Multidisciplinary Surgical Approach Using Augmented Reality Preplanning for Resection of Giant Thoracic Schwannoma With Robotic-Assisted Thoracoscopic Mobilization

BACKGROUND AND IMPORTANCE

In adults, primary spinal cord tumors account for 5% of all primary tumors of the central nervous system, with schwannomas making up about 74% of all nerve sheath tumors. Thoracic schwannomas can pose a threat to neurovasculature, presenting a significant challenge to safe and complete surgical resection. For patients presenting with complex pathologies including tumors, a dual surgeon approach may be used to optimize patient care and improve outcomes.

CLINICAL PRESENTATION

A 73-year-old female previously diagnosed with a nerve sheath tumor of the fourth thoracic vertebra presented with significant thoracic pain and a history of falls. Imaging showed that the tumor had doubled in size ranging from T3 to T5. Augmented reality volumetric rendering was used to clarify anatomic relationships of the mass for perioperative evaluation and decision-making. A dual surgeon approach was used for complete resection. First, a ventrolateral left video-assisted thoracoscopic surgery was performed with robotic assistance followed by a posterior tumor resection and thoracic restabilization. The patient did well postoperatively.

CONCLUSION

Although surgical treatment of large thoracic dumbbell tumors presents a myriad of risks, perioperative evaluation with augmented reality, new robotic surgical techniques, and a dual surgeon approach can be implemented to mitigate these risks.

A guide to selecting upper thoracic versus lower thoracic uppermost instrumented vertebra in adult spinal deformity correction

PURPOSE

Operative treatment of adult spinal deformity (ASD) has been shown to improve patient health-related quality of life (HRQOL). Selection of the uppermost instrumented vertebra (UIV) in either the upper thoracic (UT) or lower thoracic (LT) spine is a pivotal decision with effects on operative and postoperative outcomes. This review overviews the multifaceted decision-making process for UIV selection in ASD correction.

METHODS

PubMed was queried for articles using the keywords "uppermost instrumented vertebra", "upper thoracic", "lower thoracic", and "adult spinal deformity".

RESULTS

Optimization of UIV selection may lead to superior deformity correction, better patient-reported outcomes, and lower risk of proximal junctional kyphosis (PJK) and failure (PJF). Patient alignment characteristics, including preoperative thoracic kyphosis, coronal deformity, and the magnitude of sagittal correction influence surgical decision-making when selecting a UIV, while comorbidities such as poor body mass index, osteoporosis, and neuromuscular pathology should also be taken in to account. Additionally, surgeon experience and resources available to the hospital may also play a role in this decision. Currently, it is incompletely understood whether postoperative HRQOLs, functional and radiographic outcomes, and complications after surgery differ between selection of the UIV in either the UT or LT spine.

CONCLUSION

The correct selection of the UIV in surgical planning is a challenging task, which requires attention to preoperative alignment, patient comorbidities, clinical characteristics, available resources, and surgeon-specific factors such as experience.

Bow Hunter Syndrome: An Illustrative Case and Operative Management

The differential for vertebrobasilar insufficiency is wide and can be caused by posterior circulation infarcts, steal-type phenomena, or other systemic causes. In the absence of imaging findings explaining symptomology, the utility of appropriate history gathering and dynamic angiography cannot be understated in identifying Bow Hunter's syndrome, a rare cause of dynamic vertebrobasilar insufficiency. We present a case of a 69-year-old man who complained of presyncope and severe dizziness when turning his head towards the right. On examination he had no radiculopathy but did have objective evidence of myelopathy. Computed tomography imaging and dynamic angiography demonstrated C3-C4 right uncovertebral joint hypertrophy and near complete stenosis of the right vertebral artery with dynamic head position towards the right. Given vertebrobasilar insufficiency and myelopathy, he was taken to the operating room for C3-C4 anterior cervical discectomy and fusion with vertebral artery decompression (Video 1). The patient provided consent for the procedure. Standard anterior cervical neck dissection was undertaken with additional platysmal undermining to facilitate exposure of the right uncovertebral joint and transverse processes. The vertebral artery was first decompressed above and below the area of most significant stenosis at the respective transverse foramina before the hypertrophied uncovertebral joint was removed. Next, discectomy and posterior osteophyte removal were completed in typical fashion followed by graft, plate, and screw placement. Postoperatively the patient had immediate resolution of symptoms and continued so at eight month follow-up. Imaging demonstrated return to normal caliber of the right vertebral artery and successful decompression.

