Dr. Ayer completed his undergraduate education at Queen’s University with a degree in life sciences and an honors thesis in immunology. He then completed his medical training at Wake Forest University and his neurosurgical training at Northwestern University Feinberg School of Medicine, where during residency he also obtained a Master of Business Administration from Kellogg School of Management.

As a clinical instructor at Stanford, Dr. Ayer will be focused on the surgical treatments of movement disorders, epilepsy and pain. Dr. Ayer has clinical interests in surgical treatment for epilepsy, movement disorders, skull base approaches, hydrocephalus and spine surgery. His research has focused on bioelectronic tools for the treatment of neurosurgical pathology and is interested in developing novel brain computer interfaces and biosensors for the restoration of sensorimotor function.

In his free time, he enjoys playing guitar, hockey, hiking, and traveling.​

Academic Appointments

Boards, Advisory Committees, Professional Organizations

  • Member, Congress of Neurological Surgeons (2013 - Present)
  • Member, American Association of Neurological Surgeons (2013 - Present)

Professional Education

  • BSc, Queen's University, Life Sciences, Immunology (2009)
  • MBA, Northwestern Kellogg School of Management, Health care administration, entrepreneurship (2019)

All Publications

  • Analysis of risk factors and clinical sequelae of direct electrical cortical stimulation-induced seizures and afterdischarges in patients undergoing awake mapping. Journal of neurosurgery Abecassis, Z. A., Ayer, A. B., Templer, J. W., Yerneni, K., Murthy, N. K., Tate, M. C. 2020: 1–8


    OBJECTIVE: Intraoperative stimulation has emerged as a crucial adjunct in neurosurgical oncology, aiding maximal tumor resection while preserving sensorimotor and language function. Despite increasing use in clinical practice of this stimulation, there are limited data on both intraoperative seizure (IS) frequency and the presence of afterdischarges (ADs) in patients undergoing such procedures. The objective of this study was to determine risk factors for IS or ADs, and to determine the clinical consequences of these intraoperative events.METHODS: A retrospective chart review was performed for patients undergoing awake craniotomy (both first time and repeat) at a single institution from 2013 to 2018. Hypothesized risk factors for ADs/ISs in patients were evaluated for their effect on ADs and ISs, including tumor location, tumor grade (I-IV), genetic markers (isocitrate dehydrogenase 1/2, O6-methylguanine-DNA methyltransferase [MGMT] promoter methylation, chromosome 1p/19q codeletion), tumor volume, preoperative seizure status (yes/no), and dosage of preoperative antiepileptic drugs for each patient. Clinical outcomes assessed in patients with IS or ADs were duration of surgery, length of stay, presence of perioperative deficits, and postoperative seizures. Chi-square analysis was performed for binary categorical variables, and a Student t-test was used to assess continuous variables.RESULTS: A total of 229 consecutive patients were included in the analysis. Thirty-five patients (15%) experienced ISs. Thirteen (37%) of these 35 patients had experienced seizures that were appreciated clinically and noted on electrocorticography simultaneously, while 8 patients (23%) experienced ISs that were electrographic alone (no obvious clinical change). MGMT promoter methylation was associated with an increased prevalence of ISs (OR 3.3, 95% CI 1.2-7.8, p = 0.02). Forty patients (18%) experienced ADs. Twenty-three percent of patients (9/40) with ISs had ADs prior to their seizure, although ISs and ADs were not statistically associated (p = 0.16). The presence of ADs appeared to be correlated with a shorter length of stay (5.1 ± 2.6 vs 6.1 ± 3.7 days, p = 0.037). Of the clinical features assessed, none were found to be predictive of ADs. Neither IS nor AD, or the presence of either IS or AD (65/229 patients), was a predictor for increased length of stay, presence of perioperative deficits, or postoperative seizures.CONCLUSIONS: ISs and ADs, while commonly observed during intraoperative stimulation for brain mapping, do not negatively affect patient outcomes.

