Functional anatomy of the brachial plexus sheaths.

Area of Science:

• Anatomy
• Medical Imaging
• Anesthesiology

Background:

• The brachial plexus sheath's structure is crucial for understanding regional anesthesia.
• Previous knowledge on the precise compartmentalization and spread of anesthetics within the sheath was limited.

Purpose of the Study:

• To investigate the detailed anatomical structure of the brachial plexus sheath.
• To elucidate the implications of this structure on the spread of local anesthetics during brachial plexus blocks.

Main Methods:

• Anatomical dissection of cadavers.
• Histological examination of brachial plexus tissues.
• Radiographic imaging with contrast media in cadavers.
• Computed tomography (CT) dye studies in surgical patients.

Main Results:

• The brachial plexus sheath is a multicompartmented structure with dense connective tissue proximally, becoming looser distally.
• Internal septa divide the sheath into individual compartments for each nerve.
• Injected local anesthetics spread longitudinally within compartments but show limited circumferential spread.
• This compartmentalization explains variable block success and onset times.

Conclusions:

• The brachial plexus sheath's multicompartmented nature defines individual nerve compartments.
• This anatomical arrangement directly influences the efficacy and spread patterns of brachial plexus anesthesia.
• Understanding these compartments is vital for optimizing brachial plexus block techniques.