img src='/img/arrows/WS.png'/> to the level of the midposterior ring of C2. Notice also the dorsally tilted dens <img src='/img/arrows/WO.png'/> and effacement of CSF at the foramen magnum.](images/app.statdx.com_image_thumbnail_dac4c49b-c2b5-416f-a085-f7b7e6de8e51_annotated_true_size_900_quality_90_60d55480.jpg)
![Sagittal T2 MR in a patient with occipital headaches shows a significantly pointed configuration of a low-lying cerebellar tonsil <img src='img/arrows/WS.png'/> to the level of the midposterior ring of C2. Notice also the dorsally tilted dens <img src='img/arrows/WO.png'/> and effacement of CSF at the foramen magnum.](images/app.statdx.com_image_thumbnail_dac4c49b-c2b5-416f-a085-f7b7e6de8e51_annotated_true_size_900_quality_90_60d55480.jpg)
**Chiari 1**
*Sagittal T2 MR in a patient with occipital headaches shows a significantly pointed configuration of a low-lying cerebellar tonsil <img src='/img/arrows/WS.png'/> to the level of the midposterior ring of C2. Notice also the dorsally tilted dens <img src='/img/arrows/WO.png'/> and effacement of CSF at the foramen magnum.*
*Sagittal T2 MR in a patient with occipital headaches shows a significantly pointed configuration of a low-lying cerebellar tonsil <img src='img/arrows/WS.png'/> to the level of the midposterior ring of C2. Notice also the dorsally tilted dens <img src='img/arrows/WO.png'/> and effacement of CSF at the foramen magnum.*
![Sagittal T1WI MR shows inferior extension of the peg-like cerebellar tonsils <img src='/img/arrows/WS.png'/> well below the level of the foramen magnum <img src='/img/arrows/BO.png'/>, consistent with Chiari 1.](images/app.statdx.com_image_thumbnail_bf765af5-15a4-473e-8df5-a11a991e90bc_annotated_true_size_900_quality_90_1e09c50d.jpg)
![Sagittal T1WI MR shows inferior extension of the peg-like cerebellar tonsils <img src='img/arrows/WS.png'/> well below the level of the foramen magnum <img src='img/arrows/BO.png'/>, consistent with Chiari 1.](images/app.statdx.com_image_thumbnail_bf765af5-15a4-473e-8df5-a11a991e90bc_annotated_true_size_900_quality_90_1e09c50d.jpg)
**Chiari 1**
*Sagittal T1WI MR shows inferior extension of the peg-like cerebellar tonsils <img src='/img/arrows/WS.png'/> well below the level of the foramen magnum <img src='/img/arrows/BO.png'/>, consistent with Chiari 1.*
*Sagittal T1WI MR shows inferior extension of the peg-like cerebellar tonsils <img src='img/arrows/WS.png'/> well below the level of the foramen magnum <img src='img/arrows/BO.png'/>, consistent with Chiari 1.*
![Axial T2WI MR at the level of the foramen magnum demonstrates downward tonsillar herniation <img src='/img/arrows/WS.png'/> secondary to mass affect from brain death.](images/app.statdx.com_image_thumbnail_4ec0f703-c702-49e8-a1ed-adb06f9da9c5_annotated_true_size_900_quality_90_813870b0.jpg)
![Axial T2WI MR at the level of the foramen magnum demonstrates downward tonsillar herniation <img src='img/arrows/WS.png'/> secondary to mass affect from brain death.](images/app.statdx.com_image_thumbnail_4ec0f703-c702-49e8-a1ed-adb06f9da9c5_annotated_true_size_900_quality_90_813870b0.jpg)
**Herniation Syndromes, Intracranial**
*Axial T2WI MR at the level of the foramen magnum demonstrates downward tonsillar herniation <img src='/img/arrows/WS.png'/> secondary to mass affect from brain death.*
*Axial T2WI MR at the level of the foramen magnum demonstrates downward tonsillar herniation <img src='img/arrows/WS.png'/> secondary to mass affect from brain death.*
