Investigating Balloon-Vessel Contact Pressure Patterns in Angioplasty: In Silico Insights for Drug-Coated Balloons

Drug-Coated Balloons have shown promising results as a minimally invasive approach to treat stenotic arteries, but recent animal studies have revealed limited, non-uniform coating transfer onto the arterial lumen. In vitro data suggested that local coating transfer tracks the local Contact Pressure (CP) between the balloon and the endothelium. Therefore, this work aimed to investigate in silico how different interventional and device parameters may affect the spatial distribution of CP during the inflation of an angioplasty balloon within idealized vessels that resemble healthy femoral arteries in size and compliance. An angioplasty balloon computational model was developed, considering longitudinal non-uniform wall thickness, due to its forming process, and the folding procedure of the balloon. To identify the conditions leading to non-uniform CP, sensitivity finite element analyses were performed comparing different values for balloon working length, longitudinally varying wall thickness, friction coefficient on the balloon-vessel interface, vessel wall stiffness and thickness, and balloon-to-vessel diameter ratio. Findings indicate a significant irregularity of contact between the balloon and the vessel, mainly affected by the balloon's unfolding and longitudinal thickness variation. Mirroring published data on coating transfer distribution in animal studies, the interfacial CP distribution was maximal at the middle of the balloon treatment site, while exhibiting a circumferential pattern of linear peaks as a consequence of the particular balloon-vessel interaction during unfolding. A high ratio of balloon-to-vessel diameter, higher vessel stiffness, and thickness was found to increase significantly the amplitude and spatial distribution of the CP, while a higher friction coefficient at the balloon-to-vessel interface further exacerbated the non-uniformity of CP. Evaluation of balloon design effects revealed that the thicker tapered part caused CP reduction in the areas that interacted with the extremities of the balloon, whereas total length only weakly impacted the CP. Taken together, this study offers a deeper understanding of the factors influencing the irregularity of balloon-tissue contact, a key step toward uniformity in drug-coating transfer and potential clinical effectiveness.

A proof-of-concept study for the simulation of blood flow in a post arterial segment for different blood rheology models

Cardiovascular disease (CVD) and especially atherosclerosis are chronic inflammatory diseases which cause the atherosclerotic plaque growth in the arterial vessels and the blood flow reduction. Stents have revolutionized the treatment of this disease to a great extent by restoring the blood flow in the vessel. The present study investigates the performance of the blood flow after stent implantation in patient-specific coronary artery and demonstrates the effect of using Newtonian vs. non-Newtonian blood fluid models in the distribution of endothelial shear stress. In particular, the Navier-Stokes and continuity equations were employed, and three non-Newtonian fluid models were investigated (Carreau, Carreau-Yasuda and the Casson model). Computational finite elements models were used for the simulation of blood flow. The comparison of the results demonstrates that the Newtonian fluid model underestimates the calculation of Endothelial Shear Stress, while the three non-Newtonian fluids present similar distribution of shear stress. Keywords: Blood flow dynamics, stented artery, non-Newtonian fluid. Clinical Relevance- This work demonstrates that when blood flow modeling is performed at stented arteries and predictive models are developed, the non-Newtonian nature of blood must be considered.

An in silico trials platform for the evaluation of stent design effect in post-implantation outcomes

Bioresorbable Vascular Scaffolds (BVS), developed to allow drug deliver and mechanical support, followed by complete resorption, have revolutionized atherosclerosis treatment. InSilc is a Cloud platform for in silico clinical trials (ISCT) used in the design, development and evaluation pipeline of stents. The platform integrates beyond the state-of-the-art multi-disciplinary and multiscale models, which predict the scaffold's performance in the short/acute and medium/long term. In this study, a use case scenario of two Bioabsorbable Vascular Stents (BVSs) implanted in the same arterial anatomy is presented, allowing the whole InSilc in silico pipeline to be applied and predict how the different aspects of this intervention affect the success of stenting process.

How to Validate in silico Deployment of Coronary Stents: Strategies and Limitations in the Choice of Comparator

This study aims at proposing and discussing useful indications to all those who need to validate a numerical model of coronary stent deployment. The proof of the reliability of a numerical model is becoming of paramount importance in the era of in silico trials. Recently, the ASME V&V Standard Committee for medical devices prepared the V&V 40 standard document that provides a framework that guides users in establishing and assessing the relevance and adequacy of verification and validation activities performed for proving the credibility of models. To the knowledge of the authors, only a few examples of the application of the V&V 40 framework to medical devices are available in the literature, but none about stents. Specifically, in this study, the authors wish to emphasize the choice of a relevant set of experimental activities to provide data for the validation of computational models aiming to predict coronary stent deployment. Attention is focused on the use of ad hoc 3D-printed mock vessels in the validation plan, which could allow evaluating aspects of clinical relevance in a representative but controlled environment.

