MR imaging of ulnocarpal impaction after fracture of the distal radius

OBJECTIVE

The purpose of our study was to evaluate the incidence of ulnocarpal impaction after distal radius fracture using MR imaging and to correlate imaging findings with those of radiography and clinical findings.

CONCLUSION

Ulnocarpal impaction is a common finding after distal radius fracture. MR imaging can detect characteristic bone marrow changes of the lunate early after the trauma. A significant correlation exists between MR imaging findings and the extent of posttraumatic ulnar variance and pain levels.

Das akute CRPS I (Morbus Sudeck) nach distaler Radiusfraktur - Methoden der Frühdiagnostik

INTRODUCTION

CRPS I represents a frequent complication following distal radial fractures. Early diagnosis may prevent chronification of the disease. However posttraumatic pain, swelling and motor disturbances render the differentiation from normal fracture patients more difficult. The incidence of CRPS I in patients at risk and the diagnostic value of clinical evaluation, radiography and thermography in the early posttraumatic phase are analysed.

METHODS

158 consecutive patients with distal radial fractures were followed-up for 16 weeks after trauma. Apart from a detailed clinical examination 8 and 16 weeks after trauma, thermography and bilateral radiographs of both hands were performed.

RESULTS

At the end of the observation period 18 patients (11%) were clinically identified as CRPS I. The severity of the preceding trauma and the chosen therapy did not influence the process of the disease. 16 weeks after trauma easy differentiation between normal fracture patients and CRPS I patients was possible. 8 weeks after distal radial fracture clinical evaluation showed a sensitivity of 78% and a specificity of 94%. Thermography (58%) however and bilateral radiography (33%) revealed a poor sensitivity, respectively. The specificity was high for radiography (91%) and again poor for thermography (66%), respectively.

CONCLUSION

The results of the study support the importance of clinical evaluation in the early diagnosis of CRPS I. Plain radiographs facilitate the diagnosis as soon as bony changes develop.

No linkage of the interleukin-4 receptor locus on chromosome 16p11.2-12.1 with sarcoidosis in German multiplex families

We typed 241 members of 62 sarcoidosis families with 136 affected siblings for three single nucleotide polymorphisms of the interleukin-4 receptor alpha-chain gene (IL4R). Allele frequencies in patients were compared to those of healthy unrelated control individuals. The segregation of the three-point IL4R haplotypes completed by two flanking highly polymorphic microsatellite polymorphisms revealed no evidence for linkage of the IL4R gene locus with sarcoidosis.

Effectiveness of twice-weekly pyrimethamine-sulfadoxine as primary prophylaxis of Pneumocystis carinii pneumonia and toxoplasmic encephalitis in patients with advanced HIV infection

The safety and efficacy of a fixed 25 mg pyrimethamine-500 mg sulfadoxine combination supplemented with 15 mg folinic acid twice a week as primary prophylaxis of Pneumocystis carinii pneumonia (PCP) and toxoplasmic encephalitis was evaluated in 106 patients infected with the human immunodeficiency virus. All patients had a CD4+ T-lymphocyte count of less than 100 cells/microl at study entry. Efficacy in this single-arm open-label prospective study was analyzed on an as-treated basis. No patient received highly active antiretroviral treatment, including protease inhibitors or non-nucleoside reverse transcriptase inhibitors, while on study medication. PCP developed in four patients, one of whom had been noncompliant. No PCP episode occurred in the first year. Probabilities of freedom from PCP were 0.97 (95%CI, 0.92-1) after 24 months and 0.93 (95%CI, 0.84-1) after 36 months. Of 74 (69.8%) patients positive for anti-toxoplasma IgG antibodies, one noncompliant patient developed toxoplasmic encephalitis after 24 months. Allergic reactions were observed in 18 (17%) patients and resulted in permanent discontinuation in 7 (6.6%) patients. One (0.9%) patient who had continued prophylaxis despite progressive hypersensitivity reactions developed a serious adverse reaction (Stevens-Johnson syndrome). The median survival of study participants was 29 months, with relentless progression of AIDS accounting for most deaths. The prophylaxis regimen studied appeared safe and effective for primary prophylaxis of PCP and toxoplasmic encephalitis. Severe adverse events can likely be prevented by discontinuation of prophylaxis at the time allergic reactions are noted. Rechallenge frequently results in tolerance. Efficacy and safety compare favorably with previously studied regimens. This simple prophylactic regimen may provide a convenient alternative for patients failing or intolerant to approved regimens.

