Considerations for the use of porcine organ donation models in preclinical organ donor intervention research.

Use of animal models in preclinical transplant research is essential to the optimization of human allografts for clinical transplantation. Animal models of organ donation and preservation help to advance and improve technical elements of solid organ recovery and facilitate research of ischemia-reperfusion injury, organ preservation strategies, and future donor-based interventions. Important considerations include cost, public opinion regarding the conduct of animal research, translational value, and relevance of the animal model for clinical practice. We present an overview of two porcine models of organ donation: donation following brain death (DBD) and donation following circulatory death (DCD). The cardiovascular anatomy and physiology of pigs closely resembles those of humans, making this species the most appropriate for pre-clinical research. Pigs are also considered a potential source of organs for human heart and kidney xenotransplantation. It is imperative to minimize animal loss during procedures that are surgically complex. We present our experience with these models and describe in detail the use cases, procedural approach, challenges, alternatives, and limitations of each model.

Aneurysmal Subdural Hematoma: A Systematic Review.

BACKGROUND: Aneurysmal subdural hematoma (aSDH) is a rare complication of aneurysm rupture, affecting between 0.5 and 7.9% of patients with aneurysmal subarachnoid hemorrhage (aSAH). The clinical presentation, course, and outcomes of these patients are largely unknown. OBJECTIVE: This study aims to systematically review the literature to evaluate the demographics, clinical presentation, aneurysm location, treatment options, and outcomes of patients with aSDH with and without aSAH. METHODS: In accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines, we conducted a systematic review of three databases (PubMed, EMBASE, and Google Scholar). From identified reports, we extracted data on patients' demographics, clinical presentation, imaging findings, surgical interventions, and clinical outcomes. We compared clinical outcomes, need for surgical treatment, and aneurysm location between patients with aSDH with and without concurrent aSAH using χ2 and Fisher's exact tests. We used simple and multivariable logistic regression models to further examine the association between the presence of aSAH and surgical treatment with clinical outcomes. RESULTS: We identified 112 articles with a total of 270 patients (70% women, mean age 52.8 [± 15.5] years). The most common aneurysm locations were the middle cerebral artery, followed by the posterior communicating artery, and the internal carotid artery. Patients with isolated aSDH fully recovered more frequently than those with concomitant aSAH (38% vs. 6%). The presence of aSAH increased the odds of unfavorable outcome (odds ratio [OR] 2.68, 95% confidence interval [CI] 1.34-5.37). Surgical treatment was inversely associated with unfavorable outcome in the univariable (OR 0.48, 95% CI 0.28-0.84) but not in the multivariable analysis (OR 0.76, 95% CI 0.35-1.66). CONCLUSION: aSDH occurs infrequently. Simultaneous presence of both aSDH and aSAH from an aneurysmal source is associated with poor outcomes. Surgical treatment is associated with lower rates of unfavorable outcomes including death and severe disability.

The complete anterior petrosectomy: an expanded extended-middle fossa approach with removal of the infratrigeminal petrous apex and drilling of the lateral clivus.

Intradural exposure in the extended middle fossa anterior transpetrosal approach is traditionally limited to the inferior petrosal sinus inferomedially. Expanding bone removal of the petrous apex around the petrous internal carotid artery (ICA), underneath the trigeminal ganglion/mandibular nerve, and into the lateral component of the clivus can significantly expand the limits of this approach beyond the inferior petrosal sinus and allows for exposure of the midline structures, aspects of the contralateral inferior clival region, and, when high riding, the vertebrobasilar junction. To date, no descriptive techniques for drilling into the lateral clivus in this approach have been published. The authors provide a detailed stepwise description of their complete anterior petrosectomy, in use at their institution, that involves skeletonization of the posteromedial petrous ICA, gentle elevation of the trigeminal ganglion/mandibular nerve, removal of the infratrigeminal petrous apex, and two techniques for drilling into the lateral clivus along the petroclival fissure. These techniques provide a direct and unobstructed corridor to the midpetroclival region and ventral brainstem with greater maneuverability and enhanced control of the midline structures, which is especially useful for resection of petroclival meningiomas, chondrosarcomas, and giant vascular lesions of the mid- and upper basilar artery and its proximal branches.

Effects of Acute Intracranial Pressure Changes on Optic Nerve Head Morphology in Humans and Pig Model.

