[Comparative clinical study of patients with Parkinson disease and essential tremor]

Some studies have shown that essential tremor (ET) occurs more frequently in Parkinson disease (PD) patients and opposite, suggesting these disorders are pathogenically related. To evaluate this relationship, we have compared some clinical features between patients with ET and with PD.

PD patients (N = 134) and patients with ET (N = 46), were collected from Bajo Aragon district. A diagnosis of PD was taken according to the United Kingdom Parkinson's Disease Society Brain Bank criteria. A diagnosis of ET was confirmed on the basis of Rajput et al criteria.

A statistically significant higher number of females with ET were founded (p < 0.05). An earlier mean age at tremor onset was observed in ET patients (p < 0.0001). More than half ET patients had a positive had a positive family history of ET (p < 0.0001). Interval period between tremor onset and first medical consulting was higher in ET patients (p < 0.01). Depression was more common in PD patients (p < 0.05).

A statistically significant differences about mean age at tremor onset, duration of illness, positive family history of ET, one side or bilateral tremor onset and frequency of depression were observed between these two disorders. The differences found in clinical features and others described previously about necropsy findings and TEP with 18F-Dopa studies, don't support the possibility that PD and ET are pathogenically related.