Toxic substances and the nervous system: the role of clinical observation

Bismuth release from endodontic materials: in vivo analysis using Wistar rats

Calcium silicate-based materials are used to block the communication between the root canal and the periodontal ligament space. This brings the materials into contact with tissues and the potential for local and systemic elemental release and movement. The aim of the study was to evaluate the elemental release of bismuth from ProRoot MTA in contact with connective tissues after 30 and 180 days as well as any accumulation in peripheral organs using an animal model. Tricalcium silicate and hydroxyapatite containing 20% bismuth oxide (HAp-Bi) were used as controls. The null hypothesis was that bismuth migrates from tricalcium silicate-based materials when associated with silicon. The materials were examined using scanning electron microscopy, energy dispersive spectroscopy (SEM/EDS) and X-ray diffraction prior to implantation as well as using SEM/EDS, micro X-ray fluorescence and Raman spectroscopy after implantation to assess elemental presence in surrounding tissues. Histological analysis was used to evaluate the changes in tissue architecture and inductively coupled plasma mass spectrometry (ICP-MS) was used to investigate the elemental deposition. For the systemic investigation, routine blood analysis was performed and organs were obtained to evaluate the presence of bismuth and silicon using ICP-MS after acid digestion. In the histological analysis of the implantation sites, macrophages and multinucleated giant cells could be observed after 30 days which after 180 days became a chronic infiltrate; although, no major differences were identified in red and white blood cell analyses and biochemical tests. Implantation altered the materials as observed in the Raman analysis and bismuth was detected both locally and within kidney samples after both periods of analysis, indicating the potential for accumulation of bismuth in this organ. Smaller amounts of bismuth than observed in the kidney were also detected in blood, liver and brain for the ProRoot MTA and HAp-Bi after 180 days. Bismuth was released from the ProRoot MTA locally and was detected systemically and in samples without silicon; thus, the null hypothesis was rejected. The bismuth release demonstrated that this element accumulated both locally and systemically, mainly in the kidneys in comparison with brain and liver regardless of the material base.

Clinical and Forensic Signs Resulting from Exposure to Heavy Metals and Other Chemical Elements of the Periodic Table

Several heavy metals and other chemical elements are natural components of the Earth's crust and their properties and toxicity have been recognized for thousands of years. Moreover, their use in industries presents a major source of environmental and occupational pollution. Therefore, this ubiquity in daily life may result in several potential exposures coming from natural sources (e.g., through food and water contamination), industrial processes, and commercial products, among others. The toxicity of most chemical elements of the periodic table accrues from their highly reactive nature, resulting in the formation of complexes with intracellular compounds that impair cellular pathways, leading to dysfunction, necrosis, and apoptosis. Nervous, gastrointestinal, hematopoietic, renal, and dermatological systems are the main targets. This manuscript aims to collect the clinical and forensic signs related to poisoning from heavy metals, such as thallium, lead, copper, mercury, iron, cadmium, and bismuth, as well as other chemical elements such as arsenic, selenium, and fluorine. Furthermore, their main sources of occupational and environmental exposure are highlighted in this review. The importance of rapid recognition is related to the fact that, through a high degree of suspicion, the clinician could rapidly initiate treatment even before the toxicological results are available, which can make a huge difference in these patients' outcomes.

Myoclonus From Intoxication by Bismuth Iodoform Paraffin Paste (BIPP) Nasopharyngeal Packing

Bismuth iodoform paraffin paste (BIPP) gauze is widely used as an antiseptic wound packing in otolaryngology, head, and neck surgery. Uncommonly, BIPP can cause intoxication. Our report highlights an elderly patient who developed encephalopathy and overt myoclonus after nasopharyngectomy secondary to intoxication by the components of the BIPP gauze. The patient’s impaired renal function, the amount of BIPP packing and the extensive nature of his wound likely predisposed him to BIPP toxicity. The myoclonus and delirium resolved promptly after removal of the BIPP packs. Clinicians should be aware of the clinical features of BIPP intoxication because of its common usage.

Bismuth encephalopathy- a rare complication of long-standing use of bismuth subsalicylate

BACKGROUND

Drugs containing bismuth, although usually safe, may rarely cause neurotoxicity.

