Neuroanatomy: Meninges, Ventricles, CSF

Neuroanatomy of Meninges

• Meninges are 3 layers of connective tissue that surround the CNS, including the spinal cord & nerve roots, brain stem, and cerebrum.

Meningeal Layers

• Dura mater (dense connective tissue) is the outermost layer, also known as pachymeninx.
• Arachnoid is the middle layer, consisting of reticular fibers.
• Pia mater is the innermost layer, lying directly on the surface of the brain and spinal cord.

Dura Mater (Cranial Portion)

• Composed of 2 layers: outer periosteal or endosteal layer and inner meningeal layer.
• 4 folds (projections) of dura mater in the cranial portion:
  • Falc cerebri: midline, from crista galli to internal occipital protruberance.
  • Tentorium cerebelli: roofs over the posterior cranial fossa, forming a tent-like shape, and separates the cerebrum from the cerebellum.
  • Falx cerebelli: small, midsagittal septum below the tentorium, separating cerebellar hemispheres.
  • Diaphragma sellae: over the hypophyseal fossa, perforated by the infundibulum.

Dura Mater (Spinal Portion)

• Continuation of the meningeal layer of cranial dura, periosteum of vertebrae.
• Epidural space contains areolar tissue and internal vertebral venous plexus.
• Largest spinal epidural space at L2, suitable for epidural anesthesia.
• Spinal dura ends at S2, where the caudal termination invests the filum terminale to form.