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[3] The Back and ANS.pptx

  1. T H E B A C K A N D A U T O N O M I C N E R V O U S S Y S T E M WUHS Dr. Kyle Habet
  2. V E R T E B R A L C O L U M N : E M B R Y O L O G Y • During week 4, sclerotome cells of the somites (mesoderm) migrate medially to surround the spinal cord and notochord. • After proliferation of the caudal portion of the sclerotomes, the vertebrae are formed, each consisting of the caudal part of one sclerotome and the cephalic part of the next.
  3. T H E V E R T E B R A L C O L U M N • The vertebral column is the central component of the axial skeleton which functions in muscle attachments, movements, and articulations of the head and trunk. • The vertebrae provide a flexible support system that transfers the weight of the body to the lower limbs and also provides protection for the spinal cord. • The vertebral column is composed of 32–33 vertebrae (7 cervical, 12 thoracic, lumbar, and the fused 5 sacral, and 3–4 coccygeal), intervertebral disks, synovial articulations (zygapophyseal joints) and ligaments.
  4. V E R T E B R A E • A typical vertebra consists of an anterior body and a posterior vertebral arch consisting of 2 pedicles and 2 laminae. • The vertebral arch encloses the vertebral (foramen) canal that houses the spinal cord. • Vertebral notches of adjacent pedicles form intervertebral foramina that provide for the exit of the spinal nerves. • The dorsal projecting spines and the lateral projecting transverse processes provide attachment sites for muscles and ligaments.
  5. I N T E R V E R T E B R A L D I S C S • The intervertebral disks contribute to about 25% of the length of the vertebral column. They form the cartilaginous joints between the vertebral bodies and provide limited movements between the individual vertebrae. • Each intervertebral disk is numbered by the vertebral body above the disk. • Each intervertebral disk is composed of the following: 1. Anulus fibrosus consists of the outer concentric rings of fibrocartilage and fibrous connective tissue. The anuli connect the adjacent bodies and provide limited movement between the individual vertebrae. 2. Nucleus pulposus is an inner soft, elastic, compressible material that functions as a shock absorber for external forces placed on the vertebral column. The nucleus pulposus is the postnatal remnant of the notochord.
  6. L I G A M E N T S O F T H E V E R T E B R A L C O L U M N • The vertebral bodies are strongly supported by 2 longitudinal ligaments. Both ligaments are firmly attached to the intervertebral disks and to the bodies of the vertebrae. • Anterior longitudinal ligament forms a broad band of fibers that connects the anterior surfaces of the bodies of the vertebrae between the cervical and sacral regions. It prevents hyperextension of the vertebrae and is often involved in “whiplash” accidents. • Posterior longitudinal ligament connects the posterior surfaces of the vertebral bodies and is located in the vertebral canal. It limits flexion of the vertebral column. This ligament causes the herniation of a disk to be positioned posterolaterally.
  7. I N T E R V E R T E B R A L F O R A M E N • The intervertebral foramina are formed by successive intervertebral notches and provide for the passage of the spinal nerve. • The boundaries of the foramina are: • Anterior: bodies of the vertebrae and intervertebral disks • Posterior: zygapophyseal joint and articular processes • Superior and inferior: pedicles of the vertebrae
  8. D I S C H E R N I A T I O N • The nerve roots exit the spinal canal via the neural (intervertebral) foramina. Disc herniations are most common at the cervical and lumbosacral levels. • An understanding of the anatomy of the nerve roots and discs should make clear the following important rule of thumb: For both cervical and lumbosacral disc herniations, the nerve root involved usually corresponds to the lower of the adjacent two vertebrae. • For example, a C5–C6 disc herniation usually produces a C6 radiculopathy, an L5–S1 disc usually produces an S1 radiculopathy, and so on. • The explanation for this rule is different for cervical versus lumbosacral discs.