    View details for DOI 10.3171/2020.3.JNS193231

    View details for PubMedID 32442979

  • Continuous, noninvasive wireless monitoring of flow of cerebrospinal fluid through shunts in patients with hydrocephalus NPJ DIGITAL MEDICINE Krishnan, S. R., Arafa, H. M., Kwon, K., Deng, Y., Su, C., Reeder, J. T., Freudman, J., Stankiewicz, I., Chen, H., Loza, R., Mims, M., Mims, M., Lee, K., Abecassis, Z., Banks, A., Ostojich, D., Patel, M., Wang, H., Borekci, K., Rosenow, J., Tate, M., Huang, Y., Alden, T., Potts, M. B., Ayer, A. B., Rogers, J. A. 2020; 3 (1): 29


    Hydrocephalus is a common disorder caused by the buildup of cerebrospinal fluid (CSF) in the brain. Treatment typically involves the surgical implantation of a pressure-regulated silicone tube assembly, known as a shunt. Unfortunately, shunts have extremely high failure rates and diagnosing shunt malfunction is challenging due to a combination of vague symptoms and a lack of a convenient means to monitor flow. Here, we introduce a wireless, wearable device that enables precise measurements of CSF flow, continuously or intermittently, in hospitals, laboratories or even in home settings. The technology exploits measurements of thermal transport through near-surface layers of skin to assess flow, with a soft, flexible, and skin-conformal device that can be constructed using commercially available components. Systematic benchtop studies and numerical simulations highlight all of the key considerations. Measurements on 7 patients establish high levels of functionality, with data that reveal time dependent changes in flow associated with positional and inertial effects on the body. Taken together, the results suggest a significant advance in monitoring capabilities for patients with shunted hydrocephalus, with potential for practical use across a range of settings and circumstances, and additional utility for research purposes in studies of CSF hydrodynamics.

    View details for DOI 10.1038/s41746-020-0239-1

    View details for Web of Science ID 000519040400002

    View details for PubMedID 32195364

    View details for PubMedCentralID PMC7060317

  • Surgical versus conservative treatment of unilateral subaxial non-subluxed facet fractures: A systematic review and meta-analysis. Clinical neurology and neurosurgery Larkin, C. J., Abecassis, Z. A., Yerneni, K. n., Nistal, D. A., Karras, C. L., Greg Frankel, H. n., Ayer, A. n., Dahdaleh, N. S. 2020; 199: 106280


    Unilateral subaxial non-subluxed facet fractures (USNSFF) are a pathology seen in traumatic events such as motor vehicle accidents. Management involves either rigid collar bracing or surgical intervention. There currently is no consensus on the treatment of these injuries; this review aims to examine the extant data for recommendations as to which treatment is more effective.MEDLINE, Scopus, and the Cochrane trial register were all searched on January 16, 2020, comparing outcomes for surgical and conservative therapy for USNSFF. The meta-analysis examined rates of treatment failure (need for subsequent operative management) in conservative versus surgical management. The meta-analysis was performed using a random effects model, with visualization in forest and L'Abbé plots.We identified six retrospective studies describing 270 patients, with three studies describing 137 patients used in the meta-analysis. Overall, a surgical success rate of 97.7 % and a non-operative success rate of 79.7 % was observed. A random effects model risk ratio of 1.66 (95 % CI: 0.61-4.52) was obtained, suggesting efficacy of surgical management over conservative management.The need for surgical intervention subsequent to initial management in the treatment of USNSFF was found to be lower in surgical treatment in contrast to conservative management. However, the studies that were included in the meta-analysis had patient cohorts with much higher rates of neurological deficit and ligamentous injury on presentation, indicating that these may be prognostic indicators of conservative management failure. Furthermore, those that did fail conservative management did not develop severely debilitating conditions. Accordingly, conservative treatment is generally sufficient as a first step in a majority of cases of USNSFF lacking neurological deficit or ligamentous involvement.

    View details for DOI 10.1016/j.clineuro.2020.106280

    View details for PubMedID 33080428

  • Impact of medical student involvement on outcomes following spine surgery: A single center analysis of 6485 patients JOURNAL OF CLINICAL NEUROSCIENCE Abecassis, Z. A., Hopkins, B., Win, P., Yerneni, K., Karras, C. L., Frankel, H. G., Ayer, A., Dandaleh, N. S. 2019; 69: 143–48


