This document discusses microsurgery techniques for treating aneurysms of the vertebral artery, posterior inferior cerebellar artery, and vertebrobasilar junction. It describes the clinical significance, indications for treatment, preoperative evaluation, surgical approaches including far-lateral suboccipital, transfacial transclival, and combined subtemporal-presigmoid transtentorial. Treatment of vertebral dissecting and fusiform aneurysms as well as potential complications are also summarized.

1. Microsurgery of Vertebral Artery,
Posterior Inferior Cerebellar Artery,
and Vertebrobasilar Junction Aneurysms
Eric C. Chang n Brian L. Hoh n Christopher S. Ogilvy
9/02/16

2. Clinical significance
• Uncommon
• High risk for rebleeding
• High morbidity and mortality rates
• Region of the skull base that can be difficult to
access surgically
• Close proximity to the brainstem and lower
cranial nerves
• High incidence of fusiform nonsaccular aneurysms
• Dissecting aneurysm

3. Indications
• Ruptured vertebral artery and vertebrobasilar
junction aneurysms cannot be left untreated
• Timing
– The International Cooperative Study on the Timing of
Aneurysm Surgery did not include enough
vertebrobasilar aneurysm to make any significant
conclusions about the timing of surgery for aneurysm
at this location

4. Presentation
• SAH
• Ischemic symptom
• Unruptured
– signs and symptoms of ischemia or mass effect
– cranial nerve deficits(V to XII) : dysarthria,dysphagia
– brainstem compression
– cerebellar symptom : ataxia
– hemiparesis
– posterior fossa symptoms

5. Diagnostic evaluation
• first clinically, by history and examination
• computed tomography (CT)
– Hydrocephalus 95%
– IVH 95%
– Supratentorial SAH 70%
– Isolated posterior fossa SAH 30%
• lumbar puncture

6. Diagnostic evaluation
• Vertebral dissection
– string sign
– pearl and string sign
– tapered narrowing
– occlusion
– double lumen
– pseudoaneurysm
• 4-vessel angiogram : gold standard

7. Preoperative evaluation
• Orientation and projection of the neck and dome
– The neck is encountered before the dome
• Size
– Giant : not amenable to standard surgical clipping
– CTA or magnetic resonance angiography
– Varying
– Degrees of intraluminal thrombosis
– The angiographic opacity may not show the full size of the
aneurysm appreciated on CT scan

8. Preoperative evaluation
• Angiographic detail
– PICA reduplicate
– PICA contralateral artery is present
– PICA territory is supplied by an alternative vessel : AICA
– PICA are being supplied through the posterior circulation
• Fetal type PCoA
• Size of PCoA : small  worse outcome
– Bony structure
• bony anatomy of the posterior fossa

9. Technique
tonsillomedullary segment
distal to the cerebellotonsillar
and cortical segments
vertebral artery
proximal segment PICA,
vertebrobasilar junction aneurysms
midline vertebrobasilar junction
aneurysms
unusually high
vertebrobasilar junction
aneurysms

10. Far-Lateral Suboccipital Approach(Heroes)
vertebral artery
proximal segment PICA
vertebrobasilar junction aneurysms

11. Transfacial Transclival Approach(deFries and colleagues)
midline vertebrobasilar junction aneurysms

12. Transfacial Transclival Approach(deFries and colleagues)
• Supine position
• Lumbar drain or ventriculostomy
• Doppler probe : preserve the facial artery
• Incision : the glabella around the right lateral alar
margin to the piriform aperture
• Osteotomy of the nasal bones and disarticulation of
the septal cartilage from the ethmoid allow for
reflection of the nose laterally

13. Transfacial Transclival Approach(deFries and colleagues)
• The medial wall of one or both maxillary sinuses,
the bony septum, the turbinates, the ethmoid air
cells, and the floor of the sphenoid sinuses should be
removed
• A large triangular exposure of the clivus is revealed
by a midline incision into the retropharyngeal
mucosa
• A rectangular window of about 2 cm superior-
inferior by 1.2 to 2.5 cm left-right is draggled into the
anterior clivus

14. Combined Subtemporal-Presigmoid Transtentorial Approach

15. Combined Subtemporal-Presigmoid Transtentorial Approach
• unusually high vertebrobasilar junction aneurysms
• lateral position with the ipsilateral shoulder retracted
• U shape incision :
– anterior to the tragus at the level of the zygoma, circling
above the pinna and descending behind the pinna to a
point about 1.5 to 2 cm behind (medial to) the mastoid
• temporal-suboccipital (retrosigmoid) craniectomy

16. Combined Subtemporal-Presigmoid Transtentorial Approach
• complete mastoidectomy
– extensive removal of the posterior-superior petrous
pyramid anteriorly to
– but not exposing, the facial canal and the lateral and
posterior semicircular canals
• Linear dura incision
– parallel to the floor of the middle fossa anteriorly and
to the transverse sinus posteriorly
• Vertical dural incision
– is made to the presigmoid region continuing up toward the
tentorium

17. Combined Lateral and Medial Suboccipital Approach
• tonsillomedullary segment
• The patient position, skin incision, and craniectomy
are as described for the far-lateral suboccipital
approach
• bone removal extending well past midline in the
inferior aspect of the occipital bone and the foramen
magnum as well as the arch of C1
• retract the tonsils upward, medially, or laterally

18. Midline Suboccipital Approach
• the segments distal to the tonsillomedullary segment
• standard midline suboccipital craniectomy extending
through the foramen magnum

19. Treatment of Vertebral Dissecting and Fusiform Aneurysms
• Particularly ruptured ones, carry a high risk for
rebleeding in the acute period after the initial bleed
and require early management
• If their shape and morphology are such that direct
surgical clipping is possible
– far-lateral suboccipital approach
• Fusiform morphology
– proximal parent artery occlusion (hunterian ligation)
– trapping procedures
– clip reconstructions

20. Treatment of Vertebral Dissecting and Fusiform Aneurysms
• Endovascular options
– parent vessel occlusion or stent placement
– combinations of coil and stent therapies
• In which the ipsilateral vertebral artery proximal to
the aneurysm is occluded
– adequate retrograde or collateral flow would supply the
cerebellar territories if flow to the ipsilateral PICA is
compromised
– If needed, a bypass procedure can be done : occipital-PICA,
PICA-PICA bypass

21. Treatment of Vertebral Dissecting and Fusiform Aneurysms

22. Complications
• injury to the lower cranial nerves (9th through 12th)
– standard approaches use a surgical corridor through the
lower cranial nerve rootlets
– variable and often tortuous course of PICA and vertebral
vessels occasionally requires retraction of nerve rootlets.
– dysphagia, dysarthria, dysphonia, and inadequate
airway protection
• the 6th cranial nerve is located close to a high
vertebrobasilar junction and can be subject to
injury

23. Complications
• Postoperative lateral medullary (Wallenberg’s)
syndrome if the PICA is occluded

24. Complications
• Transclival approach
– Cerebrospinal fluid leak
– Meningiits