Are Facial Gunshot Wounds More Fatal When They Are Self-Inflicted or Other-Inflicted?

Study Design: This was a retrospective cohort study of the 2014 Nationwide Emergency Department Sample (NEDS). Objective: Intraoral and submental projectile entry points may be less fatal than other facial entry points due to the indirect access to the intracranial structures and the protection offered by the intervening maxillofacial complex. Because intraoral and submental trajectories are almost always present in the setting of attempted suicide, this study sought to determine if intent (self-harm versus other-harm) influenced mortality in facial gunshot wound (GSW) patients. Methods: All patients with a diagnosis of a facial fracture secondary to firearm injury were included in the study sample. The primary predictor was self-harm. Secondary predictors were derived from patient, injury, and hospitalization characteristics. The study outcome was death. Univariate time to event analyses were conducted for all study predictors. A multivariate regression model for mortality was created using all relevant predictors. Results: The final sample included 668 facial GSW injuries, of which 19.3% were attributed to self-harm. Self-inflicted GSWs were more likely to involve the mandible (58.9 vs 46.0%, P < 0.01), ZMC/maxilla (47.3 vs 32.5%, P < 0.01), and intracranial cavity (48.1 vs 22.6%, P < 0.01). The overall mortality rate was 7.3%, and the mean time to death was 2.2 days. After controlling for pertinent covariates, the risk of mortality was independently decreased with mandibular injury (HR = 0.36, P = 0.03). However, mortality was increased by self-harm intent (HR = 3.94, P < 0.01) and intracranial involvement (HR = 11.24, P < 0.01). Conclusions: Consistent with a pattern of intraoral and submental entry points, self-inflicted facial GSWs demonstrated higher rates of mandibular injury. Despite this finding, self-harm injuries still carried a higher incidence of intracranial injury and a greater independent risk of mortality. Our results refute any notion that the mechanism and trajectory of self-inflicted GSWs is less fatal.

Outcomes of Clinical Trials on Osteonecrosis of the Jaw.

OBJECTIVE: The purpose of this study was to provide a cross-sectional view of all registered clinical trials enrolling patients with osteonecrosis of the jaw (ONJ). The primary aim was to report predictors of trial completion and publication of results. MATERIALS AND METHODS: This is a cross-sectional study of ONJ trials registered with ClinicalTrials.gov. For each included entry, trial characteristics and endpoints were recorded. Predictors were enrollment size, etiology, study type, intervention type, sponsor, funding, study locations, number of centers, and specialty of the principal investigator. Outcomes were trial status, publication on PubMed, journal of publication, and length of time between endpoints. Associations between predictors and outcomes were evaluated using chi-square tests and t-tests. RESULTS: The final sample included 26 trials. Overall, 50% of trials were completed and 69% of completed trials were published. Three out of four terminated trials were suspended due to lack of funding. The median enrollment for completed trials was 149 participants with a mean length of five years. All trials included medication-related osteonecrosis of the jaw (MRONJ) patients and 26% also included osteoradionecrosis of the jaw (ORNJ) patients. The majority of trials were observational (65%), conducted internationally (62%), and involved multiple centers (54%). Published trials had a mean time of 5.9 years between trial start and publication, which was comparable to trial length (p=0.90) and appeared in either dental (44%) or cancer (56%) journals. Completion and publication rates were not significantly increased by industry sponsorship/funding, larger enrollment sizes, or multi-center involvement. Oral and maxillofacial surgery was the most represented dental specialty of principal investigators (56%). CONCLUSIONS: The majority of completed ONJ trials had their results published in a timely manner. Evidence-based investigation of ONJ is a multi-disciplinary and international effort. Among all specialists, oral and maxillofacial surgeons led the most ONJ trials.

For Patients With Isolated Cleft Palate Does Revision Palatoplasty Have an Increased Risk of Inpatient Complication Compared to Primary Palatal Repair?

