Delta activity as an early indicator for soman-induced brain damage: a review

The organophosphorus (OP) compound soman is known to produce long-lasting epileptic seizure activity and associated brain damage. The present paper reviews the findings of five recent studies that tentatively established correlations between the development of soman-induced neuropathology and some subtle changes in the electrocortigraphic (ECoG) power spectrum. It is important to note that the reported experiments have been performed independently by three different teams (France, The Netherlands, USA) in various animal models (rat, guinea-pig, cynomolgus monkey) through different protocols of intoxication, pharmacological environments, and methods for ECoG spectral analysis. Despite these disparities, the five studies show that a suistained shift of ECoG power toward the lowest frequency range, i.e. the delta band, occurs within the first hours of soman-induced seizures. This early ECoG spectral change is concurrent with the first neuropathological changes in brain and is almost constantly followed, days or weeks later, by at least minimal neuropathology. Moreover the relative contribution of delta activity to the ECoG power spectrum still remains abnormally high for 1-3 days after seizure onset, i.e. within the phase of damage maturation. On the other hand, somnan-induced neuropathology was not observed in non-seizuring animals in which the delta activity was not increased above the pre-soman baseline. Similarly, no brain damage was ever shown in seizuring subjects in which the initial delta change eventually normalized after the curative administration of efficient anticonvulsant drugs such as the non-competitive antagonists of the NMDA receptor. These results, in agreement with previously published observations, strongly suggest that an increase of the relative power in the delta band might be a real-time marker of the ongoing development of soman-induced, seizure-related cerebral lesions and a reliable predictor for the final neuronal losses to come. Therefore, the monitoring of delta activity during the 24-72 h period that follows soman exposure may potentially be a useful tool to follow "on-line" the progression of brain damage and to control the neuroprotective activity of'a medication. Moreover since the method is non-invasive in man and since the above-presented results have been partly found in primates, the applicability of spectral analysis as a prognostic means in human OP poisoning ought to be seriously considered.

[Patient choice for cancer treatment: towards a shared-decision model?]

The process of medical decision implies the elaboration of a choice between alternatives. Who has the choice? The doctor? The patient? Both? That depends on the particular characteristics of the patient and of the tumour, but also of the characteristics of the doctor and of his approach of medical discipline. For that reason, we planned first to remind some principles. In our analysis, the patient-doctor's relationship ties with environment, culture and habits. Philosophical principles, moral, and models of the relation between patient and doctor concern first part. In the second part, these ideas are compared with our routine practice: surveys about patients' needs, the obstacles for complete information and participation, studies on patients' preferences. The authors' analysis is that we are going inescapably towards shared decision-making taking into account the patients preferences. This evolution is not only tied with ethical principles, but with medical reason, i.e. the variability of patients' preferences led to tailor the treatment to the individual patient especially when benefit is limited. Of course, the applicability of a shared model depends on the particular situation of the patient and of his demand. It is all the easier as the consequences of the treatment are well known the riks tiny and distant. In the classical paternalistic model, there is no choice for the patient because the doctor(s) give the treatment. In the ideal model of the shared decision, doctor and patient progress together towards medical decision, in this case, the patient is not alone facing a choice, and in all cases, he is never alone.

Effects of thienylphencyclidine (TCP) on seizure activity and brain damage produced by soman in guinea-pigs: ECoG correlates of neurotoxicity

The capacity of thienylcyclohexylpiperidine (TCP), a non-competitive blocker of the N-methyl-D-aspartate (NMDA) receptor, to counteract the convulsant, lethal, and neuropathological effects of 2 x LD50 of soman (an irreversible inhibitor of cholinesterase) was investigated in guinea-pigs treated by pyridostigmine and atropine sulphate. The effects of a weak dose of TCP (1 mg/kg) used in the present study globally reproduced those previously obtained with a higher dose (2.5 mg/kg; [Neurotoxicology 15 (1994) 837]): TCP was again most protective when given curatively within the first hour of soman-induced seizures. In this condition, (a) paroxysmal activity ceased in 10-20 min, (b) all the animals survived, (c) the majority of them recovered remarkably well and did not show any brain damage 24 h after the intoxication, and (d) the minimal duration of seizure activity normally required for producing soman-induced brain damage in other pharmacological environments was increased from 10 to 40 min to 80 min. Strikingly, when TCP was given 120 min after seizure onset, it failed to show any anticonvulsant activity but still provided neuroprotection in the hippocampus. The present study also gives additional evidence (see [Neurotoxicology 21 (4) (2000) 521]) that in soman poisoning, (a) the development of brain damage depends on the occurrence of ECoG seizures, (b) the topographical distribution of lesions depends on seizure duration, and (c) an increase of the relative power in the lowest (delta) frequency band might be a reliable marker of neuronal degradation. All these findings confirm that (a) glutamatergic NMDA receptors are involved in the mechanisms of soman-induced seizures and brain damage, (b) non-competitive antagonists of NMDA receptors might be promising candidates for post-treatment of soman poisoning, and (c) ECoG parameters from ECoG tracings and power spectrum might serve as useful external predictors for soman-induced neuropathological changes.

