Science|Alzheimer’s Researchers Look at an Unusual Data Point: Head Shape

The illnesses that rob people of the ability to think, remember and create identity often begin, with pinpoint precision, in specific parts of the brain. It’s one of the biggest mysteries about brain diseases: Why do they start where they do?

Neuroscientists call this phenomenon, in which specific areas and cells in the brain are damaged by a disease while others are unaffected, “selective vulnerability.” Figuring out why it happens — and how to prevent or stop it — is a holy grail of the field.

Take Alzheimer’s, a disease that typically takes root years before memory unravels, when tangles of a protein called tau begin to accumulate and cells die off in a structure near the base of the brain called the entorhinal cortex.

In a preliminary study, scientists found that tau buildup in that origin area was linked to the progression of Alzheimer’s disease only when the region also lay close to the edge of the tentorial incisura, a notch in the brain’s outer lining.

This correlation prompts a series of unorthodox questions: Could the repeated mechanical stresses of everyday life, paired with the sag of gravity over a lifetime, create pressure points in the brain? And could that biomechanical wear and tear influence people’s risk of developing Alzheimer’s disease? And, as a result, could differences in the anatomy of a person’s head help explain why some people develop dementia and others do not?

“It really started in hushed tones in neuropathology circles,” said Dr. John Crary, a neuropathologist at the Icahn School of Medicine at Mount Sinai in New York, who partnered with Frank Provenzano, a neural imaging bioengineer at Columbia University, to test the idea in a small sample of 47 patients with mild cognitive impairment. Their paper was published in the journal Alzheimer’s & Dementia this month.