Multiple sclerosis in Chile Alvarez G, Castillo JL, Cirdenas M , Frru~iE, Ruiz F, Lavados J . Multiple sclerosis in Chile. Acta Neurol Scand 1992: 85: 1-4.

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So far as we know this series of 68 cases is one of the first clinical accounts of multiple sclerosis in South America. Average age of onset was 30.7 years and female:male ratio was 2: 1. The most frequent initial symptom was motor impairment and less frequent was visual loss. Most affected site of involvement in established cases was the optic nerve. There were no familial cases. The severity of the disease in Chile proved to be the same as elsewhere. N o characteristic clinical pattern peculiar to the region emerged.

Studies of multiple sclerosis in Latin America are not abundant. Not much is known regarding clinical features and course of the disease in t h s geographical area. It is presumed to be much less frequent than in Western Europe or the United States but prevalence data are not easy to obtain. One report (1) gives a figure of about 1.6 cases per 100000 population in Mexico City in 1970; a hospital-based study from the same region however yielded a prevalence of 4.69 per 100000 in 1985 (2). Reports which were not published were quoted in 1975 (3) and gave prevalence ratios of 4.4/ 100000 in Peru, 4/ 100 000 in Brazil, 14 to 17/100000 in Buenos Aires, Argentina, 14/lOOOOO in other parts of Argentina, and 14/ 100000 in Montevideo, Uruguay. No estimates can be given for Chile but it is of note that out of 1915 hospital discharges pertaining to the period 1982 to 1988 in one Santiago hospital there were 66 cases labelled as M S (3.45%), not all of them substantiated however (4). The corresponding figure for amyotrophic lateral sclerosis was 38 cases (1.98%). There have also been studies dealing with the usefulness of electrophysiological and immunological studies (5-7). There are reasons to believe that within certain limits ethnic and geographical factors can have a bearing on the pattern of clinical involvement and severity of the disease (8-12). Based on what appears to be a remarkably low incidence of MS following optic neuritis in Chile (13) (4.3 % after a mean of 9.7 years after onset), and based also on unsubstantiated clinical impression, we had come to believe that MS in this country has a relatively benign impact on those who suffer from it. We present a series of 68 non-consecutive cases drawn from all sources available to us.

G.Alvarez, J. L. Castillo, F. Ruiz, M . CArdenas, E. FaurC, J, Lavados Department of Neurological Sciences, Faculty of Medicine, University of Chile, Santiago

Key words: Chile; multiple sclerosis; epidemiology Dr. Gonzalo Alvarez, Department of Neurological Sciences, Faculty of Medicine, Universidad de Chile, Servicio de Neurologia, Hospital del Salvador, Santiago, Chile

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Accepted for publication May 22, 1991

Material and methods

The records of three large general hospitals with long-standing neurological services were systematically searched: cases known to us in private practice were included. During one year, mid 1988 to mid 1989, a number of patients from various other centres in whom M S was suspected were submitted to visual, auditory, and somatosensory evoked potentials as well as to the determination of IgG index with oligoclonal bands. Those cases in whom these methods aided in the diagnosis were included. The criteria established by Poser et al. in 1983 (14) were followed in diagnosis. All cases, except 3 who died and were confirmed pathologically, were examined personally by two of us (GA or JLC), in a hospital setting or in their homes. Some were under regular supervision in out-patients. This search disclosed 68 cases of definite or probable MS, 45 women and 23 men. Visual, auditory and somatosensory evoked potentials were sought in 46 cases, following the guidelines of the American EEG Society. CSF IgG with oligoclonal bands were studied in 28 cases. These tests were performed in all cases of probable MS and in many known to be definite MS; they were not performed in only afraction ofthe definite MS group. The chi square test was used to compare results with those of other series. Results

There were 46 cases of definite and 22 of probable MS. The sex ratio was 2 female:] male. The average age of onset was 30.7 years (S.D. 10.3) and average duration of disease was 9.2 years (S.D. 7.5). 1

Alvarez et at. It was possible to determine the initial symptom in 64 cases (Table 1); motor deficit in one or more limbs was the most frequent finding. The most frequent clinical combination involved 4 or more sites in the CNS; other forms are shown in Table 2. The most frequently affected site was the optic nerve and the less frequent were cerebral her?lispheres (Table 3). In one case motor impairment was not recorded; motor disability is set out in Table 4 as in Shibasaki et al. (9). Discussion

The sex ratio and average age at onset were unremarkable but it is worth noting that in a country where families tend to be numerous there were no cases of familial occurrence in spite of systematic questioning; this is in contrast with some European series (9, 15) and in agreement with Asian ones (9, lo), although in a Japanese series which included possible cases of MS (17) a 2% familial incidence was found. Following Poser et al. (14) electrophysiological and immunologcal criteria were employed in diagnosis so that comparisons with other series in which this was not the case and whch were moreover consecutive must be seen in this light. Also, cases of spastic paraplegia in which only the history and clinical examination were available were excluded. It must be pointed out that cases of human T-cell lymphotropic virus Type I presentation with spastic paraplegia have recently been found in Chile (18). Thus, cases of spinal progressive forms of MS may have been excluded. Outstanding clinical features peculiar to the present series is the frequency of motor weakness and the paucity of visual loss as initial symptoms (Table 1). Comparison with other series of MS definite or probable shows no figure as high as 58% of

motor weakness as initial symptom so that significant differences appear with respect to all series except Malaysia (10) and one of the Japanese ones (20). Visual loss in one or both eyes as initial symptom was seen in only 14% .of our cases, in keeping with the observation that few cases of optic neuritis go on to develop MS in Chile (13) and in this respect there are also significant differences with most other series. However, in a Danish series (16), although optic neuritis as a whole was relatively infrequent as an initial symptom (22.5% of 383 cases) it was nevertheless the most common presenting feature when patients were under 25 years of age. We have arranged the clinical forms taken by the disease as in Shibasaki et al. (9), adding the Malaysian series (Table 2). In their paper Shibasaki et al. noted that the optic-spinal-brainstem and opticspinal forms were more common in Orientals than in Caucasians. However when our series is compared to others, ddTerences reaching statistical significance are found scattered in various clinical forms without systematic patterns so that tendencies pointing to ethnic variations do not emerge. Electrophysiological criteria were taken into account in the determination of sites of lesion, which other series did not (Table 3). Shibasaki et al. (9) commented upon a more frequent incidence of cerebellar symptoms amongst Caucasians than amongst Orientals. The present Chilean series resembles all others in a high rate of involvement of the optic nerve but this was often an electrophysiological finding. Regarding sites of lesion, differences with other series were also established in random fashion. We were especially interested in ascertaining the degree of motor disability in our series, including Scottish (21) and Danish (16) ones (Table4). The average duration of the disease in these two latter series was longer; the motor incapacity of their patients was adapted to the categories of Shibasaki

Table 1. Initial symptoms in series of definite and probable MS (%)*(a)

Number of patients Motor weakness Visual loss Sensory symptoms Gait disturbance Diplopia Sphinter disturbance Speech disturbance Vertigo Clumsy hand Facial palsy

Present series 64 58 14 23 14 22 5 2

3 3 0

Hawaii Oriental

(81 15 20 p

Multiple sclerosis in Chile.

So far as we know this series of 68 cases is one of the first clinical accounts of multiple sclerosis in South America. Average age of onset was 30.7 ...
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