Histologic changes associated with experimental partial anterior disc displacement in the rabbit temporomandibular joint

AIMS

To correlate histologic changes with the stress developed by various disc interferences via a model of partial anterior disc displacement in the rabbit temporomandibular joint (TMJ).

METHODS

Eighteen male New Zealand rabbits were operated on to expose the temporomandibular disc without severing its attachments. A suture was passed around the lateral part of the disc over the condylar attachments and the 2 strands were fixed in the orbital cavity. In 9 rabbits, a resorbable suture was used to secure the disc displacement. In the other 9, a nonresorbable suture was fixed with a nickel-titanium spring to displace and maintain tension on the disc. Three non-operated animals served as controls. The animals were sacrificed at 12 and 24 weeks after surgery, and the TMJs were prepared for undecalcified histology.

RESULTS

In the first group, the disc remained in a normal position, but its morphology was modified and small histologic changes were observed in the cartilage. In the second group, the disc was displaced in various positions corresponding to the strength delivered by the spring.

CONCLUSION

Adaptive changes were observed in joints with a slightly displaced disc, while degenerative changes were associated with larger disc displacements. In each experimental joint, histologic changes increased from the medial to lateral parts. This phenomenon was related to the stress gradient induced by axial disc rotation over the condyle. Any disc displacement always resulted in changes in the cartilage.

Evaluation of toxicity and efficacy of 186Re-hydroxyethylidene diphosphonate in patients with painful bone metastases of prostate or breast cancer

Twenty-eight patients (12 men with prostate cancer, 16 women with breast cancer) were included in a phase II trial to evaluate the efficacy of 186Re-hydroxyethylidene diphosphonate (HEDP) on pain from bone metastasis and the toxicity of this agent.

METHODS

After intravenous administration of 1295 MBq 186Re-HEDP, the efficacy was evaluated by means of a daily log.

RESULTS

We observed an objective response in 67% of prostate cancer patients and in 36% of breast cancer patients. The mean duration of response was 45 d for prostate cancer patients and 24 d for breast cancer patients. No major adverse effects were observed. Marrow toxicity did not exceed grade 2 for white blood cells and grade 3 for platelets using National Cancer Institute criteria.

CONCLUSION

186Re-HEDP provides safe symptomatic relief of pain in prostate cancer patients. The benefit of this treatment is less clear in breast cancer patients. Further studies should be conducted to evaluate treatment by 186Re-HEDP at an earlier stage of the disease.

Effects of atropine sulphate on seizure activity and brain damage produced by soman in guinea-pigs: ECoG correlates of neuropathology

The present study describes the effects of pyridostigmine (PYR; 0.2 mg/kg) and atropine sulphate (AS; 5 mg/kg) on guinea-pigs intoxicated by a high dose (2xLD50) of the organophosphate compound, soman, an irreversible inhibitor of acetylcholinesterase. The medication was shown to counteract the acute respiratory distress and lethality normally produced by the intoxication. Moreover, due to the central activity of AS, soman-induced electrocorticographic (ECoG) seizure activity was either totally prevented, or reduced in duration and overall intensity. In addition, as established in the 24-hr survivors, seizure-related neuropathology was either prevented, or reduced in topographical extent and severity. An attempt to correlate our electrographic and morphological findings gives evidence that (a), the occurrence of seizure activity is the primary factor necessary for the development of acute neuropathology; (b), the duration of ECoG seizures is a secondary factor, on which the topographical distribution of brain damage finally depends; (c), the minimal duration of seizures necessary to produce 24 hr-damage in the most sensitive areas (e.g. the amygdala) is less than 70 min; (d), the overall intensity/power of epileptiform discharges is a tertiary factor which influences the severity of damage; (e), in addition, ECoG power spectral analysis suggested that an acute increase of relative power in the lower (delta) frequency band might be a real-time external marker of the starting cerebral lesions and is thus predictive for their future installation. All these data confirm the tight relationships which exist between seizure activity and neuropathology in soman poisoning, and suggest that refined, standardized analysis of electrographic parameters drawn from ECoG tracings and power spectrum might serve as a useful tool to predict the presence, localization, and severity of soman-induced brain damage.

