Temporal and spatial variations in CSF pressure are influenced by electrical stimulation of the OCI muscles in beagles

Understanding cerebrospinal fluid (CSF) dynamics is crucial in the fields of neurosurgery and physiology. The myodural bridge (MDB), a dense connective tissue structure connecting the suboccipital muscles to the cervical spinal dura mater, has recently emerged as a novel regulatory component of the CSF dynamic system. Recent studies have shed light on its potential role in modulating CSF circulation, emphasizing the need to further investigate the underlying mechanisms by which the MDB influences CSF dynamics. The obliquus capitis inferior muscle is one of the suboccipital muscles. The main aim is to investigate the temporal and spatial variations in CSF pressure during electrical stimulation of the obliquus capitis inferior muscles. Thirteen anesthetized healthy Beagles were used. The pressure catheters were surgically implanted to monitor the pressure at four distinct locations: the right lateral ventricle pressure (LVP), the right frontal pole pressure (FPP), the right occipital pole pressure (OPP), and the lumbar subarachnoid pressure (LSP) between the L1 and L2 vertebrae. CSF pressure was recorded by the BL-420 F biological data acquisition and analysis system. One needle-electrode was inserted into the obliquus capitis inferior muscle, and electrical stimulation was applied on side. This comprehensive approach allowed for a detailed assessment of CSF pressure dynamics in response to the stimulation. During electrical stimulation, the CSF pressure exhibited significant spatial variations, with notable increases observed in the first peak of LVP, FPP, and OPP compared to baseline levels. Additionally, the plateau values of FPP, OPP, and LSP were significantly elevated. The mean pressure in these regions exhibited a mild increase during electrical stimulation. A statistically significant rise was only observed in FPP. Simultaneous monitoring of cranial and spinal CSF pressures revealed temporal changes in the propagation of pressure waves within the brain and subarachnoid space. Specifically, the first peak of intracranial CSF pressure occurred earlier than that in the lumbar subarachnoid space. Within the cranial cavity, the first peak time of OPP was the earliest, whereas that of FPP was the latest. The suboccipital muscles influence the occipital cistern through the MDB, generating pressure waves that spread through the subarachnoid space and the ventricles and maintaining local high pressure at frontal region. Pressure waves in the CSF diffuse from the occipito-atlantal cistern to the cranial cavity and spinal canal, following stable spatiotemporal patterns. This diffusion depends on anatomical structures and the distance from the occipito-atlantal cistern. This mechanism is one of the ways the MDB complex drives CSF circulation.