Long-term results after posterior fixation of thoraco-lumbar burst fractures

Current concepts of treating thoraco-lumbar burst-compression injuries are based on posterior transpedicular fixation techniques which are angular stable. However, the long-term results of this approach are controversial due to inconsistent reports and due to a paucity of data on late outcome. In the present study we analyzed 50 patients retrospectively who had an unstable burst-compression injury at T 11-L 2 (type A 3 according to Magerl) without a neurological deficit. All fractures were stabilized by an internal fixator either with or without transpedicular spongiosa grafting. Patients were treated between 1991 and 1997. Follow-up times ranged from 36 to 103 months. Follow-up examinations collected occupational, subjective and clinical data (activity score, Hannover spine score) and included radiographic measurements. The latter were used to calculate the sagittal index (SI) which measures deformities of the fractured vertebral body, and the sagittal plane kyphosis (SPK) which additionally describes an eventual destruction of the affected intervertebral disc. Compared with the preinjury status, the percentage of subjects who were able to do physical labor was reduced by half at follow-up, and four times as many patients had a permanent disability. Correspondingly, activity scores and Hannover spine scores declined significantly. After the initial surgical correction SI remained stable until follow-up, whereas SPK decreased again towards pre-operative values indicating a progressive deformity of the intervertebral disc space. Clinical results did not correlate with radiographic results, and neither the time until follow-up nor the type of fracture n or the use of transpedicular bone grafting affected clinical or radiographic results significantly.

The first bismuth phosphonate cluster. X-ray single crystal structure of [(ButPO3)10(ButPO3H)2Bi14O(10).3C6H(6).4H2O]

The reaction of triphenylbismuth and tert-butylphosphonic acid gives the bismuth phosphonate phase (ButPO3H)3Bi and the first bismuth phosphonate cluster [(ButPO3)10(ButPO3H)2Bi14O(10).3C6H(6).4H2O].

Stronger reactivity of the human primary motor cortex during observation of live rather than video motor acts

The monkey premotor cortex contains neurons that are activated both when the monkey performs motor acts and when he observes actions made by others. A similar mirror neuron system, involving several brain areas, has been found in humans. We recorded neuromagnetic oscillatory activity from the primary motor cortex of 10 healthy subjects when they observed live and videotaped finger movements. The left and right median nerves were stimulated alternatingly and the poststimulus level of the approximately 20 Hz rhythm was quantified. Compared with the rest condition, the approximately 20 Hz rhythm was dampened 15-19% more when the subjects observed live rather than videotaped hand movements, indicating stronger activation of the primary motor cortex. These results suggest that the human mirror neuron system differentiates natural and artificially presented movements.

Gene polymorphisms of immunoregulatory cytokines and angiotensin-converting enzyme in Wegener's granulomatosis