Real-life analysis of the causes of death in patients consecutively followed for giant cell arteritis in a French centre of expertise

OBJECTIVES

To describe, in a real-life setting, the direct causes of death in a cohort of consecutive patients with GCA.

METHODS

We retrospectively analysed the deaths that occurred in a cohort of 470 consecutive GCA patients from a centre of expertise between January 2000 and December 2019. Among the 120 patients who died, we retrieved data from the medical files of 101 patients.

RESULTS

Cardiovascular events were the dominant cause of death (n = 41, 41%) followed by infections (n = 22, 22%), geriatric situations (i.e. falls or senile deterioration; n = 17, 17%) and cancers (n = 15, 15%). Patients in each of these four groups were compared with the other deceased patients pooled together. Patients who died from cardiovascular events were more frequently male (46 vs 27%; P = 0.04) with a past history of coronary artery disease (29 vs 8%; P = 0.006). Patients who died from infections mostly had ongoing glucocorticoid treatment (82 vs 53%; P = 0.02) with higher cumulative doses (13 994 vs 9150 mg; P = 0.03). Patients who died from geriatric causes more frequently had osteoporosis (56 vs 17%; P = 0.0009) and had mostly discontinued glucocorticoid treatment (76 vs 33%; P = 0.001). The predictive factors of death in multivariate analysis were a history of coronary disease [hazard ratio (HR) 2.39; 95% CI 1.27, 4.21; P = 0.008], strokes at GCA diagnosis (HR 2.54; 95% CI 1.05, 5.24; P = 0.04), any infection during follow-up (HR 1.93; 95% CI 1.24, 2.98; P = 0.004) and fever at GCA diagnosis (HR 1.99; 95% CI 1.16, 3.28; P = 0.01).

CONCLUSION

Our study provides real-life insight on the cause-specific mortality in GCA patients.

An experimental investigation into the physical, thermal and mechanical degradation of a polymeric bioresorbable scaffold

This study presents a comprehensive evaluation of the mechanical, micro-mechanical and physical properties of Reva Medical Fantom Encore Bioresorbable Scaffolds (BRS) subjected to a thermally-accelerated degradation protocol. The Fantom Encore BRS were immersed in phosphate buffered saline solution at 50 °C for 112 days with radial compression testing, nanoindentation, differential scanning calorimetry, gel permeation chromatography and mass loss characterisation performed at consecutive time points. In the initial stages of degradation (Days 0-21), the Fantom Encore BRS showed increases in radial strength and stiffness, despite a substantial reduction in in molecular weight, with a slight increase in the melt temperature also observed. In the second phase (Days 35-54), the radial strength of the BRS samples were maintained despite a continued loss in molecular weight. However, during this phase, the ductility of the stent showed a reduction, with stent fracture occurring earlier in the crimp process and with lower amounts of plastic deformation evident under visual examination post-fracture. In the final phase (Days 63-112), the load-bearing capacity of the Fantom Encore BRS showed continued reduction, with decreases in radial stiffness and strength, and drastic reduction in the work-to-fracture of the devices. Throughout each phase, there was a steady increase in the relative crystallinity, with limited mass loss until day 112 and only minor changes in glass transition and melt temperatures. Limited changes were observed in nano-mechanical properties, with measured local elastic moduli and hardness values remaining largely similar throughout degradation. Given that the thermally-accelerated in vitro conditions represented a four-fold acceleration of physiological conditions, these results suggest that the BRS scaffolds could exhibit substantially brittle behaviour after ∼ one year of implantation.

MRI Patterns in Pediatric CNS Hemophagocytic Lymphohistiocytosis

BACKGROUND AND PURPOSE

Neuroimaging has an important role in detecting CNS involvement in children with systemic or CNS isolated hemophagocytic lymphohistiocytosis. We characterized a cohort of pediatric patients with CNS hemophagocytic lymphohistiocytosis focusing on neuroradiologic features and assessed whether distinct MR imaging patterns and genotype correlations can be recognized.

MATERIALS AND METHODS

We retrospectively enrolled consecutive pediatric patients diagnosed with hemophagocytic lymphohistiocytosis with CNS involvement treated at 2 pediatric neurology centers between 2010 and 2018. Clinical and MR imaging data were analyzed.

RESULTS

Fifty-seven children (40 primary, 70%) with a median age of 36 months (interquartile range, 5.5-80.8 months) were included. One hundred twenty-three MR imaging studies were assessed, and 2 broad imaging patterns were identified. Pattern 1 (significant parenchymal disease, 32/57, 56%) was seen in older children (P = .004) with worse clinical profiles. It had 3 onset subpatterns: multifocal white matter lesions (21/32, 66%), brainstem predominant disease (5, 15%), and cerebellitis (6, 19%). All patients with the brainstem pattern failed to meet the radiologic criteria for chronic lymphocytic inflammation with pontine perivascular enhancement responsive to steroids. An attenuated imaging phenotype (pattern 2) was seen in 25 patients (44%, 30 studies) and was associated with younger age.

