Saddle anesthesia refers to numbness of the perineum and inner thighs and is often associated with cauda equina syndrome. Poetic. The cause is generally a herniated disc or spondylolisthesis at the L5/S1 vertebrae. Paralysis and incontinence may result. Review the anatomy of the vertebral column and spinal canal. Include bones, articulations, ligaments, spaces, contents, muscles, movements and limitations of movement, vasculature and lymphatic drainage, innervation, and relationships. Include mention of the fascial layers penetrated during lumbar puncture and a brief account of saddle anesthesia. (12 pts)

General Comment

• Vertebral column forms an osseofibrous canal that protects the spinal cord

Bones

• Seven cervical, 12 thoracic, 5 lumbar, 5 sacral, 4 coccygeal = 33 (9 fused)
• C1 and C2
• Cervical - bifid spines, transverse foramina, and more
• Thoracic - Rib articulations and more
• Lumbar - large bodies and more
• Sacral - fused and more

Boundaries of the Vertebral Foramen

• Vertebral region
  • Anterior - posterior longitudinal ligament, vertebral body
  • Posterior - lamina
  • lateral right and left - pedicle
• Intervertebral region
  • Anterior - intervertebral disk
  • Posterior - ligamentum flavum
  • Lateral right and left - intervertebral foramen, zygapophyseal
• Superior - foramen magnum
• Inferior - Sacral hiatus

Articulations

• Intervertebral disk - nucleus pulposus, annular ligament, anterior and posterior longitudinal ligaments
• Zygapophyseal joint - changes from cervical to lumbar regions and movements
• Costotransverse and costovertebral joints
• Curves - cervical lordosis, thoracic kyphosis, lumbar lordosis, sacral kyphosis, scoliosis

Spaces and Contents

• Epidural space - between bone/ligament and dura mater
  • Internal anterior and posterior vertebral plexuses
  • Epidural fat
• Subdural space - potential space between dura mater and arachnoidea
• Subarachnoid space - between arachnoidea and pia mater
  • Cerebral Spinal Fluid
• Spinal cord - C1 to L2 (conus medullaris)
• Thecal sac (dural sac) - C1 to S2
• Cauda equina
• Filum terminale internal and external - sacral hiatus and coccyx

Stability of the Spinal Cord

• Denticulate ligaments
• Filum terminale internal and external
• Rootlets
• Meninges and cerebral spinal fluid (CSF)
• Cauda equina

Muscles

• Erector Spinae - spinalis, longissimus, and iliocostalis
• Transversospinalis
• Psoas major and quadratus lumborum (optional comment)
• Longissimus cervicis and capitus
• Splenius cervicis and capitus
• Longus colli and capitus (optional comment)

Innervation

• Deep intrinsic muscles - dorsal rami
• Intermediate muscles - ventral rami
• Psoas major and quadratus lumborum - ventral rami
• Superficial muscles of the back - brachial plexus, spinal accessory, and cervical plexus
• Zygapophyseal branches

Movements

• Flexion
• Extension
• Lateral flexion
• Rotation

Ligaments and Limitation of Movements

• Anterior longitudinal ligament - limit extension
• Posterior longitudinal ligament - limit flexion
• Ligamentum flavum - limit flexion, gradual relaxation
• Interspinous - limit flexion
• Supraspinous - limit flexion

Vascularization

• Radicular arteries - essential for blood supply to cord
• Augment anterior and posterior spinal arteries
• Artery of Adamkiewicz - from lower posterior intercostal artery or upper lumbar artery, surgical risk
• Anterior and posterior internal vertebral venous plexuses, valveless and spread of infection or metastatic disease
• Anterior and posterior external vertebral venous plexuses, valveless and spread of infection or metastatic disease
• Valveless - spread of infection
• Epidural fat

Lymphatic drainage

• Paraaortic nodes
• Deep cervical nodes
• Lateral sacral nodes
• Venous plexuses and metastatic disease

Lumbar Puncture an Relationships

1. skin
2. tela subcutanea
3. investing fascia
4. supraspinous ligament
5. interspinous ligament
6. ligamentum flavum
7. epidural space
8. dura mater
9. subdural space
10. arachnoidea
11. subarachnoid space and cerebral spinal fluid (CSF)
12. pia mater (L2 and above)
13. spinal cord (L2 and above) or cauda equina