Topical tranexamic acid (TXA) is non-inferior to intravenous TXA in adult spine surgery: a meta-analysis

Tranexamic acid (TXA) has long been utilized in spine surgery and can be administered through intravenous (IV) and topical routes. Although, topical and IV administration of TXA are both effective in decreasing blood loss during spine surgery, complications like deep vein thrombosis (DVT) and pulmonary embolism have been reported with the use of intravenous TXA (ivTXA). These potential complications may be mitigated through the use of topical TXA (tTXA). To assess optimal dosing protocols and efficacy of topical TXA in spine surgery, Embase, Ovid-MEDLINE, Scopus, Cochrane, and clinicaltrials.gov were queried for original research on the use of tTXA in adult patients undergoing spine surgery. Data parameters analyzed included blood loss, transfusion rate, thromboembolic, and other complications. Data was synthesized and confidence evaluated according to the Grades of Recommendation, Assessment, Development, and Evaluation approach. Nineteen studies were included in the final analysis with 2197 patients. Of the 18 published studies, 9 (50%) displayed high levels of evidence. Topical TXA showed a trend towards a lower risk of transfusion and complications. Protocols that used 1g tTXA showed a significantly reduced risk for transfusion when compared to controls (risk ratio -1.05, 95% CI (-1.62, -0.48); P = 0.94, I2 = 0%). Complications associated with tTXA included DVTs and wound infections. Topical TXA was non-inferior to intravenous TXA with similar efficacy and complication profiles for bleeding control in spine surgery; however, more studies are needed to discern benefits and risks.

Art and Neurosurgery: The Importance of Medical Illustration

Art in neurosurgery has been a critical part of the discipline for centuries. Numerous cultures, such as ancient India, China, and Egypt, and more contemporary scientists, such as Leonardo da Vinci, Max Brödel, and Norman Dott, have significantly contributed to medical illustration. Today, advancements in three-dimensional technology have allowed for the creation of detailed neuroanatomy models for surgical planning and education. Medical illustrations are also used for research and outcome documentation as they help visualize anatomy and surgical procedures. Its use in education, surgical planning, and navigation remains integral to the advancement of neurosurgery. This review demonstrates the invaluable contribution of art in neurosurgery and how it has enabled continuous progress in the field.

Exploring the 'January effect' at a university hospital in Pakistan: a retrospective cohort study investigating the impact of trainee turnover on patient care quality outcomes

OBJECTIVE

There are reports of a potential rise in a teaching hospital's morbidity and mortality rates during the trainee turnover period, i.e., with the induction of new residents and house staffs, and the changeover of clinical teams. The published literature displays mixed reports on this topic with lack of reproducible observations. The current study was conducted to explore existence of any such phenomenon (January effect) in Pakistan.

METHODS

This retrospective cohort study was conducted at Aga Khan University Hospital, Karachi, Pakistan. Five-year (2013-2018) record of all the patients in all age groups related to these outcomes was retrieved and recorded in specifically designed questionnaire. Different outcome measures were used as indicators of patient care and change in these outcomes at the time of new induction was related to possible January effect.

RESULTS

During the five-year study period, more than 1100 new trainees were inducted into the post graduate medical education program (average of 237 per year) with more than 22,000 inpatient admissions (average of 45,469 per year). Some patterns were observed in frequencies of surgical site infections, medication errors, sentinel events, patient complaints, and adverse drug reactions. However, these were not consistently reproducible and could not be directly attributed to the trainee turnover. All other indicators did not show any pattern and were considered inconclusive. No effect of overlap was observed.

CONCLUSIONS

Inconsistency in the patient care quality indicators do not favor existence of January effect in our study. Further research is recommended to establish our results.

