Literature review of spinal hematoma case reports: causes and outcomes in pediatric, obstetric, neuraxial and pain medicine cases.

BACKGROUND: The risk of spinal epidural hematoma (SEH) has been described in the literature but the impact in various patient populations has not been assessed in the same study. We identified the risk factors for SEH and calculated the OR for recovery in the pediatric, adult and obstetric (OB) patients based on the degree of neurological deficit before surgery. METHODS: Adult non-OB cases were categorized whether they were on anticoagulants or not; SEH was related to neuraxial or pain procedure; or whether there was adherence to the American Society of Regional Anesthesia (ASRA) guidelines. Eligible cases were identified through PubMed and Embase searches in the English literature from 1954 to July 2022. RESULTS: A total of 940 cases were evaluated. In the pediatric cases, SEH was typically spontaneous, related to coagulopathy or athletic trauma. OB cases were spontaneous or related to neuraxial injections. Among adults on anticoagulant(s), SEH was mostly spontaneous with no related etiology or related to neuraxial procedure. SEH occurred despite adherence to the ASRA guidelines. Among non-OB adults not on anticoagulants, SEH was due to trauma, neuraxial injections, surgery or other causes. Neurological recovery was related to the degree of neurological deficit before surgery. CONCLUSIONS: Our data show a preponderance of spontaneous SEH in all patient populations. SEH developed even though the ASRA guidelines were followed, especially in patients on multiple anticoagulants. Patients with less impairment prior to surgery had a higher likelihood of complete recovery, regardless of the interval between surgery and onset of symptoms.

Ultrasound-Guided Occipital Nerve Blocks as Part of Multi-Modal Perioperative Analgesia in Pediatric Posterior Craniotomies: A Case Series.

Various regional anesthetics have been used for postoperative analgesia for pediatric craniotomy. In this case series, we report retrospectively collected data on postoperative pain and analgesic use in 44 patients who received ultrasound-guided occipital nerve blocks in addition to intravenous analgesic agents for posterior craniotomy procedures. In the immediate post-anesthesia care unit, pain was rated as zero or well controlled in 77% of patients, with only 43% requiring intravenous or demand patient-controlled analgesia opioids. There were no block-related complications. Occipital nerve blocks may constitute a safe and effective component of multimodal analgesia in this population.

Safety of antifibrinolytics in 6583 pediatric patients having craniosynostosis surgery: A decade of data reported from the multicenter Pediatric Craniofacial Collaborative Group.

BACKGROUND: Antifibrinolytics such as tranexamic acid and epsilon-aminocaproic acid are effective at reducing blood loss and transfusion in pediatric patients having craniofacial surgery. The Pediatric Craniofacial Collaborative Group has previously reported low rates of seizures and thromboembolic events (equal to no antifibrinolytic given) in open craniofacial surgery. AIMS: To query the Pediatric Craniofacial Collaborative Group database to provide an updated antifibrinolytic safety profile in children given that antifibrinolytics have become recommended standard of care in this surgical population. Additionally, we include the population of younger infants having minimally invasive procedures. METHODS: Patients in the Pediatric Craniofacial Collaborative Group registry between June 2012 and March 2021 having open craniofacial surgery (fronto-orbital advancement, mid and posterior vault, total cranial vault remodeling, intracranial LeFort III monobloc), endoscopic cranial suture release, and spring mediated cranioplasty were included. The primary outcome is the rate of postoperative complications possibly attributable to antifibrinolytic use (seizures, seizure-like activity, and thromboembolic events) in infants and children undergoing craniosynostosis surgery who did or did not receive antifibrinolytics. RESULTS: Forty-five institutions reporting 6583 patients were included. The overall seizure rate was 0.24% (95% CI: 0.14, 0.39%), with 0.20% in the no Antifibrinolytic group and 0.26% in the combined Antifibrinolytic group, with no statistically reported difference. Comparing seizure rates between tranexamic acid (0.22%) and epsilon-aminocaproic acid (0.44%), there was no statistically significant difference (odds ratio = 2.0; 95% CI: 0.6, 6.7; p = .257). Seizure rate was higher in patients greater than 6 months (0.30% vs. 0.18%; p = .327), patients undergoing open procedures (0.30% vs. 0.06%; p = .141), and syndromic patients (0.70% vs. 0.19%; p = .009). CONCLUSIONS: This multicenter international experience of pediatric craniofacial surgery reports no increase in seizures or thromboembolic events in those that received antifibrinolytics (tranexamic acid and epsilon-aminocaproic acid) versus those that did not. This report provides further evidence of antifibrinolytic safety. We recommend following pharmacokinetic-based dosing guidelines for administration.

