The McDonald Criteria for Multiple Sclerosis: time for clarification

The McDonald Criteria for Multiple Sclerosis in general have replaced the Poser criteria. Despite this, many consider that there are still areas of ambiguity. In this study, neurologists completed a questionnaire about familiarity with, usefulness and applicability of the McDonald Criteria for Multiple Sclerosis. Understanding of 'attack'; objective clinical evidence; 'two or more lesions' and their ability to interpret case scenarios was evaluated. Responses were analysed overall and by skill group. Ninety-seven consultants and 30 trainees responded, of whom 37 operated a multiple sclerosis clinic ('experts'). Some (62%) thought the McDonald Criteria for Multiple Sclerosis were useful, and 31% found them confusing or difficult to apply; 38% thought the criteria should be applied universally, others (14-28%) favoured their use for drug trials/research, and 17% rarely used them. Thirty-six (29.1%) thought the McDonald Criteria for Multiple Sclerosis specified two categories: 'MS and not MS', but others considered 'possible' or 'probable' multiple sclerosis were permitted. Experts understood better 'an attack' and 'objective clinical evidence'. All skill groups comprehended poorly what constituted an episode of demyelination, and whether Lhermitte's phenomenon was acceptable as evidence for cervical cord demyelination. A consistent response was given by 44-50% to 'two or more lesions', although this is not well defined. Criteria for primary progressive multiple sclerosis were understood well. We conclude that the McDonald Criteria for Multiple Sclerosis have improved diagnosis but areas of misinterpretation remain, particularly the definition of 'an attack', 'objective clinical evidence' and 'two or more lesions'. There was uncertainty about how many multiple sclerosis categories were permitted and whether the terms 'possible' and 'probable' were allowable. Further clarification might allow the criteria to be applied more consistently.

A timeline for Parkinson's disease

It is reasonably well established that prior to the motor phase of classical Parkinson's disease (PD) there is a prodromal period of several years duration. Once typical motor features appear, the disease continues up to 20 years depending on multiple variables. The clinical features of the prodromal and motor phases may be correlated with pathological changes in the central and autonomic nervous systems to allow a sequential plan of disease progression. We present a 'best guess' for a typical individual presenting with PD in their sixties and speculate that the disease will last approximately 40 years from the earliest non-motor features to death. Appreciation of this concept may allow better strategies for slowing or halting disease progression.

Parkinson's disease: the dual hit theory revisited

Accumulating evidence suggests that sporadic Parkinson's disease (sPD) has a long prodromal period during which several nonmotor features develop; in particular, impairment of olfaction, vagal dysfunction, and sleep disorder. Early sites of Lewy pathology are the olfactory bulb and enteric plexuses of the foregut. We propose that a neurotropic pathogen, probably viral, enters the brain via two routes: (a) nasal, with anterograde progression into the temporal lobe; and (b) gastric, secondary to swallowing of nasal secretions in saliva. These secretions might contain a neurotropic pathogen that, after penetration of the epithelial lining, could enter axons of the Meissner's plexus and via transsynaptic transmission reach the preganglionic parasympathetic motor neurons of the vagus nerve. This would allow retrograde transport into the medulla and from here into the pons and midbrain until the substantia nigra is reached and typical aspects of disease commence. Evidence for this theory from the perspective of olfactory and autonomic dysfunction is reviewed and the possible routes of pathogenic invasion are considered. It is concluded that the most parsimonious explanation for the initial events of sPD is pathogenic access to the brain through the foregut and nose-hence the term "dual hit."

Twin studies and the heritability of MS: a conclusion

OBJECTIVE

The classical twin study has the potential to evaluate the relative contribution of genes and environment and guide further research strategies, provided the sampling and methods of analysis are correct. We wish to review all the more informative twin studies on multiple sclerosis (MS).

METHODS

We examined six large population-based twin studies in MS and calculated indices of heritability (h(2)), which is the traditional method of assessing genetic contribution to disease and to allow comparison between studies.

RESULTS

This index was found to vary widely from 0.25 to 0.76 with large confidence intervals that reflect small sample size and prevent robust interpretation.