CASE PRESENTATION

We describe the case of a 44-year-old woman treated with bismuth subsalicylate for about 20 years, who developed abnormal behaviour and postural instability in two weeks. On examination, she had greyish discoloration of teeth, was confused and presented generalized myoclonic jerks. In the next days, her clinical condition deteriorated, with a reduction in alertness and more exuberant myoclonus. Brain MRI was unremarkable. CSF revealed mild elevation of protein content (47 mg/dL; reference range: 15-45 mg/dL) and elevation of white blood cell count (10/μL). Bismuth levels in urine (375 μg/L), serum (260 μg/L) and CSF (21.4 μg/L) samples were highly above the threshold for toxicity. Following supportive treatment and bismuth discontinuation, she made a full recovery within weeks.

CONCLUSIONS

Although rare, bismuth encephalopathy should be considered in patients presenting with subacute encephalopathy and myoclonus. This encephalopathy can be subacute even after a chronic exposure. Cessation of bismuth can lead to a complete resolution in weeks.

Evaluating suspected work-related neurologic disorders (clinical diagnosis)

The clinical diagnosis of work-related neurologic disorders is essentially one of exclusion because symptoms and signs are often nonspecific. The clinical reasoning requires a three-step approach: (1) establish the characteristics of the presenting disease; (2) ascertain that observed clinical features are consistent with those caused by the suspected agent(s); and (3) assess occupational exposures. A detailed history is of paramount importance in evaluating patients with suspected work-related neurologic disorders as it is in other clinical contexts, especially because in some circumstances it may represent the only criterion to establish causality. Thus, besides characterization of neurologic symptoms, including their location, quality, timecourse, and possible other associated symptoms, the work environment of the patient should be understood in full detail. In this respect, when a neurotoxin is suspected, then the history collection can be guided by the knowledge of the likely syndromes it produces. Similarly, physical examination should be directed to the target of toxicity/entrapment based on information from the work history. Although specific sites and elements of the nervous system may be affected depending on the offending agent, most neurotoxic disorders are characterized by generalized rather than focal neurologic abnormalities. Laboratory toxicologic tests have limited application for the etiologic diagnosis of neurotoxic disorders, except in cases of acute poisoning and in patients exposed to neurotoxic chemicals with prolonged half-life. In most cases examination takes place after the end of exposure, when the offending chemical is no longer detectable in body fluids. Electrophysiologic studies, in particular evoked potentials, electromyography, and conduction velocities, are important to confirm the organic basis of symptoms, particularly to detect subclinical or early neurologic involvement and to reduce the number of disorders to be considered in the differential diagnoses. In general, imaging studies with computed tomography and magnetic resonance are of limited utility in the evaluation of suspected neurotoxic disorders, except for helping to exclude other causes of the patient's clinical state. Improved conditions and safer practices in the workplace have led to a gradual shift in application of neuropsychologic evaluation from the assessment of severe neurotoxic damage to the evaluation of mild subclinical disturbances, and these tests are nowadays extensively used in screening workers exposed to neurotoxicants. Tools used in the screening of large groups of workers exposed to neurotoxicants may differ from those used in the clinic. Whereas some are obviously impractical, such as physical examination, others, such as, for instance, toxicologic tests, are used for biologic monitoring of exposure to ascertain compliance with occupational exposure limits.

A randomized prospective trial to compare four different ear packs following permeatal middle ear surgery

Surgeons choice of an ear pack is dictated by availability, previous training and personal preference. There has been no recent prospective study evaluating the use of different types of ear packs. This randomized prospective study compares the use of BIPP impregnated ribbon gauze (Aurum), Pope wicks (Xomed-Teace), silastic sheeting (Dow Corning) and tri-adcortyl ointment (Squibb) as an ear dressing following 'clear' middle ear procedures via a permeatal approach. The results showed that there was no statistically significant difference in post-operative pain and discomfort experienced, neither was there any significant difference regarding the otolaryngologist's assessment of the degree of canal granulation, stenosis or discharge with the above named packs. This study concludes that non-traditional dressings such as tri-adcortyl ointment or simply a thin silastic sheet placed on the drum are no worse than time honoured BIPP. They have, as well, the advantage of being well-tolerated by the patients.

