1128 The Controversial Contributions of Alexander Monro Secundus

INTRODUCTION: Alexander Monro Secundus is the second of three generations in the Monro lineage to serve as the Chair of Anatomy at the University of Edinburgh. Of his many contributions, the most notable include his description of the interventricular foramen and his hypothesis which contributed to the Monro-Kellie Doctrine. METHODS: A literature review on Alexander Monro Secundus’ key contributions to human anatomy and physiology was performed. RESULTS: The results of the literature review are summarized in the Conclusions section. CONCLUSIONS: Controversy surrounds the claims of Monro Secundus’ description of what is known today as the foramen of Monro. Although the interventricular foramen had been known by Galen 1500 years prior to Monro Secundus’ description of it, Monro Secundus claimed to have been the first to describe it in such detail. However, Monro Secundus’s description of the interventricular foramen was incorrect, as he indicated that the two interventricular foramina join each other to make a canal in which a third foramen exists which leads to the third ventricle. The Monro-Kellie doctrine established a relationship between intracranial pressure and the volumes of the brain, CSF, and intracranial blood. In 1783, he published Oberservations on the Structure and Functions of the Nervous System, in which, he established the baseline for what is now widely known as the Monroe-Kellie doctrine when he described the brain as “nearly incompressible, the quantity of blood within the head must remain the same.” His former student, George Kellie, then hypothesized that the total content of the skull (blood, CSF, and brain tissue) exist within a state of equilibrium. Today, this association is used in clinical practice to identify the origin of decompensation, or increased intracranial pressure, in patients with traumatic brain injury.