Thanks for using the forum. I am happy to address your questions, and my answer will be based on the information you provided here. Please make sure you recognize that this forum is for educational purposes only, and it does not substitute for a formal office visit with your doctor.
Without the ability to examine you and obtain a history, I can not tell you what the exact cause of your symptoms is. However I will try to provide you with some useful information.
It sounds like your husband had an episode of fast heart beat associated with some confusion and some unsteadiness. With normal CSF, meningitis is not a likely diagnosis. With a fast heart rate, a cardiac cause is more likely than a neurologic one. The neurologic symptoms of unsteadiness and confusion would be secondary to the brain not receiving enough blood because of abnormal heart function. A fast heart rate could be electrophysiologic, due to an abnormal heart rate generator, or metabolic, from something else going on in the body such as thyroid problems. As you mention, toxic exposures can lead to this as well. Continued follow-up with a cardiologist is certainly recommended if these episodes of fast heart rate occur again.
There are very few neurologic causes to fast heart rate, but one would be seizure; it sounds like you are set up for EEG, which would be useful in elucidating this further. The other neurologic cause of the fast heart rate associated with the symptoms described above could be due to a problem with the autonomic nervous system. The autonomic nervous system is the part of the nervous system that controls blood pressure, heart rate, and other functions. It is not located in one specific part of the brain or other body part but is rather made up of several different components: a region in the brainstem, certain receptors located on blood vessels and in the heart, and small nerves in our skin, among other areas. Dysfunction of the autonomic nervous system due to whatever cause can lead to a variety of symptoms including but not limited to orthostasis (which means symptoms or signs resulting from assuming an upright posture), light-headedness with drops in blood pressure when sitting up or standing up (this is an example of orthostasis), fast heart rate, syncope (passing out), constipation, diarrhea, sweating abnormalities etc. If there is a problem in the small nerve fibers, what is medically termed a small fiber neuropathy, in addition to these symptoms, burning/tingling in the feet and hands or mild sensory loss may also occur. One type of autonomic dysfunction is POTS syndrome, a condition with no known definitive cause in which the heart rate goes up inappropriately, leading to palpitations and light-headedness, and this is treated with medications that prevent these heart rate increases such as beta blockers. Disorders of the autonomic nervous system are diagnosed by testing such as a tilt table test.
While evaluation by a neurologist with completion of the tests you specify above is recommended, continued evaluation by a cardiologist is important as well.
Thank you for this opportunity to answer your questions, I hope you find the information I have provided useful, good luck.
Does the tachycardia and severely altered mental state last for 2 days with a panic attack? His pulse was revving up to 150 even when he was out cold. It wasn't until nearly 48 hours later that my husbands resting heart rate finally got below 100. Upon getting up it would rocket back into the 140's and 150's during this time.
All the doc could say is it was like something "wore off", after his heart rate finally went down.
Appointments and more tests are getting scheduled for next week (EEG,MRI). We are just still wondering what this could possibly even be while we wait. Until whatever happened to him gets identified I am still fearful that it could happen to him again at the drop of a hat like it did the first time.
I have panic attacks this sounds similiar to what i experienced.