Bulbocavernosus reflex

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The bulbocavernosus reflex (BCR), bulbospongiosus reflex (BSR) or "Osinski reflex" is a polysynaptic reflex that is useful in testing for spinal shock and gaining information about the state of spinal cord injuries (SCI). Bulbocavernosus is an older term for bulbospongiosus, thus this reflex may also be referred to as the bulbospongiosus reflex.


The test involves monitoring internal/external anal sphincter contraction in response to squeezing the glans penis or clitoris, or tugging on an indwelling Foley catheter. This reflex can also be tested electrophysiologically, by stimulating the penis or vulva and recording from the anal sphincter. This testing modality is used in intraoperative neurophysiology monitoring to verify the function of sensory and motor sacral roots as well as the conus medullaris.[1]


The reflex is spinal mediated and involves S2-S4. The absence of the reflex in a person with acute paralysis from trauma indicates spinal shock whereas the presence of the reflex would indicate spinal cord severance. Typically this is one of the first reflexes to return after spinal shock. Lack of motor and sensory function after the reflex has returned indicates complete SCI. Absence of this reflex in instances where spinal shock is not suspected could indicate a lesion or injury of the conus medullaris or sacral nerve roots.

There is an association between hyperexcitable bulbocavernosus reflex resulting from stimulation of the prostatic urethra and premature ejaculation.[2] The bulbocavernosus reflex has been found to be delayed or absent at a higher rate than the general population in diabetic men with complaints of erectile impotence,[3] and men whose penises have been circumcised or have permanent retraction of the foreskin behind the glans penis.[4]


  1. ^ Vodusek, David B.; Deletis, Vedran (2002). "Intraoperative Neurophysiological Monitoring of the Sacral Nervous System". Neurophysiology in Neurosurgery, A Modern Intraoperative Approach: 153–165.
  2. ^ Jiang XZ; Zhou CK; Guo LH; Chen J; Wang HQ; Zhang DQ; Shi BK; Xu ZS. (2009). "Role of bulbocavernosus reflex to stimulation of prostatic urethra in pathologic mechanism of primary premature ejaculation". Zhonghua Yi Xue Za Zhi (in Chinese). 89 (46): 3249–52. PMID 20193361.
  3. ^ Y Sarica; I Karacan (1987). "Bulbocavernosus reflex to somatic and visceral nerve stimulation in normal subjects and in diabetics with erectile impotence". Journal of Urology. 138 (1): 55–58. doi:10.1016/S0022-5347(17)42987-9. PMID 3599220.
  4. ^ Podnar S (2012). "Clinical elicitation of the penilo-cavernosus reflex in circumcised men". BJU Int. 209: 582–5. doi:10.1111/j.1464-410X.2011.10364.x. PMID 21883821.