Medical Terminology Daily (MTD) is a blog sponsored by Clinical Anatomy Associates, Inc. as a service to the medical community, medical students, and the medical industry. We will post a workweek daily medical or surgical term, its meaning and usage, as well as biographical notes on anatomists, surgeons, and researchers through the ages. Be warned that some of the images used depict human anatomical specimens.

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A Moment in History

Thomas Willis, MD
Thomas Willis

An English physician and anatomist, Willis was born on his parents' farm in Great Bedwyn, Wiltshire, where his father held the stewardship of the Manor. He was a kinsman of the Willys baronets of Fen Ditton, Cambridgeshire. He graduated M.A. from Christ Church, Oxford in 1642. In the Civil War years he was a royalist, and was dispossessed of the family farm at North Hinksey by Parliamentary forces. In the 1640's Willis was one of the royal physicians to Charles I of England. He obtained his medical degree in 1646.

Thomas Willis might well be one of the greatest physicians of the 17th century.He is one of the founders of the Royal Society of London. He is remembered by his many publications, especially "Cerebri Anatome: Cui accessit Nervorum Descriptio et Usu", where he describes the arterial anastomoses at the base of the brain. This work is also the first detailed description of the vasculature of the brain. Willis described nine cranial nerves.

He is considered as the father of Neurology as a discipline. He used the term "neurology" for the first time in 1664. He described several neurological conditions

The Arterial Circle of Willis is a famous eponymous structure found at the base of the brain. It represents an anastomotic roundabout that connects the right and left sides as well as the carotid and vertebral arterial territories that supply the brain. Named after Thomas Willis, this structure was known well before him, but it was Willis who described its function.  If you click on the image or here, you will be redirected to a detailed description of this structure.


1. "The legendary contributions of Thomas Willis (1621-1675): the arterial circle and beyond" Rengachary SS et al J Neurosurg. 2008 Oct;109(4):765-75
2. "Thomas Willis, a pioneer in translational research in anatomy (on the 350th anniversary of Cerebri anatome)" Arraez-AybarJournal of Anatomy, 03/2015, Volume 226, Issue 3
3. " The naming of the cranial nerves: A historical review" Davis, M Clinical Anatomy, 01/2014, Volume 27, Issue 1
4. "Observations on the history of the circle of Willis". Meyer A, Hieros, R.Med Hist 6:119–130, 1962

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[UPDATED] The word is derived from the Greek; the prefix [hydr-] [υδρος]means "water", while the root term [-cephal-] means "head".  The term [hydrocephalus] means "water in the head"; of course the "water" is cerebrospinal fluid (CSF) which accumulates excessively in the ventricular system of the brain

There are several reasons why the amount of CSF within the brain can be excessive, increasing the intracranial pressure: An imbalance between production and absorption of CSF (excessive production or reduced absorption), or a blockage in the ventricular system causing a dilation of the ventricles. The excessive pressure can and will damage the delicate brain tissue. In the case of hydrocephaly (another form of the term) in a newborn the soft cartilage between the cranial bones will distend allowing for the head to dilate and reduce the damage to the brain tissues. A hydrocephalus shunt can allow the patient to reduce the size of the head and eventually lead a normal life.

Ventricular system of the brain (www.bartleby.com)
Initial image courtesy of: www.bartleby.com
Secondary image courtesy of: www.Wikipedia.org

 In 1964 Dr. Salom?n Hakim described, in what was then considered a controversial publication, a condition known as "normal pressure hydrocephalus", usually associated with old-age, Alzheimer's and Parkinson's disease. This condition is now widely accepted as a specific type of hydrocephalus.

The image depicts the ventricular system of the brain in a normal state. If you click on the image, a secondary image of a hydrocephalic baby courtesy of Wikipedia will appear. WARNING! This image is potentially disturbing. For a YouTube video of the insertion of a CSF shunt into the brain, click here.