Central Nervous System
The central nervous system (CNS) enables the body to react to continuous changes in the external and internal environment. It controls and integrates various activities of the body. From a structural standpoint the central nervous system is composed two structures[1]:
- Brain – located within the skull (also called the cranium)
- Spinal Cord – located within the vertebral column (making it the most protected organ system in the body)[2]
The primary role of the central nervous system is twofold.
- Integrate and coordinate incoming and outgoing neural signals.
- Control higher mental functions such as thinking and leaning.
The brain is control center of the nervous system and is where all the signals from the body are processed including pain. The brain is composed of the cerebrum, cerebellum, and the brainstem – each located within the skull or cranial cavity and each with a specific set of functions.
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Sphenopalatine Ganglion Block
Consistent and unrelenting facial pain and/or chronic headaches can make simple day to day activities miserable and ruin your life. The Sphenopalatine Ganglion Block is minimally invasive, short and safe procedure that is done through your nose. It is potentially life changing as it offers immediate relief and can free a patient from the endless merry-go-round of cycling through different pain medications.
Spinal Cord Stimulation (SCS)
SCS is an innovative procedure that has yielded results for patients with pain in their back or limbs who have not found relief from any other treatments. In SCS, an electrical pulse is delivered directly to the spine, blocking certain neuron fibers’ access to the brain and consequently the brain’s ability to sense the previously perceived pain. Patients who qualify for this procedure report up to a 70% reduction in pain.
The brain and spinal cord are covered by 3 different layers of membrane, collectively called the meninges.
Dura mater – outermost layer
- above it is the extradural or epidural space
- below the dura mater is the arachnoid mater and cerebrospinal fluid (CSF)
Arachnoid mater – middle layer
- spider web-like in appearance
- cushions the CNS
- the outermost layer of the subarachnoid space – contains the CSF
Pia mater – innermost layer
- thin, delicate layer
- firmly attached to the brain and spinal cord
The layers of the meninges create and separate 3 compartments or spaces surrounding the structures of the CNS. These spaces have different contents, significance, and each serve their own importance when treating pain.3
| Compartment/Space | Location | Contents | Significance |
|---|---|---|---|
| Epidural space | Above the dura mater | Fatty tissue, small blood vessels, internal vertebral venous plexus | Medications can be injected here to relieve pain – most importantly an epidural steroid injection (i.e. Lumbar or Cervical epidural steroid injection) |
| Subdural space | Between dura mater and arachnoid mater | Potential space with no true contents – small vessels traverse through this space | Small veins in the area can be torn from an accident causing blood to leak into this space leading to a subdural hematoma |
| Subarachnoid space | Between arachnoid mater and pia mater | CSF | Medications in extremely small doses can be delivered to relieve pain and/or spasticity, thus minimizing the side effects (Intrathecal Pumps) |
CSF is a clear, colorless fluid located within the subarachnoid space. It is produced by the choroid plexus and serves a number or purposed for the CNS.
- Acts as a cushion or buffer for the brain and spinal cord – controls pH, temperature, and pressure
- Provides mechanical and immunologic protection for the CNS
- Regulates blood flow to the CNS
- Cleans waste
The CNS can be further classified into grey and white matter, each composed to different types of classes of cells of the nervous system.
- Grey matter – comprised of groups of cell bodies of the neurons (the cells of the nervous system responsible for sending and receiving signals
- White matter – comprised of bundles of axons (the portion of the neurons that conduct outgoing signals) and the myelin sheaths that surround them
It is the combination of these two types of matter that allow for transmission of signals from various parts of the body to the brain. The spinal tracts are segmented sections of white matter, each specializing in conducting very specific sets of signals and sensations to the brain. There are two types of tracts, 1) afferent – sensory/ascending tracts, and 2) efferent – descending – motor/descending tracts.4
| Tract | Class | Function |
|---|---|---|
| Spinothalamic (Anterior and Lateral) | Afferent | Transmits information regarding pain, temperature, itch and crude touch |
| Dorsal Column (Nucleus Cuneatus and Nucleus Gracilis) | Afferent | Light touch, vibration sense, and proprioception |
| Spinocerebellar (Anterior and Posterior) | Afferent | Proprioception |
| Corticospinal (Anterior and Lateral) | Efferent | Fine movement |
| Rubrospinal | Efferent | Controls tone of flexor muscles |
| Reticulospinal | Efferent | Maintains locomotion and postural control |
| Tectospinal | Efferent | Mediates reflex movements |
| Vestibulospinal (Medial) | Efferent | Controls tone of extensor muscles of legs to maintain upright posture |
| Vestibulospinal (Lateral) | Efferent | Controls head and body orientation |
Blood supply to the spinal cord is made up of multiple arteries.
- Posterior Spinal Arteries – arise directly or indirectly form the vertebral arteries, run inferiorly along the sides of the spinal cord, and provide blood to the posterior third of the spinal cord.
- Anterior Spinal Arteries – arise from the vertebral arteries, uniting to form a single artery, which runs within the anterior median fissure. They supply blood flow to the anterior two thirds of the spinal cord.
- Radicular Arteries – reinforce the posterior and anterior spinal arteries. These are branches of local arteries. They enter the vertebral canal through the intervertebral foramina.
The Artery of Adamkiewicz is the name given to the lumbar radicular artery. It is larger and arises from a branch of the descending aorta in the lower thoracic or upper lumbar vertebral levels (between T10 and L3) and anastomoses with the anterior spinal artery in the lower thoracic region. The lower thoracic region is referred to as the watershed area. It is the major source of blood to the lower anterior two thirds of the spinal cord.5
Veins of spinal cord drain mainly into the internal venous plexus.
Get Answers to Your Questions at the Ainsworth Institute
The key to finding the proper treatment for any type of pain is getting a proper diagnosis. Not all types of pain respond to the same treatments and the window for improvement can be limited. The experts at Ainsworth Institute offer the most advanced pain management treatments available today, including advanced clinical trials that aren’t yet available to the general public. Call us today for an appointment so we can get you started on your road to recovery.
References
[1] Moore K, Agur A: Essential Clinical Anataomy: 2nd edition: 32-36 2002
[2]Haines DE; Neuroanatomy: An Atlas of Structures, Sections, and Systems 5th ed: Lippincott Williams & Wilkins , 1999
[3]Miller RD, Eriksson LI, Fleisher LA, et al.: Miller’s Anesthesia. 7th ed. Elsevier Churchill-Livingstone; 2009
[4]Cuccurullo S, et al: Physical MEdicine and Rehabiliation Review: 2nd edition 490-493, 2004
[5]Griepp E, et al: The anatomy of the spinal cord collateral circulation. Annals of Cardiothorac Surg. Sep 2012; 1(3): 350–357
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