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					The Spinal Cord

    Structure   of the spinal cord
    Tracts   of the spinal cord
    Spinal   cord syndromes

                         Nabeel Kouka, MD, DO, MBA
                               www.brain101.info
               Spinal Cord



- Comparable to
    Input-Output (IO) System of the Computer

- Spinal Nerve (C8, T12, L5, S5, Cx1)

- Segmental Structure of Neural Tube Origin
Spinal segment
  C8, T12, L5, S5, Cx1

Anterior (Ventral) Root
Posterior (Dorsal) Root
  Dorsal Root (Spinal) Ganglion
Root - Rootlets
Conus Medullaris (L1-2)
Cauda Equina
Anterior median fissure
Anterolateral fissure
                                       Posterior
                                         median sulcus
                                       Posterolateral
                                         sulcus
                                       Posterior
                                         intermediate
                                         sulcus
                                        Fasciculus
                                          cuneatus
                                        Fasciculus
                                          gracilis

Posterior surface of the spinal cord
Spinal Cord                             Meninges



Periosteum of Vertebra
 - Epidural Space ----------------- epidural anesthesia
Dura Mater Spinalis
Arachnoid Membrane
 - Subarachnoid Space -------- Lumbar Puncture
                              Spinal Anesthesia
Pia Mater Spinalis
 - Denticulate Ligament --------- Cordotomy
 - Filum Terminale
                                    Meninges of
                                    the spinal cord
                                      • Dura mater
                                      • Arachnoid membrane
                                      • Pia mater




Denticulate ligament
- specialization of the pia mater
- landmark for cordotomy
Meninges of the spinal cord
Meninges of the spinal cord
Lumbar Puncture – lumbar (terminal) cistern
    Spinal Cord                                Vascular Supply



Arterial Supply
 - Spinal Arteries
        Anterior (1) & Posterior (2) Spinal Artery
         from Vertebral artery
 - Radicular Arteries ----- Segmental arteries
         from Vertebral, Ascending Cervical, Intercostal and
               Lumbar Artery
Venous Drainage
  - Longitudinal & Radicular Veins
      to Intervertebral veins ---- to Internal Vertebral Venous Plexus
      to external vertebral venous plexus ---- to segmental veins
                         5. Adamkiwicz artery


anterior spinal artery      segmental arteries
Spinal Cord   External Figure
Spinal Cord                             External Figure



Conus Medullaris (L1-2)
Spinomedullary Junction
 - Foramen Magnum, Pyramidal decussation, C1 ventral root
Enlargements
 - Cervical (C4-T1) & Lumbosacral (L1-L4)
Longitudinal Fissures
 - anterior median fissure
 - anterolateral fissure
 - posterior median sulcus
 - posterolateral sulcus
cervical enlargement (C8)   thoracic cord (T8)




lumbar enlargement (L3)      sacral cord (S1)
• Cervical level
 - Wide flat cord, lots of white matter,
   ventral horn enlargements.

• Lumbar level
   - Round cord, ventral horn enlargements.

• Sacral level
   - Small round cord, lateral Horn.

• Tthoracic level
   - Notice the pointed tips which stick out
     between the small dorsal and ventral horns.
     This extra cell column is called the
     intermediate horn (AKA: Intermediolateral
     Cell Column). It is the source of all of the
     sympathetics in the body & occurs only in
     the Thoracic sections T 1 - L 2
Spinal Cord                             Internal Structure



White Matter
    Anterior Funiculus (Anterior White Column)
    Posterior Funiculus (Posterior White Column)
        Fasciculus Gracilis & Fasciculus Cuneatus
    Lateral Funiculus (Lateral White Column)
Gray Matter
    Anterior Horn ------------ ---   motor
    Posterior Horn --------------    sensory
    Lateral Horn -----------------   autonomic (sympathetic)
    Gray Commissure --------         anterior and posterior
1. posterior horn
                          9. anterior median
2. anterior horn                fissure