Evaluating the state of non-invasive imaging biomarkers for traumatic brain injury

Non-invasive imaging biomarkers are useful for prognostication in patients with traumatic brain injury (TBI) at high risk for morbidity with invasive procedures. The authors present findings from a scoping review discussing the pertinent biomarkers. Embase, Ovid-MEDLINE, and Scopus were queried for original research on imaging biomarkers for prognostication of TBI in adult patients. Two reviewers independently screened articles, extracted data, and evaluated risk of bias. Data was synthesized and confidence evaluated with the linked evidence according to the Grades of Recommendation, Assessment, Development, and Evaluation (GRADE) approach. Our search yielded 3104 unique citations, 44 of which were included in this review. Study populations varied in TBI severity, as defined by Glasgow Coma Scale (GCS), including: mild (n=9), mild and moderate (n=3), moderate and severe (n=7), severe (n=6), and all GCS scores (n=17). Diverse imaging modalities were used for prognostication, predominantly computed tomography (CT) only (n=11), magnetic resonance imaging (MRI) only (n=9), and diffusion tensor imaging (DTI) (N=9). The biomarkers included diffusion coefficient mapping, metabolic characteristics, optic nerve sheath diameter, T1-weighted signal changes, cortical cerebral blood flow, axial versus extra-axial lesions, T2-weighted gradient versus spin echo, translocator protein levels, and trauma imaging of brainstem areas. The majority (93%) of studies identified that the imaging biomarker of interest had a statistically significant prognostic value; however, these are based on a very low to low level of quality of evidence. No study directly compared the effects on specific TBI treatments on the temporal course of imaging biomarkers. The current literature is insufficient to make a strong recommendation about a preferred imaging biomarker for TBI, especially considering GRADE criteria revealing low quality of evidence. Rigorous prospective research of imaging biomarkers of TBI is warranted to improve the understanding of TBI severity.

Spatial Computing for preoperative planning and postoperative evaluation of single-position lateral approaches in spinal revision surgery

Spatial computing (SC) in a surgical context offers reconstructed interactive four-dimensional models of radiological imaging. Preoperative and postoperative assessment with SC can offer more insight into personalized surgical approaches. Spine surgery has benefitted from the use of perioperative SC assessment. Herein, we describe the use of SC to perform a perioperative assessment of a revision spinal deformity surgery. A 79-year-old wheelchair-bound male presented to the neurosurgery clinic with a history of chronic lumbar pain associated with bilateral lower extremity weakness. His surgical history is significant for an L2-L5 lumbar decompression with posterior fixation 1 year prior. On examination, there were signs of thoracic myelopathy. Imaging revealed his previous instrumentation, pseudoarthrosis, and cord compression. We perform a two-staged operation to address the thoracic spinal cord compression and myelopathy, pseudoarthrosis, and malalignment with a lack of global spinal harmony. His imaging is driven by a spatial computing and SC environment and offers support for the diagnosis of his L2-3 and L4-5 pseudoarthrosis on the reconstructed SC-based computed tomography scan. SC enabled the assessment of the configuration of the psoas muscle and course of critical neurovascular structures in addition to graft sizing, trajectory and approach, evaluation of the configuration and durability of the anterior longitudinal ligament, and the overlying abdominal viscera. SC increases the familiarity of the patient's specific anatomy and enhances perioperative assessment. As such, SC can be used to preoperatively plan for spinal revision surgery.

Removal of a Floating and Migrated Plate Screw in a Patient with a Failed Anterior Cervical Discectomy and Fusion (ACDF)

INTRODUCTION

Anterior cervical discectomy and fusion (ACDF) is a commonly performed procedure for degenerative spine disease affecting the cervical spine. Rare complications of ACDF surgery include hardware failure, in the form of screw loosening and migration, or rod breakage. Herein, we present a case where we removed a migrated screw lodged in the esophagus from a patient with a failed anterior cervical fusion.

OBJECTIVE

To perform a complex lateral approach to remove a migrated screw.

METHODS

The previous ACDF incision was reopened and exposure was gained under the guidance of a head and neck surgeon. Longus coli were mobilized off the spine bilaterally with electrocautery. Following exposure, the locking mechanism and screws were removed from C4-C7 bilaterally and the plate was removed. After significant lateral paraspinal dissection, which was performed lateral to the C4 and C5 transverse processes, the screw was found lodged in the longitudinal muscle of the esophageal wall and excised with the use of a 15-blade. The integrity of the esophageal mucosa and submucosa was maintained and subsequently checked with rigid esophagoscopy. Fluoroscopy was utilized to confirm that all hardware was removed, with the exception of the anterior cages.

