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|Year : 2019 | Volume
| Issue : 5 | Page : 1254-1256
Anterior Circulation Aneurysm Clipping – Pterional Craniotomy or Modified Pterional Craniotomy?
Bhawani Shanker Sharma1, Kanwaljeet Garg2
1 Department of Neurosurgery, Mahatma Gandhi University of Medical Sciences and Technology, Sitapura, Jaipur, Rajasthan, India
2 Department of Neurosurgery, All India Institute of Medical Sciences, New Delhi, India
|Date of Web Publication||19-Nov-2019|
Dr. Kanwaljeet Garg
Department of Neurosurgery, Mahatma Gandhi University of Medical Sciences and Technology, Sitapura, Jaipur, Rajasthan
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Sharma BS, Garg K. Anterior Circulation Aneurysm Clipping – Pterional Craniotomy or Modified Pterional Craniotomy?. Neurol India 2019;67:1254-6
The authors compared the efficacy and safety of modified mini-pterional craniotomy (mMPC) and standard pterional craniotomy (PC) for clipping of ruptured anterior circulation aneurysms. They included 45 patients with 21 in the PC group and 24 in the mMPC group and used systemic inflammatory response syndrome (SIRS) score as a marker of the invasiveness of the surgical approach. They found that the total operative time was significantly shorter in the mMPC compared with the PC, while the rate of permanent operative morbidity was similar in both groups. The mean SIRS score at 24 h after the completion of the operation was significantly lower in patients in the mMPC group when compared with patients in the PC group. The rate of postoperative symptomatic vasospasm was significantly lower in patients operated through the mMPC than the PC. Good outcome at discharge was more frequently seen in the mMPC than in the PC, but this difference was not statistically significant. They concluded that mMPC is a safe and less invasive approach for ruptured anterior circulation aneurysms, leading to a significant lower rate of postoperative symptomatic vasospasm and a marginally significant improvement in clinical outcomes.
Surgical clipping is commonly used to treat anterior circulation aneurysms, although endovascular coiling is becoming more popular these days. PC is the most commonly used surgical approach. Krause was among the first to describe a PC, while it was Heuer and Dandy who performed the first PC or frontolateral approach to the optic chiasm and hypophysis. However, it was Prof. Yasargil who refined and popularized the PC. Safety and efficacy of pterional approach is well-established and many large studies have proven it as well., PC requires complete reflection of the temporal muscle and exposes large areas of the cortex, which is not required most of the time. The limitations of PC are cosmetic, like temporalis muscle atrophy and damage to the frontal branch of the facial nerve.
Two factors which have been shown to be associated with trauma to the normal brain and permanent neurological deficits during aneurysm surgery include the brain retraction and exposure of normal brain during surgery.,,, Various strategies adopted to tackle both these factors include the use of anesthetic techniques to lessen cerebral edema, patient-positioning techniques to encourage brain relaxation, and specially designed brain retractor systems. Another strategy is to use less invasive approaches or keyhole techniques. Various described techniques include the lateral supraorbital approach, mini-supraorbital approach, the supraorbital keyhole approach, sphenoid ridge keyhole approach, MPC, modified pterional with temporalis muscle splitting, and eyebrow approaches.,,,,,, The basic idea of these less invasive approaches is to decrease brain retraction and the extent and duration of brain tissue exposure. These approaches offer alternative incisions and craniotomies that aim to provide similar surgical access that the PC would provide for select intracranial pathology, but with smaller size and improved cosmetic results. The advantages of less invasive or limited approaches are well-described in literature.
The two most common less invasive surgical approaches include supraorbital keyhole craniotomy and MPC.
Figueiredo et al. first described MPC. Using computerized tracking, they showed that dissection of the sylvian fissure distal to the anterior ascendant ramus does not provide additional exposure of the basal cisterns or circle of Willis using computerized tracking. The anterior ascendant ramus corresponds closely to the pterion at the lateral aspect of the cranium. Thus, instead of centring the craniotomy on the pterion, they used pterion as a landmark for determining the posterior and distal limits of the craniotomy., The MPC allows extensive drilling of the lateral aspect of the sphenoid wing and the wide opening of the sylvian fissure, the two main features of the standard PT technique. As subfrontal–transsylvian route is used for anterior circulation aneurysms, lower temporal exposure is avoided along with the adverse cosmetic effects associated with dissection of the temporalis muscle.
