Head fixation device complications in pediatric neurosurgery

Head fixation device complications in pediatric neurosurgery

Head Fixation in pediatric neurosurgery is associated with complications.

They are widely used among pediatric neurosurgeons in patients younger than 5 years old. Guidelines for their safe use are not well defined despite common use and experience of significant complications associated with such devices 1).


Variability in the thickness of the developing cranium necessitates age-specific considerations to reduce the risk of adverse events. To suggest possible guidelines for the use of cranial fixation pins in children, Berry et al. surveyed neurosurgeons treating pediatric patients regarding their experience with such devices.

An Institutional Review Board-approved, 30-item multiple choice survey was provided by electronic mail to 605 neurosurgeons treating pediatric patients. The survey included specific questions regarding their experience with cranial fixation pins with respect to age ranges of patients, selection of pin size, type of pin pressure applied, and complications encountered.

One hundred sixty-four (27%) responses were received. One hundred fifty-eight of the 164 (96%) neurosurgeons reported using cranial fixation pins in their pediatric practice. Forty-four of the 164 (27%) apply fixation pins in patients aged 1 to 2 years. Eighty-two (50%) apply pins in patients aged 2 to 3 years, and 89 (54%) apply pins in patients aged 3 to 4 years. For patients aged 2 to 5 years old, the majority of responders use between 10 and 40 pounds of pressure, whereas for those older than 5 years of age, most use between 30 and 40 pounds of pressure. After age 10, patients are treated as adults. Eighty-nine of the 164 (54%) responders reported complications directly related to the use of cranial fixation pins, including cranial fracture, epidural or subdural hematoma, scalp laceration, or cerebrospinal fluid leak. One hundred fifty-four of the 164 (94%) neurosurgeons responded that they are not aware of any standard guidelines for cranial fixation pin use in pediatric patients. Seven (4%) who stated that they were aware of guidelines did not describe where they obtained those guidelines.

Cranial fixation pins are widely used among pediatric neurosurgeons in patients younger than 5 years old. Guidelines for their safe use are not well defined despite common use and experience of significant complications associated with such devices. 2).


Udayakumaran et al. applied a headband made of Plaster of Paris (POP) around the head and then applying the fixation pins of the fixation frame directly on to the POP.

They used this technique of head fixation successfully for infants with no complications 3).


Agrawal et al. described an extremely simple technique of head fixation for image-guided neurosurgery in young children in whom standard pin fixation cannot be used.

This involves positioning the head on a horseshoe headrest and using a ‘U-drape’ to fix the head to the headrest.

Over the last 5 years, this technique of head fixation (in conjunction with Stealthstation) has been used for various neurosurgical procedures in more than ten infants successfully 4).


Rubber plugs (usually used for antibiotic bottles) pierced by the skull pins are used to avoid intracranial penetration of the pins. The upper surface of the rubber plugs attached to the scalp contributes to support of the head. Four infants were successfully treated in a prone position with this technique 5).


Gupta adapted a standard Mayfield horseshoe headrest and cranial fixation system to allow simultaneous use of the headrest and three-point pin fixation. The system is compatible with most neuronavigational systems.

The combined horseshoe and pin system was used successfully in more than 30 patients ranging in age from 6 months to 14 years. No complications were encountered.

Rigid immobilization is achievable in the pediatric population, facilitating intracranial and frameless stereotaxy procedures 6).

Case series

Five of 766 children (0.65%) undergoing craniotomies with pin fixation of the head had depressed skull fractures and/or epidural hematomas from the pin fixation. Age ranged from 2.6 to 7.5 years; all fractures were temporal and occurred during posterior fossa craniotomies 7).


Lee et al. examined complications over the past 6 years, and encountered 5 children with depressed skull fractures secondary to the application of a skull clamp fixation device. There were 3 boys and 2 girls with ages ranging from 3 to 8 years (mean 5.8 years). Two patients had brainstem gliomas, 2 patients had hypothalamic gliomas and 1 patient had a medulloblastoma. Four of the children required separate cranial procedures for the exploration and elevation of the depressed fractures. There were no sequelae associated with the depressed fractures. We conclude that skull clamp fixation devices are safe, but should be used with caution in the pediatric patient. In addition, we present several modifications of existing skull clamps which may decrease the risk of depressed skull fractures 8).

