Minimally Invasive Thumb-sized Pterional Craniotomy for Surgical Clip Ligation of Unruptured Anterior Circulation Aneurysms

Podsumowanie

Minimally invasive thumb-sized pterional craniotomy for aneurysm clipping has afforded our patients with a shorter hospital stay at a lower cost compared to the national average.

Streszczenie

Less invasive surgical approaches for intracranial aneurysm clipping may reduce length of hospital stay, surgical morbidity, treatment cost, and improve patient outcomes. We present our experience with a minimally invasive pterional approach for anterior circulation aneurysms performed in a major tertiary cerebrovascular center and compare the results with an aged matched dataset from the Nationwide Inpatient Sample (NIS). From August 2008 to December 2012, 22 elective aneurysm clippings on patients ≤55 years of age were performed by the same dual fellowship-trained cerebrovascular/endovascular neurosurgeon. One patient (4.5%) experienced transient post-operative complications. 18 of 22 patients returned for follow-up imaging and there were no recurrences through an average duration of 22 months. A search in the NIS database from 2008 to 2010, also for patients aged ≤55 years of age, yielded 1,341 hospitalizations for surgical clip ligation of unruptured cerebral aneurysms. Inpatient length of stay and hospital charges at our institution using the minimally invasive thumb-sized pterional technique were nearly half that of NIS (length of stay: 3.2 vs 5.7 days; hospital charges: $52,779 vs. $101,882). The minimally invasive thumb-sized pterional craniotomy allows good exposure of unruptured small and medium-sized supraclinoid anterior circulation aneurysms. Cerebrospinal fluid drainage from key subarachnoid cisterns and constant bimanual microsurgical techniques avoid the need for retractors which can cause contusions, localized venous infarctions, and post-operative cerebral edema at the retractor sites. Utilizing this set of techniques has afforded our patients with a shorter hospital stay at a lower cost compared to the national average.

Wprowadzenie

Surgical clip ligation had been the mainstay of treatment for intracranial aneurysms but has been recently supplanted mostly by less invasive endovascular techniques.^1,2 Clinical trials including the International Study of Unruptured Intracranial Aneurysms (ISUIA-1 and ISUIA-2), and the International Subarachnoid Aneurysm Trial (ISAT) have demonstrated lower morbidity and mortality, reduced length of hospital stay, and lower overall expense, with endovascular treatment compared to surgical clip ligation.^3–5 However, the higher aneurysm recurrence rate after endovascular therapy has led to the examination of the cumulative risk to the patients compared to surgical clip ligation.^3,4 Surgical treatment remains an important modality for aneurysm therapy, particularly for anterior circulation aneurysms that have morphologies that may be difficult to treat with endovascular means.

Unlike advancements in endovascular devices, few advances in surgical techniques have been made recently. Techniques to make surgical treatment less invasive have included the supraorbital craniotomy combined with the eyebrow incision for anterior circulation aneurysms and “retractorless surgery” to minimize surgical trauma to the brain during aneurysm clipping.^6–8 These less invasive surgical approaches may reduce length of hospital stay, surgical morbidity, treatment cost, and improve patient outcomes.⁹

Here, we present our experience with a minimally invasive approach to surgical clip ligation of unruptured intracranial aneurysms using a pterional approach for anterior circulation aneurysms performed in a major tertiary cerebrovascular center and compare the results with an age matched dataset from the Nationwide Inpatient Sample (NIS). The surgical technique will be reviewed, including patient preparation, brain relaxation, sylvian fissure dissection, and closure. Post-operative care and discharge requirements will also be outlined.

Protokół

NOTE: Prior to performing this procedure, obtain all required institutional approval and patient consent.