  9. D I S C H E R N I A T I O N • Thoracic, lumbar, and sacral nerve roots exit below the correspondingly numbered vertebral bone. • Cervical nerve roots, on the other hand, exit above the correspondingly numbered vertebral bone—except for C8, which has no corresponding vertebral bone and exits between C7 and T1. • Cervical nerve roots have a fairly horizontal course as they emerge from the dural or thecal sac near the intervertebral disc and exit through the intervertebral foramen. • Cervical discs are usually constrained by the posterior longitudinal ligament to herniate laterally toward the nerve root, rather than centrally toward the spinal cord. • Thus, in the cervical cord the nerve root involved usually corresponds to the lower vertebral bone of the disc space
  10. D I S C H E R N I A T I O N • Unlike cervical nerve roots, lumbar and sacral nerve roots must travel down- ward several levels before they exit the spinal canal. • In addition, the intervertebral foramina of the lumbosacral spine are such that the nerve roots exit some distance above the intervertebral discs. • As they are about to exit, the nerve roots move into the lateral recess of the spinal canal, and it is at this point that they are closest to the disc. • Thus, posterolateral disc herniations in the lumbosacral spine usually impinge on nerve roots on their way to exit beneath the next lower vertebral bone, which corresponds to the number of the nerve root involved.
  11. L U M B O S A C R A L D I S C H E R N I A T I O N • Symptoms: low back pain, radicular leg pain (radiates from the buttock into the leg worsens with sitting, coughing, valsalva, and sneezing, improves with standing) • Motor findings: See previous slide. • Provocative tests: • Straight leg raise: elicit pain and paresthesias in the leg at 30-70 degrees of hip flexion. Caused by tension in the L5 or S1 nerve roots • Bowstring sign: straight leg raise that is aggravated by compression of the popliteal fossa
  12. C E R V I C A L D I S C H E R N I A T I O N • Symptoms: occipital headache, neck pain, unilateral arm pain, numbness, weakness, and/or tingling • Physical Exam: depends on nerve root compressed • C5 radiculopathy: Weakness in deltoid and biceps. Diminished biceps reflex • C6 radiculopathy: Weakness in brachioradialis and wrist extension. Diminished brachioradialis reflex • C7 radiculopathy: Weakness in triceps and wrist flexion. Diminished triceps reflex • Spurling Test: Test by extending head, rotating and laterally bending to the affected side, and vertically compressing the head downward. • Positive if this maneuver reproduces pain in the ipsilateral arm
  13. Fragility fractures – fractures that occur due to decreased bone mineral density in patients with osteoporosis – include fractures of the hip (femoral neck), distal radius, lumbar spine, and proximal humerus.
  14. C O M P R E S S I O N F R A C T U R E S • Vertebral compression fractures are most commonly seen in young men due to trauma or in elderly women due to osteoporosis. In patients with multiple risk factors for osteoporosis including female sex, advanced age, and remote history of hysterectomy, a vertebral compression fracture is the most likely diagnosis. • Clinical features of acute vertebral compression fractures include point tenderness at the affected level and lower back pain worsened with mobility and lying down. Diagnosis can be made with an anterior-posterior and lateral radiograph, and MRI is indicated if spinal cord involvement is suspected.
  15. K Y P H O S C O L I O S I S • Lateral curvature of the spine. Normal neurologic exam • Most common type is adolescent idiopathic scoliosis • Epidemiology: Incidence 2% of the population • Female > male • Findings: Asymmetry in shoulder or waist. Curvature of the spine when standing or sitting. • Provocative tests: Adam forward bend test with inclinometer. • Patient’s back is assessed for scoliosis as they bend forward if inclinometer is > 6°, the test is suggestive for scoliosis • Imaging: Cobb angle >10 degrees
  16. S P I N A L M E N I N G E S • The brain and spinal cord are covered by three membranes called the meninges and are bathed in cerebrospinal fluid (CSF). • The spinal cord is protected and covered by 3 connective tissue layers within the vertebral canal: the dura mater, arachnoid, and pia mater.
