Alexander M. Lopez
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Previous Organizations / Institutes
The organizations / institutes from the scholar's other articles in the past ten years
Alexander M. Lopez has a total of 77 co-authors. Here are the top co-authors by number of shared publications:
- Michael Y. Oh
Department of Neurological Surgery at the University of California, Irvine Medical Center
4 shared publications - Cathleen C. Kuo
Jacobs School of Medicine and Biomedical Sciences at University at Buffalo, Buffalo, New York, USA
3 shared publications - Nolan James Brown
Department of Neurosurgery, University of California Irvine, Orange, CA, USA
3 shared publications - Zach Pennington
Department of Neurologic Surgery, Mayo Clinic, Rochester, Minnesota
3 shared publications - Benoit M. Dawant
Vanderbilt University, Department of Electrical and Computer Engineering, Nashville, Tennessee, United States
2 shared publications - Daniel O. Claassen
Department of Neurology, Vanderbilt University Medical Center, Nashville, USA
2 shared publications
Latest Publications
- Top Cited PapersOpen Access
- 30 June 2025
- Published by The Korean Spinal Neurosurgery Society in Neurospine
- Vol. 22 (2) , 389-402
A Systematic Review of Treatment Guidelines for Lumbar Disc Herniation
Various treatments have been developed for treating herniated lumbar discs (HLD), which have been examined by professional associations when composing clinical guidelines that provide structured approaches to treating HLD. This paper aims to gather recent guidelines and summarize their conclusions on nonsurgical and surgical treatment options. PubMed, Web of Science, Scopus, Guidelines International Network, Turning Research into Practice databases, and websites of medical societies were searched for clinical guidelines of HLD. Full-text guidelines published by a professional association in English relevant to HLD were included. Comparisons among guidelines were made based on the treatments evaluated, and recommendation grades were recorded when provided by the guidelines. A total of 12 guidelines were included, with 4 by non-United States (US) or international associations, 3 by US pain societies, 2 by surgical societies, 2 by government agencies, and 1 by a multidisciplinary medical society. Treatments assessed included surgical, invasive nonsurgical, and noninvasive nonsurgical interventions. Three guidelines did not include surgical treatments, and 2 guidelines did not include nonsurgical therapies. Recommendation criteria varied among guidelines due to differences in the intended audience. HLD can be treated with various modalities with specific therapies offering better pain relief. Despite inconsistency in the recommendation grades of most treatments, established surgical techniques and epidural injections were reported with higher confidence in recommendation estimates, while inadequate supporting evidence was shown for noninvasive therapies except cognitive behavioral therapy. Future studies could incorporate and comment on some of the newer methods of treating HLD.
- 30 June 2025
- Published by The Korean Spinal Neurosurgery Society in Neurospine
- Vol. 22 (2) , 389-402
Top Cited PapersOpen AccessA Systematic Review of Treatment Guidelines for Lumbar Disc Herniation
Various treatments have been developed for treating herniated lumbar discs (HLD), which have been examined by professional associations when composing clinical guidelines that provide structured approaches to treating HLD. This paper aims to gather recent guidelines and summarize their conclusions on nonsurgical and surgical treatment options. PubMed, Web of Science, Scopus, Guidelines International Network, Turning Research into Practice databases, and websites of medical societies were searched for clinical guidelines of HLD. Full-text guidelines published by a professional association in English relevant to HLD were included. Comparisons among guidelines were made based on the treatments evaluated, and recommendation grades were recorded when provided by the guidelines. A total of 12 guidelines were included, with 4 by non-United States (US) or international associations, 3 by US pain societies, 2 by surgical societies, 2 by government agencies, and 1 by a multidisciplinary medical society. Treatments assessed included surgical, invasive nonsurgical, and noninvasive nonsurgical interventions. Three guidelines did not include surgical treatments, and 2 guidelines did not include nonsurgical therapies. Recommendation criteria varied among guidelines due to differences in the intended audience. HLD can be treated with various modalities with specific therapies offering better pain relief. Despite inconsistency in the recommendation grades of most treatments, established surgical techniques and epidural injections were reported with higher confidence in recommendation estimates, while inadequate supporting evidence was shown for noninvasive therapies except cognitive behavioral therapy. Future studies could incorporate and comment on some of the newer methods of treating HLD.
