Stellate Ganglion Block for Hot Flashes: What the Evidence Actually Shows

A stellate ganglion block is an injection of local anaesthetic into a bundle of nerves sitting at the front of the lower neck, roughly level with the sixth and seventh cervical vertebrae. The stellate ganglion is part of the sympathetic nervous system, the network that governs the fight-or-flight response, and it relays signals to the head, neck, arms and upper chest.

The procedure itself is brief. You lie on your back with your neck slightly extended. The clinician uses ultrasound guidance, and sometimes fluoroscopy, to locate the ganglion and avoid the carotid artery and other structures nearby. A small volume of anaesthetic, typically bupivacaine or ropivacaine, is injected. The whole thing takes about 15 to 30 minutes including preparation, and most of that is setup.

You know it has worked because of a predictable and temporary set of signs: the eyelid on the injected side droops slightly, the pupil narrows, the face flushes and feels warm, and the arm on that side becomes noticeably warm. This combination is called Horner syndrome, and in this context it is a confirmation the block landed correctly rather than a complication. It wears off within hours.

The procedure has been used for decades in pain medicine for conditions like complex regional pain syndrome and post-herpetic neuralgia. Its use for hot flashes, and separately for PTSD, is a repurposing of an existing technique rather than a new invention.

The rationale rests on where hot flashes are generated. They are not a problem of the skin or the blood vessels themselves. They originate in the hypothalamus, the brain's thermostat, which becomes unstable as estrogen falls.

The current model centres on KNDy neurons, a cluster in the hypothalamus named for the three signalling molecules they use: kisspeptin, neurokinin B, and dynorphin. Estrogen normally restrains these neurons. When it withdraws, they become hyperactive and repeatedly trigger the heat-dissipation response, producing the flush, sweat, and rapid heartbeat you experience as a hot flash. This is precisely the pathway that fezolinetant and elinzanetant target, and [the guide to Veozah explains that mechanism in detail](/blog/veozah-fezolinetant-nonhormonal-hot-flash-treatment-explained).

The stellate ganglion sits downstream of all this, in the sympathetic outflow that carries the instruction to the blood vessels. Proponents argue two things: first, that interrupting this outflow blocks the physical execution of the flash, and second, that the ganglion has connections travelling back up to brain regions involved in temperature and stress regulation, so blocking it may quiet the loop rather than just its output.

That second claim is the more speculative one, and it is also the one that would explain why benefit might outlast the few hours of anaesthetic action. It is biologically plausible. It is not well demonstrated.

The research base is small, and the honest summary is that early enthusiasm was not confirmed when the procedure was tested against a placebo.

Lipov and colleagues (Lancet Oncology, 2008) published the pilot that generated the interest. Thirteen women with severe hot flashes, many of them breast cancer survivors who could not take hormone therapy, received a stellate ganglion block and reported dramatic reductions in flash frequency and severity over 12 weeks. The results were striking. The study had no control group.

Walega and colleagues (Menopause, 2014) ran the test that mattered: a randomised trial of 40 women comparing a real stellate ganglion block against a sham injection of saline into the subcutaneous tissue of the neck. Participants recorded symptoms in diaries and also wore an ambulatory skin conductance monitor, which detects hot flashes objectively rather than relying on recall.

The headline result was negative. Self-reported total hot flash frequency did not differ significantly between the real block and the sham over six months. But the picture was not uniformly flat. The objectively measured frequency of moderate-to-very-severe flashes was significantly lower in the treated group, and severity scores improved.

That split is the crux of the debate. Supporters read it as evidence that the block reduces the flashes that actually matter, and that diary self-report is too noisy to detect it. Sceptics read it as a secondary outcome in a small trial that missed its primary endpoint. Both readings are defensible from 40 participants, which is exactly the problem.

They recommend against it for now. The Menopause Society's 2023 Nonhormone Therapy Position Statement, published in *Menopause*, reviewed the full landscape of non-hormonal options and sorted them into recommended and not recommended categories. Stellate ganglion block falls into the second group, alongside several other interventions with promising early data that did not survive controlled testing.

The statement's recommended options are worth knowing, because they represent where the evidence actually is:

• •Fezolinetant and, more recently, elinzanetant, which block the neurokinin pathway directly. [A comparison of the two is here](/blog/lynkuet-vs-veozah-nonhormonal-hot-flash-pills-compared).
• •Cognitive behavioural therapy, which reduces the distress and interference of flashes substantially even when frequency changes less. [More on CBT for menopause](/blog/cbt-for-menopause-nice-recommended-nonhormonal-treatment).
• •Clinical hypnosis, which has surprisingly strong trial data. [The evidence on hypnotherapy](/blog/hypnotherapy-for-hot-flashes-does-it-actually-work).
• •Certain SSRIs and SNRIs, including paroxetine, venlafaxine and escitalopram. [How they compare](/blog/ssris-snris-for-hot-flashes-nonhormonal-menopause-guide).
• •Gabapentin and oxybutynin in selected cases.

