When a man visited a French hospital complaining of a weak leg in 2007, Dr. Lionel Feuillet ordered him a CT scan and an MRI. The patient, a 44-year-old father, seemed otherwise normal. But when the test results came in, Feuillet was shocked: The man didn’t have a brain.

At least, that’s what it looked like. It turned out the man had hydrocephalus, a condition of unknown causes in which cerebrospinal fluid fills the chambers inside the brain and squashes brain matter against the cranium. In 1980, neurologist John Lorber wrote about a similar case involving a patient with honors in mathematics, an IQ of 126, and “virtually no brain.” His brain was incredibly thin—up to 75 percent smaller than normal.

Lorber has studied more than 600 such patients. While many were disabled, others touted IQs over 100. It just goes to show that the brain has an amazing power to rebound from slow-evolving injuries. In other words, gray matter matters.

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