Patient and operative factors associated with unanticipated intensive care admission and outcomes following posterior fossa decompressions in children: A retrospective study.

INTRODUCTION: Posterior fossa decompression for Chiari I Malformation is a common pediatric neurosurgical procedure. We sought to identify the impact of anesthesia-related intraoperative complications on unanticipated admission to the intensive care unit and outcomes following posterior fossa decompression. METHODS: Medical records of all patients <18 years who underwent surgery for Chiari I malformation between 1/1/09 and 1/31/21 at the Ann & Robert H. Lurie Children's Hospital of Chicago were included. Records were reviewed for patient characteristics, anesthesia-related intraoperative complications, postoperative complications, and surgical outcomes. The primary outcome was the incidence of unanticipated admission to the intensive care unit, and the primary variable of interest was an anesthesia-related intraoperative complication. Patient, surgical characteristics, and year of surgery were also compared between patients with and without an unanticipated admission to the intensive care unit, and a multi-variable adjusted estimate of odds of unanticipated admission to the intensive care unit admission following an anesthesia-related intraoperative complication was performed. Secondary outcomes included anesthesia factors associated with an anesthesia-related intraoperative event, and postoperative complications and surgical outcomes between patients admitted to the intensive care unit and those who were not. RESULTS: Two hundred ninety-six patients with Chiari I Malformation were identified. Clinical characteristics associated with an unanticipated admission to the intensive care unit were younger age, American Society of Anesthesiologist (ASA) physical status >2 and an anesthesia-related intraoperative complication. 29 anesthesia-related intraoperative complications were observed in 25 patients (8.4%). Two of 25 patients (8%) with an anesthesia-related intraoperative complication compared with 3 of 271 (1%) patients without anesthesia-related intraoperative complication had an unanticipated admission to the intensive care unit, odds ratio 7.8 (95% CI 1.2-48.8, p = .010). When adjusted for age, sex, ASA physical status, presenting symptoms, concomitant syringomyelia, previous decompression surgery and year of surgery, the odds ratio for an unanticipated admission to the intensive care unit following an anesthesia-related intraoperative complication was 5.9 (95% CI 0.51-59.6, p = .149). There were no differences in surgical outcomes between patients with or without an unanticipated admission to the intensive care unit. CONCLUSION: Our study demonstrates that although anesthesia-related intraoperative complications during posterior fossa decompression are infrequent, they are associated with an increased risk of an unanticipated admission to the intensive care unit.

Impact of preoperative hyponatraemia on paediatric perioperative mortality.

