Hi, I am new here.
What actually is a spasm? and is it the internal or the external levator muscle or both that spasms?
And what is LIS?
Thank you!

It is the internal sphincter that spasms, and we have no control over it. I think you are talking about proctalgia fugax, which I believe is somewhat different, though can happen with chronic fissures.
A spasm can last for minutes or hours. Having Sitz baths help to relieve this by expanding the blood vessels, thereby helping the fissure to heal. Lack of blood flow to the region is what messes us all up.
http://www.hemorrhoid.net/fissure.php

Hi,
Thank you for your reply, but still need to understand exactly what a spasm is, is it when the muscle contracts and wont relax or does it mean that is goes through contractions so it continually contracts and relaxes?
Also can you feel the internal muscle from the feeling around the anus. If I feel around my anus, the back and sides feel soft but the muscle close to my vagina feels very hard, but since I have been using a numbing cream I find that it has soften the muscle.
And please tell me what is LIS?

My understanding is that a spasm is when the muscles tighten up back there. I thought "spasm" meant like a pulse but I think it's just when the sphincter tightens up after a BM. If you ever lube up your bottom and you can't get a finger in there when you're in pain, it's spasming.
Also, LIS- Lateral Interior Sphincterectomy- the standard surgical procedure for these things. I hope this helps!

I am very grateful Ed : ) xx Thank you for your help, I am understanding a bit more about fissures every day x