Foramen Magnum

Intra-axial cervicomedullary masses

Nonneoplastic

- Syringomyelia

- Demyelinating diseases

Neoplastic - Gliomas, astrocy-tomas

- Nonglial neoplasms

- Metastases

In 25 % of Chiari I patients; secondary syrinxes due to trauma can be seen

• Multiple sclerosis

• Acute transverse myelopathy

• Miscellaneous (e.g., radiation, AIDS, vascular AVM)

Commonly of low grade, 50% occurring in the cervicomedullary junction. Extension of spinal cord gliomas into this area is also common. Other types of gliomas, however, such as anaplastic astrocytoma, gangliogan-glioma, ependymoma are also found here Inferior extensions of medulloblastomas in children and hemangioblastomas in adults are common in this area Rare optic optic chiasm recess infundibular recess anterior posterior commissure superior & inferior colliculi

-Great cerebral vein of Galen straight sinus tentorium cerebelli optic optic chiasm recess infundibular recess anterior posterior commissure

Foramen Magnum And Tentorium Cerebelli

tentorium cerebelli splenium of corpus callosum

PICA (posterior inf.— cerebellar artery)

C1 (anteriorarch)

Fig. 9 Intracranial tumors. Midsaggital anatomic diagram of the pineal and foramen magnum regions splenium of corpus callosum

PICA (posterior inf.— cerebellar artery)

C1 (anteriorarch)

Transverse sinus (sectioned)

occipital bone

— cisterna magna

C1 (posterior arch)

Fig. 9 Intracranial tumors. Midsaggital anatomic diagram of the pineal and foramen magnum regions

1. Glioma of the high cervical spinal cord (C2), producing a focal expansion of the spinal cord, is seen on this midsagittal T1 WI.

2. Meningioma. Axial CT demonstrates a calcified meningioma of the posterior part of the foramen magnum compressing the medulla oblongata.

3. Epidermoid cyst. Axial CT with a cystic lesion of the foramen magnum causing compression of the medulla oblongata.

4. Chiari II malformation. Sagittal T1 WI shows a descent of the cerebellar tonsils and compression of the medulla oblongata and associated syringomyelia.

5. Osteolysis of C2 and a mass of soft tissues producing compression and displacement of the spinal cord is seen on coronal T1 WI.

6. Atlantoaxial subluxation. Sagittal T2WI shows atlantoaxial subluxation with the development of inflammatory tissue around the dens of C2. This pathology causes stenosis of the foramen magnum and compression of the spinal cord and lower medulla. Focal myelinolysis is indicated by a high intensity signal.

Calcified Mass Foramen Magnum

Anterior extramedullar intradural masses

Ectatic vessel, aneurysm

Meningioma Schwannoma

Epidermoid tumors

Metastases

Paragangliomas

Arachnoid, inflammatory and neurenteric cysts

The most common mass anterior to the medulla is a tortuous, ectatic vertebral artery. Occasionally, aneurysms of the vertebral artery or PICA are seen

The most common primary neoplasm in this area

From cranial nerves IX and XI. Neurofibromas from existing spinal nerve segments occur laterally

Cisternal, perineural, and skull base

Chordomas, rheumatoid nodules

Posterior extramedullar intradural masses

Congenital or acquired tonsillar herniation

Ependymoma, medullo-blastoma

Extradural masses

Trauma Arthropathies

- Rheumatoid arthritis

- Osteoarthritis

- Paget's disease

- Osteomyelitis

Congenital anomalies

- Os odontoideum

- Vertebralization of occipital condyles

- Odontoid hypoplasia

- Arch hypoplasias or aplasias

Neoplasms

Extraosseous intradural

Represents 5-10% of all foramen magnum masses

Intra-axial caudal extension of posterior fossa neoplastic masses

Odontoid fractures

Affects 80% of cervical spine in these patients, causing severe cord compression

- Metastases

• Osteocartilaginous tumors chondroma and chon-drosarcoma

Hematogenous or local extensions from nasopharyngeal or skull base tumors

AIDS: acquired immune deficiency syndrome; AVM: arteriovenous malformation; PICA: posterior inferior cerebellar artery.

pituary gland foramen spino-

pituary gland

Jugular Foramen Syndrome

superior sagital sinus — olfactory n. (CN I) -optic n. (CN II)

sigmoid sinus transverse sinus superior sagital sinus — olfactory n. (CN I) -optic n. (CN II)

sigmoid sinus transverse sinus

r glossopharyngeal n. (CN IX)

accessory n. (CN XI)

hypoglossal n. (CN XII) medulla spinal subarachnoid space -jugular foramen

Fig. 11 Intracranial tumors. Anatomic drawing depicting the endocranial aspect of the skull base

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