Case reports

An 11-year-old girl diagnosed with non-communicating hydrocephalus, caused by a posterior fossa tumor. During the surgery, complications were found in the form of acute epidural hematoma due to head fixation pins. So, the operation was stopped. An emergent CT scan was carried out and showed a bilateral skull fracture and a massive right-sided epidural hematoma. An emergency craniotomy for clot removal was performed and five days later, a second surgery was carried out uneventfully for the residual tumor. The patient fully recovered after the second surgery.

Complications due to the use of a pinhead fixation are easier to occur in pediatric patients because the bones are thinner and need a more careful strategy when pinning. With prompt identification of any complications and earlier treatment, a good outcome will be achieved.

Parenrengi et al. compared this case report with published literature in order to suggest a way to prevent this complication.

Skull fractures and associated epidural hematomas in pediatric patients need to be considered as possible complications of the pin-type head fixation application. The head fixation devices in pediatric need to be used with great caution and knowing the risk factors, safe technique for application and management of complications will prevent a worse outcome 9).


A 4-year-old girl who sustained a depressed skull fracture by penetration of a pin of the head holder. The fracture was noted at the end of the surgery performed for treatment of a cerebellar astrocytoma and was managed conservatively.

Several factors seem to be involved in the production of this complication as are faulty application of the pins, excessive pin pressure, skull thinning, young patient’s age, and pathological conditions that evolve with long-standing raised intracranial pressure 10).


A 5-month-old girl with a growing lesion in the right thalamus and basal ganglia underwent stereotactic biopsy, which disclosed an anaplastic astrocytoma. To avoid insertion of the four stereotactic frame fixation pins through the infant’s skin and into bone, the pins were advanced into the hollowed end of rubber tops obtained from Vacutainer blood sampling tubes. The pressure applied to the skin was diffused through the rubber onto a wide skin surface, obviating skin puncture or bone deformation. This technique provided firm head fixation, and target accuracy was confirmed on postoperative imaging. This technique is safe and should permit the use of conventional stereotactic techniques in young infants 11).

References

1) , 2)

Berry C, Sandberg DI, Hoh DJ, Krieger MD, McComb JG. Use of cranial fixation pins in pediatric neurosurgery. Neurosurgery. 2008 Apr;62(4):913-8; discussion 918-9. doi: 10.1227/01.neu.0000318177.95288.cb. PubMed PMID: 18496197.
3)

Udayakumaran S, Onyia CU. Customizable rigid head fixation for infants: technical note. Childs Nerv Syst. 2016 Jan;32(1):159-61. doi: 10.1007/s00381-015-2896-y. Epub 2015 Sep 4. PubMed PMID: 26337702.
4)

Agrawal D, Steinbok P. Simple technique of head fixation for image-guided neurosurgery in infants. Childs Nerv Syst. 2006 Nov;22(11):1473-4. Epub 2006 Sep 19. PubMed PMID: 17047964.
5)

Aoki N, Sakai T. Modified application of three-point skull clamp for infants. Neurosurgery. 1989 Oct;25(4):660-2. PubMed PMID: 2677825.
6)

Gupta N. A modification of the Mayfield horseshoe headrest allowing pin fixation and cranial immobilization in infants and young children. Neurosurgery. 2006 Feb;58(1 Suppl):ONS-E181; discussion ONS-E181. PubMed PMID: 16462615.
7)

Vitali AM, Steinbok P. Depressed skull fracture and epidural hematoma from head fixation with pins for craniotomy in children. Childs Nerv Syst. 2008 Aug;24(8):917-23; discussion 925. doi: 10.1007/s00381-008-0621-9. Epub 2008 Apr 4. PubMed PMID: 18389258.
8)

Lee M, Rezai AR, Chou J. Depressed skull fractures in children secondary to skull clamp fixation devices. Pediatr Neurosurg. 1994;21(3):174-7; discussion 178. PubMed PMID: 7803306.
9)

Parenrengi MA, Adhiatmadja F, Arifianto MR, Apriawan T, Fauzi AA, Servadei F. Bilateral skull fracture with massive epidural hematoma secondary to pin-type head fixation in a pediatric patient: Case report and review of the literature. Int J Surg Case Rep. 2019 Aug 13;62:43-49. doi: 10.1016/j.ijscr.2019.07.079. [Epub ahead of print] PubMed PMID: 31445499.
10)

Martínez-Lage JF, Almagro MJ, Serrano C, Mena L. Depressed skull fracture by a three-pin head holder: a case illustration. Childs Nerv Syst. 2011 Jan;27(1):163-5. doi: 10.1007/s00381-010-1213-z. Epub 2010 Jun 24. PubMed PMID: 20574740.
11)

Kondziolka D, Adelson PD. Technique of stereotactic biopsy in a 5-month-old child. Childs Nerv Syst. 1996 Oct;12(10):615-8. PubMed PMID: 8934022.

p64 Flow Modulation Device

p64 Flow Modulation Device

(Phenox, Bochum, Germany).

https://phenox.net/products/p64.html

The p64 Flow Modulation Device is a flow diverter. It allows complete deployment and full recoverability. This provides added safety and security.