RESULTS

The mobile right plate screw which migrated to the contralateral side was successfully removed with an uneventful postoperative course.

CONCLUSION

Failure of an ACDF carries a risk of distal screw migration, which may be asymptomatic even if the screw is lodged in the esophagus. A complex lateral exposure can be utilized to retrieve the migrated screw.

Craniotomy or Craniectomy for Acute Subdural Hematoma? Difference in Patient Characteristics and Outcomes at a Tertiary Care Hospital

Objective  This article compares the outcomes of patients with traumatic acute subdural hemorrhage (SDH) managed either with craniotomy (CO) or with decompressive craniectomy (DC). Methods  In this single-center, retrospective analysis we included all adult patients with acute traumatic SDH who were treated either using CO or DC. Sixteen-year hospital data was reviewed for patient demographics, injury details, and hospital course. Outcomes were noted in terms of intraoperative blood loss, intensive care unit stay, need for tracheostomy, post-surgery Glasgow Coma Score (GCS; calculated immediately after surgery), delayed GCS (DGCS; calculated 1 week after surgery), and delayed Glasgow Outcome Score (DGOS) after 6 months of surgery. Postoperative complications were noted during hospital stay, while mortality was noted within 6 months of surgery for each patient. Results  Patients who underwent DC were younger (mean age 34.4 ± 16.8 years vs. 42.4 ± 19.9 years in the CO group) ( p  = 0.006). Patients who underwent DC also had worst degree of traumatic brain injury as per Marshall grade (62.4% patients with Marshall grade 4 in the DC group vs. only 41.2% patients in the CO group) ( p  = 0.037). Mean size of hematoma was 23.8 ± 24.6 mm in the DC group versus 11.3 ± 8.2 mm in the CO group ( p  = 0.001). Mean postop GCS was lower in the DC group; 8.0 ± 4 versus 10.8 ± 4 in the CO group ( p  < 0.001). However, there was no significant difference in DGCS and DGOS between the DC and CO groups ( p  = 0.76 and 0.90, respectively). Mortality rate was 24 (30.8%) in the DC group versus 18 (20.7%) in the CO group ( p  = 0.14). Conclusion  The patients who underwent DC were younger, had larger size hematoma, and poor Marshall grade. We did not find any significant difference in the outcomes of CO and DC for management of subdural hematoma.

First American College of Surgeons National Surgical Quality Improvement Program Report from a Low-Middle-Income Country: A 1-Year Outcome Analysis of Neurosurgical Cases

BACKGROUND

Low-middle-income countries (LMICs) share a substantial proportion of global surgical complications. This is compounded by the seemingly deficient documentation of postsurgical complications and the lack of a national average for comparison. In this context, the implementation of the American College of Surgeons (ACS) National Surgical Quality Improvement Program (NSQIP) that compares hospital performance based on postsurgical complication data provided by a wide array of centers, could be a major initiative in a resource-challenged setting. Implementation of the NSQIP has provenly mitigated postoperative morbidity and mortality across many centers all over the world. To our knowledge, this report is the first from an LMIC to report its postoperative neurosurgical complications in comparison with international benchmarks.

METHODS

Our hospital joined the NSQIP in 2019. Through a standardized ACS protocol, ACS-trained surgical clinical reviewers (SCRs) reviewed and extracted data from randomly assigned neurosurgical patients' medical records from preoperative to postoperative (30-day) data using validated, standardized data definitions. SCRs entered deidentified data in an online Health Insurance Portability and Accountability Act web-based secure platform. The validated data were then consigned to the ACS NSQIP head office in the United States where the data were analyzed and compared with similar data from other centers registered with the NSQIP. In this way, our hospital was rated for each of the variables related to postsurgical complications after both spinal and cranial procedures, and the results were sent back to us in the form of text, tables, and graphs.

RESULTS

Our initial report suggested a relatively higher odds ratio for sepsis and readmissions after spinal procedures at our hospital, and a similarly higher odds ratio for morbidity, sepsis, urinary tract infection, and surgical site infection for cranial procedures. For these variables, our hospital fell in the needs improvement category of the NSQIP. For the rest of the variables studied for both spinal and cranial procedures, the hospital fell in the as expected category of the NSQIP.

CONCLUSIONS

Implementation of the NSQIP is an important first step in creating a culture of transparency, safety, and quality. This is the first report of NSQIP implementation in an LMIC, and we have shown comparable results to developed countries.