1. Surgical Technique

1. Induce patient with general anesthesia.
2. Place radial arterial line for blood pressure monitoring.
3. Place patient in the supine position on the operating room table.
4. After the head is clamped into the Mayfield Head holder using standard techniques for a pterional craniotomy, position the head 30°-45° with the ipsilateral side up towards the ceiling, except for anterior-communicating artery aneurysms in which the head is placed at 60º to allow for better visualization across the interhemispheric fissure.
5. Position the neck midline and translate anteriorly to maximize jugular venous drainage to prevent cerebral edema and then extend the head to position the ipsilateral zygoma at the highest point—this allows for frontal lobe relaxation and elevation from the orbital roof during dissection without the use of retractors.
6. Clip the hair in preparation for standard pterional scalp incision; use about a one to two inch strip behind the hairline.
7. Sterilely prep the skin and drape the surgical area according to standard of care.
8. Perform a standard curved scalp incision for a pterional approach extending from the midline of the scalp behind the hairline with a gentle curve posteriorly and inferiorly towards the tragus ending it about 3 mm anterior to the tragus and at the level of the superior edge of the zygoma. Perform this incision down to the skull above the superior temporal line and to the muscle fascia at the level of the temporalis muscle.
9. Use electrocautery for scalp hemostasis with the bipolar device.
10. Cut the temporalis muscle down to the skull using the bovie monopolar electrocautery device.
11. Raise a myocutaneous flap keeping the temporalis muscle attached to the undersurface of the scalp for now. Fish-hooks are used to evert the flap after the temporalis muscle is elevated from the skull using a combination of monopolar electrocautery and a periosteal elevator.
12. Perform an inverse subfascial dissection in the avascular plane from the undersurface of the myocutaneous flap using Metzenbaum scissors, keeping the fascia and subfacsial fat pad with the scalp to avoid injury to the facial nerve.
13. Secure the temporalis muscle posteriorly and inferiorly to expose the pterional region with “star” fishhooks.
14. Keep all components of the myocutaneous flap moist with wetted gauze.
15. Drill a single temporal 5 mm burr-hole at the posterior-most aspect of the planned craniotomy with a 2 mm cutting burr so that the foot plate of the side-cutting drill can be inserted into this hole and then use a side-cutting drill with a foot plate to remove the thumb-sized (approximately 3 x 4 cm) kidney-shaped craniotomy centered anteriorly around the pterion.
16. Using a No. 1 Penfield, separate the dura on all sides of the pterion and have an assistant gently retract the dura away from the bone surface that is being drilled to minimize risk of penetrating the dura and causing cortical injury.
17. Remove the pterion with a drill: anteriorly, until the superior and lateral aspects of the orbital roof are smooth and flattened down to the outer cortical table of bone, without entering the orbit, to maximize subfrontal exposure; medially, drill until the superior orbital fissure dura is exposed and remove any small pieces of bone that would interfere with medial exposure using either a drill bit or hand-held Lempert bone cutting device. Ensure that excellent hemostasis of all soft-tissue and bone surfaces has been obtained to avoid blood dripping into the intradural space during brain dissection and aneurysm exposure, using electrocaurtery and bone wax as needed, before opening the dura.
18. Gently elevate the dura and use a No. 11 scalpel to penetrate the dura and then use dural scissors to create a “C-shaped” opening in the dura with the base at the pterion. Secure the dura flat against the outer cortical bone of the orbit without having redundant dural leaflets that would otherwise obscure visualization of the proximal Sylvian Fissure and subfrontal region. This can be performed by using 4-0 Surgilons sutures to tack the dura to the scalp.

2. Brain Relaxation

1. Give 25-50 g of Mannitol at the time of bone flap removal to relax the brain if anesthesia agrees that the blood pressure will tolerate diuresis.
   NOTE: This will allow time for the diuresis to occur and ultimately will relax the brain to help maximize gravity dependent brain retraction during dissection.
2. Keep End-Tidal pCO₂ between 30-35 mm Hg to achieve slight hypercapnea. NOTE: This will safely allow for brain relaxation and maximize gravity dependent brain retraction during dissection.
3. Evacuate cerebrospinal fluid (CSF) to promote brain relaxation by opening the arachnoid cisterns in the interoptic, carotid-optic, and carotid-oculomotor cisterns and patiently suction CSF until the desired brain relaxation has been achieved.
   NOTE: This typically takes about 1 min; no lumbar drain is needed with this technique and it dramatically opens the surgical corridors.

