Posterior Cranial Fossa : Mnemonic

Boundaries

1. Anteriorly: Clivus (Basiocciput + Basisphenoid)
2. Laterally: Petrous temporal bone + Occipital bone
3. Floor: Occipital bone
4. Roof: Tentorium cerebelli (separates cerebellum from cerebral hemispheres)

Foramina

Mnemonic: IJHM (International Journal of Hospitality Management) from lateral to medial

1. Internal acoustic meatus (IAM)

• CN VII
• CN VIII
• Nervus intermedius or Intermediate nerve of Wrisberg (sensory and parasympathetic branch of CN VII)
• Labyrinthine vessels (branches of AICA)

2. Jugular foramen

Mnemonic: IPS 9, 10, 11
IPS + SS = IJV

• CN IX
• CN X
• CN XI
• Internal Jugular vein (IJV)
• Inferior Petrosal sinus (IPS)
• Sigmoid sinus (SS)

3. Hypoglossal canal

• CN XII
• Meningeal branch of ascending pharyngeal artery
• Hypoglossal venous plexus

4. foramen Magnum

• Medulla oblongata
• Spinal accessory nerve (CN XI)
• Vertebral and posterior spinal arteries
• Apical ligament of dens
• Membrane tectoria

Contents

1. Midbrain
2. Pons
3. Medulla
4. Cerebral and Cerebellar hemispheres
5. Dura and Tentorium cerebelli (encloses occipital sinus, superior sagittal sinus and paired transverse sinus)

Clinical consideration

Pediatric posterior fossa tumors:

• Mnemonic: MAGE (In order of prevalence)
  • Medulloblastoma: 30-40%
  • Astrocytoma (pilocytic): 25-35%
  • Glioma: 20-25%
  • Ependymoma: 10-15%

Cerebellar tonsil herniation: Herniation of pons and medulla oblongata through the foramen magnum due to raised ICP