Genomic analysis of human brain metastases treated with stereotactic radiosurgery reveals unique signature based on treatment failure.

Stereotactic radiosurgery (SRS) has been shown to be efficacious for the treatment of limited brain metastasis (BM); however, the effects of SRS on human brain metastases have yet to be studied. We performed genomic analysis on resected brain metastases from patients whose resected lesion was previously treated with SRS. Our analyses demonstrated for the first time that patients possess a distinct genomic signature based on type of treatment failure including local failure, leptomeningeal spread, and radio-necrosis. Examination of the center and peripheral edge of the tumors treated with SRS indicated differential DNA damage distribution and an enrichment for tumor suppressor mutations and DNA damage repair pathways along the peripheral edge. Furthermore, the two clinical modalities used to deliver SRS, LINAC and GK, demonstrated differential effects on the tumor landscape even between controlled primary sites. Our study provides, in human, biological evidence of differential effects of SRS across BM's.

Endovascular intervention for the treatment of epistaxis: cone beam CT review of anatomy, collateral, and treatment implications/efficacy.

Epistaxis is common, impacting more than half the population, and can require procedural intervention in approximately 10% of cases. With an aging population and increasing use of antiplatelets and anticoagulants, severe epistaxis is likely to increase in frequency significantly over the next two decades. Sphenopalatine artery embolization is rapidly becoming the most common type of procedural intervention. The efficacy of endovascular embolization is dependent on a refined understanding of the anatomy and collateral physiology of this circulation as well as the impact of temporizing measures such as nasal packing and inflation of a nasal balloon. Likewise, safety is dependent on a detailed appreciation of collateralization with the internal carotid artery and ophthalmic artery. Cone beam CT imaging has the resolution to enable a clear visualization of the anatomy and collateral circulation associated with the arterial supply to the nasal cavity, in addition to assisting with hemorrhage localization. We present a review of epistaxis treatment, a detailed description of anatomic and physiologic considerations informed by cone beam CT imaging, and a proposed protocol for sphenopalatine embolization for which there is currently no standard.

Papillary glioneuronal tumor presenting with low-pressure hydrocephalus from intraventricular spread: Case Report.

Papillary glioneuronal tumors are a rare and typically benign entity with pathological and radiographic complexity. Presentation can mimic other neoplasms, making diagnosis more challenging. The literature to date describes the clinical understanding, diagnostic, therapeutic, and prognostic characteristics of this limited number of patients. In this article, we report an unusual case of a glioneuronal tumor with multifocal presentation, normal pressure hydrocephalus-like symptoms, and large peritumoral parenchymal cysts, which guided the surgical approach. This unusual presentation has not previously been reported and adds valuable information to the clinical recognition and management literature.

Genomic Analysis of Human Brain Metastases Treated with Stereotactic Radiosurgery Under the Phase-II Clinical Trial (NCT03398694) Reveals DNA Damage Repair at the Peripheral Tumor Edge.

Stereotactic Radiosurgery (SRS) is one of the leading treatment modalities for oligo brain metastasis (BM), however no comprehensive genomic data assessing the effect of radiation on BM in humans exist. Leveraging a unique opportunity, as part of the clinical trial (NCT03398694), we collected post-SRS, delivered via Gamma-knife or LINAC, tumor samples from core and peripheral-edges of the resected tumor to characterize the genomic effects of overall SRS as well as the SRS delivery modality. Using these rare patient samples, we show that SRS results in significant genomic changes at DNA and RNA levels throughout the tumor. Mutations and expression profiles of peripheral tumor samples indicated interaction with surrounding brain tissue as well as elevated DNA damage repair. Central samples show GSEA enrichment for cellular apoptosis while peripheral samples carried an increase in tumor suppressor mutations. There are significant differences in the transcriptomic profile at the periphery between Gamma-knife vs LINAC.

Artificial intelligence aneurysm measurement tool finds growth in all aneurysms that ruptured during conservative management.

