Surgical Treatment of Ruptured Anterior Circulation Aneurysms: Comparative Analysis of Modified Mini-Pterional and Standard Pterional Craniotomies
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.271261
Source of Support: None, Conflict of Interest: None
Keywords: Aneurysm, cerebral, minimally invasive, neurosurgery, systemic inflammatory reaction syndromeKey Message: This is the first evidence showing less invasiveness of modified minipterional craniotomy for ruptured anterior circulation aneurysm surgery compared with standard pterional craniotomy.
After the publication of the International Subarachnoid Aneurysm Trial (ISAT) data, endovascular treatment of intracranial aneurysms has been widely accepted as an established standard for aneurysmal subarachnoid hemorrhage (SAH), mainly because of its minimal invasiveness.,, Meanwhile, coil instability necessitating aneurysm re-treatment remains a major shortcoming of this treatment.,,, Microsurgical clipping has durable modality for ruptured cerebral aneurysms, and has become less invasive through minimal craniotomy.[8–10] However, there is no surgical data demonstrating improved outcome with smaller craniotomies, in terms of patient satisfaction, cosmesis and peripheral facial nerve branch preservation.[10–12]
In this study, we compare the use of modified mini-pterional and the standard pterional craniotomies (mMPT and PT, respectively) in the surgery of ruptured anterior circulation aneurysms. The two groups were compared with respect to various clinical indicators, including systemic inflammatory reaction syndrome (SIRS) score as an indicator of invasiveness of the surgeries.
Study design, setting, and participants
The protocol of this retrospective study was approved by the Ethics Committee of our Institute. A written informed consent was obtained from all participants (or their relatives or legal representatives of unconscious patients). Between February 2004 and March 2006, 93 SAH patients presented to our institute. Over the two-year study period, a total of 45 patients who were admitted to our hospital within 24 hours after ictus and underwent microsurgical clipping for ruptured anterior circulation aneurysms were included in this study. 24 patients were treated through the mMPT craniotomy and 21 patients were treated through the PT craniotomy. SAH patients with associated massive intracerebral or intraventricular hematoma who were suitable for decompressive craniectomy or ventricular drainage, patients with high-positioned and/or superior projection ruptured anterior communicating artery (Acom) aneurysm who were suitable for anterior interhemispheric approach, and comatose patients were excluded from this study.
During this study period, all eligible aneurysmal SAH patients were not treated by endovascular coiling at our institute because of non-availability of the endovascular surgeons. To avoid an interoperator variability, all surgeries included in this study were performed by the first author (T.I.), a board-certified neurosurgeon of the Japan Neurosurgical Society, with more than 9 years of experience and stable performances in microsurgical clipping. All consecutive patients were treated through the PT and the mMPT craniotomies during the first half and second half of the study period, respectively.
Following the diagnosis of SAH and ruptured aneurysms, spinal lumber drainage catheters were subsequently inserted at the emergency room under deep sedation with modified neuroleptanalgesia using pentazocine and diazepam. Local anesthesia was completed using xylocaine with the objective to make the blood pressure control easier preoperatively and making a brain slack intraoperatively. Surgery was performed under general anesthesia. The patients were placed in a supine position with the head fixed in a 3-pin Mayfield holder and the head end of the operative table elevated at 15 degrees. The head was rotated about 15 degrees of the opposite to the craniotomy side in a neutral vertex position.
For the PT craniotomy, a skin incision was designed along a line, which was started just in front of the tragus and above the base of the zygomatic arch, gently curving behind the hair line medially and anteriorly to the midline with a hair shave [Figure 1]a. Using a high-speed craniotome, a bone flap was made having a width of approximately 8.0 to 9.0 cm and a height of 5.0 to 6.0 cm [Figure 1]b.
The MPT craniotomy has been described by Figueiredo et al. Our method has some differences from the MPT, thus we named it mMPT. For the mMPT craniotomy, skin was incised along a line, starting 2.5 cm anterior from the tragus and just above the zygomatic arch, gently curving to the forehead, coursing through 3 cm posterior from lateral supraorbital ridge, gradually toward the ipsilateral lateral pupillary line without a hair shave [Figure 1]c. Following skin incision, the temporal muscle was incised along the skin incision and a single myocutaneous flap was reflected anteriorly; this muscular dissection was different from the original MPT. Two burr holes were subsequently drilled, including one just superior to the fronto-zygomatic suture under the linea temporalis and a second at the inferior aspect of the incision. The craniotomy was placed inferior and lateral to the superior temporal line, and the bone flap with a width of 4.0 to 4.5 cm and a height of 2.5 to 3.0 cm was made [Figure 1]d.
For both craniotomies, the sphenoid ridge was rongeoured-off to the level of the superior orbital fissure and until its base was flattened. After drainage of cerebrospinal fluid through the lumbar drainage catheter about 20 to 40 mL (a crucial step to make a brain slack especially for the mMPT), the dura was incised in a semilunar fashion with the base of the flap directed toward the skull base, followed by the opening of the carotid and sylvian cisterns.
