Electroencephalogram (EEG), Brain Mapping (EEGq), Cognitive Evoked Potentials (P300) and Psychophysiological Tests allow to diagnose ADHD and thus guide the therapy of children with this disorder.
Clinical Neurophysiology offers techniques that support clinical diagnosis and offer a quantification and grading of ADHD. Likewise, these techniques collaborate in the orientation and therapeutic management of these patients, since they allow a follow-up of the response to the different therapeutic strategies used in these patients.
Neurophysiological tests for the diagnosis of ADHD
Experts in Clinical Neurophysiology have been working in recent years on various diagnostic methods for Attention Deficit Disorder with or without Hyperactivity (ADHD). These neurophysiological tests group 4 different methods:
1) Electroencephalogram (EEG)
The EEG consists of a recording of the brain bioelectrical activity by means of electrodes placed on the surface of the scalp or with a cap. A series of frequencies are obtained that allow us to know the maturational state of the brain and the presence or absence of abnormalities. Although the EEG of the ADHD patient is not specific, we do observe some characteristic features.
EEG is a very useful technique because it allows:
(a) differentiate the presence of epilepsy or other types of neurological disorders.
b) to rule out the presence of epileptiform activity that could contraindicate the use of psychotropic drugs.
2) Quantitative electroencephalogram (EEGq) and brain mapping
Brain mapping provides a graphical presentation of the values obtained in the EEG, which allows us an accurate, quantitative and reproducible estimation of the EEG characteristics. It is performed in a similar way to EEG, although the signal processing is different, obtaining a series of different parameters, such as: absolute power, relative power, mean frequency and coherence, all represented both with numerical values and in a representative visual image.
The findings that are usually found in a patient with ADHD when performing a brain mapping would be:
– an increase in the absolute power of delta bands and in the relative power of delta and theta bands in frontal areas
– a decrease in the mean frequency of alpha and beta in Posterior Areas
In 2013, the US Food and Drug Administration approved the NEBA as the first device for the complementary assessment of attention deficit/hyperactivity disorder (ADHD), based on the quantified electroencephalogram (EEGq) and including the standardized theta/beta ratio, whose results derived from both a medical and psychological evaluation, and is a useful tool to determine whether ADHD is primary, secondary or comorbid to another disorder.
3) Cognitive Evoked Potentials (P300)
It is a positive brain wave obtained at the level of the cortex caused by the cortical response to a stimulus, either visual or auditory, and is also related to attention.
The latency or time of appearance of the wave and its amplitude are evaluated and correlated with the difficulty in cognitive processing. It also allows assessing the response to treatment.
4) Psychophysiological tests
They are performed together with the P300 and obtain the following parameters:
– Reaction time: It assesses the speed in the execution of the response. In the patient with ADHD it will be prolonged.
– Errors of commission: It assesses impulsivity. These are errors that are made when answering and should not be answered.
– Errors of omission: It assesses inattention. These are errors due to not responding to the stimulus when they should do so.
In addition, other neurophysiological tests will also help to differentiate from other types of disorders that can be confused and misdiagnosed as ADHD:
– Polysomnography or sleep study will help to assess the presence of alterations that have an impact on the child’s normal rest (respiratory, nocturnal leg myoclonias, nocturnal epilepsy, parasomnias, etc.) and that manifest with irritability, restlessness and hyperactivity or inattention behaviors. The child does not usually present somnolence.
– The auditory evoked potentials will allow us to know the existence of auditory losses that manifest as false inattention or difficulty in the language area.