BACKGROUND: Preoperative hyponatraemia is an independent risk factor for postoperative mortality in adults. To our knowledge, this has not been investigated in children. METHODS: Using data from the 2014 and 2015 data sets of the American College of Surgeons National Surgical Quality Improvement Program-Pediatric (NSQIP-P), we conducted a retrospective study of children undergoing surgery. The primary outcome was 30-day all-cause mortality. The secondary outcomes of interest were postoperative seizure within 30 days and prolonged length of stay. To identify any independent association between preoperative hyponatraemia, defined as mild (serum sodium of 131-135 mEq L-1) or severe (≤130 mEq L-1), and death, postoperative seizures, or prolonged length of stay, multivariable logistic regression models were generated. RESULTS: A total of 152 894 patients were identified, and of these 35 291 were included in the final analysis. Preoperative hyponatraemia was present in 5422 patients or 15.4% of the final cohort. There were 432 (0.80%) deaths at 30 days. Compared with patients with a normal preoperative sodium concentration, those with mild (P=0.003; odds ratio [OR]: 1.59; 95% confidence interval [CI]: 1.17-2.18) and severe (P=0.002; OR: 2.16; 95% CI: 1.32-3.54) hyponatraemia had increased rates of death, after adjusting for co-morbidity and procedural complexity. Both mild (P<0.001; OR: 1.53; 95% CI: 1.42-1.65) and severe (P<0.001; OR: 1.51; 95% CI: 1.19-1.93) hyponatraemia were independently associated with prolonged length of stay, after adjusting for relevant co-variates. CONCLUSIONS: This retrospective analysis identified an association between preoperative hyponatraemia and perioperative mortality and length of stay in paediatric patients.

Pediatric Anesthesiology Fellows' Perception of Quality of Attending Supervision and Medical Errors.

BACKGROUND: Appropriate supervision has been shown to reduce medical errors in anesthesiology residents and other trainees across various specialties. Nonetheless, supervision of pediatric anesthesiology fellows has yet to be evaluated. The main objective of this survey investigation was to evaluate supervision of pediatric anesthesiology fellows in the United States. We hypothesized that there was an indirect association between perceived quality of faculty supervision of pediatric anesthesiology fellow trainees and the frequency of medical errors reported. METHODS: A survey of pediatric fellows from 53 pediatric anesthesiology fellowship programs in the United States was performed. The primary outcome was the frequency of self-reported errors by fellows, and the primary independent variable was supervision scores. Questions also assessed barriers for effective faculty supervision. RESULTS: One hundred seventy-six pediatric anesthesiology fellows were invited to participate, and 104 (59%) responded to the survey. Nine of 103 (9%, 95% confidence interval [CI], 4%-16%) respondents reported performing procedures, on >1 occasion, for which they were not properly trained for. Thirteen of 101 (13%, 95% CI, 7%-21%) reported making >1 mistake with negative consequence to patients, and 23 of 104 (22%, 95% CI, 15%-31%) reported >1 medication error in the last year. There were no differences in median (interquartile range) supervision scores between fellows who reported >1 medication error compared to those reporting ≤1 errors (3.4 [3.0-3.7] vs 3.4 [3.1-3.7]; median difference, 0; 99% CI, -0.3 to 0.3; P = .96). Similarly, there were no differences in those who reported >1 mistake with negative patient consequences, 3.3 (3.0-3.7), compared with those who did not report mistakes with negative patient consequences (3.4 [3.3-3.7]; median difference, 0.1; 99% CI, -0.2 to 0.6; P = .35). CONCLUSIONS: We detected a high rate of self-reported medication errors in pediatric anesthesiology fellows in the United States. Interestingly, fellows' perception of quality of faculty supervision was not associated with the frequency of reported errors. The current results with a narrow CI suggest the need to evaluate other potential factors that can be associated with the high frequency of reported errors by pediatric fellows (eg, fatigue, burnout). The identification of factors that lead to medical errors by pediatric anesthesiology fellows should be a main research priority to improve both trainee education and best practices of pediatric anesthesia.

Evidence for the Efficacy of Systemic Opioid-Sparing Analgesics in Pediatric Surgical Populations: A Systematic Review.

