Continuing the theme of interesting single case reports, I was pleased to see a paper about brain activity in someone who suffered a panic attack in the middle of an fMRI brain scan experiment.The unfortunate volunteer, a 46 year old woman, was taking part in an experiment looking at restless-leg syndrome. The scan lasted 40 minutes, and everything was going smoothly until quite near the end, when out of the blue, she had a panic attack.
Obviously, the scan had to be abandoned - as soon as the volunteer pressed the emergency "panic button", they stopped the scan and got her out of the MRI. (This kind of thing is why we have such buttons!) However, they decided to see what happened in the woman's brain as the panic started using the data they acquired up to that point.
Here's what they found: the top graph here shows her heart rate. It starts increasing a bit and then spikes, which shows exactly when the attack occurred. What about the brain? Well, amygdala and left insula activity sort of increase around this time. A bit. If you stare at the lines hard enough.
If you believe they did, it makes sense because the amygdala is known to be involved in anxiety (amongst other things) while the insula is responsible for the perception of the body's internal state, which is rather out of whack during a panic attack.
What doesn't make sense is the middle temporal gyrus bit, which was statistically the only part of the brain where activity was significantly correlated with heart rate (in whole-brain analysis). That region is not believed to have anything to do with panic, and to be honest, it's probably just a fluke.
This is only the second published report about panic during fMRI. There was one previous paper from 2006 about an attack in someone with a history of panic, which also found amygdala activation. But there are sure to be others out there which haven't made it into print - anxiety and panic during scans is not unheard of (the scanner is rather claustrophobic). It would be interesting to get more data on this, because it's obviously rather hard to research real-life panic attacks, on account of them being unpredictable.
Spiegelhalder, K., Hornyak, M., Kyle, S., Paul, D., Blechert, J., Seifritz, E., Hennig, J., Tebartz van Elst, L., Riemann, D., & Feige, B. (2009). Cerebral correlates of heart rate variations during a spontaneous panic attack in the fMRI scanner Neurocase, 1-8 DOI: 10.1080/13554790903066909
11 comments:
It's not uncommon for psychologists to induce panic attacks in the context of teaching people to cope with them, so a full study would be possible... May have trouble with ethics committees though.
It's also possible to induce panic with various drugs (in some people). But induced panic attacks might differ from "natural" ones.
One interpretation is that the spike, well, spikelet in the LTG is an attempt to inhibit anxiety in the other hemisphere. When it fails, the demons are let loose. But this doesn't seem exactly compelling on the facts.
More constructive is to ask about the limits of the technique. Suppose there's a network of neurons, cortical presumably, set up to go into action in an emergency and zap the hypothalamus directly, bypassing the amygdala. Could such a focus be too small to pick up?
Temporal lobe seizures are supposed to involve some spooky states of consciousness, like religious exhaltation and communing with the cosmic spirit. Has anyone caught that with a functional scan, or even an EEG?
maybe e tempral epilepsia should be considered ?
My understanding is that any seizure in the cortex should light up a fMRI, and this tracing isn't impressive. Maybe an EEG would have shown some spiky activity. It's lo-tech, but a few questions about history of her panic disorders and other seizure symptoms would be helpful to argue against temporal lobe epilepsy.
The control of heart rate is out of the hypothalamus, and it may not be well visualized, or the relevant neurons may be too few to show up on fMRI. But something in the cortex was involved if the claustrophobia of being in the machine set her off. So the straightforward question is how small can a active set of cortical neurons be and set off the hypothalamus.
An off-the-wall possibility of pheochromocytoma, an adrenal tumor which secretes epi and norepi. It can present with paroxysmal hypertension or tachycardia. This is not a fun experience and it can cause panic. It would be interesting to know her blood pressure and catecholamine levels during the attack.
Otto: That's an interesting point, actually, but I think the fact that the patient had no history of any kind of neurological problems, or panic, makes it unlikely.
The fMRI is also rather unimpressive, as Roger says, although it's worth bearing in mind that all fMRI signal is relative.
So if someone goes into the scanner with massive epileptic activity in a certain area, that area might not appear abnormal on fMRI, because metabolism would be high, but constant, and fMRI can only detect changes.
That's one of the reasons why you use EEG or PET to diagnose neurological disorders, rather than fMRI...
"Obviously, the scan had to be abandoned, but the researchers, not wanting the data they had got to go to waste, decided to see what happened in the woman's brain just as the panic started."
This seems to be the reason to publish it. Whoever witnessed a panic attack will imagine what happened to the patient: as the data show, a very strong arousal induced including an increased heart rate as well as high muscle tension can be observed. I would not speculate how this increased heart rate is linked to blood flow, blood volume, and the specific BOLD effect in particular regions of the brain. But the muscular activity will surely induce body movements that result in strong movement artifacts. Therefore, as long as they do not publish the movement correction data, I am pretty sure that I would easily detect strong "activity" in the salmons brain as well.
There is usually no relationship between a panic attack and an epileptic seizure. However, in contrast to a panic attack, most of the epileptic seizures can be detected by EEG. There are a few studies that combined EEG and fMRI on order to observe the particular BOLD signal. Since it is rather difficult and ethically not recommend to induce a seizure in the scanner one is taking interictal spike activity as a model. In this studies interictal spike activity is linked to negative BOLD effects.
Herbert: Motion and physiological confounds are obviously a concern. They claim -
"FMRI signal artefacts that were induced by cardiac pulsatility were corrected using the RETROICOR method ... The movement parameter time curves of intra-session slice alignment showed that our data was clearly not dominated by movement artefacts, because no scan had a translational movement parameter of more than 0.70 mm or a rotational movement parameter of more than 0.40 degrees."
Wow that's pretty amazing, I really believe that some people have to sacrifice for the rest of the people that suffer the same disease.
http://hubpages.com/hub/Triggers-and-Causes-of-panic-attacks
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