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  • Journal of Neurosurgery: Spine x
  • By Author: Arnold, Paul x
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Shawn B. Frost, Maria Iliakova, Caleb Dunham, Scott Barbay, Paul Arnold and Randolph J. Nudo


The purpose of the present study was to determine the feasibility of using a common laboratory rat strain for reliably locating cortical motor representations of the hindlimb.


Intracortical microstimulation techniques were used to derive detailed maps of the hindlimb motor representations in 6 adult Fischer-344 rats.


The organization of the hindlimb movement representation, while variable across individual rats in topographic detail, displayed several commonalities. The hindlimb representation was positioned posterior to the forelimb motor representation and posterolateral to the motor trunk representation. The areal extent of the hindlimb representation across the cortical surface averaged 2.00 ± 0.50 mm2. Superimposing individual maps revealed an overlapping area measuring 0.35 mm2, indicating that the location of the hindlimb representation can be predicted reliably based on stereotactic coordinates. Across the sample of rats, the hindlimb representation was found 1.25–3.75 mm posterior to the bregma, with an average center location approximately 2.6 mm posterior to the bregma. Likewise, the hindlimb representation was found 1–3.25 mm lateral to the midline, with an average center location approximately 2 mm lateral to the midline.


The location of the cortical hindlimb motor representation in Fischer-344 rats can be reliably located based on its stereotactic position posterior to the bregma and lateral to the longitudinal skull suture at midline. The ability to accurately predict the cortical localization of functional hindlimb territories in a rodent model is important, as such animal models are being increasingly used in the development of brain-computer interfaces for restoration of function after spinal cord injury.

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Christina L. Stephan, John J. Kepes, Paul Arnold, K. Douglas Green and Fran Chamberlin

✓ A case of a neurocytoma involving a nerve root of the cauda equina in a 46-year-old woman is reported. The patient presented with a 2-month history of progressive left lower-extremity weakness and pain and decreased ability to walk, as well as complaints of incomplete voiding. A magnetic resonance image revealed a 7-mm oval mass that was located intrathecally and extended from T-12 to L-1 and was adjacent to a nerve root. No lesions were identified at higher vertebral levels. The mass was excised. On histological examination it was found to have classical features of a neurocytoma. To the best of the authors' knowledge, this is the first report of a neurocytoma occurring in that region. A detailed histological description of this case and review of the pertinent literature are provided.