CONCLUSIONS

Distinct MR imaging patterns correlating with clinical phenotypes and possible genetic underpinnings were recognized in this cohort of pediatric CNS hemophagocytic lymphohistiocytosis. Disruptive mutations and missense mutations with absent protein expression correlate with a younger onset age. Children with brainstem and cerebellitis patterns and a negative etiologic work-up require directed assessment for CNS hemophagocytic lymphohistiocytosis.

An in silico trials platform for the evaluation of effect of the arterial anatomy configuration on stent implantation. Annu Int Conf IEEE Eng Med Biol Soc 2021;2021:4213-4217. [PMID: 34892153 DOI: 10.1109/embc46164.2021.9629950] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

The introduction of Bioresorbable Vascular Scaffolds (BVS) has revolutionized the treatment of atherosclerosis. InSilc is an in silico clinical trial (ISCT) platform in a Cloud-based environment used for the design, development and evaluation of BVS. Advanced multi-disciplinary and multiscale models are integrated in the platform towards predicting the short/acute and medium/long term scaffold performance. In this study, InSilc platform is employed in a use case scenario and demonstrates how the whole in silico pipeline allows the interpretation of the effect of the arterial anatomy configuration on stent implantation.

Comprehensive computational analysis of the crimping procedure of PLLA BVS: effects of material viscous-plastic and temperature dependent behavior

Recently, researchers focused their attention on the use of polymeric bioresorbable vascular scaffolds (BVSs) as alternative to permanent metallic drug-eluting stents (DESs) for the treatment of atherosclerotic coronary arteries. Due to the different mechanical properties, polymeric stents, if compared to DESs, are characterized by larger strut size and specific design. It implies that during the crimping phase, BVSs undergo higher deformation and the packing of the struts, making this process potentially critical for the onset of damage. In this work, a computational study on the crimping procedure of a PLLA stent, inspired by the Absorb GT1 (Abbott Vascular) design, is performed, with the aim of evaluating how different strategies (loading steps, velocities and temperatures) can influence the results in terms of damage risk and final crimped diameter. For these simulations, an elastic-viscous-plastic model was adopted, based on experimental results, obtained from tensile testing of PLLA specimens loaded according to ad hoc experimental protocols. Furthermore, the results of these simulations were compared with those obtained by neglecting strain rate and temperature dependence in the material model (as often done in the literature), showing how this lead to significant differences in the prediction of the crimped diameter and internal stress state.

Validation of the computational model of a coronary stent: a fundamental step towards in silico trials

The proof of the reliability of a numerical model is becoming of paramount importance in the era of in silico clinical trials. When dealing with a coronary stenting procedure, the virtual scenario should be able to replicate the real device, passing through the different stages of the procedure, which has to maintain the atherosclerotic vessel opened. Nevertheless, most of the published studies adopted commercially resembling geometries and generic material parameters, without a specific validation of the employed numerical models. In this work, a workflow for the generation and validation of the computational model of a coronary stent was proposed. Possible sources of variability in the results, such as the inter-batches variability in the material properties and the choice of proper simulation strategies, were accounted for and discussed. Then, a group of in vitro tests, representative of the device intended use was used as a comparator to validate the model. The free expansion simulation, which is the most used simulation in the literature, was shown to be only partially useful for stent model validation purposes. On the other hand, the choice of proper additional experiments, as the suggested uniaxial tensile tests on the stent and deployment tests into a deformable tube, could provide further suitable information to prove the efficacy of the numerical approach.

From the real device to the digital twin: A coupled experimental-numerical strategy to investigate a novel bioresorbable vascular scaffold

The purpose of this work is to propose a workflow that couples experimental and computational activities aimed at developing a credible digital twin of a commercial coronary bioresorbable vascular scaffold when direct access to data about material mechanical properties is not possible. Such a situation is be faced when the manufacturer is not involved in the study, thus directly investigating the actual device is the only source of information available. The object of the work is the Fantom® Encore polymeric stent (REVA Medical) made of Tyrocore™. Four devices were purchased and used in mechanical tests that are easily reproducible in any mechanical laboratory, i.e. free expansion and uniaxial tension testing, the latter performed with protocols that emphasized the rate-dependent properties of the polymer. Given the complexity of the mechanical behaviour observed experimentally, it was chosen to use the Parallel Rehological Framework material model, already used in the literature to describe the behaviour of other polymers, such as PLLA. Calibration of the material model was based on simulations that replicate the tensile test performed on the device. Given the high number of material parameters, a plan of simulations was done to find the most suitable set, varying each parameter value in a feasible range and considering a single repetitive unit of the stent, neglecting residual stresses generated by crimping and expansion. This strategy resulted in a significant reduction of computational cost. The performance of the set of parameters thus identified was finally evaluated considering the whole delivery system, by comparing the experimental results with the data collected simulating free expansion and uniaxial tension testing. Moreover, radial force testing was numerically performed and compared with literature data. The obtained results demonstrated the effectiveness of the digital twin development pipeline, a path applicable to any commercial device whose geometric structure is based on repetitive units.