![Sagittal T1WI MR shows cerebellar tonsillar herniation <img src='/img/arrows/WC.png'/> from a large left posterior fossa mass. Note compression of 4th ventricle <img src='/img/arrows/WO.png'/>. Supratentorial ventricles are enlarged <img src='/img/arrows/WS.png'/>.](images/app.statdx.com_image_thumbnail_8aaa21ec-1c19-4e6c-8181-592b3df7869d_annotated_true_size_900_quality_90_60eba5bd.jpg)
![Sagittal T1WI MR shows cerebellar tonsillar herniation <img src='img/arrows/WC.png'/> from a large left posterior fossa mass. Note compression of 4th ventricle <img src='img/arrows/WO.png'/>. Supratentorial ventricles are enlarged <img src='img/arrows/WS.png'/>.](images/app.statdx.com_image_thumbnail_8aaa21ec-1c19-4e6c-8181-592b3df7869d_annotated_true_size_900_quality_90_60eba5bd.jpg)
**Herniation Syndromes, Intracranial**
*Sagittal T1WI MR shows cerebellar tonsillar herniation <img src='/img/arrows/WC.png'/> from a large left posterior fossa mass. Note compression of 4th ventricle <img src='/img/arrows/WO.png'/>. Supratentorial ventricles are enlarged <img src='/img/arrows/WS.png'/>.*
*Sagittal T1WI MR shows cerebellar tonsillar herniation <img src='img/arrows/WC.png'/> from a large left posterior fossa mass. Note compression of 4th ventricle <img src='img/arrows/WO.png'/>. Supratentorial ventricles are enlarged <img src='img/arrows/WS.png'/>.*
![Sagittal CINE phase-contrast CSF flow - diastolic shows diminished posterior CSF flow <img src='/img/arrows/WS.png'/> compared to anterior CSF flow <img src='/img/arrows/BO.png'/> at the site of tonsillar impaction.](images/app.statdx.com_image_thumbnail_bbdce702-8985-4ec6-a3e4-cad6dea34ada_annotated_true_size_900_quality_90_9fd2b7f0.jpg)
![Sagittal CINE phase-contrast CSF flow - diastolic shows diminished posterior CSF flow <img src='img/arrows/WS.png'/> compared to anterior CSF flow <img src='img/arrows/BO.png'/> at the site of tonsillar impaction.](images/app.statdx.com_image_thumbnail_bbdce702-8985-4ec6-a3e4-cad6dea34ada_annotated_true_size_900_quality_90_9fd2b7f0.jpg)
**Chiari 1**
*Sagittal CINE phase-contrast CSF flow - diastolic shows diminished posterior CSF flow <img src='/img/arrows/WS.png'/> compared to anterior CSF flow <img src='/img/arrows/BO.png'/> at the site of tonsillar impaction.*
*Sagittal CINE phase-contrast CSF flow - diastolic shows diminished posterior CSF flow <img src='img/arrows/WS.png'/> compared to anterior CSF flow <img src='img/arrows/BO.png'/> at the site of tonsillar impaction.*
![Sagittal T2WI MR shows a classic case of Chiari 1 with pointed cerebellar tonsils <img src='/img/arrows/WO.png'/> protruding through the foramen magnum and effacing the cisterna magna.](images/app.statdx.com_image_thumbnail_6840be04-8ddf-44dd-90f5-533d79cc1e88_annotated_true_size_900_quality_90_19b200f9.jpg)
![Sagittal T2WI MR shows a classic case of Chiari 1 with pointed cerebellar tonsils <img src='img/arrows/WO.png'/> protruding through the foramen magnum and effacing the cisterna magna.](images/app.statdx.com_image_thumbnail_6840be04-8ddf-44dd-90f5-533d79cc1e88_annotated_true_size_900_quality_90_19b200f9.jpg)
**Chiari 1**
*Sagittal T2WI MR shows a classic case of Chiari 1 with pointed cerebellar tonsils <img src='/img/arrows/WO.png'/> protruding through the foramen magnum and effacing the cisterna magna.*