While a large number of studies has examined the efficacy of opioid-sparing analgesics in adult surgical populations, fewer studies are available to guide postoperative pain treatment in pediatric patients. We systematically reviewed available publications on the use of systemic nonopioid agents for postoperative analgesia in pediatric surgical populations. A comprehensive literature search identified meta-analyses and randomized controlled trials (RCTs) assessing the effects of systemic, nonopioid agents on postoperative narcotic requirements or pain scores in pediatric surgical populations. If a meta-analysis was located, we summarized its results and any RCTs published after it. We located and reviewed 11 acetaminophen RCTs, 1 nonsteroidal anti-inflammatory drug (NSAID) meta-analysis, 2 NSAID RCTs, 1 dexamethasone meta-analysis, 3 dexamethasone RCTs, 2 ketamine meta-analyses, 5 ketamine RCTs, 2 gabapentin RCTs, 1 clonidine meta-analysis, 3 magnesium RCTs, 2 dexmedetomidine meta-analyses, and 1 dextromethorphan RCT. No meta-analyses or RCTs were found assessing the perioperative efficacy of intravenous lidocaine, amantadine, pregabalin, esmolol, or caffeine in pediatric surgical patients. The available evidence is limited, but suggests that perioperative acetaminophen, NSAIDs, dexamethasone, ketamine, clonidine, and dexmedetomidine may decrease postoperative pain and opioid consumption in some pediatric surgical populations. Not enough, or no, data exist from which to draw conclusions on the perioperative use of gabapentin, magnesium, dextromethorphan, lidocaine, amantadine, pregabalin, esmolol, and caffeine in pediatric surgical patients. Further pharmacokinetic and pharmacodynamics studies to establish both the clinical benefit and efficacy of nonopioid analgesia in pediatric populations are needed.

The Effect of Systemic Magnesium on Postsurgical Pain in Children Undergoing Tonsillectomies: A Double-Blinded, Randomized, Placebo-Controlled Trial.

BACKGROUND: Tonsillectomy is a frequently performed surgical procedure in children; however, few multimodal analgesic strategies have been shown to improve postsurgical pain in this patient population. Systemic magnesium infusions have been shown to reliably improve postoperative pain in adults, but their effects in pediatric surgical patients remain to be determined. In the current investigation, our main objective was to evaluate the use of systemic magnesium to improve postoperative pain in pediatric patients undergoing tonsillectomy. We hypothesized that children who received systemic magnesium infusions would have less post-tonsillectomy pain than the children who received saline infusions. METHODS: The study was a prospective, randomized, double-blinded, clinical trial. Subjects were randomly assigned using a computer-generated table of random numbers to 1 of the 2 intervention groups: systemic magnesium infusion (initial loading dose 30 mg/kg given over 15 minutes followed by a continuous magnesium infusion 10 mg/kg/h) and the same volume of saline. The primary outcome was pain scores in the postanesthesia care unit (PACU) measured by FLACC (Face, Legs, Activity, Cry, Consolability) pain scores. Pain reduction was measured by the decrement in the area under the pain scale versus 90-minute postoperative time curve using the trapezoidal method. Secondary outcomes included opioid consumption in the PACU, emergence delirium scores (measured by the pediatric anesthesia emergence delirium scale), and parent satisfaction. RESULTS: Sixty subjects were randomly assigned and 60 completed the study. The area under pain scores (up to 90 minutes) was not different between the study groups, median (interquartile range [IQR]) of 30 (0-120) score × min and 45 (0-135) score × min for the magnesium and control groups, respectively (P = 0.74). Similarly, there was no clinically significant difference in the morphine consumption in the PACU between the magnesium group, median (IQR) of 2.0 (0-4.44) mg IV morphine, compared with the control, median (IQR) of 2.5 (0-4.99) mg IV morphine (P = 0.25). The serum level of magnesium was significantly lower in the control group than in the treatment group at the end of the surgery (P < 0.001). CONCLUSIONS: Despite a large number of studies demonstrating the efficacy of systemic magnesium for preventing postsurgical pain in adults, we could not find evidence for a significant clinical benefit of systemic magnesium infusion in children undergoing tonsillectomies. Our findings reiterate the importance of validating multimodal analgesic strategies in children that have been demonstrated to be effective in the adult population.

