Bilateral symmetrical dystonia secondary to aripiprazole

To the Editor

Mrs A is an 88-year-old woman admitted to an inpatient Rehabilitation unit for a reconditioning programme, on a background of chronic schizophrenia, depression, ischaemic heart disease and bronchiectasis.

On examination, Mrs A displayed hypomimia, bradyphrenia, bradykinesia and bilateral upper limb ‘cogwheeling’, consistent with iatrogenic Parkinsonism, related to long-term anti-psychotic medication usage.

During this admission she was seen by the psychogeriatrics service and her quetiapine was changed to aripiprazole, to improve symptoms of sedation and avolition. The dose was gradually increased to 7.5 mg daily. Twenty-three days later, she developed sudden onset of bilateral, symmetrical, dystonic, equinovarus posturing of the feet and ankles. The positioning was rigid – Grade 4 on the Modified Ashworth scale (Harb and Kishner, 2021); as such, the posturing could not be corrected actively by the patient, nor passively by the examiner.

We contacted the prescribing psychogeriatrician with our provisional diagnosis of anti-psychotic-induced dystonia. She concurred and advised immediate cessation of the aripiprazole. We considered administration of a pro-cholinergic, muscarinic antidote, Trihexyphenidyl; however, as the patient was not experiencing discomfort at that stage, we elected to simply discontinue the likely causative agent and monitor the patient.

At 48 hours post onset, both feet remained in equinovarus posturing at rest. However, at the right ankle, we were able to passively correct the inversion to neutral and partially correct the equinus posturing. At the left ankle, we were able to fully correct the inversion into 5 degrees of eversion and almost completely correct the equinus posturing.

We prescribed padded resting splints to hold the feet as close as possible to a neutral position, to prevent musculotendinous shortening while awaiting resolution of her symptoms.

After 1 week, the decision was made to administer botulinum toxin to the lower limb muscles, given minimal clinical improvement in the bilateral ankle dystonia and increasing patient distress. A total of 400 U of Botulinum toxin type A were administered into extensor hallucis longus, tibialis posterior, gastrocnemius (medial and lateral heads) and soleus. Injection accuracy was facilitated via a neuromuscular stimulator.

At the time of writing, the patient remains hospitalised, unable to independently transfer, mobilise or perform activities of daily living, as a result of the impact of her multiple active co-morbidities. After meeting with the family and the patient, we planned to transfer the patient to a residential aged care facility, with community psychogeriatric follow-up.

Upon review of the literature, we noted that focal dystonias were overall less common with the second-generation antipsychotics and that there were only a few reports of aripiprazole-induced dystonia (Desarkar et al., 2006; Sanghadia and Pinninti, 2007). We believe this is the first reported case of sudden onset, bilateral, symmetrical, lower limb dystonia.