Helen Triantafyllidi, MD, PhD

Hypertension Specialist

Chief of Hypertension Unit

2nd Department of Cardiology, Medical School,

University of Athens, ΑΤΤΙΚΟΝ Hospital

Intervational therapies for hypertension:

Bilateral sphenopalatine ganglion blockade

There is no conflict of interest

54% of strokes and 47% of IHDattributable to hypertension

Comment: This surgical intervention

was highly effective in reducing BP and

mortality, however, at the cost of very

severe complications in particular

orthostatic hypotension and a high

morbidity and mortality (1935-1960).

In terms of Efficacy: Better BP reduction with RDN

than sham-control group by all measures, HOWEVER

▪ not better than changes expected from a single

added antihypertensive pill

▪ considerable variability

▪ long-term efficacy is lacking

▪ possibility of nerve regrowth still exists

In terms of Safety: Results of recent sham-control studies indicate that RDN is

safe, HOWEVER

▪ renal artery stenosis has been reported post-RDN

▪ atherosclerotic lesions after endothelial injury can progress slowly and may

take years to become clinically apparent.

The sphenopalatine ganglion (SPG) is the largest

collection of neurons in the head outside of the brain,

located in the pterygopalatine fossa, posterior to the

middle nasal turbinate, under a 1–1.5 mm layer of

connective tissue and mucus membrane.

It has rich autonomic sympathetic and

parasympathetic components from the superior cervical

ganglion and it is connected with the brain stem and the

central nervous system (CNS).

SPG block by lidocaine is currently indicated in the

management of 1. medically resistant cluster headaches,

2. migraine, 3. trigeminal autonomic neuralgias as well

as 4. intractable orofacial pain syndromes.

The analgesic effect typically lasts beyond the

duration of anesthesia caused by the nerve blockade,

providing some patients with pain relief for several

weeks or even months. This prolonged analgesia may be

due to an effect on central pain modulation.

Sphenopalatine ganglion

G. Sluder. The role of the sphenopalatine

ganglion in nasal headache, N. Y. State J.

Med. 27 (1908) 8–13.

Responders: 24h SBP reduced by >5 mmHg

n=11/22 (50%)

Controls under sham

procedure with water for

injection instead of

lidocaine

Responders: 24h SBP reduced by >5 mmHg

n=12/33 (33%)

Responders:

24h SBP reduced by 9 mmHg

24h DBP reduced by 6.5 mmHg

➢Who responds: Responders presented with higher SBP at baseline (24 h,

daytime and night-time) compared with the non responders.

➢Safety: We did not notice any acute PR interval, BP or heart rate (HR)

alterations. Subsequently, it seems that there is no direct interaction between SPG

block and the cardiovascular SNS, instead a gradual decrease of BP levels for

the next 20–30 days after the SPG block was noticed.

➢Minor side-effects: Total destruction of the SPG by radiofrequency treatment

might lead to dryness of the eye (unusual), an “open nose” because the mucosa has

less inclination to swell, and hypesthesia or dysesthesia of the soft palate, maxilla,

or posterior pharynx. Numbness of the soft palate is usually temporary, and

sometimes loss of taste can be permanent. Subsequently, applying a long-term

deletion of the SPG block in antihypertensive treatment instead of SPG anesthesia

might affect the quality of life in a hypertensive population.

➢However, using lidocaine none of our patients suffered such a complication.

Sphenopalatine ganglion

block

• Our results indicate that SPG block might be a promising, non-invasive, safe,

painless and easy to perform therapeutic option of BP decrease without any

subsequent complications.

• It resembles to renal denervation as to the need of a bilateral application and the

unknown immediate effect since no drop in blood pressure is seen just after the procedure.

However, as SPG block just causes an anesthetic effect instead of destroying the nerve

fibers, a lot of questions emerge as for the long term BP decrease and when the

procedure has to be repeated as well as which is its impact in patients with more

severe arterial hypertension or even resistant hypertension.

• Finally, as with renal denervation, SPG should be effective in those hypertensive

patients with an activated SNS, so a period of patient selection should precede the

application of this procedure. On the other hand, SPG block might work as a selection

test for RDN procedure. We believe that the responders to SPG block hypertensive

patients might be the true responders to SNS modulation that RDN procedure seeks with a

subsequent long-standing BP decrease.

Sphenopalatine ganglion

block

Consequently, brain is connected with SPG through pretectum (midbrain),

ciliospinal center (spinal cord), SCG (cervical sympathetic trunk), internal carotid

artery and deep petrosal nerve (PPF).

Neural routesThe preganglionic sympathetic neurons

1. start from the ciliospinal center, a

structure which receives input from

the pretectum (midbrain structure)

and is located at the intermediate

horn of grey matter of the spinal cord

between the C8 and T1 regions, then

2. they ascend the cervical sympathetic

trunk to the superior cervical

ganglion (SCG) to synapse with the

postganglionic neurons (SCG input).

3. The postganglionic fibers follow

along the internal carotid artery

and enter the skull and the PPF as the

deep petrosal nerve which passes

through the SPG.

Sympathetic fibers under anesthesia (SPG) should transmit fewer neural

signals to the superior cervical ganglion:

1. Suppressed superior cervical ganglion sends fewer signals directly to CNS

resulting to BP decrease.

2. It seems likely that sympathetic excitation induces a sympathetic reflex causing

internal carotid and vertebrobasilar insufficiency and eventually resulting to

hypertensive response while the sympathetic withdrawal should lead to increased

blood flow and subsequent BP levels decrease.

3. The superior cervical ganglion and the carotid sinus of the internal carotid

artery are connected directly. It is suggested that the superior cervical ganglion

controls, at least partially, the state of contraction of the carotid sinus arterial wall and

thus has a role in the reflex homeostasis of blood pressure (fewer signals to carotid

sinus). On the other hand, increased blood flow due to sympathetic withdrawal after

SPG block should trigger a hypotensive response through carotid sinus pressure

receptors.

Proposed mechanisms of action

and BP lowering

✓ Impaired patient's compliance is one of the main reasons of the failure of any

antihypertensive medical treatment. Invasive methods should improve patient's

compliance to treatment due to the decreased number of antihypertensive

drugs needed.

✓ Renal artery nerves mapping, renal denervation, arterio-venous iliac fistula,

carotid barostimulation offer a new insight in arterial hypertension. Subsequently,

invasive methods of arterial hypertension management work but it is not known

yet who is the perfect candidate for their success.

✓ We feel that SPG block, a non-invasive method, might work either as a

therapeutic option after repeated blocks or as a selection test for RDN

procedure since responders to SPG block might be the right candidates for RDN

procedure.

✓ We will continue our research project in groups of ESRD patients as well as in

hypertensive patients with resistant hypertension while we are going to try a new

catheter for SPG blockade, the Tx 360.

Take home messages