• Complete deployment and recoverability ensures optimal placement

• Greater neck coverage due to the 64 Nitinol wire braid maximizes hemodynamic flow effect in the aneurysm

• Visualization is achieved by 2 helical strands along entire length of the implant and eight proximal markers

• p64 is mechanically detached once optimally placed

• Implanted via a 0.027“ ID microcatheter

The p64 is a flow modulation device designed to be used in endovascular treatment of intracranial aneurysms. There is limited data on the long-term effectiveness of the device. A study of Sirakov et al. sought to determine the safety and long-term efficacy of this device.

A retrospective review of aprospectively maintained database was performed to identify all patients treated with a p64 between March 2015 and November 2018 at University Hospital St. Ivan Rilski. Anatomical features, intraprocedural complications, clinical, and angiographic outcomes were also taken into account and reviewed.

A total of 72 patients with 72 aneurysms who met the inclusion criteria were identified. Device placement was successful in all patients. Follow-up angiographic imaging at 6 months showed complete occlusion (O’Kelly-Marotta grading scale [OKM] D) in 55 (76.3%) patients, subtotal aneurysmal filling (OKM B) in 10 (13.8%) patients, and neck remnant (OKM C) in 7 (9.7%) patients. Catheter angiography at 12 months was available for 70 patients (97.2%) and of these patients 91.4% of the aneurysms were completely occluded (OKM D) (64/72). Delayed angiography at 24 months was available for 68 patients (94.4%) and of these 98.5% (67/68) had completely occluded aneurysms. A 36-month angiography was available for 61 patients (84.4%) by which point all aneurysms had been completely occluded (100%). Permanent morbidity due to delayed aneurysmal rupture occurred in one patient (1.38%). The mortality rate was 0%. Self-limiting mild intimal hyperplasia was seen in 2 patients (2.72%).

Treatment of intracranial aneurysms with a p64 flow modulation device is safe and effective with a high success rate and only infrequent complication 1).


Girdhar et al., reported the thrombogenic potential of the following flow diversion devices measured experimentally in a novel human blood in-vitro pulsatile flow loop model: Pipeline™ Flex Embolization Device (Pipeline), Pipeline™ Flex Embolization Device with Shield Technology™ (Pipeline Shield), Derivo Embolization Device (Derivo), and P64 Flow Modulation Device (P64). Thrombin generation (Mean ± SD; μg/mL) was measured as: Derivo (28 ± 11), P64 (21 ± 4.5), Pipeline (21 ± 6.2), Pipeline Shield (0.6 ± 0.1) and Negative Control (1.5 ± 1.1). Platelet activation (IU/μL) was measured as: Derivo (4.9 ± 0.7), P64 (5.2 ± 0.7), Pipeline (5.5 ± 0.4), Pipeline Shield (0.3 ± 0.1), and Negative Control (0.9 ± 0.7). They found that Pipeline Shield had significantly lower platelet activation and thrombin generation than the other devices tested (p < .05) and this was comparable to the Negative Control (no device, p > .05). High resolution scanning electron microscopy performed on the intraluminal and cross-sectional surfaces of each device showed the lowest accumulation of platelets and fibrin on Pipeline Shield relative to Derivo, P64, and Pipeline. Derivo and P64 also had higher thrombus accumulation at the flared ends. Pipeline device with Phosphorylcholine surface treatment (Pipeline Shield) could mitigate device material related thromboembolic complications 2).


In preliminary in vivo experiments, antithrombogenic hydrophilic coating (HPC) p64 FDSs appeared to be biocompatible, without acute inflammation 3).


