Morphological and morphometric characterisation of Onuf's nucleus in the spinal cord in man

Author(s): Pullen AH, Tucker D, Martin JE


In the absence of a systematic morphometric study of Onuf's nucleus in man, this investigation defines the limits of variation of segmental position and the range of length and volume of Onuf's nucleus in 6 normal humans displaying no neurological disease (2 males, 4 females). Serial section reconstruction methods in conjunction with the disector method provided information on the numbers, sizes and shapes of the constituent motor neurons of Onuf's nucleus. In contrast to previous descriptions, the cranial origin of Onuf's nucleus occurred in rostral S1 in 50% of subjects, and midcaudal S1 in the remaining subjects. Onuf's nucleus varied in length between 4 and 7 mm, and was 0.2-0.37 mm3 in volume. Differences in length or volume between males or females, or between the left and right side of the cord were not statistically significant. Neurons in Onuf's nucleus varied in diameter between 10 microns and 60 microns (mean 26 microns) and their mean number was 625 +/- 137. A higher density of neurons occurred at the cranial and caudal ends of the nucleus relative to the middle. While 37% of neurons were approximately spherical (shape index approximately 1), 44% were ellipsoid and 19% fusiform (shape indices varying between 0.26 and 0.8). These findings are compared with previous studies of Onuf's nucleus in man and animals. The results form a basis for further studies on Onuf's nucleus in normality and neurodegenerative diseases.

Similar Articles

Neuroanatomy of the striated muscular anal continence mechanism

Author(s): Matzel KE, Schmidt RA, Tanagho EA

Multi-MUP EMG analysis--a two year experience in daily clinical work

Author(s): Stålberg E, Falck B, Sonoo M, Stålberg S, Aström M

Standardization of anal sphincter EMG: technique of needle examination

Author(s): Podnar S, Rodi Z, Lukanovic A, Trsinar B, Vodusek DB

Injury to innervation of pelvic floor sphincter musculature in childbirth

Author(s): Snooks SJ, Setchell M, Swash M, Henry MM

Pelvic floor damage and childbirth: a neurophysiological study

Author(s): Allen RE, Hosker GL, Smith AR, Warrell DW

Anal-sphincter disruption during vaginal delivery

Author(s): Sultan AH, Kamm MA, Hudson CN, Thomas JM, Bartram CI

Anal function: effect of pregnancy and delivery

Author(s): Chaliha C, Sultan AH, Bland JM, Monga AK, Stanton SL

Age-associated changes in the monoaminergic innervation of rat lumbosacral spinal cord

Author(s): Ranson RN, Dodds AL, Smith MJ, Santer RM, Watson AH

Standardization of anal sphincter electromyography: normative data

Author(s): Podnar S, Vodusek DB, Stâlberg E