INTRODUCTION: Tremor is the most frequent and disabling neurological side effect 
under Calcineurin inhibitor-induced immunosuppression, but no studies have 
defined its phenomenology, severity, distribution, the impact on quality of 
life, as well as of other neurological symptoms associated.
METHODS: 126 consecutive kidney-transplanted patients, under treatment with 
Cyclosporin A, Tacrolimus and non-Calcineurin inhibitors, within therapeutic 
range, were enrolled. Participants underwent a deep neurological examination by 
two blinded to the treatment raters, and a blood sampling to assess plasmatic 
immunosuppressant level and nephrological function tests. Tremor and cerebellar 
signs were scored according to the Fahn-Tolosa-Marin and the SARA scale. 
Parkinsonism was excluded applying the UPDRS (part III).
RESULTS: Tremor was more common and severe in the Tacrolimus group, similar to 
impairment in ADL. Regardless of treatment, tremor involved both upper and lower 
limbs and was activated by action, but in about 50% of cases presented in action 
and rest condition. Plasmatic level of Tacrolimus was higher in patients with 
tremor than in those without, while cholesterol was significantly lower. 
Cerebellar and neuropathic signs were overall mild and were not significantly 
different across the three groups comparing patients with and without tremor.
CONCLUSIONS: Non-Calcineurin inhibitors such as Sirolimus have the lowest 
propensity to induce tremor and with a milder severity, while Calcineurin 
inhibitors, especially Tacrolimus, the highest, and regardless of the 
formulation. Plasmatic concentration of Tacrolimus was higher in tremulous 
patients; further research needs to validate the role of cholesterol plasmatic 
concentration in predicting the occurrence of tremor in patients on Tacrolimus.