Tailored antiplatelet therapy in stent assisted coiling for unruptured aneurysms: a nationwide registry study.

BACKGROUND: Antiplatelet therapy, where regimens are tailored based on platelet function testing, has been introduced into neurointerventional surgery. This nationwide registry study evaluated the effect and safety of tailored antiplatelet therapy in stent assisted coiling for unruptured aneurysms compared with conventional therapy using a standard regimen. METHODS: This study enrolled 1686 patients in 44 participating centers who received stent assisted coiling for unruptured aneurysms between January 1, 2019 and December 31, 2019. The standard regimen (aspirin and clopidogrel) was used for all patients in the conventional group (924, 19 centers). The regimen was selected based on platelet function testing (standard regimen for clopidogrel responders; adding cilostazol or replacing clopidogrel with other thienopyridines (ticlopidine, prasugrel, or ticagrelor) for clopidogrel non-responders) in the tailored group (762, 25 centers). The primary outcome was thromboembolic events. Secondary outcomes were bleeding and poor outcomes (increase in modified Rankin Scale score). Outcomes within 30 days after coiling were compared using logistic regression analysis. RESULTS: The thromboembolic event rate was lower in the tailored group than in the conventional group (30/762 (3.9%) vs 63/924 (6.8%), adjusted OR 0.560, 95% CI 0.359 to 0.875, P=0.001). The bleeding event rate was not different between the study groups (62/762 (8.1%) vs 73/924 (7.9%), adjusted OR 0.790, 95% CI 0.469 to 1.331, P=0.376). Poor outcomes were less frequent in the tailored group (12/762 (1.6%) vs 34 (3.7%), adjusted OR 0.252, 95% CI 0.112 to 0.568, P=0.001). CONCLUSION: Tailored antiplatelet therapy in stent assisted coiling for unruptured aneurysms reduced thromboembolic events and poor outcomes without increasing bleeding.

Treatment for Hemifacial Spasm Associated with a Dissecting Vertebral Artery Aneurysm Requiring Microvascular Decompression in Addition to Endovascular Trapping: A Case Report with Literature Review.

BACKGROUND: The treatment protocol for hemifacial spasm (HFS) associated with dissecting vertebral artery aneurysm (DVAA) has not been established. CASE DESCRIPTION: A-42-year-old man with left HFS underwent endovascular trapping for a DVAA that was identified on brain imaging. Although the dissecting segment was treated successfully, the HFS persisted for 3 months, and subsequently microvascular decompression (MVD) was needed. The posteroinferior cerebellar artery (PICA) was found to be interposed between the root exit zone of the facial nerve and DVAA during surgery. After pulling out the PICA, the HFS ceased immediately. CONCLUSION: HFS associated with DVAA should be considered carefully before formulating a treatment strategy. Moreover, the cause of pulsatile compression may not be visible on brain imaging, and MVD surgery may be indicated in such cases.

Predicting Arachnoid Membrane Descent in the Chiasmatic Cistern in the Treatment of Pituitary Macroadenoma.

OBJECTIVE: Preoperative prediction of the arachnoid membrane descent in pituitary surgery is useful for achieving gross total removal and avoiding cerebrospinal fluid leakage resulting from tearing of the arachnoid membrane in the chiasmatic cistern. In this study, we analyzed the patterns of arachnoid membrane descent during or after pituitary tumor surgery and identified the factors related to this descent. METHODS: Analysis was restricted to pituitary macroadenomas not extending into the third ventricle or over the internal carotid artery. To minimize confounding factors, patients who underwent revision surgery, those who had a torn arachnoid during operation or small medial diaphragma sellae (DS) opening, and subtotal resections were excluded. We enrolled 41 consecutive patients in this retrospective analysis. The degree of arachnoid descent was categorized using intraoperative videos. Preoperative magnetic resonance findings, including tumor height, suprasellar extension, and variables including DS area and medial opening size, tumor composition, and displacement of the pituitary stalk and gland were evaluated to determine their correlations with arachnoid membrane descent. RESULTS: Arachnoid membrane descent was significantly correlated with DS area and medial opening size. Based on T2-weighted images (T2WI) magnetic resonance (MR) images, tumor composition was significantly associated with arachnoid membrane descent. Other factors were not significantly correlated with arachnoid membrane descent. CONCLUSION: T2WI of tumor composition and preoperative MR imaging of DS area and medial opening provided valuable information regarding arachnoid membrane descent. These parameters may serve as fundamental measures to facilitate complete resection of pituitary macroadenomas.

