Phenylketonuria: MR imaging of the brain with clinical correlation

Article Abstract:

Phenylketonuria (PKU) is a genetic disease that results in an enzyme deficiency. The enzyme is necessary to convert phenylalanine, an amino acid, into tyrosine, another amino acid. The result of PKU is an accumulation of phenylalanine in the tissues. Mental retardation and neurologic disorders can result if PKU is not treated promptly after birth. Although much is known about PKU, the actual pathology of the disease as it affects the brain is not well understood. Reduction of myelin (the protective layer that surrounds nerves) is often found. Some studies have shown changes in the gray matter of the brain in PKU patients. This study examined the amount of loss of white matter myelination and gray matter changes in 15 patients with PKU, using magnetic resonance (MR) imaging. These results were compared with the extent of mental retardation resulting from PKU and the biochemical severity of the disease to see if a relationship existed between the findings of MR imaging and the severity of disease. MR results showed white matter abnormalities in the posterior part of the cerebrum but no white matter abnormalities in the brain stem, cerebellum or cortex. The abnormalities were found in the front part of the cerebrum in severe cases. There was no correlation between white matter abnormalities as detected by MR and IQ (intelligence quotient) score. No correlation was found between intelligence and atrophy of gray matter. These results indicate that MR imaging can be used to show the loss of myelination of white matter in patients with PKU. However, the extent of these losses does not correlate significantly with the clinical severity of the disease. (Consumer Summary produced by Reliance Medical Information, Inc.)

Usage, Abnormalities, Physiological aspects, Phenylketonuria, Brain abnormalities, Brain diseases, Metabolic, Metabolic brain diseases

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Abnormal corpus callosum: a sensitive and specific indicator of multiple sclerosis

Article Abstract:

Multiple sclerosis (MS) most often affects young adults. It is evidenced by abnormal patches on the brain and spinal cord, with symptoms including tremor and paralysis. Magnetic resonance imaging (MRI) is a diagnostic technique that uses the magnetic properties of elements to produce images of tissues and organs. MRI has been found to be useful in evaluating and diagnosing brain and spinal cord abnormalities associated with MS, but it often cannot distinguish between lesions that are related to MS and lesions that are not related to MS but have a similar appearance. An MRI finding that more specifically indicates MS would be desirable. It has been reported that the corpus callosum (CC), a structural part of the brain connecting the two hemispheres, shows specific changes on MRIs of patients with MS. This study reviewed images of the CC obtained from 42 MS patients and 127 patients with other brain abnormalities to determine whether there were any specific changes in the CC of MS patients that could be used in diagnosing the disease. The callosal-septal interface (CSI), the area where the CC and the septum pellucidum meet, was abnormal on MRI in 39 of 42 (93 percent) of the MS patients. Only three of the 127 (2.4 percent) non-MS patients exhibited such abnormalities. These results indicate that magnetic resonance imaging of the CC can be both highly sensitive and specific in detecting abnormalities that are indicative of MS. (Consumer Summary produced by Reliance Medical Information, Inc.)

Evaluation, Multiple sclerosis, Corpus callosum

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Wallerian degeneration after cerebral infarction: evaluation with sequential MR imaging

Article Abstract:

Wallerian degeneration is the anatomic disruption of the peripheral processes of nerve fibers which occurs after they are severed or after injury or death of their cell body. In this study the pattern of degeneration which occurs throughout the nervous system as a result of a cerebral vascular accident or stroke is observed through the use of magnetic resonance imaging techniques (MRI). MRI is the noninvasive use of strong magnetic fields and radio frequency energy to produce clear images of internal structures of the body (e.g., portions of the brain). The current study follows the process of wallerian degeneration from the earliest periods after an acute stroke to progression of the pattern of degeneration into the peripheral nervous system months later. Forty-three patients between the age of 29 and 81 were observed with MRI. The original infarct (stroke) was seen and documented in all but one patient. The pattern of brain damage in these patients is presented and the signal which was detected from the damaged tissue was found to become extremely intense (hyperintense signal abnormalities) with the passage of time. The changes in signal intensity associated with neural damage is hypothesized to be related to changes in chemical structure of the (myelin) nerve cells during wallerian degeneration.

Case studies, Nervous system, Cerebrovascular disease, Cerebrovascular disorders, Nerve degeneration, Cerebral embolism and thrombosis, Cerebral embolism, Cerebral thrombosis, Brain infarction

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