Dorello canal revisited: an observation that potentially explains the frequency of abducens nerve injury after head injury.

Abstract

The abducens nerve is frequently injured after head trauma and some investigators have attributed this to its long intracranial course. The present study aimed to elucidate an additional mechanism to explain this phenomenon. Twelve fresh adult cadavers underwent dissection of Dorello canal using standard microsurgical techniques. In addition, traction was applied to the nerve at its entrance into this canal before and after transection of Gruber ligament to observe for movement. In all specimens, a secondary tunnel (i.e., tube within a tube) was found within Dorello canal that exclusively contained the abducens nerve. This structure rigidly fixated the abducens nerve as it traversed Dorello canal, thereby not allowing any movement. Transection of Gruber ligament did not detach the nerve, but after release of the inner tube, the nerve was easily mobilized. Rigid tethering of the abducens nerve with a second tube within Dorello canal affords this nerve no ability for movement with motion of the brainstem. We hypothesize that this finding is a main factor in the high incidence of abducens nerve injury after head trauma.