PURPOSE: The lamina cribrosa (LC) is a layer of fenestrated connective tissue tethered to the posterior sclera across the scleral canal in the optic nerve head (ONH). It is located at the interface of intracranial and intraocular compartments and is exposed to intraocular pressure (IOP) anteriorly and intracranial pressure (ICP) or Cerebrospinal fluid (CSF) pressure (CSFP) posteriorly. We hypothesize that the pressure difference across LC will determine LC position and meridional diameter of scleral canal (also called Bruch's membrane opening diameter; BMOD). METHODS: We enrolled 19 human subjects undergoing a medically necessary lumbar puncture (LP) to lower CSFP and 6 anesthetized pigs, whose ICP was increased in 5 mm Hg increments using a lumbar catheter. We imaged ONH using optical coherence tomography and measured IOP and CSFP/ICP at baseline and after each intervention. Radial tomographic ONH scans were analyzed by two independent graders using ImageJ, an open-source software. The following ONH morphological parameters were obtained: BMOD, anterior LC depth and retinal thickness. We modeled effects of acute CSFP/ICP changes on ONH morphological parameters using ANOVA (human study) and generalized linear model (pig study). RESULTS: For 19 human subjects, CSFP ranged from 5 to 42 mm Hg before LP and 2 to 19.4 mm Hg after LP. For the six pigs, baseline ICP ranged from 1.5 to 9 mm Hg and maximum stable ICP ranged from 18 to 40 mm Hg. Our models showed that acute CSFP/ICP changes had no significant effect on ONH morphological parameters in both humans and pigs. CONCLUSION: We conclude that ONH does not show measurable morphological changes in response to acute changes of CSFP/ICP. Proposed mechanisms include compensatory and opposing changes in IOP and CSFP/ICP and nonlinear or nonmonotonic effects of IOP and CSFP/ICP across LC.

Correlation Between Neurosurgical Residency Written Board Scores and Case Logs.

OBJECTIVE: There are few objective measures for evaluating individual performance throughout surgical residency. Two commonly used objective measures are the case log numbers and written board examination scores. The objective of this study was to investigate possible correlations between these measures. METHODS: We conducted a retrospective review of the American Board of Neurological Surgery (ABNS) written board scores and the Accreditation Council for Graduate Medical Education case logs of 27 recent alumni from neurologic surgery residency training programs at The Ohio State Wexner Medical Center and the University of Nebraska Medical Center. RESULTS: The number of spine cases logged was significantly correlated with the ABNS written examination performance in univariate linear regression (r2 = 0.182, P = 0.0265). However, case numbers from all other neurosurgical subspecialties did not significantly correlate with ABNS written board performance (P > 0.1). CONCLUSIONS: Identifying which objective measures correlate most closely with resident education could help optimize the structure of residency training programs. We believe that early exposure to focused aspects of neurosurgery helps the young resident learn quickly and efficiently and ultimately score highly on standardized examinations. Therefore program directors may want to ensure focused exposure during the early years of residency, with particular attention to worthwhile rotations in spine neurosurgery.

The Effects of Acute Intracranial Pressure Changes on the Episcleral Venous Pressure, Retinal Vein Diameter and Intraocular Pressure in a Pig Model.

PURPOSE: Orbital veins such as the retinal veins and episcleral veins drain into the cavernous sinus, an intracranial venous structure. We studied the effects of acute intracranial pressure (ICP) elevation on episcleral venous pressure, intraocular pressure and retinal vein diameter in an established non-survival pig model. METHODS: In six adult female domestic pigs, we increased ICP in 5 mm Hg increments using saline infusion through a lumbar drain. We measured ICP (using parenchymal pressure monitor), intraocular pressure (using pneumatonometer), episcleral venous pressure (using venomanometer), retinal vein diameter (using OCT images) and arterial blood pressure at each stable ICP increment. The average baseline ICP was 5.4 mm Hg (range 1.5-9 mm Hg) and the maximum stable ICP ranged from 18 to 40 mm Hg. Linear mixed models with random intercepts were used to evaluate the effect of acute ICP increase on outcome variables. RESULTS: With acute ICP elevation, we found loss of retinal venous pulsation and increased episcleral venous pressure, intraocular pressure and retinal vein pressure in all animals. Specifically, acute ICP increase was significantly associated with episcleral venous pressure (ß = 0.31; 95% CI 0.14-0.48, p < .001), intraocular pressure (ß = 0.37, 95%CI 0.24-0.50; p < .001) and retinal vein diameter (ß = 11.29, 95%CI 1.57-21.00; p = .03) after controlling for the effects of arterial blood pressure. CONCLUSION: We believe that the ophthalmic effects of acute ICP elevation are mediated by increased intracranial venous pressure producing upstream pressure changes within the orbital and retinal veins. These results offer exciting possibilities for the development of non-invasive ophthalmic biomarkers to estimate acute ICP elevations following significant neuro-trauma.