OBJECTIVE: The purpose of this study was to determine whether revision palatoplasty was associated with increased rates of inpatient complication and wound dehiscence compared to primary palatal repair. MATERIALS AND METHODS: This was a retrospective study of patients with isolated cleft palate treated with primary palatoplasty or revision surgery for fistula repair. The records were obtained from the Kids' Inpatient Database between 2000 and 2014. The primary predictor was the type of surgery, classified as either primary or revision palatoplasty. Secondary predictors included demographics and comorbidities. Primary study outcomes were the postoperative complication and dehiscence rates as noted during the hospitalization course. The secondary outcomes related to health care utilization as measured through length of stay (LOS) and hospital charges. RESULTS: A total of 5357 total admissions (95.5% primary, 4.5% revision) were included in the final sample. Fistula repairs (odds ratio = 14.37, P < .01) had significantly greater odds of wound dehiscence. The rates of inpatient complication ranged from 3.5% to 3.7%, and there were no significant differences between primary and revision surgery (P = .82). Complications were independently associated with insurance status and congenital anomalies. Complications and wound dehiscence both significantly increased the LOS and the hospital charges. Fistula repairs had a shorter mean LOS (P = .02), however this did not translate into cost savings (P = .60). CONCLUSIONS: Although the rates of inpatient complications were not significantly different, revision palatoplasty was associated with a greater odds of wound dehiscence. Failure of a primary repair may portend an increased risk of wound failure with subsequent surgeries.

What Are the Predictors of Craniomaxillofacial Injuries From Hoverboard Accidents?

PURPOSE: A hoverboard, or self-balancing scooter, is a battery-powered vehicle with 2 wheels connected by a longboard that requires handsfree operation. The purpose of the present study was to characterize the emergency department visits for hoverboard-related craniomaxillofacial trauma and determine predictors of injuries and hospital admission. MATERIALS AND METHODS: We performed a retrospective cohort study of the National Electronic Injury Surveillance System from 2015 to 2018. The database was searched using the codes for battery-powered vehicles and craniomaxillofacial body parts (ie, head, face, mouth, eyeball, ear). Entries with the term "hoverboard" in their narrative were included. The predictors were gender, age, body part, year, season, setting, and helmet wear. The outcomes were injury diagnoses (ie, dental injury, facial fracture, soft tissue injury, intracranial injury) and hospital admission. Associations between the predictors and outcomes were evaluated using χ2 and t tests. RESULTS: The final sample included 440 patients, of whom 51% were male and 74% were pediatric (age, ≤18 years). Pediatric and male patients were both less likely to wear helmets (P < .01). The injuries had most commonly occurred in the winter (38%) and in a home setting (77%). Facial fractures were more likely in adults (P = .03) and in the summer (P = .04). The overall admission rate was 4.3%. The admission rates were greater for those with facial fractures (P = .02) and intracranial injuries (P = .03) but lower for those with soft tissue injuries (P < .01). Street injuries resulted in a greater admission rate compared with home injuries (P = .01). CONCLUSIONS: Craniomaxillofacial injuries from hoverboard accidents have resulted in emergency department visits and hospital admissions since the vehicle's introduction to the consumer market in 2015. Most cases occurred in the winter, which might reflect increased sales and novice riders during the holiday season. Injuries to adults, in the summer or outdoors, appear to be more severe. Intracranial injuries were the most frequent diagnosis; thus, helmet wear is recommended.

Current Status of Instagram Utilization by Oral and Maxillofacial Surgery Residency Programs: A Comparison With Related Dental and Surgical Specialties.

PURPOSE: The utility of social media in oral and maxillofacial surgery (OMS) residency programs has never been investigated, despite the increasing popularity of such platforms in academic medicine. As a specialty that strives for constant innovation, it is important for OMS programs to participate in the emerging concept of incorporating social media into medical and surgical education. Therefore, this study aimed to evaluate the use of Instagram in OMS residency programs in the United States. METHODS: A cross-sectional study of Instagram search data was performed. The Instagram accounts of OMS residency programs were searched, and their metrics were retrieved from June 1 to June 5, 2020. Factors correlated with the total number of followers were identified. The use of Instagram in OMS residency programs was compared with that in other related dental and surgical residency programs. RESULTS: Only 17 (18.7%) of 91 OMS residency programs had an Instagram account. The number of programs with Instagram accounts exhibited linear growth (R2 = 0.98) since December 2018. The median number of followers was 326 (range, 94 to 2,152), and the median number of posts was 9 (range, 2 to 40). The number of Instagram followers was positively correlated with the number of accounts followed, the number of total posts, and the number of educational posts, and it was negatively correlated with the Instagram engagement rate. Instagram presence did not differ among residency programs for orthodontics (18.2%), periodontics (5.5%), and OMS (P = .067). However, Instagram presence in OMS residency programs was significantly lower than that in plastic surgery (74.7%; P < .001) and otolaryngology residency programs (35.0%; P = .011). CONCLUSIONS: Instagram use in OMS residency programs is growing but is significantly lower than that in related surgical fields. This may represent a missed opportunity for promoting collaboration and efficiently delivering useful information to trainees.

