Isolated abducens nerve palsy following lumbar puncture: case report and review of the mechanism of action.

Isolated abducens nerve palsy following lumbar puncture is a very rare condition. In this case we discussed the probable causes of abducens nerve palsy and review the mechanism of action in anatomical relevant literature. A 53-year old hypertensive female patient with a saccular aneursym on the left middle cerebral artery (MCA) bifurcation underwent emergency operation. Before the operation lumbar puncture (LP) was performed to the patient lying on the right lateral position to facilitate cerebral relaxation intraoperatively. The left MCA bifurcation aneurysm was clipped successfully with a left pterional-transsylvian approach. Postoperatively, she complained of visual diplopia and postural headache. In her neurological examination, isolated abducens nerve palsy was found on the left eye. The patient was treated with intravenous hydration, bed rest and non - steroid anti-inflamatuary drugs (NSAID) for postural headache. Her postural headache was resolved in the postoperative fifth day, but her abducens nerve palsy was present in the postoperative sixth month follow-up. Many classic textbooks have attributed the vulnerability of the abducens nerve to its long intracranial course, but it is now known that abducens nerves angulation points are the vulnerable parts of the nerve. We hypothesize that the petroclival dural entrance point is the entrapment point and lateral type abducens nerve, if present may be a factor that facilitates the injury of the nerve by lumbar puncture (LP).