No difference in hippocampus volume detected on magnetic resonance imaging in autistic individuals.

Researchers used high-resolution MRI to measure the hippocampus in people with autism. They compared the scans to a control group without autism. The goal was to see if the memory center of the brain looked different in autism.

The MRI scans showed no size difference in the hippocampus between the two groups. Volume, shape, and symmetry all matched. In plain words, the hippocampus looks the same in autism.

Laidi et al. (2019) later found thinner cortex in the anterior cingulate of autistic adults. That study used the same MRI tool but looked at a different brain area. The two papers do not fight each other; they simply map different neighborhoods.

Marcell et al. (1988) used older CT scans and also found no cerebellar or hemispheric differences. Bromley et al. (1998) repeats that null result with sharper MRI, giving the field more confidence.

Porter et al. (2008) and Lancioni et al. (2008) tested blood and spinal-fluid markers and also came up empty. Together these papers build a stack of evidence that single biological measures rarely separate autism from controls.

You can stop telling families that a smaller hippocampus causes autism. When medical providers ask for brain-based proof, point them to this clean null finding. Save your energy for behavioral assessment and skill-building, not hunting for hidden hippocampal problems.