Phrenic nerve pathway via infra-omohyoid suprascapular injection: A cadaveric study

Identification of pathway to Phrenic nerve after an Infra-omohyoid Suprascapular Injection: A Cadaveric Injection Study.

Interscalene block is gold standard for shoulder surgeries, but the phrenic paresis (PP) is persisting problem. The anterior approach to suprascapular nerve (SSN) has been advocated, but 20% times PP occurs. We in cadaveric study wanted to evaluate the path of dye diffusion from infra-omohyoid SSN to the phrenic nerve.

In 2 fresh cadavers (4 sides), an infra-omohyoid SSN block were administered with 5ml of 0.1% methylene blue dye is injected at 5ml/minute. Spread of the dye was inspected in real time. Dissection is performed at 30 minutes post injection. The stain pattern of suprascapular nerve, divisions of superior trunk, cephalad and caudal spread and stain of phrenic nerve was investigated.

The suprascapular nerve was stained in all 4 specimens. The posterior and anterior divisions, the lateral edge of superior trunk and C5 were stained. Table 1 Following the stain path the dye was dorsal to the brachial plexus divisions-trunks, winded around the C5 and appeared in the proximal part of the phrenic nerve (PN). The PN was stained in all specimens. Figure 1

The pathway to phrenic nerve from the suprascapular nerve injection exists. The dye tracked along the posterior fascial sheath of the dorsal aspect of the brachial trunks and cervical rami and spilled ventrally on the PN.