Anomalous X-ray diffraction with soft X-ray synchrotron radiation

Anomalous diffraction with soft X-ray synchrotron radiation opens new possibilities in protein crystallography and materials science. Low-Z elements like silicon, phosphorus, sulfur and chlorine become accessible as new labels in structural studies. Some of the heavy elements like uranium exhibit an unusually strong dispersion at their M(V) absorption edge (lambdaMV = 3.497 A, E(MV) = 3545 eV) and so does thorium. Two different test experiments are reported here showing the feasibility of anomalous X-ray diffraction at long wavelengths with a protein containing uranium and with a salt containing chlorine atoms. With 110 electrons the anomalous scattering amplitude of uranium exceeds by a factor of 4 the resonance scattering of other strong anomalous scatterers like that of the lanthanides at their L(III) edge. The resulting exceptional phasing power of uranium is most attractive in protein crystallography using the multi-wavelength anomalous diffraction (MAD) method. The anomalous dispersion of an uranium derivative of asparaginyl-tRNA synthetase (hexagonal unit cell; a = 123.4 A, c = 124.4 A) has been measured for the first time at 4 wavelengths near the M(V) edge using the beamline ID1 of ESRF (Grenoble, France). The present set up allowed to measure only 30% of the possible reflections at a resolution of 4 A, mainly because of the low sensitivity of the CCD detector. In the second experiment, the dispersion of the intensity of 5 X-ray diffraction peaks from pentakismethylammonium undecachlorodibismuthate (PMACB, orthorhombic unit cell; a = 13.003 A, b = 14.038 A, c = 15.450 A) has been measured at 30 wavelengths near the K absorption edge of chlorine (lambdaK = 4.397 A, EK= 2819.6 eV). All reflections within the resolution range from 6.4 A to 3.4 A expected in the 20 degree scan were observed. The chemical state varies between different chlorine atoms of PMACB, and so does the dispersion of different Bragg peaks near the K-edge of chlorine. The results reflect the performance of the beamline ID1 of ESRF at wavelengths beyond 3 A at the end of 1998. A gain by a factor 100 for diffraction experiments with 4.4 A photons was achieved in Autumn 1999 when two focusing mirrors had been added to the X-ray optics. Further progress is expected from area detectors more sensitive to soft X-rays. Both CCD detectors and image plates would provide a gain of two orders of measured intensity. Image plates would have the additional advantage that they can be bent cylindrically and thus cover a larger solid angle in reciprocal space. In many cases, samples need to be cooled: closed and open systems are presented. A comparison with the state of art of soft X-ray diffraction, as it had been reached at HASYLAB (Hamburg, Germany), and as it is developing at the Brookhaven National Laboratory (USA), is given.

Feasibility and review of anomalous X-ray diffraction at long wavelengths in materials research and protein crystallography