Spontaneous Spinal Epidural Hematoma Associated With Apixaban Therapy: A Report of two Cases.

Spontaneous spinal epidural hematoma (SSEH) is a rare clinical entity that can result in severe neurological deficit and warrants emergent neurosurgical evaluation and management. The exact etiology of this entity remains unknown, but certain risk factors exist, including the use of anticoagulant medications. There are few published reports of the association of SSEH with direct factor Xa inhibitors. We aimed to present 2 cases of SSEH in patients on chronic apixaban therapy. To the best of our knowledge, there is only 1 other report of SSEH in the setting of apixaban therapy. A comparison between the cases suggests the importance of rapid recognition and management of SSEH in order to achieve favorable neurological outcomes.

Association of Preoperative Patient Frailty and Operative Stress With Postoperative Mortality.

Importance: Patients with frailty have higher risk for postoperative mortality and complications; however, most research has focused on small groups of high-risk procedures. The associations among frailty, operative stress, and mortality are poorly understood. Objective: To assess the association between frailty and mortality at varying levels of operative stress as measured by the Operative Stress Score, a novel measure created for this study. Design, Setting, and Participants: This retrospective cohort study included veterans in the Veterans Administration Surgical Quality Improvement Program from April 1, 2010, through March 31, 2014, who underwent a noncardiac surgical procedure at Veterans Health Administration Hospitals and had information available on vital status (whether the patient was alive or deceased) at 1 year postoperatively. A Delphi consensus method was used to stratify surgical procedures into 5 categories of physiologic stress. Exposures: Frailty as measured by the Risk Analysis Index and operative stress as measured by the Operative Stress Score. Main Outcomes and Measures: Postoperative mortality at 30, 90, and 180 days. Results: Of 432 828 unique patients (401 453 males [92.8%]; mean (SD) age, 61.0 [12.9] years), 36 579 (8.5%) were frail and 9113 (2.1%) were very frail. The 30-day mortality rate among patients who were frail and underwent the lowest-stress surgical procedures (eg, cystoscopy) was 1.55% (95% CI, 1.20%-1.97%) and among patients with frailty who underwent the moderate-stress surgical procedures (eg, laparoscopic cholecystectomy) was 5.13% (95% CI, 4.79%-5.48%); these rates exceeded the 1% mortality rate often used to define high-risk surgery. Among patients who were very frail, 30-day mortality rates were higher after the lowest-stress surgical procedures (10.34%; 95% CI, 7.73%-13.48%) and after the moderate-stress surgical procedures (18.74%; 95% CI, 17.72%-19.80%). For patients who were frail and very frail, mortality continued to increase at 90 and 180 days, reaching 43.00% (95% CI, 41.69%-44.32%) for very frail patients at 180 days after moderate-stress surgical procedures. Conclusions and Relevance: We developed a novel operative stress score to quantify physiologic stress for surgical procedures. Patients who were frail and very frail had high rates of postoperative mortality across all levels of the Operative Stress Score. These findings suggest that frailty screening should be applied universally because low- and moderate-stress procedures may be high risk among patients who are frail.

Highly Aggressive and Radiation-Resistant, "Atypical" and Silent Pituitary Corticotrophic Carcinoma: A Case Report and Review of the Literature.

BACKGROUND: Pituitary tumors typically remain silent unless interaction with nearby structures occurs. Rare subsets of pituitary tumors display aggressive phenotypes: highly mitotic, locally invasive, metastatic, chemotherapy and radiation resistant, etc. Disease progression and response to therapy is ill-defined in these subtypes, and their true prognostic potential is debated. Thus, identifying tumor characteristics with prognostic value and efficacious treatment options remains a challenge in aggressive pituitary tumors. CASE PRESENTATION: A 45-year-old female presented with a nonfunctioning corticotropic pituitary macroadenoma with biomarkers suggestive of an "atypical" subtype: Ki-67 of 8-12%, increased mitosis, and locally invasive. Despite resections and radiation, growth continued, eventually affecting her vision. Although histologically ACTH positive, the patient remained clinically asymptomatic. Twelve months later, an episode of Cushing's disease-induced psychosis prompted a PET-CT scan, identifying sites of metastasis. Temozolomide was added to her medical regimen, and her metastatic liver lesions and boney metastases were treated with radiofrequency ablation and stereotactic body radiation therapy, respectively. Systemic treatment resulted in a drop in her ACTH levels, with her most recent scans/labs at 12 months following RFA suggesting remission. CONCLUSIONS: This is a unique presentation of a pituitary tumor, displaying characteristics of both clinically silent corticotropic and "atypical" macroadenoma subtypes. Although initially ACTH positive while clinically silent, the patient's disease ultimately recurred metastatically with manifestations of Cushing's disease and psychosis. With the addition of temozolomide to her treatment plan, her primary and metastatic sites have responded favorably to radiation therapy. Thus, the addition of temozolomide may be beneficial in the treatment of aggressive pituitary tumors.