3. intermediate zone     10. posterior median
                               sulcus
  (intermediate gray)
                         11. anterolateral
4. lateral horn
                               sulcus
5. posterior funiculus
                         12. posterolateral
6. anterior funiculus          sulcus
                         13. Posterior
7. lateral funiculus
                               intermediate
8. Lissauer's tract            sulcus
Spinal Cord                          Internal Structure


       Principles of Cord Organization
1) Longitudinal Arrangement
    Fibers (White Matter) ------------- White Column
    Cell Groups (Gray Matter) ------- Gray Column

2) Transverse Arrangement
   Afferent & Efferent Fibers
   Crossing (Commissural and Decussating) Fibers
3) Somatotopical Arrangement
Columnar arrangement   Somatotopical arrangement
Lamina of Rexed
Lamina of Rexed

   Lamina I Posteromarginal Nucleus
   Lamina II Substantia Gelatinosa of Rolando
   Lamina III
   Lamina IV, V, VI ----- Nucleus Proprius
   Lamina VII
         - Intermediate Gray
         - Intermediolateral cell column (ILM)
         - Clarke’s column (Nucleus dorsalis)
         - Intermediomedial cell column (IMM)
   Lamina VIII
   Lamina IX ---------- Anterior Horn (Motor) Cell
   Lamina X ----------- Gray Commissure
Lamina I


• AKA: lamina marginalis
  or the layer of Waldeyer

• Receives incoming dorsal root fibers
  and collateral branches as well

• Larger neurons contribute axons
  to Contralateral Spinothalamic Tract
Lamina II
• AKA: Substantia Gelatinosa

• Involved in Pain interpretation
• Receives incoming input from dorsal
  root axons & descending input from
  reticular formation of the medulla

• Efferent axons travel up & down
  several segments to make contact
  with other areas of the dorsal horn
Lamina III

• Contains larger, less densely packed
  cells than lamina II

• Receives primary afferents from
  dorsal root fibers
• Neurons considered as a part of
  nucleus proprius
Lamina IV
• Contains a variety of cell types that have
  more myelin than any other lamina

• Some tract cells originate here, axons cross
  the midline and enter the contralateral
  Spinothalamic Tract, also sends contacts to
  layers II and III

• Receives afferents from dorsal roots via
  the dorsal funiculus

• At rostral end of spinal cord, laminas I-IV
  become continuous with the spinal
  trigeminal nucleus
Lamina V - VI

  • Origination of tract cells, similar
    to lamina IV, these tracts cells are
    also known as the Nucleus Proprius
    (e.g. spinal thalamic tract or
    anterolateral system; pain and
    temperature, some tactile)

  • Receives afferent input from
    dorsal roots and descending fibers,
    most importantly Corticospinal
                      Lamina V - VI
                                                        C7



reticular formation ---------------->




Laterally, gray matter at base of dorsal horn mixes with
white matter from lateral funiculus, this region is called
reticular formation. It is noticeable in the cervical region
Lamina VII

• The largest region, occupies most of
  ventral horn &intermediate zone

• Projects long axons that connect to other
  gray matter segments of the cord

• Some columns do not fit into the lamina
  scheme, and have individual designations:
       a. Nucleus dorsalis (Clarke)
       b. Intermediolateral cell column
       c. Intermediomedial cell column
       d. Sacral autonomic nucleus
                         Lamina VII

• Nucleus dorsalis of Clark
                                      T5
  AKA nucleus thoracicus
  is located medial & ventral
  to the dorsal horn in T1-L3

• Composed of large neurons
  & axons that form the
  dorsal spinocerebellar tract
  on the ipsilateral side
                               Lamina VII

• Intermediolateral cell column
  is located at the lateral portion         T5
  of the intermediate zone.

• Responsible for the formation
  of the lateral horn in T1 - L2

• Consists of cell bodies of
  sympathetic preganglionic
  neurons
                              Lamina VII


• Intermediomedial cell column             T5
  is located lateral to lamina X.
  Not seen in all cord sections.