In vivo studies on striatal dopamine D1 and D2 site binding in L-dopa-treated Parkinson's disease patients with and without dyskinesias

Dyskinesias are usually seen in Parkinson's disease (PD) patients after several years of L-dopa therapy. Their presence has been attributed to supersensitivity of striatal D1 and D2 receptors. We have used PET to assess striatal D2 receptor binding in untreated PD patients and striatal D1 and D2 binding in L-dopa-treated PD patients. Untreated patients showed a 14% increase in mean D2 receptor binding in the putamen contralateral to the more affected limbs (p < 0.02). Treated patients were segregated into subgroups according to the presence or absence of dyskinesias. There were no differences in mean caudate and putamen D1 and D2 binding between dyskinetic and nondyskinetic patients, matched for duration of clinical disease. Both dyskinetic and nondyskinetic PD subgroups showed a similar 16% reduction of mean caudate D2 binding (p < 0.01) with normal D2 binding in putamen. Mean caudate and putamen D1 binding potentials of both subgroups were reduced by 10% compared with those of controls, though this trend did not reach significance. Putamen D1 binding, however, showed a negative correlation with duration and L-dopa treatment (p < 0.03). These findings suggest that, while exposure of PD patients to L-dopa may be associated with reductions in caudate D2 and caudate and putamen D1 receptor, dyskinesias are unlikely to result from alterations in striatal dopamine receptor binding.

Efficacy of pramipexole, a novel dopamine agonist, as monotherapy in mild to moderate Parkinson's disease. The Pramipexole Study Group

A total of 335 patients with early Parkinson's disease (PD) were enrolled in a multicenter, randomized, double-blind trial designed to assess the efficacy and safety of pramipexole. Entry was restricted to patients with idiopathic PD who were not receiving levodopa. Pramipexole was administered according to an ascending dose schedule up to 4.5 mg/d. During the 7-week dose-escalation phase, each subject was titrated to his or her maximally tolerated dose of study medication. This was followed by a 24-week period of maintenance therapy. The mean daily dose during the maintenance period was 3.8 mg. Pramipexole significantly reduced the severity of PD symptoms and signs compared with placebo, as measured by decreases in parts II (Activities of Daily Living) and III (Motor Examination) of the Unified Parkinson's Disease Rating Scale at week 24 compared with baseline (p < or = 0.0001). Differences between the active drug and placebo groups emerged at week 3 (1.5 mg/d) in the ascending-dose interval and persisted throughout the maintenance phase (p < or = 0.0001). The majority of patients completed the study (pramipexole 83%, placebo 80%). In the assessment of adverse events, nausea, insomnia, constipation, somnolence, and visual hallucinations occurred more frequently in the pramipexole treatment group compared with placebo patients. No clinically significant changes were noted in blood pressure or pulse rate. Overall, these results indicate that pramipexole is safe and effective in the treatment of early PD.

Familial idiopathic brain calcification with autosomal dominant inheritance

We report a family with brain calcification, predominantly in the basal ganglia, and no evident cause such as abnormal calcium or phosphorus metabolism. The proband, a 48-year-old man, had intellectual decline, parkinsonism, and mild cerebellar ataxia. He had bilateral and symmetric calcification of the basal ganglia, thalamus, dentate nucleus, cerebral cortex, subcortical white matter, and hippocampus on CT. Calcified areas showed low- or high-intensity signals on MRI T1-weighted images, and low-intensity signals on MRI T2-weighted images. Two sons and both parents, all asymptomatic, also showed calcification of the basal ganglia, suggesting an autosomal dominant inheritance. Familial idiopathic brain calcification is a rare disorder with less than 20 previously reported families. Twelve families with autosomal dominant inheritance showed a relatively homogeneous clinical picture, which may represent a distinct clinical entity. Mental deterioration, parkinsonism, and cerebellar ataxia appear in adult life and progress gradually. CT imaging, rather than MRI, is a simple and useful means to screen family members for this condition.

Low-dose clozapine improves dyskinesias in Parkinson's disease

The severity of parkinsonian motor disability and dyskinesias was evaluated in seven levodopa-responsive patients with Parkinson's disease after an acute challenge with the mixed dopamine agonist apomorphine, before and after low-dose clozapine (50 mg) for 18 +/- 2 days. There was a significant 59% improvement (p < 0.05) of apomorphine-induced dyskinesias without aggravation of parkinsonian motor disability following clozapine treatment. The results suggest that low-dose clozapine, already shown to improve psychotic symptoms, may help to reduce severe levodopa-induced dyskinesias in parkinsonian patients.

