ADD, NF1 clinically similar but neurophysiologically different
Despite their considerable similarities in terms of clinical features, attention deficit disorder (ADD) and neurofibromatosis type 1 (NF1) have important neurophysiological differences, particularly in perceptual categorization and response inhibition, a new study shows.
The study included 29 patients with either NF1 (n=13) or ADD (n=16). Only those diagnosed according to the NIH and ICD criteria were included. Of the ADD patients, six were taking methylphenidate or atomoxetine medication. An additional 17 children without psychiatric conditions were included as controls.
Participants underwent a standard Go/No-go task requiring them to respond adequately to a “press” or “stop” stimulus. Electroencephalogram (EEG) readings during the onset of the stimuli were recorded. Only those for correct responses were considered.
ADD patients (51.8±15.8 percent) had more false alarm response in the No-go tests compared with controls (31.8±16.5 percent; p=0.003) and patients with NF1 (34.8±19.8 percent; p=0.03). The difference between the NF1 patients and the controls was insignificant (p=0.64).
There was a significant difference among the three groups in terms of the correct responses in the Go tests (ADD: 92.9±7.8 percent; NF1: 90.9±10.3 percent; controls: 97.9±2.7 percent; p=0.03). Moreover, the difference between the NF1 patients and the controls were significant (p=0.01).
The NF1 patients (491±135 ms) also had significantly slower reaction times in the Go tests compared with ADD patients (415±55 ms; p=0.02) and controls (416±98 ms; p=0.02).
Neurophysiological data showed that NF1 patients had lower P1 amplitudes compared with ADD patients (p=0.01) and controls (p=0.02). The difference between controls and ADD patients was insignificant (p=0.66).
ADD patients had a lower central P3 (cP3) peak compared with controls (p=0.001) and NF1 patients (p=0.02) in the No-go tests. On the other hand, NF1 patients showed a significantly later cP3 peak compared with ADD patients (p=0.007) and controls (p=0.05) in the No-go tests.
The differences highlighted in the study show that both clinical and cognitive-neurophysiological measures are important in assessing these disorders.