Sacral reflex latencies in tethered cord syndrome

We performed electrophysiologic evaluation in three adult patients with diagnosis of tethered cord syndrome confirmed by magnetic resonance imaging. In addition to lower motor neuron lesion signs in the lumbar and sacral myomeres we noticed shortened latencies for the H and bulbocavernosus reflexes. H reflex latencies ranged from 23.3 to 26.0 ms; bulbocavernosus reflex latencies ranged from 18.2 to 20.2 ms. The low location of the conus medullaris accounts for the shortening of the monosynaptic H reflex and for a part of the shortening of the polysynaptic bulbocavernosus reflex, anoxia of the conus being probably another important factor. In the absence of previous description of alternative pathology accountable for such a shortening, our observations suggest that shortened sacral reflex latencies might be specific of the tethered cord syndrome.