Which Factors Affect the Completion and Publication of Dental Implant Trials?

PURPOSE: Clinical decision making in implant dentistry may be vulnerable to industry influence. The purpose of this study was to identify factors associated with the completion and publication of implant trials. MATERIALS AND METHODS: This was a cross-sectional study of dental implant trials registered with ClinicalTrials.gov. The predictor variables were composed of a set of study characteristics including study design (investigational or observational), topic, sample size (≤50 or >50 participants), investigator specialty (periodontics, oral-maxillofacial surgery, prosthodontics, general/implantology, or other), study site (United States or international), and industry funding (yes or no). The outcome variables were time to study completion and time to publication. Reverse Kaplan-Meier analyses were used to determine time-to-event probabilities, and Cox proportional hazards models were used to identify factors associated with study completion and publication. RESULTS: A total of 317 trials were included in the final sample. The median trial duration was 2.3 years, and the median time from completion to publication was 1.9 years. Compared with periodontist-led trials, oral and maxillofacial surgeon-led trials had greater success with publication (publication rate, 73.0% vs 54.4%; P = .01) but were less likely to be conducted in the United States (US site present, 8.8% vs 46.0%; P < .01). Trials that received industry funding were able to extend their operations by an average period of 1.2 years (P < .01). The projected trial completion rate at 5 years was 78.0%, and the projected publication rate 5 years after completion was 94.0%. Multivariate Cox regression showed that both industry-funded trials (hazard ratio, 0.66; P < .01) and pharmacologic studies (hazard ratio, 1.69; P = .02) were significantly associated with the completion rate. Among completed trials, neither industry sponsorship nor any other factor influenced the publication rate over time. CONCLUSIONS: Trials that were industry funded had lower rates of completion but not publication. Future efforts should explore the reasons for research waste and improve US oral and maxillofacial surgeon involvement in clinical trial research.

Are Motorized Scooters Associated With More Severe Craniomaxillofacial Injuries?

PURPOSE: The purpose of the present study was to compare the severity of craniomaxillofacial injuries between accidents involving motorized and nonmotorized standup scooters. MATERIALS AND METHODS: This is a 20-year cross-sectional study of the National Electronic Injury Surveillance System. Injuries from powered and unpowered standup scooters were included in this study if they involved the head, face, eyeball, mouth, or ear. Study predictors were obtained from both patient and injury characteristics. The study outcome was the probability of hospital admission from the emergency department. A multiple logistic regression model was created to model the probability of admission using all significant univariate predictors. RESULTS: A total of 11,916 records were included in the present study, of which 9.5% involved motorized scooters. The proportion of motorized injuries more than tripled from 2014 (5.8%) to 2018 (22.1%). Motorized injuries occurred more often in older individuals (24.0 vs 8.5 years; P < .01). A greater proportion of motorized injuries involved the head (55.0 vs 36.9%; P < .01) and resulted in concussion (11.5 vs 5.6%; P < .01), fractures (6.7 vs 2.0%; P < .01), and other nonspecified internal organ injuries (31.1 vs 19.6%; P < .01). Motorized scooter injuries had more than triple the admission rate compared to nonmotorized injuries (13.9 vs 3.7%; P < .01). After controlling for potential confounders, injuries from motorized scooters still had double the odds of hospital admission (odds ratio, 2.03; P < .01). CONCLUSIONS: Motorized standup scooters appear to cause more severe injuries than conventional nonmotorized scooters. The recent growth of rentable electric scooters may pose a future public health concern. Ride-sharing companies should ensure that customers are capable of safely and responsibly operating these vehicles.

Characterizing Craniomaxillofacial Injuries in American Professional Sports Leagues.

