Navigated intraoperative ultrasound in neuro-oncology: volumetric accuracy and correlation with high-field MRI.

OBJECTIVE: The use of intraoperative techniques to detect residual tumors has recently become increasingly important. Intraoperative MRI has long been considered the gold standard; however, it is not widely used because of high equipment costs and long acquisition times. Consequently, real-time intraoperative ultrasound (ioUS), which is much less expensive than MRI, has gained popularity. The aim of the present study was to evaluate the capacity of ioUS to accurately determine the primary tumor volume and detect residual tumors. METHODS: A prospective study of adult patients who underwent surgery for intra-axial brain tumors between November 2017 and October 2020 was performed. Navigated intraoperative ultrasound (nioUS) of the brain was used to guide tumor resection and to detect the presence of residual disease. Both convex (5-8 MHz) and linear array (6-13 MHz) probes were used. Tumor volume and residual disease were measured with nioUS and compared with MR images. A linear regression model based on a machine learning pipeline and a Bland-Altman analysis were used to assess the accuracy of nioUS versus MRI. RESULTS: Eighty patients (35 females and 45 males) were included. The mean age was 58 years (range 25-80 years). A total of 88 lesions were evaluated; there were 64 (73%) gliomas, 19 (21.6%) metastases, and 5 (5.7%) other tumors, mostly located in the frontal (41%) and temporal (27%) lobes. Most of the tumors (75%) were perfectly visible on ioUS (grade 3, Mair grading system), except for those located in the insular lobe (grade 2). The regression model showed a nearly perfect correlation (R2 = 0.97, p < 0.001) between preoperative tumor volumes from both MRI and nioUS. Ultrasonographic visibility significantly influenced this correlation, which was stronger for highly visible (grade 3) tumors (p = 0.01). For residual tumors, the correlation between postoperative MRI and nioUS was weaker (R2 = 0.78, p < 0.001) but statistically significant. The Bland-Altman analysis showed minimal bias between the two techniques for pre- and postoperative scenarios, with statistically significant results for the preoperative concordance. CONCLUSIONS: The authors' findings show that most brain tumors are well delineated by nioUS and almost perfectly correlated with MRI-based measurements both pre- and postoperatively. These data support the hypothesis that nioUS is a reliable intraoperative technique that can be used for real-time monitoring of brain tumor resections and to perform volumetric analysis of residual disease.

Long-Term Results of Cortical Motor Stimulation for Neuropathic Peripheral and Central Pain: Real-World Evidence From Two Independent Centers.

BACKGROUND AND OBJECTIVES: Cortical motor stimulation (CMS) is used to modulate neuropathic pain. The literature supports its use; however, short follow-up studies might overestimate its real effect. This study brings real-world evidence from two independent centers about CMS methodology and its long-term outcomes. METHODS: Patients with chronic refractory neuropathic pain were implanted with CMS. The International Classification of Headache Disorders 3rd Edition was used to classify craniofacial pain and the Douleur Neuropathique en 4 Questions Scale score to explore its neuropathic nature. Demographics and clinical and surgical data were collected. Pain intensity at 6, 12, and 24 months and last follow-up was registered. Numeric rating scale reduction of ≥50% was considered a good response. The Clinical Global Impression of Change scale was used to report patient satisfaction. RESULTS: Twelve males (38.7%) and 19 females (61.3%) with a mean age of 55.8 years (±11.9) were analyzed. Nineteen (61.5%) were diagnosed from painful trigeminal neuropathy (PTN), and seven (22.5%) from central poststroke pain. The mean follow-up was 51 months (±23). At 6 months, 42% (13/31) of the patients were responders, all of them being PTN (13/19; 68.4%). At last follow-up, only 35% (11/31) remained responders (11/19 PTN; 58%). At last follow-up, the global Numeric rating scale reduction was 34% ( P = .0001). The Clinical Global Impression of Change scale punctuated 2.39 (±0.94) after 3 months from the surgery and 2.95 (±1.32) at last follow-up ( P = .0079). Signs of suspicious placebo effect were appreciated in around 40% of the nonresponders. CONCLUSION: CMS might show long-term efficacy for neuropathic pain syndromes, with the effect on PTN being more robust in the long term. Multicentric clinical trials are needed to confirm the efficacy of this therapy for this and other conditions.

