Onuf's nucleus: Difference between revisions
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== Introduction == | == Introduction == | ||
Onuf's nucleus is a small group of motor neurons located in the anterior horn of the S2 segment of the spinal cord, specifically in Lamina IX. It is named after Bronislaw Onuf-Onufrowicz, a neurologist, who first discovered the structure in 1899. It is the site of origin of the pudendal nerve.<ref>Watson C, Kayalioglu G. Chapter 1: The Organization of the Spinal Cord. The Spinal Cord. 2009. DOI: 10.1016/B978-0-12-374247-6.50005-5</ref><ref name=":0">Mannen T. Neuropathology of Onuf's nucleus. Rinsho Shinkeigaku. 1991 Dec;31(12):1281-5. Review. PubMed PMID: 1817791.</ref> | Onuf's nucleus is a small group of motor neurons located in the anterior horn of the S2 segment of the spinal cord, specifically in Lamina IX. It is named after Bronislaw Onuf-Onufrowicz, a neurologist, who first discovered the structure in 1899. It is the site of origin of the pudendal nerve.<ref>Watson C, Kayalioglu G. Chapter 1: The Organization of the Spinal Cord. The Spinal Cord. 2009. DOI: 10.1016/B978-0-12-374247-6.50005-5</ref><ref name=":0">Mannen T. Neuropathology of Onuf's nucleus. Rinsho Shinkeigaku. 1991 Dec;31(12):1281-5. Review. PubMed PMID: 1817791.</ref> | ||
Revision as of 19:17, 12 February 2020
Introduction[edit | edit source]
Onuf's nucleus is a small group of motor neurons located in the anterior horn of the S2 segment of the spinal cord, specifically in Lamina IX. It is named after Bronislaw Onuf-Onufrowicz, a neurologist, who first discovered the structure in 1899. It is the site of origin of the pudendal nerve.[1][2]
Functions[edit | edit source]
Through the pudendal nerve, Onuf's nucleus innervates the external anal and urethral sphincters, as well as two perineal muscles: ischiocavernosus and bulbospongiosus. Hence, it maintains bowel and bladder continence through the voluntary control of both external sphincters and enables sexual functions like penile erection and ejaculation through perineal muscle contractions.[2][3]
In addition to its motor functions, Onuf's nucleus also performs autonomic functions by association with the parasympathetic neurons in the sacral segment of the spinal cord.[3]
Significance[edit | edit source]
Onuf's nucleus, interestingly, is the only motor neuron preserved in Amyotrophic Lateral Sclerosis. Additionally, it is also spared in Spinal Muscular Atrophy, Duchenne Muscular Dystrophy and Poliomyelitis. In stark contrast, it is the one of the most affected structures in Multiple System Atrophy.[2][3][4]
Therefore, the presence or absence of incontinence and/or impotence can allow the clinician to either rule in or out the possibility of the above conditions, from their differential diagnosis, subsequently saving a lot of time during clinical examination.
References[edit | edit source]
- ↑ Watson C, Kayalioglu G. Chapter 1: The Organization of the Spinal Cord. The Spinal Cord. 2009. DOI: 10.1016/B978-0-12-374247-6.50005-5
- ↑ 2.0 2.1 2.2 Mannen T. Neuropathology of Onuf's nucleus. Rinsho Shinkeigaku. 1991 Dec;31(12):1281-5. Review. PubMed PMID: 1817791.
- ↑ 3.0 3.1 3.2 Mannen T. Neuropathological findings of Onuf's nucleus and its significance. Neuropathology. 2000 Sep;20 Suppl:S30-3. Review. PubMed PMID: 11037184.
- ↑ Marani, Enrico. (2015). The nucleus of Onuf. 10.13140/RG.2.1.2253.0401.