Visualization of the anterior ascending ramus of the sylvian fissure, an important landmark for adequate exposure of the anterior circulation, was possible in both the craniotomies. Aneurysmal clipping was performed using standard microsurgical techniques.
All patients were transferred to the intensive care unit following surgery, where they were closely monitored. Fasudil hydrochloride was administered to prevent development of delayed cerebral vasospasm. In case of symptomatic vasospasm, which was defined by neurological deterioration and radiological confirmation of vasospasm with exclusion of other potential contributing factors, induced hypertension with hypervolemia and ozagrel sodium administration, were initiated. A lumbar drainage was continued for patients developing hydrocephalus.
Variables and data collection
The following variables were retrospectively extracted from a prospectively maintained database for this analysis: Demographics including age, gender, past medical history of hypertension, diabetes mellitus, dyslipidemia, and smoking; admission status including Hunt and Hess grade was derived. Aneurysm size, aneurysm locations, operative time, and procedural complications were also collected. Operative time was defined as the time from initiation of skin incision to completion of skin closure. Ischemic or hemorrhagic complications were diagnosed on computed tomography (CT) performed postoperative day 1, 7, and 14. Postoperative three-dimensional computed tomographic angiography (3D-CTA) was performed in all patients for the confirmation of complete aneurysmal clipping. Daily measures of physiological variables including leukocyte count, maximum heart rate, and respiratory rate, and highest or lowest body temperature were collected. Clinical outcomes including symptomatic vasospasm, hydrocephalus requiring shunt implantation, length of hospital stay, and discharge disposition were also collected. The discharge disposition was evaluated using the modified Rankin scale score (mRS) and classified as described.
A “Good outcome” was considered mRS grade 0 to 2, and a “Poor outcome” was considered mRS 3 to 6.
The SIRS score was calculated by summing the number of variables meeting standard criteria for SIRS: (1) Heart rate >90 beats per minute; (2) Respiratory rate >20 breath per minute; (3) Leukocyte count <4000 or >12000; and (4) Body temperature >38°C or 36°C.
A statistical analysis was conducted to compare the two groups of patients. Continuous variables are presented as mean and standard deviation (SD), and categorical variables are presented as frequency. Statistical analysis was conducted by use of the Student's t test for continuous variables, Mann–Whitney test for semi-quantitative variables, or χ2 or Fisher exact test for categorical variables as appropriate. All statistical analyses were performed using SPSS for Windows (version 11.5; SPSS, Chicago, IL). Differences were considered statistically significant for values of P < 0.05.
Participants and descriptive data
There were 21 patients in the PT group and 24 in the mMPT group. Patient characteristics at baseline were similar in the two groups [Table 1]. The age was 65.2 years in the PT group and 59.9 years in the mMPT group (P = 0.20). The proportion of female patients was 76.2% (16/21) in the PT group and 79.2% (19/24) in the mMPT group (P = 0.81). The rate of comorbidities, including hypertension (P = 0.63), diabetes mellitus (P = 0.83), dyslipidemia (P = 0.53), and smoking (P = 0.48), were comparable in both groups. All participants in both groups presented with Fisher group 3 SAH. The preoperative Hunt and Hess grade was similar in both groups (P = 0.77). Although no significant difference was seen between two groups in the site of ruptured aneurysms (P = 0.75), the mMPT group included more ruptured MCA aneurysms than the PT group. Aneurysm size and hydrocephalus were similar in both groups (P = 0.61 and 0.64, respectively).
All procedures were successful in both groups. No patient undergoing surgery through a mMPT craniotomy needed a conversion to a standard PT craniotomy. Total operative time was significantly longer in the PT group (235.0 minutes) than in the mMPT group (166.6 minutes, P = 0.001) [Table 2]. The incidence of intraoperative bleeding from aneurysms, most of which were minor amount and needed no temporary proximal control, was 20% (4/21) in the PT group vs 16.7% (4/24) in the mMPT group (P = 0.76). The amount of intraoperative bleeding was significantly less in the mMPT group (110.4 ml, P = 0.03) than the PT group (216.1 ml). The rate of permanent operative morbidities, which were ischemic events in all patients, were similar in both groups (5% in the PT group vs 4.2% in the mMPT group, P = 0.92). A mean SIRS score was significantly lower in the mMPT group (0.96, P = 0.01) than in the PT group (1.81). Symptomatic vasospasm developed more frequently in the PT group (38.1%) than in the mMPT group (8.3%, P = 0.03). The rate of hydrocephalus requiring shunt implantation were similar in both groups (38.1% in the PT group vs 29.1% in the mMPT group, P = 0.54).
Complete obliteration of ruptured aneurysms was confirmed by postoperative 3D-CTA in all patients. There was no procedure-related death in this series. No patient experienced re-bleeding in either group.
Longer hospital stay was noted in patients treated through the PT group (47.3 days) in comparison with the mMPT group (38.8 days), but the difference did not reach statistical significance (P = 0.19). A outcome (mRS 0 to2) at discharge was more frequently seen in the mMPT group (91.7%) than in the PT group (70%), but this difference was not also statistically significant (P = 0.11).