Efficacy of Acupuncture Treatment to Prevent Cerebral Vasospasm After Subarachnoid Hemorrhage: A Double-Blind, Randomized Placebo-Controlled Trial.

Objectives: To investigate the efficacy of acupuncture in preventing cerebral vasospasm following aneurysmal subarachnoid hemorrhage (SAH) and explore its underlying mechanism. Design: A randomized, double-blinded, and placebo-controlled trial. Setting/Location: Subjects were recruited from Kyung Hee University Hospital at Gangdong, Seoul, Korea Subjects: A total of 50 patients admitted with acute SAH. Interventions: The study group received acupuncture treatments (n = 25), while the control group underwent mock transcutaneous electrical nerve stimulation and sham acupuncture (n = 25) six times/week for 2 weeks. Outcome measures: The primary outcome was the incidence of delayed ischemic neurologic deficit (DIND), and secondary measurements included angiographic vasospasm, vasospasm-related infarction, modified Rankin Scale score, and plasma nitric oxide (NO) and endothelin-1 (ET-1) levels. Results: The study group treated with acupuncture showed a lower incidence of DIND (9.1%) than the control group (20.8%); however, this difference in the incidence of DIND was not statistically significant. The study group demonstrated better clinical outcomes, especially in functional recovery. Significant alterations in plasma NO and ET-1 levels after the 2-week intervention were observed only in the study group. Conclusions: Their study shows that acupuncture treatment improved functional recovery after SAH and could potentially prevent cerebral vasospasm. These effects could be attributed to the recovery of endothelial dysfunction by acupuncture through modulating the plasma NO and ET-1 levels. The study protocol has been registered on www.clinicaltrials.gov (NCT02275949).

Acupuncture attenuates postoperative inflammation in patients after craniotomy: A prospective, open-label, controlled trial.

BACKGROUND: It is important to manage inflammation after craniotomy. It may be prudent to reduce the excessive usage of antibiotics and to add supplementary treatments like acupuncture, which would be effective and safe. However, there are only a few studies available to date on the effects of acupuncture on anti-inflammatory response after craniotomy. The aim of this study was to explore the anti-inflammatory effects of acupuncture in patients after a craniotomy. METHODS: This study was a single-center, prospective, open-label, controlled trial. Forty-four subjects who underwent craniotomy for an unruptured aneurysm, facial spasm, or brain tumor were allocated to either an acupuncture group or a control group. Both groups received postoperative routine care in the Department of Neurosurgery. The subjects in the acupuncture group also received a total of 6 acupuncture treatments sessions within 8 days after craniotomy. Acupuncture treatments included acupuncture, electroacupuncture, and intradermal acupuncture. The serum interleukin (IL)-1ß and IL-6, tumor necrosis factor-α (TNF-α), C-reactive protein (CRP), and erythrocyte sedimentation rate levels were assessed four times within 7 days after surgery. The presence of fever, use of additional antibiotics, presence of infection including pneumonia or urinary tract infection, and safety were also reviewed. RESULTS: The IL-1ß levels of subjects who underwent aneurysmal clipping were significantly lower in the acupuncture group (P = .02). TNF-α levels of subjects who underwent aneurysmal clipping at the seventh postoperative day were also significantly lower in the acupuncture group (P = .03). Six cases of fever of unknown origin were observed in the control group, while none were seen in the acupuncture group, revealing that the incidence of fever was significantly lower in the acupuncture group (P = .02). No adverse events occurred during the trial. CONCLUSION: Acupuncture showed a possibility of alleviating inflammation by attenuating the levels of proinflammatory cytokines and significantly reduced the incidence of fever of unknown origin in patients after craniotomy. Acupuncture would be suitable as an adjunctive therapy to alleviate inflammation after craniotomy.