The feasibility and a review of progress in the long-wavelengths anomalous dispersion technique is given in the context of the development of beamline ID1 of the ESRF for such studies. First experiments on this beamline and their analyses are described. The first study reports on the use of uranium which exhibits an unusually strong anomalous dispersion at its M(V) absorption edge (lambda(M(V)) = 3.5 A). The anomalous scattering amplitude of uranium with 110 anomalous electrons exceeds the resonance scattering of other strong anomalous scatterers like that of the rare earth ions by a factor of four. The resulting exceptional phasing power of uranium is most attractive in protein crystallography using the MAD method. The anomalous dispersion of a uranium derivative of asparaginyl-tRNA synthetase (hexagonal, a = 124.4 A, c = 123.4 A) has been measured at three wavelengths near the M(V) edge using beamline ID1 of the ESRF. The present set-up allowed the measurement of 10% of the possible reflections at a resolution of 8 A. This is mainly due to the low sensitivity of the CCD camera. The second study, involving DAFS experiments at wavelengths near the K-absorption edge of chlorine (lambda(K) = 4.4 A), reports the use of salt crystals which give rise to much stronger intensities of diffraction peaks than those of protein crystals. In the case of a crystal of pentamethylammonium undecachlorodibismuthate (PMACB, orthorhombic, a = 13.00 A, b = 14.038 A, c = 15.45 A), all reflections within the resolution range from 6.4 A to 3.5 A and the total scan width of 24 degrees were collected. The crystalline structure of PMACB implies two chemically distinct states of the Cl atom. Consequently, different dispersions near the K-edge of chlorine are expected. The dispersion of the intensity of five Bragg peaks of the PMACB crystal has been measured at 30 wavelengths. The relative success of these preliminary experiments with X-rays of long wavelength shows that the measurement of anomalous X-ray diffraction at wavelengths beyond 3 A is feasible. Starting from the experience gained in these experiments, an increased efficiency of the instrument ID1 by two to three orders of magnitude will be achieved in this wavelength range. A comparison with different techniques of anomalous diffraction which rely on the use of argon/ethane-filled multiwire chambers and image plates as detectors for wavelengths near the K-edge of sulfur and phosphorus is also given.

The lower labial branches of the mental nerve: anatomic variations and surgical relevance

PURPOSE

The purpose of this study was to determine the cause of injuries of the lower labial branches (LLB) of the mental nerve (MN) after biopsy of minor salivary glands (BMSG), labial nodule excision, or symphyseal bone procedures using a labial approach.

PATIENTS AND METHODS

Thirty-two MN were dissected in 16 cadavers to trace the labial branches. The following factors were recorded: 1) the number of LLB; 2) the angle between the medial LLB and the fibers of the orbicularis oris muscle; 3) the anastomoses between the lateral branches; and 4) the midline crossover innervation of the LLB. The number of branches on each side, as well as values of the angle between the nerves and superficial fibers of the orbicularis oris muscle, were compared using the Wilcoxon test.

RESULTS

The mean number of LLB was 2 (SEM, 1; range, 1 to 4); the average angle between the medial LLB and the fibers of the orbicularis oris muscle was 36 degrees (SEM, 2 degrees ), without any statistical difference between the two sides (P = .78); an anastomosis between the 2 lateral branches of the LLB was observed in only 1 case; and the mean midline crossover innervation of the LLB was 25% (SEM, 14%) of the intercommisural distance. This crossover innervation was present only on the ventral surface of the lip.

CONCLUSIONS

These data suggest that injuries to the LLB could be prevented if the incision(s) are made horizontally on the dorsal aspect of the lower lip, and the angle between the incision and the long axis of the lip is approximately 36 degrees . In the case of symphyseal bone procedures using a labial route, a "U"-shaped incision parallel to the LLB is suggested.

Memory impairment after soman intoxication in rat: correlation with central neuropathology. Improvement with anticholinergic and antiglutamatergic therapeutics

The effects of soman, a potent irreversible inhibitor of acetylcholinesterase, on central neuropathology in rats were studied in relation with subsequent spatial memory impairments. In a first step, it was found that, without treatment, neuropathology and learning impairment were observed only in rats which experienced convulsions. Then, treatment consisting of atropine sulfate, and/or TCP and/or NBQX was administered to intoxicated animals at infraanticonvulsant doses to obtain a graded subsequent neuropathology and to appreciate an eventual relation between neuropathology and spatial memory impairment. Thus, a correlation between neuropathology in the hippocampal CA1 region and spatial learning performance was found, the degradation of performance of rat being directly related to the amplitude of their neural damage. A threshold was emphasized : below a certain degree of neural loss, no memory impairment was found. Only treatment with tritherapy (atropine + TCP + NBQX) was able to improve the different parameters of spatial learning, despite no effect on the convulsions of the animals.