Selection of subspecialty fellows in anesthesia for pediatric anesthesia: a national survey of program directors in the United States.

BACKGROUND: Several studies have investigated the selection process for medical students, residents, and fellows across different specialties. Currently, the selection criteria used by pediatric anesthesia program directors to select prospective pediatric anesthesia fellows are unknown. OBJECTIVE: To evaluate the criteria used by program directors in the selection of prospective pediatric anesthesia fellows in the United States. METHODS: Survey responses were solicited from 51 pediatric anesthesia fellowship directors in the United States. Questions evaluated department demographic information, the importance of fellowship selection criteria, and program satisfaction with the Match process. RESULTS: Forty-two of 51 fellowship directors responded to the survey (a response rate of 82%). The personal statement was reported as extremely/very important for 30 of 42 (71%) program directors, while research experience and prior publications were reported as extremely/very important for 16 of 41 (39%) and 16 of 41 (39%) program directors, respectively. Programs that offered all the spots through the Match were smaller, median (IQR) number of fellows of 3 (2-6) compared to the ones that did not offer all the spots through the Match, 8 (2-12), P = 0.03. In contrast, no difference in program directors' satisfaction with the Match was detected between smaller (≤ 3 fellows) and larger programs (>3 fellows), P = 0.25. CONCLUSION: A minority of pediatric fellowship program directors rated prior research experience as an important factor in the selection of prospective fellows. The lack of emphasis on research qualities for fellows is potentially concerning for the future of our specialty.

Update on the 2012 guidelines for the management of pediatric traumatic brain injury - information for the anesthesiologist.

Traumatic brain injury (TBI) is a significant contributor to death and disability in children. Considering the prevalence of pediatric TBI, it is important for the clinician to be aware of evidence-based recommendations for the care of these patients. The first edition of the Guidelines for the Acute Medical Management of Severe Traumatic Brain Injury in Infants, Children, and Adolescents was published in 2003. The Guidelines were updated in 2012, with significant changes in the recommendations for hyperosmolar therapy, temperature control, hyperventilation, corticosteroids, glucose therapy, and seizure prophylaxis. Many of these interventions have implications in the perioperative period, and it is the responsibility of the anesthesiologist to be familiar with these guidelines.

Status of pediatric anesthesiology fellowship research education in the United States: a survey of fellowship program directors.

BACKGROUND: Currently, very little information is known regarding the research education of pediatric anesthesia fellows. OBJECTIVE: The main objective of the current investigation was to evaluate the status of research training in pediatric anesthesia fellowship programs in the United States. METHODS: Survey responses were solicited from forty-six pediatric anesthesia fellowship directors. Questions evaluated department demographic information, the extent of faculty research activity, research resources and research funding in the department, the characteristics of fellow research education and fellow research productivity, departmental support for fellow research, and perceived barriers to fellow research education. RESULTS: Thirty-six of forty-six fellowship directors responded to the survey, for a response rate of 78%. Eight of fourteen (57%) programs with a structured curriculum had more than 20% of graduating fellows publish a peer-reviewed manuscript compared with only five of twenty-two (23%) programs, which did not have a structured research curriculum (P = 0.03). While the majority of program directors (thirty of thirty-six (83%)) did not think that fellows are adequately trained to pursue research activities, only a minority of program directors (7 of 36 (19%)) thought that an extra year of fellowship dedicated to research should become a requirement. CONCLUSION: Structured research curriculum is associated with increased research productivity during pediatric anesthesia fellowship. Important barriers to fellows' research education include high clinical demands and lack of research time for faculty. Despite acknowledging the poor research education, a small minority of fellowship directors supports the addition of an extra year exclusively dedicated to research.

Prescription patterns of pain medicine physicians.