"Not recommended" is not the same as "proven useless." It means the evidence is currently insufficient to justify the cost and risk for most people. A larger, well-designed trial could change that. But if a clinic is marketing the procedure as an established menopause treatment, that framing is running ahead of the science.

Most side effects are expected, temporary, and a sign the block worked. Serious complications are genuinely rare in experienced hands with ultrasound guidance, but they are not zero, and this is elective treatment for a non-life-threatening symptom.

Expected and temporary, resolving within hours:

• •Drooping eyelid, constricted pupil, and reduced sweating on the injected side (Horner syndrome)
• •Hoarseness or a lump-in-the-throat feeling from anaesthetic reaching the recurrent laryngeal nerve
• •Warmth, tingling, or temporary weakness in the arm
• •Nasal congestion on that side
• •Soreness at the injection site for a day or two

Uncommon: difficulty swallowing, a temporary change in voice lasting longer than expected, bruising, or dizziness.

Rare but serious: bleeding or haematoma in the neck, infection, injection into a blood vessel causing seizure or cardiovascular effects, puncture of the lung causing pneumothorax, and temporary paralysis of the diaphragm on one side. Rates in published series are low, generally well under 1%, and ultrasound guidance has reduced them further.

One practical warning: because a hoarse voice and a temporarily weak diaphragm are possible, blocks are not done on both sides at the same session.

There is also cost. Insurance rarely covers stellate ganglion block for vasomotor symptoms because it is not an approved indication, so most women pay out of pocket, often in the range of one to two thousand dollars per procedure, and the protocols being marketed usually involve more than one.

Placing the procedure next to the alternatives makes the decision clearer, because the differences are not subtle.

Effect size. Hormone therapy reduces hot flash frequency by roughly 75% in pooled trial data. Fezolinetant and elinzanetant produce reductions in the region of 60 to 65% in their pivotal trials, versus around 40% on placebo. Stellate ganglion block did not separate from a sham injection on its primary endpoint.

Reversibility. A pill can be stopped tomorrow if it does not suit you. An injection into your neck cannot be undone, though its effects do wear off.

Cost and access. Hormone therapy and generic SSRIs are inexpensive and widely available. The neurokinin antagonists are costly but increasingly covered. Stellate ganglion block is generally not covered for this indication and usually requires a pain specialist rather than a menopause clinician.

Evidence quality. This is the sharpest contrast. Fezolinetant went through the SKYLIGHT trial programme with thousands of participants across multiple studies. Elinzanetant went through OASIS 1, 2 and 3. Stellate ganglion block has one randomised trial of 40 women.

None of this means the procedure is worthless. It means it belongs at the end of a decision tree, not the beginning. If a treatment with thousands of participants behind it is available to you and you have not tried it, that is the more rational next step, and it is also the cheaper one.

The strongest case is for women with severe, frequent hot flashes who genuinely cannot use the better-evidenced options.

That group is real and not small. Women with hormone-receptor-positive breast cancer are typically advised against systemic estrogen and may also be taking tamoxifen or an aromatase inhibitor, which makes vasomotor symptoms worse. Some cannot take SSRIs or SNRIs because of interactions, notably the effect of paroxetine and fluoxetine on tamoxifen metabolism. Others have tried fezolinetant or elinzanetant without benefit or could not tolerate them. For a woman in that position, having twenty severe flashes a day and no remaining standard option, an experimental procedure with a modest safety profile becomes a more reasonable conversation.

It is a poor fit if you have not yet tried the recommended treatments, if your flashes are mild to moderate, if you take anticoagulants, if you have significant lung disease that would make a pneumothorax dangerous, or if you have a bleeding disorder or active infection.

If you are considering it, ask specific questions. How many of these has this clinician done for vasomotor symptoms specifically? Is ultrasound guidance used every time? What does the full protocol cost, including repeats? What do they tell you about the Walega trial? A clinician who describes the evidence as mixed and small is giving you an accurate picture. One who describes it as proven is not.

Start with the interventions that have survived sham-controlled testing, and give each a fair trial before moving on.

If hormone therapy is an option for you, it remains by far the most effective treatment for vasomotor symptoms, reducing frequency by around 75% in pooled trial data. Many women rule it out based on the original 2002 Women's Health Initiative reporting without knowing how substantially the interpretation has been revised for women starting therapy before 60 or within ten years of their final period.

If it is not, the neurokinin antagonists are the most significant development in non-hormonal treatment in decades, because they act directly on the mechanism that generates the flash rather than dampening it downstream.

Alongside either, cognitive behavioural therapy and clinical hypnosis are underused. They will not stop a flash, but they reliably reduce how much a flash costs you in sleep, concentration, and distress, and they have no side effects.

And be sceptical of the supplement aisle. [Black cohosh](/blog/black-cohosh-for-hot-flashes-does-it-actually-work) and [red clover](/blog/red-clover-for-hot-flashes-does-it-work) both perform poorly against placebo in controlled trials, despite the marketing.

The frustrating truth is that severe hot flashes in a woman who cannot take hormones remain genuinely hard to treat. That gap is exactly why procedures like this attract attention, and why it matters to look clearly at what the trials found rather than what the clinic website says.