Endovascular Treatments Performed Collaboratively by the Society of Korean Endovascular Neurosurgeons Members : A Nationwide Multicenter Survey.

OBJECTIVE: Since less invasive endovascular treatment was introduced to South Korea in 1994, a considerable proportion of endovascular treatments have been performed by neuroradiology doctors, and endovascular treatments by vascular neurosurgeons have recently increased. However, few specific statistics are known regarding how many endovascular treatments are performed by neurosurgeons. Thus, authors compared endovascular treatments collaboratively performed by vascular neurosurgeons with all cases throughout South Korea from 2013 to 2017 to elucidate the role of neurosurgeons in the field of endovascular treatment in South Korea. METHODS: The Society of Korean Endovascular Neurosurgeons (SKEN) has issued annual reports every year since 2014. These reports cover statistics on endovascular treatments collaboratively or individually performed by SKEN members from 2013 to 2017. The data was requested and collected from vascular neurosurgeons in various hospitals. The study involved 77 hospitals in its first year, and 100 in its last. National statistics on endovascular treatment from all over South Korea were obtained from the Healthcare Bigdata Hub website of the Health Insurance Review & Assessment Service based on the Electronic Data Interchange (EDI) codes (in the case of intra-arterial (IA) thrombolysis, however, statistics were based on a combination of the EDI and I63 codes, a cerebral infarction disease code) from 2013 to 2017. These two data sets were directly compared and the ratios were obtained. RESULTS: Regionally, during the entire study period, endovascular treatments by SKEN members were most common in Gyeonggido, followed by Seoul and Busan. Among the endovascular treatments, conventional cerebral angiography was the most common, followed by cerebral aneurysmal coiling, endovascular treatments for ischemic stroke, and finally endovascular treatments for vascular malformation and tumor embolization. The number of endovascular treatments performed by SKEN members increased every year. CONCLUSION: The SKEN members have been responsible for the major role of endovascular treatments in South Korea for the recent 5 years. This was achieved through the perseverance of senior members who started out in the midst of hardship, the establishment of standards for the training/certification of endovascular neurosurgery, and the enthusiasm of current SKEN members who followed. To provide better treatment to patients, we will have to make further progress in SKEN.

Characteristic Signs on T2*-Based Imaging and Their Relationship with Results of Reperfusion Therapy for Acute Ischemic Stroke: A Systematic Review and Evidence to Date.

PURPOSE: Characteristic signs - the susceptibility vessel sign (SVS) and the prominent hypointense vessel sign (PHVS) - on T2*-based magnetic resonance imaging (T2*MRI) can be seen for acute ischemic stroke with large artery occlusion. In this study, we investigated the evidence to support our hypothesis that these findings may help to predict outcomes after reperfusion therapy. MATERIALS AND METHODS: We searched for papers describing SVS and PHVS in patients treated with reperfusion therapy for acute ischemic stroke, and their functional/radiologic outcomes were systematically reviewed. RESULTS: Nine studies on the SVS and six studies on the PHVS were included. The pooled odds ratio (OR) of recanalization after intravenous thrombolysis or mechanical thrombectomy was not significantly different with the presence of SVS (OR, 0.615; 95% confidence interval [CI], 0.335-1.131 and OR, 0.993; 95% CI, 0.629-1.567). The OR of favorable functional outcome after reperfusion therapy in terms of the presence of PHVS varied (0.083 to 1.831) by study. CONCLUSION: Our meta-analysis of the published data showed that a SVS was not a predictive factor for recanalization after reperfusion therapy for acute ischemic stroke. Currently, the data available on T2*MRI are too limited to warrant reperfusion therapy in routine practice. More data are needed from studies with randomized treatment allocation to determine the role of T2*MRI.