- Open Access
- 26 March 2024
- Published by MDPI AG in Bioengineering
- Vol. 11 (4) , 312
Outcome of Percutaneous Endoscopic Lumbar Discectomy in Relation to the Surgeon’s Experience: Propensity Score Matching
Percutaneous endoscopic lumbar discectomy (PELD) presents a challenging learning curve, and the correlation between surgeon experience and clinical outcomes remains contentious. This retrospective study aimed to compare the outcomes of PELD performed by a single surgeon at beginner and experienced stages. Propensity score matching selected 150 patients (75 per group) with a minimum 3-year follow-up. Clinical and radiological outcomes, perioperative complications, and adverse events were assessed. Baseline characteristics, pain improvement, patient satisfaction, and radiological outcomes did not differ between the groups. However, operation time was longer in the beginner group than in the experienced group (57.5 min [IQR, 50.0–70.0] versus 50.0 min [IQR, 45.0–55.0], p < 0.001). The beginner group had higher perioperative complication rates (eight patients [10.7%] versus one patient [1.3%], with a hazard ratio of 8.836 [95% CI, 1.077–72.514], p = 0.034) and lower 3-year survival without adverse events (19 patients [25.3%] in the beginner group and 10 patients [13.3%] in the experienced group, p = 0.045). Our findings indicate that the clinical outcomes were more favorable in patients operated on at the experienced stage compared to those treated at the beginner stage.
- 26 March 2024
- Published by MDPI AG in Bioengineering
- Vol. 11 (4) , 312
Open AccessOutcome of Percutaneous Endoscopic Lumbar Discectomy in Relation to the Surgeon’s Experience: Propensity Score Matching
Percutaneous endoscopic lumbar discectomy (PELD) presents a challenging learning curve, and the correlation between surgeon experience and clinical outcomes remains contentious. This retrospective study aimed to compare the outcomes of PELD performed by a single surgeon at beginner and experienced stages. Propensity score matching selected 150 patients (75 per group) with a minimum 3-year follow-up. Clinical and radiological outcomes, perioperative complications, and adverse events were assessed. Baseline characteristics, pain improvement, patient satisfaction, and radiological outcomes did not differ between the groups. However, operation time was longer in the beginner group than in the experienced group (57.5 min [IQR, 50.0–70.0] versus 50.0 min [IQR, 45.0–55.0], p < 0.001). The beginner group had higher perioperative complication rates (eight patients [10.7%] versus one patient [1.3%], with a hazard ratio of 8.836 [95% CI, 1.077–72.514], p = 0.034) and lower 3-year survival without adverse events (19 patients [25.3%] in the beginner group and 10 patients [13.3%] in the experienced group, p = 0.045). Our findings indicate that the clinical outcomes were more favorable in patients operated on at the experienced stage compared to those treated at the beginner stage.
- Open Access
- 15 March 2024
- Published by Elsevier in World Neurosurgery
- Vol. 186, 35-42
What is the Philosophy of Neurosurgery? Systematic Review and Defining the Discipline
- 15 March 2024
- Published by Elsevier in World Neurosurgery
- Vol. 186, 35-42
Open AccessWhat is the Philosophy of Neurosurgery? Systematic Review and Defining the Discipline
- Open Access
- 31 December 2023
- Published by Asian Spine Journal (ASJ) in Asian Spine Journal
- Vol. 17 (6) , 1139-1154
Endoscopic Anterior Lumbar Interbody Fusion: Systematic Review and Meta-Analysis
Laparoscopic anterior lumbar interbody fusion (L-ALIF), which employs laparoscopic cameras to facilitate a less invasive approach, originally gained traction during the 1990s but has subsequently fallen out of favor. As the envelope for endoscopic approaches continues to be pushed, a recurrence of interest in laparoscopic and/or endoscopic anterior approaches seems possible. Therefore, evaluating the current evidence base in regard to this approach is of much clinical relevance. To this end, a systematic literature search was performed according to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines using the following keywords: “(laparoscopic OR endoscopic) AND (anterior AND lumbar).” Out of the 441 articles retrieved, 22 were selected for quantitative analysis. The primary outcome of interest was the radiographic fusion rate. The secondary outcome was the incidence of perioperative complications. Meta-analysis was performed using RStudio’s “metafor” package. Of the 1,079 included patients (mean age, 41.8±2.9 years), 481 were males (44.6%). The most common indication for L-ALIF surgery was degenerative disk disease (reported by 18 studies, 81.8%). The mean follow-up duration was 18.8±11.2 months (range, 6–43 months). The pooled fusion rate was 78.9% (95% confidence interval [CI], 68.9–90.4). Complications occurred in 19.2% (95% CI, 13.4–27.4) of L-ALIF cases. Additionally, 7.2% (95% CI, 4.6–11.4) of patients required conversion from L-ALIF to open surgery. Although L-ALIF does not appear to be supported by studies available in the literature, it is important to consider the context from which these results have been obtained. Even if these results are taken at face value, the failure of endoscopy to have a role in the ALIF approach does not mean that it should not be incorporated in posterior approaches.
