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You are watching: Which of the three spinal meninges is the most superficial

StatPearls . Endowment Island (FL): StatPearls Publishing; 2021 Jan-.


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Introduction

The spinal cord and mind are encased within 3 layers of tissue referred to as the meninges. The spinal meninges specifically enclose the spinal cord and also stretch native the brainstem under to the filum terminale. The layers of the meninges are, native deep to superficial, the pia mater, the arachnoid mater, and also the dura mater. The surname of these layers offer information on your qualities. Pia, which is Latin for “loving,” and also mater, which is Latin because that “mother,” consist of the pia mater, or “loving mother,” i m sorry is straight attached to the spinal cord and inseparable. The arachnoid mater includes a net of fiber beneath it in the subarachnoid space, and also the dura mater or “hard mother” is the challenging outer layer of the meninges. The principal duty of the spinal meninges is come protect and also support the spinal cord.<1>


Structure and also Function

The Epidural Space

Between the ligamentum flavum and also the superficial dura mater is the spinal epidural space. This location consists of various structures such together adipose tissue, connective tissue, nerves, the internal vertebral venous plexus, and also lymphatics. That is a site typically used because that analgesic purposes and is a potential site for infection.<1><2>

The Dura Mater

The many superficial layer of the meninges is the dura mater. While it has two great in the cranial segment, the spinal dura mater only has the deep meningeal layer. The periosteal layer, i beg your pardon is the superficial layer of the dura in ~ the calvarium, end at the foramen magnum, with only the meningeal layer continuing down along the spinal cord.<1> The dura mater is the strongest of the 3 layers, through some animal studies showing that the thickness that the dura decreases together it descends towards the coccyx.<3> together they make their means out of the vertebral canal, the spinal nerves space coated through dura mater as they departure into the epidural space, developing the epineurium.

The Subdural Space

The spinal subdural space is only a potential space; typically, it is not present under normal physiological conditions. That exists in between the dura and arachnoid mater.<1>

The Arachnoid Mater

The spinal arachnoid mater is in between the dura and the pia mater. The arachnoid mater is avascular and primarily exists to assist maintain cerebrospinal liquid (CSF) metabolism.<4>

The Subarachnoid Space

The spinal subarachnoid space is located between the arachnoid and also pia mater and is filled v CSF. Arachnoid trabeculae extend in between these 2 layers within the subarachnoid an are to provide the subarachnoid an are its properties spiderweb appearance. The choroid plexus produce CSF within the mind ventricles, and CSF start the spinal subarachnoid spaces via the median and lateral apertures. The functions of the CSF encompass protection and also nourishment of the mind and spinal cord.<4> The spinal subarachnoid space, especially the lumbar cistern inferior to the conus medullaris, has actually clinical definition in diagnosing meningitis, as it is the website of lumbar puncture.

The Pia Mater

The spinal pia mater is the deepest class of the meninges and is straight attached to the surface of the spinal cord. The pia mater is composed primarily of collagen and also reticular fibers.<5> The pia mater will continue past the conus medullaris and also fuse right into the filum terminale, anchoring the spinal cord to the coccyx inferiorly. One of the main functions of the spinal pia mater is that it has important elastic characteristics that aid maintain stiffness of the spinal cord, and also it assists the cord return to its initial shape ~ compression.<6> The spinal pia mater additionally contains denticulate ligaments, which prolong outwards to assist anchor the spinal cord to the spinal dura mater, further assisting through stabilizing the cord.<7>


Embryology

The spinal meninges, along with the cranial meninges, have a complex embryologic origin. The pia and also arachnoid mater, jointly known together the leptomeninges, are obtained from the neural crest. The neural stakes itself forms from the ectoderm-derived neuroectoderm and neural plate. The dura mater derives from the mesoderm.<4><8>


Blood Supply and also Lymphatics

The blood supply to the spinal meninges comes mainly from the anterior spinal artery and also posterior spinal arteries. The single anterior spinal artery originates indigenous the vertebral arteries, i m sorry each offers of collaterals the fuse and descend as the anterior spinal artery before ending up being the basilar artery. The combine posterior spinal arteries also receive your blood supply from the vertebral arteries. Extr segmental medullary arteries likewise feed into these anterior and also posterior spinal arteries via enntrance gate points in ~ the nerve roots, the biggest being the artery that Adamkiewicz, i beg your pardon provides additional blood it is provided to the anterior spinal artery and also are generally present in between T9 and also L2.<9><10>

