I'm not a physician, or even a scientist. I am someone who is interested in psychiatry, though, so I use that as a disclaimer from time to time so that people know what my perspective is.
I have read about ketamine being used for a variety of mental illnesses as well as for conditions like complex regional pain syndrome. The way it's been described in media for the public is that it "resets" the brain in some ways.
In that way, and that it's an anesthetic agent, it sounded similar to this neck injection, which is also some sort of anesthetic and is also described as "resetting" the brain. I think ECT is conceptualized that way (as resetting things), at least by the general public.
Oh yeah, I can see that connection. There's no clear consensus on this, but I'm in the camp that believes that ketamine works by "resetting" the brain - one of the downstream effects of NMDA blockade (ketamine's primary known mechanism of action) is to decrease neuroplasticity in certain pathways, which might decrease the tendency of the depressed brain to form abnormal "bad" connections. It would also reduce the tendency to form abnormal "good" connections, but since that's not a problem in people with depression, it's not as relevant of an effect. I guess you could describe that as "resetting" the brain.
ECT still sort of "resets" the brain, but in a very different way. Some research suggests that it restores the brain to a point where it is better at forming some of the normal "good" connections. So you could say that there's some vague relationship with ketamine, but it's resetting a completely different system in the brain.
And a ganglion block doesn't "reset" anything in the brain itself - it would block off some of the signals connecting the brain to the rest of the body. Those signals are involved in some of the abnormal physical stimulation experienced by people with PTSD - they get overstimulation of their "fight or flight" system in response to stimuli that shouldn't normally trigger that. If you turn off a ganglion that is involved in that process, it would prevent that fight/flight response from being triggered. It wouldn't "cure" the brain process that is causing PTSD, but it'd essentially break the system that causes the symptoms of the illness.
A lot of neuroscientists think that PTSD is actually a form of depression/anxiety that involves this extra overstimulation due to the patient's history of trauma superimposed on their background mental illness. While it's hard to know whether this is an accurate characterization, it's a useful model for thinking about the illness. Based on that, I'd expect that an SGB might treat the physical symptoms of PTSD, but wouldn't treat the depression/anxiety that is so commonly present.
After I wrote that last sentence, I did some cursory review of the scientific data on SGB, and it looks like it's in agreement with what I was expecting. There is evidence to say that it reduces panic/anxiety symptoms (which are mediated by the fight/flight system), but there's no data on whether it improves depressive/psychological symptoms. So I'd be careful about characterizing it as a "cure," especially since it doesn't actually treat the brain.
That said, I think that this could be a useful research tool to help us better understand the pathophysiology of PTSD, panic disorder, and OCD. If we quantified psychiatric and physical symptoms before and after the procedure, it could help us better characterize the extent to which each of those illnesses is CNS vs. autonomic. I wonder if reduction in autonomic symptoms could lead to a neuroplastic change in the brain that causes improvement in mental symptoms, especially for people with OCD.