Treatment with p64 is associated with an overall rate of 8.5% moderate in stent stenosis (ISS) (50-75%) and 2.7% severe ISS (>75%), which is comparable with the rate of ISS reported in the literature for other flow diverting stents. There is a tendency for ISS to spontaneously improve over time 4)

References

1)

Sirakov S, Sirakov A, Bhogal P, Penkov M, Minkin K, Ninov K, Hristov H, Karakostov V, Raychev R. The p64 Flow Diverter-Mid-term and Long-term Results from a Single Center. Clin Neuroradiol. 2019 Aug 9. doi: 10.1007/s00062-019-00823-y. [Epub ahead of print] PubMed PMID: 31399749.
2)

Girdhar G, Ubl S, Jahanbekam R, Thinamany S, Belu A, Wainwright J, Wolf MF. Thrombogenicity assessment of Pipeline, Pipeline Shield, Derivo and P64 flow diverters in an in vitro pulsatile flow human blood loop model. eNeurologicalSci. 2019 Jan 8;14:77-84. doi: 10.1016/j.ensci.2019.01.004. eCollection 2019 Mar. PubMed PMID: 30723811; PubMed Central PMCID: PMC6350389.
3)

Martínez Moreno R, Bhogal P, Lenz-Habijan T, Bannewitz C, Siddiqui A, Lylyk P, Hannes R, Monstadt H, Henkes H. In vivo canine study of three different coatings applied to p64 flow-diverter stents: initial biocompatibility study. Eur Radiol Exp. 2019 Jan 22;3(1):3. doi: 10.1186/s41747-018-0084-z. PubMed PMID: 30671686; PubMed Central PMCID: PMC6342750.
4)

Aguilar Pérez M, Bhogal P, Henkes E, Ganslandt O, Bäzner H, Henkes H. In-stent Stenosis after p64 Flow Diverter Treatment. Clin Neuroradiol. 2018 Dec;28(4):563-568. doi: 10.1007/s00062-017-0591-y. Epub 2017 May 9. PubMed PMID: 28488025; PubMed Central PMCID: PMC6245240.

DERIVO® Embolisation Device

DERIVO® Embolisation Device

The Derivo® embolisation device (DED) is a new-generation flow diverter designed to treat intracranial aneurysms, consisting of a flexible structure and a surface modification that aims to reduce thrombogenicity.

The safety and efficacy of flow diverters and their long-term clinical outcome must be investigated.

Girdhar et al., reported the thrombogenic potential of the following flow diversion devices measured experimentally in a novel human blood in-vitro pulsatile flow loop model: Pipeline™ Flex Embolization Device (Pipeline), Pipeline™ Flex Embolization Device with Shield Technology™ (Pipeline Shield), Derivo Embolization Device (Derivo), and P64 Flow Modulation Device (P64). Thrombin generation (Mean ± SD; μg/mL) was measured as: Derivo (28 ± 11), P64 (21 ± 4.5), Pipeline (21 ± 6.2), Pipeline Shield (0.6 ± 0.1) and Negative Control (1.5 ± 1.1). Platelet activation (IU/μL) was measured as: Derivo (4.9 ± 0.7), P64 (5.2 ± 0.7), Pipeline (5.5 ± 0.4), Pipeline Shield (0.3 ± 0.1), and Negative Control (0.9 ± 0.7). They found that Pipeline Shield had significantly lower platelet activation and thrombin generation than the other devices tested (p < .05) and this was comparable to the Negative Control (no device, p > .05). High resolution scanning electron microscopy performed on the intraluminal and cross-sectional surfaces of each device showed the lowest accumulation of platelets and fibrin on Pipeline Shield relative to Derivo, P64, and Pipeline. Derivo and P64 also had higher thrombus accumulation at the flared ends. Pipeline device with Phosphorylcholine surface treatment (Pipeline Shield) could mitigate device material related thromboembolic complications 1).


Kaschner et al., retrospectively analyzed all patients with ruptured dissecting and blister aneurysms treated with the Derivo between February 2016 and July 2018. Procedural details, complications, morbidity within 30 days, and angiographic aneurysm occlusion rates, initially and after six months, were assessed.

In 10 patients 11 ruptured dissecting and blister aneurysms were treated with 12 Derivos as monotherapy. No aneurysm rebleeding was observed at follow-up. One treatment-related complication occurred including a coil perforation of an additionally treated aneurysm. One patient died due to brain edema. Initial digital subtraction angiography revealed complete (O’Kelly-Marotta grading scale D) and favorable (OKM D+C) occlusion rate in three aneurysms. Six-month follow-up for digital subtraction angiography and clinical evaluation was available in 6/9 patients with complete (OKM D) occlusion in all aneurysms (6/6). Favorable (modified Rankin Scale [mRS] ≤ 2) and moderate (mRS 3) clinical outcome after a mean follow-up of 10 months was observed in six and two patients, respectively.