BACKGROUND: Cerebral aneurysm rupture is associated with high rates of morbidity and mortality. Detecting aneurysms at high risk of rupture is critical in management decision making. Rupture risk has traditionally been associated with size-measured as a maximum dimension. However, aneurysms are morphologically dynamic, a characteristic ignored by large prospective aneurysm risk studies. Manual measurement is challenging and fraught with error. We used an artificial intelligence (AI) measurement tool to study aneurysms that ruptured during conservative management to detect changes in size not appreciated by manual linear measurement. METHODS: A single practice database with >5000 aneurysms was queried. Patients followed conservatively for an unruptured aneurysm were identified using appropriate diagnosis codes. This cohort was screened for subsequent rupture using procedure codes. Only patients with two vascular imaging studies before rupture were included. RESULTS: Five patients met the criteria. All patients had aneurysm enlargement, two of which were not detected from manual linear measurements, including adjudication and analysis, during a multidisciplinary neurovascular conference in a high volume practice. Maximum dimension increased at a minimum of 1.8% (range 1.8-63.3%) from the first scan to the last, and aneurysm volume increased at a minimum of 5.9% (5.9-385.5%), highlighting the importance of volumetric measurement. CONCLUSIONS: AI-enabled volumetric measurements are more sensitive to changes in size and detected enlargement in all aneurysms that ruptured during conservative management. This finding has major implications for clinical practice and methods used for interval aneurysm measurement in patients being conservatively followed.

Technical video: Onyx-18 embolization of spinal epidural arteriovenous Fistula using the scepter-Mini balloon catheter.

Spinal arteriovenous fistulas (AVFs) account for approximately 70% of all vascular spinal malformations and commonly develop in the lateral epidural space at the epidural /radicular venous junction. The fistula is located close to the spinal nerve root where a radiculomeningeal artery shunts to a radicular vein. Increased venous pressure leads to decreased spinal venous drainage and venous congestion causing progressive myelopathy, bowel/bladder incontinence and erectile dysfunction. Treatment consists of surgical occlusion of the intradural vein, or endovascular embolization, which has a reported success rate of 25%-75%.1 Endovascular failure can occur with inadequate embolic penetration of the nidus and the proximal segment of the draining vein, or premature reflux of the liquid embolic agent.The use of a dual-lumen balloon microcatheter offers advantage in these cases given the ability to push liquid embolysate more distally during balloon inflation. The Scepter Mini is a new dimethyl-sulfoxide (DMSO)-compatible dual-lumen balloon microcatheter with a distal-tip outer diameter of 1.6 Fr and a nominal balloon diameter of 2.2 mm, facilitating atraumatic navigation and safer balloon inflation. Limited neurointerventional experience using the Scepter Mini in predominantly cerebrovascular cases has reported favorable navigability and flow arrest2, 3 Although Onyx is rarely used for spinal AVF embolization, success has been reported considering the well-known favorable experience in cerebral cases.1, 4, 5We present one of the first cases of Onyx embolization of a spinal dural AVF through a Scepter Mini in a patient with progressively worsening lower extremity sensorimotor dysfunction. Operators should be aware of radiculomedullary arteries arising at the same level or at adjacent levels to avoid unintentional Onyx migration during balloon inflation.

The Use of a Pipeline Embolization Device for Treatment of a Ruptured Dissecting Middle Cerebral Artery M3/M4 Aneurysm: Challenges and Technical Considerations.

Prompt, effective treatment is necessary following aneurysmal subarachnoid hemorrhage to prevent recurrent rupture, which is thought to double mortality. Atypical ruptured aneurysms, such as blister or dissecting pseudoaneurysms, or those that are unusually distal in the middle cerebral artery (MCA) are challenging to treat with either open or endovascular options, though the pipeline embolization device (PED) has shown promise in multiple case series. We present a case of a ruptured dissecting pseudoaneurysm in the distal MCA (distal M3/proximal M4) prefrontal division in an healthy young patient (<60 years) successfully treated with a PED. The PED was chosen both as the only vessel sparing option in the young patient as well as for its potential as a vessel sacrifice tool if the pseudoaneurysm was felt to be incompletely treated, which in this case was not necessary-though would have leveraged the thrombogenicity of the device as a therapeutic advantage.

