Anterior Communicating Artery Aneurysm: Subarachnoid and Intracerebral Hemorrhage from an Aneurysm on the Posterior Aspect of the Anterior Communicating Artery – Microsurgical Clipping with a Fenestrated and Angulated Clip Without Direct Visual Control During Clip Application
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A 72-year-old female patient suddenly lost consciousness due to a subarachnoid hemorrhage (SAH) and a large intracerebral hematoma (ICH) stemming from the rupture of an aneurysm on the small anterior communicating artery (AcomA). The poor clinical condition of the patient meant that the ICH needed to be surgically removed. The small wide-necked aneurysm was not suitable for coil occlusion. Since there was no escaping surgery, the decision was made to also clip the aneurysm. As the aneurysm was hidden on the posterior wall of the AcomA and therefore not actually visible during the operation, a fenestrated clip was used. CTA following the operation confirmed that this had completely obliterated the aneurysm while leaving the afferent and efferent vessels patent. When the patient was referred on to a rehabilitation facility, she was awake, aphasic, and with no motor deficit. Most ruptured anterior communicating artery (AcomA) aneurysms are nowadays eliminated by endovascular therapy. However, in selected cases in which the aneurysm is not suitable for endovascular therapy, surgical clipping is the suggested route. In this chapter, we address the surgical approach, the as yet unsolved issue of which side to approach from, and radiological follow-up for ruptured AcomA aneurysms which have been microsurgically clipped. Microsurgical clipping of ruptured AcomA aneurysms is the main topic of this chapter.
KeywordsAnterior communicating artery Intracranial aneurysm Microsurgical clipping Fenestrated clip
A 72-year-old female patient with an otherwise unremarkable medical history was found unconscious at home. She was transported to the emergency room for further diagnostics and treatment. Prior to intubation, her level of consciousness was graded as 6 on to the Glasgow Coma Scale (GCS).
After consultation with the neuroradiologist, the decision was made to perform surgical clipping, based on the anatomy of the aneurysm. The small size of the aneurysm coupled with its wide neck made it unsuitable for endovascular treatment. The large intraparenchymal hematoma had to be removed surgically, which was an additional argument to clip the ruptured aneurysm.
Procedure, 20.12.2017: microsurgical clipping of a small ruptured AcomA aneurysm and removal of an intracerebral hematoma in the right frontal lobe
Anesthesia: general anesthesia, mannitol, and dexamethasone were given, and systolic blood pressure was maintained below 110 mm Hg in order to relax the brain.
Technical equipment: Pentero 800
Carl Zeiss: indocyanine green (ICG) angiography
Course of treatment: with the patient already in endotracheal anesthesia upon admission, a ventriculostomy was inserted. Mannitol and dexamethasone were administrated, and systolic blood pressure was maintained below 110 mmHg in order to achieve maximum brain relaxation. The patient was placed in a supine position with the head rotated 20° to the right. The aneurysm was approached from the side of the dominant A1 segment, in this case, the left. Fine adjustment of the head position was accomplished by tilting the operating table. The patients’ neck was hyperextended, resulting in a 20° angle between the plane of the anterior cranial fossa and the vertical plane of the axis. The head was then secured in a Mayfield clamp, with the clamp positioned as horizontally as possible. Care was taken in the adjustment and balancing of the surgical microscope that the neural baseline position of the objective tube was set at an angle of 20° from vertical. This position allowed easy manipulation of the microscope. A temporo-frontal hairline skin incision was performed. The incision was started 1 cm in front of the tragus and slightly above the zygomatic arch and extended to the frontal midline. The superficial temporal artery within the temporal fascia was identified. Dissection was performed in the interfascial plane, and the supraorbital fat pad was mobilized alongside the scalp flap to prevent injury to the frontal branch of the facial nerve. The temporal muscle at the attachment of the orbital pillar was dissected and pulled back.
Two burr holes were made, the first on the frontozygomatic suture and the second above the orbital rim at the medial aspect of the planned craniotomy. The craniotomy was performed, and the superior and lateral orbital rims were cut. The bone flap was elevated and fractured between the end of the medial and lateral orbital roof incision.
Duration: 150 min
The patient recovered consciousness after the operation; however, she remained severely impaired with neurocognitive deficits (disorientation) and aphasia. She was able to walk with assistance. Due to a lack of social security and medical insurance, rehabilitation was significantly delayed. The patient stayed in our department for 6 months before she was transferred to a rehabilitation facility.
Over the past three decades, the attitude regarding surgical treatment for intracranial aneurysms has changed. The introduction of endovascular techniques has resulted in the development of less traumatic alternatives for traditional craniotomies. Reduction of the craniotomy size is only possible if the concept of a standard craniotomy for anterior circulation aneurysms is abandoned. Smaller craniotomies must be optimally placed and centered on the most direct path to the neck of the aneurysm. To this end, we use four differently tailored craniotomies for anterior circulation aneurysms.