Endovascular treatment with the Derivo in ruptured dissecting and blister aneurysms revealed a sufficient initial division of aneurysms from the circulation without rebleeding. The Derivo is associated with high procedural and clinical short-term safety 2).


Kaschner et al., did a retrospective analysis of 32 patients with complex RIAs and UIAs treated with Derivo from Nov.2015 to Dec.2018. Clinical safety was defined as absence of death, transient attack, absence of minor and major stroke, and Derivo associated hemorrhage. Treatment efficacy was assessed angiographically (DSA) immediately after treatment and at 6 month follow-up according to the O’Kelly Marotta (OKM) grading scale (A=total filling to D=no filling; prolongation of stasis 1=arterial to 3=venous phase).

32 patients with 39 aneurysms were treated with 42 Derivos. In 5 aneurysms additional coiling was performed. Deployment was technically successful in all cases. Two patients developed a procedure related minor stroke (one transient). In 1 patient bleeding due to an inflammatory aneurysmatic wall process occurred 20 days after retreatment and in 1 patient a stroke due to instent thrombosis occurred when dual platelet inhibition (PI) was switched to permanent single PI 12 month after FD treatment. No treatment related deaths were observed. Initial DSA revealed OKMD,n=3; C,n=6; B,n=5; A,n=25. Six-month follow-up for DSA and clinical evaluation was available in 20/32 patients (62.5%), 26/39 aneurysms (66.7%) and revealed 73.1% complete and 3.8% subtotal occlusion (OKMD:19/26, OKMC3:1/26).

Treatment of complex RIAs and UIAs with the new generation Derivo appeared to be safe and effective in this single centre case series for ruptured and unruptured intracranial aneurysms. Immediate DSA revealed a significant flow modulation; and 6-month follow-up showed a high occlusion rate 3).


In a retrospective study of 59 consecutive patients (mean age: 53 years, 81% women) treated with the DED for 59 aneurysms (mean size: 8.1 mm) between November 2015 and February 2018 at 3 German tertiary care centers. Goertz et al., evaluated the rate of ischemic stroke, functional outcome, and angiographic results during a 1-year follow-up period.

Deployment of the DED was successful in all cases. Adverse events were observed in 6 procedures (10.2%), of which 2 were symptomatic (3.4%). No delayed ischemic or hemorrhagic events occurred during the 1-year follow-up and there were no deaths. Permanent morbidity due to in-stent thrombosis and consecutive ischemic stroke occurred in 1 patient (1.7%). Complete (O’Kelly-Marotta grading scale D) and favorable (O’Kelly-Marotta grading scale C+D) aneurysm occlusion was obtained in 70.5% (31/44) and 88.7% (39/44) at 6 months and 82.8% (24/29) and 100% (29/29) at 12 months, respectively.

The results demonstrated that treatment of intracranial aneurysms with the DED is associated with low rates of ischemic complications and adequate aneurysm occlusion at 1-year follow-up 4).


Between February 2016 and March 2018, 10 patients (median age 54.5 years, seven women) with 11 aneurysms were treated with the DED at three neurovascular centers. Procedural details, complications, morbidity, and aneurysm occlusion (O’Kelly-Marotta scale, OKM) were retrospectively reviewed.

Among 11 aneurysms treated, there were nine anterior circulation and two posterior circulation aneurysms. Aneurysm morphology was saccular in four cases, dissecting in three, blister-like in three, and fusiform in one. In each case, a single DED was implanted and deployment was technically successful without exception. Adjunctive coiling was performed in two aneurysms. We observed one in-stent thrombosis, presumably due to low response to clopidogrel 4 days after the procedure, which remained with a mild hemiparesis after aspiration thrombectomy. No further thromboembolic or hemorrhagic events occurred. Favorable outcome (modified Rankin scale score ≤2) at last follow-up was achieved in all patients. Among 10 aneurysms available for angiographic follow-up, complete aneurysm occlusion (OKM D) was obtained in nine cases (90.0%).

In this pilot study, endovascular treatment of ruptured intracranial aneurysms with the DED was feasible and not associated with any incidence of rebleeding 5).