    Medical student (MS) observation and assistance in the operating room (OR) is a critical component of medical education. Though participation in the operating room has many benefits to the medical student, the potential cost of these experiences to the patients must be taken into account. Other studies have shown differences in outcomes with resident involvement, but the effect of medical students in the OR has been poorly understood. The objective of this study was to understand how medical students and residents impacted surgical outcomes in posterior spinal fusions, anterior cervical discectomy and fusions (ACDFs), and lumbar discectomies. We conducted a retrospective study of patients undergoing posterior spinal fusions, ACDFs, and lumbar discectomies over 15 years. There were 6485 patients met the inclusion criteria of either undergoing a posterior fusion, ACDF or lumbar discectomy (1250 posterior fusion, 1381 ACDF, 3854 lumbar discectomies). Overall, little difference was observed when a medical student was present for surgical outcomes including length of stay, infection, and readmission. For ACDFs, having a medical student present had a significantly longer procedure durations (OR = 1.612, p = 0.001) than cases without. Besides slightly longer operative time (in posterior fusions), there were no major differences in outcomes when a medical student was present in the OR.

    View details for DOI 10.1016/j.jocn.2019.08.009

    View details for Web of Science ID 000498325100025

    View details for PubMedID 31427233

  • Epidermal electronics for noninvasive, wireless, quantitative assessment of ventricular shunt function in patients with hydrocephalus SCIENCE TRANSLATIONAL MEDICINE Krishnan, S. R., Ray, T. R., Ayer, A. B., Ma, Y., Gutruf, P., Lee, K., Lee, J., Wei, C., Feng, X., Ng, B., Abecassis, Z. A., Murthy, N., Stankiewicz, I., Freudman, J., Stillman, J., Kim, N., Young, G., Goudeseune, C., Ciraldo, J., Tate, M., Huang, Y., Potts, M., Rogers, J. A. 2018; 10 (465)


    Hydrocephalus is a common and costly neurological condition caused by the overproduction and/or impaired resorption of cerebrospinal fluid (CSF). The current standard of care, ventricular catheters (shunts), is prone to failure, which can result in nonspecific symptoms such as headaches, dizziness, and nausea. Current diagnostic tools for shunt failure such as computed tomography (CT), magnetic resonance imaging (MRI), radionuclide shunt patency studies (RSPSs), and ice pack-mediated thermodilution have disadvantages including high cost, poor accuracy, inconvenience, and safety concerns. Here, we developed and tested a noninvasive, skin-mounted, wearable measurement platform that incorporates arrays of thermal sensors and actuators for precise, continuous, or intermittent measurements of flow through subdermal shunts, without the drawbacks of other methods. Systematic theoretical and experimental benchtop studies demonstrate high performance across a range of practical operating conditions. Advanced electronics designs serve as the basis of a wireless embodiment for continuous monitoring based on rechargeable batteries and data transmission using Bluetooth protocols. Clinical studies involving five patients validate the sensor's ability to detect the presence of CSF flow (P = 0.012) and further distinguish between baseline flow, diminished flow, and distal shunt failure. Last, we demonstrate processing algorithms to translate measured data into quantitative flow rate. The sensor designs, fabrication schemes, wireless architectures, and patient trials reported here represent an advance in hydrocephalus diagnostics with ability to visualize flow in a simple, user-friendly mode, accessible to the physician and patient alike.

    View details for DOI 10.1126/scitranslmed.aat8437

    View details for Web of Science ID 000448834800004

    View details for PubMedID 30381410

  • Low-Dose Gamma Knife Radiosurgery for Vestibular Schwannomas: Tumor Control and Cranial Nerve Function Preservation After 11 Gy JOURNAL OF NEUROLOGICAL SURGERY PART B-SKULL BASE Schumacher, A. J., Lall, R. R., Lall, R. R., Nanney, A., Ayer, A., Sejpal, S., Liu, B. P., Marymont, M., Lee, P., Bendok, B. R., Kalapurakal, J. A., Chandler, J. P. 2017; 78 (1): 2–10


