Mobilization of the transcavernous oculomotor nerve during basilar aneurysm surgery: biomechanical bases for better outcome.
BACKGROUND
The transcavernous approach adds a significant exposure advantage in basilar aneurysm surgery. However, one of its frequently reported side effects is postoperative oculomotor nerve palsy.


OBJECTIVE
To present the technique of mobilizing the oculomotor nerve throughout its intracranial course and to analyze its consequences on the nerve tension and clinical outcome.


METHODS
The oculomotor nerve is mobilized from its mesencephalic origin to the superior orbital fissure. Its degree of mobility, related to the imposed pulling force, was measured in 11 cadaveric nerves. Tension was mathematically deduced and compared before and after mobilizing of the cavernous segment. One hundred four patients treated for basilar aneurysms with the orbitozygomatic pretemporal transcavernous approach were followed up for a 1-year period and evaluated for postoperative oculomotor nerve palsy.


RESULTS
Releasing the transcavernous segment compared to cisternal mobilization alone resulted in a significant increase in freedom of mobility from 4 to 7.9 mm (P < .001) and in a significant decrease in tension from 0.8 to 0.5 N (P = .006). Ninety-nine percent of aneurysms treated with this technique were amenable to neck clipping, and a total of 84% of patients had a good postoperative outcome (modified Rankin Scale score, 0-2). All patients showed direct postoperative palsy; however, 97% had a complete recovery by 9 months. Only 3 patients had a persistent diplopia on medial gaze, which was corrected with prism glasses.


CONCLUSIONS
Mobilization of the transcavernous oculomotor nerve results in better maneuverability and less tension on the nerve, which lead to successful surgical treatment and favorable oculomotor outcome.
*Arkansas Neuroscience Institute, St. Vincent's Infirmary, Little Rock, Arkansas; ‡Department of Neurosurgery, Uppsala University Hospital, Uppsala, Sweden; §Division of Neurosurgery, Department of Neuroscience and Rehabilitation, Santa Anna University Hospital, Ferrara, Italy.
Jaafar
J
Basma
Mats
M
Ryttlefors
Francesco
F
Latini
Svetlana
S
Pravdenkova
Ali
A
Krisht
D001488:Basilar Artery; D001696:Biomechanical Phenomena; D004172:Diplopia / Q000209:etiology / Q000628:therapy; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D002532:Intracranial Aneurysm / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D008959:Models, Neurological; D009038:Motion; D019635:Neurosurgical Procedures / Q000009:adverse effects; D009802:Oculomotor Nerve / Q000033:anatomy & histology / Q000502:physiology; D015840:Oculomotor Nerve Diseases / Q000209:etiology; D020127:Recovery of Function; D013997:Time Factors; D016896:Treatment Outcome