Functional anatomy of the spinal cord and cranial meninges: CSF conducting pathways

Vocabulary flashcards covering the major terms and concepts from the lecture notes on spinal cord meninges, cranial meninges, CSF, and related neuroanatomy.

Dura mater (pachymeninx)

Outermost fibrous coat of CNS; in the brain has external endosteal and internal meningeal layers and forms venous sinuses; in the spinal cord it covers the cord from foramen magnum to S2 and is fixed by sacro-dural ligaments (e.g., Trolard).

Leptomeninx

Collective term for the arachnoid mater and pia mater.

Arachnoid mater

Middle coat of the spinal meninges; ‘spider’web-like membrane, surrounds the cord, attached to the inner surface of the dura, devoid of blood vessels.

Pia mater spinalis

Thin coat containing blood vessels; inner surface follows spinal cord contours; has two layers (intima pialis and stratum epipiale) and gives rise to denticulate ligaments.

Denticulate ligaments

Extensions of the pia mater that pass between spinal nerves, partially dividing the subarachnoid space into anterior and posterior parts.

Epidural space (spinal)

Space between the vertebral canal’s inner surface and the outer dura mater; contains fat and the internal vertebral venous plexus.

Subdural space

Potential space between dura mater and arachnoid mater.

Subarachnoid space

Space between arachnoid and pia; contains CSF; enlarges in regions called cisterns.

Lumbo-sacral cistern

Expanded subarachnoid space below the spinal cord; contains CSF and nerve roots.

Arachnoid granulations (Pacchionian granulations)

Projections of arachnoid into venous sinuses that facilitate CSF absorption into venous blood.

Dura mater of the brain (DMB)

Cranial dura mater; two layers—external endosteal and internal meningeal; external adheres to skull bones, internal protects brain; forms venous sinuses by duplicature.

Falx cerebri, Falx cerebelli, Tentorium cerebelli, Diaphragma sellae

Dural partitions/lines in the brain formed by dural duplicatures; support and compartmentalize brain regions.

Venous sinuses

Dural venous channels formed by duplicature of the dura; lack valves; drain brain venous blood into internal jugular veins.

Sinuses of the vault of the skull

Superior sagittal, Inferior sagittal, Straight (sinus rectus), Transverse sinuses.

Sinuses of the base of the skull

Sphenoparietal, Cavernous, Intercavernous, Transverse occipital (basilar), Superior petrosal, Inferior petrosal, Petro-occipital (inconstant), Posterior occipital (inconstant), Sigmoid.

Arachnoid mater of the brain

Thin, avascular coat; devoid of vessels; external surface contacts dura; internal surface lined by flat cells; does not enter brain fissures.

Pia mater of the brain

Vascularized layer covering brain; follows brain contour; forms choroid plexuses with vessels; contributes to perivascular Virchow-Robin spaces.

Virchow-Robin space

Perivascular immunological space between a large vessel and the pia mater; can expand with leukocytes; usually seen on MRI.

Subarachnoid cisterns

Expanded portions of the subarachnoid space around brainstem/cerebellum (e.g., cisterna magna, ambient cistern, interpeduncular cistern, pontocerebellar cistern, etc.).

Choroid plexus

Vascular network within ventricles producing CSF; forms part of CSF secretion with other extraplexual sources.

CSF (cerebrospinal fluid)

Transparent, colorless fluid derived from blood plasma; similar electrolyte/glucose/pH to plasma but with distinct quantitative differences; normally free of blood.

CSF volume and turnover

Total CSF about 140 ml in adults; produced ~0.35 ml/min (roughly 400–500 ml/day); renewed every ~6 hours.

CSF composition differences

Water, Na+, HCO3−, creatinine similar to plasma; glucose/proteins/urea/uric acid/K/Ca/pH lower than plasma; Mg and Cl higher.

Origin of CSF

60–70% produced by choroid plexuses; 30–40% extraplexual origin.

Mechanism of CSF secretion

Water diffuses from blood plasma; ions actively transported into CSF via specialized transporters.

Circulation of CSF

Lateral ventricles → third ventricle via interventricular foramina; third → fourth via aqueduct; fourth → subarachnoid space via lateral/ median apertures; CSF drains into venous sinuses.

CSF drainage (venous route)

Reabsorption of CSF through arachnoid granulations into venous blood; additional transport by neurothelial cells.

Secondary drainage of CSF

Reabsorption along spinal/cranial nerve sheaths, at cortex capillaries, and at ventricular ependyma.

Blood–brain barrier (BBB)

Highly selective barrier separating blood from brain extracellular fluid; consists of capillary endothelium with tight junctions, basement membrane, and astrocyte foot processes; restricts most substances.

BBB features

Tight junctions, high electrical resistance, limited transcytosis; glucose/aminos acids transported by specific carriers; lipid-soluble molecules diffuse passively.

Circumventricular organs

Brain regions lacking a blood–brain barrier, allowing sampling of circulating factors.

Blood–CSF barrier

Barrier between blood and CSF formed at choroid plexus epithelium and ependyma; regulates CSF composition.

Meningeal innervation of DMB

Sensory innervation via meningeal branches of trigeminal nerve, vagus nerve, and first spinal nerve; Perlin described additional contributions from hypoglossal and other nerves.

Development of meninges

Dura mater from mesenchyme surrounding the neural tube; arachnoid and pia from neural crest (ectodermal origin).

Age-related dura features

Dura-skull connections stronger in children and the elderly; arachnoid granulations increase in number with age (200–300 to 400–600).

CSF conduits in spinal cord anatomy

Spaces and pathways within the CNS that carry and regulate CSF, including the epidural, subdural, and subarachnoid compartments and lumbo-sacral cistern.

Lumbar puncture

CSF sample/measurement technique performed between L3 and L4 vertebrae.

Puncture of the cerebello-medullary cistern

CSF access through the interval between the occipital bone and posterior arch of the atlas.

Examination techniques (CSF-related)

Lumbar puncture, cerebello-medullary cistern puncture, ventriculography with contrast, pneumoencephalography, CT and MRI.

Spinothalamic tract (lateral)

Ascending projection pathway conveying pain and temperature from body to thalamus and cortex; involves multiple relay neurons and decussation.

Anterior spinothalamic tract

Ascending pathway conveying crude touch and pressure (with decussation at level of entry).

Dorsal (posterior) spinocerebellar tracts

Proprioceptive pathways conveying muscle sense to cerebellum; posterior and anterior variants with different decussation patterns.

Corticospinal and corticobulbar tracts

Pyramidal motor pathways originating in motor cortex; control voluntary, refined movements; decussate largely at medullary levels.

Extrapyramidal pathways

Automatic/postural motor pathways (rubrospinal, reticulospinal, vestibulospinal, etc.) that modulate movement and muscle tone without pyramidal decussation.

Choroid plexus and CSF production balance

Choroid plexuses produce CSF; extraplexual sources contribute; CSF production balanced with drainage to maintain constant volume.

Questions and examination notes

Methods for assessing spinal cord/cranial meninges include lumbar puncture, cistern puncture, ventriculography, pneumoencephalography, CT and MRI.