    This study aims to report tumor control rates and cranial nerve function after low dose (11.0 Gy) Gamma knife radiosurgery (GKRS) in patients with vestibular schwannomas.A retrospective chart review was performed on 30 consecutive patients with vestibular schwannomas treated from March 2004 to August 2010 with GKRS at the Robert H. Lurie Comprehensive Cancer Center of Northwestern University. The marginal dose for all patients was 11.0 Gy prescribed to the 50% isodose line. Median follow-up time was 42 months. The median treatment volume was 0.53 cm3. Hearing data were obtained from audiometry reports before and after radiosurgery.The actuarial progression free survival (PFS) based on freedom from surgery was 100% at 5 years. PFS based on freedom from persistent growth was 91% at 5 years. One patient experienced tumor progression requiring resection at 87 months. Serviceable hearing, defined as Gardner-Robertson score of I-II, was preserved in 50% of patients. On univariate and multivariate analyses, only higher mean and maximum dose to the cochlea significantly decreased the proportion of patients with serviceable hearing.Vestibular schwannomas can be treated with low doses (11.0 Gy) of GKRS with good tumor control and cranial nerve preservation.

    View details for DOI 10.1055/s-0036-1584231

    View details for Web of Science ID 000394341800002

    View details for PubMedID 28180036

    View details for PubMedCentralID PMC5288117

  • Cavernous sinus metastases treated with gamma knife (TM) stereotactic radiosurgery JOURNAL OF RADIOSURGERY AND SBRT Ayer, A., Page, B. R., Lucas, J. T., Bourland, J., Oliver, E. R., Tatter, S. B., Ellis, T. L., Chan, M. D. 2014; 3 (2): 131–37


    Cavernous sinus metastases represent difficult clinical scenarios because of the lack of surgical options. We investigate the use of Gamma Knife stereotactic radiosurgery (GKRS) as a treatment option of these metastases.To determine the patterns of failure for cavernous sinus metastases and to identify factors that predict for improved outcomes.This is a retrospective review of 19 patients treated with GKRS for cavernous sinus metastases over a 9-year period between May 2002 and October 2011. The median marginal tumor dose was 18 Gy. Patients were followed with serial imaging. Kaplan Meier analysis was used to estimate local control and overall survival. Fischer exact test was used to determine any predictive factors for local control or survival.Median follow-up time was 22.4 months. Kaplan Meier estimate of overall survival at 1, 2, and 4 years was 76%, 44%, and 44% survival, respectively. 11 patients experienced intracranial failure. Of these, 7 (64%) were local and 4 (36%) were distant intracranial failures. Local control was 76%, 44%, and 44% at 1, 2 and 4 years, respectively. Six of seven local failures in the series were considered to be marginal failures because they were abutting the 50% isodose volume. Head and neck primary tumors were associated with 86% of local failures (P = 0.017) and was the only factor that predicted for local failure.GKRS appears to be a feasible and safe modality for treatment of cavernous sinus metastases. Local failures appear to be due to a marginal miss of microscopically occult disease.

    View details for Web of Science ID 000219423400005

    View details for PubMedID 29296394

    View details for PubMedCentralID PMC5675485

  • A ruptured infectious intracranial aneurysm with a combined fungal and bacterial etiology CLINICAL NEUROLOGY AND NEUROSURGERY Abecassis, I. J., Adel, J. G., Ayer, A., Batjer, H. 2013; 115 (11): 2393–96
  • Clinical Trials for Neuroprotective Therapies in Intracerebral Hemorrhage: A New Roadmap from Bench to Bedside TRANSLATIONAL STROKE RESEARCH Ayer, A., Hwang, B. Y., Appelboom, G., Connolly, E. S. 2012; 3 (4): 409-417


    The most deadly form of stroke, intracerebral hemorrhage (ICH) continues to puzzle researchers and produce substantial decrements in the quality of patients' lives. Intensive basic research has devised many agents with putative benefit in mitigating the devastating effects of ICH, but these therapies have been largely ineffective in the transition to clinical trials. However, a steady translational pipeline continues to provide new avenues of treatment that may be effective in the management of this condition. In this review, we aim to summarize the array of neuroprotective clinical trials and techniques used in the history of ICH, and delineate the progression of relevant research to date. Furthermore, we provide insight into methods that may allow for better translation of basic science advances into productive clinical trials.

