Vertebral Column and Spinal Cord

Question 1

Name the various curvatures of the spine.

Answer 1

1. Cervical curve (C2 - T2): convex anteriorly [cervical lordotic curve]
2. Thoracic curve (T2 - T12): concave anteriorly [thoracic kyphotic curve]
3. Lumbar curve (T12 - sacrovertebral angle): convex anteriorly [lumbar lordotic curve]
4. Sacral curve (sacrovertebral articulation - coccyx): concave anteriorly [sacral kyphotic curve]

Extra Notes:
☛ The thoracic and sacral (pelvic) curvatures are concave anteriorly and are referred to as kyphoses (singular: kyphosis). They appear during the fetal period of embryonic development, hence they are also termed primary or developmental curvatures. It is important to note that the sacral curvature differs in males and females; the latter is less pronounced so that the coccyx protrudes less into the pelvic outlet, making it suitable for childbirth.
☛ The cervical and lumbar curvatures are concave posteriorly and convex anteriorly, being referred to as lordoses (singular: lordosis). These curvatures arise as a consequence of extension from the flexed fetal position. Although they begin to appear before birth, they are not apparent until later in infancy when they are accentuated by support of the head and by the adoption of an upright or erect human posture. As a result, they are termed secondary or acquired curvatures.

Question 2

State three functions of the spinal cord.

Answer 2

The spinal cord has three major functions:
1. It acts as a pathway for motor information, which travels down the spinal cord.
2. It serves as a passage for sensory information in the reverse direction.
3. It is a centre for coordinating simple reflexes.

Question 3

Describe the external features of the spinal cord.

Answer 3

☛ The length of the cord is about 45 cm.
☛ It resembles a flattened cylinder, though not uniform in cross section. The spinal segments that contribute to the nerves of the upper limbs (C5 to T1) are enlarged to form the cervical enlargement. Similarly, the segments innervating the lower limbs (L1 to S3) form the lumbar enlargement. [The cervical enlargement gives rise to the brachial plexus, whereas the lumbar enlargement gives rise to the lumbosacral plexus.
☛ The distal end of the spinal cord presents a bundle of spinal nerves that arise from the lumbar enlargement and conus medullaris, known as the cauda equina.
☛ The anterior surface of the spinal cord is marked by a deep anterior median fissure, which contains anterior spinal artery.
☛ The posterior surface is marked by a shallow posterior median sulcus from which a posterior median septum of neuroglial tissue extends into the substance of the cord to a variable extent.

Further Notes:
Why does the cauda equina exist? Remember a spinal nerve exits under its corresponding vertebra (save for cervical nerves). Spinal cord terminated at L1/L2 junction, but segments are still maintained so what do they do? For the remaining lumbar and sacral nerves to exit, they have to move downwards before exiting…hence the cauda equina.

Question 4

State the location and extents of the spinal cord.

Answer 4

LOCATION: Within the vertebral canal

EXTENTS:
The spinal cord begins as a downward extension of medulla oblongata at the level of the foramen magnum/upper border of the first cervical vertebra and ends as conus medullaris at:
a) L1/2 junction in adults
b) L2 at puberty
c) L3 at birth
d) S1 at 6 months of fetal life
e) Coccyx at 3 months of fetal life (remember here, the spinal cord and vertebral column are of equal length)

NB: Vertebral column grows faster than the spinal cord.

Question 5

Outline the arterial blood supply of the spinal cord.

Answer 5

1. Anterior spinal artery: it is formed in the posterior cranial fossa by the union of the right and left anterior spinal arteries which are the branches of the fourth part of the vertebral artery. It runs caudally in the anterior median fissure of the spinal cord and terminates along the filum terminale. It supplies the anterior 2/3 of the spinal cord, covering the following areas:
   i) The anterior horn
   ii)The lateral horn
   iii) The central gray
   iv) The basal part of the posterior horn
   v) Anterior and lateral funiculi
2. Posterior spinal arteries: There are two posterior spinal arteries each arising as a small branch from either the vertebral or posterior inferior cerebellar artery. Each posterior spinal artery runs down on the posterolateral aspect of the cord in the posterolateral sulcus. It supplies the posterior 1/3 of the spinal cord, covering the posterior horns and posterior funiculi.
3. Radicular arteries - The main source of blood to the spinal arteries is from the vertebral arteries (from which the anterior and posterior spinal arteries take origin). However, the blood from the vertebral arteries reaches only up to the cervical segments of the cord. Lower down, the spinal arteries receive blood through radicular arteries that reach the cord along the roots of spinal nerves. These radicular arteries arise from spinal branches of the vertebral, intercostal, lumbar and sacral arteries. These provide the principal blood supply to thoracic, lumbar, sacral and coccygeal spinal segments.
4. [Diagram]

Question 6

What is striking about the spinal meninges?

