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General Information
33 Vertebrae: 7 cervical, 12 thoracic, 5 lumbar, 5 sacral (fused), 4 coccygeal (fused)
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Spinal Regions: Cervical
- C1-C2: unique bones allow stabilization of occiput to spine and rotation of head
- Motion: rotation and flexion/extension
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Spinal Regions: Thoracic
- Relatively stiff due to costal articulations
- Motion: rotation
- Minimal flexion/extension
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Spinal Regions: Thoracolumbar
- Facet orientation transitions from semicoronal to sagittal
- Segments are mobile
- Most common site of lower spine injuries
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Spinal Regions: Lumbar
- Largest vertebrae
- Common site for pain
- Houses caudal equina
- Motion: flexion/extension (minimal rotation)
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Vertebrae
- Uniquely shaped bones that support the axial musculature and protect the spinal cord and nerve roots
- Body (Centrum): Has articular cartilage on both superior and inferior surfaces; articulates with intervertebral discs and gets larger distally
- Arch: Made up of pedicles and lamina. Develops from 2 ossification centers that fuse. Failure to fuse results in spina bifida. It forms the vertebral canal for the spinal cord
- Spinous Processes: ligament attachment site
- Transverse Processes: rib (t-spine) and ligament attachment site
- Vertebral Foramen: spinal cord/cauda equina
- Neural Foramen: nerve roots exit via here
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Spinal Levels and Corresponding Structures
- C2-3: Mandible
- C3: Hyoid Cartilage
- C4-5: Thyroid Cartilage
- C6: Cricoid Cartilage
- C7: Vertebral Prominens
- T3: Spine of Scapula
- T7: Xiphoid, Tip of Scapula
- T10: Umbilicus
- L1: Conus Medullaris (End of Cord)
- L3: Aorta Bifurcation
- L4: Iliac Crest
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Sensory Testing
- C5: Lateral Shoulder
- C6: Thumb
- C7: Middle Finger
- C8: Ring & Small Fingers
- T1: Ulnar Forearm & Hand
- L3: Anterior & Medial Thigh
- L4: Medial Leg & Ankle
- L5: Dorsal Foot & 1st Web Space
- S1: Lateral & Plantar Foot
- S2-4: Perianal Sensation
- Positive Test = cervical root compression/lesion
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Motor Testing
- C5: Deltoid (resisted abduction)
- C6: Biceps (resisted elbow flexion)
- C7: Triceps (resisted elbow extension)
- C8/T1: Intrinsics (resisted finger abduction)
- L3-4: Quadriceps (knee extension)
- L4: Tib Ant (Ankle DF)
- L5: EHL (Toe DF)
- S1: Gastroc (Ankle PF)
- S2-4: Anal Sphincter (Anal Squeeze)
- Positive Test = cervical root compression/lesion
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Reflex Testing
- Biceps = C5
- Brachioradialis = C6
- Triceps = C7
- Patellar Tendon = L4
- Achilles Tendon = S1
- Positive = radiculopathy
Babinski and ankle clonus= upper motor neuron/myelopathy
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Descending (Motor) Tracts
- Anterior Corticospinal
- Lateral Corticospinal
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Anterior Corticospinal
- Function: innervates motor neurons - voluntary motor
- Minor motor pathway
- Injured in anterior cord syndrome
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Lateral Corticospinal
- Function: innervates motor neurons - voluntary motor
- Major motor pathway
- Injured in Brown-Sequard Syndrome
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Ascending (Sensory) Tracts
- Anterior Spinothalamic
- Lateral Spinothalamic
- Dorsal Columns
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Anterior Spinothalamic
- Light touch sensation
- Injured in anterior cord syndrome
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Lateral Spinothalamic
- Pain and temperature sensation
- Injured in Brown-Sequard Syndrome
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Dorsal Columns
- Proprioception and Vibratory Sensation
- Usually preserved, injured in posterior cord syndrome
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Spinal Cord
- Runs from brain stem to conus medullaris (termination at L1) within the spinal canal
- Terminale filum and cauda equina (lumbar and sacral nerve roots) continue in the spinal canal
- Has layered covering (membranes) = dura mater, arachnoid mater, pia mater (outisde --> inside)
- Made up of multiple ascending (sensory) and descending (motor) tracts and columns
- Wider in the cervical and lumbar spines where roots for plexuses to innervate the upper and lower extremities
- Paired (R & L) nerve roots emerge from each level
- Nerve roots made up of ventral (motor) and dorsal (sensory) roots
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Spinal Nerves
- Made up of a ventral (motor) root and dorsal (sensory) root
- 31 pairs (L&R)
- Cell bodies for sensory nerves are in the dorsal root ganglia
- Motor nerve cell bodies are in the ventral horn of the spinal cord
- Roots exit spinal column via intervertebral (neural) foramen (under pedicle)
- C1-7 exit above their vertebrae, C8-L5 exit below their vertebrae
- Can be compressed by herniated discs, osteophytes, and hypertrophied soft tissues (ligamentum flavum, facet capsule)
- Spinal nerves divide into dorsal and ventral rami
- Dorsal rami innervate local structures (neck & back mm, overlying skin, facet capsule, etc)
- Ventral rami contribute to plexus and become peripheral nerves to the extremities
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Cervical Plexus
C1-C4 Ventral Rami (behind IJ and SCM)
- 1) Lesser Occipital Nerve
- 2) Greater Auricular Nerve
- 3) Transverse Cervical Nerve
- 4) Supraclavicular Nerve
- 5) Ansa Cervicales
- 6) Phrenic Nerve
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Lesser Occipital Nerve
- C2-3
- Arise from posterior border of SCM
- Sensory: superior region behind auricle
- Motor: none
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Great Auricular Nerve
- C2-3
- Exits inferior to lesser occipital nerve, ascends on SCM
- Sensory: over parotid gland & behind ear
- Motor: none
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Transverse Cervical Nerve
- C2-3
- Exits inferior to greater auricular nerve, then to anterior neck
- Sensory: anterior triangle of the neck
- Motor: none
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Supraclavicular Nerve
- C2-3
- Splits into three branches = anterior, middle, and posterior
- Sensory: over clavicle, outer trap and deltoid
- Motor: none
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Ansa Cervicales
- C1-3
- Superior (C1-2) and inferior (C2-3) roots form loop
- Sensory: none
- Motor: omohyoid, sternohyoid, sternothyroid
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Phrenic Nerve
- C3-5
- On anterior scalene into thorax between subclavian artery and vein
- Sensory: pericardium & mediastinal pleura
- Motor: diaphragm
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