CONCLUSION

Overall the studies support a genetic contribution to disease; however, the imprecision of the heritability estimates and potential biases that they contain mean that very little inference can be drawn its exact size. Given that the magnitude of genetic effect cannot be measured because of the relative infrequency of MS; the consequent difficulty in collecting an informative sample; and in many countries, the lack of a comprehensive twin register, we suggest that further twin prevalence surveys should not be undertaken. Twin studies could be used more effectively in other ways, such as the co-twin case-control approach.

Parkinson's disease: a dual-hit hypothesis

Accumulating evidence suggests that sporadic Parkinson's disease has a long prodromal period during which several non-motor features develop, in particular, impairment of olfaction, vagal dysfunction and sleep disorder. Early sites of Lewy pathology are the olfactory bulb and enteric plexus of the stomach. We propose that a neurotropic pathogen, probably viral, enters the brain via two routes: (i) nasal, with anterograde progression into the temporal lobe; and (ii) gastric, secondary to swallowing of nasal secretions in saliva. These secretions might contain a neurotropic pathogen that, after penetration of the epithelial lining, could enter axons of the Meissner's plexus and, via transsynaptic transmission, reach the preganglionic parasympathetic motor neurones of the vagus nerve. This would allow retrograde transport into the medulla and, from here, into the pons and midbrain until the substantia nigra is reached and typical aspects of disease commence. Evidence for this theory from the perspective of olfactory and autonomic dysfunction is reviewed, and the possible routes of pathogenic invasion are considered. It is concluded that the most parsimonious explanation for the initial events of sporadic Parkinson's disease is pathogenic access to the brain through the stomach and nose - hence the term 'dual-hit'.

Multiple sclerosis in Latter Day Saints (Mormons)

BACKGROUND

Compliant members of the Church of Jesus Christ of Latter Day Saints (LDS, Mormons) have a low incidence of heart and lung disease that may relate to their healthy life style. We wished to determine whether multiple sclerosis (MS) was less frequent in this religious body.

METHODS

To ascertain this, diagnostic and treatment coding records were accessed from the Deseret Mutual Benefit Administrators (DMBA) for the 6 year period 1997-2002. DMBA is a medical insurance company that provides medical insurance to all employees of LDS Church in the US. This information was combined with prescribing records for disease modifying treatment, principally beta-interferon and Copaxone which are medications specific to MS.

RESULTS

Using various search strategies we derived an approximate MS prevalence of 45-64/100,000.

CONCLUSION

Comparison with MS rates from Utah and other states of comparable latitude suggest that strict LDS have an MS prevalence that is lower than expected and may reflect their healthy life style.

Smoking is a risk factor for multiple sclerosis: a metanalysis

Several case control studies have probed a link between cigarette smoking and subsequent multiple sclerosis (MS). Data collection and statistical methods have varied, and frequently, case numbers have been small. Publications relating to MS and smoking are reviewed and combined where comparable methods have been used. Metanalysis of six informative studies show significantly elevated odds or rate ratios, ranging from 1.22 to 1.51, depending on the method of analysis, confirming that the risk of MS is increased for those who smoke prior to disease onset, as measured by commencement of symptoms. A variety of direct causative mechanisms are discussed, but an indirect association through health adverse conduct is favoured. Multiple Sclerosis 2007; 13: 610-615. http://msj.sagepub.com

Seroprevalence of herpes simplex virus type 2 in multiple sclerosis

BACKGROUND

It has been proposed that multiple sclerosis (MS) might be a sexually transmitted disorder. There is evidence that seropositivity to herpes simplex virus type 2 (HSV-2) correlates well with the number of sexual partners. Accordingly, a raised overall HSV-2 seroprevalence in MS would lend support to this theory.

MATERIALS AND METHODS

Serum from 497 UK subjects with clinically definite MS was tested for antibodies to HSV-2 and compared with matched historical controls from within and outside London, blood donors and genito-urinary medicine (GUM) clinics.