• Receives primary afferent
  fibers from dorsal root and
  has been implicated in
  visceral reflexes
                               Lamina VII

                                            S2

• Sacral autonomic nucleus
  is located in the lateral part of
  lamina VII in S2-S4 segments

• Consists of preganglionic para-
  sympathetic neurons
Lamina VIII

 • Located on the medial aspect of
   the ventral horn

 • Efferent projections both ipsilaterally
   and contralaterally to the same and
   nearby segmental levels to lamina
   VII & IX

 • Site of termination for descending
   fibers, including the vestibulospinal
   and reticulospinal tracts
Lamina IX
• Consists of columns of neurons
  embedded in either lamina VII or VIII
• Cells include alpha and gamma motor
  neurons, which axons exit via the
  ventral roots and innervate striated
  muscle. Smaller neurons contribute
  axons to the ventral fasciculus proprius
• Four columns of motor neurons can
  be identified within this lamina;
  ventromedial, ventrolateral, dorsolateral
  & central each has characteristic
  dendritic features
Lamina IX


 Ventral gray columns in lamina IX
  have somatotopic arrangement:
   - Medial areas innervate the
     axial musculature
   - Lateral areas innervate the
     limbs muscles
                    PHRENIC NUCLEUS

The phrenic nucleus is located in the ventromedial area of the
ventral horn in C2-C5 segments. It receives bilateral innervation
from the solitary nucleus of the medullary region, via solitary tract.
This nucleus is responsible for the innervation of the diaphragm



             SPINAL ACCESSORY NUCLEUS

The spinal accessory nucleus (cranial nerve XI) is located in the
lateral area of vental horn in C1-C5 segments. Corticospinal tract
innervates this nucleus bilaterally. This nucleus is also responsible
for the innervation of the trapezius & sternocleidomastoid muscles
(ipsilaterally)
                               Lamina IX

     Nucleus of Onuf                       S2

• Located ventrolaterally in
  S1-S2 spinal segments

• Supplies muscles of the
  pelvic floor, including striated
  muscle sphincters for urinary
  and fecal continence
Lamina X

• Surrounds the central canal, and
  includes the ventral gray commissure

• Contains relatively small neurons,
  radial neuroglia cells & decussating
  axons

• Some dorsal root afferents terminate
  here
                Fasiculus Proprius




• Ascending and descending association fiber systems of the
  spinal cord which lie deep in the anterior, lateral & posterior
  funiculi adjacent to the gray matter.
• Fasciculi proprii aka Flechsig's fasciculi or Ground bundles
  consist of: anterior, lateralis & intersegmental fasciculi
                                Dorsal Roots

• Each dorsal root divides
  into 6 - 8 rootlets
• Each rootlet can be divided into
  lateral & medial division
• Lateral division carries
  information related to pain
  & temperature
• Medial division carries
  information related to tactile
  discrimination & vibration
                           Dorsal Roots


• Lateral division axons enter
  dorsolateral tract of Lissauer,
  and then divide into ascending
  & descending branches, each
  terminate in the dorsal horn
• Most terminate at same
  level & some fibers may
  travel up or down the cord
  up to four levels
                             Dorsal Roots

• Medial division axons enter the
  white matter & then divide into
  ascending & descending branches

• Descending branches are
  organized into two bundles,
  the Septomarginalis Fasiculus
  and the Interfascicular Fasiculus

• All descending branches terminate
  in the dorsal horn
                         Dorsal Roots



• Ascending branches of the
 medial division enter the
 dorsal funiculus & terminate
 in gracile & cuneate nuclei
 in the medulla
                               Ventral Horn

• Lamina IX contains two types
 of motor neurons, alpha and
 gamma
• Alpha motor neurons innervate
  extrafusal fibers of striated
  skeletal muscles
• Gamma motor neurons innervate
  intrafusal fibers of neuromuscular
  spindles
• Both types receive inputs from
  interneurons, including the
  inhibitory Renshaw cell
Spinal Cord   Tracts
Tracts of the Spinal Cord


