ABSTRACT
Inborn errors of metabolism [IEM] are common throughout the Middle East, presumably because of the relatively high rates of consanguinity. Disorders of inborn errors of metabolism that affect the CNS are divided according to MRI picture into disorders involving grey or white matter or both. Only very few studies on inborn errors of metabolism have been done in Egypt. However, with the introduction of MRI and increasing awareness of the disease, more and more cases of metabolic diseases are being diagnosed. Many of these diseases if detected early can be cured and MRI might play a vital role in its early diagnosis. MRI has virtually replaced all other imaging modalities including CT in the evaluation of white matter diseases due to its excellent gray-white matter resolution and multiplanar imaging capability. The aim of this work is to identify the pattern of white and grey matter involvement in some neurometabolic diseases and to evaluate the role of MRI as an investigative modality in inborn errors of metabolism and to document its value in early diagnosis and hence management. This is a descriptive study done among 800 patients suspected of having an inborn error of metabolism and referred to the clinic of inherited metabolic disease at Cairo University Children Hospitals, at the centre of Social and Preventive Medicine. Only fourteen patients were found to have the diagnosis of metabolic disease and abnormal findings on MRI. Out of 14 cases, 11 were males [78.6%] while 3 [21.4%] were females. At presentation, the mean age +/- SD of the patients was 4.36 +/- 3.775 years, and their ages ranged from 9 months to 16 years. Four cases [28.5%] were diagnosed as Leigh disease, 4 cases [28.5%] as metachromatic leukodystrophy, 2 cases [14.2%] as Canavan disease, 1 [7.1%] as methylmalonic academia, 1 [7.1%] as Vander Knappe disease, 1 [7.1%] as mucolipidosis, and one [7.1%] as Wilson disease. Clinical presentation included positive consanguinity in 9 cases [64.3%], other sibs affected in 5 cases [35.7%]. Global developmental delay in 3 cases [21.4%], and developmental regression in 11 cases [78.6%]. Attacks of disturbed conscious level with metabolic acidosis were encountered in 5 cases [35.7%]. Seizures were encountered in 6 patients [42.9%] [four of them were generalized tonic clonic, one was multifocal clonic and one was hemifocal]. All types achieved good control on one or two antiepileptic drugs. Extrapyramidal symptoms were present in 5 cases [35.7%], and ataxia in 2 cases [14.3%]. On examination there was spasticity in 11 cases [78.5%], while only 3 patients [21.4%] were hypotonic. On measuring the skull circumference, 6 patients [42.9%] had microcephaly, 4 patients [28.5%] were macrocephalic and 4 cases had normal skull circumference. Fundus examination was done and revealed optic atrophy in 2 cases [14.3%]. MRI was a guide in reaching a proper diagnosis in these cases, definitive diagnosis was done by tandem mass spectrometry [TMS], enzymatic essay and skin or gingival biopsies according to each case. When properly used, MRI pattern recognition approach in conjunction with the other imaging tools can be very useful for separating the complex group of metabolic disorders into more manageable groups. Indeed, sometimes this approach allows a specific diagnosis to be made. Although the pattern of disease in MRI is not often specific, the distribution may suggest a differential diagnosis that may be pursued by increasingly specific enzyme analysis