Flying Fox Hemolytic Fever, Description of a New Zoonosis Caused by Candidatus Mycoplasma haemohominis

BACKGROUND

Hemotropic mycoplasmas, previously classified in the genus Eperythrozoon, have been reported as causing human infections in Brazil, China, Japan, and Spain.

METHODS

In 2017, we detected DNA from Candidatus Mycoplasma haemohominis in the blood of a Melanesian patient from New Caledonia presenting with febrile splenomegaly, weight loss, life-threatening autoimmune hemolytic anemia, and hemophagocytosis. The full genome of the bacterium was sequenced from a blood isolate. Subsequently, we retrospectively (2011-2017) and prospectively (2018-2019) tested patients who had been hospitalized with a similar clinico-biological picture. In addition, as these patients had been in contact with frugivorous bats (authorized under conditions for hunting and eating in New Caledonia), we investigated the role of these animals and their biting flies by testing them for hemotropic mycoplasmas.

RESULTS

There were 15 patients found to be infected by this hemotropic mycoplasma. Among them, 4 (27%) died following splenectomy performed either for spontaneous spleen rupture or to cure refractory autoimmune hemolytic anemia. The bacterium was cultivated from the patient's blood. The full genome of the Neocaledonian Candidatus M. haemohominis strain differed from that of a recently identified Japanese strain. Of 40 tested Pteropus bats, 40% were positive; 100% of collected bat flies Cyclopodia horsfieldi (Nycteribiidae, Diptera) were positive. Human, bat, and dipteran strains were highly similar.

CONCLUSIONS

The bacterium being widely distributed in bats, Candidatus M. haemohominis, should be regarded as a potential cause of severe infections in humans.

Design and implementation of in silico clinical trial for Bioresorbable Vascular Scaffolds

In the recent years, Bioresorbable Vascular Scaffolds (BVS) for the treatment of atherosclerosis have been introduced. InSilc is a cloud based in silico clinical trial (ISCT) platform for drug-eluting BVS. The platform integrates multidisciplinary and multiscale models predicting the BVS performance. In this study, we present a use case scenario and demonstrate the functioning of the individual modules and of the whole pipeline and the ability to predict BVS short, medium, long-term outcomes.

Biomechanical interpretation of observed fatigue fractures of peripheral Nitinol stents in the superficial femoral arteries through in silico modelling

PURPOSE

To suggest an in silico modelling approach to estimate the fatigue failure on peripheral Nitinol stents implanted in the superficial femoral artery (SFA) and interpret the clinically observed stent fractures of a retrospective series of patients.

MATERIALS AND METHODS

Preoperative data of 27 patients who underwent SFA Nitinol stenting were retrospectively analyzed. Data about preoperative features of the SFA and the lesion were collected. Follow-up data were also collected about the occurrence of restenosis/occlusion and stent fracture.

RESULTS

After a lengthening of the entire vessel, the occluded region was slightly stretched due to its high stiffness, whereas the healthy regions accommodated the artery length variation. The stent fatigue was predicted to be higher in the regions of low stiffness and higher shortening. In 7 out of 27 patients a stent fracture was clinically recorded. The model resulted to be accurate in 90% of the cases.

CONCLUSIONS

The clinical outcomes in terms of biomechanical fatigue behavior of peripheral Nitinol stents of the SFA could be interpreted by our new approach.

Synthesis and Characterization of Luminescent ZnO Powders Produced by Thermally-Induced Doping

A low cost and efficient method of doping pure zinc oxide powders for luminescence applications is presented. The powders have been obtained from pure, non-luminescent ZnO by thermally induced doping under a nitrogen flux and in the presence of ZnS powders. Structural characterization has been carried out by X-ray diffraction analysis (XRD), while luminescence properties have been studied with both a spectrofluorimeter and microraman spectrometer. Emission spectra have shown an increase of the luminescence with treatment temperature. The XRD patterns of all samples showed, along with reflections of the hexagonal phase of ZnO, other reflections ascribed to the hexagonal phase of ZnS. Upon further annealing in air at 800°C, the ZnS reflections disappear even though the luminescence still persists with a comparable intensity. Luminescence is ascribed to ZnO reduction due to the interaction of S with ZnO. It has also been observed that excitation with a He-Ne laser beam (λ=633 nm) with a high specific power (5×10−3 W·µm−2) yielded blue-green luminescence in spite of excitation below the band-to-band absorption threshold.