Pilot project to assess and improve neurosurgery resident and staff perception of feedback to residents for self-improvement goal formation.

OBJECTIVE: The Accreditation Council for Graduate Medical Education (ACGME) has pushed for more frequent and comprehensive feedback for residents during their training, but there is scant evidence for how neurosurgery residents view the current feedback system as it applies to providing information for self-improvement and goal formation. The authors sought to assess neurosurgery resident and staff perceptions of the current resident feedback system in providing specific, meaningful, achievable, realistic, and timely (SMART) goals. The authors then created a pilot project to improve the most unfavorably viewed aspect of the feedback system. METHODS: The authors conducted an anonymous survey of neurosurgery residents and staff at an academic medical institution to assess SMART goals for resident feedback and used the results to create a pilot intervention to address the most unfavorably viewed aspect of the feedback system. The authors then conducted a postintervention survey to see if perceptions had improved for the target of the intervention. RESULTS: Neurosurgery residents and staff completed an anonymous online survey, for which the results indicated that resident feedback was not occurring in a timely manner. The authors created a simple anonymous feedback form. The form was distributed monthly to neurosurgery residents, neurosurgical staff, and nurses, and the results were reported monthly to each resident for 6 months. A postintervention survey was then administered, and the results indicated that the opinions of the neurosurgery residents and staff on the timeliness of resident feedback had changed from a negative to a nonnegative opinion (p = 0.01). CONCLUSIONS: The required ACGME feedback methods may not be providing adequate feedback for goal formation for self-improvement for neurosurgery residents. Simple interventions, such as anonymous feedback questionnaires, can improve neurosurgery resident and staff perception of feedback to residents for self-improvement and goal formation.

Suction forces generated by passive bile bag drainage on a model of post-subdural hematoma evacuation.

BACKGROUND: Passive drainage systems are commonly used after subdural hematoma evacuation but there is a dearth of published data regarding the suction forces created. We set out to quantify the suction forces generated by a passive drainage system. METHOD: We created a model of passive drainage after subdural hematoma evacuation. We measured the maximum suction force generated with a bile bag drain for both empty drain tubing and fluid-filled drain tube causing a siphoning effect. We took measurements at varying heights of the bile bag to analyze if bile bag height changed suction forces generated. RESULTS: An empty bile bag with no fluid in the drainage tube connected to a rigid, fluid-filled model creates minimal suction force of 0.9 mmHg (95% CI 0.64-1.16 mmHg). When fluid fills the drain tubing, a siphoning effect is created and can generate suction forces ranging from 18.7 to 30.6 mmHg depending on the relative position of the bile bag and filled amount of the bile bag. The suction forces generated are statistically different if the bile bag is 50 cm below, level with or 50 cm above the experimental model. CONCLUSION: Passive bile bag drainage does not generate significant suction on a fluid-filled rigid model if the drain tubing is empty. If fluid fills the drain tubing then siphoning occurs and can increase the suction force of a passive bile bag drainage system to levels comparable to partially filled Jackson-Pratt bulb drainage.

Hemorrhage Rate After External Ventricular Drain Placement in Subarachnoid Hemorrhage: Time to Heparin Administration.