Review of the value of gacyclidine (GK-11) as adjuvant medication to conventional treatments of organophosphate poisoning: primate experiments mimicking various scenarios of military or terrorist attack by soman

Today, organophosphorus nerve agents are still considered as potential threats in both military or terrorism situations. These agents act as potent irreversible inhibitors of acetylcholinesterase in both central and peripheral nervous systems. Conventional treatment of organophosphate poisoning includes the combined administration of a cholinesterase reactivator (an oxime), a muscarinic cholinergic receptor antagonist (atropine) and a benzodiazepine anticonvulsant (diazepam). However, numerous studies have demonstrated that the excitatory amino acid glutamate also plays a prominent role in the maintenance of organophosphate-induced seizures and in the subsequent neuropathology especially through an overactivation of the N-methyl-D-aspartate (NMDA) receptor subtype. Contrary to other non-competitive NMDA antagonists successfully tested in rodents exposed to organophosphate, gacyclidine is a novel antiNMDA compound which is in the process of approval for human use in France for neurotraumatology. This review summarizes the therapeutic value of gacyclidine as a complement to the available emergency treatment against severe organophosphate poisoning. Previous data obtained from experiments on primates in several scenarios mimicking military or terrorist attacks, using soman as the nerve agent, were used. Primates pretreated with pyridostigmine and receiving conventional emergency therapy at the first signs of poisoning survive. However, only gacyclidine is able to ensure complete management of nerve agent poisoning for rapid normalization of EEG activity, clinical recovery and neuroprotection. Gacyclidine also ensures optimal management of severe nerve agent poisoning in animals neither pretreated nor receiving emergency therapy likewise during an unexpected exposure. However, this beneficial effect is obtained provided that medical intervention is conducted rapidly after intoxication. Globally, the current lack of any other NMDA receptor antagonist suitable for human use reinforces the therapeutic value of gacyclidine as a central nervous system protective agent for the treatment of OP poisoning.

Early development of deep-vein thrombosis following hip fracture surgery: the role of venous wall thickening detected by B-mode ultrasonography

Deep-vein thrombosis (DVT) remains the most frequent complication following hip surgery. This study was designed in order to evaluate the development of DVT after hip fracture surgery, and to determine if venous wall thickening detected before surgery predisposes patients to postoperative DVT. Systematic ultrasound examinations were performed on 100 consecutive patients undergoing hip fracture surgery on the day preceding the operation, and then postoperatively on days 2, 5 and 10. A total of 12 proximal, 28 distal deep-vein and four saphenous vein thromboses were detected. Of the DVT, 19 (43%) were detected at day 2. Five out of eight patients with venous wall thickening had a previous history of DVT. Venous wall thickening was positively correlated with proximal DVT development (62.5% versus 8% incidence in the group of patients with and without venous wall thickening respectively; p<0.001, relative risk = 7.8). This study highlights the high frequency of early major thromboembolic events following hip fracture surgery. It is considered that patients with a previous history of venous thromboembolic disease should undergo B-mode ultrasonographic examination before hip fracture surgery. Patients in whom venous wall thickening is detected should have repeated postoperative ultrasonographic examinations enabling early detection of DVT.

Seizure-related opening of the blood-brain barrier produced by the anticholinesterase compound, soman: new ultrastructural observations

Previous macroscopic and light microscopic observations established that the organophosphate soman, an irreversible inhibitor of cholinesterases, produces seizure-related opening of the blood-brain barrier (BBB) to proteins. In Wistar rats, this BBB alteration was found to be reversible. This alteration was greatest during the first hour of seizures, and was topographically limited to sensitive areas such as the thalamus. In contrast, the hippocampus remained free of any vascular leakage. The present study is an attempt to elucidate, in rat thalamus, the subcellular mechanisms involved in soman-induced BBB alteration. A combination of three ultrastructural approaches was used: examination of ultra-thin sections, freeze-fracture, and post-embedding protein A-gold immunocytochemistry of the endogenous, normally exclusively blood-borne, albumin. Our findings show that soman-induced seizure activity produced no discernible structural change in the endothelial tight junctions, whereas it unambiguously increased the number of endothelial vesicles. Finally, immunolabelled albumin clearly crossed the endothelium, but was not systematically found inside the endothelial vesicles. Altogether, the present ultrastructural study confirms that soman can alter the integrity of the BBB, and demonstrates that the blood-to-brain passage of proteins does not mainly derive from the opening of tight junctions. Although transcytosis is clearly increased through the cerebral endothelium, there is little evidence that blood-borne proteins penetrate the brain in this way. The actual mechanisms of transport thus remain to be clarified.