Staged Endovascular Occlusion of a Posterior Communicating Artery-Cavernous Sinus Fistula and a Basilar Artery-Cavernous Sinus Fistula Associated with Traumatic Pseudoaneurysms: Technical Consideration and Literature Review.

BACKGROUND: Traumatic injury of the posterior communicating artery or the basilar artery causing arteriovenous fistulae is rare. CASE DESCRIPTION: Here we report an unusual case of the coincidence of a posterior communicating artery-cavernous sinus fistula and a basilar artery-cavernous sinus fistula associated with traumatic pseudoaneurysms of the posterior communicating and basilar arteries. The fistulas and pseudoaneurysms were obliterated completely after staged endovascular surgery via a transarterial and transvenous route. CONCLUSIONS: To our knowledge, this is the first such report worldwide.

Alberta Stroke Program Early CT Score in the Prognostication after Endovascular Treatment for Ischemic Stroke: A Meta-analysis.

PURPOSE: The Alberta Stroke Program Early CT Score (ASPECTS) was devised to quantify the extent of early ischemic changes in the middle cerebral artery territory on brain CT. We performed a systematic review and meta-analysis of studies that presented clinical outcomes and baseline ASPECTS in ischemic stroke patients managed with endovascular methods to validate the use of ASPECTS for risk prognostication. MATERIALS AND METHODS: We searched the MEDLINE, EMBASE, and Cochran databases for observational or interventional studies that reported clinical outcomes and baseline ASPECTS in ischemic stroke patients treated with endovascular methods. Data were pooled to perform a meta-analysis for comparisons of clinical outcomes between high and low ASPECTS patients. RESULTS: A meta-analysis of 13 studies (six observational and seven interventional) revealed favorable outcomes (mRS sore 0-2 at 90 days) for high baseline ASPECTS (odds ratio=2.22; 95% CI: 1.74-2.86). CONCLUSION: High ASPECTS is a predictor of favorable outcome after endovascular therapy for ischemic stroke.

Anti-inflammatory and immune regulatory effects of acupuncture after craniotomy: study protocol for a parallel-group randomized controlled trial.

BACKGROUND: Despite recent advances in the medical and surgical fields, complications such as infection, pneumonia, or brain swelling may occur after a craniotomy. In some patients, perioperative antibiotic prophylaxis causes adverse effects such as itching, rash, or digestive conditions. Certain patients still develop infections severe enough to require a repeat operation despite antibiotic prophylaxis. Acupuncture has been used to treat inflammatory conditions, and many basic and clinical studies have provided evidence of its anti-inflammatory and immune regulatory effects. The aim of this study is to explore the effects of acupuncture on inflammation and immune function after craniotomy. METHODS: This trial will be a single-center, parallel-group clinical trial. Forty patients who underwent craniotomy for an unruptured aneurysm, facial spasm, or a brain tumor will be allocated to either the study or the control group. The study group will receive conventional management as well as acupuncture, electroacupuncture, and intradermal acupuncture, which will start within 48 h of the craniotomy. The patients will receive a total of six sessions within 8 days. The control group will only receive conventional management. The primary outcome measure will be the C-reactive protein levels, while the secondary outcomes will be the serum erythrocyte sedimentation rate and the tumor necrosis factor-α, interleukin (IL)-1ß, and IL-6 levels measured at four different time points: within 48 h prior to the craniotomy and on days 2, 4, and 7 after surgery. The presence of fever and infection, the use of additional antibiotics, the presence of infection, including pneumonia or urinary tract infection, and safety will also be investigated. DISCUSSION: In this trial, we will observe whether acupuncture has anti-inflammatory and immune regulatory effects after a craniotomy. If our study yields positive results and a placebo-controlled study also finds favorable results following our study, acupuncture could be recommended as an adjunctive therapy after a craniotomy. TRIAL REGISTRATION: ClinicalTrials.gov: NCT02761096 . Registered on 27 April 2016.