OBJECTIVE: The use of antiplatelet or anticoagulants has previously been shown to increase hemorrhagic complications of ventricular catheterization. Although heparin use 24 h after ventriculostomy appears safe, the safety of heparin immediately (within 4 h) after ventriculostomy is unknown. The objective of this study was to assess the safety of heparin immediately (within 4 h) after ventriculostomy in subarachnoid hemorrhage (SAH) patients undergoing endovascular treatment. PATIENTS AND METHODS: This is a retrospective cohort study of 46 patients with aneurysmal SAH secondary to aneurysm rupture who required ventriculostomy. Post-ventriculostomy imaging was carefully reviewed for tract hemorrhaging. Timing of heparinization was noted. Early heparinization was within 4 h after ventriculostomy, and intermediate heparinization was between 4 and 24 h after ventriculostomy. RESULTS: Overall, the tract hemorrhage rate was 26.1% for the study cohort-mostly grade I tract hemorrhages-consistent with the existing literature. The tract hemorrhage rate in the early (<4 h) heparin group was a remarkable 58.8%. The hemorrhages were also notably larger in the early (<4 h) heparin group. CONCLUSION: Although heparin appears to be safe after 4 h, immediate heparinization (within 4 h) after ventriculostomy significantly increases the odds of tract hemorrhage. Additional time should be afforded between ventriculostomy and heparinization to avoid potentially devastating external ventricular drain tract hemorrhage. It is advisable to wait a sufficient time (at least 4 h) after ventriculostomy before embarking on endovascular treatment of ruptured aneurysms.

Measuring Hemodynamic Changes in the Ophthalmic Artery During Applied Force for Noninvasive Intracranial Pressure Monitoring: Test Results in a Porcine Model.

Possible traumatic brain injury victims would greatly benefit from a handheld, noninvasive intracranial pressure (ICP) monitoring tool, which a medic could operate in a remote area. Such a device would also benefit the transport of injured soldiers during en route medical care and critical care air transport. This study demonstrates the use of noninvasive blood flow measurements in the eye by ultrasound as a proxy for ICP. ICP was artificially raised in a porcine model and resultant blood flow change in the ophthalmic artery was measured. In addition, the ultrasound transducer itself was used to compress the eye further altering ophthalmic hemodynamics. Blood flow velocities at a range of applied forces and ICP were compared. It was found that 3.25 N of force applied to the cornea was sufficient to produce significant changes in ophthalmic artery blood dynamics regardless of the ICP value. Specifically, the change in resistivity index (RI) and pulsatility index (PI) as force was applied to the cornea correlated with ICP levels. In multiple animal experiments, the magnitude of PI/RI percent change was inversely related to differences in ICP. Force applied to the cornea at baseline ICP resulted in a 15% increase in PI/RI. Results indicate that as ICP increases, the percent change in PI/RI while force is applied decreases. The consistency of data collected indicates that a trend line developed with this data and from similar experiments could be used as a predictive measurement of ICP.

Occipital Bony Abnormality and Multiple Strokes in a Pediatric Patient: Case Report and Review of the Current Literature.

This study presents a case of a 15-year-old boy who had a right vertebral artery dissection with distal embolization from repeated trauma from an occipital bony spicule. The authors hypothesize that this bony spicule was contacting the left vertebral artery during head rotation, resulting in trauma to the vessel and formation of emboli which then showered distally, causing strokes in the posterior circulation of the brain. This specific phenomenon has previously been reported three times, only one of which was in pediatric literature. It is important for individuals to be aware of this rare anatomic cause of vertebral artery dissection in patients presenting with an odd constellation of symptoms related to strokes from vertebro-basilar system. Treatment options including early intervention with intravascular coil embolization are also discussed.

Implications of carotid sinus hypersensitivity following preoperative embolization of a carotid body tumor. An indication for prophylactic intraoperative cardiac pacing.

IMPORTANCE Carotid body tumors are rare neoplasms of neural crest origin that are both highly vascularized and locally invasive. Treatment options for these tumors often include surgery with preoperative embolization, which can pose major cardiovascular risk to patients. As demonstrated by this case report, hemodynamic instability following preoperative embolization of a carotid body tumor may indicate severe carotid sinus hypersensitivity and the need for temporary cardiac pacing. OBSERVATIONS This case report describes a man in his early 30s who presented for staged surgical resection of bilateral carotid body tumors with preoperative embolization. After embolization of the second tumor, the patient displayed transient episodes of bradycardia and hypotension, which resolved with medical management. Surgery commenced, and with minimal manipulation intraoperatively, the patient became asystolic and required resuscitation. Following a negative cardiac workup, a temporary pacemaker was implanted, and surgical resection of the tumor was successfully completed. CONCLUSIONS AND RELEVANCE Carotid sinus hypersensitivity is a rare but serious risk of preoperative embolization of carotid body tumors. Postembolization bradycardia or hypotension should be assessed as potential harbingers of carotid sinus hypersensitivity, and the need for temporary intraoperative cardiac pacing should be strongly considered.