A new echo-Doppler method to measure interatrial conduction time. Validation and clinical usefulness

AIM

The aim of this study was to assess if knowing the interatrial conduction time is useful to better program atrioventricular delay in sequential pacing. The study proposes a new echo-Doppler method to measure interatrial conduction time, correlating it with electrophysiological measures.

METHODS

The new method was tested in 30 subjects who underwent electrophysiological study. Interatrial conduction time by new method was taken during atrial pacing as the interval between the artefact of electrocardiogram pacing, shown on screen echo, and the onset of the A wave of the echo-Doppler mitral inflow. The electrophysiological measures were obtained, in the same subjects and at the same time, by a decapolar catheter in coronary sinus as intervals between the artefact of atrial pacing and the first positive left atrial deflection at proximal (C7C8) and distal (C1C2) electrodes.

RESULTS

Echo-Doppler mean time was 114±12 ms, electrophysiological time was 107±14 ms at C7C8 and 124±11 ms at C1C2. Statistical analysis showed a good correlation (r=0.92, P<0.001) and accord (mean difference=6.6 ms) between the two methods.

CONCLUSION

The new method to measure interatrial conduction time is consistent with the electrophysiological method; it could be particularly useful in programming the best AV delay in sequential and biventricular pacing, to avoid atrial contraction against a closed mitral valve.

[Myocardial and cerebral infarction as initial presentation of antiphospholipid syndrome]

The antiphospholipid antibody syndrome is the most common acquired thrombophilia; it is a systemic autoimmune disease characterized by recurrent arterial and venous thrombosis and/or pregnancy loss, in association with circulating antiphospholipid antibodies. The pathogenic mechanisms in antiphospholipid antibody syndrome that lead to in vivo injury are incompletely understood. Like other autoimmune diseases, a combination of genetic and environmental factors is involved. We report the case of a 50-year-old woman suffering from an antero-lateral non-ST-elevation myocardial infarction. After few days, coronary angiography showed a severe occlusive arterial disease, involving anterior descending, circumflex e right coronary arteries. Percutaneous coronary intervention was performed with the implantation of a drug-eluting stent in the proximal segment of the anterior descending coronary artery. One day after discharge (10 days after the first hospitalization) the patient experienced dizziness, nausea, vomiting, swelling in absence of any electrocardiographic abnormalities or myocardial enzyme elevation; then she was hospitalized in the neurology department. Because of a similar episode, urgent cerebral computed tomography scan was performed 5 days later; it revealed two different acute ischemic areas, parietal in the right hemisphere and cerebellar in the left hemisphere. The diagnosis of antiphospholipid antibody syndrome was confirmed by high anticardiolipin antibody titers, also present in medium titer at 5 and 17 weeks apart. She was discharged without any sequelae, on warfarin and double antiplatelet therapy (aspirin and clopidogrel for 6 months), then warfarin and aspirin.

[Cardiac evaluation for non-cardiac surgical patients]

There is no evidence that most of the clinical examinations we prescribe before any surgical operation may be useful to a prognostic evaluation of the patient. Recently, some authors showed that there was no postoperative difference between 2 groups of patients. The 1(st) group had performed many laboratory examinations, the 2(nd) group none at all. Both the surgical operations and the characteristics of the patients may foresee a high, intermediate or low risk. The major clinical complications may be foreseen through tested algorithms. Patients who are at risk of cardiac events should perform tests which may be invasive but may reveal a serious heart disease. In some cases, the patients should have to be submitted to heart surgery before their programmed intervention.

[Blood pressure self-monitoring]

The blood pressure is measured, usually, in the last years by the patient at home. The method is useful for the screening of the true hypertensive patients, for the follow-up of "white coat" hypertension, for the control of antihypertensive therapy, and for the clinical trials. The home blood pressure is closer to real blood pressure of a subject and it is better correlated than clinical pressure to target organ damage. The normal values, 135/85 mmHg, are been established by meta-analysis studies. Automatic oscillometric devices should be used. The method, very useful in clinical practice, has to improve in accuracy and measures validation. Doctor has to spend more time to train the patient to use the devices correctly.

[Approach to the patient in vegetative state. Part II: differential diagnosis]

A prerequisite to the diagnosis of vegetative state is the exclusion of apparently similar syndromes, in which the patient retains the consciousness partially or even completely. Some syndromes are not separate nosological entities and should be abandoned: the apallic state, the neocortical death, the decerebrate and decorticate state, the alpha-coma, the vigil or prolonged or irreversible coma are among them. Three conditions deserve special consideration. The term locked-in syndrome describes a patient completely paralysed and mute, but fully conscious, and is usually caused by ischemic lesions of the pons. Several variants do exist, either in the causes and site of lesion. Some patients may become paralysed and mute, but conscious because of polyneuropathies, that is in the absence of any lesions of the central nervous system. The akinetic mutism is a rare condition characterised by loss of speech and nearly absent bodily movements. Painful stimulation may cause appropriate withdrawing, and wakefulness and self-awareness may be preserved, but cognitive impairment is usually present. It must be emphasised that this condition can be due to potentially treatable lesions, such as hydrocephalus and craniopharyngioma. The term "minimally responsive" or "minimally conscious" describes severely disabled patients in whom meaningful responses can be demonstrated, although inconstantly. This condition, the true diagnostic challenge, often represents a transition phase of vegetative patients recovering consciousness. Physicians, physiotherapists and patient's relatives should work all together to reach a correct diagnosis, by using current available methods to monitorize the recovery of consciousness.

