Pathway from anterior suprascapular nerve block to the phrenic nerve: a cadaveric dye study

BACKGROUND

Anterior suprascapular nerve block is widely used for postoperative shoulder pain management. Although cadaveric studies show the spread and smudging of the phrenic nerve, our cadaveric injection investigation was conducted to investigate the pathway of diffusion of the dye toward the phrenic nerve from a more distal injection at the suprascapular nerve.

METHODS

We injected 5 ml of 0.1% methylene blue dye into the proximal portion of the suprascapular nerve (infra-omohyoid in the posterior triangle) in 12 neck specimens from six cadavers. Following meticulous dissection, we assessed the spread of the dye along the brachial plexus to the nerve roots and traced the phrenic nerve for staining.

RESULTS

The phrenic nerve was stained in 41.7% of the cases, the inferior trunk of the brachial plexus was unstained in all cases (100%), and the posterior division and suprascapular nerve were stained in all cases (100%). The nerves to the subclavius, dorsal aspect of the superior trunk, and C5 and C6 roots were stained in all cases. Anterior division of the superior trunk was observed in 75% of the specimens. The dye-spread pathway along the brachial plexus was dorsal, sparing the ventral aspect.

CONCLUSIONS

Our study demonstrated that the dye-spread pathway from the suprascapular nerve at the infra-omohyoid level to the phrenic nerve is dorsal to the brachial plexus.

A rapid micro-magnetic resonance imaging scanning for three-dimensional reconstruction of peripheral nerve fascicles

The most common methods for three-dimensional reconstruction of peripheral nerve fascicles include histological and radiology techniques. Histological techniques have many drawbacks including an enormous manual workload and poor image registration. Micro-magnetic resonance imaging (Micro-MRI), an emerging radiology technique, has been used to report results in the brain, liver and tumor tissues. However, micro-MRI usage for obtaining intraneural structures has not been reported. The aim of this study was to present a new imaging method for three-dimensional reconstruction of peripheral nerve fascicles by ¹T micro-MRI. Freshly harvested sciatic nerve samples from an amputated limb were divided into four groups. Two different scanning conditions (Mannerist Solution/GD-DTPA contrast agent, distilled water) were selected, and both T1 and T2 phases programmed for each scanning condition. Three clinical surgeons evaluated the quality of the images via a standardized scale. Moreover, to analyze deformation of the two-dimensional image, the nerve diameter and total area of the micro-MRI images were compared after hematoxylin-eosin staining. The results show that rapid micro-MRI imaging method can be used for three-dimensional reconstruction of the fascicle structure. Nerve sample immersed in contrast agent (Mannerist Solution/GD-DTPA) and scanned in the T1 phase was the best. Moreover, the nerve sample was scanned freshly and can be recycled for other procedures. MRI images show better stability and smaller deformation compared with histological images. In conclusion, micro-MRI provides a feasible and rapid method for three-dimensional reconstruction of peripheral nerve fascicles, which can clearly show the internal structure of the peripheral nerve.