Recurrent Primary Intrasellar Paraganglioma.

We describe a case of an 81-year-old male presenting with bitemporal visual field defects and blurry vision in the right eye. The patient was found to have a recurrent primary paraganglioma in the sellar and suprasellar region requiring a repeat transsphenoidal endoscopic resection. Immunohistochemical examination confirmed paraganglioma with the classic zellballen appearance which stained positive for chromogranin, synaptophysin, and S-100 in the periphery. Paragangliomas (PGLs) in the sella turcica are a rare entity; only 19 cases have ever been reported in the literature. PGLs in the sellar region are often misdiagnosed or diagnosed in a delayed fashion. Earlier diagnosis of this locally aggressive tumor and meticulous debulking can prevent morbidity secondary to the tumor's compressive effects. This report highlights the effectiveness of surgical interventions in treatment of paragangliomas. More research is still needed to determine the need for adjuvant therapies such as radiation.

Bipolar Coagulation Aneurysm Dome Remodeling (Aneurysmorrhaphy) for Middle Cerebral Artery Aneurysms.

Adequate visualization of the proximal and distal vessels and clip reconstruction of the bifurcation with complete aneurysm neck exclusion are often difficult in the setting of bulbous small- and moderate-sized middle cerebral artery (MCA) aneurysms. We describe our experience with bipolar aneurysm dome remodeling in the setting of bulbous MCA aneurysms. The charts of the senior author's (Aaron Cohen-Gadol) patients who underwent clip ligation of their MCA aneurysm (220 patients), and more specifically those whose aneurysm clipping was facilitated through bipolar coagulation remodeling (8 patients), were reviewed. Patient demographics, aneurysm characteristics, and postoperative angiographic results were analyzed. Eight patients with eight MCA aneurysms were treated through this technique over a six-year period. Their mean age was 53 years, and six of the eight patients were women. Two involved the anterior temporal artery, and the rest were at the M1 bifurcation or trifurcation. Three of the eight were ruptured; the mean aneurysm maximum diameter was 7 mm. Postoperative angiography demonstrated complete aneurysm obliteration in seven of eight patients; one patient had an asymptomatic mild stenosis of her anterior temporal artery's origin, and another had a small neck remnant in the setting of a highly atherosclerotic neck. On the basis of this experience, dome coagulation remodeling of small- and moderate-sized bulbous aneurysms in the setting of poor proximal and distal vessel visualization was found to be safe for facilitating aneurysm clipping and offers more desirable clip deployment.

Initial Experience Using Intraoperative Magnetic Resonance Imaging During a Trans-Sulcal Tubular Retractor Approach for the Resection of Deep-Seated Brain Tumors: A Case Series.

BACKGROUND: Treatment of deep-seated subcortical intrinsic brain tumors remains challenging and may be improved with trans-sulcal tubular brain retraction techniques coupled with intraoperative magnetic resonance imaging (iMRI). OBJECTIVE: To conduct a preliminary assessment of feasibility and efficacy of iMRI in tubular retractor-guided resections of intrinsic brain tumors. METHODS: Assessment of this technique and impact upon outcomes were assessed in a preliminary series of brain tumor patients from 2 centers. RESULTS: Ten patients underwent resection with a tubular retractor system and iMRI. Mean age was 53.2 ± 9.0 yr (range: 37-61 yr, 80% male). Lesions included 6 gliomas (3 glioblastomas, 1 recurrent anaplastic astrocytoma, and 2 low-grade gliomas) and 4 brain metastases (1 renal cell, 1 breast, 1 lung, and 1 melanoma). Mean maximal tumor diameter was 2.9 ± 0.95 cm (range 1.2-4.3 cm). The iMRI demonstrated subtotal resection (STR) in 6 of 10 cases (60%); additional resection was performed in 5 of 6 cases (83%), reducing STR rate to 2 of 10 cases (20%), with both having tumor encroaching on eloquent structures. Seven patients (70%) were stable or improved neurologically immediately postoperatively. Three patients (30%) had new postoperative neurological deficits, 2 of which were transient. Average hospital length of stay was 3.4 ± 2.0 d (range: 1-7 d). CONCLUSION: Combining iMRI with tubular brain retraction techniques is feasible and may improve the extent of resection of deep-seated intrinsic brain tumors that are incompletely visualized with the smaller surgical exposure of tubular retractors.