PURPOSE: The purpose of this study was to characterize the types of craniomaxillofacial (CMF) injuries that occur in professional sports leagues and the associated recovery times. MATERIALS AND METHODS: A retrospective cohort study was designed and implemented using the Pro Sports Transaction Archive. The database was queried for all registered CMF injuries in the 4 main men's major professional sports leagues in the United States from 2013 to 2018. The sport, injury location, and season were the predictor variables, and the frequency and length of time on the injured list were the outcome variables. Descriptive statistics were computed, and Fisher's exact tests were used to determine the association between the predictor and outcome variables. Analysis of variance was used to compare the injury frequency and duration. RESULTS: Of the 198 injuries that met the inclusion criteria, 60 were from Major League Baseball (MLB) (30%), 49 from the National Basketball Association (25%), 8 from the National Football League (4%), and 81 from the National Hockey League (NHL) (41%). Injuries to the midface were most common (mean, 25.2 ± 3.6 injuries per season; P < .001) compared with the upper face (mean, 6.0 ± 2.0 injuries per season) and lower face (mean, 8.4 ± 2.3 injuries per season). The mean time on the injured list after CMF trauma was 8.4 ± 10.4 days, with MLB injuries requiring the shortest duration (mean, 3.9 ± 6.6 days; P = .001). A significant association was found between the injury location and sport (P < .001). However, no statistically significant difference was found in the number of injuries per season from 2013 to 2018 for each league (P = .818). CONCLUSIONS: Midface trauma was significantly more common than upper or lower face trauma in professional sports leagues during the past 5 seasons. The NHL had the greatest injury rate, even after adjustment for games played.

Standing on the Shoulders of Giants: Dental Students Seek Academically Productive Mentors.

PURPOSE: The purpose of this study was to determine whether a strong statistical correlation exists between the involvement of trainee groups and the academic productivity of the senior author. MATERIALS AND METHODS: A retrospective cohort study of publications in the Journal of Oral and Maxillofacial Surgery from 2002 to 2016 was designed and implemented. The primary predictor variables were the presence of a trainee (dental student or oral and maxillofacial surgery [OMS] resident), year of publication, and study design and topic. The outcome variable was the Hirsch index (h-index) of the senior author. Author affiliations were queried using ScienceDirect, and the Scopus database was used to identify the h-index of the senior author from each publication spanning the previous 15 years. Descriptive statistics and t tests were performed to determine significance. RESULTS: Of the 6,398 articles published in the Journal of Oral and Maxillofacial Surgery from January 2002 to December 2016, 1,341 (21.0%) met the inclusion criteria. The mean h-index of senior authors of articles with trainees or OMS residents was not significantly different from the mean h-index of senior authors without trainees (P = .50) or OMS residents (P = .37), whereas the mean h-index of senior authors working with dental students was significantly greater than the h-index of those not working with dental students (P < .01). Dental student mentors had a mean h-index that was below the sample mean from 2002 to 2007 but rose above the sample mean from 2010 to 2016. Trainees were more likely to work with academically productive mentors in orthognathic surgery (P < .01), temporomandibular joint (P < .05), retrospective cohort (P < .05), and innovative technique (P < .05) studies but less likely in randomized controlled trials (P < .05). CONCLUSIONS: Dental students seek more academically productive mentors to a greater degree. More studies should be conducted to elucidate the attributes of the ideal mentor in academic OMS and to determine whether differences in mentorship exist between domestic and foreign OMS programs.

What Is the Health Care Burden of Treating Pediatric Dental Infections on an Inpatient Basis?

PURPOSE: The purpose of this study was to quantify the inpatient burden of pediatric dental infections. MATERIALS AND METHODS: This was a retrospective study of the Kids' Inpatient Database from 2000 to 2014. Patients with a primary admitting diagnosis of cellulitis or an abscess of the oral soft tissues were included. Predictors were drawn from patient characteristics and the types of interventions performed. The outcomes were hospital charges, length of stay (LOS), and procedure count. Multiple linear regression models for each outcome were created using all the predictors. RESULTS: The final sample included 1,779 patients. On average, admissions lasted 2.77 days, patients had a single (1.03) procedure performed, and hospitals billed for $12,729.37. During hospitalization, 41.4% of patients received definitive treatment (incision and drainage or dental extraction), with very few patients requiring some form of mechanical ventilation (2.4%) or a tracheostomy (0.9%). After we controlled for other predictors, dental stage (primary, mixed, or permanent) did not significantly influence the study outcomes. The presence of a medical comorbidity increased the LOS (+0.54 days) and hospital charges (+$3,338.81) but did not carry a need for additional procedures. Definitive treatment contributed to the cost of care (+$5,582.96) but did not meaningfully prolong hospitalization (+0.41 days) when considering the procedure and anesthesia time. Although uncommon, tracheostomy and ventilation independently had the largest impact on all study outcomes. CONCLUSIONS: On the basis of national estimates, the majority of pediatric odontogenic infections appear to follow an uncomplicated hospital course. Definitive treatment increased the cost of care but did not meaningfully prolong the LOS. This finding suggests that additional management is not usually required once source control is achieved. Future economic studies should evaluate whether definitive treatment may be safely provided on an outpatient basis or under observation status for select patients.