Olfaction in Parkinson's disease: methods of assessment and clinical relevance

Several neurological conditions have been reported to be associated with peripheral or central deficits of olfactory system. In recent years particular emphasis has been placed on the early and severe olfactory impairment in Parkinson's disease (PD), in which limited neuropathological studies have revealed a marked dopaminergic deficit in the olfactory tubercles. Moreover, indirect evidence suggests that dysfunction of the dopaminergic pathways from mesencephalon to the piriform cortex may play a role in olfactory impairment in PD. A large number of clinical studies have reported that olfactory loss in idiopathic PD is bilateral, present in hemiparkinsonism, unrelated to the stage or clinical subtype of the disease, and independent of antiparkinsonian medication. In addition, major olfactory alterations have been reported in familial PD and dementia with Lewy bodies but not in progressive supranuclear palsy and essential tremor. These findings might stimulate further research targeted to determine the biological substrate of dissimilar olfactory performances in these movement disorders. The present review summarizes standardized procedures for the assessment of olfactory acuity (detection threshold), identification (multiple choice odor naming), discrimination (differentiation between similar/dissimilar odorants), and memory (recognition of a substance previously smelled). Specific suggestions concerning the psychometric and neuropsychological evaluation of PD patients are provided.

Spinal cord stimulation for the treatment of refractory angina pectoris: a two-year follow-up

Twenty-three patients affected by severe, refractory angina were submitted to permanent spinal cord stimulation (SCS) and then followed in our outpatient clinic for 24 months. During the follow-up period, the number of weekly angina episodes drastically dropped from 9.2 (preimplant) to 1.8 in the 3rd, 2.5 in the 6th, 4.5 in the 12th, and 4.2 in the 24th month, with a statistically significant difference (P < 0.01) between the first and last values. A significant increase in the average exercise time from 320 +/- 120 seconds (in baseline condition) to 410 +/- 115 seconds (during SCS) was observed at the treadmill stress test (P < 0.01). SCS was well tolerated by all the patients. However, 7 patients died during follow-up (3 myocardial infarctions, 2 noncardiac deaths, and 2 sudden deaths). Three generators were replaced because of battery depletion after 15, 17, and 21 months. No serious complication was observed. In conclusion, in patients with otherwise intractable angina or already submitted to myocardial revascularization, SCS is very effective in reducing the number of angina episodes. The time of the work during exercise stress test is also significantly prolonged.

High prevalence of peripheral neuropathy in hepatitis C virus infected patients with symptomatic and asymptomatic cryoglobulinaemia

BACKGROUND

Fifty per cent of patients with chronic hepatitis C, show detectable cryoglobulinaemia, even though most of them do not show cryoglobulinaemia related symptoms. Peripheral neuropathy is present in most of the patients with symptomatic cryoglobulinaemia, where it may be the first clinical manifestation. The prevalence of peripheral neuropathy in patients with hepatitis C and cryoglobulinaemia is unknown.

AIMS

To assess the prevalence of peripheral neuropathy in HCV infected patients with symptomatic or asymptomatic detectable cryoglobulinaemia.

PATIENTS AND METHODS

Eighty-nine patients with HCV infection and detectable cryoglobulinaemia underwent electrophysiological studies.

RESULTS

Electrophysiological evidence of peripheral neuropathy was found in 37% and was significantly associated with: the presence of cryoglobulinaemia syndrome, older age, higher rheumatoid factor reactivity and immunoglobulin M levels and reduced complement C4 activity. However, electrophysiological evidence of peripheral neuropathy was unrelated to cryocrit levels and type of cryoglobulinaemia and was found in 23/68 patients without any symptoms of cryoglobulinaemia other than pain and paresthesia.

CONCLUSIONS

These findings suggest that peripheral neuropathy is frequent in patients with hepatitis C and detectable cryoglobulins. Neuropathy was found to be present in 1/3 of patients without other cryoglobulinaemia-related symptoms, thus a direct or indirect role of HCV, independent of cryoglobulinaemia, in the pathogenesis of nerve damage cannot be ruled out.

Critical illness myopathy and neuropathy

BACKGROUND

Critically ill patients may develop muscle weakness or paralysis during the course of sepsis and multiple-organ failure. We studied peripheral nerve and muscle disorders (NMD) in comatose patients.

