7 - Spinal Cord Anatomy Flashcards
basic definitions of spinal cord anatomy
- Spinal Column, Spine or Vertebral Column is the collection of bones that form the backbone.
- Vertebrae: bones of the spinal column.
- Spinal Cord: the portion of the central nervous system enclosed by the spine that connects the brain to all parts of the body.
- Spinal Nerve: one of the 31 pairs of nerves that arise from the spinal cord that carry motor, sensory, and autonomic fibers.
-
“Myelo-”: pertaining to the spinal cord
– e.g.myelopathy is a disease of the spinal cord -
“Radiculo-”: pertaining to an individual
spinal nerve
– e.g.radiculopathy is a disease of a spinal nerve
Vertebral Column
- Protective container for spinal cord
- 33 bones (vertebrae) comprise the spine or
vertebral column - Vertebrae components include the vertebral
body, pedicles, laminae, transverse and spinous processes. - Openings include the spinal canal and the
neural foramen
Vertebral Components
- Body: major weight-bearing component
- Laminae: posterior bones of vertebrae that make up foramen
- Transverse Process: bilateral projections from vertebrae
- Pedicles: connects the vertebral body to the spinous and transverse processes
- Spinous Process: posterior prominence on vertebrae
- Pars interarticularis: the segment of bone between facets
Superior openings of the spinal canal
Inferior openings of the spinal canal
openings in the spine
Cervical Spine
- 7 cervical vertebrae
- 8 cervical spinal nerves
- C-1 (Atlas) - securely affixed to the occiput
- C-2 (Axis) - odontoid process (dens)
- C-7 - prominent spinous process
Thoracic Spine
- Larger and stronger than cervical spine
- 12 thoracic vertebrae
- 1 st rib articulates with T-1
- Next nine ribs attach to the inferior and superior portion of adjacent vertebral bodies
Lumbar Spine
- 5 vertebrae
- Largest and thickest vertebral bodies and intervertebral disks
Sacral Spine
- 5 fused vertebrae
- Form posterior plate of pelvis
spinal nerve organization
31 pairs of
Spinal Nerves
8 Cervical (C1-C8)
12 Thoracic (T1-T12)
5 Lumbar (L1-L5)
5 Sacral (S1-S5)
1 Coccygeal (Co1)
distal end of the spinal cord
- Conus Medularis: distal tapering of spinal cord
- Filum Terminale a fibrous band that extends from the conus medullaris to the periosteum of the coccyx
-
Cauda Equina: (aka – horse
tail) extension of ventral and dorsal roots
tethered cord
Spinal Meninges
- Dura Mater
- Arachnoid
- Pia Mater
Denticulate
ligaments
- lateral projections of the pia mater
forming triangular-shaped ligament - There are usually 21 denticulate ligament pairs, with the uppermost pair occurring just below the foramen magnum, and the lowest pair occurring between spinal nerve roots of T12 and L1
Spinal Cord development, Dural sac, lumbar puncture
Spinal Cord
* Adults: the foramen magnum to L1
* Infants: ends at L3 and moves up as they grow older
Dural Sac
* Adults: extend to S2
* Infants: often ends at S3 in children
Lumbar puncture
* Adult: below L1
* Children: below L3
Lumbar puncture technique
Palpate the L4 spinous process (should be at the level of iliac crests)
Identify the L2-3, L3-4 and L4-5 interspaces
organization/general function of the spinal cord (gray/white, afferent/efferent, dorsal/ventral, somatic/autonomic/sensory) (diagrams)
Posterior gray horns:
Somatic and Visceral Sensory nuclei.
Anterior gray horns:
Somatic Motor control.
Lateral gray horns:
Visceral Motor neurons.
Gray commissures
Axons of interneurons crossing and unmyelinated axons.
Dermatomes & Myotomes
- Dermatome – an area of skin innervated by a single posterior root
- Myotome – a group of muscles innervated by a single anterior root
The Vertebral Arteries
Branches of the vertebral arteries are-the posterior spinal artery, the anterior spinal artery, and the posterior inferior cerebellar arter.
