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Meninges

The meninges are three concentric connective tissue membranes that envelop the brain and spinal cord. They provide mechanical protection, support vascular structures, facilitate cerebrospinal fluid (CSF) circulation, and form important compartments and spaces relevant to intracranial pathology.

They consist of the dura mater, arachnoid mater, and pia mater, each with distinct anatomical, functional, and radiologic characteristics. Disorders of the meninges are common and clinically significant, including infection, hemorrhage, inflammation, neoplasia, and postoperative change.

Synonyms

  • Meningeal layers

  • Craniospinal coverings

Location

  • Surround the brain within the cranial vault

  • Encase the spinal cord within the vertebral canal

  • Extend from the foramen magnum to the terminal filum

  • Closely related to dural venous sinuses, CSF spaces, and neurovascular structures

Anatomical components

Dura mater:

  • Outermost, thick, fibrous layer

  • Cranial dura: consists of periosteal and meningeal layers

  • Forms dural venous sinuses and dural reflections (falx cerebri, tentorium cerebelli)

  • Pain-sensitive layer

Arachnoid mater:

  • Middle, thin, avascular membrane

  • Lines the inner surface of the dura

  • Bridges over sulci without entering them

  • Forms arachnoid villi and granulations for CSF absorption

Pia mater:

  • Innermost, delicate vascular membrane

  • Closely adherent to the brain and spinal cord surface

  • Follows gyri and sulci

  • Envelops penetrating vessels

Meningeal spaces

Epidural space:

  • Potential space in the cranium

  • True space in the spinal canal containing fat and venous plexus

Subdural space:

  • Potential space between dura and arachnoid

  • Site of subdural hematoma

Subarachnoid space:

  • True space between arachnoid and pia mater

  • Contains CSF, arteries, veins, and cranial nerves

Relations

Externally:

  • Inner table of skull (cranial)

  • Vertebral canal (spinal)

Internally:

  • Brain and spinal cord parenchyma

Vascular relations:

  • Dural venous sinuses within dura

  • Cortical and deep vessels within subarachnoid space

Function

  • Mechanical protection: Cushions brain and spinal cord

  • CSF containment: Maintains CSF circulation and pressure

  • Vascular support: Houses venous sinuses and meningeal vessels

  • Compartmentalization: Limits spread of infection or hemorrhage

  • Immunologic role: Participates in inflammatory and immune responses

Clinical significance

  • Meningitis: Infection of leptomeninges (arachnoid and pia)

  • Subdural hematoma: Venous bleeding in subdural space

  • Epidural hematoma: Arterial bleeding between skull and dura

  • Meningioma: Extra-axial tumor arising from arachnoid cap cells

  • Leptomeningeal metastasis: Malignant infiltration of pia–arachnoid

  • Intracranial hypotension: Pachymeningeal thickening and enhancement

  • Postoperative change: Expected dural enhancement after surgery

MRI appearance

T1-weighted images:

  • Normal dura: Low-to-intermediate signal, thin and linear

  • Arachnoid and pia: Typically not separately visualized

  • Subacute blood: High signal depending on age

T2-weighted images:

  • Normal dura: Low signal intensity

  • CSF in subarachnoid space: High signal

Post-contrast T1-weighted images:

  • Normal dura: Thin, smooth enhancement may be seen

CT appearance

Non-contrast CT:

  • Normal meninges: Usually not visualized

Post-contrast CT:

  • Normal: Minimal dural enhancement

MRI images

MRI Meninges coronal anatomy image -img-00000-00000

MRI images

MRI Meninges sagittal anatomy image -img-00000-00000