Sphenopalatine Block

The sphenopalatine  (SPG) block is not a new technique, but has recently gained interest in the anesthesia community. SPG block was first described by Dr. Greenfield Sluder in 1908 (1). So for more than a century this technique has been known to be effective for various indications. Such indications include various presentations from facial pain somatic syndromes, CRPS, surgical and velocity trauma to the face and head, and most recently, relief from post dural puncture headache (PDPH) pain. And although the evidence to support the incorporation of the SPG block for PDPH is scarce, initial small population studies and case reports are encouraging. Compared to expensive, time consuming, invasive and considerably more risky procedures, the SPG block is simple, inherently safer and entirely less expensive. 

ANATOMY

The sphenopalatine ganglion (SPG) is a small triangular-shaped parasympathetic ganglion, measuring about 5 mm in size, located superficially in the pterygopalatine fossa. Specifically the SPG lies posterior to the middle nasal turbinate, and anterior to the pterygoid canal. It may be found as the nasal ganglion, pterygopalatine ganglion, or Meckel's ganglion. It lies deep to a 1 to 2 mm-thick layer of connective tissue and mucous membrane. The superficial location of the ganglion makes access to it fairly easy, and does nit require violation of the mucous membrane via needle. The SPG functions as a central location from which sympathetic, parasympathetic, and sensory information intersect. Because of this unique anatomy of tightly packed neuronal mixing, combined with a superficial location beyond a thin porous membrane, the SPG is easily susceptible to local anesthetics, and uniquely efficacious to a variety of pain generators. The pre-ganglionic parasympathetic axons meet directly within it. The maxillary division of the trigeminal nerve, post-ganglionic sympathetic neurons and somatic sensory afferent branches also pass through it. The SPG receives neuronal information from regions of upper pharynx, palate, glands of the nasal cavity, paranasal sinuses, and lacrimal gland.   Therefore, these parasympathetic, sympathetic neurons, and the somatic sensory nerves from the described regions, can all be blocked in this superficial location. Although there is some patient to patient variability, like many anatomical structures, the SPG location is generally at the posterior region of the middle turbinate bone. This points to the anterior middle aspect of the fossa containing the SPG.

Current literature

Articles abound regarding blockade of the SPG for a variety of facial and head pain syndromes is robust. However, as previously mentioned, available sources which promote the efficacy of the SPG block for relieving PDPH is limited. The sources available for the PDPH SPG block is primarily in the form of case reports. The first published paper suggesting the use of the SPG block for management of PDPH appeared in 2001 Cohen (4). Eight years later, in 2009, Cohen et al., formalized a publication, reporting their small population study of 13 parturients.  All participants suffered moderate to severe PDPH following epidural leaks secondary from epidural placement. Although not a double blinded, controlled or randomized, all participants were treated with SPG blocks. Most patients (11 of 13) reported satisfactory pain relief and did not require additional epidural blood patching (EBP). 2 of the 13 patients did not report pain relief and received a subsequent EBP (5). Patel and colleagues reported retrospective data of 72 patients over many years. Their study population of 72 patients fell into one of two groups. One group received an SPG block and the second received EBP. They measured pain scores at 1 hour and reported that the SPB block patients had pain relief comparable to the EBP group. They also measured pan scores at 24 hours and found there was no significant difference in either group. Incidentally, and predictably, they reported more complications in the EBP group.

Literature in support of SPG blockade for PDPH pain relief is not confined to anesthesia providers. In 2015, Kent and Mehaffey reported results from a mother small population observation. They performed SPG blocks in 3 patients complaining of postural headache following dural puncture, in the emergency room. Their technique included a low dose technique including 2% viscous lidocaine. They reported that all 3 patients had good relief following the intervention. The following year, the same researchers  reported a more formalized publication regarding post dural puncture headache parturients. This appeared in the Journal of Clinical Anesthesia.

Finally, in 2017, Nair and Rayani published a review work on the incorporation of the SPG block in the Korean Journal of Pain. It included reviews of the techniques and literature in support of the SPG block specifically for patients suffering from post dural puncture headache. 

