Bones Variation
Accessory ossicles
Small extra bones, most often in the foot, that form when a growth centre never fuses with its main bone. They are harmless but can be mistaken for fractures on an X-ray.
Up to 1 in 5 feet
Not an emergency
20 oddities.
Spiritual 6Icky 4Not an emergency 20Get it checked 14Try it 62Learnable 20Party trick 19Vestigial 7Genetic 35Sleep 6Illusion 21Childhood 10Debunked myth 11Community 13Famous people 14Record 7
Brain Perception
Alice in Wonderland syndrome
Objects, body parts, or the whole room suddenly look far too big, far too small, or far away. It mostly happens to children, often during a fever or infection, and it passes on its own. In adults it is usually linked to migraine.
6–7% of teenagers (size distortion)
Muscle Involuntary
Benign fasciculations
Small visible twitches in the eyelid, calf, thumb, or arm that come and go with no weakness. About 70% of healthy people get them. They are not a sign of nerve disease.
About 70% of healthy people
Brain Involuntary
Brain zaps
A brief feeling like a small electric shock inside the head, often set off by moving the eyes. It is most common when stopping or lowering an antidepressant. It is unpleasant but not dangerous.
Common when stopping antidepressants
Brain Involuntary
Call of the void
A sudden, brief thought of jumping when you stand somewhere high, or of swerving while driving, with no wish to do it. About half of people get it. It is the brain's safety system being misread, not a hidden wish.
43–60% of people
Bones Variation
Cervical rib
An extra rib above the normal top rib, growing from the lowest bone in the neck. About 1 in 100 people have one, and most never know.
About 1% of people
Brain Perception
Charles Bonnet syndrome
People who lose a lot of their sight often start to see things that are not there: patterns, faces, small people in costume, whole landscapes. They know the images are not real. It is caused by the eyes, not the mind.
10–40% of people with serious sight loss
Brain Involuntary
Derealization and depersonalization
The world suddenly seems flat, distant, or like a film (derealization), or you feel like you are watching yourself from outside (depersonalization). Most people have a brief episode at some point, usually under stress.
50–75% of people, at least once
Muscle Variation
Diastasis recti
A widening of the gap between the two halves of the six-pack muscle, seen in nearly every pregnancy and in some men. A bulge down the midline when you sit up is the usual sign.
Almost all pregnancies; about 1 in 3 women a year after birth
Brain Involuntary
Exploding head syndrome
A loud bang, crash, or explosion heard inside the head while falling asleep or waking up. Nothing actually happens, there is no pain, and it is harmless.
10–37% of people, lifetime
Skin Involuntary
Fordyce spots
Tiny pale yellow or white bumps, 1 to 3 mm across, on the edge of the lips or inside the cheeks. They are ordinary oil glands in a place without hair. Most adults have them.
70–80% of adults
Mouth Variation
Geographic tongue
Smooth red patches with pale borders that form a map on the tongue and move around over days and weeks. About 1 to 3% of people have it, and it is harmless.
1–3% of people
Brain Involuntary
Hypnagogic hallucinations
Vivid images, sounds, or touches that appear while you are falling asleep or waking up. A face, a voice saying your name, a hand on your shoulder. They are dream fragments arriving early or late, and they are normal.
About 25–37% of people
Brain Involuntary
Hypnic jerks
A sudden jolt of the arms, legs, or whole body just as you fall asleep, often with a feeling of falling. Most people get them, and they are harmless.
60–70% of people
Nerves Involuntary
Precordial catch syndrome
A sudden, sharp, stabbing pain near the heart that lasts seconds to a few minutes and gets worse when you breathe in. It is the most common cause of chest pain in children and teenagers, and it is harmless.
Most chest pain in ages 6–20
Heart Involuntary
Seeing stars when standing up
You stand up fast, your vision goes grey or sparkly, and your head feels light for a few seconds. Blood has briefly pooled in your legs. It passes on its own.
Almost everyone, at some time
Brain Involuntary
Sleep paralysis
You wake up, or start to fall asleep, and cannot move or speak for a few seconds to minutes. Sometimes a threatening presence seems to be in the room. It is the normal paralysis of dreaming sleep running a little late.
8–30% of people, lifetime
Skin Variation
Supernumerary nipples
An extra nipple, usually small and flat, on a line running from the armpit to the groin. Between 1 in 500 and 1 in 18 people have one, and most think it is a mole.
0.2–5.6% of people
Bones Variation
Torus palatinus
A hard bony lump along the midline of the roof of the mouth that grows slowly and is completely harmless. Many people find it by chance and worry that it is a tumour.
About 20% of people
Heart Reflex
Vasovagal syncope
The most common reason people faint. A trigger like blood, pain, heat, or standing too long makes the vagus nerve slow the heart and drop blood pressure. The brain briefly runs short of blood and you go down.
About 4 in 10 people faint at least once