Efficacy of pre-operative stereotactic radiosurgery followed by surgical resection and correlative radiobiological analysis for patients with 1-4 brain metastases: study protocol for a phase II trial.

BACKGROUND: Stereotactic radiosurgery (SRS) has emerged as a common adjuvant modality used with surgery for resectable brain metastases (BMs). However, the optimal sequence of the multi-modality therapy has not been established. The goal of the study is to evaluate 6-month local control utilizing pre-operative SRS followed by surgical resection for patients with 1-4 brain metastases. METHODS: This prospective, single arm, phase II trial will recruit patients with up to 4 brain metastases and at least one resectable lesion. All lesions will be treated with SRS and symptomatic lesions will be resected within 1-4 days after SRS. Patients will be monitored for 6-month local control, in-brain progression free survival, distant in-brain failure, rate of leptomeningeal spread, radiation necrosis and overall survival. Additionally, we will also perform correlative radiobiological molecular studies to assess the effect of radiation dosing on the tumor tissue and clinical outcomes. We expect that pre-operative SRS to the gross tumor prior to surgical resection will improve local control and decrease leptomeningeal failure. DISCUSSION: Our study is the second prospective trial to investigate the efficacy of pre-operative SRS in the treatment of multiple BMs. In addition, the correlative molecular studies will be the first to investigate early response of BMs at a cellular and genetic level in response to radiation doses and potentially provide molecular prognostic markers for local control and overall survival. TRIAL REGISTRATION: Clinicaltrials.gov identifier: NCT03398694 (registration date: January 12, 2018).

Denosumab Treatment for a Residual Giant Cell Tumor of the Clivus: A Case Report and Review of the Literature.

BACKGROUND: Giant cell tumors (GCTs) are a locally aggressive primary bone neoplasm of osteoclast-like cells. These lesions largely occur in the epiphyses of long bones, but there have been rare reports of occurrence in the pelvis, spine, or skull. Of those located in the skull, involvement of the clivus has been rarely reported. CASE DESCRIPTION: We present a case of an 18-year-old woman presenting with a third nerve palsy, found to have a lytic lesion of the upper clivus that was primarily treated with endoscopic endonasal resection. Her third nerve palsy resolved postoperatively, and subsequent histopathologic analysis revealed a GCT. Six-month postoperative magnetic resonance imaging (MRI) revealed progression of residual disease for which she was treated with adjuvant denosumab. This treatment resulted in a significant decrease in the tumor size. She subsequently underwent proton beam radiation. At 1-year postsurgery, the patient's MRI remained stable after completing denosumab and proton therapy. She was neurologically intact and had no issues from her treatment. CONCLUSIONS: Denosumab has demonstrated anti-GCT efficacy. In combination with proton therapy, it has the potential to spare a young, vulnerable population from adverse long-term effects of traditional adjuvant radiation therapy. To our knowledge, this is the first report of the use of denosumab in the treatment of GCT of the clivus in the United States.

Intraoperative angiography via the popliteal artery: a useful technique for patients in the prone position.