RESULTS

The unadjusted MS seropositivity rate was 14%. HSV-2 seroprevalence in MS patients aged 35-64 years was significantly higher overall compared with a non-London general population in an unadjusted comparison. HSV-2 seroprevalence in London MS patients compared with London blood donors was significantly greater irrespective of age, but the MS seropositive rate was lower than GUM clinic attenders. In a logistic regression analysis, increased age, female sex and MS diagnosis all independently increased the odds of seropositivity after adjustment for each other.

CONCLUSION

It is concluded that there is increased likelihood of HSV-2 exposure in patients with MS and this may indicate a higher than average number of partners.

Are multiple sclerosis patients risk-takers?

Several factors appear to be associated with multiple sclerosis (MS), and each has a postulated immune or environmental explanation, but a common theme is lacking. This article suggests that a unifying premise could be risk-associated behaviour. Evidence is reviewed for associations with smoking, alcohol, recreational drug use, oral contraception, cholesterol intake, risk attitude and behaviour, ultraviolet light and vitamin D exposure, frequency of MS in healthy societies, and viral infection. The evidence associated with smoking, not taking vitamin D supplements and Epstein-Barr viral infection appears good. There may be a pattern of risk-associated behaviour that characterizes patients with MS and brings them into contact with one or more causative agents. Of the possible agents, viral infection seems the most likely.

Choreic syndrome and coeliac disease: a hitherto unrecognised association

Coeliac disease has been associated with a variety of neurological conditions, most frequently cerebellar ataxia and peripheral neuropathy. To date, chorea has not been associated with coeliac disease. We present the case histories of 4 individuals with coeliac disease and chorea (4 women, average age of onset of chorea 61 years). Unexpectedly, most of these patients showed a notable improvement in their motor symptoms after the introduction of a gluten-free diet.

Is multiple sclerosis a sexually transmitted infection?

It is proposed that multiple sclerosis may be transmitted chiefly by sexual contact. Arguments favouring this include: migration studies that suggest a transmissible agent in adolescence; clusters of multiple sclerosis which have occurred in low prevalence areas following entry of young males; the similarity of multiple sclerosis to tropical spastic paraplegia, a known sexually transmitted infection with resemblance to primary progressive multiple sclerosis; an increased rate in drug misusers; a similar age of onset and sex pattern to that found in sexually transmitted disease; increased incidence of multiple sclerosis in those using oral contraceptives; low multiple sclerosis rates in societies with a strict moral code; longitudinal shifts in sex prevalence that show an increase in women after the sexual revolution of the 1960s; and important exceptions to the worldwide distribution corresponding to countries with permissive attitudes to sex. Family, conjugal pair, twin, and adoption studies are compatible with an infectious cause of multiple sclerosis if this is sexually transmitted. It is not proposed that sexual transmission is the only cause but that inherited factors create a susceptibility to a sexually transmitted neurotropic agent. It is hoped this hypothesis might encourage a new direction of neurological research.

Is Parkinson's disease a primary olfactory disorder?

It has been known for over 30 years that olfactory function is disordered in idiopathic Parkinson's disease (IPD). The severity and partial specificity of anosmia was not realized until recently, with the advent of more detailed analysis and sophisticated measurement. The olfactory vector hypothesis suggests that the causative agent for IPD enters the brain via the nasal route, but the reason for olfactory dysfunction may be more subtle. Evidence for olfactory disturbance is reviewed from pathological, psychological, neurophysiological and genetic stand-points. It is proposed that the initial causative event in IPD may start in the rhinencephalon (olfactory brain) prior to damage in the basal ganglia.

Olfactory evoked responses and identification tests in neurological disease

To assess the value of smell testing we used olfactory evoked potentials (OEP) and an identification test in multiple sclerosis, Parkinson's disease, motor neuron disease and Alzheimer's disease.

METHODS

The OEP to H2S (20 ppm) was obtained using an olfactometer designed to stimulate olfactory nerve endings only. Odor recognition was assessed by the University of Pennsylvania Smell Identification Test (UPSIT). In all instances the disease was 'definite' based on standard diagnostic criteria. Controls were derived from 156 healthy people.