Answer 6

(1) The spinal dura is a single layer.
(2) The pia mater and arachnoid mater are closer together unlike in the brain (relatively apart in the brain hence large sub-arachnoid spaces) hence forming pia-arachnoid membrane. (Remember: pia and arachnoid mater are called leptomeninges)
(3) The vertebral column grows faster than the spinal cord. The attachment of the pia mater to Cx1 is however retained, and hence forms an elongation that extends up to the conus medullaris, known as the filum terminale.
(4) Since the filum terminale is just a narrow filament, the sub-arachnoid space around it is quite enlarged. This sub-arachnoid space is called lumbar cistern and it contains the cauda equina.
(5) The pia mater has very fine extensions that go through the arachnoid and attach to the dura. These tooth like extensions go from cervical to lumbar region. They are called ligamentum denticulate (denticulate ligaments).

Notes:
The lumbar cistern has a lot of CSF hence a common site for lumbar puncture procedure. Lumbar puncture procedure may be done to collect a sample of CSF or to administer an anaesthetic.

Question 7

Briefly discuss the artery of Adamkiewicz/arteria radicularis magna.

Answer 7

[Many of these radicular arteries are small and end by supplying the nerve roots. A few of them, which are larger, join the spinal arteries and contribute blood to them.] One of the radicular branches, usually from the right or left 11th intercostal artery is very large and is called the arteria radicularis magna (artery of Adamkiewicz). Its position is variable. This artery may be responsible for supplying blood to as much as the lower two-thirds of the spinal cord.

Question 8

What is the arterial vasocorona?

Answer 8

This is the arterial plexus found in the spinal pia mater which sends branches into the substance of the spinal cord.

Question 9

Outline the venous drainage of the spinal cord.

Answer 9

The veins draining the spinal cord are arranged in the form of six longitudinal channels. These are:
a) Two median longitudinal channels, one in the anterior median fissure called the anteromedian channel, and the other in the posteromedian sulcus called the posteromedian channel
b) The paired anterolateral channels, one on either side, posterior to the anterior nerve roots
c) The paired posterolateral channels, one on either side posterior to the posterior nerve roots
These channels are interconnected by a plexus of veins that form a venous vasocorona. The blood from these veins is drained into radicular veins that open into a venous plexus lying between the dura mater and the bony vertebral canal (internal vertebral venous plexus) and through it, into various segmental veins.

Question 10

Discuss anterior spinal artery syndrome. (cause and symptoms)

Answer 10

Anterior spinal artery syndrome: It occurs due to occlusion (thrombosis or compression) of the anterior spinal artery. Since the anterior spinal artery supplies the anterior 2/3 of the spinal cord, the occlusion of this artery will result in:
a) Motor symptoms due to involvement of corticospinal tracts and anterior grey columns (motor paralysis due below level of occlusion or lesion)
b) Sensory symptoms; bilateral loss of pain and temperature sensations due to ischemia of spinothalamic tracts
c) Note that proprioception and vibratory sensation will be retained due to intact dorsal columns

Notes:
1. What are corticospinal tracts? These are the major neuronal pathways providing voluntary motor function. They connect the cortex to the spinal cord to enable movement of distal extremities.

Question 11

What are watershed regions of the spinal cord?

Answer 11

These are areas particularly susceptible to ischemia or insufficient blood supply due to their location at the border of the supply areas of two arteries.

The specific regions: T1, T4, T7-T9, L1

Clinical relevance: this region is vulnerable to watershed infarcts

Notes:
Infarction is tissue death and necrosis due to inadequate blood supply to the affected area.

