To describe the phenomenology of hyperkinetic movement disorders (HMD) in patients and its association with immunosuppressant drugs and cefepime.

HMD are a frequent complaint in inpatients and among their several possible aetiologies there are structural lesions to the CNS, seizures, metabolic disturbances and current medications (i.e. cefepime, or immunosuppressants (IS) such as calcineurin inhibitors (CNInh)).

Retrospective review of the medical records of inpatients consecutively evaluated for HMD between 2008 and 2018. Phenomenology of HMD: distribution, triggers, movement features as well as clinical variables such as the presence of a CNS lesion, seizures, EEG-MRI abnormalities, liver and renal failure (RF) were documented.

Of 101 patients (mean age 60y.o.) 85 presented myoclonus, 19 tremor and 21 chorea-dyskinesia. Myoclonus was mainly reflex (55%) and postural (60%), its distribution: unilateral (24%), focal (19%), segmental (43%) or generalized (39%). CNS injury was present in 49% of patients; stroke 47%, tumour 6%, seizures/non-convulsive status epilepticus (NCSE) 48%, renal 53% and liver failures 30%. Sixty-eight percent showed EEG abnormalities, 18% leukoaraiosis, 10% showed T1W bi-pallidal hyperintensity on MRI. Pharmacology: 24% received Cefepime and 47% immunosuppressant (36% CNInh: tacrolimus/cyclosporine). Mean time of IS use was 420 days; mean daily dose of tacrolimus 1,64mg and serum titters 4,96ng/mL. Thirty six patients recovered after IS/Cefepime withdrawal (drug-induced): those cases presented significantly more myoclonus (97%vs78%,p=.01), postural lapses (41%vs18%,p=.01), use of Cefepime and CNInh, higher CNInh-dose (2.9mg vs 0.95mg,p<.01), prolonged use CNInh (807vs206 days,p=.01), associated with seizures/NCSE and RF. A regression model showed that age, drug-induced condition and daily dose of CNInh predicted myoclonus development (accounting for 28% of variance).