Meninges

• Dura mater


  • 2 layers
  • Periosteal layer: attaches to the inner surface of the skull
  • Meningeal layer: attaches to the arachnoid on one side and the periosteal layer on the other
• Extensions of the dura mater

  • Falx cerebri: sickle shaped, between the two cerebral hemispheres
  • Tentorium cerebelli: tent, covers the cerebellum
  • Falx cerebelli: sits between the two cerebellar hemispheres
• There is an extension of dura mater called the filum terminale external that attaches the spinal cord to the coccyx bone for cord stability
• Sinuses that extend into the dural extensions

  • Superior sagittal sinus lies in the attached edge (ie where it attaches to the skull) of the falx cerebri
  • Inferior sagittal sinus lies in the free edge of the falx cerebri (i.e. the inferior edge of the falx cerebri)
  • Straight sinus lies in the junction between the falx cerebri and tentorium cerebelli
  • Transverse sinus lies in the attached edge of the tentorium cerebelli
  • Occipital sinus lies in the falx cerebelli
• Compartments created by dural reflections

  • Supratentorial compartment – i.e. above the tentorium cerebelli
  • Infratentorial compartment – i.e. below the tentorium cerebelli
  • Falx cerebri compartmentalises left and right cerebral hemispheres
• Brain herniation


  Occurs when something inside the skull produces pressure that moves brain tissue and blood vessels away from their usual position inside the skull
• Brain herniation is most often the result of brain swelling or bleeding from a head injury, stroke or brain tumour
• Uncal herniation


  Occurs when the uncus (most medial part of the temporal lobe) herniates into the anterior part of the opening of the tentorial notch
• Symptoms of uncal herniation

  • Dilated pupil
  • Hemiplegia: paralysis on one side of the body
  • Coma
• Uncal herniation


  • Compression of the oculomotor nerve (causing pupil dilation)
  • Compression of the cerebral peduncles (causing hemiplegia)
  • Compression of the brainstem reticular formation (causing unconsciousness)
• Central herniation


  Downward movement of the thalamic region and brainstem through the tentorial notch
• Cingulate (subfalcine) herniation


  Displacement of the cingulate cortex under the falx cerebri, may be associated with anterior cerebral artery occlusion
• Upward cerebellar herniation


  Upwards transtentorial herniation of posterior fossa contents
• Tonsillar herniation (Chiari malformation)

  Downward herniation of the cerebellar tonsils into the foramen magnum, leading to compression of the medulla (causing respiratory arrest, blood pressure instability, and death)
• What are the dura layers of the spinal cord?

  There is only 1 layer, the meningeal layer
• Enlargements in Subarachnoid space

  Interpeduncular cistern

  Quadrigeminal cistern

  cisterna magna

  prepontine cistern

  lumber cistern
• Lumbar Cistern


  name given to the subarachnoid space of the lower lumbar spinal canal.

  contains cauda equina
• Potential Space: brain

  Epidural Space: between skull and dura

  Subdural space: between dura and arachnoid
• Potential space: spinal cord 


  Subdural space: between dura and arachnoid
• Actual space: brain 


  Subarachnoid space: between arachnoid and pia
• Actual space: spinal cord 


  Epidural space: between vertebra and dura

  Subarachnoid space: between arachnoid and pia