Question 12

What is Cauda Equina Syndrome? (Hint: cause, symptoms)

Answer 12

This is a syndrome that results from the compression and disruption of the functions of the nerves comprising the cauda equina. The compression is usually as a result of a herniated disc in the lumbar region.
Symptoms:
1. severe back pain
2. pain, numbness or weakness in one or both legs
3. numbness around the anus, loss of bowel or bladder control
4. sexual dysfunction

Question 13

What is Conus Medullaris Syndrome? (Hints: cause, symptoms)

Answer 13

This is a syndrome resulting from compressive damage to the conus medullaris. Symptoms:
1. severe back pain
2. strange or jarring sensations in the back
3. bowel and bladder dysfunction
4. sexual dysfunction
5. weakness, numbness or tingling in the lower limbs

Question 14

What is herpes zoster?

Answer 14

Dorsal nerve root ganglia (and the sensory ganglia of cranial nerves) can be infected with a virus. Vesicles appear on the skin over the area of distribution of the nerve.

Notes:
“Herpes zoster, also known as shingles, is caused by reactivation of varicella-zoster virus (VZV), the same virus that causes varicella (chickenpox). Primary infection with VZV causes varicella. After a person has varicella, the virus remains latent in the dorsal root ganglia.”

Question 15

What is lumbar puncture?

Answer 15

Lumbar puncture is a procedure performed to obtain samples of cerebrospinal fluid (CSF) for various diagnostic and therapeutic purposes. In this procedure, a needle is introduced into the subarachnoid space through the interval between the third and fourth lumbar vertebrae.

Question 16

State the anatomical basis for performing a lumbar puncture.

Answer 16

• presence of the lumbar cistern
• it is done at L3/L4 interval since the spinal cord in adults terminates at L1/L2 junction

Question 17

List the structures through which a needle passes through during the lumbar puncture procedure.

Answer 17

• Skin
• Superficial and deep fascia
• Supraspinous ligament
• Interspinous ligament
• Ligamentum flavum
• Areolar tissue containing the internal vertebral venous plexus
• Dura mater
• Arachnoid mater
• [Diagram]

Question 18

State the purpose of lumbar puncture. (4)

Answer 18

• The pressure of CSF can be estimated roughly by counting the rate at which drops of CSF flow out of the needle or more accurately, by connecting the needle to a manometer.
• Samples of CSF can be collected for examination. The important points to note about CSF are its colour, its cellular content and its chemical composition (especially the protein and sugar content).
• Lumbar puncture may be used for introducing air or radiopaque dyes into the subarachnoid space for certain investigative procedures, e.g. myelography. Drugs may also be injected for treatment.
• Anaesthetic drugs injected into the subarachnoid space act on the lower spinal nerve roots and render the lower part of the body insensitive to pain. This procedure, called spinal anaesthesia, is frequently used for operations on the lower abdomen or on the lower extremities.

NB: Myelography/myelogram: a diagnostic imaging test generally done by a radiologist. It uses a contrast dye and X-rays or computed tomography (CT) to look for problems in the spinal canal.

Question 19

State the region of the nervous system affected in syphilis.

Answer 19

Dorsal column-medial lemniscal pathway

Question 20

Discuss Complete Spinal Cord Transection syndrome.

Answer 20

this refers to a tear within the spinal cord that results in complete loss of function below the level of the tear

Question 21

Discuss Brown-Sequard Syndrome.

Answer 21

This is a neurologic syndrome resulting from hemisection of the spinal cord. It results in weakness or paralysis on one side of the body and a loss of sensation on the opposite side.

Question 22

Cervical vertebra are 7 in number, some are typical, others are atypical, foramen transversaria are present. State the distinguishing features of a typical cervical vertebra.

Answer 22

📝 bifid spinous process
📝 uncinate processes
📝 nearly horizontal articular facets
📝 presence of lateral masses
📝 [Diagram]: a typical cervical vertebra
📝 [Diagram 2]: a typical cervical vertebra

Further notes:
Uncinate process is a bony projection, in the superior surface of the vertebral body, which forms the uncovertebral joint with the body of the cervical vertebra above and also forms the medial margin of the intervertebral foramen.

Question 23

State 3 distinguishing features of C1 vertebra.

Answer 23

✈ no body
✈ 2 arches; anterior and posterior
✈ paired lateral masses (serve as a body, sustain weight of the cranium)
✈ [Image 1] [Image 2]

Further notes:
At the posterior arch near superior articular surface of lateral mass, there’s a groove for vertebral artery.

Question 24

State the distinguishing feature of C2 vertebra.