MPC is a smaller version of PC and is centred over the lesser wing of the sphenoid. It provides similar operative corridor as the PC, but the incision is smaller, and there is less muscle dissection and a smaller craniotomy. One gets better wound healing and cosmesis, and less postoperative pain. Figueiredo et al. demonstrated that this technique represents an optimal balance among size of craniotomy, extent of dissection of the temporalis muscle, splitting of the sylvian fissure, and microsurgical exposure. In their analysis of PC and MPC, they found no difference in the area of surgical exposure, angular exposure, and the boundaries of the anatomic exposure provided by these two craniotomies. There were also no substantial differences in trajectories, even for contralateral limits. However, the lateral limit of exposure is more distal with the PC, thereby enabling more distal dissection of the sylvian fissure than with the MPC.
Caplan et al. described their experience of 74 MPCs performed on 72 patients to treat a total of 82 aneurysms. They did not include patients presenting with aneurysmal subarachnoid haemorrhage (SAH), aneurysms with partial thrombosis due to anticipated complexity such as possible need for thrombectomy in which a large craniotomy might be needed. They reported that the operative corridors were adequate in all cases and clip applications were not compromised. There were 10 significant complications in their cohort which included visual diminution in six patients with paraophthalmic region aneurysm, large middle cerebral artery (MCA) infarct, contralateral stroke, operative site epidural hematoma requiring evacuation, seizure, and third nerve palsy in one patient each. Temporalis muscle wasting was rated as none to minimal in 71 (96%) of the cases. They concluded that MPC is an alternative over the standard PC for unruptured MCA, posterior communicating artery (Pcomm), and paraophthalmic aneurysms. They further recommended that MPC is not suitable for internal carotid artery (ICA) terminus or anterior communicating artery aneurysms as more brain retraction is required for these aneurysms.
The other commonly used less invasive approach for the anterior circulation aneurysms is the supraorbital keyhole approach through a small incision in the eyebrow.,, This approach is not very widely used, and the safety and efficacy of this approach is a subject of debate. This approach was first described by Jane et al., in 1982, but was refined and popularized by Axel Perneczky, who was a pioneer in the development of keyhole approaches in neurosurgery.,, This approach potentially minimizes the brain exposure, retraction, and traumatization. The small incision also avoids the supraorbital nerve/artery, the frontal branches of the facial nerve, the superficial temporal artery, and the temporalis muscle.
Chalouhi et al. published their results of a study involving a total of 87 patients who underwent surgical clipping of aneurysms, 40 through the pterional and 47 through the supraorbital keyhole approach. The total operative time was significantly shorter in the supraorbital group. The rate of procedural complications was lower in patients treated through the pterional versus the supraorbital approach. Intraoperative aneurysm ruptures occurred more frequently in the supraorbital group. One year after treatment, 75% of patients achieved a favorable outcome (Glasgow Outcome Scale IV or V) in the pterional group versus 76.6% in the supraorbital group. They concluded that the rate of procedural complications may be higher with the supraorbital keyhole approach, but the overall patient outcomes appear to be comparable.
The use of supraorbital keyhole approach through an eyebrow incision for anterior circulation aneurysms has been shown to be associated with a favorable rate of approach-associated surgical complications and high patient satisfaction with cosmetic outcome in other studies as well.
However, there are disadvantages of the supraorbital keyhole approach as well. The working space is limited significantly in a keyhole approach and it becomes difficult in cases of tense brain and when there is intraoperative aneurysm rupture. Hence, it takes a surgeon some time to gain confidence with this procedure. Given the advantages of keyhole craniotomy and the steep learning curve, one should select cases very carefully and detailed preoperative planning should be done.
To conclude, these less invasive approaches can be used in selected patients with anterior circulation aneurysms. However, one has to choose the case very carefully after studying the preoperative imaging. Moreover, the surgeon must have adequate training and experience before shifting from a standard approach like PC to less invasive approaches, as the invasiveness of the surgical approach on the brain matters more than on the skin and subcutaneous tissues in neurosurgery.
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