Correlation of Cephalometric Analyses With Clinical Impression in Orthognathic Surgery Patients: Harvold and Steiner Analyses.

PURPOSE: A variety of linear (Harvold) and angular (Steiner) cephalometric analyses are used to identify the skeletal basis for a malocclusion; there is no universally accepted standard. The purpose of this study was to compare the concordance of Harvold and Steiner analyses with the clinicians' impression of maxillary and mandibular jaw position. PATIENTS AND METHODS: We conducted a retrospective cohort study of patients who underwent orthognathic surgery at Massachusetts General Hospital from 2012 through 2016. Patients were included if they had symmetrical deformities not related to trauma, clefts, or syndromes; complete records; and a clinical diagnosis documented at initial consultation. The predictor variables were Harvold- and Steiner-derived diagnoses of jaw position (hypoplasia, neutral, or hyperplasia). The outcome variables were maxillary and mandibular clinical impressions (hypoplasia, neutral, or hyperplasia). The concordance, sensitivity, specificity, positive predictive value (PPV), and negative predictive value relative to clinical diagnoses were calculated. RESULTS: During the study period 388 patients had orthognathic surgery and 222(112 females, mean age 26.4±9.9 years) met the inclusion criteria. Harvold and Steiner analyses were 82% and 33% concordant with the maxillary clinical impression, respectively (P < .001), and 62% and 52% concordant with the mandibular clinical impression, respectively (P = .044). Steiner analysis had greater concordance in females (P < .001). For maxillary hypoplasia, the maxillary unit length had a sensitivity of 87%, specificity of 36%, and PPV of 92% and the sell-nasion-A (SNA) point had 28%, 84%, and 93%, respectively. For mandibular hypoplasia, the mandibular unit length had a sensitivity of 52%, specificity of 96%, and PPV of 94% and the sell-nasion-B (SNB) point had 52%, 98%, and 97%, respectively. For mandibular hyperplasia, the mandibular unit length had a sensitivity of 46%, specificity of 93%, and PPV of 40% and the SNB point had 73%, 73%, and 23%, respectively. CONCLUSIONS: Harvold analysis was significantly more consistent with the clinical impression of the maxillary and mandibular sagittal position than Steiner analysis. Both analyses were highly specific and had high PPVs to confirm the clinical impression. Clinicians should consider incorporating Harvold analysis during treatment planning for orthognathic surgery.

A Retrospective Study of Patient Outcomes After Temporomandibular Joint Replacement With Alloplastic Total Joint Prosthesis at Massachusetts General Hospital.

PURPOSE: Disorders of the temporomandibular joint (TMJ) occur frequently, with a prevalence of 15 to 18%. Total joint replacement (TJR) surgery is indicated for severe joint damage associated with impaired function, pain, or occlusal change for which other treatments have been unsuccessful. The aim of this study was to assess changes in pain and range of motion (ROM), as well as postoperative complications and comorbidities, in patients receiving TJR surgery at Massachusetts General Hospital (MGH). PATIENTS AND METHODS: This study is a retrospective review that describes the clinical variables in patients after alloplastic TMJ reconstruction performed at MGH from 2000 to 2015. Clinical variables included primary diagnosis; number of previous surgical procedures; comorbidities; preoperative and postoperative pain; preoperative, intraoperative, and postoperative ROM; and complications. RESULTS: Data were obtained from 95 patients undergoing a total of 108 surgical procedures, with an average follow-up period of 4.48 ± 3.38 years. The most common primary indications for TJR were ankylosis (44%) and inflammatory disease (23%). The maximum interincisal opening improved by a mean of 7.7 ± 10.27 mm, and pain decreased by a mean of 1.5 ± 3.29 points on a visual analog scale. Transient facial nerve palsy (25%) was the most common postoperative complication; however, long-term complications were rare. The most frequent comorbidities were psychiatric disorders (56%) and gastrointestinal disease (46%). Psychiatric patients had similar preoperative pain scores (6.0 ± 2.90) but significantly higher postoperative pain scores (4.7 ± 2.58) compared with nonpsychiatric patients. Twenty-eight percent of patients had prior failed TMJ implant materials, specifically Proplast-Teflon (Vitek, Houston, TX). These patients were significantly older (50.4 ± 8.26 years) and had smaller preoperative ROM (21.7 ± 8.85 mm) and smaller postoperative ROM (28.3 ± 9.59 mm). CONCLUSIONS: Patients showed a statistically significant (P < .01) increase in ROM and reduction in pain. TJR is an effective treatment option in patients with limited mouth opening or severe pain.