             1.    Fasciculus Gracilis
             2.    Fasciculus Cuneatus
             3.    Tractus spinocerebellaris dorsalis
             4.    Tractus corticospinalis lateralis
 16          5.    Tractus spinothalamicus lateralis
             6.    Tractus spinocerebellaris ventralis
             7.    Tractus rubrospinalis
             8.    Tractus spinotectalis
             9.    Tractus corticospinalis anterior
             10.   Tractus olivospinalis
             11.   Tractus spinoolivaris
             12.   Tractus tectospinalis
             13.   Tractus reticulospinalis
             14.   Tractus vestibulospinalis
             15.   Tractus spinothalamicus anterior
             16.   Raphe-spinal & Hypothalamospinal fibers
   Spinal Cord                              Tracts


                 Ascending Tracts

Modality: Touch, Pain, Temperature, Kinesthesia
Receptor: Exteroceptor, Interoceptor, Proprioceptor
Primary Neuron: Dorsal Root Ganglion (Spinal Ganglion)
Secondary Neuron: Spinal Cord or Brain Stem
Tertiary Neuron: Thalamus (Ventrobasal Nuclear Complex)
Termination: Cerebral Cortex, Cerebellar Cortex, or
              Brain Stem
Spinal Cord                           Tracts


              Ascending Tracts

Posterior White Column-Medial Lemniscal Pathway
Spinothalamic Tract
Spinoreticular or Spinoreticulothalamic Tract
Spinocerebellar Tract
Spinomedullothalamic Tract
Cervicothalamic or Spinocervicothalamic Tract
Spino-olivary Tract
Spinotectal Tract
   Spinal Cord                               Ascending Tracts

   Posterior White Column-Medial Lemniscal Pathway

 Modality: Discriminative Touch Sensation (include Vibration) and
           Conscious Proprioception (Position Sensation, Kinesthesia)
 Receptor: Most receptors except free nerve endings

Ist Neuron: Dorsal Root Ganglion (Spinal Ganglion)
              Posterior Root - Posterior White Column
2nd Neuron: Dorsal Column Nuclei (Nucleus Gracilis et Cuneatus)
              Internal Arcuate Fiber - Lemniscal Decussation
              - Medial Lemniscus
3rd Neuron: Thalamus (VPLc)
              Internal Capsule ----- Corona Radiata
Termination: Primary Somesthetic Area (S I)
               medial lemniscus

               lemniscal decussation

               internal arcuate fiber

               posterior white column

               posterior root




Posterior White Column -
Medial Lemniscal Pathway

- ipsilateral loss of discriminative touch
    sensation and conscious proprioception
    below the level of lesion
Spinal Cord                           Ascending Tracts


               Spinothalamic Tract

   Modality: Pain & Temperature Sensation, Light Touch
   Receptor: Free Nerve Ending

 Ist Neuron: Dorsal Root Ganglion (Spinal Ganglion)
               Posterior Root
 2nd Neuron: Dorsal Horn (Lamina IV, V, VI)
               Spinothalamic Tract - (Spinal Lemniscus)
 3rd Neuron: Thalamus (VPLc, CL & POm)
               Internal Capsule ----- Corona Radiata
 Termination: Primary Somesthetic Area (S I) &
              Diffuse Widespread Cortical Region
                      spinothalamic
                      tract



decussation
                      anterior white
                      commissure


                      posterior root




     Spinothalamic Tract


- contralateral loss of pain and temperature
    sensation below the level of lesion
  NeoSTT             PaleoSTT
Primary Motor      Widespread
 Area (M I)         cortical region

VPLc (ventrobasal CL (intralaminar
                                      thalamus
 nuclear complex) thalamic nuclei)

(spinal lemniscus) reticulothalamic
                     pathways

spinothalamic      spinoreticular
 tract              tract             reticular
                                      formation



 Spinothalamic Tract
 & Spinoreticular Tract
Comparison of Fast and Slow Pain ------ Spinothalamic Tract



   Fast Pain                  Slow Pain

   Sharp, pricking            Dull, burning
   Group III (A) fiber       Group IV (C) fiber
   Short latency              Slower onset
   Well localized             Diffuse
   Short duration             Long duration
   Less emotional             Emotional, autonomic response
   Not blocked by morphine    Blocked by morphine
   Neospinothalamic Tract     Paleospinothalamic Tract
Spinal Cord                         Ascending Tracts

