LIMA, Peru -- Pointing to one of the four natural holes we all carry in our brains, Dr. Diana Rivas explained why some of her patients get headaches only when they move their heads to one side.
She suggests the reason is that parasites camped out in the ventricles bump up against the gray matter only some of the time.
The brain Rivas showed is one of 2,786 at the Neurological Sciences Institute's brain museum, a resource for generations of Peruvian medical students and a popular stop for foreign physicians since brain collecting began in 1947.
"The foreign doctors come to see some of the diseases we have here that aren't so common in other parts of the world," said Dr. Adriana Ciudad, who serves as museum curator.
She says it's Latin America's largest collection of diseased brains.
For those unable to make it to Peru, images of about 700 of the museum's brains will go online in late August. The Web launch coincides with the 302nd anniversary of the institute, which is a short cab ride from Lima's historic Plaza Mayor in the poor, decrepit Barrios Altos district.
In the museum's 10-by-10-foot display room, 230 brains fill lunchbox-sized glass cases of formaldehyde on shelves that run from floor to ceiling along three walls. High in the center of the middle wall hangs an oil painting of Dr. Oscar Trelles, the father of Peruvian neuroscience.
An adjoining "brain library" holds the museum's remaining specimens in 2-liter glass jars of formaldehyde on three shelved walls.
One specimen feared
Rivas' favorite specimen is the one with Creutzfeldt-Jakob disease -- the human form of "mad cow" disease. When medical students dissected it a few months ago, they had to cover the lab with plastic sheeting and don "astronaut" gear to handle the brain, despite its having spent a month in formaldehyde.
"The prion proteins that cause the disease are microscopic and extremely resilient," Rivas said. "Everyone is afraid of that one."
Other preserved brains at the museum have been attacked by amoebas, fungi, meningitis, tuberculosis and 36 types of brain cancer.
In addition to tending the displays, Ciudad leads medical students in weekly dissections in an adjacent lab.
Following a 15-minute review of a patient's medical file, a dozen students correctly diagnosed the museum's most popular specimen -- cysticercosis, a non-intestinal infection caused by pork tapeworm larvae.
Unchecked, the parasites can grow in the brain, leaving it riddled with pencil-wide holes. As with about 40 of the annual student dissections, the diagnosed brain made the museum's collection.
What made this example worthy of inclusion, Rivas pointed out, was the unusual location of the parasite: inside one of the four natural holes, or ventricles, that we all carry around inside of our brains.