  17. S P I N A L M E N I N G E S Dura Mater • The dura mater is a tough, cylindrical covering of connective tissue forming a dural sac which envelops the entire spinal cord and cauda equina. • The dura mater and dural sac terminate inferiorly at the second sacral vertebra level. • Superiorly, the dura mater continues through the foramen magnum and is continuous with the meningeal layer of the cranial dura. Arachnoid • The arachnoid is a delicate membrane which completely lines the inner surface of the dura mater and dural sac. It continues inferiorly and terminates at the second sacral vertebra.
  18. S P I N A L M E N I N G E S • The pia mater is tightly attached to the surface of the spinal cord and provides a delicate covering of the cord. • The spinal cord, with its covering of pia mater, terminates at the L1 or L2 vertebral levels in the adult. • There are 2 specializations of the pia mater that are attached to the spinal cord: • The denticulate ligaments are bilateral thickenings of pia mater that run continuously on the lateral sides of the midpoint of the cord. They separate the ventral and dorsal roots of the spinal nerves and anchor to the dura mater. • The filum terminale is a continuation of the pia mater distal to the lower end of the spinal cord. The filum terminale is part of the cauda equina which is composed of ventral and dorsal roots of lumbar and sacral nerves that extend below the inferior limit of the spinal cord.
  19. S P I N A L M E N I N G E S • There are 2 spaces related to the meninges. The epidural space is located between the inner walls of the vertebral canal and the dura mater. It contains fat and the internal vertebral venous plexus. The venous plexus runs the entire length of the epidural space and continues superiorly through the foramen magnum to connect with dural venous sinuses in the cranial cavity. • The subarachnoid space is a pressurized space located between the arachnoid and pia mater layers. It contains cerebrospinal fluid (CSF), which bathes the spinal cord and spinal nerve roots within the dural sac, and terminates at the second sacral vertebral level. • There are 2 important vertebral levels. The L1 or L2 vertebrae is the inferior limit of the spinal cord in adults (conus medullaris). S2 vertebra is the inferior limit of the dural sac and the subarachnoid space (cerebrospinal fluid).
  20. C L I N I C A L C O R R E L A T E • A lumbar puncture is used to inject anesthetic material in the epidural space or to withdraw CSF from the subarachnoid space. • A spinal tap is typically performed at the L4-L5 interspace. • A horizontal line drawn at the top of the iliac crest marks the level of the L4 vertebra. • When a lumbar puncture is performed in the midline, the needle passes through the interlaminar space of the vertebral column found between the laminae of the lumbar vertebrae. • The interlaminar spaces are covered by the highly elastic ligamenta flava.
  21. C L I N I C A L C O R R E L A T E • The internal vertebral venous plexus is valveless and connects with veins of the pelvis, abdomen, and thorax. • It provides a route of metastasis of cancer cells to the vertebral column and the cranial cavity.
  22. S P I N A L N E R V E S • There are 31 pairs of spinal nerves attached to each segment of the spinal cord: • 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal. The spinal nerves with the cranial nerves form part of the peripheral nervous system. • The C2 nerve exits via the intervertebral foramen superior to the C2 vertebra, and so on, until one reaches the C8 nerve, which then exits the intervertebral foramen above the T1 vertebra. All the remaining thoracic, lumbar, and sacral nerves exit via the intervertebral foramen below the vertebra of the same number
  23. D E R M A T O M E S • The region of skin innervated by the somatic sensory nerve axons associated with a single spinal ganglion at a single spinal cord level is called a dermatome. (Likewise, over the anterolateral head, the skin is innervated by one of the three divisions of the trigeminal cranial nerve, as discussed later.) • The neurons that give rise to these sensory fibers are pseudounipolar neurons that reside in the single spinal ganglion associated with the specific spinal cord level. • The first cervical spinal cord level, C1, does possess sensory fibers, but these provide minimal if any contribution to the skin, so at the top of the head the dermatome pattern begins with the C2 dermatome.