*Sagittal T2WI MR shows a classic case of Chiari 1 with pointed cerebellar tonsils <img src='img/arrows/WO.png'/> protruding through the foramen magnum and effacing the cisterna magna.*
![Sagittal T2WI MR shows a small posterior fossa with caudal descent of cerebellar tonsillar tissue <img src='/img/arrows/WS.png'/>, elongation of the 4th ventricle <img src='/img/arrows/WC.png'/>, and cervical cord syrinx <img src='/img/arrows/WO.png'/>.](images/app.statdx.com_image_thumbnail_e8e875a9-dab9-4138-acad-70e88f4e90d9_annotated_true_size_900_quality_90_95de6bef.jpg)
![Sagittal T2WI MR shows a small posterior fossa with caudal descent of cerebellar tonsillar tissue <img src='img/arrows/WS.png'/>, elongation of the 4th ventricle <img src='img/arrows/WC.png'/>, and cervical cord syrinx <img src='img/arrows/WO.png'/>.](images/app.statdx.com_image_thumbnail_e8e875a9-dab9-4138-acad-70e88f4e90d9_annotated_true_size_900_quality_90_95de6bef.jpg)
**Chiari 2**
*Sagittal T2WI MR shows a small posterior fossa with caudal descent of cerebellar tonsillar tissue <img src='/img/arrows/WS.png'/>, elongation of the 4th ventricle <img src='/img/arrows/WC.png'/>, and cervical cord syrinx <img src='/img/arrows/WO.png'/>.*
*Sagittal T2WI MR shows a small posterior fossa with caudal descent of cerebellar tonsillar tissue <img src='img/arrows/WS.png'/>, elongation of the 4th ventricle <img src='img/arrows/WC.png'/>, and cervical cord syrinx <img src='img/arrows/WO.png'/>.*
![Axial FSPGR image demonstrates caudally displaced cerebellar tissue <img src='/img/arrows/WO.png'/> wrapping around the brainstem. This is sometimes referred to as a &quot;creeping cerebellum&quot; due to a small posterior fossa.](images/app.statdx.com_image_thumbnail_2881fed2-4a1d-4e08-8032-ccc2e2135a6c_annotated_true_size_900_quality_90_b9efe583.jpg)
![Axial FSPGR image demonstrates caudally displaced cerebellar tissue <img src='img/arrows/WO.png'/> wrapping around the brainstem. This is sometimes referred to as a &quot;creeping cerebellum&quot; due to a small posterior fossa.](images/app.statdx.com_image_thumbnail_2881fed2-4a1d-4e08-8032-ccc2e2135a6c_annotated_true_size_900_quality_90_b9efe583.jpg)
**Chiari 2**
*Axial FSPGR image demonstrates caudally displaced cerebellar tissue <img src='/img/arrows/WO.png'/> wrapping around the brainstem. This is sometimes referred to as a &quot;creeping cerebellum&quot; due to a small posterior fossa.*
*Axial FSPGR image demonstrates caudally displaced cerebellar tissue <img src='img/arrows/WO.png'/> wrapping around the brainstem. This is sometimes referred to as a &quot;creeping cerebellum&quot; due to a small posterior fossa.*
![Sagittal T1WI MR shows caudal descent of cerebellar vermian tissue <img src='/img/arrows/WS.png'/> and elongated 4th ventricle <img src='/img/arrows/WC.png'/> as well as callosal dysgenesis <img src='/img/arrows/WO.png'/> and a small posterior fossa.](images/app.statdx.com_image_thumbnail_5a4e9906-ab96-4d21-9cab-e237c76a221e_annotated_true_size_900_quality_90_77c3db2e.jpg)
![Sagittal T1WI MR shows caudal descent of cerebellar vermian tissue <img src='img/arrows/WS.png'/> and elongated 4th ventricle <img src='img/arrows/WC.png'/> as well as callosal dysgenesis <img src='img/arrows/WO.png'/> and a small posterior fossa.](images/app.statdx.com_image_thumbnail_5a4e9906-ab96-4d21-9cab-e237c76a221e_annotated_true_size_900_quality_90_77c3db2e.jpg)
