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On the occurrence of striated muscle within the spinal leptomeninges
Abstract:
A clinically normal adult male rabbit was found to possess fascicles of muscle fibers within the leptomeninges over the spinal cord at L6, L7, and S1. The finding is believed to be purely incidental and unrelated to any experimental procedure. Morphologically, the fascicles had the characteristics of striated muscle; and, while most were of normal dimensions, several were made up of small fibers 4-10 micron in diameter. Motor endplates, capillaries, and endomysial and perimysial connective tissue were also present. Axons myelinated by Schwann cells were associated with the normal bundles but were absent from the bundles of small fibers. In such bundles, large, unmyelinated axons predominated, some of which lacked ensheathment while others were invested by perineurial-type cells. The observation of incidental intraleptomeningeal skeletal muscle probably reflects a rare developmental anomaly. Its occurrence in humans is also discussed.
Insights
Intraleptomeningeal skeletal muscle fascicles were incidentally discovered in a rabbit's spinal cord. This rare finding, likely a developmental anomaly, involved both normal and small muscle fibers with unique axonal characteristics.
Area of Science:
- Veterinary Pathology
- Developmental Biology
- Neuroscience
Background:
- Intraleptomeningeal findings are rare in clinical veterinary neurology.
- Skeletal muscle typically resides outside the central nervous system's protective layers.
Purpose of the Study:
- To document and characterize incidental skeletal muscle fascicles found within the leptomeninges of a rabbit's spinal cord.
- To explore the potential developmental origins and implications of this anomaly.
Main Methods:
- Histopathological examination of spinal cord tissue from a clinically normal adult male rabbit.
- Morphological analysis of muscle fascicles, including fiber dimensions, associated vasculature, and neural elements.
- Microscopic assessment of axonal myelination and ensheathment.
Main Results:
- Discovery of striated muscle fiber fascicles within the leptomeninges at spinal cord levels L6-S1.
- Presence of both normal-sized and small (4-10 micron diameter) muscle fibers.
- Normal fascicles showed myelinated axons; small fiber fascicles contained predominantly large, unmyelinated axons, some lacking ensheathment.
Conclusions:
- The presence of intraleptomeningeal skeletal muscle is likely a rare developmental anomaly.
- The observed morphological variations in muscle fibers and associated axons suggest a complex developmental process.
- This finding warrants consideration for similar rare developmental anomalies in human medicine.