Cretinism, endemic neurology

Severely endemic areas have a high prevalence of cretinism, other neurological dysfunctions and intellectual impairment. The prevalence of these manifestations declines sharply after implementation of an iodization program. 

What can the neurological data contribute to understanding of the pathophysiology of the brain in endemic cretinism Can neurological observations tell which systems are involved and when that Involvement occurred ... 

The therapeutic strategy should rely on preventative measures. Endemic goitre and endemic cretinism as well as more subtle deficits of neurological function associated with iodine deficiency have been shown to be prevented with adequate iodine prophylaxis. Adequate and continuous supply is the key to successful prevention programmes. 

However, some observations from other goiter endemic areas did not support the selenium-iodine hypothesis. First, selenium deficiency in Central Africa is not as severe as in the selenium- and iodine-deficient areas of Tibet, where the neurological and not the myxedematous type of cretinism is most frequent (Moreno-Reyes et al, 1998) Figure 71.4. 

DeLong, G.R., Stanbury, J.B. and Fierro-Benitez, R. (1985). Neurological signs in congenital iodine-deficiency disorder (endemic cretinism), Dev.Med Child Neurol 27, no. 3, pp. 317-324. 

Endemic cretinism (neurologic cretinism) Congenital hypothyroidism Myxedema (adult hypothyroidism)... 

The findings suggest that iodine deficiency has an early effect on neuroblast multiplication and if so this could be important in the pathogenesis of the neurological form of endemic cretinism (8) (23). 

We know that there are two extreme types of endemic cretinism, neurological and myxedematous, that there are regional variations in the frequency of the two types, that there are mixed types in some individuals and areas and, finally, that there is neurointellectual impairment in non cretin individuals in severe endemic areas (1-12). 

What is needed now is a comparison of brain pathology in neurological cretinism and cerebral palsy and in myxedematous cretinism and sporadic congenital hypothyroidism there is also a need for study of the brain in endemic mental retardation. 

We know very little about the pathology of the ear. And yet, hearing loss is a major component of cretinism. Old data summarized by Koenig (21) indicated that neurological endemic cretins present middle ear abnormalities characterized by hypertrophic bone changes of the promontorium, deformation of the ossicles, distorsion of the oval and round windows and thickening of the mucous membrane of the tympanic cavity. No data are available for the inner ear. 

What we need is more precise information, obtained with modem methods of investigation, on the structure and ultrastructure of the middle and inner ear in neurological and myxedematous cretins. Such findings should then be compared with data concerning sporadic congenital hypothyroidism and congenital infections. There is undoubtedly scope for further work in audiometry and auditory evoked potentials in endemic and sporadic cretinism. 

Swiss authors (2, 17) reported that neurological cretins have hyperplastic, colloid, multinodular goiters similar to those seen in non cretin individuals in the same area. They showed that myxedematous endemic cretins have thyroid atrophy and sclerosis. As a consequence of their thyroid failure, myxedematous cretins also have hyperplastic pituitary glands. 

Several points emerge from a neurological analysis of endemic cretinism ... 

I have previously described the neurological features of endemic cretinism (1,2) and will summarize them briefly here. The three major features are deafmutism, mental deficiency and motor disorders. Deafness, if complete, results from cochlear dysfunction. Partial hearing loss may be associated with limited dysarthric speech, probably reflecting an element of cerebral cortical dysfunction. 

Within the broad syndrome of neurological endemic cretinism, the severity of particular features may vary widely. For example, deafness may be minimal or may be complete spasticity may be prominent or may be subtle speech may be impossible, or may be functional and only mildly dysarthric, etc. Within sibships, the overall pattern tends to be more similar than is seen if unrelated individuals are compared. These observations argue that the genetic substrate influences the expression of endemic cretinism. This has recently been clearly demonstrated by Held, et al. (3)... 

The reason for describing our case is that his neurological deficits were indistinguishable from neurological endemic cretinism, and were irreversible despite early treatment, presumably because there was the added factor that the mother was hypothyroid during pregnancy. 

Guinea. The most detailed account of the neurology of endemic cretinism in recent times is provided by DeLong (4) on endemias in Zaire, Ecuador and China. 

Hornabrook RW. Neurological aspects of endemic cretinism in Eastern New Guinea. In Hetzel BS,... 

Although the materials studied in the present paper and the above mentioned differences were relatively small, the morphometric changes in the brains of certain iodine deficient fetuses are definite. The results suggest that prenatal iodine deficiency exhibits certainly a depressive influence on the brain in some of the fetuses in the endemic goiter and cretinism areas retarding its development. This might account for the neurological deficit of cretinism or cretinoid syndrome. 

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