Iodine deficiency is a common cause of preventable brain damage and mental retardation worldwide, according to the World Health Organisation. It results in structural and metabolic brain abnormalities which may be visible on nuclear magnetic resonance (NMR) techniques. Currently, however, there has been no review of the appearance of these changes on NMR images. We conducted a systematic review on the literature until March/2012 to determine the appearance of brain abnormalities on NMR, caused by iodine deficiency.
From 1332 papers assessed, 24 studies were selected which confirmed their findings directly using magnetic resonance imaging (MRI) and/or magnetic resonance spectroscopy (MRS). 23 of them were in humans and involved 130 subjects 33 of which had primary hypothyroidism, 83 had congenital hypothyroidism, 3 had endemic cretinism and 11 had subclinical hypothyroidism. Within the selected studies there were various types of brain abnormalities found, with pituitary abnormalities (14/24 studies) and cerebellar atrophy (3/24 studies) being the most prevalent. The studies were small, being the mean sample size 6, the median 3, the range 35, and 11 studies each presented case report data on 1 individual only.
Work is required to determine whether the effects of a low-iodine intake on the brain can be studied using NMR methods and to improve spatial resolution in the imaging of small brain areas, such as the pituitary gland and subtle atrophy changes (e.g. in the hippocampus and cerebellum).