Vascular supply - arterial
- One anterior spinal artery ventral cord
- Two posterior spinal artery dorsal cord
Vascular supply - arterial
Six to ten segmental arteries (radicular arteries) unite with the anterior and posterior spinal arteries to form the spinal arterial plexus
Vascular supply - arterial
- Prominent artery of Ademkiewicz –direct branch of the aorta into the spinal arterial plexus
- Can see occlusion or transections
Nerve Root Anatomy
SCI Neurological classification
- Neurological levels
- American Spinal Injury Association (ASIA) impairment scale (A through E)
- Clinical syndromes (incomplete injuries only)
- Examples:
– T4 ASIA A
– C4 ASIA D central cord
Neurological levels
- Broadly divided into cervical (C), thoracic (T), lumbar (L) and sacral (S).
- Neurologic level is the most caudal level with normal motor and sensory function
- Determined by key dermatomes (sensation) and myotomes (motor)
Dermatomes (diagram)
Myotomes
Monitor Neurologic Status
Neurologic examination at 72 hours is
the most accurate predictor of functional
outcome.
-
Incomplete - based on detection of sacral
sparing, either motor or sensory. - Complete - if no sacral sparing.
- Neurologic level of injury (NLI) - needs to be monitored acutely to ensure a progressive neurologic loss is not missed.
ASIA Impairment Classification
- A. Complete – No sacral sensory or motor
- B. Sensory but no motor below NLI
-
C. More than half of Key muscles below
NLI have muscle grade <3 -
D. At least half of key muscles below NLI
have muscle grade > or = to 3 - E. Sensory and Motor normal.
Neurological recovery with the zone of injury
- Some (30%) initial Grade 0 muscles will develop some motor power but will likely be nonfunctional
- Most (90%) initial Grade 1-2 muscles will develop functional motor power (>3/5).
- Most (70-80%) quadriplegic patients will “descend” a full neurological level.
- Most recovery within the first 9 months of injury
Neurological recovery below the level of injury
- ASIA A rarely develop significant recovery (<3%)
- Some ASIA B will convert to ASIA C and D (more common if pinprick is preserved) – on average 50% will attain functional ambulation
- Most younger (< 50 yrs) ASIA C will attain functional ambulation
- Nearly all ASIA D will attain functional ambulation
Functional outcome by level
- C3-5: ventilator dependency
-
C5: hand to face approximation
power mobility - C6: short distance manual wheelchair
- C7: transfers could achieve independence at wheelchair level
- C8/T1: fine hand control
- T2-T10: complete independence at WC level
- L2: short distance ambulation with bracing
- L3: community ambulation with bracing
Central cord syndrome
- Incomplete (ASIA C or D) cervical spinal cord syndrome
- Arm weakness greater than leg weakness
- Neuropathology controversial
- Mechanism controversial
Brown-Sequard syndrome
- Incomplete spinal cord syndrome
- Ipsilateral weakness and contralateral pain and temperature loss
- Neuropathology: hemisection of spinal cord
- Mechanism: penetrating trauma
Anterior cord syndrome
- Incomplete spinal cord syndrome
- Absent pain sensation and motor function with sparing of light touch, temperature, and proprioception
- Neuropathology: lesion of anterior 2/3 of spinal cord
- Mechanism: ischemia of anterior spinal artery
Posterior cord syndrome
- Incomplete spinal cord syndrome
- Rarest of spinal cord syndromes
- Varying degrees of motor preservation with
loss of some sensory modalities - Neuropathology: lesion of posterior 1/3 of
spinal cord - Mechanism: ischemia of posterior spinal
arteries
Autonomic Dysreflexia
- Alteration of sympathetic control caused by noxious stimuli below the level of spinal lesion.
- Occurs in cervical and upper thoracic injuries
- Signs/Symptoms: dramatic hypertension, bradycardia, headache, sweating
- Treatment: removal of inciting cause
Sympathetic Trunk
Lies just lateral to the vertebral
bodies from T1 to L2/3lt