Wegener's granulomatosis is a granulomatous and vasculitic disease of unknown origin. Gene polymorphisms are known to affect phenotypes of numerous diseases. Polymorphisms within the angiotensin-converting enzyme (ACE), transforming growth factor-beta1 (TGF-beta1), and interleukin-10 (IL-10) genes are suspected to modify the course of granulomatous disorders. We examined whether the genotype frequencies of the named polymorphisms differ in Wegener's granulomatosis from those in healthy controls. Thirty-nine patients with Wegener's granulomatosis were genotyped for the deletion/insertion polymorphism in intron 16 of the ACE gene, a biallelic polymorphism in codon 25 of the TGF-beta1 gene and a biallelic polymorphism at position -1082 of the IL-10 gene and compared with healthy blood donors. For the ACE polymorphism no significant differences were detected neither in the allele frequencies nor in the genotype frequencies. For TGF-beta1 a trend to genotype CG was found. The most interesting result was the observed, significant shift to genotype AA of the IL-10 polymorphism in Wegener's granulomatosis. IL-10 and TGF-beta1, immunoregulatory cytokines capable of down-regulating T helper cell type 1 response, showed a significant shift or a trend, respectively towards genotypes associated with reduced cytokine release, leading to the hypothesis that different immunoregulatory cytokine patterns dependent on gene polymorphisms might be involved in the pathogenesis of Wegener's granulomatosis.

Assessment of the peripheral microcirculation using computer-assisted venous congestion plethysmography in post-traumatic complex regional pain syndrome type I

In complex regional pain syndrome type I (CRPS-I), edema of the affected limb is a common finding. Therefore, the changes in macro- and microcirculatory parameters were investigated to elucidate the underlying pathophysiology. Twenty-four patients with post-traumatic CRPS-I and 25 gender- and age-matched healthy subjects were examined by means of an advanced computer-assisted venous congestion strain-gauge plethysmograph. The recording of the volume response of the forearm to a stepwise inflation of an occlusion cuff placed at the upper arm enabled the calculation of the arterial blood flow into the arm (Q(a)), the vascular compliance (C), the peripheral venous pressure (P(v)), the isovolumetric venous pressure (P(vi); = hydrostatic pressure needed to achieve net fluid filtration) and the capillary filtration capacity (CFC)--an index of microvascular permeability. The study revealed no difference in any of the parameters between the right and left hand of healthy subjects. In CRPS-I patients, however Q(a), P(v), P(vi) and CFC were significantly (p < 0.01/0.001) elevated in the affected arm (Q(a) 11.2 +/- 7.0 ml x min(-1) x 100 ml(-1), P(v) 20.2 +/- 8.1 mm Hg, P(vi) 24.7 +/- 4.2 mm Hg, CFC 0.0058 +/- 0.0015 ml x min(-1) x 100 ml(-1) x mm Hg(-1)) compared to the unaffected arm (Q(a) 4.2 +/- 2.4 ml x min(-1) x 100 ml(-1), P(v) 10.0 +/- 5.1 mm Hg, P(vi) 13.2 +/- 3.7 mm Hg, CFC 0.0038 +/- 0.0005 ml x min(-1) x 100 ml(-1) x mm Hg(-1)) and the values obtained in healthy controls (Q(a) 5.1 +/- 1.3 ml x min(-1) x 100 ml(-1), P(v) 10.4 +/- 4.3 mm Hg, P(vi) 15.7 +/- 3.3 mm Hg, CFC 0.0048 +/- 0.0012 ml x min(-1) x 100 ml(-1) x mm Hg(-1)). Whereas the values in the unaffected arm of CRPS-I patients revealed no difference in Q(a), P(v) and P(vi) but a lower CFC (p < 0.01) compared to those from healthy controls. These results suggest profound changes in both macro- and microvascular perfusion in the affected arm of CRPS-I patients. The high CFC contributes to the edema formation, and combined with the elevated P(vi), they are in agreement with the hypothesis of an inflammatory origin of CRPS.

