There are sensors attached to my skull. More on my legs. Wires run to a device strapped to my chest. The bed is small and so is the room.
My brain activity is being tracked and monitored. I’m in a hospital for a sleep study. And despite all the sensors and wires, I start to drop off.
And then I hear it. It sounds like something has fallen. Not a body tumbling down a flight of stairs this time. More like a shelf giving way and books hitting the floor.
It lasts about a second. I know no one else can hear it. I know it isn’t real. It’s an auditory hallucination, a semi-regular event in the months after my concussion. It’s not scary or even surprising but I wonder if it might be an important clue about what’s going on inside my skull.
So I thrash my legs a bit and turn on my side, to mark the moment when I heard the books fall. I'm pleased. I think to myself that those who will analyze the data from my sleepover will be able to see on their reports when I moved and so know when I heard the sound that wasn’t there.
But no one cares.
I learn later that I’m having hypnagogic hallucinations. They are new to me but a lot of people experience brief sensations, including sound, when falling asleep. The hallucinations can trigger anxiety or, in extreme cases, injuries if people are startled and leap out of bed. Nothing like that happened to me.
After a few episodes, I became amused by the things that seemed to go bump and crash in the night. I was getting three a week for a while. I quickly learned to recognize them. Eventually, I am told this kind of brief hallucination, while not well understood, is usually considered harmless.
And my sleep study produced nothing of value.
After a blow to the head, it’s a good idea to report every symptom or issue to a doctor, of course. And I did that. But my little “sound bites”, to use a description from my broadcast career, gradually became less frequent and faded away almost completely as my recovery progressed.
I wish someone had mentioned hypnagogic hallucinations to me right after my injury. I didn’t fear them. But I got excited, thinking they could be a useful sign of something. I thought they might even put me on a treatment path that would lead to a faster recovery.
They were meaningless, I now know. And I also know that people with concussions have a bewildering variety of symptoms. If there is one thing that I have not stopped hearing for six years it is this phrase: “no two concussions are the same”.