Saddle anesthesia - Optional

• L5/S1 anterior displacement
• Lordosis
• Compressed sacral nerves within cauda equina

Injuries to the brachial plexus include Erb's Palsy (an upper trunk injury), Klumpke's Palsy (a lower trunk injury), Brachial Plexus Palsy, Erb-Duchenne Palsy (childbirth traction injury), and "Burners" or "Stingers" (usually associated with sports-related brachial plexus injuries). Review the structure (roots, trunks, divisions, cords, and branches) of the brachial plexus. Limit your review of relationships to the region of the axilla. Discuss the deficits, compensations, and deformities that result from injury to the ulnar nerve within the axilla. (12 pts)

Structure (Roots, Trunks, Divisions, Cords, and Branches)

• Roots - ventral rami C5 - T1; neck
• Trunks - upper (C5 - C6), middle (C7), lower (C8 - T1); neck
• Divisions - anterior (mostly flexors), posterior (mostly extensors); how they combine to form cords; neck
• Cords - medial, lateral, and posterior named for relationship to axillary artery; axilla
• Branches - brief discussion of each branch

Relationships

• Cords of the brachial plexus are within the axilla.
• Cords surround the axillary artery and are named accordingly; the medial, lateral, and posterior cords.
• Superior: first rib, outlet syndrome
• Inferior: clavical, outlet syndrome
• Anterior: pectoral muscles
• Posterior: subscapularis
• Lateral: head and neck of humerus
• Medial: serratus anterior
• Inferior free edge of teres major
• Axillary sheath
• Axillary vein

Boundaries of the axilla

• Superior: clavical and thoracic outlet
• Inferior: skin of the axilla; teres minor and serratus anterior
• Anterior: pectoralis major and minor
• Posterior: latissimus dorsi and teres major
• Medial: serratus anterior
• Lateral: humerus

Ulnar Nerve Injury

• Flexor carpi ulnaris
  • Flexion compensated by long flexors of the forearm
  • Adduction compensated by extensor carpi ulnaris
• Flexor digitorum profundus
  • No compensation of flexion of distal IP for the the ring and little fingers
  • Compensation for flexion at joints proximal to DIP by long flexors
  • Compensation for flexion at MP joints by intrinsic muscles of the hand
• Intrinsic muscles of the hand
  • Clinical: claw hand
    • Hyperextension at MP joints and tethering at the IP joints
  • Loss of adduction at the MP joints
    • Minor compensation by lumbricals
  • Loss of abduction at the MP joints
    • Minor compensation by lumbricals
  • Loss of extending IPs while flexing MP
    • No compensation

Carpal tunnel syndrome can cause tingling, numbness, weakness, or pain in the fingers or hand. Review the anatomy of the carpal tunnel. Include bones, ligaments, contents, relationships, nerve injury, and lymphatic drainage. (12 pts)

General Comments

• Osseofibrous tunnel with non-yielding borders
• Carpal tunnel syndrome and median nerve compression

Bones

• Anterior surfaces of wrist bones
• Lunate may dislocate into tunnel

Ligaments

• Flexor retinaculum
  • Distal medial - hook of hamate
  • Proximal medial - pisiform
  • Distal lateral - trapezium
  • Proximal lateral - scaphoid

Contents

• Flexor digitorum superficialis - anterior
• Flexor digitorum profundus - posterior
• Flexor pollicis longus - intermediate and lateral
• Median nerve - anterior and lateral
• Tendon sheaths

Nerve injury

• Median nerve
  • Atrophy of thenar eminence
  • Supinated thumb
  • Weakened flexion and abduction of thumb
  • Possible clawing of index and middle finger
  • Loss of opposition
  • Weakness in extending IPs while flexing MPs for the index and middle finger.
  • Paraesthesia over palm and radial 3.5 fingers on palmar side

Lymphatic drainage

• Deep drainages along upper limb vessels to lateral axillary nodes
• Superficial drainages along cephalic and basilic veins toward axillary nodes.