Results from a genome-wide search for predisposing genes in sarcoidosis

Sarcoidosis is a systemic disease of granulomatous inflammation and unknown etiology. An inherited predisposition is involved, and many candidate susceptibility genes have been tested in association studies. We have applied the more general strategy of genome-wide microsatellite linkage analysis to identify chromosomal regions that contribute to the risk of sarcoidosis. On the basis of 225 microsatellite markers tested in 63 families with affected siblings (138 patients) and multipoint nonparametric linkage (NPL) analysis, we found the most prominent peak (six adjacent markers including D6S1666; NPL score = 2.99; p = 0.001) at the major histocompatibility complex (MHC). Six minor peaks (p < 0.05) were found on chromosomes 1 (D1S1665 ), 3 (D3S1766 ), 7 (D7S821 and D7S3070), 9 (D9S934), and the X chromosome (DXS6789). A subset of nine families with more than two affected siblings (30 patients) contributed little to the peak at the MHC (D6S1666; NPL score = 0.79; p = 0.21). Our results point to locus heterogeneity of susceptibility to sarcoidosis, with a major effect of the MHC.

[Experiences with calcitonin treatment of patients with type I complex regional pain syndrome (CRPS I--Sudeck disease)]

PURPOSE/METHODS/PATIENTS: Calcitonin is a common treatment in patients suffering from Complex Regional Pain Syndrome Type 1 (CRPS I), although its effects are being controversially discussed. In a prospective study of 24 patients with CRPS I of the upper limb, we examined the tolerance of daily doses of 0.5 mg human calcitonin administered subcutaneously over 8 weeks. To assess the benefit of this therapy, the patients were clinically examined every second week. The results were compared to a consecutive group of 25 CRPS 1 patients who received only analgetics and physiotherapy.

RESULTS

With regard to all examined parameters (spontaneous pain, grip strength, edema, hand function, systematic temperature difference), the patients treated with calcitonin showed an improvement during the observation time. However, a statistically significant difference to the control group was calculated only for the reduction of the edema (P < 0.01). 83% (20/24 patients) of the calcitonin-treated patients suffered from severe, mostly gastroenterological side-effects. Hence therapy had to be discontinued in 3 cases (13%).

CONCLUSION

The therapy with calcitonin has the burden of numerous unpleasant side-effects and causes only a slight therapeutic improvement. Thus, calcitonin must only be prescribed with reservations for patients suffering from CRPS I.

Wavelet Transform in the analysis of the frequency composition of evoked potentials

This technical paper deals with the application of the Wavelet Transform to the study of evoked potentials. In particular, Wavelet Transform gives an optimal time-dependent frequency decomposition of the evoked responses, something difficult to be achieved with previous methods such as the Fourier Transform. We describe in detail the protocol for implementing the decomposition based on the Wavelet Transform and apply it to two different types of evoked potentials. In the first case we study alpha responses in pattern visual evoked potentials and in the second case, we study gamma responses to bimodal (auditory and visual) stimulation. Although in this study we focus on methodological issues, we briefly discuss physiological implications of the present time-frequency analysis. Furthermore, we show examples of the better performance of the wavelet decomposition in comparison with Fourier-based methods.

[When fracture pain does not subside. Recognizing complications]

Over the long term, the evolution of pain caused by fractures is determined by the quality of immobilization, the extent of edema, and by surgical, analgesic and physiotherapeutic treatment. Development of chronicity is initiated by secondary deterioration, persistence of pain in the absence of improvement, changes in the nature of the pain, its spontaneous occurrence, and the appearance of concomitant symptoms. Differential diagnostic considerations must include surgical complications, but also damage to nerves, or the complex regional pain syndrome (CRPS). A particular differential diagnostic problem is the differentiation between CRPS and other complications. Treatment must be matched to the diagnosis: conservative attempts at treatment may have to be followed up with surgical revision. Drug treatment of pain is oriented to the stepped WHO schema. Physiotherapy, physical treatment and ergotherapy play a major role in the treatment of CRPS.

[Important acute measures after fractures. Rapid and adequate treatment of pain]

Pain caused by bone fractures needs to be treated promptly and adequately to avoid negative secondary effects. Pain therapy and the healing of soft tissue are goals that are equally as important as healing of the fracture. The following factors have analgesic potential: reduction, immobilization, cooling measures, limb elevation and fasciotomy. Symptomatic treatment of pain is orientated to the WHO stepped approach, which attaches particular importance to the regular administration of analgesics, as dictated by clinical effectiveness.