  24. D E R M A T O M E S • The dermatomes encircle the body in segmental fashion, corresponding to the spinal cord level that receives sensory input from that segment of skin. The sensation conveyed by touching the skin is largely that of pressure and pain. Knowledge of the dermatome pattern is useful in localizing specific spinal cord segments and in assessing the integrity of the spinal cord at that level (intact or “lesioned”). • The sensory nerve fibers that innervate a segment of skin and constitute the “dermatome” exhibit some overlap of nerve fibers. • Consequently, a segment of skin is innervated primarily by fibers from a single spinal cord level, but there will be some overlap with sensory fibers from the level above and below the primary cord level. • For example, dermatome T5 will have some overlap with sensory fibers associated with the T4 and T6 spinal levels. Thus, dermatomes provide a good approximation of spinal cord levels, but variation is common, and overlap exists.
  25. E A C H S P I N A L N E R V E I S F O R M E D B Y T H E F O L L O W I N G C O M P O N E N T S : 1. Dorsal root carries sensory fibers from the periphery into the dorsal aspect of the spinal cord; on each dorsal root there is a dorsal root ganglion (sensory) containing the pseudounipolar cell bodies of the nerve fibers that are found in the dorsal root 2. Ventral root arises from the ventral aspect of the spinal cord and car- ries axons of motor neurons from the spinal cord to the periphery; the cell bodies of the axons in the ventral root are located in the ventral or lateral horns of the spinal cord gray matter 3. Spinal nerve is formed by the union of the ventral and dorsal roots; it exits the vertebral column by passing through the intervertebral foramen 4. Dorsal rami innervate the skin of the dorsal surface of the back, neck, zygapophyseal joints, and intrinsic skeletal muscles of the deep back 5. Ventral rami innervate the skin of the anterolateral trunk and limbs, and the skeletal muscles of the anterolateral trunk and limbs (ventral rami form the brachial and lumbosacral plexuses)
  26. T H E A U T O N O M I C N E R V O U S S Y S T E M
  27. T H E A U T O N O M I C N E R V O U S S Y S T E M • The autonomic nervous system (ANS) is concerned with the motor innervation of smooth muscle, cardiac muscle, and glands of the body. Anatomically and functionally, it is composed of 2 motor divisions: sympathetic and parasympathetic. • In both divisions, 2 neurons form an autonomic pathway. 1. Preganglionic neurons have their neuronal cell bodies in the CNS (formed by neuroectoderm); their axons exit in cranial and spinal nerves. 2. Postganglionic neurons have cell bodies in autonomic ganglia in the peripheral nervous system (PNS) (formed by neural crest cells)
  28. T H E S Y M P A T H E T I C N E R V O U S S Y S T E M • The preganglionic cell bodies of the sympathetic nervous system are found in the lateral horn gray matter of spinal cord segments T1–L2 (14 segments). • The postganglionic cell bodies of the sympathetic system are found in one of 2 types of motor ganglia in the PNS: 1. Chain or paravertebral 2. Collateral or prevertebral (found only in abdomen or pelvis)
  29. P A R A S Y M P A T H E T I C N E R V O U S S Y S T E M • The preganglionic cell bodies of the parasympathetic nervous system are found in the CNS in one of 2 places: 1. Gray matter of brain stem associated with cranial nerves III, VII, IX, and X, or 2. Spinal cord gray in sacral segments S2 3, and 4 (pelvic splanchnics) • The postganglionic cell bodies of the parasympathetic nervous system are found in terminal ganglia in the PNS that are usually located near the organ innervated or in the wall of the organ.
  30. P A R A S Y M P A T H E T I C N E R V O U S S Y S T E M • “Rest and Digest” • CN: 1974 • S2-S4 • “Craniosacral” division