OBJECTIVE Intraoperative angiography can be a valuable tool in the surgical management of vascular disorders in the CNS. This is typically accomplished via femoral artery puncture; however, this can be technically difficult in patients in the prone position. The authors describe the feasibility of intraoperative angiography via the popliteal artery in the prone patient. METHODS Three patients underwent intraoperative spinal angiography in the prone position via vascular access through the popliteal artery. Standard angiography techniques were used, along with ultrasound and a micropuncture needle for initial vascular access. Two patients underwent intraoperative angiography to confirm the obliteration of dural arteriovenous fistulas. The third patient required unexpected intraoperative angiography when a tumor was concerning for a vascular malformation in the cervical spine. RESULTS All 3 patients tolerated the procedure without complication. The popliteal artery was easily accessed without any adaptation to typical patient positioning for these prone-position cases. This proved particularly beneficial when angiography was not part of the preoperative plan. CONCLUSIONS Intraoperative angiography via the popliteal artery is feasible and well tolerated. It presents significant benefit when obtaining imaging studies in patients in a prone position, with the added benefit of easy access, familiar anatomy, and low concern for catheter thrombosis or kinking.

Neurosurgical Management of Self-Inflicted Cranial Crossbow Injury.

BACKGROUND: Although gun-related penetrating traumatic brain injuries make up the majority of cranial missile injuries, low-velocity penetrating injuries present significant clinical difficulties that cannot necessarily be identically managed. Bow hunting is an increasingly popular pastime, and a crossbow allows a unique mechanism to cause a self-inflicted cranial injury with a large, low-velocity projectile. Historically, arrow removal is described in an operating room setting, which provides limited knowledge of the location of vascular injury in the setting of postremoval hemorrhage, and may represent an inefficient use of operating room availability. CASE DESCRIPTION: Two patients presented after self-inflicted cranial crossbow injuries. Both were neurologically salvageable. Initial assessment with computed tomography angiography allowed triage into likely or unlikely vascular injury. Arrow removal was performed in a radiology setting rather than in the operating room to allow immediate postremoval imaging to localize hemorrhage. While an operating room was on standby, neither patient required neurosurgical operative intervention. Both patients made a good recovery with no further injury caused by arrow removal. CONCLUSIONS: We describe a novel approach to retained cranial arrow removal in a radiologic, rather than operative, setting and describe its relative benefits over traditional removal in the operating room.

Neuroprotective effect of dexmedetomidine in a murine model of traumatic brain injury.

No FDA approved pharmacological therapy is available that would reduce cell death following traumatic brain injury (TBI). Dexmedetomidine (Dex) is a highly selective agonist of alpha-2 adrenergic receptors and has demonstrated neuroprotective effects in hippocampal slice cultures undergoing direct impact. However, no one has tested whether Dex, in addition to its sedative action, has neuroprotective effects in an animal model of TBI. Thus, in the present study, we investigated the effects of Dex on an animal model of TBI. Mice received different doses of Dex (1, 10, or 100 µg/kg bodyweight, n = 10 each group) or saline as control at 1 hour and 12 hours following TBI. The mice treated with Dex lost less cortical tissue than the control mice. Further analysis found that Dex treatment reduced cell death in the cortex and the hippocampus measured by Fluoro-Jade B (FJB) staining, prevented axonal degeneration detected by immunostaining with antibody against ß-amyloid precursor protein (ß-APP), and protected synapses from elimination with synaptophysin staining. Taken together, in an in vivo murine model of TBI, Dex at the dose of 100 µg/kg not only prevented tissue lesion and cell death, but also reduced axonal injury and synaptic degeneration caused by TBI.

Pediatric Pontine Cavernous Malformations: The Presigmoid, Posterior Petrosal Approach.