In a study, the clinical outcomes of using the DED on 182 aneurysms are presented Material and Methods: In total, 146 patients with 182 aneurysms were treated with DED. The mean age of the participants was 51.5 years; among them, 46 (31.5%) presented with acute subarachnoid haemorrhage. The mean aneurysm size was 8.3 mm, and 12 aneurysms were involved the vertebrobasilar system. Ophthalmic aneurysms account for most internal carotid artery (ICA) aneurysms.

The Glasgow Coma Scale (GCS) score of 12 patients was 15. DED was associated with a mortality rate of 2.7% and permanent morbidity rate of 3.4%, and a complete aneurysm occlusion rate was achieved in 78.7% of cases after 7.02 months

The DED device is a new-generation flow diverter with excellent opening behaviour and navigational benefits. The results indicated a safe aneurysm occlusion with optimum morbidity and mortality values despite the fact that almost one-third of the patients presented with subarachnoid haemorrhage 6).


Martínez-Galdámez et al., presented the first clinical use of the largest flow diverter available, the 6×50 mm DERIVO embolization device (Acandis GmbH & Co. KG, Pforzheim, Germany), into the arterial circulation for a cervical internal carotid artery endovascular reconstruction. This is a new device for large or fusiform aneurysms requiring flow diversion, especially located in the vertebrobasilar system or extracranial segments 7).

References

1)

Girdhar G, Ubl S, Jahanbekam R, Thinamany S, Belu A, Wainwright J, Wolf MF. Thrombogenicity assessment of Pipeline, Pipeline Shield, Derivo and P64 flow diverters in an in vitro pulsatile flow human blood loop model. eNeurologicalSci. 2019 Jan 8;14:77-84. doi: 10.1016/j.ensci.2019.01.004. eCollection 2019 Mar. PubMed PMID: 30723811; PubMed Central PMCID: PMC6350389.
2)

Kaschner MG, Petridis A, Turowski B. Single-center experience with the new generation Derivo Embolization Device in ruptured dissecting and blister aneurysms. Acta Radiol. 2019 Jun 5:284185119852731. doi: 10.1177/0284185119852731. [Epub ahead of print] PubMed PMID: 31166695.
3)

Kaschner MG, Petridis A, Turowski B. Single center experience with the new generation derivo embolization device for ruptured and unruptured intracranial aneurysms. J Neurosurg Sci. 2019 May 6. doi: 10.23736/S0390-5616.19.04678-2. [Epub ahead of print] PubMed PMID: 31079436.
4)

Goertz L, Dorn F, Kraus B, Borggrefe J, Forbrig R, Schlamann M, Liebig T, Turowski B, Kabbasch C. Improved Occlusion Rate of Intracranial Aneurysms Treated with the Derivo Embolization Device: One-Year Clinical and Angiographic Follow-Up in a Multicenter Study. World Neurosurg. 2019 Mar 23. pii: S1878-8750(19)30815-0. doi: 10.1016/j.wneu.2019.03.137. [Epub ahead of print] PubMed PMID: 30910748.
5)

Goertz L, Dorn F, Kraus B, Borggrefe J, Schlamann M, Forbrig R, Turowski B, Kabbasch C. Safety and efficacy of the Derivo Embolization Device for the treatment of ruptured intracranial aneurysms. J Neurointerv Surg. 2019 Mar;11(3):290-295. doi: 10.1136/neurintsurg-2018-014166. Epub 2018 Aug 6. PubMed PMID: 30082333.
6)

Daglioglu E, Akmangit İ, Acik V, Alagoz F, Sayin B, Uckun OM, Belen AD, Arat A. The Experience of the Derivo® Embolisation Device in Intracranial Aneurysms. Turk Neurosurg. 2019 Mar 27. doi: 10.5137/1019-5149.JTN.25776-19.2. [Epub ahead of print] PubMed PMID: 31049921.
7)

Martínez-Galdámez M, Rodríguez C, Hermosín A, Crespo-Vallejo E, Monedero G, Chaviano J, Zheng B. Internal Carotid Artery Reconstruction with a “Mega Flow Diverter”: First Experience with the 6×50 mm DERIVO Embolization Device. Neurointervention. 2018 Sep;13(2):133-137. doi: 10.5469/neuroint.2018.00934. Epub 2018 Aug 31. PubMed PMID: 30196686; PubMed Central PMCID: PMC6132039.
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