Mismatch Negativity in essential tremor: role of age at onset in pre-attentive auditory discrimination.

OBJECTIVE: To investigate whether pre-attentive auditory discrimination is impaired in patients with essential tremor (ET) and to evaluate the role of age at onset in this function. METHODS: Seventeen non-demented patients with ET and seventeen age- and sex-matched healthy controls underwent an EEG recording during a classical auditory MMN paradigm. RESULTS: MMN latency was significantly prolonged in patients with elderly-onset ET (>65 years) (p=0.046), while no differences emerged in either latency or amplitude between young-onset ET patients and controls. CONCLUSIONS: This study represents a tentative indication of a dysfunction of auditory automatic change detection in elderly-onset ET patients, pointing to a selective attentive deficit in this subgroup of ET patients. SIGNIFICANCE: The delay in pre-attentive auditory discrimination, which affects elderly-onset ET patients alone, further supports the hypothesis that ET represents a heterogeneous family of diseases united by tremor; these diseases are characterized by cognitive differences that may range from a disturbance in a selective cognitive function, such as the automatic part of the orienting response, to more widespread and complex cognitive dysfunctions.

Attention in essential tremor: evidence from event-related potentials.

Clinically subtle executive dysfunctions have recently been described in essential tremor (ET), though the presence of attentional deficits is still unclear. We investigated the psychophysiological aspects of attention in ET, using event-related potentials (ERPs). Twenty-one non-demented patients with ET and 21 age- and sex-matched healthy controls underwent a psychophysiological evaluation. P300 components and the Contingent Negative Variation (CNV) were recorded. The latencies and amplitudes of the P3a and P3b subcomponents and CNV areas were evaluated. Possible correlations between clinical parameters and ERP data were investigated. P3a latency was significantly longer in the ET group (p < 0.05), while no differences emerged between patients and controls in P3b latency. No differences were observed between the two groups in the CNV parameters. ET patients display a difficulty in the response to novelty and in the recruitment of prefrontal attentive circuits, while the memory context-updating process appears to be spared. This selective cognitive dysfunction does not appear to interfere with the attentional set linked to the expectancy evaluated during a complex choice-reaction time task, which is preserved in ET. This multitask psychophysiological approach reveals the presence of a peculiar attentional deficit in patients with ET, thus expanding the clinical features of this disease.