RESULTS

1) Multiple Sclerosis: 11/72 patients (15%) were abnormal on UPSIT. For OEP there was significant increase of latency and decrease in amplitude in 6/26 patients (23%). 2) Parkinson's Disease: 126/155 (81%) patients had an abnormal UPSIT score. 12/37 (32%) had prolonged latency with normal amplitude measurement on OEP, but 27 had absent or unclear readings. 4/10 with normal UPSIT displayed abnormality on OEP. 3) Motor Neuron Disease: 9/58 (16%) were abnormal on UPSIT. There was significant delay in 1/10 (10%) patients on OEP. 4) Alzheimer's Disease: UPSIT scores were abnormal in all 8 patients examined. OEP was normal in 4 of these who could be tested.

CONCLUSION

Smell dysfunction was found in all 4 conditions but most severely in Parkinson's Disease (over 80%). The UPSIT in general showed abnormality more frequently than OEP. The olfactory defect probably involves peripheral structures in all diseases tested except Alzheimer's. A patient with normal olfaction is unlikely to have idiopathic Parkinson's disease.

Olfactory disorder in motor neuron disease

In Parkinson's disease and Alzheimer's disease there is profound disorder of olfaction. The extent to which this modality is involved in motor neuron disease (MND) has been studied little. To address this further we assessed olfaction by three methods-a smell identification test ("UPSIT") in 58 patients and 135 controls; olfactory-evoked response (OEP) to H2S in 15 patients, and pathological examination of olfactory bulbs obtained from 8 cadavers. It was found that smell identification compared with the controls was slightly worse overall in the MND group as a whole, but only the bulbar patients scored significantly less on the UPSIT. Patients displayed a subtle defect in cheese odor recognition. OEPs were normal in 9 subjects and delayed in 1 subject. The remaining 5 OEPs were unsuccessful. Histopathological studies of olfactory bulbs showed excess lipofuscin deposition in all 8 cases examined, indicating subclinical neuronal damage. Olfactory neurons with a degree of antioxidant defect may be more susceptible to cellular damage than other neuronal groups because of their direct relationship to environmental agents. Overall we found the degree of olfactory dysfunction in MND to be mild and in contrast with the marked changes described by others.

Assessment of olfaction in multiple sclerosis: evidence of dysfunction by olfactory evoked response and identification tests

OBJECTIVE

To resolve whether the olfactory pathways are affected in multiple sclerosis.

METHODS

Olfaction was assessed by: (1) The University of Pennsylvania smell identification test (UPSIT, which uses microencapsulated odours that are released when scratched with a pencil) in 72 patients with multiple sclerosis and 96 controls, (2) olfactory evoked potentials (OEP) to 20 ppm H2S by volume, and 50% CO2 in air for 45 patients with multiple sclerosis and 47 controls. The abnormality rate in patients with multiple sclerosis for both tests (1) and (2) was compared with that for visual evoked potentials measured using a standard checquerboard technique.

RESULTS

By comparison with controls, patients exhibited significantly low scores on the smell identification test with 15% of patients scoring outside the 95% confidence intervals for controls. The UPSIT was occasionally abnormal when the visual evoked potential (VEP) was normal. In general UPSIT scores correlated well with the H2S-evoked response in controls and patients. For H2S, there was a statistically significant increase of latency and decrease of amplitude for patients compared with controls. Increased H2S latency and reduced UPSIT score correlated with greater disability on conventional rating scales. Overall, H2S responses were abnormal in about one quarter of patients with multiple sclerosis. The sensitivity of UPSIT and OEP was similar although disorder on one test did not necessarily indicate abnormality in the other. The visual evoked potential was found to be a more sensitive indicator of disease than OEP or UPSIT.

CONCLUSION

These findings confirm the existence of olfactory dysfunction in multiple sclerosis and validate a new evoked potential technique.

British motor neuron disease twin study

OBJECTIVES

To investigate the cause of sporadic motor neuron disease (MND) by twin study, so allowing (1) estimation of the genetic contribution, and (2) collection of matched pairs for a case-control study of possible environmental factors.