Celiac disease with cerebral calcium and silica deposits: x-ray spectroscopic findings, an autopsy study

An increased incidence of seizures and cerebral calcifications, usually bilateral and located in the occipital cortex, has been reported in celiac patients. The histology of cerebral lesions is not well defined, and their pathogenesis is only speculative. We report the autopsy results of a patient with celiac disease, seizures, and cerebral calcifications who died following a cerebral hemorrhage caused by Fisher-Evans syndrome. Calcifications were restricted to the cortical gray matter and composed of aggregates of small calcified spicules. Calcium deposition was present as psammoma-like bodies, along small vessels, and within neurons. X-ray spectroscopy of the calcified areas revealed that calcium (43%) and silica (57%) were present in the lesions. High silica content was also found in the cerebral hemorrhagic fluid. Silica toxicity has to be considered in regard to the pathogenesis of the cerebral lesions and of the seizures.

Low-dose clozapine in the treatment of levodopa-induced mental disturbances in Parkinson's disease

Delusions and other manifestations of psychotic behavior are common side effects in Parkinson's disease (PD) patients chronically treated with dopaminergic drugs. Clozapine, a dibenzodiazepine derivative, is an antipsychotic drug largely devoid of extrapyramidal side effects. We evaluated the effects of low doses of clozapine on the mental and motor functions in PD patients requiring antipsychotic treatment. Twenty-seven PD patients taking dopaminergic drugs and who had psychotic behavior received clozapine at 12.5 to 75 mg/d. Fifteen patients received clozapine for 1 to 11 months (mean, 6.8 months) and seven received it for 12 to 24 months (mean, 18 months). No patient exhibited motor deterioration, and the psychotic features disappeared immediately, allowing discontinuation of clozapine after several months in 10 patients. Fifteen patients are still receiving clozapine and are free of psychiatric symptoms. The clozapine treatment was discontinued after 5 days (25 mg/d) in two patients because of somnolence. No patient developed neutropenia. Clozapine in low doses is effective in the treatment of drug-induced delusions and hallucinations in PD.

Extradural application of bismuth iodoform paraffin paste causing relapsing bismuth encephalopathy: a case report with CT and MRI studies

Bismuth iodoform paraffin paste (BIPP) is used in dressings in ear, nose, and throat, dental, and neurosurgical practice. Neurotoxicity due to absorption of bismuth from the BIPP pack is rare. It is preventable and reversible but likely to be fatal if unrecognised. A case of relapsing but reversible toxic encephalopathy due to a large extradural BIPP pack is reported in a 57 year old Caucasian woman, operated on for a huge basal cell carcinoma of the vertex invading the skull and extradural space. Clinical, neuroradiological (CT and MRI), and biochemical studies are presented and discussed in the light of the available literature.

Neuromuscular function and plasma drug levels in pyridostigmine treatment of myasthenia gravis

In 18 patients with generalised myasthenia treated with oral pyridostigmine, muscular strength, decrement of neuromuscular transmission in the trapezius muscle on repetitive accessory nerve stimulation, and pyridostigmine plasma level were measured repeatedly during 1-3 dosing intervals. Significant correlations between pyridostigmine concentrations and functional parameters were present in three out of 11 cases in which plasma levels changed by at least 25 ng/ml during the investigational period and peak levels did not exceed 100 ng/ml. Several other observations indicated that pyridostigmine at levels above 100 ng/ml may impair neuromuscular function.

Bipp: a case of toxicity?

Ribbon gauze impregnated with bismuth iodoform paraffin paste is a dressing used in both oral and ENT surgery. A case is presented in which it was implicated in increased postoperative morbidity highly suggestive of a toxic state.

Alzheimer's disease: environmental factors and etiologic hypotheses

A review of published reports on conventional and unconventional viruses, aluminum, neurotoxic metals and trace elements, neurotoxins of biological origin and immune systems, suggest that environmental factors, possibly multiple ones, play a significant role in the etiology of Alzheimer's disease. A complex interaction between genetic predisposition to this illness, natural aging processes, environmental factors over a life-time exposure and pathological alterations of the host immune system is proposed.