BACKGROUND: Brainstem cavernous malformations (cavernomas) in children have a high risk of hemorrhage and neurological deterioration. This risk is magnified if the child has a genetic predisposition for cavernoma formation. The surgical management is challenging and carries a significant risk of morbidity. OBJECTIVE: To describe the feasibility of a posterior petrosal approach to brainstem cavernomas in a pediatric population. METHODS: A single institution operative experience with this technique was reviewed; 2 cases were identified and are technically described here with supportive figures and illustrations, as well as a focused literature review. RESULTS: Two pediatric cases with multiple symptomatic hemorrhages from large expanding pontine cavernomas were identified. Both cavernomas were resected through a presigmoid posterior petrosal approach. While this approach is well described in the adult literature for ventral brainstem lesions, its description for the treatment of pontine cavernomas in the pediatric populations is scarce. CONCLUSION: This study demonstrates the utility and feasibility of the posterior petrosal approach in two pediatric patients at different points in cranial base development.

Technology that achieves the Triple Aim: an economic analysis of the BrainPath™ approach in neurosurgery.

BACKGROUND: The Triple Aim is defined as: improving the patient experience of care, improving the health of populations, and reducing the per capita cost of health care. The purpose of this analysis was to evaluate the economic value of a new neurosurgical technique, the BrainPath™ approach, for use in patients with subcortical tumors and intracerebral hemorrhage (ICH). METHODS: Inpatient length of stay (LOS) data were collected for ICH and brain tumor surgical patient cases between August 2013 and November 2015. Patient cases were separated into two groups; BrainPath approach (n = 28) and conventional techniques, such as craniotomy, (n = 208). The average intensive care unit (ICU) LOS was calculated for each group by diagnosis-related group and compared between groups. RESULTS: The new surgical technology resulted in surgical intervention in 14 ICH cases which otherwise would have been medically managed due to the hemorrhage location or size of the ICH. A reduction in ICU LOS was seen in this group. Based on the variable direct cost per day in the neuro critical care unit at this academic medical center, 14 patient cases incurred ~ US$210,000 less in direct ICU costs. Surgical resection was possible in two tumor patient cases which would have been biopsied, rather than surgically resected, also due to location of the abnormalities. A total net value of > US$329,000 is attributable to the analyzed approach over a 28-month period. CONCLUSION: This analysis shows positive economic value for the new technology group when ICU LOS and reimbursement are considered against equipment costs, thus achieving Triple Aim objectives.

Effect of short-term ε-aminocaproic acid treatment on patients undergoing endovascular coil embolization following aneurysmal subarachnoid hemorrhage.

OBJECTIVE Aneurysmal rebleeding before definitive obliteration of the aneurysm is a cause of mortality and morbidity. There are limited data on the role of short-term antifibrinolytic therapy among patients undergoing endovascular intervention. METHODS All consecutive patients receiving endovascular therapy for their ruptured saccular aneurysm at the authors' institution between 2000 and 2011 were included in this study. These patients underwent endovascular coiling of their aneurysm within 72 hours of admission. In patients receiving ε-aminocaproic acid (EACA), the EACA administration was continued until the time of the endovascular procedure. Complications and clinical outcomes of endovascular treatment after aneurysmal subarachnoid hemorrhage (aSAH) were compared between EACA-treated and untreated patients. RESULTS During the 12-year study period, 341 patients underwent endovascular coiling. Short-term EACA treatment was administered in 146 patients and was withheld in the other 195 patients. EACA treatment did not change the risk of preinterventional rebleeding in this study (OR 0.782, 95% CI 0.176-3.480; p = 0.747). Moreover, EACA treatment did not increase the rate of thromboembolic events. On the other hand, patients who received EACA treatment had a significantly longer duration of hospital stay compared with their counterparts who were not treated with EACA (median 19 days, interquartile range [IQR] 12.5-30 days vs median 14 days, IQR 10-23 days; p < 0.001). EACA treatment was associated with increased odds of shunt requirement (OR 2.047, 95% CI 1.043-4.018; p = 0.037) and decreased odds of developing cardiac complications (OR 0.138, 95% CI 0.031-0.604; p = 0.009) and respiratory insufficiency (OR 0.471, 95% CI 0.239-0.926; p = 0.029). Short-term EACA treatment did not affect the Glasgow Outcome Scale score at discharge, 6 months, or 1 year following discharge. CONCLUSIONS In this study, short-term EACA treatment in patients who suffered from aSAH and received endovascular aneurysm repair did not decrease the risk of preinterventional rebleeding or increase the risk of thrombotic events. EACA did not affect outcome. Randomized clinical trials are required to provide robust clinical recommendation on short-term use of EACA.

