A spider in the brain

This is not literal. It's a mental image I get or impaired patients get who have a cluster of veins in the brain that have some kind of problem.

It can be caused by various issues impacting veins in the brain and if they are suffering mental illness, figuring out what is wrong and treating it can play a role in resolving their mental health issues.

I talked about this in unpublished drafts and someone at a mental health facility began doing brain scans and found several patients with vein issues in the brain.

Do a brain scan if you have crazy patients nattering on about spiders in their brain.

Ask them to describe the spider in detail. It may give you clues to what kind of problem they have. 

What color is it? 

Black is probably dead blood. Light brown may imply anemia or a condition reducing blood flow to that area, such as hardening of the arteries.

Is it dripping venom? This may mean a leak or some kind of "poisoning" happening.

A description suggesting it's hard may imply hardening of the arteries.

As the problem resolves, the spider may lose some of its legs one by one.

I also once read an article about an elderly woman with dementia who kept saying she had worms in her brain. No one took her seriously. After she died, an autopsy revealed a brain tumor, if I recall correctly.

Do a brain scan if crazy people tell you they have something running around in their brain, no matter how nonsensical it sounds.

It's like a medical Freudian Slip. They are TRYING to tell you what is wrong with them in spite of not being medically savvy and being highly mentally impaired because something is wrong with their brain.

There was a House episode where a nonverbal autistic child kept drawing squiggles because he had worms in his eyes.