[Corrected normal values for serum ACE by genotyping the deletion-/insertion-polymorphism of the ACE gene]

BACKGROUND

In sarcoidosis, serum ACE is widely recognised as a marker of disease activity. Since 1990 a deletion-/insertion polymorphism of the ACE gene is known and a correlation between the genotypes of this polymorphism and serum ACE levels has been observed. Homzygotes for the deletion allele (DD) have the highest levels and homozygotes for the insertion allele (II) the lowest. Heterozygote (DI) persons show intermediate levels. The extent of this influence varies in populations of different ethnic origin. In a large cohort of healthy individuals from North of Germany, genotype-based normal ranges for serum ACE were determined for the population of Germany for the first time.

METHODS

In 262 healthy individuals the genotype of the ACE D/I gene polymorphism was determined from genomic DNA by a PCR method. In addition, in serum samples of all these individuals ACE level was measured with a kinetic test.

RESULTS

The genotype DD was found in 29.4 % of the individuals examined, the genotype DI in 49.6 % and the genotype II in 21.0 %, respectively. These results are similar to those found in previous investigations in other populations of Central European origin. The mean serum ACE levels (95 % confidence interval) in individuals with the genotypes DD, DI and II are 59.8 U/l (31.8 - 87.8), 47.7 U/l (18.6 - 76.8) and 32.2 U/l (13.7 - 50.7), respectively. Without taking the genotype into account, the average value is 48.0 U/l (15.0 - 80.9). Differences between all genotype groups are highly significant (p < 0.0001).

CONCLUSIONS

In sarcoidosis patients, the determination of this ACE gene polymorphism once in the course of the disease allows a better interpretation of the serum ACE levels measured.

Local atomic environment of Si suboxides at the SiO2/Si(111) interface determined by angle-scanned photoelectron diffraction

Local environments of Si suboxides at the interface between a thermally grown SiO2 film and Si(111) were studied by angle-scanned photoelectron diffraction. Si 2p core-level spectra containing chemically shifted components were recorded. The components were deconvoluted by least squares fitting and assigned to different Si oxidation states. The obtained diffraction patterns of the various suboxides exhibit different features. Comparison of these patterns with multiple scattering calculations including a multipole R-factor analysis shows that a simple chemical abrupt interface model describes well the environment of the suboxides and indicates ordered SiO2 close to the interface.

Wavelet entropy in event-related potentials: a new method shows ordering of EEG oscillations

In this work we show the application of a measure of entropy defined from the wavelet transform, namely the wavelet entropy (WS), to the study of event-related potentials (ERPs). WS was computed for ERPs recorded from nine healthy subjects with three different types of stimuli, among them target stimuli in a cognitive task. A significant decrease of entropy was correlated with the responses to target stimuli (P300), thus showing that these responses correspond to a more "ordered" state than the spontaneous EEG. Furthermore, we propose the WS as a quantitative measure for such transitions between EEG ("disordered state") and ERP ("ordered state").

Bisensory stimulation increases gamma-responses over multiple cortical regions

In the framework of the discussion about gamma (approx. 40 Hz) oscillations as information carriers in the brain, we investigated the relationship between gamma responses in the EEG and intersensory association. Auditory evoked potentials (AEPs) and visual evoked potentials (VEPs) were compared with bisensory evoked potentials (BEPs; simultaneous auditory and visual stimulation) in 15 subjects. Gamma responses in AEPs, VEPs and BEPs were assessed by means of wavelet decomposition. Overall maximum gamma-components post-stimulus were highest in BEPs (P < 0.01). Bisensory evoked gamma-responses also showed significant central, parietal and occipital amplitude-increases (P < 0.001, P < 0.01, P < 0.05, respectively; prestimulus interval as baseline). These were of greater magnitude when compared with the unisensory responses. As a correlate of the marked gamma responses to bimodal stimulation we suggest a process of 'intersensory association', i.e. one of the steps between sensory transmission and perception. Our data may be interpreted as a further example of function-related gamma responses in the EEG.