Response and Safety Outcomes in Treatment-Resistant Depression After Subcallosal Cingulate Gyrus Deep Brain Stimulation: Long-term Follow-up Study.

Objective: To replicate previous findings and to investigate related clinical factors of long-term benefits and safety of subcallosal cingulate gyrus deep brain stimulation (SCG-DBS) for treatment-resistant depression (TRD).Methods: Sixteen patients with TRD (with either major depressive disorder or bipolar disorder, DSM-IV and DSM-5 criteria) receiving chronic SCG-DBS were followed for up to 11 years (January 2008 to June 2019). Demographic, clinical, and functioning data were collected pre-surgery and during the follow-up. Response was defined as a ≥ 50% decrease from baseline in the 17-item Hamilton Depression Rating Scale (HAM-D17) score, and remission was defined as ≤ 7 in the HAM-D17 score. The Illness Density Index (IDI) was used as a longitudinal measure of treatment effects. Survival analyses were performed for response outcomes and relapses.Results: Depressive symptoms were significantly decreased over time (F = 2.37; P = .04). Response and remission rates were 75% and 62.5% at individual endpoint. Based on Kaplan-Meier curve analysis, 55% of patients reached remission in 139 days. IDI curves showed sustained clinical improvements as measured with HAM-D17 and Clinical Global Impression and sustained functioning improvement as measured with Global Assessment of Functioning scores. The procedure was generally safe and well tolerated (122 adverse events across 81 patient-years, of which 25 were related to SCG-DBS). Two patients committed suicide long after surgery.Conclusions: SCG-DBS produced a robust and protracted improvement in most patients, which reinforces the possibility that SCG-DBS could be an alternative for patients with treatment-resistant unipolar or bipolar depression. Identification of clinical and neurobiological response predictors should guide the continuation of DBS for TRD, to obtain its indication soon.

Long-Term Results of Deep Brain Stimulation for Treatment-Resistant Depression: Outcome Analysis and Correlation With Lead Position and Electrical Parameters.

BACKGROUND: Long-term efficacy and mechanisms of action of deep brain stimulation (DBS) for treatment-resistant depression (TRD) are under investigation. OBJECTIVE: To compare long-term outcomes with active electrode's coordinates and its electrical parameters in patients with TRD treated with DBS in the subgenual cingulate gyrus (SCG-DBS). METHODS: Seventeen patients with TRD underwent SCG-DBS. Demographic and baseline characteristics were recorded. The 17-item Hamilton Depression Rating Scale was used to measure the response to the therapy. The anterior commissure-posterior commissure coordinates of the active contacts and the total electrical energy delivered were calculated and correlated with clinical outcomes. Patient-specific tractographic analysis was performed to identify the modulated pathways in responders. RESULTS: Twelve women (70.6%) and 5 men (29.4%) with a median age of 48 yr (34-70 years) were included. Along the 5-year follow-up, 3 main clinical trajectories were observed according to symptom's improvement: great responders (≥80%), medium responders (≥50%-79%), and poor responders (<50%). Active contacts' coordinates and total electrical energy delivered showed no correlation with clinical outcomes. Brodmann area 10 medial was the most frequently stimulated area and the forceps minor, the most frequently modulated tract. CONCLUSION: SCG-DBS for TRD is clearly effective in some patients. Active contacts' coordinates were highly variable within the region and, like electrical parameters, did not seem to correlate with clinical outcomes. In the current series, Brodmann area 10 medial and the forceps minor were the most frequently targeted area and modulated pathway, respectively.

Occipital nerve stimulation and deep brain stimulation for refractory cluster headache: a prospective analysis of efficacy over time.

