Introduction

Anatomy and Physiology of Pain Principles of Pain Spinal Cord Stimulation Intrathecal Drug Delivery Selective Spinal Cord Lesioning Neuroanesthesia

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The Spinal Cord


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The spinal cord is a thin column of nerve tissue that extends downward from the brain through the vertebral column to the level of the second lumbar vertebra. The spinal cord transmits pain signals and other nerve impulses to and from the brain and controls reflex actions. The spinal cord is approximately 18 inches (46 cm) in length and up to 0.75 inches (1.9 cm) in diameter at its widest point.
The spinal cord has three main components:
● Spinal nerves
● Nerve tissue
● Meninges

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Spinal nerves
The spinal nerves originate in the spinal cord and carry impulses to muscles and other structures, and return impulses received from sensory organs. There are 31 pairs of spinal nerves that provide two-way transmission of nerve impulses between the spinal cord and the arms, legs, neck, and trunk.
Spinal nerves contain both sensory (incoming) and motor (outgoing) nerve fibers. The sensory nerve fibers enter the spinal cord from the dorsal (back)
area. The motor nerve fibers exit through the anterior (ventral) area.
Each spinal nerve pair emerges from the spinal cord from two short branches, or roots, which lie within the vertebral column:
● Dorsal root
● Ventral root

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Dermatomes
A dermatome is an area of the body supplied by a particular section of spinal nerves connected to a specific vertebral body. In the torso, the dermatomes form consecutive bands. A map of these bands, called a dermatome map, is an important diagnostic tool for pain syndromes.

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Nerve tissue
The spinal cord consists of two types of nerve tissue:
● Grey matter
● White matter

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Grey matter
Grey matter makes up the centre of the spinal cord. Grey matter consists primarily of dendrites, which are thread-like extensions of a neuron, and cell bodies of neurons. Both of these neuron components receive nerve impulses from other neurons.

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White matter
White matter surrounds the grey matter. White matter consists of bundles of nerve fibers that form conduction paths called spinal tracts. The nerve fibers are surrounded by myelin. Nerves that are myelinated transmit information to and from the brain faster than nerves that are not myelinated.

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Meninges
Meninges are membranous tissue coverings that surround and protect the spinal cord from injury. There are three types of meninges that surround the
spinal cord:
● Dura mater
● Arachnoid membrane
● Pia mater
Dura matter is the tough, protective, outer covering that is made up of collagenous (protein) tissue. The arachnoid membrane is a delicate membrane that covers the subarachnoid, or intrathecal space. The pia matter is a vascular membrane that closely attaches to the spinal cord and surface of the brain. The pia matter is the innermost layer of the meninges.

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Intraspinal space
The layering of the dura matter, arachnoid membrane and pia matter creates ‘spaces’ in the spinal cord, known as intraspinal spaces. There are two types of intraspinal spaces:
● Epidural space
● Intrathecal or subdural space

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Epidural space
The epidural space lies between the vertebrae and the dura matter. The epidural space is filled with fatty tissue and consists of a network of large, thin-walled veins and spinal nerve extensions. This is shown in Figure 3.Neurostimulation leads are placed in the epidural space.

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Intrathecal or subdural space
The intrathecal or subdural space is a potential space that is located between the dura mater and the arachnoid membrane. This small-volume space is filled with cerebral spinal fluid (CSF). CSF completely bathes the brain and spinal cord, which provides a fluid cushion against shocks. This is shown in Figure 6. The drug delivery catheter is usually placed in the intrathecal space to provide site-specific delivery of a pain-relieving drug such as morphine to opioid receptors in the spinal cord. However the screening test (which tests a patients response to intraspinal morphine) can often be conducted by delivering the drug to the epidural space).
 


 

What’s Up
August/14/2007
Inomed ISIS Intraoperative neurophysiological monitoring started to function in all our related surgeries.
Oct /07/2009
The author celebrating 30 years experience in neurosurgery.
Nov/28/2013
Skyra 3 tesla magnetom with all clinical applications  are running in the neurosuite.
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