Onuf’s nucleus is a distinct group of neurons located in the ventral part (laminae IX) of the anterior grey column of the sacral region of the human spinal cord involved in the maintenance of micturition and defecatory continence, as well as muscular contraction during orgasm. It contains motor neurons, and is the origin of the pudendal nerve.

Nerve fibres innervating the urethral and anal striated sphincters play an important role in the regulation of urinary and defaecatory continence. These fibres are derived from a group of neurons in the sacral spinal cord known as the Onuf's nucleus. Different neuron groups innervate the anal and urethral sphincter, and the nucleus uniquely demonstrates sexual dimorphism across different species ¹⁾.

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While working in New York City in 1899, Bronislaw Onuf-Onufrowicz discovered this group of unique cells and originally identified it as “Group X.” “Group X” was considered distinct by Onufrowicz because the cells were different in size from the surrounding neurons in the anterolateral group, suggesting that they were independent.

Neuronal degenerations secondary to vasospasm of artery of Adamkiewicz vasospasm induced Onuf's nucleus-pudental nerve ganglia complex degeneration may be a reason of urinary retention following spinal SAH ²⁾.