A Life Without Fear - Urbach-Wiethe Disease (by Danielle Steinbach)
Jan 13, 2026One of the most finely tuned natural systems in the world is the human brain. Despite being such a finely tuned system, though, the human brain is astonishingly resilient to change. It’s one thing for a system to operate when all the typical pieces are in place, but it’s an extraordinary thing for a system to be able to adapt and pivot when something that was essential is removed. Our brains are that sort of miracle.
It doesn’t happen often, but case studies exist that record the behaviors of subjects lacking brain regions considered key in the history of our evolution. The amygdala, hippocampus, cerebellum, and corpus callosum – all of these are regions that contribute to critical aspects of the human experience. So what happens when a human must make do without them?
In this series, we’ll begin from the anterior of the brain and move posteriorly. First, we’ll learn about a woman denoted as S.M. who navigated life without an amygdala.
The amygdala creates the perception and experience of fear. Unless you’re Alex Honnold, you probably would not be willing to climb hundreds of feet into the air without a rope. You probably wouldn’t walk down a dark street in an unfamiliar area alone. You probably wouldn’t go kayaking off a waterfall.
People want to live without fear, but fear kept our ancestors alive.
And the loss of fear in S.M. only solidified how integral fear is to the human experience.
Carrying a mutation in the ECM1 gene, S.M. suffers from Urbach-Wiethe disease, which led to the disintegration of her amygdala. Calcium buildup in her amygdala led to the slow degradation of this fear hub in her brain, leading to a gradual change in her character that would be documented through a long-term case study.
Researchers underwent a series of trials attempting to initiate some sort of a fear response in S.M. Between being exposed to reptiles and spiders and watching frightening videos, S.M. never once exhibited a fear response.
What’s more, on the exterior, S.M. seemed entirely typical because she was entirely capable of processing and feeling the remainder of human emotions, from joy to sorrow to curiosity. She had not lost her ability to share the most joyous parts of the human experience with her loved ones.
However, one experience that S.M. cannot experience with her loved ones is that of shared fear. Indeed, S.M. does not only lack fear within herself, she also struggles with recognizing when those around her are afraid – the facial expression of fear is an image that her brain does not naturally interpret.
Once again, we can see evolution’s hand in this particular aspect of S.M.’s condition. Through centuries of relying on each other to survive–through famine and flood and fire–we humans think of each other as our mirrors, as extensions of ourselves that we need to live. Thus, in cases like S.M.’s when a loss of an emotion occurs, it is not uncommon for the brain to then lose the ability to see that emotion in others.
Although S.M. has gone on to live a life of laughter and joy with her three sons, she has also had more harrowing encounters than others around her throughout her life. Fear exists to tip off when you should turn around and retreat to safety. Without this sense of fear, on any day, S.M. could be walking on safe ground until suddenly she steps off the proverbial cliff without knowing. Over her life, S.M. has been mugged several times and remained in a physically abusive marriage partly because of her struggles associating danger with the primitive sense of fear.
However, it seems that S.M. has not lost all self-preservation instincts. Researchers had been trying relentlessly to trigger a fear response in her with no success. Trying to confirm if S.M. was indeed entirely devoid of the physiological fear response, those researchers investigated how S.M. reacted to inhaling large amounts of carbon dioxide, an experience that would result in her feeling like she was being asphyxiated. As S.M. detected the onset of this death zone, she became utterly terrified.
In S.M.’s brain–and, we can infer, the brains of most humans–there must thus exist a different region of the brain that can initiate fear as one is at the point of losing their life.
And that is the miracle of the human brain and why it has carried us through centuries of unimaginable circumstances. Even when you remove the part of the brain conditioned to predict danger and instill fear in us, you still cannot remove that most basic instinct–the will to live.
– Danielle Steinbach
Sources
https://www.science.org/content/article/fearless-woman-lacks-key-part-brain
https://www.bbc.com/future/article/20250924-the-rare-disease-that-stops-us-feeling-fear