METHOD

Comatose patients who developed paralysis associated with absent deep-tendon reflexes had electroneuromyography (ENMG) and muscle-nerve biopsy specimens taken. Onset and duration of sepsis, multiple-organ dysfunction and failure, biochemical alterations, and drugs potentially interfering with nerve-muscle function were recorded.

FINDINGS

24 patients became quadriparetic or quadriplegic; muscle changes were found in 23. Axonal neuropathy was found in eight of 22 patients examined. All patients had prolonged sepsis and multiple-organ dysfunction, but only 14 had multiple-organ failure. Drugs such as steroids, neuromuscular-blocking agents, and aminoglycosides were not responsible for paresis, and the part played by hyperglycaemia and hypoalbuminaemia is uncertain. Attending physicians predicted a fatal outcome in all cases, although six of seven survivors fully recovered within 115-210 days from the onset of paralysis.

INTERPRETATION

Comatose patients may become completely paralysed because of NMD. The diagnosis is important to avoid unnecessary investigations and unreasonably pessimistic prognosis. ENMG is essential for the diagnosis and for planning further clinical management. Biopsy needs to be done only when it is necessary to properly classify NMD.

Anterior corpus callosotomy: effects in a patient with congenital bilateral perisylvian syndrome and oromotor seizures

Anterior corpus callosotomy was performed in a patient with pseudobulbar palsy, mild mental retardation and intractable epilepsy related to congenital bilateral perisylvian cortical dysplasia. Before surgery, she had daily atonic drop attacks, rare and mainly sleep-related oromotor seizures, and multifocal and diffuse paroxysmal EEG discharges; after callosotomy, less abrupt atonic drop attacks recurred monthly and the EEG epileptiform abnormalities disappeared. Video-EEG sleep recordings revealed the clinically unsuspected serial recurrence of oromotor seizures, probably related to the clinically observed aggravation of dysarthria. New surgical techniques, in addition or alternative to callosotomy, should be developed in order to avoid or reduce the risk of aggravating some types of partial seizures in patients with bilateral cortical displastic lesions, intractable epilepsy and epileptic falls.

Occipital lobe seizures related to clinically asymptomatic celiac disease in adulthood

We report the electroclinical ictal findings of four epileptic patients with clinically asymptomatic celiac disease (CD). Celiac disease diagnosis was suspected by past history and/or computed tomography (CT) findings in all patients and confirmed by laboratory tests and jejunal biopsy. All patients had paroxysmal visual manifestations and ictal EEG discharges arising from the occipital lobe. Epilepsy evolution was favorable in two patients and severe in 2, regardless of CT evidence of occipital corticosubcortical calcifications in 2 patients. Occipital lobe seizures may be characteristic of the epilepsy related to CD, and epileptic patients with these seizures of unknown etiology should be carefully investigated for malabsorption. If past history and/or laboratory tests suggest gastrointestinal (GI) dysfunction they should also undergo small intestinal biopsy even if they do not have GI tract symptoms.

Monitoring of somatosensory evoked potentials during carotid endarterectomy: relationship with different haemodynamic parameters and clinical outcome

The authors studied the changes of Somatosensory Evoked Potentials (SEPs) performed in 241 anaesthetised patients during 264 carotid endarterectomies (CEs). SEP responses were considered significantly modified when the central conduction time was greater than 1 ms and/or when the amplitude of the complex N20-P25 decreased by at least 50%. Both CCT and N20-P25 have been correlated with different parameters, including the presence or absence of preoperative neurological deficits, the type of general anaesthesia, the status of the contralateral and the ipsilateral carotid artery, stump pressure, the use of an intraluminal shunt and the perioperative results. After carotid cross-clamping SEP responses were within the normal range in 236 CEs (89%), and abnormal in 28 (11%). A shunt was inserted 23 times in 264 (9%) cases. None of the patients operated on in this series experienced a permanent neurological deficit; there were three (1.1%) transient deficits (two Rinds and one TIA) and two deaths from non-neurological causes. Only one of the transient deficits was present when the patient woke from the anaesthetic and this event was predicted by significant modification of the SEP which did not reverse after removal of the clamps (a shunt was not used). None of the patients in our series who did not present significant modifications of SEPs during the operation had any postoperative neurological deficit. The authors conclude that SEP recording is a highly reliable and objective method for continuous monitoring of brain function during CE.