**Chiari 2**
*Sagittal T1WI MR shows caudal descent of cerebellar vermian tissue <img src='/img/arrows/WS.png'/> and elongated 4th ventricle <img src='/img/arrows/WC.png'/> as well as callosal dysgenesis <img src='/img/arrows/WO.png'/> and a small posterior fossa.*
*Sagittal T1WI MR shows caudal descent of cerebellar vermian tissue <img src='img/arrows/WS.png'/> and elongated 4th ventricle <img src='img/arrows/WC.png'/> as well as callosal dysgenesis <img src='img/arrows/WO.png'/> and a small posterior fossa.*
![Sagittal T1 C+ MR shows a small posterior fossa with extension of the vermis through the foramen magnum to the level of C1/2 <img src='/img/arrows/WS.png'/>. The 4th ventricle is small <img src='/img/arrows/WO.png'/>, and there is tectal beaking <img src='/img/arrows/WC.png'/>.](images/app.statdx.com_image_thumbnail_fc43bc05-4fc8-45c2-8329-13bc355cf93c_annotated_true_size_900_quality_90_7e196aa3.jpg)
![Sagittal T1 C+ MR shows a small posterior fossa with extension of the vermis through the foramen magnum to the level of C1/2 <img src='img/arrows/WS.png'/>. The 4th ventricle is small <img src='img/arrows/WO.png'/>, and there is tectal beaking <img src='img/arrows/WC.png'/>.](images/app.statdx.com_image_thumbnail_fc43bc05-4fc8-45c2-8329-13bc355cf93c_annotated_true_size_900_quality_90_7e196aa3.jpg)
**Chiari 2**
*Sagittal T1 C+ MR shows a small posterior fossa with extension of the vermis through the foramen magnum to the level of C1/2 <img src='/img/arrows/WS.png'/>. The 4th ventricle is small <img src='/img/arrows/WO.png'/>, and there is tectal beaking <img src='/img/arrows/WC.png'/>.*
*Sagittal T1 C+ MR shows a small posterior fossa with extension of the vermis through the foramen magnum to the level of C1/2 <img src='img/arrows/WS.png'/>. The 4th ventricle is small <img src='img/arrows/WO.png'/>, and there is tectal beaking <img src='img/arrows/WC.png'/>.*
![Axial T2WI MR shows a normal 4th ventricle and vermis; however, there is a prominent retrocerebellar CSF space <img src='/img/arrows/WO.png'/>, which does not cause compression but does remodel endosteum, leading to mega cisterna magna.](images/app.statdx.com_image_thumbnail_c3afc83f-66c2-4438-9441-88dc439e4880_annotated_true_size_900_quality_90_bae05a32.jpg)
![Axial T2WI MR shows a normal 4th ventricle and vermis; however, there is a prominent retrocerebellar CSF space <img src='img/arrows/WO.png'/>, which does not cause compression but does remodel endosteum, leading to mega cisterna magna.](images/app.statdx.com_image_thumbnail_c3afc83f-66c2-4438-9441-88dc439e4880_annotated_true_size_900_quality_90_bae05a32.jpg)
**Dandy-Walker Continuum**
*Axial T2WI MR shows a normal 4th ventricle and vermis; however, there is a prominent retrocerebellar CSF space <img src='/img/arrows/WO.png'/>, which does not cause compression but does remodel endosteum, leading to mega cisterna magna.*
*Axial T2WI MR shows a normal 4th ventricle and vermis; however, there is a prominent retrocerebellar CSF space <img src='img/arrows/WO.png'/>, which does not cause compression but does remodel endosteum, leading to mega cisterna magna.*
![Sagittal T1WI MR demonstrates a CSF-intensity arachnoid cyst remodeling the endosteum <img src='/img/arrows/WS.png'/> and filling the cisterna magna <img src='/img/arrows/WO.png'/>.](images/app.statdx.com_image_thumbnail_91da2980-fb4a-4a4e-b638-7747bec7db0c_annotated_true_size_900_quality_90_eae82879.jpg)