METHODS

10872 death certificates bearing the diagnosis MND were collected from 1979 to 1989 inclusive. Inspection of individual birth entries allowed identification of potential twins. The status of each co-twin was determined and contact made through the National Health Service Central Register (NHS-CR) and their general practitioner (GP). The diagnosis of MND was verified via the co-twin and relatives, and medical records where available. Zygosity was assessed using a recognised questionnaire. Details concerning environmental exposures and health were gathered by interview of cotwin and relatives using a semistructured questionnaire. Heritability (h2) of MND was estimated, and the environmental information was analysed by conditional logistic regression modelling.

RESULTS

Seventy seven probands were identified, of whom 26 were monozygotic and 51 dizygotic. Four monozygotic probands were concordant, but two probands came from a family known to have familial MND. The estimated heritability was between 0.38 and 0.85. Most environmental risk factors were not significant. Regular vehicle maintenance (odds ratio (OR) = 7.0; 95% confidence interval (95% CI) 1.3-89.9) and occupational paint usage (OR = 3.75; 95% CI 1.0-17.1), however, occurred significantly more often in the affected cases.

CONCLUSIONS

This "death discordant" method for twin collection has proved to be viable, and has allowed the ascertainment of a large population sample in a rare disease. The genetic role in sporadic MND is substantial, and higher than expected. Exposure to industrial chemicals, particularly constituents of petrochemicals and paints, may contribute to the aetiology of MND.

Olfactory dysfunction in Parkinson's disease

OBJECTIVE

To evaluate olfactory function in Parkinson's disease.

METHODS

A standardised odour identification test was used, together with an evoked potential assessment with hydrogen sulphide. In addition, histological analysis was performed on the olfactory bulbs of cadavers who died from Parkinson's disease.

RESULTS

Over 70% of patients studied (71 of 96) were outside the 95% limit of normal on the identification test in an age matched sample and there was an unusual pattern of selective loss to certain odours, not hitherto described. The evoked potentials were significantly delayed but of comparable amplitude to a control matched population. Of the 73 patients studied only 37 had a technically satisfactory record containing a clear response to both gases and of these, 12 were delayed. For H2S there was more delay on stimulating the right nostril than the left. Some patients with normal smell identification test scores had delayed evoked potentials. In the pathological examination of olfactory bulbs from eight brains, changes characteristic of Parkinson's disease (Lewy bodies) were seen in every olfactory bulb, particularly in the anterior olfactory nucleus, and were sufficiently distinct to allow a presumptive diagnosis of Parkinson's disease.

CONCLUSIONS

Olfactory damage in Parkinson's disease is consistent and severe and may provide an important clue to the aetiology of the disease.

Twin studies in medicine--what do they tell us?

A well-conducted twin study has the potential to evaluate the relative contribution of genetic and environmental factors to a given disease. Many studies are inconclusive because of problems with methodology. This article reviews the principles underlying the classical twin study and then discusses potential pitfalls. Twin studies in three diseases are evaluated, namely, multiple sclerosis, diabetes, osteoarthritis. Studies in multiple sclerosis are thought to be inconclusive. In type 1 diabetes, genetic factors are very important and according to the single study in females with osteoarthritis, genetic factors are also significant.

Twin studies in diabetes mellitus

Twin studies are a valuable way of determining the relative significance of genetic and environmental factors in the aetiology of disease. In diabetes mellitus, they are of importance, since the aetiologies of Type 1 (insulin-dependent) and Type 2 (non-insulin-dependent) diabetes mellitus are probably different. However the results of twin studies have not always been reliable. Strict adherence to methodological guidelines is necessary to ensure the validity of the results that are obtained. These guidelines relate to ascertainment of a twin sample, confirmation of zygosity, and effects of sampling. Critical review of twin studies in diabetes performed to date imply provisionally a very strong genetic input to the aetiology of Type 1 diabetes. In Type 2 diabetes genetic and environmental factors are probably of equal importance.

Diagnosis of functional neurological disease

Functional disease is a common and difficult problem in clinical neurology. A thorough appraisal should be undertaken before concluding that a patient's problem is not physically based. This article describes symptoms and signs of potential value in the diagnosis of such disorder.