OBJECTIVE: Occipital nerve stimulation (ONS) and deep brain stimulation (DBS) are widely used surgical treatments for chronic refractory cluster headache (CH). However, there is little literature regarding long-term follow-up of these treatments. METHODS: The authors describe two prospective cohorts of patients with refractory CH treated with ONS and DBS and compare preoperative to postoperative status at 6 and 12 months after the surgery and at final follow-up. Efficacy analysis using objective and subjective variables is reported, as well as medication reduction and complications. RESULTS: The ONS group consisted of 13 men and 4 women, with a median age of 44 years (range 31-61 years). The median number of attacks per week (NAw) before surgery was 28 (range 7-70), and the median follow-up duration was 48 months. The DBS group comprised 5 men and 2 women, with a median age of 50 years (range 29-64 years). The median NAw before surgery was 56 (range 14-140), and the median follow-up was 36 months. The NAw and visual analog scale score were significantly reduced for the ONS and DBS groups after surgery. However, while all the patients from the DBS group were considered responders at final follow-up, with more than 85% being satisfied with the treatment, approximately 29% of initial responders to ONS became resistant by the final follow-up (p = 0.0253). CONCLUSIONS: ONS is initially effective as a treatment for refractory CH, although a trend toward loss of efficacy was observed. No clear predictors of good clinical response were found in the present study. Conversely, DBS appears to be effective and provide a more stable clinical response over time with an acceptable rate of surgical complications.

Long-Term Safety and Performance of a Polymeric Clamplike Cranial Fixation System.

OBJECTIVE: After a craniotomy procedure to access the brain, neurosurgeons have several options to fix the bone flap to the skull. The aim of this study was to assess if a polymeric clamplike fixation system (Cranial LOOP) is a safe and reliable system that maintains over time an appropriate alignment of the bone flap. METHODS: This is an observational, retrospective, case series study of 60 patients who underwent a craniotomy and were subject to cranial bone flap fixation with the Cranial LOOP fixation system. Baseline clinical parameters, surgical variables, medical records, and all postoperative medical images available were reviewed to assess the bone flap alignment and potential adverse events. RESULTS: A total of 182 Cranial LOOPs were implanted in the 60 patients (56.01 ± 20.21 years, 55% women) included in the study. The cranial fixation system maintained a good bone flap alignment in 95% of the patients studied immediately after surgery and in up to 96.7% of them at the end of follow-up. No intraoperative complications were reported. An ulcer potentially related to a device was detected, which was solved without the need for device removal. No artifacts were observed in any of the 219 medical images analyzed. CONCLUSIONS: Cranial LOOP is a safe and reliable postoperative long-term cranial bone flap fixation system. This device can fix the bone flap after a wide range of craniotomy procedures, performed in multiple locations, and provides good bone flap alignment. Cranial LOOP does not interfere in patient follow-up through medical imaging.

Efficacy of Sphenopalatine Ganglion Radiofrequency in Refractory Chronic Cluster Headache.

BACKGROUND: In the literature, there are only short series of radiofrequency of the sphenopalatine ganglion (SPG) to treat chronic refractory cluster headache (CCHr) with variable results. Furthermore, there is no consensus on which methodology to use: radiofrequency ablation (RFA) or pulsed radiofrequency (PRF). METHODS: We conducted a prospective analysis of 37 patients with CCHr who underwent RFA or PRF of the SPG in our center between 2004 and 2015. RESULTS: The mean age of the patients was 40 years (range, 26-59 years). PRF was performed in 24 patients, and RFA was performed in 13 patients. A total of 5 patients (13.5%) experienced complete clinical relief of both pain and parasympathetic symptoms, 21 patients (56.8%) had partial and transient relief, and 11 patients (29.7%) did not improve. There was no evidence of significant superiority of one radiofrequency modality over the other (P = 0.48). There were no complications associated with the technique. The passage of time tended to decrease the efficacy of both techniques (P < 0.001). The mean follow-up was 68.1 months (range, 15-148 months). To our knowledge, this is the series with the largest number of patients and the longest follow-up period published in the literature. CONCLUSIONS: Radiofrequency of the SPG is a safe, fast, and partially effective method for the treatment of CCHr. Given its low rate of complications and its low economic cost, we think it should be one of the first invasive treatment options, prior to techniques with greater morbidity and mortality, such as neuromodulation.

[Complications related with implanted devices in patients with Parkinson's disease treated with deep brain stimulation. A study of a series of 124 patients over a period of 16 years]. / Complicaciones relacionadas con dispositivos implantados en pacientes con enfermedad de Parkinson tratados con estimulacion cerebral profunda. Estudio de una serie de 124 pacientes durante 16 años.