The venous drainage the the spinal meninges is with the internal and also external vertebral venous plexuses. These kind a complicated and valve-less system of drainage that is constant with the venous device of the mind and has drainage right into the azygous venous system, the portal venous system, renal veins, the superior and inferior vena cava, and also others.<11>


Nerves

The spinal meninges have far-ranging nonspecific innervation, consisting of both sensory and also sympathetic fiber. Plentiful sympathetic nerve fibers with solid associations to blood vessels are current within all 3 layers that the meninges.<12><13> Additionally, the peridural membrane has abundant sensory and nociceptive innervations, which most likely play a role in earlier pain.<14>


Surgical Considerations

There are plenty of tumors the the spinal meninges, one example being a meningioma. If the bulk of meningiomas show up in the cranial meninges, lock are also known to thrive in the spinal portions, especially in the thoracic and cervical portions. Spinal meningiomas are typically benign and also slow-growing and also typically occur in females aged 50 to 70 years old. Children with neurofibromatosis form 2 are additionally susceptible to emerging spinal cord tumors, such together meningiomas and also intramedullary tumors.<15><16>

The much more common tumors that impact the spinal meninges are epidural metastases, which can primarily arise from breast, lung, and prostate primary cancers. These metastases can prosper on one of two people the bony vertebra, the paravertebral tissues, or within the epidural room overlying the spinal meninges. This metastases are most usual in the thoracic region and deserve to cause significant compression that the spinal cord or cauda equina syndrome if in the lumbar-sacral region.<17>


Clinical Significance

Clinically, the spinal meninges are essential in their duty in the spread of cancers and also the diagnosis of meningitis. The spinal epidural space contains a device of epidural veins well-known as the Batson plexus, which shows up to bring implications in the spread out of miscellaneous infections and also metastatic cancer, such as prostate cancer, bring about the metastatic epidural masses described earlier.<1><17> Compression the the spinal cord by tumors of the meninges and also epidural an are can reason a plethora the neurological symptoms, such together motor weakness, top motor signs (i.e., optimistic Babinski reflex), urinary incontinence, and also pain.<17>

Clinicians utilize the spinal subarachnoid an are when performing a diagnostic lumbar puncture, which might be helpful in assessing the presence of meningitis, a subarachnoid bleed, or document the opening push of CSF. A lumbar puncture is among the first tests performed as soon as a patient presents v the cardinal attributes of meningitis (headache, fever, and also nuchal rigidity). In adults, the L3/L4 interspinal room is the preferred location to safely collect the CSF indigenous the lumbar cistern. The L4 spinous procedure is approximately midline in ~ the level the the iliac crests, well-known as the intercristal or Tuffier line, do the L3/L4 interspinal room just above this landmark. The patient should then be in either the left lateral decubitus position or seated with the spine flexed. The needle have to be inserted with the bevel parallel to the yarn of the dura mater (up or under if left lateral decubitus and also bevel to one of two people the right or left if sit position, to mitigate resistance when passing through the meninges and avoid harming any type of fibers that the cauda equina) right into the L3/L4 interspinal an are at a slim angle. The needle will certainly then pass with the complying with structures: skin, subcutaneous tissue, the supraspinous ligament, the interspinous ligament, the ligamentum flavum, the epidural space, the dura mater, the arachnoid mater, and also the subarachnoid space/lumbar cistern. The patient should receive counsel to expect usual side effects such as headache, which occurs in a 3rd of all cases, and pain is frequently relieved once lying supine.

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<18>

Anesthesia during childbirth can likewise be ceded using the very same landmarks as placing a lumbar puncture needle. An epidural anesthetic would be placed in the epidural space, when the location of spinal anesthesia will certainly be within the CSF the the lumbar cistern. Epidurals space typically an ext precise but have a longer onset of activity and require a bigger dose than spinal anesthesia. Levobupivacaine and also bupivacaine space two generally used agents for epidural and also spinal anesthesia.<19>