Objectives-To test whether the position of lumbosacral dermatomes vari
es in the presence of transitional vertebrae. Material and methods-Fif
ty consecutive male patients were tested for thoracolumbar and lumbosa
cral transitional vertebrae by radiography and for the position of the
dermatome gap between the lumbar dermatomes L1, L2, L3, and the sacra
l dermatomes S2 and S3. The dermatome gap was documented with the use
of the cremasteric reflex, the receptive field of which ends sharply a
t the gap which allows its delineation. Results-Thirty two of 50 patie
nts had a normal thoracolumbosacral spinal configuration, 10 patients
had transitional vertebrae. The patients with a cranial displacement o
f the thoracolumbar or lumbosacral vertebral transition showed a derma
tome gap which lay significantly more ventrally than in the patients w
ith a normal spinal configuration. Conclusion-The finding supports the
notion of a variant position of lumbosacral dermatomes in the presenc
e of transitional vertebrae in males.