Is demyelination a feature of maple syrup urine disease?

To determine whether disturbance of myelination is a pathophysiologic feature in patients with treated maple syrup urine disease (MSUD), neurophysiologic studies were performed in 10 MSUD patients ages 4-16 years. Afferent and efferent pathways were studied by visual evoked potentials, somatosensory evoked potentials, motor evoked potentials, stance-stabilizing reflexes, and peripheral nerve conduction velocity. Magnetic resonance imaging was used to detect possible cerebral white matter abnormalities. Visual evoked potentials were normal in all patients. There was only slight prolongation of central afferent and efferent conduction times and the long latency component of the stance-stabilizing reflexes. Peripheral nerve conduction studies revealed reduced sensory nerve conduction velocity in 3 patients. The neurophysiologic findings were not consistently correlated to the neurologic outcome of the patients. Magnetic resonance imaging did not reveal major abnormalities and demonstrated bilateral periventricular high intensity periventricular signals on T2-weighted images in 4 of 10 patients. It is concluded that dysmyelination is not a major pathophysiologic feature in patients with MSUD.