The Safety and Feasibility of Image-Guided BrainPath-Mediated Transsulcul Hematoma Evacuation: A Multicenter Study.

BACKGROUND: Subcortical injury resulting from conventional surgical management of intracranial hemorrhage may counteract the potential benefits of hematoma evacuation. OBJECTIVE: To evaluate the safety and potential benefits of a novel, minimally invasive approach for clot evacuation in a multicenter study. METHODS: The integrated approach incorporates 5 competencies: (1) image interpretation and trajectory planning, (2) dynamic navigation, (3) atraumatic access system (BrainPath, NICO Corp, Indianapolis, Indiana), (4) extracorporeal optics, and (5) automated atraumatic resection. Twelve neurosurgeons from 11 centers were trained to use this approach through a continuing medical education-accredited course. Demographical, clinical, and radiological data of patients treated over 2 years were analyzed retrospectively. RESULTS: Thirty-nine consecutive patients were identified. The median Glasgow Coma Scale (GCS) score at presentation was 10 (range, 5-15). The thalamus/basal ganglion regions were involved in 46% of the cases. The median hematoma volume and depth were 36 mL (interquartile range [IQR], 27-65 mL) and 1.4 cm (IQR, 0.3-2.9 cm), respectively. The median time from ictus to surgery was 24.5 hours (IQR, 16-66 hours). The degree of hematoma evacuation was ≥90%, 75% to 89%, and 50% to 74% in 72%, 23%, and 5.0% of the patients, respectively. The median GCS score at discharge was 14 (range, 8-15). The improvement in GCS score was statistically significant ( P < .001). Modified Rankin Scale data were available for 35 patients. Fifty-two percent of those patients had a modified Rankin Scale score of ≤2. There were no mortalities. CONCLUSION: The approach was safely performed in all patients with a relatively high rate of clot evacuation and functional independence.

Modified skin incision for avoiding the lesser occipital nerve and occipital artery during retrosigmoid craniotomy: potential applications for enhancing operative working distance and angles while minimizing the risk of postoperative neuralgias and intraoperative hemorrhage.

Chronic postoperative neuralgias and headache following retrosigmoid craniotomy can be uncomfortable for the patient. We aimed to better elucidate the regional nerve anatomy in an effort to minimize this postoperative complication. Ten adult cadaveric heads (20 sides) were dissected to observe the relationship between the lesser occipital nerve and a traditional linear versus modified U incision during retrosigmoid craniotomy. Additionally, the relationship between these incisions and the occipital artery were observed. The lesser occipital nerve was found to have two types of course. Type I nerves (60%) remained close to the posterior border of the sternocleidomastoid muscle and some crossed anteriorly over the sternocleidomastoid muscle near the mastoid process. Type II nerves (40%) left the posterior border of the sternocleidomastoid muscle and swung medially (up to 4.5cm posterior to the posterior border of the sternocleidomastoid muscle) as they ascended over the occiput. The lesser occipital nerve was near a midpoint of a line between the external occipital protuberance and mastoid process in all specimens with the type II nerve configuration. Based on our findings, the inverted U incision would be less likely to injure the type II nerves but would necessarily cross over type I nerves, especially more cranially on the nerve at the apex of the incision. As the more traditional linear incision would most likely transect the type I nerves and more so near their trunk, the U incision may be the overall better choice in avoiding neural and occipital artery injury during retrosigmoid approaches.