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It has been suggested that the cerebellum plays a role in the event-based timing of synchronized repetitive movements. We hypothesized that regularity of rhythmic movements in essential tremor (ET) is impaired, since several lines of evidence suggest the involvement of the cerebellum in the pathomechanism of ET. To test this assumption, we examined the regularity and the maximum frequency of auditory paced repetitive movements at slow and fast stimulus rate in 34 ET patients. Variability of rhythmic finger tapping and alternating hand movements, defined by the standard deviation of movement offset before or after the pacing signal, was significantly higher compared to healthy controls. Timing of rhythmic movements of the two hands was disturbed to the same degree. Our results suggest a severe deficit of event-based rhythm generation on both sides in ET, supporting the presumed bilateral cerebellar dysfunction in this disorder.

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Vitamin B12 deficiency causes haematological and neurological diseases. Subacute combined degeneration (SCD) of the spinal cord is characterized by degeneration of the posterior and lateral columns. We report two cases of SCD induced by nitrous oxide (N2O) anaesthesia. In both cases magnetic resonance imaging (MRI) of the spinal cord showed symmetric, reversible changes in the posterior columns, correlating well with patients' symptoms.