Heat stress, even extreme, does not induce penetration of pyridostigmine into the brain of guinea pigs

Stress due to forced swimming was recently shown to allow penetration of pyridostigmine (PYR) into the brain of mice. Accordingly, it was suggested that in troops exposed to emotional stress under conditions of war, as during the Gulf War, the BBB may have unexpectedly become permeable to PYR thus leading to an increased frequency of CNS symptoms. In this study, the entry of PYR into the brain was investigated in guinea pigs subjected to different heat stress levels. In a first group, guinea pigs were maintained at room temperature for 2 hours, their core temperature remaining stable at about 39.8 degrees C. In a second group, animals were placed in a climatic chamber in order to keep their core temperature at 41.5 degrees C for 2 hours. In a third group, animals were subjected to a high ambient temperature (42.6 degrees C) during about 2 hours and developed heatstroke symptoms, their core temperature progressively increasing and reaching around 44.3 degrees C. In each group, the stress of the animals was assessed by measuring the increase of plasma cortisol level. PYR (0.2 mg/kg, s.c.) was injected 90 minutes after beginning the experiment. Penetration of the drug into the brain was examined by measurement of acetylcholinesterase (AChE) activity in the cortex, the striatum and the hippocampus of the animals 30 minutes after PYR administration. A passage of this drug into the brain was also evaluated autoradiographically after i.v. injection of tritiated PYR 90 minutes after the beginning of the experiment (100 microCi/animal). Whatever the group examined, no entry of PYR into the CNS could be detected. Exposure to an ambient temperature at 42.6 degrees C for 2 hours resulted by itself in a partial inhibition of cerebral AChE activity. Our results, which agree with previous data obtained in humans exposed to heat stress, are opposite to the recent research showing a central passage of PYR in mice following a forced swim stress test. This demonstrated that the penetration of PYR into the brain of rodents under stress depends on the experimental conditions used (animal species, nature of the stressor, etc.). Extrapolations to humans of results primarily obtained in rodents about central passage of a drug under stress must thus be done very carefully.

Anatomic and mechanical properties of the lateral disc attachment of the temporomandibular joint

PURPOSE

This study measured the strength to failure of the human temporomandibular joint (TMJ) lateral disc attachment (LDA) using a tension-compression machine. These data were correlated with the LDA location and its morphologic aspects, the age and sex of the subjects, and the amount of the lateral pterygoid muscle (LPM) inserted in the disc.

METHODS

Forty-two TMJs without any obvious internal damage were carefully dissected to preserve the LDA. The width of insertion of the lateral pterygoid muscle fibers in the anterior band, as well as the width of the disc, were measured. The tension test was performed until the complete failure of the sample using a screw machine.

RESULTS

Two types of LDA were recognized. In LDA 1, the anterior and posterior bands lateral disc junction were directly inserted on the lateral pole, whereas in LDA 2 this lateral junction was attached behind and below the pole through a sheet of fibrous tissue. The breaking points for LDA 1 (55.8 N) and LDA 2 (28.8 N) were significantly different (P = .03). No correlation was found between the amount of LPM discal fibers insertion, sex, age, or the LDA breaking strength point.

CONCLUSION

The LDA 2 insertion strongly suggests that the lateral joint ligament together with the capsule may act as a substitute for the original disc attachment to the lateral pole of the condyle.

Medical management of organophosphate-induced seizures

Recent studies concerning management of soman-induced seizures are reviewed. While drugs classically used against epilepsy in hospital appear ineffective against soman, muscarinic receptor blockers are shown to be able to prevent or stop seizures within the first 5 min after their onset. Benzodiazepine could also be considered as an emergency treatment useful during the first 10 min of seizure. Comparatively NMDA antagonists appear to be able to terminate soman-induced seizures even if the treatment is delayed after 40 min of epileptic activity. Drugs with both antimuscarinic and anti-NMDA properties may represent the most adequate pharmacological treatment to treat soman intoxication. However, the results obtained until now with these drugs must be completed in relation with their possible efficacy after i.m. administration. Propositions for future studies are reviewed.