Remote cerebellar hemorrhage following supratentorial cerebrovascular surgery.

Three patients with remote cerebellar hemorrhage following supratentorial cerebrovascular surgery are presented. Remote cerebellar hemorrhage is a rare surgical complication that is most often associated with aneurysm clipping or temporal lobectomies. Bleeding occurs on the superior cerebellar cortex and is believed to be venous in origin. The precise pathogenesis of remote cerebellar hemorrhage has yet to be fully elucidated but is generally considered to be a consequence of intraoperative cerebrospinal fluid loss causing caudal displacement of the cerebellum with resultant stretching of the supracerebellar veins. This case series will hopefully shed further light on the incidence, presentation, workup, and treatment of this particular complication of supratentorial surgery.

Diffuse anaplastic leptomeningeal oligodendrogliomatosis mimicking neurosarcoidosis.

Diffuse leptomeningeal oligodendrogliomatosis is a rare, frequently fatal CNS malignancy that most often affects children.1 Although potentially treatable with chemotherapy and radiation, the radiologic findings are nonspecific and pathologic confirmation of the diagnosis is difficult. We describe an adult patient whose initial presentation mimicked neurosarcoidosis. Despite extensive imaging abnormalities, 3 biopsies were required before the diagnosis of diffuse leptomeningeal oligodendrogliomatosis was confirmed.

Compartmentalization of immune responses during Staphylococcus aureus cranial bone flap infection.

Decompressive craniectomy is often required after head trauma, stroke, or cranial bleeding to control subsequent brain swelling and prevent death. The infection rate after cranial bone flap replacement ranges from 0.8% to 15%, with an alarming frequency caused by methicillin-resistant Staphylococcus aureus, which is problematic because of recalcitrance to antibiotic therapy. Herein we report the establishment of a novel mouse model of S. aureus cranial bone flap infection that mimics several aspects of human disease. Bacteria colonized bone flaps for up to 4 months after infection, as revealed by scanning electron microscopy and quantitative culture, demonstrating the chronicity of the model. Analysis of a human cranial bone flap with confirmed S. aureus infection by scanning electron microscopy revealed similar structural attributes as the mouse model, demonstrating that it closely parallels structural facets of human disease. Inflammatory indices were most pronounced within the subcutaneous galeal compartment compared with the underlying brain parenchyma. Specifically, neutrophil influx and chemokine expression (CXCL2 and CCL5) were markedly elevated in the galea, which demonstrated substantial edema on magnetic resonance images, whereas the underlying brain parenchyma exhibited minimal involvement. Evaluation of immune mechanisms required for bacterial containment and inflammation revealed critical roles for MyD88-dependent signaling and neutrophils. This novel mouse model of cranial bone flap infection can be used to identify key immunologic and therapeutic mechanisms relevant to persistent bone flap infection in humans.

Angiogram-negative subarachnoid hemorrhage: outcomes data and review of the literature.

Spontaneous subarachnoid hemorrhage (SAH) is most commonly caused by rupture of a saccular aneurysm or other structural pathologies. Occasionally, no structural cause for the hemorrhage can be identified by radiographic imaging. These hemorrhages, termed angiogram-negative SAH, are generally considered to have a better prognosis than aneurysmal SAH. Angiogram-negative SAH subgroups include benign perimesencephalic SAH (PMH) and aneurysmal-type SAH. Outcome data for these subgroups differ from those for the group as a whole. We report data for 31 patients who presented to our institution from 2006 to the present. We performed a retrospective chart review, and report outcome data that include rates of rehemorrhage, hydrocephalus, vasospasm, permanent ischemic deficits, headaches, and outcomes based on modified Rankin Scale scores. We also performed a review of the literature and meta-analysis of the data therein. We compared rates of complications in the PMH subgroup and the diffuse-type hemorrhage subgroup. The chart review revealed no poor outcomes and no rehemorrhages in the patients with PMH. In the diffuse hemorrhage subgroup, 1 patient had a rehemorrhage and 2 patients had a poor outcome. Our literature review found an OR of 6.23 for a good outcome for PMH versus diffuse-type hemorrhage, and an OR of 2.78 for rehemorrhage in PMH versus diffuse-type hemorrhage. Angiogram-negative SAH is not a benign entity. Complications are present but are significantly reduced, and outcomes are improved, compared with aneurysmal SAH.