![Sagittal T1WI MR demonstrates a CSF-intensity arachnoid cyst remodeling the endosteum <img src='img/arrows/WS.png'/> and filling the cisterna magna <img src='img/arrows/WO.png'/>.](images/app.statdx.com_image_thumbnail_91da2980-fb4a-4a4e-b638-7747bec7db0c_annotated_true_size_900_quality_90_eae82879.jpg)
**Arachnoid Cyst**
*Sagittal T1WI MR demonstrates a CSF-intensity arachnoid cyst remodeling the endosteum <img src='/img/arrows/WS.png'/> and filling the cisterna magna <img src='/img/arrows/WO.png'/>.*
*Sagittal T1WI MR demonstrates a CSF-intensity arachnoid cyst remodeling the endosteum <img src='img/arrows/WS.png'/> and filling the cisterna magna <img src='img/arrows/WO.png'/>.*
![Sagittal T2WI MR shows heterogeneous features of an ependymoma. Focal hyperintense regions correspond to focal necrosis <img src='/img/arrows/WS.png'/> and hypointense regions correlate to calcification <img src='/img/arrows/WC.png'/>.](images/app.statdx.com_image_thumbnail_f38e8e00-56df-4d69-b748-773ed89d905f_annotated_true_size_900_quality_90_69f8cdb4.jpg)
![Sagittal T2WI MR shows heterogeneous features of an ependymoma. Focal hyperintense regions correspond to focal necrosis <img src='img/arrows/WS.png'/> and hypointense regions correlate to calcification <img src='img/arrows/WC.png'/>.](images/app.statdx.com_image_thumbnail_f38e8e00-56df-4d69-b748-773ed89d905f_annotated_true_size_900_quality_90_69f8cdb4.jpg)
**Ependymoma**
*Sagittal T2WI MR shows heterogeneous features of an ependymoma. Focal hyperintense regions correspond to focal necrosis <img src='/img/arrows/WS.png'/> and hypointense regions correlate to calcification <img src='/img/arrows/WC.png'/>.*
*Sagittal T2WI MR shows heterogeneous features of an ependymoma. Focal hyperintense regions correspond to focal necrosis <img src='img/arrows/WS.png'/> and hypointense regions correlate to calcification <img src='img/arrows/WC.png'/>.*
![Axial T1 C+ MR demonstrates a heterogeneously enhancing ependymoma <img src='/img/arrows/BS.png'/> containing cystic elements <img src='/img/arrows/WO.png'/>.](images/app.statdx.com_image_thumbnail_8c0d32d7-f882-4d35-b39d-0cebc442af46_annotated_true_size_900_quality_90_21ba0570.jpg)
![Axial T1 C+ MR demonstrates a heterogeneously enhancing ependymoma <img src='img/arrows/BS.png'/> containing cystic elements <img src='img/arrows/WO.png'/>.](images/app.statdx.com_image_thumbnail_8c0d32d7-f882-4d35-b39d-0cebc442af46_annotated_true_size_900_quality_90_21ba0570.jpg)
**Ependymoma**
*Axial T1 C+ MR demonstrates a heterogeneously enhancing ependymoma <img src='/img/arrows/BS.png'/> containing cystic elements <img src='/img/arrows/WO.png'/>.*
*Axial T1 C+ MR demonstrates a heterogeneously enhancing ependymoma <img src='img/arrows/BS.png'/> containing cystic elements <img src='img/arrows/WO.png'/>.*
![Sagittal T1 C+ MR shows an enhancing mass expanding the 4th ventricle <img src='/img/arrows/WS.png'/>. The mass is also distending the obex <img src='/img/arrows/WO.png'/> and protruding through the foramen of Magendie into the cisterna magna <img src='/img/arrows/WC.png'/>.](images/app.statdx.com_image_thumbnail_5fc91f03-53aa-4f1a-b923-2461c8433360_annotated_true_size_900_quality_90_de5dd820.jpg)
![Sagittal T1 C+ MR shows an enhancing mass expanding the 4th ventricle <img src='img/arrows/WS.png'/>. The mass is also distending the obex <img src='img/arrows/WO.png'/> and protruding through the foramen of Magendie into the cisterna magna <img src='img/arrows/WC.png'/>.](images/app.statdx.com_image_thumbnail_5fc91f03-53aa-4f1a-b923-2461c8433360_annotated_true_size_900_quality_90_de5dd820.jpg)