            Spinocerebellar Tract
    Modality: Unconscious Proprioception
    Receptor: Muscle spindle, Golgi tendon organ

Ist Neuron: Dorsal Root Ganglion (Spinal Ganglion)
                 Posterior Root , [Posterior Column]
2nd Neuron: 1. Clarke’s column (Lamina VII)
                 Posterior Spinocerebellar Tract
              2. Accessory Cuneate Nucleus
                 Cuneocerebellar Tract
              3. Posterior Horn
                 Anterior Spinocerebellar Tract
Termination: Cerebellar Cortex
Anterior SCbllT    Posterior SCbllT
                                      Inferior cerebellar
                                        peduncle
(superior          Inferior
  cerebellar        cerebellar
  peduncle)          peduncle

anterior           cuneocerebellar    posterior
 spinocerebellar    tract              spinocerebellar
 tract              (upper body)       tract

anterior white     posterior          Clarke’s
 commissure         white column       column

posterior root     posterior root     posterior
                                       white column


  Spinocerebellar Tract               posterior root
Spinocerebellar Tract
Spinal Cord                             Descending Tracts
                Corticospinal Tract
Origin: Cerebral Cortex
          Brodmann Area 4 (Primary Motor Area, M I)
          Brodmann Area 6 (Premotor Area, PM )
          Brodmann Area 3,1,2 (Primary Somesthetic Area, S I)
          Brodmann Area 5 (Anterior Portion of Sup. Parietal Lobule)
       Corona Radiata
       lnternal Capsule, Posterior Limb
       Crus Cerebri, Middle Portion
       Longitudinal Pontine Fiber
       Pyramid - pyramidal decussation
       Corticospinal Tracts:
                         - Lateral (crossed) - 85%
                         - Anterior (Not crossed) - 15%
Termination: Spinal Gray (Rexed IV-IX)
 Corona Radiata
 lnternal Capsule, Posterior Limb
 Crus Cerebri, Middle Portion
 Longitudinal Pontine Fiber
 Pyramid                                   CR
 Pyramidal Decussation
 Corticospinal Tract
                                           IC
   - Lateral and Anterior

                                           LPF


 Corticospinal Tract
                                    Pyr
                                                 LCST
                                          PD
- ipsilateral UMN syndrome                ACST
       at the level of lesion
Spinal Cord                    Descending Tracts


        Descending Tracts from Brain Stem
     Dorsolateral (Motor) Pathway
        Rubrospinal Tract
     Ventromedial (Motor) Pathway
        Tectospinal Tract
        Vestibulospinal Tract
        MLF (Medial Longitudinal Fasciculus)
         - interstitiospinal tract
     Sensory Modulation pathways
        Raphespinal & Cerulospinal Pathways
     Descending Autonomic Pathways
Spinal Cord
Tracts




              ventromedial   dorsolateral
 Descending    pathway        pathway
 Tracts
 from
 Brain Stem
                  SOMATIC MOTOR SYSTEM


upper motor neuron
       UMN                                         Brain Stem
                                                   Descending
                                                    Pathway

 VOLUNTARY             Final Common Pathway            Rubrospinal Tract
  CONTROL                                              Tectospinal Tract
                         lower motor neuron            Vestibulospinal Tract
                                                       MLF
                              LMN                      Reticulospinal Tract
     Pyramidal Tract                             AUTOMATIC CONTROL



                                              REFLEX
                           EFFECTORS
                          skeletal muscle
Spinal Cord                                       Syndrome



Location of
Symptoms in
Spinal Disease




                 ipsilateral to lesion   contralateral to lesion
Upper Motor Neuron (UMN) vs. Lower Motor Neuron (LMN) Syndrome