Illustrative case presentation
A 39-year-old man was presented with Fisher group 3 SAH [Figure 2]a. A 3D-CTA of his head revealed an Acom aneurysm [Figure 2]b. Clipping for the aneurysm was performed through the mMPT craniotomy. The photograph and CT on postoperative day 1 showed no complication [Figure 2]c and [Figure 2]d. He did not experience symptomatic nor angiographical vasospasm. A complete obliteration of the aneurysm was confirmed by postoperative 3D-CTA [Figure 2]e. He was discharged from our institution 29 days after the onset with asymptomatic (mRS grade 0). The aesthetic result 3 months after the operation was favorable [Figure 2]f.
In this study, we demonstrated that the mMPT craniotomy is a less invasive approach for SAH patients with ruptured anterior circulation aneurysms than the standard PT craniotomy. mMPT also contributes to a significantly lower rate of postoperative symptomatic vasospasm and there is a marginally significant improvement in clinical outcomes.
The MPT craniotomy was first described by Figueiredo et al. They compared the area of surgical exposure and anatomic limits of MPT and PT craniotomies, and found that were comparable in both groups. They concluded that all anterior circulation aneurysms, which are eligible for the PT, can be treated by the MPT craniotomy. In our study, all consecutive ruptured anterior circulation aneurysms intended to treat through the mMPT craniotomy could be successfully clipped without a need for conversion to the standard PT craniotomy. And even in poor-grade SAH patients, drainage of cerebrospinal fluid through lumbar drainage catheter enabled us to perform aneurysmal clippings through the mMPT without difficulty. Thus, the mMPT craniotomy provides sufficient surgical corridors for the ruptured anterior circulation aneurysms.
A main advantage of the mMPT craniotomy, comparing with the PT craniotomy is its less invasiveness. After the publication of the ISAT, endovascular treatment of ruptured aneurysms has been widely accepted mainly because of its low invasiveness,[1–3] whereas coil instability is a major shortcoming of this modality.,,, Microsurgical clipping is durable modality for intracranial aneurysms, and has become less invasive through small craniotomies., However, there are no surgical data demonstrating improved invasiveness with smaller craniotomies, except for patient's satisfaction, cosmetics, and peripheral nerve functions.[10–12]
Clinical manifestations of a systemic immune response have been termed SIRS, a constellation of findings originally described in association with sepsis. The SIRS is induced by a number of non-infectious statuses, including trauma and surgical procedures., The SIRS score, delineated by a combination of abnormal heart rate, respiratory rate, body temperature, and peripheral blood leukocyte count, has been reported to reflect a surgical invasiveness and its prognosis in various conditions including SAH.,,,, Dhar et al. reported that the high SIRS score independently predicted symptomatic vasospasm and was associated with worse outcome in cases of SAH. In our study, the SIRS score at 24 hours after surgery was significantly lower in the mMPT group (P = 0.96) compared with the PT group, and this reflects the less decreased invasiveness of the mMPT craniotomy. This result rises from the minimal tissue exposure including skin, temporal muscle, skull, and brain, leading to a significant shorter operation time (P = 0.001) and decreased amount of intraoperative bleeding (P = 0.03). Thus, the decreased invasiveness of the mMPT resulted in the significantly lower rate of postoperative symptomatic vasospasm (P = 0.03) and marginally significant improved outcome (P = 0.11).
The rate of intraoperative bleeding from the treating aneurysm was about 20% in each groups of this study, which was relatively high compared to the previously reported incidence ranging from 7.9–19%.,, The rate in this study was comparable between the mMPT and the PT groups (P = 0.67). Thus, the intraoperative bleeding from the aneurysm was mainly because of the rigorous dissection of the ruptured aneurysms performed in either group, not because of smaller craniotomies through the mMPT. All of the bleeding from the aneurysm was not copious and did not need blood transfusion. It was controllable without the use of temporary clips. Also, none of the intraoperative bleeding contributed to a permanent operative morbidity.
The limitations of this study include the small sample size, retrospective analysis comprising patients recruited from a single center and the absence of randomization. The sample size was also not enough for subgroup analysis based on aneurysm site or size, and/or other characteristics. Moreover, all patients in this series were operated only by one neurosurgeon (T.I.). Thus, our results should be carefully generalized to SAH patients with ruptured anterior circulation aneurysms.
Though further studies will be needed to conclusively demonstrate the above, this is the first evidence showing the decreased invasiveness of the mMPT craniotomy for clipping of ruptured anterior circulation aneurysms compared to the PT craniotomy.
We compared the mMPT and the PT craniotomies in SAH patients with ruptured anterior circulation aneurysms. We found that the mMPT craniotomy was associated with a significant lower SIRS score at 24 hours after surgery, and contributes to the significant lower rate of postoperative symptomatic vasospasm and the marginally significant improvement in clinical outcomes.
This is the first evidence showing decreased invasiveness of the mMPT craniotomy for ruptured anterior circulation aneurysm surgery compared with the PT craniotomy.
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Conflicts of interest
There are no conflicts of interest.
[Figure 1], [Figure 2]
[Table 1], [Table 2]