Bone flap explantation, steroid use, and rates of infection in patients with epilepsy undergoing craniotomy for implantation of subdural electrodes

Clinical article

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Subdural implantation of electrodes is commonly performed to localize an epileptic focus. Whether to temporarily explant the bone plate and whether to treat patients with perioperative steroid agents is unclear. The authors' aim was to evaluate the utility and risk of bone plate explantation and perioperative steroid use.


The authors reviewed the records of all patients who underwent unilateral craniotomy for electrode implantation performed between November 2001 and June 2011 at their institution. Patients were divided into 3 groups: Group 1 (n = 24), bone explanted, no perioperative steroid use; Group 2 (n = 42), bone left in place, no perioperative steroid use; Group 3 (n = 25), bone left in place, steroid agents administered perioperatively. Complications, mass effect, and seizure rates were examined by means of statistical analysis.


Of 324 cranial epilepsy surgeries, 91 were unilateral subdural electrode implants that met our inclusion criteria. A total of 11 infections were reported, and there was a significantly higher rate of infection when the bone was explanted (8 cases [33.3%]) than when the bone was left in place (3 cases [4.5%], p < 0.01). Leaving the bone in place also increased the rate of asymptomatic subdural hematomas and frequency of seizures, although there was no increase in midline shift, severity of headache, or rate of emergency reoperation. The use of steroid agents did not appear to have an effect on any of the outcome measures.


Temporary bone flap explantation during craniotomy for implantation of subdural electrodes can result in high rates of infection, possibly due to the frequent change of hands in transferring the bone to the bone bank. Leaving the bone in place may increase the frequency of seizures and appearance of asymptomatic subdural hematomas but does not increase the rate of complications. These results may be institution dependent.

Abbreviation used in this paper:GEE = generalized estimating equation.

Article Information

Address correspondence to: Theodore H. Schwartz, M.D., Department of Neurosurgery, Weill Cornell Medical College, New York-Presbyterian Hospital, 525 East 68th Street, Box 99, New York, New York 10065. email:

Please include this information when citing this paper: published online April 26, 2013; DOI: 10.3171/2013.3.JNS121489.

© AANS, except where prohibited by US copyright law.



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    Latency to infection after last surgery in the 11 patients who had postoperative infections.



Adelson PDBlack PMMadsen JRKramer URockoff MARiviello JJ: Use of subdural grids and strip electrodes to identify a seizure focus in children. Pediatr Neurosurg 22:1741801995


Araki TOtsubo HMakino YElliott IIida KOchi A: Efficacy of dexamathasone on cerebral swelling and seizures during subdural grid EEG recording in children. Epilepsia 47:1761802006


Baldo STacconi L: Effectiveness and safety of subcutaneous abdominal preservation of autologous bone flap after decompressive craniectomy: a prospective pilot study. World Neurosurg 73:5525562010


Bhaskar IPZaw NNZheng MLee GYF: Bone flap storage following craniectomy: a survey of practices in major Australian neurosurgical centres. ANZ J Surg 81:1371412011


Hamer HMMorris HHMascha EJKarafa MTBingaman WEBej MD: Complications of invasive video-EEG monitoring with subdural grid electrodes. Neurology 58:971032002


Inamasu JKuramae TNakatsukasa M: Does difference in the storage method of bone flaps after decompressive craniectomy affect the incidence of surgical site infection after cranioplasty? Comparison between subcutaneous pocket and cryopreservation. J Trauma 68:1831872010


Iwama TYamada JImai SShinoda JFunakoshi TSakai N: The use of frozen autogenous bone flaps in delayed cranioplasty revisited. Neurosurgery 52:5915962003


Joaquim AFMattos JPNeto FCLopes Ade Oliveira E: [Bone flap management in neurosurgery.]. Revista Neurociencias 17:1331372009. (Portugese)


Lee WSLee JKLee SAKang JKKo TS: Complications and results of subdural grid electrode implantation in epilepsy surgery. Surg Neurol 54:3463512000


Matsuno ATanaka HIwamuro HTakanashi SMiyawaki SNakashima M: Analyses of the factors influencing bone graft infection after delayed cranioplasty. Acta Neurochir (Wien) 148:5355402006


Mocco JKomotar RJLadouceur AKZacharia BEGoodman RRMcKhann GM II: Radiographic characteristics fail to predict clinical course after subdural electrode placement. Neurosurgery 58:1201252006


Onal COtsubo HAraki TChitoku SOchi AWeiss S: Complications of invasive subdural grid monitoring in children with epilepsy. J Neurosurg 98:101710262003


Osawa MHara HIchinose YKoyama TKobayashi SSugita Y: Cranioplasty with a frozen and autoclaved bone flap. Acta Neurochir (Wien) 102:38411990


Sahjpaul RLMahon JWiebe S: Dexamethasone for morbidity after subdural electrode insertion—a randomized controlled trial. Can J Neurol Sci 30:3403482003


Sinclair DB: Prednisone therapy in pediatric epilepsy. Pediatr Neurol 28:1941982003


Van Gompel JJWorrell GABell MLPatrick TACascino GDRaffel C: Intracranial electroencephalography with subdural grid electrodes: techniques, complications, and outcomes. Neurosurgery 63:4985062008


Yoshikawa HYamazaki SAbe TOda Y: Liposteroid therapy for refractory seizures in children. J Child Neurol 15:7027042000




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