Neurological outcome in 22 treated adolescents with hyperphenylalaninemia. A clinical and electrophysiological study.

We examined clinically and electrophysiologically 22 adolescents suffering from hyperphenylalaninemia. Three of 16 treated patients showed slight impairment of proprioception; their examination was otherwise unremarkable. Subclinical deficits were present in the central motor and sensory pathway. In addition, we had evidence of a minor sensory neuropathy: 32% of the 22 patients had subclinical deficits in the visual system. However, in contrast to earlier reports we saw no relation to the degree of metabolic control. Our results suggest that treated adolescent patients with hyperphenylalaninemia show neurological dysfunction that may be related to morphological, as well as pharmacological changes.