Disturbances of cutaneous sensation along a dermatome distribution signals problems with a spinal nerve (herniated disc). Disturbances of cutaneous sensation along a peripheral nerve distribution signals problems with a peripheral nerve (entrapment). Identify the C5 and T1 dermatomes. Account for their adjacent distributions despite the nonadjacent cord levels of the spinal nerves. (6 pts)

Lymphatic Drainage

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Innervation

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Vasculature

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Compression of the median nerve within the carpal tunnel my lead to atrophy and dysfunction of the muscles of the thenar eminence. Discuss the innervation, vasculature, movements, and muscles of the thenar eminence. (6 pts)

Anatomy

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Relationships

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Embryology

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“Saturday night palsy” refers to nerve damage that can occur a person falls asleep with their arm compressed by a chair arm. Discuss boundaries, relationships, contents and injuries of the triangular interval (lower triangular space). (6 pts)

Boundaries

• Superior: Teres Minor and subscapularis
• Lateral: Surgical neck of humerus, lateral head of triceps brachii
• Medial: Long head of triceps brachii
• Anterior: Spiral groove of humerus, opening to anterior arm
• Posterior: Brachial fascia, tela subcutanea, skin

Relationships

• Communication between axilla/anterior arm and posterior arm compartments
• Quadrangular space, triangular space (upper triangular space)
• Middle and radial collateral arteries
• Ascending branch of profunda brachii

Contents

• Radial nerve
• Profunda brachii artery
• Profunda brachii vein

Injuries

• Radial nerve palsy aka “Saturday Night Palsy”
• Sensory Loss
  • Distribution of cutaneous branches
    • Posterior cutaneous nerve of arm
    • Lower lateral cutaneous nerve of arm
    • Posterior cutaneous nerve of the forearm
    • Superficial radial nerve
  • Motor Loss
    • Discussion of triceps innervation – possible sparring of forearm extension
    • Weakened elbow flexion
    • Loss of wrist extension (“wrist drop”)
    • Weakened radial deviation
    • Weakened ulnar deviation
    • Weakened MCP and IP joint extension
    • Weakened thumb abduction
  • Profunda brachii artery and vein
    • Collateral circulation

A lumbar puncture is a procedure for withdrawing cerebral spinal fluid for diagnosis. Discuss the location, fascial layers penetrated, and spaces penetrated when withdrawing cerebral spinal fluid from the spinal canal. (6 pts)*

Location

• Between L3 & L4 or L4 & L5 - The needle is easily penetrated between the lumbar vertebrae, and not through the fused sacral vertebrae
• Inferior to conus medullaris - the end of the spinal cord around levels L1/L2
• Superior to the end of the dural sac at S2
• Cauda equina - nerve roots inferior to conus medullaris are freely movable within CSF minimizing the likelihood of damage

Layers and Spaces Penetrated - From the Posterior - Superficial to Deep

• Skin
• Tela subcutanea
• Supraspinous ligament
• Interspinous ligament
• Ligamentum flavum
• Epidural space
• Dura mater
• Subdural space
• Arachnoid mater
• Subarachnoid space - location of CSF

If above L1 - could cause serious damage because the next layers penetrated would be:

• Pia mater
• Spinal Cord

The stability of the axial skeleton is greatly dependent on ligamentous support. A failure of ligamentous support may cause back pain; one of the most frequent complaints that leads to an office visit by patients. *Discuss the anatomy, relationships, and functions of the posterior longitudinal ligament of the vertebral column. (6 pts)*

Location and structure

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Topography and Relationships

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