Identification of catalytically important residues in the active site of Escherichia coli transaldolase

The roles of invariant residues at the active site of transaldolase B from Escherichia coli have been probed by site-directed mutagenesis. The mutant enzymes D17A, N35A, E96A, T156A, and S176A were purified from a talB-deficient host and analyzed with respect to their 3D structure and kinetic behavior. X-ray analysis showed that side chain replacement did not induce unanticipated structural changes in the mutant enzymes. Three mutations, N35A, E96A, and T156A resulted mainly in an effect on apparent kcat, with little changes in apparent Km values for the substrates. Residues N35 and T156 are involved in the positioning of a catalytic water molecule at the active site and the side chain of E96 participates in concert with this water molecule in proton transfer during catalysis. Substitution of Ser176 by alanine resulted in a mutant enzyme with 2.5% residual activity. The apparent Km value for the donor substrate, fructose 6-phosphate, was increased nearly fivefold while the apparent Km value for the acceptor substrate, erythrose 4-phosphate remained unchanged, consistent with a function for S176 in the binding of the C1 hydroxyl group of the donor substrate. The mutant D17A showed a 300-fold decrease in kcat, and a fivefold increase in the apparent Km value for the acceptor substrate erythrose 4-phosphate, suggesting a role of this residue in carbon-carbon bond cleavage and stabilization of the carbanion/enamine intermediate.

Clinical and physiologic evaluation of stellate ganglion blockade for complex regional pain syndrome type I

OBJECTIVE

The efficacy of peripheral sympathetic interruption after stellate ganglion blockade was assessed by a sympathetic function test. Results were compared with clinical signs such as temperature changes, pain reduction, and the development of Horner syndrome to evaluate the correlation with clinical investigations.

DESIGN

Stellate ganglion blockade with local anesthetics was carried out via an anterior paratracheal approach in 33 patients suffering from complex regional pain syndrome type I. Patients were examined before and after the procedure. For assessment of sympathetic nervous function, the vasoconstrictor response to sympathetic stimuli was assessed using laser Doppler flowmetry. Clinical parameters like surface temperature changes (thermography), pain relief (visual analogue scale), and Horner syndrome were monitored.

RESULTS

Twenty-three (70%) of 33 patients developed an increase in temperature difference between the treated hand and the contralateral hand of more than 1.5 degreesC after the procedure, which is a clinical sign of sympathicolysis. In 48% (n = 11) of these patients, the sympathetic function test showed an undisturbed sympathetic nervous function. In 10 patients, no significant increase in temperature difference was observed. Although these patients presented with a normal sympathetic vasoconstrictor response, 4 felt pain relief of more than 50%, suggesting a placebo effect. Only 7 patients with pain relief revealed both clinical sympathicolysis and extinguished sympathetic nervous function and qualified for sympathetically maintained pain.

CONCLUSIONS

Clinical investigation is not reliable in the assessment of stellate ganglion blockade. Proof of sympathetically maintained pain based on pain relief after stellate ganglion blockade is not conclusive.