Technique

Placement of the SPG block is likely the most simple and non-invasive technique available for pain providers. Following explanation and patient consent, the patient is placed in the supine position. The head is tilted backwards and comfort assured. This is essential as the patient will maintain this position for 10-30 minutes. This position created a pocket favored by gravity to hold the local anesthetic, and therefore promoting absorption at the site of the SPG. Patients susceptible to epistaxis, such as nasal polyps and similar conditions should be carefully considered prior to performing the SPG block. A padded swab, preferably connected with a hollow shaft post is selected. Some case reports promote the use of culture swab for this purpose as they meet all suggested criteria and are usually readily available at most full service care facilities. The soft  swab portion is then soaked in a high concentration, fast acting local anesthetic such as lidocaine 2-4%. Viscous lidocaine has also been described. The saturated swabs are then inserted, swab first, into the nares one at a time. The path of insertion is followed until resistance is met. The swabs are then left in contact with the posterior nasopharyngeal region for 10-30 minutes. Additional small local anesthetic doses, such as 1-3 mLs can be considered and are mentioned in case reports. Administering the local through a hollow shaft easily facilitates the deposition, without the awkwardness and mess of attempting to drip or wick additional medicine down a wooden, or solid shaft. Patients should experience pain relief in 5-10 minutes. They may then have the swabs removed and pain assessed. No reports of troublesome side effects have been reported however, lightheadedness and occasional nosebleeds appear in available literature. 

PEARLS

A common sense approach to patient positioning may include a slight Trendlenberg tilt, and -retreating the nares with a vasoconstrictor such as Afrin (oxymetazilone) prior to instituting the SPG block.

Conclusion

The SPG block is showing promise front patients suffering from a multitude of ailments, the most relevant to anesthesia providers is PDPH relief. The simple application of topical anesthetic to an easily reachable region, requires little from the patient and makes the technique even more appealing. The materials required are easily accessible in their most simple form from any full service hospital, although newer devices are available. This old and proven technique for facial and headache pain has a favorable track record suggesting safety and efficacy. The most compelling aspect of the recent interest for SPG blocks, specifically for the purpose or PDPH pain, is that, until recently (2009), we have made no significant improvement options for dural leaking beyond epidural blood patch. While favorably effective, the epidural blood patch is invasive carrying potentially serious complications such as additional dural puncture, nerve and tissue damage and infection. Not all patients suffering from this ailment care to endure a second epidural intervention and others may simply to be suitable candidates. These scenarios make the non invasive SPG block appealing for ER, neurology and anesthesia providers.

SOURCES

• Pain Physician 2013; 16:E769-E778 • ISSN 2150-1149

• A Novel Revision to the Classical Transnasal Topical Sphenopalatine Ganglion Block for the Treatment of Headache and Facial Pain

• Kenneth D. Candido, MD1,2, Scott T. Massey, MD1, Ruben Sauer, MD1, Raheleh Rahimi Darabad, MD1, and Nebojsa Nick Knezevic, MD, PhD1,2

• 5. Cohen S, Sakr A, Katyal S, Chopra D. Sphenopalatine ganglion block for postdural puncture headache. Anaesthesia. 2009;64:574–575. [PubMed]

• 6. Patel P, Zhao R, Cohen S, Mellender S, Shah S, Grubb W. Sphenopalatine ganglion block (SPGB) versus epidural blood patch (EBP) for accidental postdural puncture headache (PDPH) in obstetric patients: a retrospective observation; 32nd Annual Meeting of the American Academy of Pain Medicine; 2016 Feb 18-21;

• 7. Kent S, Mehaffey G. Transnasal sphenopalatine ganglion block for the treatment of postdural puncture headache in the ED. Am J Emerg Med. 2015;33:1714.e1–1714.e2. [PubMed]

• 8. Kent S, Mehaffey G. Transnasal sphenopalatine ganglion block for the treatment of postdural puncture headache in obstetric patients. J Clin Anesth. 2016;34:194–196. [PubMed]

• 9. Nair A, Kumar Rayani B. Sphenopalatine ganglion block for relieving postdural puncture headache: technique and mechanism of action of block with a narrative review of efficacy

• Korean J Pain. 2017 Apr; 30(2): 93–97. Published online 2017 Mar 31. doi: 10.3344/kjp.2017.30.2.93