Cretinism neurological abnormalities

With respect to experimental studies in rats born from mothers with severe iodine deficiency, several neurological abnormalities have been demonstrated. The progeny has susceptibihty to audiogenic seizures, associated with irreversible hearing defects, similar to those found in neurological cretinism. Several areas of the brain, such as the cerebral cortex, hippocampus and cerebellum, present morphological abnormalities (Martinez-Galan et al, 1997). 

The neurological abnormalities observed in neurological cretinism seem to be caused by maternal hypothyroxinemia during the first period of brain development, early in pregnancy. In iodine deficiency the maternal plasma T4 is low, even if plasma T3 and TSH are normal. 

The defect in vestibular function is usually parallel to the defect in hearing in neurological cretins. Wang found 95.1% of neurological cretins had abnormal vestibular response. 

In conclusion, classical myxoedematous cretinism is found in the Qinghai endemia. Nevertheless, all cretins displayed degrees of neurological abnormality. In this endemia the traditional classification was not useful and the clinical syndrome of cretinism was modified by the severity and duration of ongoing hypothyroidism. The factors that influence postnatal thyroid function are unidentified, but the finding of thyroid atrophy implies an autoimmune process. 

Neurological cretinism is caused by severe iodine deficiency during pregnancy and is characterized by severe mental retardation and neurological and motor abnormalities it can be corrected by the administration of iodine before conception. The clinical features of cretinism and CH are different. 

Neurological cretinism has a characteristic standing posture characterized by flexion of the neck and flexed hips and knees with abductor tightness (Hollowell and Hannon, 1997). In this situation, the trunk tilts forward, the feet are flat and everted, and the gait is broad-based and knock-kneed. The arms are often held in a curious posture with shoulders abducted and the elbows and wrists flexed. Most individuals have characteristic gait disturbances ranging from an abnormal posture and rhythm to an inability to walk. 

Iodine is a trace element essential for the synthesis of thyroid hormones. Iodine deficiency is well-recognized as a cause of goiter, but the most serious consequence is cretinism. Apart from neurological and motor abnormalities, some of the ocular features of hypothyroidism described subsequently may occur. 

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. 

In studies in China, lower intelligence quotient scores showed a relationship with the detection by audiometry of nerve deafness, and the presence of abnormal neurological signs similar to the pattern observed more obviously in overt neurological cretins. It was concluded that iodine deficiency results in a shift of the entire population distribution of cognitive skills to a lower level. ... 

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