The cremasteric reflex evaluates the presence of a pyramidal track lesion.
The male patient is undressed sufficiently to expose his genitals. The cremasteric reflex can be performed either in the supine or standing positions.
Using a pointed but not sharp instrument, like the handle end of a swab stick, a brisk scratch-line line is drawn in the medial aspect of the thigh very close to the testicles.
A positive cremasteric reflex will not result in an ipsilateral contraction of the testis. This signifies an upper motor neurone in the pyramidal tracts, e.g. cauda equine syndrome, multiple sclerosis.
A negative cremasteric reflex will produce ipsilateral contraction visible in the scrotum or elevation of the same testis.
Factors affecting the cremasteric reflex include a cold environment. Also consider the possibility of an undescended testes.