Answer 24

Presence of dens/odontoid process

Question 25

State the distinguishing features of C7 vertebra (aka vertebra prominens).

Answer 25

✈ has a long spinous process (palpable in the midline of the neck
✈ has transitional inferior facets
✈ [Diagram 1] [Diagram 2]

Question 26

State the distinguishing features of typical thoracic vertebrae.

Answer 26

✈ coronal facets (allow rotational motion)
✈ facets on the body (for costo-vertebral joint)
✈ facets on the transverse process (costo-transverse joint)
✈ [Diagram]: typical thoracic vertebra

Question 27

What is one feature of T12 that distinguishes it from the rest of the thoracic vertebrae.

Answer 27

The inferior facets of T12 are sagittal whereas the rest of the thoracic vertebrae have coronal facets.
[Diagram 1: T12]
[Diagram 2: typical thoracic vertebra]

Question 28

State the distinguishing features of typical lumbar vertebrae.

Answer 28

➤ they have sagittal facets (to allow flexion)
➤ they have oblong spinous processes
➤ presence of mamillary tubercles
➤ [Diagram 1] [Diagram 2]

Question 29

All the spinal nerves exit out of the vertebral canal through an intervertebral foramen except which ones? Where do they exit?

Answer 29

1. C1 spinal nerve emerges above the posterior arch of the atlas.
2. C2 emerges between the posterior arch of atlas and axis vertebra.
3. S5 and Cx1 emerge through lower end of the sacral canal. Other sacral nerves have separate sacral foramina for each ramus.

Question 30

Name 6 spinal ligaments that confer stability to the spine.

Answer 30

1. anterior longitudinal ligament
2. posterior longitudinal ligament
3. interspinal ligament
4. ligamentum flavum
5. supraspinous ligament
6. nuchal ligament (ligamentum nuchae)
7. [Diagram 1] [Diagram 2] [Diagram 3]

Further notes:
The nuchal ligament is a ligament at the back of the neck that is continuous with the supraspinous ligament. The nuchal ligament extends from the external occipital protuberance on the skull and median nuchal line to the spinous process of the seventh cervical vertebra in the lower part of the neck.

Question 31

What type of joint is the intervertebral joint.

Answer 31

fibrocartilaginous symphysis

Question 32

Briefly explain Romberg’s test. Give examples of lesions that may result in a positive Rhomberg’s sign.

Answer 32

✓ This is a neurological test used to evaluate balance and proprioception.
✓ The test involves the patient standing with their feet together and arms at their side or crossed in front of them. The patient is first observed with their eyes open, and then with their eyes closed.
✓ A positive Romberg sign is observed when a patient, who is able to maintain balance with their eyes open, loses balance when their eyes are closed.
✓ This suggests that the patient is relying on vision to maintain balance due to a deficit in proprioception.
✓ Examples of conditions that can cause a positive Romberg sign include: (1) posterior cord syndrome (Posterior spinal artery infarction), (2) hemisection of the spinal cord (Brown Sequard syndrome), (3) cerebellar lesions
✓ [Video]: patient with positive Romberg sign

Question 33

List the differences between Conus Medullaris syndrome and Cauda Equina syndrome.

Answer 33

CMS: conus medullaris syndrome
CES: cauda equina syndrome
(a) Vertebral level: CMS lesion occurs at L1-L2 level, whereas CES lesion occurs between L2 and the sacrum.
(b) Spinal level: CMS lesion affects sacral cord segment and roots; CES lesion affects lumbosacral nerve roots
(c) Presentation: CMS is sudden and bilateral; CES is gradual and unilateral
(d) Radicular pain: CMS - less severe; CES - more severe
(e) Low back pain: CMS - more; CES - less
(f) Motor strength: CMS - symmetrical, less marked hyperreflexic distal paresis of lower limb, fasciulation; CES - more marked asymmetric areflexic paraplegia, atrophy more common
(g) Reflexes: CMS - ankle jerks affected; CES - both knee and ankle jerks affected
(h) Sensory: CMS - localized numbness to perianal area, symmetrical and bilateral; CES - localized numbness at saddle area, asymmetrical, unilateral
(i) Sphincter dysfunction: CMS - early urine and fecal incontinence; CES - tend to present late
(j) Impotence: CMS - frequent; CES - less frequent