OBJECTIVES: Our study surveyed physician members of 3 American pain societies to determine prescription patterns and whether these practices reflect current expert opinion. METHODS: We sent 3 mailings to 2938 physicians from January 2010 to January 2011. The questionnaire contained 49 questions on topics related to opioids, antidepressants, anticonvulsants, and preferences for the different pain syndromes. RESULTS: A total of 474 physicians responded, representing a 16% return. Seventy-two percent ask patients to sign an opioid agreement, 59% order random urine drug testing, 13% wait until the dose of methadone is between 100 and 150 mg before converting the drug to another opioid, and 85% do not think there is a maximum dose of opioids with respect to driving. Most responders prescribe codeine to Caucasians and Asians. While 42% stated that the maximum daily dose of acetaminophen is 3000 mg, 75% would decrease the dose in patients who are moderate or heavy drinkers. Fifty-four percent do not order an ECG at all when prescribing tricyclic antidepressants. CONCLUSIONS: The responses pertaining to opioid agreements, urine drug testing, acetaminophen, and treatment for neuropathic pain are reassuring in that they prevent misuse and abuse of opioids, prevent acetaminophen-induced hepatotoxicity, and reflect evidence-based treatments. However, we identified gaps in knowledge, including the prescription of codeine in certain populations and the use of electrocardiogram in patients on antidepressants. Further education of physicians who treat chronic pain pharmacologically is warranted.

Factor VII levels and international normalized ratios in the early phase of warfarin therapy.

BACKGROUND: Factor VII is the most affected clotting factor during the early phase of warfarin therapy. An international normalized ratio (INR) of more than 1.4 is considered unsafe for epidural catheter placement or removal, according to the American Society of Regional Anesthesia and Pain Medicine. The authors tested the hypothesis that factor VII activities would be consistent with safe removal of the epidural catheter on postoperative day (POD) 1 regardless of INR value. METHODS: Data from 121 patients who took warfarin after undergoing total joint surgery and had INRs and factor VII levels determined were reviewed. Patient characteristics and factor VII activities were compared between patients with INRs of more than 1.4 and those with INRs less than or equal to 1.4 on PODs 1, 2, and 3. RESULTS: Eleven patients had INRs of more than 1.4 on POD 1; their mean +/- SD factor VII activities were 60 +/- 28% (normal: 50-160%). On POD 2, 78 patients with INRs more than of 1.4 had factor VII activities of 32 +/- 15%, whereas on POD 3, 84 patients with INRs of more than 1.4 had factor VII activities of 44 +/- 19%. Variables included in the final multiple logistic regression model as predictors of an INR of more than 1.4 on POD 2 were warfarin dose on POD 1 and factor VII activity on POD 2. CONCLUSIONS: The range of factor VII activities in the patients with INRs of more than 1.4 within 12 h of warfarin therapy was compatible with adequate hemostasis. The authors found no evidence that epidural catheters should not be removed even with INRs up to 1.9, the highest INR on POD 1 noted in their study.

Ultrasound-assisted and evoked motor response stimulation of the deep peroneal nerve.

BACKGROUND: We performed an observational volunteer study to document an ultrasound-guided evoked motor response blockade of the deep peroneal nerve. METHODS: Sixteen volunteers had deep peroneal nerve blocks in each foot. After visualization of the artery and the deep peroneal nerve with an ultrasound, the nerve was stimulated with a nerve stimulator. Evoked motor responses and/or paresthesia were noted before injection of the local anesthetic. RESULTS: Any evoked motor response (extension of the toes or muscle contractions on the dorsum of the lateral aspect of the foot) or elicitation of paresthesia resulted in complete sensory blockade of the web between the big toe and second toe. CONCLUSIONS: Visualization of the deep peroneal nerve with ultrasound followed by elicitation of an evoked motor response, or paresthesia, predicts successful blockade of the deep peroneal nerve.

Comparison of the particle sizes of different steroids and the effect of dilution: a review of the relative neurotoxicities of the steroids.

