**11. Complications of surgical clipping**

*New Insight into Cerebrovascular Diseases - An Updated Comprehensive Review*

[130, 135, 136]. Despite the differences in regard to mortality being relatively small, they are nonetheless significant and favor endovascular coiling as the safest of the two [136]. Aside from preventing rupture, interventional therapy has demonstrated cognitive improvement without causing further intellectual deficits, in addition to a decrease in anxiety levels [137, 138]. Older patients harboring MIAs without a history of SAH can be managed conservatively, whereas those at risk or with a previous SAH should be treated in a one- or two-staged intervention [119]. Moreover, coiling might prove more appropriate for those with serious comorbidities and in an altered clinical state, while clipping is more suitable in the presence of intracranial vasospasm or hematomas [69]. The same as for younger patients with MIAs, the ruptured lesion should always be managed first and foremost, yet for unruptured MIAs treatment may only be indicated if the risk related to observation outweighs those of therapy.

*Illustrative case 2. (A) CTA 3D reconstruction of a 55-year-old male with multiple cerebral aneurysms two on the right middle cerebral artery and one the left middle cerebral artery bifurcation. He presented to emergency department with right-sided weakness with gradual onset 3 days prior to surgery. Video 2 is available at: https://bit.ly/2Z8W6rm. He underwent microsurgical clipping via a right frontolateral craniotomy. All the clips were placed in the same procedure. (B) Postoperative CTA 3D reconstruction showing* 

There are conflicting reports regarding the postprocedural outcomes for these interventions. Short-term outcomes generally favor endovascular procedures, with a higher incidence of postinterventional adverse events after surgery [74, 139]. According to Kim et al., there is no significant difference regarding all-cause mortality at 7 years after the elective treatment of UIAs via either clipping or coiling [140]. The meta-analysis performed by Ruan et al. showed similar outcomes for the two procedures [141]. On the other hand, in their meta-analysis, Falk Delgado et al. reported a higher independent outcome and lower mortality after coiling of UIAs [108]. The outcomes may be improved with the intraoperative use of electrophysiological monitoring, fluorescence angiography, or Doppler ultrasonography [142]. Surgical clipping of UIAs does not negatively impact quality of life nor does it affect cognitive functions in such a way that patients are unable to work or drive at 6 weeks or 1 year after the intervention [143, 144]. The risk of poor outcome for patients below the age of 65 stands at around 2–4% and rises with aneurysm size, which when compared to the 0.3–0.9% risk of annual rupture might outclass the natural history in a few years after treatment [89, 103, 145]. Nonetheless, mortality is extremely low, if not inexistent in these series. Therefore, a more aggressive treatment may be acceptable for UIAs in younger patients. Although some series

**10. Neurological and clinical outcome after clipping**

*proper clip placement. He was discharged without any additional deficit.*

**162**

**Figure 4.**

Since clipping is a surgical intervention, there are chances of developing complications related to the procedure, medical and infectious complications as well as those attributable to anesthesia. The following paragraphs will focus on the complications of clipping itself. These can be divided according to timing of onset after the intervention into immediate and delayed complications.

IAR is one of the most frequent and most dreaded periprocedural complications [147]. This is especially the case for inexperienced (and oftentimes reckless) surgeons; however, preoperative GCS has also been shown to play a role in predicting this event [148]. It occurs especially around the time of neck dissection and clip placement or adjustment and is capable of hampering the microsurgical procedure, sometimes being life-threatening [149]. Nevertheless, it is significantly less frequent for UIAs than for the ruptured lesions [147]. A steady technique, proper discovery of the parent artery, temporary clipping proximal to the aneurysm, and aspiration can regain control of the situation and ensure proper clip placement.

Ischemic complications may also arise from improper clip placement or due to thromboembolism from the aneurysm. The type and severity of neurological consequences depend mostly on the location of the aneurysm [150–153]. The most frequent type of postoperative events and possibly even underestimated, ischemia leads to poorer outcomes at discharge and often entails a reintervention [153, 154]. After clipping of UIAs, transcranial Doppler studies show a decrease in transient reduction in cerebrovascular reactivity on the side of the aneurysm, leading to a proneness toward cerebral ischemia [155]. Endovascular procedures apparently bear a higher risk for thromboembolic events and ischemia [156], yet a recent meta-analysis showed that there was no statistical difference between coiling and clipping in respect to this event [141]. Incidence of perforator territory ischemia is higher for aneurysms of the A1 segment, whereas olfactory disturbances are more common for lesions of the ACoA [157]. Silent ischemic lesions are fairly frequent (up to 10% of procedures) and mostly irreversible, though rarely disabling [153, 157]. It has been argued that induced hypertension may reduce the effects of delayed cerebral ischemia [158]. Regardless, there is still no conclusive data to sustain the benefits of induced hypertension, whereas serious adverse events are sometimes unavoidable.

Another undesirable complication is the occlusion of the surrounding arteries, especially deep and subtle perforators. Again, dissection, proper magnification and illumination of the surgical field, and adequate brain relaxation can improve the visibility of the aneurysmal neck and surrounding structures. It is also important to utilize clips adjusted to aneurysm size and morphology. Electrophysiological monitoring, micro-Doppler ultrasonography, or intraoperative angiography can rapidly detect an arterial occlusion and facilitate repositioning of the clip [152, 159].

Clip slippage can happen when advanced atherosclerosis thickens the aneurysmal wall, making it impossible for the clip to close properly [151, 160]. Clip rotation and kinking of the parent vessel can also be the result of uneven arterial walls due to atheromatous degeneration [94]. Using a double-clip technique can often prevent this from occurring, yet certain aneurysms may require more complex techniques [151, 125, 160].

Aneurysmal residue or incomplete occlusion signifies an aneurysm sac or neck that is still permeable and has a significant chance of rupture [37, 80, 86, 161, 162]. Aneurysmal rest (or dog ear) occurs when a small triangular portion of the neck is not occluded by the aneurysmal blades. In time, and under certain hemodynamic conditions, this residual neck can lead to aneurysm regrowth, and eventual rupture, requiring further imaging studies and possibly another intervention [104]. In the microsurgical series described by Nanda, the majority of recurrences were found at the ACoA, followed by ICA, VA, and PICA [163]. Adequate neck dissection and using suitable clips may avoid this complication [164]. Also using intraoperative angiographic procedures can confirm proper clip placement.

Clipping UIAs of the ophthalmic artery can lead to visual disturbances [162]. Apparently, if visual deficit was present before treatment, clipping may offer a higher degree of improvement than coiling [162, 165]. From our own experience, we can add that the clipping of aneurysms of the paraclinoid segment of the ICA or the superior hypophyseal artery may in some cases result in acute pituitary deficiency. Some of these patients will require lifelong hormone substitution therapy.

Cerebral vasospasm is predominantly a complication of ruptured aneurysms, but it has rarely been described as occurring after clipping of UIA [166]. The exact etiological mechanism is unknown, although it might be multifactorial, especially after aggressive manipulation of the vessels.

Cognitive dysfunction after UIA therapy may occur, regardless of treatment method [137]. Nevertheless, the exact effect clipping has on cognitive functions remains uncertain.

Some patients with surgically treated UIAs may develop a chronic subdural hematoma in time, being at a higher risk for this than patients with ruptured lesions [167]. Risk factors include brain atrophy, male sex, chronic antiplatelet use, and advanced age.

As long as the risk of complications remains, the incentive of perfecting microsurgical techniques will persist. The purpose of gaining surgical experience is to ensure a long-term survival of the patient with the best possible neurological outcome, while also striving to lower or eliminate the chance of adverse events.
