A novel technique of ultrasound-guided glossopharyngeal nerve block to relieve cancer pain.

Sir,

Conventional glossopharyngeal nerve block (GPN) involves topical, intraoral, and peristyloid approach. However, ineffectiveness in deeper pathology, risk of vascular injury, and inadvertent block of closely associated other cranial nerves are their potential drawbacks.[1] We report the first successful use of a novel technique of GPN block, which is potentially devoid of such complications.

A 55-year-old man presented with uncontrolled throbbing and burning pain due to an unresectable cancer of the posterior one-third of the tongue [Figure 1]. It was 10/10 on the numeric pain rating scale (NRS) best relieved to 8/10 with oral medications (immediate release morphine 60 mg every 4 h and ibuprofen 400 mg every 8 h). The patient consented to this new technique of distal GPN block with potentially less chance of complications after refusing consent for peristyloid technique. This technique was first described by Azman et al.[2] in cadavers and normal volunteers. High-frequency ultrasound probe (6–15 MHz) was kept with its medial tip on lateral cornu of hyoid bone in transverse plane, and then the lateral tip of probe was rotated toward angle of mandible. Once the facial vessels in the intermuscular plane and the two muscle groups (superficial group of posterior belly of digastric and stylohyoid, and deep group consisting of styloglossus and stylopharyngeus) are identified, a 22-G lumbar puncture needle was advanced till it reached just superficial to the pharyngeal constrictor muscle (identified by the dirty air shadow of pharynx) [Figure 2]. After a successful diagnostic dose of 2-mL 0.5% ropivacaine, 1.2 mL of dexamethasone, 4 mg/dL, and 1 mL of 0.5% ropivacaine was injected after 24 h of the initial injection. The procedure was uneventful with no immediate complications. NRS at 24 h, 48 h, 4 days, 1 week, and 2 weeks postinjection were 2/10, 2/10, 3/10, 5/10, and 6/10, respectively.

Figure 1

Axial T2 weighted MRI images shows the infiltrative tumor (arrow) involving the right lateral part of the posterior one-third of tongue; MRI = Magnetic resonance imaging

Figure 2

High-resolution ultrasound images show the normal anatomy (a) before the needle advancement. The pharynx (ph) is identified by the echogenic dirty air shadow with its wall as an hypoechoic linear structure just anterior to it. The submandibular salivary gland (smg) and the facial vessels (arrow head) are also visualized. (b) The tip of the echogenic line (arrow) represents the needle tip in position before injection of the drug

In our case, the nerve block was at distal level just before GPN enters the pharynx. Only visceral sensory fibres of the GPN supplying the pharyngeal mucosa are affected at this level, preserving other innervations of the GPN. About 2 mL of nerve blocking agent is the maximum volume of drug the para-pharyngeal space would take without spreading to adjacent areas.[2] Dexamethasone has been reported to prolong duration of a nerve block and reduce severity of pain likely due to modulation of local inflammation and reduction in blood.[3] We refrained from using neurolytic agents such as alcohol or phenol because of its potential side effects on adjacent structures with a potential risk of pharyngeal perforation.[4] However, a safer agent meant that the duration of pain relief was relatively short, with adequate relief lasting for just about a week.

This case demonstrated that ultrasound-guided distal GPN block technique was technically feasible in bringing short lasting excellent cancer pain relief in our patient. Further trials are needed to validate the same in a larger cohort.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.