Postdischarge 24/7 Hotline Service for Neurology and Neurosurgery Patients and 1-Year Impact on Readmission Rates, Unplanned Emergency Department Visits, and Patient Satisfaction

Objective

Telephone triage is a system in which trained nurses use standardized protocols to evaluate symptoms over the phone and determine the appropriate course of action.

Materials and Methods

We implemented a protocol for systematic follow up phone calls and telephonic triage to families of neurology and neurosurgery patients after discharge, primarily to improve care transition and to assess its impact on the ratio of visits in the emergency department, readmissions, and overall satisfaction of patients and families. The intervention comprised the implementation of nurse led telephone triage and postdischarge follow up phone calls. After implementing hotline services in mind and brain service line, a retrospective cohort study was conducted to evaluate the impact of hotline services on patient readmissions, emergency department visits, and overall satisfaction rate. We collected data of readmission rate and emergency visits of discharge patients in three periods a prehotline period, immediate posthotline period, and late posthotline period to make comparison. Patients discharged home from the neurology and neurosurgery services from January 2017 to September 2019 were provided with hotline number to call in case of any issue or query. These patients also received postdischarge follow up calls from hotline nurses. We initiated the hotline in October 2017.

Results

On analysis, we found a 25% decline in readmission rate in the immediate period of hotline followed by a further decline to 37.2% in the late period as compared to the prehotline period. Among discharge patients visiting the emergency department, we found a decline of 18.5% in the immediate posthotline period which further declined to 77.7% in the later phase as compared to the prehotline period.

Conclusion

A standardized telephone system and pathway can be an effective way to improve nurse-patient communication which can further improve health outcomes for many patients.

Management of symptomatic disc herniation in pregnancy: A case report and literature review

Background:

Lower back pain with radiculopathy due to a disc herniation occurs in about 0.01% of pregnant females. Surgical intervention is seldom required unless there is intractable pain, and for a significant neurological deficit. Further, the use of intraoperative ionizing radiation may adversely affect the developing fetus.

Case Description:

A 25-year-old female, 17-weeks pregnant, presented with right lower extremity sciatica due to a L4-5 unilateral disc herniation. She underwent a microdiscectomy that required just one intraoperative C-arm fluoroscopic image. Postoperatively, her leg pain resolved, and she delivered a healthy baby at term.

Conclusion:

Using single-image C-arm fluoroscopy in a pregnant female undergoing an emergent lumbar discectomy, employing as low as reasonably achievable/shielding, did not adversely impact the developing fetus.

Current Role of Laser Interstitial Thermal Therapy in the Treatment of Intracranial Tumors

Laser interstitial thermal therapy (LITT) is gaining popularity in the treatment of both primary and secondary intracranial tumors. The goal of LITT is to deliver thermal energy in a predictable, controlled, and minimally invasive fashion. It can be particularly valuable in patients with recurrent tumors who, due to previous radiation or surgery, may have a potentially higher risk of wound breakdown or infection with repeat craniotomy. Deep-seated lesions that are often inaccessible through open approaches (thalamus, hypothalamus, mesial basal temporal lobe, brainstem) may also be suitable targets. The experience and data published thus far on this modality is limited but growing. This review highlights the use of LITT as a primary treatment method in a variety of intracranial tumors, as well as its application as an adjunct to established surgical techniques.

Cerebellar Mutism Syndrome after surgical resection of posterior fossa neoplastic lesions

Cerebellar Mutism Syndrome (CMS) is a well-described clinical entity that complicates surgeries for posterior fossa tumours; more so in children than adults. This review focuses on the current understanding of CMS, its incidence and risk factors. Incidence showed a variable range in retrospective studies due to variety of definitions. Risk factors can be classified as either modifiable including surgical technique, or non-modifiable which include tumour related factors. A positive correlation has been associated between tumour pathology, brain stem invasion and size of tumour at time of presentation with development of CMS.