**Ependymoma**
*Sagittal T1 C+ MR shows an enhancing mass expanding the 4th ventricle <img src='/img/arrows/WS.png'/>. The mass is also distending the obex <img src='/img/arrows/WO.png'/> and protruding through the foramen of Magendie into the cisterna magna <img src='/img/arrows/WC.png'/>.*
*Sagittal T1 C+ MR shows an enhancing mass expanding the 4th ventricle <img src='img/arrows/WS.png'/>. The mass is also distending the obex <img src='img/arrows/WO.png'/> and protruding through the foramen of Magendie into the cisterna magna <img src='img/arrows/WC.png'/>.*
![Axial T2WI MR demonstrates a posterior fossa meningioma <img src='/img/arrows/WS.png'/> with significant mass effect upon the cerebellum with interposed trapped CSF clefts <img src='/img/arrows/WO.png'/> and vessels <img src='/img/arrows/WC.png'/>.](images/app.statdx.com_image_thumbnail_d1c5e3a5-bf64-4a37-a40b-bb3a99f607ef_annotated_true_size_900_quality_90_329c2b60.jpg)
![Axial T2WI MR demonstrates a posterior fossa meningioma <img src='img/arrows/WS.png'/> with significant mass effect upon the cerebellum with interposed trapped CSF clefts <img src='img/arrows/WO.png'/> and vessels <img src='img/arrows/WC.png'/>.](images/app.statdx.com_image_thumbnail_d1c5e3a5-bf64-4a37-a40b-bb3a99f607ef_annotated_true_size_900_quality_90_329c2b60.jpg)
**Meningioma**
*Axial T2WI MR demonstrates a posterior fossa meningioma <img src='/img/arrows/WS.png'/> with significant mass effect upon the cerebellum with interposed trapped CSF clefts <img src='/img/arrows/WO.png'/> and vessels <img src='/img/arrows/WC.png'/>.*
*Axial T2WI MR demonstrates a posterior fossa meningioma <img src='img/arrows/WS.png'/> with significant mass effect upon the cerebellum with interposed trapped CSF clefts <img src='img/arrows/WO.png'/> and vessels <img src='img/arrows/WC.png'/>.*
![Axial T1 C+ MR of a meningioma shows an avidly enhancing, dural-based mass splaying the cerebellar hemispheres, flattening the 4th ventricle <img src='/img/arrows/WC.png'/>, with dural tail <img src='/img/arrows/WO.png'/>.](images/app.statdx.com_image_thumbnail_c7247000-384b-463a-ac68-4cfddc8bc020_annotated_true_size_900_quality_90_c30a12c4.jpg)
![Axial T1 C+ MR of a meningioma shows an avidly enhancing, dural-based mass splaying the cerebellar hemispheres, flattening the 4th ventricle <img src='img/arrows/WC.png'/>, with dural tail <img src='img/arrows/WO.png'/>.](images/app.statdx.com_image_thumbnail_c7247000-384b-463a-ac68-4cfddc8bc020_annotated_true_size_900_quality_90_c30a12c4.jpg)
**Meningioma**
*Axial T1 C+ MR of a meningioma shows an avidly enhancing, dural-based mass splaying the cerebellar hemispheres, flattening the 4th ventricle <img src='/img/arrows/WC.png'/>, with dural tail <img src='/img/arrows/WO.png'/>.*
*Axial T1 C+ MR of a meningioma shows an avidly enhancing, dural-based mass splaying the cerebellar hemispheres, flattening the 4th ventricle <img src='img/arrows/WC.png'/>, with dural tail <img src='img/arrows/WO.png'/>.*
![Coronal T1 C+ MR demonstrates the diffuse enhancement of meningeal carcinomatosis from metastatic xanthoastrocytoma <img src='/img/arrows/WS.png'/> spread throughout the posterior fossa, folia, and also more cephalad.](images/app.statdx.com_image_thumbnail_1cdce1bc-69d9-42bf-b62f-e5bb173bebec_annotated_true_size_900_quality_90_eb210c6e.jpg)