Glycosylphosphatidylinositol-anchored proteins as chaperones and co-receptors for FERONIA receptor kinase signaling in Arabidopsis.

The Arabidopsis receptor kinase FERONIA (FER) is a multifunctional regulator for plant growth and reproduction. Here we report that the female gametophyte-expressed glycosylphosphatidylinositol-anchored protein (GPI-AP) LORELEI and the seedling-expressed LRE-like GPI-AP1 (LLG1) bind to the extracellular juxtamembrane region of FER and show that this interaction is pivotal for FER function. LLG1 interacts with FER in the endoplasmic reticulum and on the cell surface, and loss of LLG1 function induces cytoplasmic retention of FER, consistent with transport of FER from the endoplasmic reticulum to the plasma membrane in a complex with LLG1. We further demonstrate that LLG1 is a component of the FER-regulated RHO GTPase signaling complex and that fer and llg1 mutants display indistinguishable growth, developmental and signaling phenotypes, analogous to how lre and fer share similar reproductive defects. Together our results support LLG1/LRE acting as a chaperone and co-receptor for FER and elucidate a mechanism by which GPI-APs enable the signaling capacity of a cell surface receptor.

Characterization of a replication-incompetent pseudorabies virus mutant lacking the sole immediate early gene IE180.

UNLABELLED: The alphaherpesvirus pseudorabies virus (PRV) encodes a single immediate early gene called IE180. The IE180 protein is a potent transcriptional activator of viral genes involved in DNA replication and RNA transcription. A PRV mutant with both copies of IE180 deleted was constructed 20 years ago (S. Yamada and M. Shimizu, Virology 199:366-375, 1994, doi:10.1006/viro.1994.1134), but propagation of the mutant depended on complementing cell lines that expressed the toxic IE180 protein constitutively. Recently, Oyibo et al. constructed a novel set of PRV IE180 mutants and a stable cell line with inducible IE180 expression (H. Oyibo, P. Znamenskiy, H. V. Oviedo, L. W. Enquist, A. Zador, Front. Neuroanat. 8:86, 2014, doi:10.3389/fnana.2014.00086), which we characterized further here. These mutants failed to replicate new viral genomes, synthesize immediate early, early, or late viral proteins, and assemble infectious virions. The PRV IE180-null mutant did not form plaques in epithelial cell monolayers and could not spread from primary infected neurons to second-order neurons in culture. PRV IE180-null mutants lacked the property of superinfection exclusion. When PRV IE180-null mutants infected cells first, subsequent superinfecting viruses were not blocked in cell entry and formed replication compartments in epithelial cells, fibroblasts, and neurons. Cells infected with PRV IE180-null mutants survived as long as uninfected cells in culture while expressing a fluorescent reporter gene. Transcomplementation with IE180 in epithelial cells restored all mutant phenotypes to wild type. The conditional expression of PRV IE180 protein enables the propagation of replication-incompetent PRV IE180-null mutants and will facilitate construction of long-term single-cell-infecting PRV mutants for precise neural circuit tracing and high-capacity gene delivery vectors. IMPORTANCE: Pseudorabies virus (PRV) is widely used for neural tracing in animal models. The virus replicates and spreads between synaptically connected neurons. Current tracing strains of PRV are cytotoxic and kill infected cells. Infected cells exclude superinfection with a second virus, limiting multiple virus infections in circuit tracing. By removing the only immediate early gene of PRV (called IE180), the mutant virus will not replicate or spread in epithelial cells, fibroblasts, or neurons. The wild-type phenotype can be restored by transcomplementation of infected cells with IE180. The PRV IE180-null mutant can express fluorescent reporters for weeks in cells with no toxicity; infected cells survive as long as uninfected cells. Infection with the mutant virus allows superinfection of the same cell with a second virus that can enter and replicate. The PRV IE180-null mutant will permit conditional long-term tracing in animals and is a high-capacity vector for gene delivery.