Event-related potentials in posttraumatic headache

To assess impairment of cognitive functions occurring in patients with posttraumatic headache as a consequence of a minor cranial trauma in the absence of organic damage involving the central nervous system.

The term posttraumatic syndrome defines a stereotypic set of symptoms following traumatic brain injury that are subjective and varied. A deficit of cognitive function and impairment of the rapid processes of learning, attention, and short-term memory have frequently been identified. Moreover, headache is the most frequent symptom reported by the patients. Due to the nature of the symptoms, a great limitation in defining the posttraumatic syndrome is represented by the lack of methods and diagnostic tools that allow quantification of the subjective disturbances and evidence of the signs indicative of central nervous system involvement in this pathological condition.

Twenty-five subjects (16 women, 9 men; mean age, 28 +/- 9 years) were examined between 3 and 6 months after the traumatic event. The P300 event-related potential was recorded by an odd-ball paradigm with an acoustic modality. The patients underwent electroencephalography and brain stem auditory evoked potentials; magnetic resonance imaging was performed to exclude the presence of cerebral lesions.

The mean latency of P300 was increased in both central electrodes (Cz and Pz) in patients with posttraumatic syndrome compared with controls (P<.001); assuming the value of mean +/- 2 SD was the cutoff point between normal and abnormal results, the P300 latency results were altered in 13 patients (52%). In the patient group, a significant correlation was demonstrated between Zung Depression Scale score and P3 and N2 wave latencies (r = 0.54, P <.004; r = 0.56, P<.003) and between Zung Anxiety Scale scores and P3 wave latencies (r = 0.46, P<.02).

These data suggest the usefulness of the P300 event-related potential in evaluating cognitive disturbances in patients affected by posttraumatic syndrome. Alteration of cognitive potential in such patients, even in the absence of lesions detectable by neuroimaging, indicate the functional impairment of specific cerebral areas that can occur after a traumatic event.