A rare case of osteoporotic spine fracture associated with epidural lipomatosis causing paraplegia following long-term cortisone therapy

Cushing's syndrome is frequently associated with osteoporosis. Therefore, the incidence of osteoporotic spine fractures is significant. They are a rare cause of paraplegic syndromes. Additionally, epidural lipomatosis may occur in those patients. The combination of both fracture and lipomatosis may cause neurological deficit. A case of a young patient suffering from drug-induced Cushing's syndrome is reported. She developed progressive paraplegia. Radiographs demonstrated kyphosis of the thoracic spine from T7 to T9 and pathologic fractures. Urgent operation was planned to stabilize and decompress the spinal cord in the area of the kyphosis. Fortunately, magnetic resonance imaging (MRI) was conducted first. It confirmed pathologic fractures of T7-9 but also showed massive epidural fat extending from the level of T1 to T9. As suspected, laminectomy alone in the area of the fracture proved to be insufficient, as shown by myelography during operation. For treatment of paraplegia in this case of symptomatic epidural lipomatosis, an expanded laminectomy was necessary to remove all the epidural fat. Having undergone this procedure, the patient is now recovering from paraplegia. Our experience suggests that care should be taken before operative treatment of patients with pathological fractures in combination with Cushing's syndrome. In addition to vertebral fractures, epidural lipomatosis has to be taken into consideration. Those patients with neurological deficits have to be treated by an extensive laminectomy.

Wavelet entropy: a new tool for analysis of short duration brain electrical signals

Since traditional electrical brain signal analysis is mostly qualitative, the development of new quantitative methods is crucial for restricting the subjectivity in the study of brain signals. These methods are particularly fruitful when they are strongly correlated with intuitive physical concepts that allow a better understanding of brain dynamics. Here, new method based on orthogonal discrete wavelet transform (ODWT) is applied. It takes as a basic element the ODWT of the EEG signal, and defines the relative wavelet energy, the wavelet entropy (WE) and the relative wavelet entropy (RWE). The relative wavelet energy provides information about the relative energy associated with different frequency bands present in the EEG and their corresponding degree of importance. The WE carries information about the degree of order/disorder associated with a multi-frequency signal response, and the RWE measures the degree of similarity between different segments of the signal. In addition, the time evolution of the WE is calculated to give information about the dynamics in the EEG records. Within this framework, the major objective of the present work was to characterize in a quantitative way functional dynamics of order/disorder microstates in short duration EEG signals. For that aim, spontaneous EEG signals under different physiological conditions were analyzed. Further, specific quantifiers were derived to characterize how stimulus affects electrical events in terms of frequency synchronization (tuning) in the event related potentials.

[cyclo-CH2[Sn(CI2)CH2Si(Me2)]2O]: synthesis and complexation behaviour of a novel, cyclic, bidentate Lewis acid and its conversion into a tin-containing fluorosilane with intermolecular Si-F...Sn bridges

Acid-catalysed hydrolysis of [CH2[(Sn(Ph2)CH2Si(OiPr)Me2]2] followed by subsequent reaction with mercuric chloride in acetone afforded the novel silicon- and tin-containing eight-membered ring [cyclo-CH2[Sn(Cl2)CH2Si(Me2)]2O] in good yield, the crystal structure of which is reported. 119Sn NMR and X-ray studies indicate that [cyclo-CH2[Sn(Cl2)CH2Si(Me2)]2O] acts as a bidentate Lewis acid towards chloride ions exclusively forming the 1:1 complex [(Ph3P)2N]+[cyclo-CH2[Sn(Cl2)CH2Si(Me2)]2OCl]- upon addition of [(Ph3P)2N]+Cl- . Also reported are the synthesis and structure of [K(dibenzo[18]crown-6)]+[cyclo-CH2(Sn(Cl2)CH2Si(Me2)]2OF]-, the first completely characterised organostannate with a C2SnCl2F- substituent pattern. No ring-opening polymerisation could be achieved for [cyclo-CH2[Sn(Cl2)CH2Si(Me2)]2O] or for its perphenylated derivative [cyclo-CH2[Sn(Ph2)CH2Si(Me2)]2O]. The reaction of [cyclo-CH2[Sn(Cl2)CH2Si(Me2)]2O] with Me3O+BF4- gave the tin-containing fluorosilane [CH2[Sn(Cl2)CH2Si(F)Me2]2], in which the Si-F bond is activated by intermolecular Si-F...Sn interactions in the solid state.