INTRODUCTION: Establishing protocols of the best candidates for deep brain stimulation in patients with Parkinson's disease and a greater knowledge of the technique have increased its safety profile. Yet, the complications related with implanted devices still occur with a far-from-negligible frequency and have both an economic and clinical impact. AIM: From a broad series of patients undergoing deep brain stimulation included consecutively for the treatment of their Parkinson's disease, data concerning the complications related with implanted devices were gathered and compared with those in the literature. PATIENTS AND METHODS: Altogether 124 patients with a total of 242 implanted electrodes and 252 generator replacements were included in the study. Mean follow-up time was 8.4 years (range: 3-16 years). Data on all the complications related with implanted devices were collected retrospectively. RESULTS: Findings showed that 23 implanted device-related complications occurred (17.7% of the patients): 12 (9.6%) had culture-positive ulcers, five (4%) had culture-negative ulcers, four (3.2%) were left with infections following generator replacement, one (0.8%) had a generator malfunction, and electrode migration took place in one (0.8%). Significant differences were observed as regards the effectiveness of the treatment involving surgical revision of the ulcers, which suggests that the culture-negative ulcers responded to the surgical revision better than the culture-positive ulcers (80% healing versus 16.6%; p = 0.028). CONCLUSIONS: The results observed in the series were comparable to those in the existing literature. The presence of culture-positivity in the ulcers is a factor forecasting surgical revision.

TITLE: Complicaciones relacionadas con dispositivos implantados en pacientes con enfermedad de Parkinson tratados con estimulacion cerebral profunda. Estudio de una serie de 124 pacientes durante 16 años.Introduccion. La protocolizacion de los mejores candidatos para la estimulacion cerebral profunda en pacientes con enfermedad de Parkinson y el mayor conocimiento de la tecnica han aumentado su perfil de seguridad. Sin embargo, las complicaciones relacionadas con los dispositivos implantados siguen teniendo una frecuencia no menospreciable y presentan un impacto tanto clinico como economico. Objetivo. En una serie amplia de pacientes con estimulacion cerebral profunda incluidos consecutivamente para el tratamiento de su enfermedad de Parkinson, se recogieron las complicaciones relacionas con los dispositivos implantados y se compararon con la bibliografia. Pacientes y metodos. Se incluyeron en el estudio 124 pacientes con un total de 242 electrodos implantados y 252 recambios de generador. Seguimiento medio de 8,4 años (rango: 3-16 años). Se recogieron de forma retrospectiva todas las complicaciones relacionadas con los dispositivos implantados. Resultados. Se produjeron 23 complicaciones relacionadas con los dispositivos implantados (el 17,7% de los pacientes): 12 (9,6%) ulceras con cultivo positivo, cinco (4%) ulceras con cultivo negativo, cuatro (3,2%) infecciones tras recambio de generador, una (0,8%) malfuncion de generador y una (0,8%) migracion del electrodo. Se observaron diferencias significativas respecto a la efectividad del tratamiento de la revision quirurgica de las ulceras, lo que indica que las ulceras con cultivo negativo respondieron mejor que las ulceras con cultivo positivo a la revision quirurgica (80% frente a 16,6% de curacion; p = 0,028). Conclusiones. Se observan en la serie unos resultados comparables a la bibliografia existente. La presencia de positividad en el cultivo de las ulceras constituye un factor pronostico a la revision quirurgica.

Complicaciones relacionadas con dispositivos implantados en pacientes con enfermedad de Parkinson tratados con estimulación cerebral profunda. Estudio de una serie de 124 pacientes durante 16 años / Complications related with implanted devices in patients with Parkinson’s disease treated with deep brain stimulation. A study of a series of 124 patients over a period of 16 years

Introducción. La protocolización de los mejores candidatos para la estimulación cerebral profunda en pacientes con enfermedad de Parkinson y el mayor conocimiento de la técnica han aumentado su perfil de seguridad. Sin embargo, las complicaciones relacionadas con los dispositivos implantados siguen teniendo una frecuencia no menospreciable y presentan un impacto tanto clínico como económico. Objetivo. En una serie amplia de pacientes con estimulación cerebral profunda incluidos consecutivamente para el tratamiento de su enfermedad de Parkinson, se recogieron las complicaciones relacionas con los dispositivos implantados y se compararon con la bibliografía. Pacientes y métodos. Se incluyeron en el estudio 124 pacientes con un total de 242 electrodos implantados y 252 recambios de generador. Seguimiento medio de 8,4 años (rango: 3-16 años). Se recogieron de forma retrospectiva todas las complicaciones relacionadas con los dispositivos implantados. Resultados. Se produjeron 23 complicaciones relacionadas con los dispositivos implantados (el 17,7% de los pacientes): 12 (9,6%) úlceras con cultivo positivo, cinco (4%) úlceras con cultivo negativo, cuatro (3,2%) infecciones tras recambio de generador, una (0,8%) malfunción de generador y una (0,8%) migración del electrodo. Se observaron diferencias significativas respecto a la efectividad del tratamiento de la revisión quirúrgica de las úlceras, lo que indica que las úlceras con cultivo negativo respondieron mejor que las úlceras con cultivo positivo a la revisión quirúrgica (80% frente a 16,6% de curación; p = 0,028). Conclusiones. Se observan en la serie unos resultados comparables a la bibliografía existente. La presencia de positividad en el cultivo de las úlceras constituye un factor pronóstico a la revisión quirúrgica (AU)

