Abstract
Simple SummaryThe cerebrospinal fluid (CSF) flows through and around the central nervous system to nourish, cleanse, and support the brain and spinal cord. Though abnormalities of this CSF flow have been linked to multiple human neural diseases, little is known about the underlying mechanics of CSF flow. This study was designed to test the hypothesis that movement of the body’s trunk could cause CSF flow; hence, the study was conducted on a snake, an animal with prominent trunk movement. The results demonstrate that the resting snake has a CSF pressure profile that is very similar to what is seen in humans and other mammals, and that the CSF dynamics are changed during either artificial (manual) or natural (locomotor) movement of the snake’s bodyIn the viper boa (Candoia aspera), the cerebrospinal fluid (CSF) shows two stable overlapping patterns of pulsations: low-frequency (0.08 Hz) pulses with a mean amplitude of 4.1 mmHg that correspond to the ventilatory cycle, and higher-frequency (0.66 Hz) pulses with a mean amplitude of 1.2 mmHg that correspond to the cardiac cycle. Manual oscillations of anesthetized C. aspera induced propagating sinusoidal body waves. These waves resulted in a different pattern of CSF pulsations with frequencies corresponding to the displacement frequency of the body and with amplitudes greater than those of the cardiac or ventilatory cycles. After recovery from anesthesia, the snakes moved independently using lateral undulation and concertina locomotion. The episodes of lateral undulation produced similar influences on the CSF pressure as were observed during the manual oscillations, though the induced CSF pulsations were of lower amplitude during lateral undulation. No impact on the CSF was found while C. aspera was performing concertina locomotion. The relationship between the propagation of the body and the CSF pulsations suggests that the body movements produce an impulse on the spinal CSF.
Highlights
Perspectives on the cerebrospinal fluid (CSF) have changed; what once was seen as an almost “passive” supporting substance is generally seen as a dynamic system, perturbations of which can cause a number of neural disorders [1,2]
In humans and other mammals, the cardiac cycle and ensuing arterial pulsations have the greatest influence on CSF pulsations [4], while the ventilatory cycle has the greatest influence on CSF flow [5]
The purpose of this study is to explore the CSF dynamics in the viper boa, Candoia aspera
Summary
Perspectives on the cerebrospinal fluid (CSF) have changed; what once was seen as an almost “passive” supporting substance is generally seen as a dynamic system, perturbations of which can cause a number of neural disorders [1,2]. A recent study on the American alligator (Alligator mississippiensis) revealed that this mammalian pattern is not universal; in the alligator, there are both cardiac and ventilatory influences on the CSF, but they are far more variable than what has been reported from any mammal [6]. The basis for this variation is unknown; compared to mammals, both the cardiac output [7,8] and ventilatory cycle [9,10] of the alligator are actively variable. Alligators have a diaphragm capable of sustaining transdiaphragmatic pressures [19], and can ventilate through costal displacement [20], but little is known about how the variation in intrathoracic pressure in Alligator influences central venous pressure or CSF flow dynamics
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