Approaches that Protect the Pharyngeal Plexus

Difference between the two techniques lies in the deliberate measures taken during the ANP procedure to protect the pharyngeal autonomic nerves

Aim to reduce the risk of postoperative dysphagia (difficulty swallowing) by minimising both direct and indirect nerve damage.

Dissection is performed along the upper edge of the omohyoid muscle without cutting it.
The surgeon uses the lateral edge of the omohyoid muscle as an anatomical landmark to separate the visceral and carotid sheaths, using the omohyoid as a natural barrier to avoid accidental entry into the visceral sheath.
Extensive sharp dissection is avoided, particularly of the middle layer of the deep cervical fascia above the hyoid plane. Instead, blunt dissection with narrow hooks is used, a method referred to as the "incision shifting technique," especially for surgeries at the C3/C4 level.

The technique identifies and protects a membranous structure called the "septum" (connecting the sternocleidomastoid and omohyoid muscles). The surgical entry point is made below this septum in a designated "safe space" to avoid damaging the autonomic nerves within the visceral sheath.

Protected Retraction: Self-retaining retractors are fitted with rubber sheaths to buffer pressure on the visceral sheath. If these cannot be used, two narrow hooks are employed to prevent compression injuries to the nerves.
Reduced Surgical Time: The procedure aims to shorten surgical time to limit prolonged traction on the visceral sheath. This is achieved through careful preoperative assessment and the routine use of ultrasonic bone scalpels to improve surgical efficiency.

The NANP technique represents a more conventional approach where explicit protection of the pharyngeal autonomic nerves is not a focal point of the procedure.

The incision is centered on the surgical target segment, and the superficial layer of the deep cervical fascia is incised for exposure.
The omohyoid and sternocleidomastoid muscles are retracted medially and laterally, respectively to expose the surgical field.
A key difference is the use of sharp dissection with an electrocautery knife to cut any remaining connective tissue and the middle layer of the deep cervical fascia to achieve full surgical exposure.

In the ANP group, the rate of postoperative dysphagia was 6.3% at 3 days, falling to 0% at 3 months and 1 year.

In the NANP group, the rate of postoperative dysphagia was significantly higher at 20.6% at 3 days, 11.8% at 3 months, and 8.8% at 1 year.

Notably, there were no significant differences between the two groups in terms of operation time or intraoperative blood loss.

Both techniques also resulted in similar improvements in Neck Disability Index (NDI) and Japanese Orthopaedics Association (JOA) scores.

This technique is only applicable for high cervical approaches, the paper has only 29 patients out of 96 patients having a C3/4 procedure. I am not sure if there is selection bias of the NANP approach

Approaching the disc form medial to the omo-hyoid, in the mid or lower cervical region would logically be more protective of the nerves as one would land on the prevertebral fascia at a lower level i.e C4 body first then blunt dissect up to C3/4 disc space in the avascular retropharyngeal space.