BACKGROUND: Central nervous system injuries after transforaminal epidural steroid injections have been ascribed to occlusion of the blood vessels supplying the spinal cord and brain by the particulate steroid. METHODS: The authors compared the sizes of the particles of the steroids methylprednisolone acetate, triamcinolone acetonide, dexamethasone sodium phosphate, betamethasone sodium phosphate/betamethasone acetate (both Celestone Soluspan; Schering-Plough, Kenilworth, NJ, the commercial betamethasone; and betamethasone repository, a betamethasone preparation that can be ordered from a compounding company), and betamethasone sodium phosphate. Both undiluted and diluted samples were examined. The samples were examined with a laser scanning confocal microscope, and images were analyzed and measured. The particles were categorized (or tabulated) into groups: 0-20, 21-50, 51-1000, and greater than 1000 mu. Chi-square analyses, with Bonferroni correction, were used to compare the proportion of particles among the undiluted and diluted drug formulations. RESULTS: Dexamethasone and betamethasone sodium phosphate were pure liquid. The proportion of larger particles was significantly greater in the methylprednisolone and the compounded betamethasone preparations compared with the commercial betamethasone. There was no statistical difference between the commercial betamethasone and triamcinolone, although betamethasone had a smaller percentage of the larger particles. Increased dilution of the compounded betamethasone with lidocaine decreased the percentage of the larger particles, whereas increased dilution of methylprednisolone 80 mg/ml with saline increased the proportion of larger particles. CONCLUSION: Commercial betamethasone is the recommended preparation if a nonsoluble steroid is preferred. Dexamethasone is a nonparticulate steroid, but its routine use awaits further studies on its safety and efficacy.

Piriformis syndrome: anatomic considerations, a new injection technique, and a review of the literature.

BACKGROUND: Piriformis syndrome can be caused by anatomic abnormalities. The treatments of piriformis syndrome include the injection of steroid into the piriformis muscle and near the area of the sciatic nerve. These techniques use either fluoroscopy and muscle electromyography to identify the piriformis muscle or a nerve stimulator to stimulate the sciatic nerve. METHODS: The authors performed a cadaver study and noted anatomic variations of the piriformis muscle and sciatic nerve. To standardize their technique of injection, they also noted the distance from the lower border of the sacroiliac joint (SIJ) to the sciatic nerve. They retrospectively reviewed the charts of 19 patients who had received piriformis muscle injections, noting the site of needle insertion in terms of the distance from the lower border of the SIJ and the depth of needle insertion at which the motor response of the foot was elicited. The authors tabulated the response of the patients to the injection, any associated diagnoses, and previous treatments that these patients had before the injection. Finally, they reviewed the literature on piriformis syndrome, a rare cause of buttock pain and sciatica. RESULTS: In the cadavers, the distance from the lower border of the SIJ to the sciatic nerve was 2.9 +/- 0.6 (1.8-3.7) cm laterally and 0.7 +/- 0.7 (0.0-2.5) cm caudally. In 65 specimens, the sciatic nerve passed anterior and inferior to the piriformis. In one specimen, the muscle was bipartite and the two components of the sciatic nerve were separate, with the tibial nerve passing below the piriformis and the peroneal nerve passing between the two components of the muscle. In the patients who received the injections, the site of needle insertion was 1.5 +/- 0.8 (0.4-3.0) cm lateral and 1.2 +/- 0.6 (0.5-2.0) cm caudal to the lower border of the SIJ as seen on fluoroscopy. The needle was inserted at a depth of 9.2 +/- 1.5 (7.5-13.0) cm to stimulate the sciatic nerve. Patients had comorbid etiologies including herniated disc, failed back surgery syndrome, spinal stenosis, facet syndrome, SIJ dysfunction, and complex regional pain syndrome. Sixteen of the 19 patients responded to the injection, their improvements ranged from a few hours to 3 months. CONCLUSIONS: Anatomic abnormalities causing piriformis syndrome are rare. The technique used in the current study was successful in injecting the medications near the area of the sciatic nerve and into the piriformis muscle.