3. Sylvian Fissure Dissection

1. Bring the intra-operative microscope with the mouthpiece into the field using sterile techniques. Also bring surgical chairs with arm support into the field sterilely to maximize bimanual dexterity and to prevent surgeon arm and hand fatigue.
   NOTE: The mouthpiece should be adjusted before draping so that the surgeon can move the microscope with the mouth while simultaneously looking through the ocular pieces.
2. Perform dissection.
   NOTE: For anterior communicating artery aneurysms, no Sylvian Fissure dissection is required and minimal (2-3 mm in extreme cases only, but this is a rare occurrence) to no gyrus rectus resection is needed using only subfrontal dissection; all other supraclinoid anterior circulation aneurysm locations (including posterior communicating artery) require <1 cm proximal Sylivan Fissure dissection to expose the supraclinoid internal carotid artery, its branches (posterior communicating and anterior choroidal arteries), the internal carotid artery terminus, the A1 and M1 origins, and the proximal A2 and M2 segments distal to their respective bifurcations. Total Sylvian Fissure exposure was dime-size (1 cm x 1 cm) and no brain retractors were used for any of the cases reported. Gravity dependent brain relaxation was sufficient for excellent exposure of the soft tissue structures and vasculature needed to perform surgical clip ligation in the areas discussed above.
3. Using bimanual manipulation with surgical microinstruments gently open the arachnoid corridors, holding the brain tissue aside with the edge of the instrument handles or suction device as needed through this exposure.
   NOTE: The senior author's preference is to use a 4-French Fukishima suction tip in the non-dominant hand and in the dominant hand bipolar bayonettes for blunt dissection or microscissors for sharp dissection. Moistened Telfa strips are placed on the brain surface at the site of manipulation to prevent cortical injury. Cottonoids often stick to the brain surface and can’t be easily advanced deeper as the dissection progresses, without causing mild cortical injury.
4. Use the mouthpiece on the operating microscope frequently to adjust the scope and focus length as needed while keeping both hands in the field.
5. Secure the aneurysm in standard fashion, using the suction most often in the non-dominant hand to maintain the surgical corridor and visualization free of CSF.
6. After clip placement, perform intra-operative Doppler of the aneurysm dome to confirm cessation of flow as well as the inflow and outflow vessels to confirm flow and carefully examine the aneurysm neck and parent vessels. We reserve intra-operative digital subtraction angiography (DSA) for anterior communicating artery aneurysms and those clipped aneurysms where inflow, outflow, or aneurysm neck cannot be visualized completely or there is a concern with intra-operative Doppler. Intra-operative DSA is preferred over indocyanine green (ICG) angiography because when multiple aneurysm clips are used to reconstruct the aneurysm neck, the clip can obstruct visualization. NOTE: Once the aneurysm has been securely clipped, the microscope is removed from the field and the brain irrigated with normal saline solution to minimize the amount of pneumocephalus after closure.
7. After inspecting the clip for aneurysm occlusion with the Doppler, the aneurysm dome is perforated with a 22 G needle attached to intravenous tubing and a 10 ml syringe and manually suction aspirated to confirm aneurysm occlusion.
8. Reapproximate the native dura with 4-0 surgilon and cover with a synthetic dural substitute if a watertight closure is not able to be obtained properly.
9. Secure bone plates with a metal plating system per standard of care.
10. Secure the frontal edge of the bone flap flush against the native bone to avoid space between the two which would not be cosmetically pleasing after the tissues heal.
11. Reapproximate the temporalis muscle fascia with interrupted 2-0 Vicryl sutures. Secure the top of the temporalis muscle with a 2-0 Vicryl stitch to the frontal metal plate to reapproximate it to the superior temporal line.
12. Reapproximate the galea using 3-0 Vicryl sutures and close the scalp in a standard fashion using either staples, nylon, or prolene. Dress with sterile bandages per surgeon preference.

4. Post-treatment Care

1. Admit patient to the intensive care unit after treatment and mobilize with the nursing staff as soon as sedation or general anesthesia has worn off enough to do so, typically within 6 hr of extubation.
2. Order physical and occupational therapy to begin post-operative day one in order to assess the patient for safe discharge to home if there were any concerns by the nursing staff.
3. Discharge the patient when criteria are met: pain controlled with only oral medications, voiding independently, ambulating independently, and tolerating oral food intake.

Wyniki

Currently, at our institution over 150 aneurysms are treated annually. From August 2008 to December 2012, 22 elective aneurysm clippings using this minimally invasive thumb-sized pterional craniotomy technique for supraclinoidal aneurysms on patient’s ≤55 years of age were performed by the same dual fellowship-trained cerebrovascular/endovascular neurosurgeon that developed this technique (EMD) (Table 1). This age group was chosen as earlier trials have shown that surgical treatment of aneury...

Dyskusje

Surgical clip ligation of intracranial aneurysms remains a relevant and important option in treating certain types of aneurysms, though this role has been diminishing over the past several years as endovascular technology becomes safer and more efficacious. Endovascular treatment has surpassed surgery for cerebral aneurysms, yet the higher recurrence rate after endovascular treatment, the occasional need for surgical treatment after aneurysm recurrence from failed endovascular treatment, specific morphologies making endo...

Materiały

Name	Company	Catalog Number	Comments
Mayfield Infinity skull clamp	Integra	A-1114
Mayfield table attachment	Integra	A-1018
4-French Fukishima suction tip	Integra	R-8986
Periosteal elevator (Langenbeck)	Codman	65-1116
Metzenbaum scissors	Codman	36-5023
Malis dissector, round angled	Codman	80-1541
Penfield dissector, style 1	Codman	65-1015
Lempert bone rongeur	Codman	19-1232
Malis Irrigation Module	Codman	Module 1000
Bovie monopolar electrocautery device	Codman
Insulated blade for electrocautery device	Covidien	E1455
Fish-hook retractors	Lone Star	3350-8G
Pneumatic drill	Medtronic	Midas Rex MR7
Side-cutting drill	Medtronic	F2/8TA23
Fluted legend match head tool	Medtronic	10MH30
Surgical scalpel No. 10,11,15	Bard-Parker	0029064 (No.10), 0018291 (No.11), 0018043 (No.15)
Intra-operative microscope with mouthpiece	Leica
Microscissors	V. Mueller	NL3785-034(st), NL3785-035(cvd)
Rhoton dissector, #2	V. Mueller	NL3785-002
Telfa strips	American Surgical	#80-09 (1/2x3), #80-04 (1/4x3)
Aneurysm clip	Aesculap
Raney clip applier	Aesculap	FF012R
Synthes Matrix metal plating system	Synthes
Braided absorbable surgical sutures (Vicyrl)	Ethicon	J790D (3-0), J743D (4-0)
Braided nylon nonabsorbable surgical sutures (Nurolon) 4-0	Ethicon	C584D
Doppler System	Mizuho	07-150-02