Paramedian vertebral aneurysms in the lower third clival region are one of the most difficult lesions to access surgically. Although several approaches with drilling of the skull base have been considered for aneurysms in this region, successful clipping in the acute stage without permanent neurological deficits is thought to be extremely rare. We experienced a case of VA-PICA aneurysm located 6 mm across the midline that was successfully clipped in the acute stage via the far-lateral suboccipital approach. The usefulness of this approach is reported in this paper.
A 52-year old female was admitted to our hospital suffering from severe headache. Right vertebral angiography revealed a right VA-PICA aneurysm located 6 mm across the midline towards the left. The pre-operative condition of this patient was classified as Hunt and Kosnik's grade 1. Direct clipping was completed on day 0 via the far-lateral suboccipital approach. The long straight clip (Sugita No. 18) was applied above the hypoglossal nerve by left hand, permiting microscopic visualization of the aneurysm below the hypoglossal nerve. Transient vagal and hypoglossal nerve palsy noted post-operatively were restored within a week. The post-operative vertebral angiography revealed complete clipping of this aneurysm.
The far-lateral suboccipital approach, in which the postero-medial third of the occipital condyle is drilled out, permits access to the midline, lower third clival region from the extreme infero-lateral direction. Excessive retraction against the brainstem and obstruction of the operative view by the lower cranial nerves are therefore minimal with this approach. The wide longitudinal operative field afforeded by this approach allows insertion of the clip from various directions and acute stage operation. An additional drilling of the jugular tubercle should also be considered depending on the height of the aneurysm.
