The morphology of the suboccipital region in snakes, and the anatomical and functional diversity of the myodural bridge

Grondel, Bryson; Cramberg, Michael; Greer, Skye; Young, Bruce A.

doi:10.1002/jmor.21431

Cited by 7 publications

(5 citation statements)

References 41 publications

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“…[30] e myodural bridge of Alligator is well-developed, and contraction of the myodural bridge changes the CSF pressure. [39] ere continues to be debate regarding the functional role and significance of the myodural bridge; [12,23] two common hypotheses are that the myodural bridge functions to alter CSF pressure, or that it adjusts/regulates the dura. [13] e results of the present study support both these hypotheses; more specifically, our data suggest that the myodural bridge of Alligator is functioning to regulate the transition in dural compliance at the foramen magnum and that, by doing so, it plays a role in influencing the dynamics of CSF exchange between the cranial and spinal compartments.…”

Section: Discussionmentioning

confidence: 99%

Dynamic asymmetry in cerebrospinal fluid pressure: An indicator of regional differences in compliance

English¹,

Taylor²,

Cramberg³

et al. 2023

Surgical Neurology International

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Background: Dural compliance influences the shape and magnitude of the cerebrospinal fluid (CSF) pulsations. In humans, cranial compliance is approximately 2× greater than spinal compliance; the differential has been attributed to the associated vasculature. In alligators, the spinal cord is surrounded by a large venous sinus, which suggests that the spinal compartment may have higher compliance than is found in mammals. Methods: Pressure catheters were surgically implanted into the cranial and spinal subdural spaces of eight subadult American alligators (Alligator mississippiensis). The CSF was propelled through the subdural space by orthostatic gradients and rapid changes in linear acceleration. Results: CSF pressure recordings taken from the cranial compartment were consistently, and significantly, larger than those taken from the spinal compartment. After the myodural bridge of Alligator was surgically released, the asymmetry in CSF pressure was decreased. Conclusion: Unlike the situation in humans, the spinal compartment of Alligator has greater compliance than the cranial compartment, presumably due to the presence of the large spinal venous sinus surrounding the dura. The change in CSF pressures after myodural surgical release supports the hypothesis that the myodural bridge functions, at least in part, to modulate dural compliance and the exchange of CSF between the cranial and spinal compartments.

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Section: Discussionmentioning

confidence: 99%

Dynamic asymmetry in cerebrospinal fluid pressure: An indicator of regional differences in compliance

English¹,

Taylor²,

Cramberg³

et al. 2023

Surgical Neurology International

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“…The physical bases for these movement-induced CSF pulsations are not clear. Crocodylians have a well-developed myodural bridge, a link between cervical skeletal muscles and the dura 23 . These suboccipital muscles would likely be contracting during head rotations, and previous experimental studies on alligators have shown that contraction of the myodural bridge alters the CSF dynamics 16 .…”

Section: Discussionmentioning

confidence: 99%

Treadmill locomotion in the American alligator (Alligator mississippiensis) produces dynamic changes in intracranial cerebrospinal fluid pressure

Young

Cramberg

2022

Sci Rep

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To examine the influence of movement on cerebrospinal fluid (CSF) dynamics, intracranial subdural pressure recordings were taken from sub-adult alligators (Alligator mississippiensis) locomoting on a treadmill. Pressure recordings documenting the cardiac, ventilatory, and barostatic influences on the CSF were in good agreement with previous studies. During locomotion the CSF exhibits sinusoidal patterns of pressure change that spanned a mean amplitude of 56 mm Hg, some 16 × the amplitude of the cardiac-linked pulsations. These sinusoidal CSF pulsations were closely linked to the locomotor kinematics, particularly the lateral oscillations of the alligator’s head. Data recorded from the freely moving alligators suggest that fluid inertia, body cavity pressures, and likely other factors all influence the CSF pressure. The clear relationship between movement and CSF pressure described in this study suggests that the paucity of studies examining human CSF dynamics during movement should be addressed.

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“…Another key difference between manual tail oscillations and the oscillations of the body and head during locomotion, is the potential influence of the myodural bridge. The myodural bridge is a specialization of the suboccipital muscles in which muscle fibers insert onto the dura adjacent to the first cervical vertebra (the atlas) [ 63 ]. Though other functions have been proposed [ 64 ] there is a consensus that the myodural bridge could influence CSF dynamics during turning (oscillating) the head.…”

Section: Discussionmentioning

confidence: 99%

The Influence of Movement on the Cerebrospinal Fluid Pressure of the American Alligator (Alligator mississippiensis)

Young

Cramberg

2022

Biology

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This study was undertaken to document how the cerebrospinal fluid (CSF) pressure varied during movements and physiological activities. Using surgically implanted pressure catheters; the CSF pressure was recorded from sub-adult American alligators (Alligator mississippiensis) under anesthesia and post-recovery. Pressures were recorded during physiological activities (the cardiac cycle; passive and active ventilation); manual manipulation of the anesthetized animals (foot sweeps; tail oscillations; and body bends); as well as voluntary movements post-recovery (changes in body tone; defensive strikes; and locomotion). The CSF pulsations associated with the cardiac cycle had the lowest mean amplitude (3.7 mm Hg); during active ventilation and defensive strikes; the alligators routinely generated CSF pressure spikes in excess of 100 mm Hg. The recorded CSF pressures appear to be caused by a variety of mechanisms including vascular pressure; fluid inertia; and possible physical displacement of the spinal cord. The results of the study suggest that any model of CSF dynamics or perfusion should incorporate the episodic high-pressure CSF pulsations associated with movement

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The morphology of the suboccipital region in snakes, and the anatomical and functional diversity of the myodural bridge

Cited by 7 publications

References 41 publications

Dynamic asymmetry in cerebrospinal fluid pressure: An indicator of regional differences in compliance

Dynamic asymmetry in cerebrospinal fluid pressure: An indicator of regional differences in compliance

Treadmill locomotion in the American alligator (Alligator mississippiensis) produces dynamic changes in intracranial cerebrospinal fluid pressure

The Influence of Movement on the Cerebrospinal Fluid Pressure of the American Alligator (Alligator mississippiensis)

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