Plasma amino acid patterns in experimental acute hepatic failure: comparison between hepatectomy and liver devascularization in pigs

To clarify the physiopathologic mechanism leading to a marked increase in aromatic amino acids (AAA) in acute hepatic failure (AHF), we compared two experimental models of AHF. Ten pigs were submitted to one-stage hepatic devascularization (group A); in eight other pigs total hepatectomy was performed (group B). The animals were maintained under constant glucose infusion. The mean survival time in group A was 23 +/- 2 hours; after hepatectomy it was 30 +/- 4 hours. Hepatic coma progressively deepened from 8 +/- 3 hours in Group A animals and was delayed until 17 +/- 5 hours in the anhepatic pigs. AAA, methionine, and tryptophan immediately increased markedly in pigs with liver ischemia. In group B animals, AAA showed a slight increase only 18 hours after hepatectomy, whereas there were no significant differences in methionine and tryptophan. The different amino acid patterns in the two groups of animals demonstrate that hepatocyte necrosis is a major source of plasma amino acids after liver devascularization. The slight increase in AAA after total hepatectomy suggests that a release mechanism from muscular mass is involved in the later stages of the experiment. The onset of coma is related to the increase in AAA rather than to alterations in blood ammonia that did not differ in either group of animals.

[Angiographic control of portocaval anastomoses. A study of hepato-portal circulatory changes after shunt (author's transl)]

The hepatoportal circulatory changes which occur after porto-systemic shunts have been evaluated in 55 cirrhotic patients studied by post-operative arterioportography. In every one of these cases the shunt was patent. After side to side portocaval shunt (28 patients) the arterioportography shows the complete drainage of the splanchnic blood into the inferior vena cava. A reversed flow was observed in 20 patients. After conventional spleno renal shunt (eight patients) a maintained hepatopetal flow was present only in early angiographic controls, while in later controls all splanchnic blood flow was towards the renal vein, with evidence of reversed portal flow. Even after mesocaval shunt (ten patients) the splanchnic flow was hepatofugal. Instead, after distal splenorenal Warren shunt (two cases) the hepatopetal portal flow seems to be unaffected as evidence by angiography 15 days post-operatively. An increased of the hepatic artery diameter and its intrahepatic branches was observed in 20 out of 27 controls. This hepatic artery "hepertrophy" is related in increased hepatic artery blood flow which seems to be, according to Burchell [5], an important factor in the reestablishment of the liver circulation after portocaval shunt.

[Control of the patency of porto-systemic anastomoses]

After having discussed the direct and indirect methods to control the patency of porto-systemic anastomoses, the Authors report on their series of 42 cases (28 side-to-side porto-cava shunts, 6 end-to-side porto-cava shunts, 6 spleno-renal shunts, 2 mesenterico-cava shunts) where the postop. control was carried out with portography, hepatic superselective arteriography in 29 cases, transcaval catheterism of the anastomosis in 6 patients, and pre-op., and post-op. echotomography in 15 cases. Portography revealed 39 cases of patent anastomosis and thrombotic occlusion in 3 cases. The typical sign of shunt patency is the visualisation of the inferior V.C. and the less frequent disappearance of right gastric reflux. Furthermore the investigations consented the evaluation of altered post-shunt hepato-portal flow: side-to-side porto-cava shunt (25 patent anastomoses) revealed a complete deviation of portal glow towards the I.V.C. and in 15 cases there was inverted portal flow; portography after splenorenal shunt (5 cases of patent anastomosis) showed a preserved hepatopetal portal flow only in early controls (7 days) while in all long term controls it was hepatofugal. In 13 cases the morphology of the hepatic arterial system was compared before and after surgery; in 12 cases the hepatic artery was larger and its intrahepatic branches more tortuous after surgery Ultrasonography revealed only 8 patent shunts out of 15 examined since the amount of gas in the bowel rendered the exam technically insufficient.

[Hepato-portal circulatory changes after splenorenal anastomosis]

Hepatoportal circulation changes after the shunt were examined angiographically in 5 patients subjected to splenoportal anastomosis and splenectomy. Arterioportography was employed in all cases. Catheterisation of the anastomosis was carried out in 1 patient and suprahepatic phlebography in another. The anastomosis was found to be patent in all cases. A hepatopetal portal flow was noted solely in the two patients examined six days after surgery. Disappearance of hepatic portal perfusion was observed in one of these patients on the 15th postoperative day. Controls carried out one month, one year, and five years after the operation showed that the mesenteric-portal flow was fully deviated through the shunt towards the vena cava in all patients. Selective hepatic arteriography showed an inverted portal flow in 3 patients. An increase in the calibre of the trunk of the hepatic artery and the entire intrahepatic artery network was always present.

[Pickwickian syndrome]

Respiratory performance tests and EEG and EMG data from two obese patients with ventilatory rhythm disturbances and hypersomnolence are reported. Their insertion within the picture of the Pickwick syndrome is discussed.

Permeability of membrane to potassium in hypochromic red cells with different specific density

In hypochromic anaemias (heterozygous beta-thalassaemia and iron deficiency anaemia) ligher red cells lose more K+ than heavier ones, following incubation at 37 degrees C for 24 h. Both in the light and heavy fractions two subpopulations of cells with different permeability to K+ can be separated by a new centrifugation after incubation. On the basis of the results, a relationship between K+ permeability and probability of survival in hypochromic cells is suggested.