- 31 December 2023
- Published by Asian Spine Journal (ASJ) in Asian Spine Journal
- Vol. 17 (6) , 1139-1154
Open AccessEndoscopic Anterior Lumbar Interbody Fusion: Systematic Review and Meta-Analysis
Laparoscopic anterior lumbar interbody fusion (L-ALIF), which employs laparoscopic cameras to facilitate a less invasive approach, originally gained traction during the 1990s but has subsequently fallen out of favor. As the envelope for endoscopic approaches continues to be pushed, a recurrence of interest in laparoscopic and/or endoscopic anterior approaches seems possible. Therefore, evaluating the current evidence base in regard to this approach is of much clinical relevance. To this end, a systematic literature search was performed according to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines using the following keywords: “(laparoscopic OR endoscopic) AND (anterior AND lumbar).” Out of the 441 articles retrieved, 22 were selected for quantitative analysis. The primary outcome of interest was the radiographic fusion rate. The secondary outcome was the incidence of perioperative complications. Meta-analysis was performed using RStudio’s “metafor” package. Of the 1,079 included patients (mean age, 41.8±2.9 years), 481 were males (44.6%). The most common indication for L-ALIF surgery was degenerative disk disease (reported by 18 studies, 81.8%). The mean follow-up duration was 18.8±11.2 months (range, 6–43 months). The pooled fusion rate was 78.9% (95% confidence interval [CI], 68.9–90.4). Complications occurred in 19.2% (95% CI, 13.4–27.4) of L-ALIF cases. Additionally, 7.2% (95% CI, 4.6–11.4) of patients required conversion from L-ALIF to open surgery. Although L-ALIF does not appear to be supported by studies available in the literature, it is important to consider the context from which these results have been obtained. Even if these results are taken at face value, the failure of endoscopy to have a role in the ALIF approach does not mean that it should not be incorporated in posterior approaches.
- Open Access
- 30 June 2023
- Published by Elsevier in World Neurosurgery
- Vol. 177, e600-e612
External Validation of the Global Alignment and Proportion Score as Prognostic Tool for Corrective Surgery in Adult Spinal Deformity: A Systematic Review and Meta-Analysis
- 30 June 2023
- Published by Elsevier in World Neurosurgery
- Vol. 177, e600-e612
Open AccessExternal Validation of the Global Alignment and Proportion Score as Prognostic Tool for Corrective Surgery in Adult Spinal Deformity: A Systematic Review and Meta-Analysis
- 13 March 2023
- Published by Elsevier in World Neurosurgery
- Vol. 174, 81-115
Resident Training in Spine Surgery: A Systematic Review of Simulation-Based Educational Models
- 13 March 2023
- Published by Elsevier in World Neurosurgery
- Vol. 174, 81-115
Resident Training in Spine Surgery: A Systematic Review of Simulation-Based Educational Models
- Open Access
- 5 August 2020
- Published by Oxford University Press (OUP) in Cerebral Cortex Communications
- Vol. 1 (1) , tgaa083
Subthalamic Nucleus Subregion Stimulation Modulates Inhibitory Control
Patients with Parkinson’s disease (PD) often experience reductions in the proficiency to inhibit actions. The motor symptoms of PD can be effectively treated with deep brain stimulation (DBS) of the subthalamic nucleus (STN), a key structure in the frontal–striatal network that may be directly involved in regulating inhibitory control. However, the precise role of the STN in stopping control is unclear. The STN consists of functional subterritories linked to dissociable cortical networks, although the boundaries of the subregions are still under debate. We investigated whether stimulating the dorsal and ventral subregions of the STN would show dissociable effects on ability to stop. We studied 12 PD patients with STN DBS. Patients with two adjacent contacts positioned within the bounds of the dorsal and ventral STN completed two testing sessions (OFF medication) with low amplitude stimulation (0.4 mA) at either the dorsal or ventral contacts bilaterally, while performing the stop task. Ventral, but not dorsal, DBS improved stopping latencies. Go reactions were similar between dorsal and ventral DBS STN. Stimulation in the ventral, but not dorsal, subregion of the STN improved stopping speed, confirming the involvement of the STN in stopping control and supporting the STN functional subregions.