Innervation of the human lateral pterygoid muscle

The one- or two-headed arrangement of the lateral pterygoid m. (LPM) was analysed by studying the motor nerve distribution within the muscular tissue. In all subjects, the main innervation of the lateral pterygoid m. came from the anterior trunk of the mandibular n. by one to three nerves. These nerves divided into five or six vertical branches which ramified into parallel horizontal tiny fibers. Consequently, the lateral pterygoid m. appeared to be divided into oblique sagittal planes and horizontal layers by the nerve branches, reflecting the multipennate organisation of the muscle. These layers can be selectively recruited during mandibular movements, ensuing a fine medial-lateral control. According to its nerve supply, the LPM has to be considered as a single unit made of independent functional musulo-aponeurotic layers even though its morphologic conformation is in one, two or three heads.

MR of 732 TMJs: anterior, rotational, partial and sideways disc displacements

OBJECTIVE

The purpose of this study was to determine the prevalence of anterior, sideways, rotational and partial anterior disc displacements, as well as degenerative changes in patients with clinical signs and symptoms of internal disorders.

MATERIALS AND METHODS

732 MR Images of temporomandibular joints (TMJ) were produced for 366 symptomatic patients. Image analysis included assessment of disc positions and mobility, as well as recapture in coronal and mediolaterally divided sagittal planes in closed and open positions.

RESULTS

Of these images, 545 TMJ showed an internal derangement comprised of 52% anterior disc displacements without reduction, 26% anterior disc displacements with reduction, 11% partial anterior disc displacement, 5% pure sideways displacements and 4% stuck discs. Rotational disc displacements were observed in 34% of the anterior disc displacements without reduction group and in 53% of the anterior disc displacements with reduction group. A total of 97% of the partial anterior disc displacement occurred laterally. Degenerative changes increased with age, mainly in the anterior disc displacements without reduction group.

CONCLUSION

Magnetic resonance imaging (MRI) investigations show that the disc is subject to a great variety of displacements and that there is a need for further research to refine the clinical therapy for TMJ internal derangements.

Blood low shear rate rheometry: influence of fibrinogen level and hematocrit on slip and migrational effects

Red blood cell (RBC) aggregation is of prime importance in vivo and in vitro for low flow rates. It may be estimated by rheometrical measurements at low shear rates, but these are perturbed by slip and migrational effects which have already been highlighted in the past. These effects lead to a torque decay with time so that the true value of the stress at low shear rates may be greatly underestimated. Elevated aggregation being associated with different diseases, pathological blood samples show more pronounced perturbing effects and a strong time dependency in low shear rate rheometry. To test the dependence of slip and migrational effects on RBC aggregation, and particularly to determine the way in which they depend upon fibrinogen concentration ([Fb]), a home-made measuring system with roughened internal and external walls (170 microns roughness) was used to study low shear rate rheometry for RBC suspensions in PBS buffer containing albumin (at 50 g/l) and fibrinogen at various concentrations. The influences of hematocrit, shear rate, and fibrinogen concentration were investigated. Particular attention was paid to data acquisition at low shear rates (10(-3) s-1 to 3 x 10(-2) s-1). The combined influence of hematocrit and fibrinogen was investigated by adjusting hematocrit to 44 or 57% and fibrinogen concentration ([Fb]) to 3.0-4.5-6.5 g/l. Microscopic observations of the blood samples at rest were performed. They showed that different structures were formed according to fibrinogen concentration. The rheometrical measurements indicated that torque decay with shearing duration was strongly dependent on fibrinogen concentration and on shear rate at fixed hematocrit. Migrational and slip effects were more pronounced as shear rate decreased, fibrinogen concentration was raised, and hematocrit was lowered. The results have been explained on the basis of the expected microstructure of flowing blood in relation to the microscopic observations at rest.

[MRI study of temporomandibular joint disk behavior in chilren with hyperpropulsion appliances]

Orthodontic and orthopaedic effects of hyperpropulsors have been studied, evaluating the possible adaptation of the temporo mandibular joint. Before the event of MR imaging, the positional modification of the disc could not be seen. The study has been carried out on 15 subjects, skeletal Class II, with a mean age of 11.6 years (SD = 1 year). A bilateral MR investigation has been done before and after the wear of an activator (Herbst or Monobloc with Head Gear). All patients underwent bilateral imaging in sagittal and modified coronal planes in closed and opened mouth. The qualitative analysis of the temporo-mandibular joints reveals the appearing of internal derangements, often asymptomatic, in one case out of five; the disc being anteriorly displaced on an average of 8.3 degrees (p = 0.023). These results need to be confirmed on larger samples but may modified functional approach of orthopaedic treatments in order to take into account the TMJ change.