IgG immunoadsorption in experimental allergic neuritis: effect on antibody levels and clinical course

The effect of IgG immunoadsorption upon the course of chronic experimental allergic neuritis (EAN) is described. Miniature membrane plasma separators coupled with a Protein A (PA)-Sepharose immunoadsorbent column were used to perform upon conscious rabbits 5 IgG immunoadsorption treatments over 6 days. Quantitation of anti-myelin IgG and IgM by ELISA revealed that 55-65% of plasma IgG was removed per treatment. Rapid post-treatment antibody rebound was observed for anti-myelin IgG although no antibody overshoot above control levels could be observed. Anti-myelin IgM levels remained relatively unaffected by PA immunoadsorption. Comparisons of clinical scores between control and treatment animals showed that IgG immunoadsorption was significantly beneficial (day 1 post-treatment p less than 0.001; day 2 post-treatment p less than 0.05). However, rapid relapse was observed in all treatment animals such that by day 3 post-treatment no significant clinical difference between control and treatment groups could be observed. IgG immunoadsorption suppresses the clinical progression of chronic EAN in a manner similar to that seen with plasma exchange. This finding suggests that antibody modulates early disease pathogenesis.

Release of endogenous Zn2+ from brain tissue during activity

The role of divalent transition metal ions in neural function is poorly understood. In excess, these ions are associated with neurological disorders such as Wilson's disease, Pick's disease and epileptic seizures. We suggest that zinc ions, which are contained in nerve terminals, are extruded into the extracellular space during neuronal activity. Excessive levels of zinc may be released during intense neuronal activation, and contribute to the paroxysm and toxic damage observed. Zinc ions are contained in high concentrations in mossy fibres of the hippocampal formation, and it is the postsynaptic neurones of these fibres which are most susceptible to the toxic effects of kainic acid, a potent convulsant, or to chronic exposure to organometallic compounds. Here we demonstrate for the first time that Zn2+ is released into the extracellular space during excitation of hippocampal slices.

Divalent transition-metal ions (Cu2+ and Zn2+) in the brains of epileptogenic and normal mice

The concentrations of Cu2+ and Zn2+ in 3 strains of mice were determined spectrophotometrically. The brain of the inborn audiogenic mouse (DBA/2J) contains higher levels of Zn2+ and Cu2+ than those found in the normal mouse (CBA/Ca or Parkes). Small differences in the metallic content in the whole brains of audiogenic and normal mice are accentuated in the hippocampus and the colliculus.

Enolase isoenzymes in the cerebrospinal fluid of patients with diseases of the nervous system

Alpha and gamma enolase isoenzymes have been studied in 212 patients with a variety of neurological diseases. The results show that these proteins are sensitive markers of tissue damage which enable a distinction to be made between the involvement of glial and neuronal components.

Experimentally induced susceptibility to audiogenic seizure

By injecting metal ions and pyridoxal-5'-phosphate, we made the normal mouse prone to sound-induced epilepsy. We showed that the levels of glutamate and aspartate in its inferior colliculus were elevated and the concentration of gamma-aminobutyrate was lowered. The time course of audiogenic susceptibility after the treatment was closely mirrored by changes in the concentrations of glutamate, aspartate, and gamma-aminobutyrate in the inferior colliculus.

The treatment of trigeminal neuralgia by posterior fossa microsurgery

Between 1972 and 1981 57 patients underwent posterior fossa exploration in Oxford by a single surgeon for the treatment of trigeminal neuralgia. Fifty-four of these had either partial or total section of the trigeminal sensory root, 2 had microvascular decompression operations and one had both a partial sensory root section and microvascular decompression. There was no mortality and no significant morbidity. Fifty-four patients were followed up for a mean period of 4 . 5 years. Fifty-two patients (96%) had either no further pain or only minor twinges requiring no further treatment. Two other patients who had partial sections suffered no further trigeminal neuralgia after subsequent total sections. One patient who had a partial root section developed anaesthesia dolorosa and one who had a microvascular decompression developed painful dysaesthesia. All patients having partial root sections retained previously intact corneal responses--the sensory impairment in the face corresponded to the appropriate part of the portio major cut. Only 11% of patients were found to have a vascular abnormality.