Evaluating Transient Hemifacial Spasm that Reappears After Microvascular Decompression Specifically Focusing on the Real Culprit Location of Vascular Compression.

BACKGROUND: Even although microvascular decompression is the standard treatment for hemifacial spasm (HFS), the treatment is not always 100% successful. Some patients experience the reappearance of HFS after temporary relief after surgery. We analyzed our data to elucidate the reasons for and prognosis of HFS reappearance, specifically focusing on exact compressive location of the facial nerve. METHODS: The patients were divided into 2 groups: group A, the patients whose symptoms of spasm disappeared immediately after surgery but recurred within a month, and group B, the patients whose symptoms of spasm completely disappeared and never recurred. We adopted the terms of subdivision in the facial nerve root exit zone: RExP, root exit point; AS, attached segment; RDP, root detachment point; TZ, transition zone; and CP, distal cisternal portion. RESULTS: Among 115 patients, 56 (48.7%) belonged to group A and 59 (51.3%) to group B. In 54 of the 56 patients in group A (96.4%), the reappearing HFS disappeared gradually over several weeks. The precise location of compression in group A was at the RExP in 46.4% of the patients, AS in 33.9%, RDP in 16.1%, and TZ in 3.6%, and the RExP compression was significantly more frequent compared with in group B. CONCLUSIONS: After microvascular decompression for HFS, almost half of the patients experienced transient HFS recurrence despite sufficient decompression of the facial nerve. However, in most cases, recurrent HFS gradually resolved over a period. Based on the compression location, the surgeon could anticipate recurrence of transient HFS.

Giant Intrathoracic Meningocele and Breast Cancer in a Neurofibromatosis Type I Patient.

Intrathoracic meningoceles are relatively rare entities found in patients with neurofibromatosis type I (NF1). Given that both the BRCA1 and NF-1 genes are located on the same long arm of chromosome 17, one would expect concurrence of neurofibromatosis and breast cancer. However, incidence of such co-disorders is very rare in the literature. Here, the authors report a case of a 50-year-old female patient with NF-1 and concurrent cancer of the left breast, who had a huge bilobulated intrathoracic meningocele with thoracic dystrophic scoliosis, treated surgically via a posterior-only approach for the meningocele and spinal deformity in the same setting.

Incomplete Clipping Resulting from Scissoring of the Clip Blades during Treatment of a Large Atheromatous Aneurysm.

The cerebral aneurysm 'clip scissoring' phenomenon resulting from clip blade twisting is an unpredictable surgical complication. Additionally, incomplete clipping resulting from the presence of an atherosclerotic wall in the neck of the aneurysm can also cause unforeseen problems. Here, the authors present an unusual case of incomplete clipping of a large, atheromatous aneurysm resulting from clip scissoring, which was treated with additional endovascular coiling.

Clinical Characteristics and Prognostic Factors in Hemophiliacs with Intracranial Hemorrhage: A Single-Center, Retrospective Experience.

Intracranial hemorrhage (ICH) is the most serious bleeding event that occurs in patients with hemophilia; its estimated mortality rate is approximately 20 %, accounting for the largest number of deaths from bleeding. We conducted this single-center, retrospective study to examine the characteristics of and prognostic factors in patients with hemophilia. A comprehensive review of 12 cases of intracranial hemorrhage (ICH) among 10 patients. All 12 cases of ICH in the 10 patients were treated with clotting factor concentrates. Three patients had intracerebral hemorrhage that required neurosurgical intervention. After presenting with ICH, two pediatric patients developed antibodies to clotting factors. Two adult patients with intracerebral hemorrhage died, and the mortality rate was thus 20.0 % (2/10) in our clinical series. Prompt and intensive treatment with clotting factor concentrates may significantly lower the mortality rate among patients with hemophilia presenting with ICH. Our results showed a better prognosis in pediatric patients with intracerebral hemorrhage. Clinicians should pay special attention to the possible development of inhibitors after intensive treatment in pediatric patients. Further studies are needed to examine methods for administering clotting factor concentrates and to determine whether neurosurgical intervention is essential in each case.