![Coronal T1 C+ MR demonstrates the diffuse enhancement of meningeal carcinomatosis from metastatic xanthoastrocytoma <img src='img/arrows/WS.png'/> spread throughout the posterior fossa, folia, and also more cephalad.](images/app.statdx.com_image_thumbnail_1cdce1bc-69d9-42bf-b62f-e5bb173bebec_annotated_true_size_900_quality_90_eb210c6e.jpg)
**Metastasis**
*Coronal T1 C+ MR demonstrates the diffuse enhancement of meningeal carcinomatosis from metastatic xanthoastrocytoma <img src='/img/arrows/WS.png'/> spread throughout the posterior fossa, folia, and also more cephalad.*
*Coronal T1 C+ MR demonstrates the diffuse enhancement of meningeal carcinomatosis from metastatic xanthoastrocytoma <img src='img/arrows/WS.png'/> spread throughout the posterior fossa, folia, and also more cephalad.*
![Sagittal T1WI MR shows tonsillar descent <img src='/img/arrows/WC.png'/> and dural thickening <img src='/img/arrows/WS.png'/> secondary to intracranial hypotension.](images/app.statdx.com_image_thumbnail_275e1525-c39f-4a67-a0c6-85527fff9775_annotated_true_size_900_quality_90_2634400b.jpg)
![Sagittal T1WI MR shows tonsillar descent <img src='img/arrows/WC.png'/> and dural thickening <img src='img/arrows/WS.png'/> secondary to intracranial hypotension.](images/app.statdx.com_image_thumbnail_275e1525-c39f-4a67-a0c6-85527fff9775_annotated_true_size_900_quality_90_2634400b.jpg)
**Intracranial Hypotension**
*Sagittal T1WI MR shows tonsillar descent <img src='/img/arrows/WC.png'/> and dural thickening <img src='/img/arrows/WS.png'/> secondary to intracranial hypotension.*
*Sagittal T1WI MR shows tonsillar descent <img src='img/arrows/WC.png'/> and dural thickening <img src='img/arrows/WS.png'/> secondary to intracranial hypotension.*
![Axial DWI MR shows a hyperintense mass <img src='/img/arrows/WS.png'/> in the midline posterior fossa.](images/app.statdx.com_image_thumbnail_34b283f3-4ea9-4e5a-9cb3-881ab4f80a29_annotated_true_size_900_quality_90_5cf04a76.jpg)
![Axial DWI MR shows a hyperintense mass <img src='img/arrows/WS.png'/> in the midline posterior fossa.](images/app.statdx.com_image_thumbnail_34b283f3-4ea9-4e5a-9cb3-881ab4f80a29_annotated_true_size_900_quality_90_5cf04a76.jpg)
**Epidermoid Cyst**
*Axial DWI MR shows a hyperintense mass <img src='/img/arrows/WS.png'/> in the midline posterior fossa.*
*Axial DWI MR shows a hyperintense mass <img src='img/arrows/WS.png'/> in the midline posterior fossa.*
![Sagittal T1 C+ MR demonstrates a mostly solid hemangioblastoma <img src='/img/arrows/WS.png'/> involving the cerebellar tonsils and effacing the cisterna magna.](images/app.statdx.com_image_thumbnail_1be0b435-f039-412e-b180-4268d6bd5c32_annotated_true_size_900_quality_90_9f29c937.jpg)
![Sagittal T1 C+ MR demonstrates a mostly solid hemangioblastoma <img src='img/arrows/WS.png'/> involving the cerebellar tonsils and effacing the cisterna magna.](images/app.statdx.com_image_thumbnail_1be0b435-f039-412e-b180-4268d6bd5c32_annotated_true_size_900_quality_90_9f29c937.jpg)
**Hemangioblastoma**
*Sagittal T1 C+ MR demonstrates a mostly solid hemangioblastoma <img src='/img/arrows/WS.png'/> involving the cerebellar tonsils and effacing the cisterna magna.*
*Sagittal T1 C+ MR demonstrates a mostly solid hemangioblastoma <img src='img/arrows/WS.png'/> involving the cerebellar tonsils and effacing the cisterna magna.*