Storms, hanged pirates, anemia, exsanguination: the contributions of Monro, Kellie and Abercrombie in understanding intracranial blood circulation

Abstract

The so-called Monro-Kellie doctrine states that with an intact skull, the sum of the volume of the brain plus the cerebrospinal fluid volume plus the intracranial blood volume is constant. Therefore an increase in one should cause a reduction in one or both of the remaining two. The researcher who expressed the doctrine in such a way was indeed Harvey Cushing in 1925, during a lecture in Edinburgh. The original Monro-Kellie doctrine is the result of observations on autopsies and several animal experiments. What the original doctrine states is a dynamic explanation of the intracranial system, aimed at explaining how a pulsatile and continuous perfusion may occur in a closed-non-expandable and fully filled system. During each cardiac cycle the quantity of blood within the head must be the same: during the systole, the brain arteries dilate, and, in the mean time, a quantity of blood, equal to that which is dilating them, is passing out of the head through the veins. During the succeeding diastole, the quantity which dilated the brain arteries passes into the corresponding veins and, at the same time, as much passes from the sinuses out of the head, as enters into the head from the arteries situated between the heart and the head. Monro implicitly states that the blood coming out from the cerebral veins into the sinuses must be pulsatile and (almost) synchronous with the arteries. That is deeply different from the concept of a constant content of a rigid case, as expressed by Cushing

Neurosurgical implications of the Jugular Vein Nutcracker

“…7 Therefore, Monro stated that the venous outflow of the intracranial system is pulsatile and almost synchronous with arterial pulsations. 8 The blood enters the skull pulsating into the arteries, the mechanical wave of pulsation is transmitted through parenchyma and CSF over the bridging veins, then the blood leaves the skull N o n -c o m m e r c i a l u s e o n l y pulsating into the extracranial veins (dural sinuses). Eagle's Syndrome (ES) refers to a rare group of neuropathic and vascular symptoms caused by abnormal elongation or angulation of the styloid process.…”