Introduction. Establishing protocols of the best candidates for deep brain stimulation in patients with Parkinson’s disease and a greater knowledge of the technique have increased its safety profile. Yet, the complications related with implanted evices still occur with a far-from-negligible frequency and have both an economic and clinical impact. Aim. From a broad series of patients undergoing deep brain stimulation included consecutively for the treatment of their Parkinson’s disease, data concerning the complications related with implanted devices were gathered and compared with those in the literature. Patients and methods. Altogether 124 patients with a total of 242 implanted electrodes and 252 generator replacements were included in the study. Mean follow-up time was 8.4 years (range: 3-16 years). Data on all the complications related with implanted devices were collected retrospectively. Results. Findings showed that 23 implanted device-related complications occurred (17.7% of the patients): 12 (9.6%) had culture-positive ulcers, five (4%) had culture-negative ulcers, four (3.2%) were left with infections following generator replacement, one (0.8%) had a generator malfunction, and electrode migration took place in one (0.8%). Significant differences were observed as regards the effectiveness of the treatment involving surgical revision of the ulcers, which suggests that the culture-negative ulcers responded to the surgical revision better than the culture-positive ulcers (80% healing versus 16.6%; p = 0.028). Conclusions. The results observed in the series were comparable to those in the existing literature. The presence of culturepositivity in the ulcers is a factor forecasting surgical revision (AU)

Fibrosarcoma epitelioide esclerosante a nivel paraespinal. Caso clínico y revisión de la literatura / Sclerosing epithelioid fibrosarcoma of the paravertebral column. Case report and literature review

El fibrosarcoma epitelioide esclerosante (SEF) es una variante poco frecuente de fibrosarcoma de bajo grado con características histológicas e inmunohistoquímicas bien definidas, caracterizado por su mal pronóstico. Presentamos un caso de SEF a nivel paraespinal en un paciente varón de 49 años con un tumor que se extiende hacia el foramen L4-L5 e invade la raíz L5. La histología de la pieza quirúrgica y el estudio inmunohistoquímico fueron compatibles con SEF. Este caso es particularmente inusual por su origen a nivel paraespinal e ilustra, a pesar de su bajo grado, el potencial de malignidad del SEF (AU)

Sclerosing epithelioid fibrosarcoma (SEF) is a rare variant of low-grade fibrosarcoma, with specific histological and immunohistochemical features and a poor prognosis. We report a case of SEF of the paravertebral column in a 49-year old male who presented a paraspinal mass with extension into the L4-L5 neural foramen and invasion of the L5 nerve root. Histology of the tumourectomy specimen and its immunohistochemical study led to the diagnosis of SEF. This case was particularly unusual due to its paravertebral column location and, despite its low grade, illustrates the malignant potential of SEF (AU)

[Sclerosing epithelioid fibrosarcoma of the paravertebral column. Case report and literature review]. / Fibrosarcoma epitelioide esclerosante a nivel paraespinal. Caso clínico y revisión de la literatura.

Sclerosing epithelioid fibrosarcoma (SEF) is a rare variant of low-grade fibrosarcoma, with specific histological and immunohistochemical features and a poor prognosis. We report a case of SEF of the paravertebral column in a 49-year old male who presented a paraspinal mass with extension into the L4-L5 neural foramen and invasion of the L5 nerve root. Histology of the tumourectomy specimen and its immunohistochemical study led to the diagnosis of SEF. This case was particularly unusual due to its paravertebral column location and, despite its low grade, illustrates the malignant potential of SEF.