                        UMN syndrome            LMN Syndrome

Type of Paralysis      Spastic Paresis          Flaccid Paralysis

Atrophy                No (Disuse) Atrophy      Severe Atrophy

Deep Tendon Reflex     Increase                 Absent DTR

Pathological Reflex    Positive Babinski Sign   Absent

Superficial Reflex     Absent                   Present

Fasciculation and      Absent                   Could be
Fibrillation                                     Present
Spinal Cord                                    Syndrome



        Predominantly Motor Syndromes

      • Poliomyelitis (Infantile Paralysis)
         - viral infection of lower motor neuron
         - LMN syndrome at the level of lesion


      • Amyotrophic Lateral Sclerosis (ALS)
         - combined LMN and UMN lesion
         - LMN syndrome at the level of lesion
         - UMN syndrome below the level of lesion
         - Lou Gehrig’s disease
    Spinal Cord                                    Syndrome




1. corticospinal                                    2. lower motor
   tract                                               neuron (LMN)



                   Amyotrophic Lateral Sclerosis
  Spinal Cord
   Syndrome



  Amyotrophic
Lateral Sclerosis
     (ALS)


 Lou Gherig’s
   Disease
                    Lou "The Iron Horse" Gehrig (1903-41)
                    3.40, 2131(1925-39), 23 GSH, 147 RBI avg.
  Spinal Cord
   Syndrome



  Amyotrophic
Lateral Sclerosis
     (ALS)


 Lou Gherig’s
   Disease                 Stephen Haking (1946- )
                    British Physicist, A Brief History of Time
Spinal Cord                                    Syndrome



         Predominantly Sensory Syndromes
 • Herpes Zoster
    - inflammatory reactions of spinal ganglion
    - severe pain on the dermatomes of affected ganglion
 • Tabes Dorsalis
    - common variety of neurosyphilis
    - posterior column and spinal posterior root lesion
    - loss of discriminative touch sensation and conscious
        proprioception below the level of lesion
    - posterior column ataxia
    - lancinating pain (a stabbing or piercing sensation)
    - loss of deep tendon reflex (DTR)
Herpes Zoster (Shingles)
                    • varicella-zoster virus
                       reactivation from
                       the dorsal root ganglia
                    • unilateral vesicular
                       eruption within
                       a dermatome
                    • T3 to L3 dermatome
                       lesions are frequent
                    • zoster ophtahalmicus
                       (ophthalmic division
                        of trigeminal n., V1)
                    • Ramsey-Hunt syndrome
                       (sensory br. of VII)
                    • acyclovir, antiviral agent
Spinal Cord                                   Syndrome



        Sub-Acute Combined Degeneration
          (Combined System Disease)

 Lesion
   - posterior white column
   - corticospinal tract (UMN)

 Symptom
   - loss of discriminative touch sensation and conscious
      proprioception below the level of lesion
   - ipsilateral UMN syndrome below the level of lesion
    Spinal Cord                               Syndrome




1. corticospinal                               2. posterior
   tract                                          white column



                   Sub-Acute Combined Degeneration
Spinal Cord                                      Syndrome



          Syringomyelia, Hematomyelia

 Lesion
    - central canal of spinal cord
    - gradually extended to peripheral part of the cord

 Symptom
    - initial symptom is bilateral loss of pain
          (compression of anterior white commissure)
    - variety of symptoms appear
         according to the lesion extended from central canal
Spinal Cord                                Syndrome




              Syringomyelia - Initial Symptoms
Spinal Cord                                      Syndrome



          Brown-Sequard syndrome
              (spinal cord hemisection)
Major Symptoms
   1. ipsilateral UMN syndrome below the level of lesion
   2. ipsilateral LMN syndrome at the level of lesion
   3. ipsilateral loss of discriminative touch sensation and
       conscious proprioception below the level of lesion
       (posterior white column lesion)
   4. contralateral loss of pain and temperature sensation
       below the level of lesion (spinothalamic tract lesion)
Spinal Cord                                                    Syndrome


                                 3'            3
                   1                                       1



                                      3'   3
                       1'                              1
              4'                                           4
                            2'                     2




         5'                                                    5
              4                                            1
                       1'         3            3




Brown-Sequard Syndrome (Spinal Cord Hemisection)

				
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