    View details for DOI 10.1007/s12975-012-0207-4

    View details for Web of Science ID 000311407000001

    View details for PubMedID 24323830

  • IL-27 Enhances LPS-Induced Proinflammatory Cytokine Production via Upregulation of TLR4 Expression and Signaling in Human Monocytes JOURNAL OF IMMUNOLOGY Guzzo, C., Ayer, A., Basta, S., Banfield, B. W., Gee, K. 2012; 188 (2): 864–73


    IL-27, which is produced by activated APCs, bridges innate and adaptive immunity by regulating the development of Th cells. Recent evidence supports a role for IL-27 in the activation of monocytic cells in terms of inflammatory responses. Indeed, proinflammatory and anti-inflammatory activities are attributed to IL-27, and IL-27 production itself is modulated by inflammatory agents such as LPS. IL-27 primes LPS responses in monocytes; however, the molecular mechanism behind this phenomenon is not understood. In this study, we demonstrate that IL-27 priming results in enhanced LPS-induced IL-6, TNF-α, MIP-1α, and MIP-1β expression in human primary monocytes. To elucidate the molecular mechanisms responsible for IL-27 priming, we measured levels of CD14 and TLR4 required for LPS binding. We determined that IL-27 upregulates TLR4 in a STAT3- and NF-κB-dependent manner. Immunofluorescence microscopy revealed enhanced membrane expression of TLR4 and more distinct colocalization of CD14 and TLR4 upon IL-27 priming. Furthermore, IL-27 priming enhanced LPS-induced activation of NF-κB family members. To our knowledge, this study is the first to show a role for IL-27 in regulating TLR4 expression and function. This work is significant as it reveals new mechanisms by which IL-27 can enhance proinflammatory responses that can occur during bacterial infections.

    View details for DOI 10.4049/jimmunol.1101912

    View details for Web of Science ID 000299323700041

    View details for PubMedID 22156348

  • Advances in Neuroprotective Strategies: Potential Therapies for Intracerebral Hemorrhage CEREBROVASCULAR DISEASES Hwang, B. Y., Appelboom, G., Ayer, A., Kellner, C. P., Kotchetkov, I. S., Gigante, P. R., Haque, R., Kellner, M., Connolly, E. S. 2011; 31 (3): 211-222


    Intracerebral hemorrhage (ICH) is associated with higher mortality and morbidity than any other form of stroke. However, there currently are no treatments proven to improve outcomes after ICH, and therefore, new effective therapies are urgently needed. Growing insight into ICH pathophysiology has led to the development of neuroprotective strategies that aim to improve the outcome through reduction of secondary pathologic processes. Many neuroprotectants target molecules or pathways involved in hematoma degradation, inflammation or apoptosis, and have demonstrated potential clinical benefits in experimental settings. We extensively reviewed the current understanding of ICH pathophysiology as well as promising experimental neuroprotective agents with particular focus on their mechanisms of action. Continued advances in ICH knowledge, increased understanding of neuroprotective mechanisms, and improvement in the ability to modulate molecular and pathologic events with multitargeting agents will lead to successful clinical trials and bench-to-bedside translation of neuroprotective strategies.

    View details for DOI 10.1159/000321870

    View details for Web of Science ID 000291816300001

    View details for PubMedID 21178344

    View details for PubMedCentralID PMC3721946

  • The sociopolitical history and physiological underpinnings of skull deformation NEUROSURGICAL FOCUS Ayer, A., Campbell, A., Appelboom, G., Hwang, B. Y., McDowell, M., Piazza, M., Feldstein, N. A., Anderson, R. C. 2010; 29 (6)


    In this report, the evidence, mechanisms, and rationale for the practice of artificial cranial deformation (ACD) in ancient Peru and during Akhenaten's reign in the 18th dynasty in Egypt (1375-1358 BCE) are reviewed. The authors argue that insufficient attention has been given to the sociopolitical implications of the practice in both regions. While evidence from ancient Peru is widespread and complex, there are comparatively fewer examples of deformed crania from the period of Akhenaten's rule. Nevertheless, Akhenaten's own deformity, the skull of the so-called "Younger Lady" mummy, and Tutankhamen's skull all evince some degree of plagiocephaly, suggesting the need for further research using evidence from depictions of the royal family in reliefs and busts. Following the anthropological review, a neurosurgical focus is directed to instances of plagiocephaly in modern medicine, with special attention to the conditions' etiology, consequences, and treatment. Novel clinical studies on varying modes of treatment will also be studied, together forming a comprehensive review of ACD, both in the past and present.

    View details for DOI 10.3171/2010.9.FOCUS10202

    View details for Web of Science ID 000285648900002

    View details for PubMedID 21121715