Traditionally, there are multiple approaches for the clipping of AcomA aneurysms. The frontal interhemispheric approach has failed to gain wide acceptance due to limited proximal control and the risk of venous infarction following an injury of frontal bridging veins (Tsutsumi et al. 1991). Instead, the pterional approach has replaced the bifrontal and frontolateral craniotomy as a standard approach for access to aneurysms of the anterior circulation (Yasargil and Fox 1975). However, the problem with the pterional approach for AcomA aneurysms is that the axis of access to the AcomA usually lies 5–10 mm above the cranial base in the interhemispheric fissure. As a result, the pterional approach often requires the medial aspect of the gyrus rectus to be resected in order to enable adequate control of the AcomA complex (Chehrazi 1993; Horikoshi et al. 1992; Kempe and VanderArk 1971). Although there is no definitive indication that gyrus rectus resection has a negative impact on the functional outcome following AcomA aneurysm repair, we are reluctant to accept this as a standard treatment for ordinary aneurysms (Brock and Dietz 1978). Several orbitocranial and orbitozygomatic approaches exist; however, they seem overly complex for standard treatment in which minimal invasiveness has become an increasingly important criterion (de Souza et al. 1995; Fujitsu and Kuwabara 1986; Harland et al. 1996; Horikoshi et al. 1992; Poletti 1989; Smith et al. 1989; Steiger et al. 2001; Zabramski et al. 1998). As a result, we tend to favor a small orbito-cranial approach for purely extra-axial control of AcomA aneurysms as this allows for a more ventral line of access of the interhemispheric fissure and minimizes both brain retraction and the need for gyrus rectus resection (Steiger et al. 2001). Usually, we prefer an exposure through the side of the dominant A1 segment because of the specific pathoanatomy of the A2 segments. Due to normal physiological elongation of the A1-segment during aging, the anterior communicating artery usually rotates so that the origin of the ipsilateral A2 to the larger A1 is displaced posteriorly, allowing insertion of the clip blades between the two A2 segments. This so-called open A2 plane has been reported in approximately 80% of patients with superior-type aneurysms (Suzuki et al. 2008). In the patient described above, a closed plane and the thus anteriorly displaced A2 segment actually obstructed our view of the aneurysm. A closed A2 plane is associated with additional surgical requirements such as A2 displacement and gyrus rectus resection and may result in a residual aneurysm neck. It also increases the risk of injury to Heubner’s artery, diencephalic perforators, and contusions (Suzuki et al. 2008). The obvious consequence from the association between the closed A2 constellation and surgical complications would be that all superior projecting aneurysms should be approached from the side that provides an open plane. In the case presented above, a contralateral transorbital exposure to the dominant A1 would have probably provided a better view of the aneurysm and reduced the risk of perforating arteries occluding; especially as in this specific case, the aneurysm was located above the plane of the A1 segment and behind the plane of the A2s. These so-called “type 4” aneurysms require access to the neck above the A1s, which is between the perforators. The aneurysms are also in close approximation to the hypothalamus and could be more easily damaged by aneurysmal hemorrhage and surgical manipulation. As a result, these type 4 projections are associated with a less favorable outcome compared to other projections.
Injury of perforating branches from the AcomA complex generally results in memory disturbance, personality changes, and decreased spontaneous activity (Crowell and Morawetz 1977; Suzuki et al. 2008; Vincentelli et al. 1991). However, this kind of deficit remains undetected as neuropsychological evaluation is not done in most studies. As a result, little is known about the postoperative results with respect to the intraoperative difficulty of the approach.
In this instance, the choice was made to place a fenestrated clip accommodating the ipsilateral A1. It should be noted that the use of fenestrated clips in the treatment of AcomA aneurysms is – in our experience – extremely rare. Drake initially developed the fenestrated clip in 1969 due to his experience with large basilar bifurcation aneurysms in which the adherent P1 segment could not be safely separated from the neck of the aneurysm. With his preferred subtemporal approach, it was very difficult to work around the ipsilateral proximal P1, and as a result, the fenestrated “Drake-Kees clip” was developed with an aperture to accommodate the P1 (Del Maestro 2000).
In our experience, the use of fenestrated clips as well as the superior-type aneurysms is associated with larger neck remnants. Since the size of the neck remnant is associated with the risk of aneurysm re-rupture, there is a distinct need for radiological follow-up to monitor aneurysm remnants or de novo formation. However, since catheter angiography carries a theoretical risk of thromboembolic complications with resulting neurological impairment, CTA is increasingly preferred to follow-up on patients who have undergone aneurysm repair (David et al. 1999; Dehdashti et al. 2006; Jabbarli et al. 2016). However, the accurate visualization of the aneurysm neck or parent and branching arteries after aneurysm treatment can be limited due to a superimposed clip or coil artifacts in conventional (single-energy) CTA imaging.
In our practice, we use dual-energy CTA as an alternative imaging modality for catheter angiography. Dual-energy CTA was initially developed for high-temporal resolution imaging of cardiovascular pathologies but has also shown to have a high sensitivity and specificity for detection of small (i.e., 5 mm or less) intracranial aneurysms and neck remnants (<2 mm) (Abdulazim et al. 2017; Dolati et al. 2015). As such, it is our primary modality for the follow-up of surgically treated IA patients. In cases where there is considered to be insufficient (e.g., in complex cases with multiple clips) or a significant remnant or de novo aneurysm is suspected by CTA, DSA is carried out for further evaluation (Abdulazim et al. 2017).
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