Student Guest Post: Caitlin Smith on Spina Bifida
During the fall semester (Sept-Dec 2018), students from Bryn Mawr and Haverford helped to clean and catalog the remains at Rutgers-Camden as part of a praxis course led by Professor Maja Šešelj. The following post if from one such student --- Bryn Mawr student Caitlin Smith. Caitlin Smith is a senior at Bryn Mawr College who is majoring in anthropology with a thesis research focus in bioarchaeology.
Spina Bifida in the Arch Street Population
By Caitlin Smith, Bryn Mawr College
When we study bones, we can look for signs of conditions that affect people in the long term. Whether from a birth defect, a disease, or simply individual variation, we are able to diagnose individuals from the past when they show evidence of the specific changes a particular condition leaves on or in bones. We are limited by what we can study in the bioarchaeological record by the fact our primary source of information are bones, as soft tissue is not preserved, but what we can observe provides us with valuable information about the lives of those individuals.
One of those conditions is spina bifida, a relatively rare birth defect where the bones do not grow completely around the spinal cord. Spina bifida is considered a neural tube defect since it begins during development in utero and is present at birth. Today, we know that the chances of a child developing spina bifida can be reduced by a maternal diet high in folic acid - a B vitamin - during pregnancy. However, this cannot and does not prevent all instances of spina bifida, so it affects between 1,500 to 2,000 babies born in the United States every year (1).
Spina bifida has a long history, with bioarchaeologists finding remains with evidence of the condition from as early as 7,500 years ago (2). We even have the remains of individuals who had spina bifida among the salvaged remains from the First Baptist Church of Philadelphia cemetery. As part of the osteological analysis (analysis of the bones), noting that some individuals had conditions like spina bifida helps us to reconstruct their lives.
In at least two of the individuals from Arch Street whose remains are housed at Rutgers University-Camden, we can see evidence of mild and moderate spina bifida in the sacrum. The sacrum is the bone just below the vertebral or spinal column (colloquially known as “the spine”), located in the center of the back part of the pelvis. A modern human typically has five sacral vertebrae that fuse during adolescence to form a single, triangular bone. When the vertebral arches along the back of the sacrum are not fully closed, they are considered to show evidence of spina bifida. The bone appears to flare out along a vertical line from the center of the sacrum, leaving a visible gap where the lowest part of the spinal cord (technically, the “cauda equina" or “horse’s tail”, a bundle of spinal nerves as opposed to a more compact spinal cord that runs through most of the vertebral column before thinning out into this bundle of nerve fibers) would have then been exposed. The severity varies, from just one segment of the sacrum not being fully closed, to the entire back of the sacrum being open in this manner. We can observe this variation in severity in two individuals from Arch Street with one exhibiting very mild spina bifida, and the other one (pictured in this post) showing fully open neural arches along the entire length of the sacrum.
Today, spina bifida can be diagnosed in living humans with X-rays or other imaging, but for those individuals living in the 18th or early 19th century Philadelphia, they might not have even known that they had it, if it was not causing any symptoms. This is because they likely had the milder form of the defect, called spina bifida occulta, where the skin and connective tissue fully covers the affected area (3). Other forms of spina bifida are more severe, with a potentially significant impact on mobility and function, and a historically lower rate of survival (4). While spina bifida occulta can cause symptoms like nerve damage or weakness in the limbs, in mild forms it does not require any additional medical intervention. Given that both individuals from Arch Street were adults at the time of their deaths, we know that the symptoms of their spina bifida were manageable enough that they were able to survive into adulthood. The size and shape of their sacra is also comparable to individuals with typical levels of lower limb mobility, suggesting that that their symptoms were most likely minor, or (in the milder version) they could have been completely asymptomatic.
As is part of our study of the skeletal remains from Arch Street, the presence of spina bifida is recorded as a pathology in the biological profiles we are making for each individual. These are descriptive documents that provide our estimates of the individuals’ age, sex, ancestry, stature, and presence of any pathology or trauma, written as the remains are analyzed in the lab. The goal of the biological profile is to reconstruct the identity of a person as they would have been recognized during life, and understanding conditions that may have impacted their quality of life is an important part of that process, especially for conditions that may have gone unrecognized or unreported during their lives.
(1) Spina Bifida Fact Sheet. National Institute of Neurological Disorders and Stroke. https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Fact-Sheets/Spina-Bifida-Fact-Sheet
(2) Dickel, D.N. and Doran, G.H. “Severe Neural Tube Defect Syndrome From the Early Archaic of Florida”. American Journal of Physical Anthropology 80:325-334. (1989)
(3) What is Spina Bifida? Centers for Disease Control and Prevention. https://www.cdc.gov/ncbddd/spinabifida/facts.html
(4) Spina Bifida, Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/spina-bifida/symptoms-causes/syc-20377860