Extended Pneumocephalus after Drainage of Chronic Subdural Hematoma Associated with Intracranial Hypotension : Case Report with Pathophysiologic Consideration.

Chronic subdural hematoma (SDH) is a well-known disease entity and is traditionally managed with surgery. However, when associated with spontaneous intracranial hypotension (SIH), the treatment strategy ought to be modified, as classical treatment could lead to unwanted consequences. A 59-year-old man presented with a case of SIH that manifested as a bilateral chronic SDH. He developed fatal extensive pneumocephalus and SDH re-accumulation as a complication of burr-hole drainage. Despite application of an epidural blood patch, the spinal cerebrospinal fluid leak continued, which required open spinal surgery. Chronic SDH management should not be overlooked, especially if the exact cause has not been determined. When chronic SDH assumed to be associated with SIH, the neurosurgeon should determine the exact cause of SIH in order to effectively correct the cause.

Endovascular Treatment of Vertebral Artery Dissecting Aneurysms That Cause Subarachnoid Hemorrhage : Consideration of Therapeutic Approaches Relevant to the Angioarchitecture.

OBJECTIVE: Intracranial ruptured vertebral artery dissecting aneurysms (VADAns) are associated with high morbidity and mortality when left untreated due to the high likelihood of rebleeding. The present study aimed to establish an endovascular therapeutic strategy that focuses specifically on the angioarchitecture of ruptured VADAns. METHODS: Twenty-three patients with ruptured VADAn received endovascular treatment (EVT) over 7 years. The patient group included 14 women (60.9%) and 9 men (39.1%) between the ages of 39 and 72 years (mean age 54.2 years). Clinical data and radiologic findings were retrospectively analyzed. RESULTS: Four patients had aneurysms on the dominant vertebral artery. Fourteen (61%) aneurysms were located distal to the posterior inferior cerebellar artery (PICA). Six (26%) patients had an extracranial origin of the PICA on the ruptured VA, and 2 patients (9%) had bilateral VADAns. Eighteen patients (78%) were treated with internal coil trapping. Two patients (9%) required an adjunctive bypass procedure. Seven patients (30%) required stent-supported endovascular procedures. Two patients experienced intra-procedural rupture during EVT, one of which was associated with a focal medullary infarction. Two patients (9%) exhibited recanalization of the VADAn during follow-up, which required additional coiling. No recurrent hemorrhage was observed during the follow-up period. CONCLUSION: EVT of ruptured VADAns based on angioarchitecture is a feasible and effective armamentarium to prevent fatal hemorrhage recurrence with an acceptable low risk of procedural complications. Clinical outcomes depend mainly on the pre-procedural clinical state of the patient. Radiologic follow-up is necessary to prevent hemorrhage recurrence after EVT.

Spontaneous Occluded Anterior Communicating Artery Aneurysm during Coil Embolization Treated with One Coil Insertion into Remaining Stump.

Spontaneous thrombosis of a ruptured aneurysm during coil embolization is a rare event, and some reports on recanalization of a spontaneous occluded ruptured aneurysm have been published. We report on a case of a 54-year-old male who presented with a subarachnoid hemorrhage due to rupture of a small aneurysm of the anterior communicating artery (ACoA). Cerebral angiography confirmed the presence of the ACoA aneurysm, but, during coil embolization, the aneurysm was near completely occluded with a remaining small neck. A small coil was inserted into the remaining stump of the neck to prevent recanalization, and the angiographic result at 1 year after coil embolization showed complete obliteration of the aneurysm.