Question 34

Atlanto-occipital joint
(a) type
(b) articulating surfaces
(c) arterial supply
(d) nerve supply
(e) movements

Answer 34

(a) type: synovial joint of ellipsoidal variety
(b) articulating surfaces:
Above: convex articular surface of the occipital condyles
Below: concave superior articular facets of the atlas
(c) arterial supply: vertebral artery
(d) nerve supply: first cervical nerve
(e) movements: flexion and extension [nodding or yes movements] and lateral flexion [slight]

Question 35

Name the muscles that:
(a) flex the atlanto-occipital joint
(b) extend the atlanto-occipital joint
(c) flex the atlanto-occipital joint laterally

Answer 35

(a) flexion: longus capitis, rectus capitis anterior
(b) extension: ☑ rectus capitis posterior major and minor, ☑ semispinalis capitis, ☑ splenius capitis, ☑ upper part of the trapezius
(c) lateral flexion: rectus capitis lateralis

Question 36

State three ligaments closely associated with the atlanto-occipital joint.

Answer 36

(a) fibrous capsule
(b) anterior atlanto-occipital membrane
(c) posterior atlanto-occipital membrane

Question 37

The atlantoaxial joint complex consists of three well separated joints, which are:

Answer 37

a median atlantoaxial joint and two lateral atlantoaxial joints.

☯️ All these joints function as one unit to produce the movement of rotation of atlas with head around the vertical axis.

Question 38

Regarding the median atlantoaxial joint, state the type of joint and articular surfaces.

Answer 38

Type of joint: a synovial joint of pivot variety
Articular surfaces: odontoid process of axis, anterior arch and transverse ligament of axis.

Further notes:
☯️ There are two articulations—anterior and posterior—with separate synovial cavities.
☯️ Anteriorly, the vertically oriented oval facet on the anterior surface of dens articulates with a similar facet on the posterior surface of the anterior arch of the atlas.
☯️ Posteriorly, the cartilaginous anterior surface of transverse ligament of atlas articulates with the horizontally oriented ovoid facet on the posterior surface of the base of the dens.

Question 39

State the ligaments of the median atlantoaxial joint.

Answer 39

1. Fibrous capsule
2. Transverse ligament - attached on each side to the medial surface of the lateral mass of the atlas. In the median plane its fibres are prolonged: (a) upwards to the basiocciput and (b) downwards to the body of the axis, thus forming the cruciform ligament of the atlas. The transverse ligament prevents backward dislocation of the dens.
3. Apical ligament of the dens: Extends from tip of odontoid process to the upper surface of the basilar part of the occipital bone near foramen magnum [Remember: It’s also a remnant of the notochord]
4. Alar ligaments (one on each side): Extend from the upper part of the dens (on side of the tip) to the tubercle on the medial aspect of the occipital condyle. These ligaments are very strong and check excessive rotation and flexion of head. They are, therefore, called check ligaments.
5. Membrana tectoria (upward continuation of the posterior longitudinal ligament): lies posterior to the transverse ligament of the atlas. Inferiorly, it is attached to the posterior surface of the body of the axis and superiorly to the upper surface of the basilar part of the occipital bone above the attachment of upper band of the cruciform ligament.

Question 40

Regarding the lateral atlantoaxial joints, state:
1. Type
2. Articular surfaces

Answer 40

1. Type: Synovial joint of plane variety.
2. Articular surfaces:
   Above: Inferior facet of the lateral mass of the atlas. It is flat.
   Below: Superior articular facet of axis. It is also flat, thus superior and inferior articular facets are reciprocally curved.
   Capsules: It is attached to the margin of articular surfaces. It is supported by anterior longitudinal ligament and ligamentum flavum.

Question 41

State and explain the movements of the atlantoaxial joint complex.

Answer 41

Rotation of axis: These are simultaneous at all the three atlantoaxial joints and consist almost exclusively of rotation of axis. In fact, the osseoligamentous ring of atlas supporting the atlas rotates around the central pivot formed by the odontoid process. The rotation is limited mainly by alar ligaments. Rotatory movements of atlas with head, around vertical axis are also called No movements.

Question 42

Why does death occur during executive hanging?

Answer 42

Death occurs due to posterior dislocation of odontoid process (following rupture of transverse ligament of atlas) crushing the lower part of medulla oblongata which houses vital centres and adjoining part of the spinal cord.