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INTRODUCTION:The gastrulation brain homeobox (Gbx) genes are essential for patterning and maintenance of neurons along the anteroposterior axis of the developing neural tube. Knockout (ko) of Gbx2 results in neonatal lethality associated with neurological and other defects. To understand pathologies, ko studies are not realistic as gene loss usually results in death before birth. Gbx2 neo/neo mutant mice express 6-10% of the wildtype Gbx2 expression levels. They have milder malformations than ko mice but lack the cerebellar vermis and mandibular division of the trigeminal nerve (3rd division of 5th cranial nerve = V3), among other defects. These Gbx2 neo/neo mutant mice die perinatally as they are unable to suckle due to lack of motor innervation via V3 to the muscles of mastication. Muscle cells develop largely without interaction with their motor nerve. However, the final differentiation of myocytes requires interactions with nerve fibers. Unexpectedly, the muscles of mastication appear normal in Gbx2 neo/neo mutant mice, despite the lack of V3. METHODS:We performed microdissections of neonate wildtype and Gbx2neo/neo mutant mice. Additionally, we embedded mutant and wildtype mouse embryos in paraffin, serial sectioned them (7 μm), stained the sections with Azan staining, and analyzed specimen microscopically. RESULTS:Current analysis of the data to identify where nerve fibers in the muscles of mastication originate is in process. We favor the origin of these fibers from the facial nerve (7th cranial nerve), which has several overlapping territories with the trigeminal nerve. CONCLUSIONS:Muscles require innervation for their final differentiation steps. The loss of a nerve can result in the invasion of another nerve into the territory of the lost one, which rescues muscle differentiation but not muscle function. IACUC Ziermann Med-20-02, Funding NSF #2000005 to Ziermann.
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This content will become publicly available on September 1, 2026
Intraoperative blink reflex monitoring during skull base surgery: a single-institution method
OBJECTIVECranial nerve (CN) preservation remains a challenge for skull base neurosurgeons, and neurophysiological intraoperative monitoring presents many methods for CN identification and mapping. The blink reflex, which is the electrophysiological representation of the corneal reflex, can be used to test both trigeminal and facial nerve function. The objective of this study was to present a method for obtaining a reliable blink reflex response and maintaining it during the course of a procedure. METHODSA method for robust blink reflex recording is presented. Electrode placement, recording parameters, stimulation parameters, anesthetic considerations, and reliability troubleshooting are described. RESULTSThis method has been iteratively developed at the authors’ institution across multiple sites for more than 5 years. The blink reflex was monitored in multiple cranial approaches and for various pathologies. The most common cases monitored were vestibular schwannoma resections and microvascular decompressions. The most common cranial approaches were the translabyrinthine, retrosigmoid/suboccipital, and middle cranial fossa approaches. CONCLUSIONSTo gain a more comprehensive understanding of the clinical utility of the blink reflex in surgical decision-making and outcome prediction, prospective studies involving larger patient cohorts are warranted. This report outlines a reproducible methodology and invites validation and constructive input from the broader neurosurgical and neuromonitoring communities.
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- Award ID(s):
- 2125528
- PAR ID:
- 10651538
- Publisher / Repository:
- American Association of Neurological Surgeons
- Date Published:
- Journal Name:
- Neurosurgical Focus
- Volume:
- 59
- Issue:
- 3
- ISSN:
- 1092-0684
- Page Range / eLocation ID:
- E18
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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