Estimulación del nervio occipital para la cefalea en racimos refractaria al tratamiento farmacológico / Stimulation of the occipital nerve in the treatment of drug-resistant cluster headache

Objetivo. Evaluar la utilidad de la estimulación del nervio occipital en el tratamiento de la cefalea en racimos crónica refractaria al tratamiento farmacológico. Pacientes y métodos. Serie prospectiva de cuatro pacientes, tres varones y una mujer. La edad media es de 42 años. Hay historia de cefalea en racimos de entre 1 y 16 años, con mal control de las crisis mediante tratamiento farmacológico. En todos los casos se han colocado percutáneamente electrodos octopolares en ambas regiones occipitales. Se ha realizado un seguimiento de seis meses. Resultados. A los seis meses se obtuvo una reducción de la frecuencia de las crisis del 56% (rango: 25-95%), una disminución en la intensidad del 48,8% (rango: 20-60%) y una disminución de la duración de un 63,8% (rango: 0-88,8%), sin observarse empeoramiento ni progresión de la enfermedad en ningún caso. La mejoría en la calidad de vida respecto a la prequirúrgica fue de un 15,4% (rango: 6-31,5%) en el cuestionario de salud SF-36. Excepto en un caso, se objetivó una reducción significativa en la cantidad y la dosis de fármacos requeridos respecto al tratamiento prequirúrgico. No se han detectado complicaciones postoperatorias. Todos los pacientes aconsejarían el procedimiento como opción terapéutica. Conclusiones. La estimulación del nervio occipital puede ser una alternativa terapéutica segura y efectiva en el tratamiento de la cefalea en racimos crónica refractaria al tratamiento farmacológico. Sin embargo, son necesarios más estudios para valorar la efectividad de la técnica en un mayor número de pacientes y los resultados a largo plazo (AU)

Aim. To evaluate the occipital nerve stimulation therapy in as a treatment for drug-resistant cluster headache. Patients and methods. Prospective study of four patients, three males and one female. Mean age of 42 years. Patients complained of a cluster headache lasting between one and 16 years, with suboptimal control of the attacks with medication. In all cases octopolar electrodes were placed percutaneously in the occipital region bilaterally. Follow-up of 6 months. Results. At 6 months, there was a 56% (range: 25-95%) reduction in the frequency, a 48.8% (range: 20-60%) decrease in the intensity and a 63.8% (range: 0-88.8%) reduction in the duration of the attacks. Worsening or progression of the illness was not observed in any case. All patients referred a 15.4% (range: 6-31.5%) improvement in their quality of life compared to their previous basal situation in SF-36. In all cases but one there was a significant reduction in the amount and dosage of medication required. Postoperative complications were not observed. All patients would recommend the procedure. Conclusions. Occipital nerve stimulation may be considered a safe and effective therapeutic option in the drug-resistant cluster headache. However, studies with more patients and a longer follow-up are required to evaluate the efficacy of the technique (AU)

[Stimulation of the occipital nerve in the treatment of drug-resistant cluster headache]. / Estimulación del nervio occipital para la cefalea en racimos refractaria al tratamiento farmacológico.

AIM: To evaluate the occipital nerve stimulation therapy in as a treatment for drug-resistant cluster headache. PATIENTS AND METHODS: Prospective study of four patients, three males and one female. Mean age of 42 years. Patients complained of a cluster headache lasting between one and 16 years, with suboptimal control of the attacks with medication. In all cases octopolar electrodes were placed percutaneously in the occipital region bilaterally. Follow-up of 6 months. RESULTS: At 6 months, there was a 56% (range: 25-95%) reduction in the frequency, a 48.8% (range: 20-60%) decrease in the intensity and a 63.8% (range: 0-88.8%) reduction in the duration of the attacks. Worsening or progression of the illness was not observed in any case. All patients referred a 15.4% (range: 6-31.5%) improvement in their quality of life compared to their previous basal situation in SF-36. In all cases but one there was a significant reduction in the amount and dosage of medication required. Postoperative complications were not observed. All patients would recommend the procedure. CONCLUSIONS: Occipital nerve stimulation may be considered a safe and effective therapeutic option in the drug-resistant cluster headache. However, studies with more patients and a longer follow-up are required to evaluate the efficacy of the technique.