Rebleeding of Ruptured Intracranial Aneurysms in the Immediate Postoperative Period after Coil Embolization.

OBJECTIVE: Early rebleeding after coil embolization of ruptured intracranial aneurysms is rare, however serious and fatal results of rebleeding have been reported. We studied the incidence and angiographic and clinical characteristics of rebleeding of ruptured aneurysms occurring in the immediate postoperative period after coil embolization. MATERIALS AND METHODS: We analyzed patients who had aneurysmal subarachnoid hemorrhage and underwent coil embolization. Patients with dissecting aneurysms, blood blister-like aneurysms, fusiform aneurysms, and pseudoaneurysms were excluded. This study included 330 consecutive patients. The clinical and radiological data of 7 of these patients with acute rebleeding after coil embolization were reviewed. RESULTS: The incidence of rebleeding of ruptured aneurysms after coil embolization was 2.1% (7/330), and all cases of rebleeding occurred in the immediate postoperative period within 3 days after coiling. The radiological characteristics were as follows: anterior communicating artery (ACoA) aneurysm (71.4%, 5/7); presence of intracerebral hemorrhage (ICH, 71.4%, 5/7); dome-to-neck ratio < 2 (42.9%, 3/7); presence of bleb (42.9%, 3/7); and subtotal occlusion of aneurysm after coiling (14.3%, 1/7). A thrombolytic agent was administered in 1 patient and continued anticoagulation was performed in 2 patients. Rebleeding patients showed a very poor outcome (Glasgow Outcome Scale 1, 85.7%, 6/7). CONCLUSION: The prognosis of early rebleeding was very poor. Location of aneurysms on ACoA, the unilateral hypoplasia of A1 segment, presence of ICH and bleb, and adverse events during the procedure were probably associated with early rebleeding of ruptured intracranial aneurysms in the immediate postoperative period after coil embolization.

Analyses Using Micro-CT Scans and Tissue Staining on New Bone Formation and Bone Fusion According to the Timing of Cranioplasty via Frozen Autologous Bone Flaps in Rabbits : A Preliminary Report.

OBJECTIVE: The timing of cranioplasty and method of bone flap storage are known risk factors of non-union and resorption of bone flaps. In this animal experimental study, we evaluated the efficacy of cranioplasty using frozen autologous bone flap, and examined whether the timing of cranioplasty after craniectomy affects bone fusion and new bone formation. METHODS: Total 8 rabbits (male, older than 16 weeks) were divided into two groups of early cranioplasty group (EG, 4 rabbits) and delayed cranioplasty group (DG, 4 rabbits). The rabbits of each group were performed cranioplasty via frozen autologous bone flaps 4 weeks (EG) and 8 weeks (DG) after craniectomy. In order to obtain control data, the cranioplasty immediate after craniectomy were made on the contralateral cranial bone of the rabbits (control group, CG).The bone fusion and new bone formation were evaluated by micro-CT scan and histological examination 8 weeks after cranioplasty on both groups. RESULTS: In the micro-CT scans, the mean values of the volume and the surface of new bone were 50.13±7.18 mm(3) and 706.23±77.26 mm(2) in EG, 53.78±10.86 mm(3) and 726.60±170.99 mm(2) in DG, and 31.51±12.84 mm(3) and 436.65±132.24 mm(2) in CG. In the statistical results, significant differences were shown between EG and CG and between DG and CG (volume : p=0.028 and surface : p=0.008). The histological results confirmed new bone formation in all rabbits. CONCLUSION: We observed new bone formation on all the frozen autologous bone flaps that was stored within 8 weeks. The timing of cranioplasty may showed no difference of degree of new bone formation. Not only the healing period after cranioplasty but the time interval from craniectomy to cranioplasty could affect the new bone formation.