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The subdural space interpreted as a cellular layer of meninges
1Department of Basic Sciences, Bastyr College, Seattle, Washington.
Abstract:
The subdural region within the cranial meninges is examined in guinea pigs by electron microscopy. The fine structures of the arachnoid membrane and dura are described separately in specimens that have been isolated from each other during removal from the cranial cavity. In addition, the fine structure of the intact dura-arachnoid is described, where the subdural space would be present in an undisrupted state. Lastly, the inner surface of the dura and the outer surface of the arachnoid membrane are examined at the point of separation between the two specimens where the dura is reflected from the arachnoid by experimental dissection. From these observations morphologic criteria are established for identifying the constituents and boundaries of the subdural space and for explaining mechanisms in the histogenetic process of "opening" or enlarging this space. The morphologic identity of the classic subdural space is reinterpreted in light of the findings. The subdural space, traditionally described as a fluid-filled potential cavity existing in an extracellular compartment, is not apparent in the guinea pig. Instead, fragile cells designated as light cells occupy the compartment between the dura and arachnoid, with very little extracellular space available. Experimental opening of the subdural space occurs, significantly, along pathways extending by fracture through the cytoplasm and intercellular separation of these light cells rather than by enlargement of a preexisting mesothelial-lined intercellular space between these cells and the true arachnoid cells. Cytoplasmic fine structure of light cells suggests a close kinship with cells in the meningeal layer of the dura. The functional significance of the light cells and their possible role in subdural hematomas is discussed.
Insights
The subdural space in guinea pigs is not a fluid-filled cavity but is occupied by "light cells." Experimental opening of this space fractures these cells, not enlarges a preexisting cavity.
Area of Science:
- Neuroscience
- Histology
- Cell Biology
Background:
- The subdural space, a potential cavity between the dura mater and arachnoid mater, is traditionally viewed as a fluid-filled extracellular compartment.
- Its precise morphology and the mechanisms of its formation or enlargement have been subjects of ongoing investigation.
Purpose of the Study:
- To investigate the fine structure of the subdural region in guinea pigs using electron microscopy.
- To establish morphologic criteria for identifying the subdural space and understand the histogenetic processes involved in its enlargement.
- To reinterpret the morphologic identity of the classic subdural space based on new findings.
Main Methods:
- Electron microscopy was used to examine the subdural region in guinea pigs.
- Specimens included isolated dura and arachnoid membranes, intact dura-arachnoid structures, and experimentally dissected surfaces.
- Morphologic analysis focused on the inner dural surface, outer arachnoid surface, and the compartment between them.
Main Results:
- The subdural space in guinea pigs is not a fluid-filled potential cavity but is occupied by fragile cells termed "light cells."
- There is minimal extracellular space between the dura and arachnoid mater.
- Experimental opening of the subdural space occurs via fracture through the cytoplasm and intercellular separation of these light cells, not by enlarging a preexisting space.
Conclusions:
- The classic description of the subdural space as a fluid-filled extracellular compartment is reevaluated.
- "Light cells," with cytoplasmic features suggesting a dural origin, constitute the primary cellular element in the guinea pig subdural compartment.
- The findings provide insights into the mechanisms of subdural space formation and the potential role of light cells in conditions like subdural hematomas.