- 5 August 2020
- Published by Oxford University Press (OUP) in Cerebral Cortex Communications
- Vol. 1 (1) , tgaa083
Open AccessSubthalamic Nucleus Subregion Stimulation Modulates Inhibitory Control
Patients with Parkinson’s disease (PD) often experience reductions in the proficiency to inhibit actions. The motor symptoms of PD can be effectively treated with deep brain stimulation (DBS) of the subthalamic nucleus (STN), a key structure in the frontal–striatal network that may be directly involved in regulating inhibitory control. However, the precise role of the STN in stopping control is unclear. The STN consists of functional subterritories linked to dissociable cortical networks, although the boundaries of the subregions are still under debate. We investigated whether stimulating the dorsal and ventral subregions of the STN would show dissociable effects on ability to stop. We studied 12 PD patients with STN DBS. Patients with two adjacent contacts positioned within the bounds of the dorsal and ventral STN completed two testing sessions (OFF medication) with low amplitude stimulation (0.4 mA) at either the dorsal or ventral contacts bilaterally, while performing the stop task. Ventral, but not dorsal, DBS improved stopping latencies. Go reactions were similar between dorsal and ventral DBS STN. Stimulation in the ventral, but not dorsal, subregion of the STN improved stopping speed, confirming the involvement of the STN in stopping control and supporting the STN functional subregions.
- 28 April 2020
- Published by Wiley in Movement Disorders
- Vol. 35 (7) , 1181-1188
Structural Correlates of the Sensorimotor Cerebellum in Parkinson's Disease and Essential Tremor
Background: Parkinson's disease (PD) and essential tremor (ET) are commonly encountered movement disorders. Pathophysiologic processes that localize to the cerebellum are described in both. There are limited studies investigating cerebellar structural changes in these conditions, largely because of inherent challenges in the efficiency of segmentation.Methods: We applied a novel multiatlas cerebellar segmentation method to T1‐weighted images in 282 PD and 111 essential tremor patients to define 26 cerebellar lobule volumes. The severity of postural and resting tremor in both populations and gait and postural instability in PD patients were defined using subscores of the UPDRS and Washington Heights‐Inwood Genetic Study motor scales. These clinical measurements were related to lobule volume size. Multiple comparisons were controlled using a false discovery rate method.Results: Group differences were identified between ET and PD patients, with reductions in deep cerebellar nucleus volume in ET versus reduced lobule VI volume in PD. In ET patients, lobule VIII was negatively correlated with the severity of postural tremor. In PD patients, lobule IV was positively correlated with resting tremor and total tremor severity. We observed differences in cerebellar structure that localized to sensorimotor lobules of the cerebellum. Lobule volumes appeared to differentially relate to clinical symptoms, suggesting important clinicopathologic distinctions between these conditions. These results emphasize the role of the cerebellum in tremor symptoms and should foster future clinical and pathologic investigations of the sensorimotor lobules of the cerebellum. © 2020 International Parkinson and Movement Disorder Society
- 28 April 2020
- Published by Wiley in Movement Disorders
- Vol. 35 (7) , 1181-1188
Structural Correlates of the Sensorimotor Cerebellum in Parkinson's Disease and Essential Tremor
Background: Parkinson's disease (PD) and essential tremor (ET) are commonly encountered movement disorders. Pathophysiologic processes that localize to the cerebellum are described in both. There are limited studies investigating cerebellar structural changes in these conditions, largely because of inherent challenges in the efficiency of segmentation.Methods: We applied a novel multiatlas cerebellar segmentation method to T1‐weighted images in 282 PD and 111 essential tremor patients to define 26 cerebellar lobule volumes. The severity of postural and resting tremor in both populations and gait and postural instability in PD patients were defined using subscores of the UPDRS and Washington Heights‐Inwood Genetic Study motor scales. These clinical measurements were related to lobule volume size. Multiple comparisons were controlled using a false discovery rate method.Results: Group differences were identified between ET and PD patients, with reductions in deep cerebellar nucleus volume in ET versus reduced lobule VI volume in PD. In ET patients, lobule VIII was negatively correlated with the severity of postural tremor. In PD patients, lobule IV was positively correlated with resting tremor and total tremor severity. We observed differences in cerebellar structure that localized to sensorimotor lobules of the cerebellum. Lobule volumes appeared to differentially relate to clinical symptoms, suggesting important clinicopathologic distinctions between these conditions. These results emphasize the role of the cerebellum in tremor symptoms and should foster future clinical and pathologic investigations of the sensorimotor lobules of the cerebellum. © 2020 International Parkinson and Movement Disorder Society