How to Elicit the Bulbocavernosus Reflex (BCR)
The bulbocavernosus reflex is best elicited by squeezing the glans penis in males or clitoris in females and observing for contraction of the bulbocavernosus muscle, which can be palpated at the perineum.
Technique for Eliciting BCR
Male Patients
- Position: Place the patient in supine position with legs slightly abducted
- Stimulation method: Squeeze the glans penis or apply pressure to the dorsum of the penis 1
- Observation: Palpate for contraction of the bulbocavernosus muscle at the perineum
- Alternative method: Pull on a urethral catheter if one is present (though this activates a different pathway with longer transit time) 2
Female Patients
- Position: Place the patient in lithotomy or supine position with legs abducted
- Stimulation method: Apply pressure to the clitoris 1
- Observation: Palpate for contraction of the bulbocavernosus muscle at the perineum
- Alternative method: Transurethral electrical stimulation can be used in clinical settings where more reliable monitoring is needed 3
Clinical Pearls and Pitfalls
Important Considerations
- Bladder filling status: Ensure assessment at both empty and filled bladder states, as false negatives may occur with an empty bladder 4
- Response time: Normal latency is approximately 33.0±4.85 ms (range 26.8-39.4 ms) when measured electrophysiologically 5
- Documentation: Note whether the reflex is present, diminished, or absent
Clinical Significance
- The BCR assesses the integrity of S2-S4 spinal reflex arcs 1
- Present BCR with loss of voluntary control indicates an upper motor neuron lesion
- Absent BCR suggests a lower motor neuron lesion 1
- Helps distinguish conus medullaris from cauda equina syndromes
- Has prognostic implications for bowel, bladder, and sexual function 1
Common Errors
- Inadequate stimulation: Ensure sufficient pressure is applied to the glans penis or clitoris
- Improper palpation technique: Place fingers firmly along the perineal raphe to detect contraction
- Misinterpretation: Remember that different stimulation methods (penile squeeze vs. urethral stimulation) activate different pathways with different response times 2
- Testing only once: If initial testing is negative, repeat the test with the bladder filled, as this may improve detection 4
Advanced Assessment
For more precise evaluation in specialized settings:
- Electrophysiological testing can be performed using electrical stimulation of the dorsal nerve of the penis/clitoris
- Recording electrodes can be placed on the bulbocavernosus muscle to measure exact latency and amplitude 5
- Normal electrophysiological values: mean latency 33.0±4.85 ms, mean amplitude 16.53±12.21 μV 5
The bulbocavernosus reflex is an essential component of neurological examination in patients with suspected neurogenic bladder, bowel, or sexual dysfunction and should be routinely assessed in these populations.