PATHOLOGY OF SYMPTOMATIC TREMORS

Symptomatic tremors are labeled in the literature under different name s including rubral tremor, midbrain tremor, thalamic tremor, myorhythm ia, Holmes' tremor, cerebellar tremor, and goal-directed tremor. The m ost common tremor is a delayed-onset postural and action tremor with a low frequency of 3 Hz and a proximal distribution. Resting irregular tremor is sometimes present. Mild cerebellar dysmetria is often detect ed. The lesions are mainly located in the thalamus, the brain stem, an d the cerebellum, with secondary interruption and degeneration of vari ous pathways and olivary hypertrophy. The more consistent lesions are found in the cerebello-thalamocortical and dentato-rubro-olivary pathw ays. The role of superimposed dysfunction of the nigrostriatal system may account for the rest component. The role of the basal ganglia in t he emergence and control of tremor is poorly understood.