Significance of micro-RNA expression in patients with meningioma

Recent brain tumour research has shown abnormalities in gene expression as key features for almost all common brain tumours investigated. However, there is increasing evidence that epigenetic abnormalities are also crucial for tumorigenesis. Epigenetic abnormalities are heritable alterations affecting gene expression without changing the primary DNA sequence. Epigenetic abnormalities in meningiomas include abnormal microRNA expression, altered DNA methylation and histone and chromatin modifications. In this review we identify the role of altered expression of microRNA in the development and recurrence of meningioma. Based on the review of current literature, extensive knowledge of micro-RNA expression cannot only determine tumour recurrence and prognosis but also opens up new avenues for treatment.

A species dependent response to the pro-epileptic drug pentylentetrazole in birds

Epilepsy is common disorder that affects over 50 million people worldwide. Birds remain a promising yet largely under-explored model of epilepsy. This study reports the comparison of the response of two species of birds, Australian Parrots (APs) and Sparrows (SPs), to a pro-epileptic drug, Pentylenetetrazole (PTZ). PTZ injections caused myoclonic jerks (MCJs) and tonic clonic seizures (TCSs) in both species. The frequency of MCJs in APs was greater at the dose of 75mg/kg compared to both 50mg/kg and 25mg/kg while it was not significantly different in SPs. The comparison of APs and SPs showed that the frequency of MCJs was greater in APs compared to SPs at 25mg/kg and 75mg/kg while its latency was reduced at 25mg/kg and 50mg/kg. Interestingly SPs had a reduced latency of TCSs compared to APs at 75mg/kg. Glutamatergic and Gabaergic cell count was conducted to determine an association with the epileptic response to PTZ. The Glutamatergic cell counts for SPs was significantly greater than APs and conversely the Gabaergic cell counts in APs was higher compared to SPs. The reason for this difference in findings needs to be further investigated. This study shows that birds, and APs and SPs in particular, are a valid, interesting and under-explored model of epilepsy that should be further explored in order to understand the mysteries of epilepsy.

Exposure and mineralogical correlates of pulmonary fibrosis in chrysotile asbestos workers

OBJECTIVES

The relation between lifetime cumulative exposure to asbestos, pathological grade of pulmonary fibrosis, and lung burden of asbestos at death, was explored in a necropsy population of former workers in a chrysotile asbestos textile plant in South Carolina.

METHODS

Estimates of cumulative, mean, and peak exposures to asbestos were available for 54 workers. Necropsy records and lung tissue samples were obtained from hospital files. Matched control cases were selected from consecutive necropsies performed at the same hospitals. The extent and severity of pulmonary fibrosis was graded on tissue sections. Mineral fibres in lung tissue were characterised by transmission electron microscopy combined with x ray spectroscopy.

RESULTS

A significant positive correlation (r = 0.67, P < 0.0001) was found between lifetime cumulative exposure to asbestos and total lung burden of asbestos fibres. This relation was also found for the individual types of asbestos associated with the exposure: chrysotile and tremolite. Pulmonary fibrosis was correlated with both cumulative exposure to asbestos (r = 0.60, P < 0.01) and the concentration of asbestos fibres in the lung (r = 0.62, P < 0.0001). The concentration of tremolite fibres in the lung provided a better estimate of lung fibrosis than did the concentration of chrysotile. Asbestosis was usually present in asbestos textile workers with more than 20 fibre-years cumulative exposure. The lengths and aspect ratios of chrysotile asbestos, but not amphibole asbestos, were greater in the lungs of asbestos fibre workers than in the control population. Textile workers with lung cancer had significantly greater cumulative exposures and fibrosis scores than workers without lung cancer.

CONCLUSIONS

Both cumulative exposure to asbestos and lung fibre burden are strongly correlated with severity of asbestosis. The data also support the hypothesis that the high prevalence of asbestosis and lung cancer in this population resulted from exposure to long fibres of chrysotile asbestos in the workplace.

Retention patterns of asbestos fibres in lung tissue among asbestos cement workers

Retention patterns in lung tissue (determined by transmission electron microscopy and energy dispersive spectrometry) of chrysotile, tremolite, and crocidolite fibres were analysed in 69 dead asbestos cement workers and 96 referents. There was an accumulation of tremolite with time of employment. Among workers who died within three years of the end of exposure, the 13 with high tremolite concentrations had a significantly longer duration of exposure than seven in a low to intermediate category (medians 32 v 20 years; p = 0.018, one sided). Crocidolite showed similar patterns of accumulation. In workers who died more than three years after the end of exposure, there were no correlations between concentrations of amphibole fibres and time between the end of exposure and death. Chrysotile concentrations among workers who died shortly after the end of exposure were higher than among the referents (median difference in concentrations 13 million fibres (f)/g dry weight; p = 0.033, one sided). No quantitative differences in exposure (duration or intensity) could be shown between workers with high and low to intermediate concentrations. Interestingly, all seven workers who had had a high intensity at the end of exposure (> 2.5 f/ml), had low to intermediate chrysotile concentrations at death, whereas those with low exposure were evenly distributed (31 subjects in both concentration categories); hence, there was a dependence between last intensity of exposure and chrysotile concentration (p = 0.014). Among 14 workers with a high average intensity of exposure, both those (n = 5) with high tissue concentrations of chrysotile and those (n = 10) with high tissue concentrations of tremolite fibres had more pronounced fibrosis than those with low to intermediate concentrations (median fibrosis grades for chrysotile: 2 v 1, p = 0.021; for tremolite: 2 v 0.5, p = 0.012). Additionally, workers who died shortly after the end of exposure with high concentrations of chrysotile and crocidolite had smoked more than those with low intermediate concentrations (medians for chrysotile 35 v 15 pack-years, p = 0.030; for crocidolite 37 v 15 pack-years, p = 0.012). The present data indicate that chrysotile has a relatively rapid turnover in human lungs, whereas the amphiboles, tremolite and crocidolite, have a slower turnover. Further, chrysotile retention may be dependent on dose rate. Chrysotile and crocidolite deposition and retention may be increased by tobacco smoking; chrysotile and tremolite by fibrosis.

Talc pneumoconiosis: a pathologic and mineralogic study

Seventeen cases of "talc pneumoconiosis" were examined pathologically and mineralogically to ascertain whether a true talc pneumoconiosis existed and also to compare these results in primary, secondary, and tertiary exposures. Mineralogic analyses were performed on wet tissue or tissue blocks by a variety of techniques, including analytical transmission electron microscopy and x-ray diffraction. Overall, the pathologic appearance of the tissues was similar in primary, secondary, and tertiary exposures, although ferruginous bodies and foreign body giant cells were not always present in cases caused by secondary exposures. Mixed dust fibrotic lesions were found in two cases in which there were substantial quantities of quartz present. There was great variation in the minerals found within the lung tissues. Several cases showed significant quantities of mica and kaolin in addition to talc. One case consisted predominantly of mica and in fact could be regarded as "mica pneumoconiosis"; this diagnosis was correctly attributed because of the mineralogic findings. Tremolite fibers were found in only two cases. Substantial quantities of crocidolite and amosite fibers were found in one case. This study shows that "talcosis" frequently represents disease associated with a variety of minerals and that talc is a common denominator. It shows also the usefulness of lung dust mineral analysis, particularly in secondary industries, for evaluating the cause of a pathologic reaction when exposures are especially complex.

Mineral fibres, fibrosis, and asbestos bodies in lung tissue from deceased asbestos cement workers

Lung tissue from 76 deceased asbestos cement workers (seven with mesothelioma) exposed to chrysotile asbestos and small amounts of amphiboles, has been studied by transmission electron microscopy, together with lung tissue from 96 controls. The exposed workers with mesothelioma had a significantly higher total content of asbestos fibre in the lungs than those without mesothelioma, who in turn, had higher concentrations than the controls (medians 189, 50, and 29 x 10(6) fibres/g (f/g]. Chrysotile was the major type of fibre. The differences were most pronounced for the amphibole fibres (62, 4.7, and 0.15 f/g), especially crocidolite (54, 1.8 and less than 0.001 f/g), but were evident also for tremolite (2.9, less than 0.001, and less than 0.001 f/g) and anthophyllite (1.7, less than 0.001, and less than 0.001 f/g). For amosite, there was no statistically significant difference between lungs from workers with and without mesothelioma; the lungs of workers had, however, higher concentrations than the controls. Strong correlations were found between duration of exposure and content of amphibole fibres in the lungs. Asbestos bodies, counted by light microscopy, were significantly correlated with the amphibole but not with the chrysotile contents. Fibrosis was correlated with the tremolite but not the chrysotile content in lungs from both exposed workers and controls. Overall, similar results were obtained using fibre counts and estimates of mass.