Two cases of acute hemichorea-hemiballismus could be linked to AstraZeneca’s COVID-19 vaccine and “highlight the need for careful clinical observation to aid pharmacovigilance efforts”, Sydney-based neurologists say.

The “consecutive” and “strikingly similar” cases were seen in two 80+ year old men who presented to the University of Sydney’s Central Clinical School within 40 days of their first ChAdOx1 injection, had no history of movement disorders and resolved symptoms on steroids, University of Sydney neurologist, Dr Elie Matar and colleagues wrote in a letter to Movement Disorders.

Patient 1, an 88-year-old, awoke with involuntary movements of the arm, leg and face 16 days after his first dose, while Patient 2, who was 84, noticed an “acute onset of involuntary hyperkinetic movements of the left upper and lower limbs” while watching TV, which worsened through the evening and impacted his sleep, 40 days post first-dose, the authors reported.

Patient 1 had treated hyperlipidaemia, hypertension and gout and Patient 2 had a history of asthma, allergic aspergillosis and primary orthostatic hypertension and treated colorectal, oesophageal and prostate cancers in remission, the authors noted.

Neither patient had any other neurological or systemic symptoms and both had “continuous, non-patterned, small-amplitude movements of affected arms and legs with superimposed proximal irregular large-amplitude movements consistent with hemichorea-hemiballismus” on neurological examination, they wrote, although case 1 did show mild parkinsonism on their contralateral side.

With bloods and MRI showing no alternative cause, Dr Matar and colleagues attributed the symptoms to an autoimmune reaction sparked by the vaccine’s spike protein and patients were given a short course of steroids (3 daily doses of 1 g intravenous methyl-prednisolone).

Patient 1 had a “prompt and significant resolution within 24 hours of the first dose”, while Patient 2 had “partial spontaneous improvement after the first day”, and complete resolution after three days of corticosteroids, the authors wrote.

Their results are “in line with a recent report of a patient with worsening levodopa-induced dyskinesias after receiving the BNT162b2 (Pfizer/BioNTech) mRNA vaccine and preclinical studies supporting a role of neuroinflammation in levodopa-induced dyskinesia generally”, they wrote.

The spike protein may have induced a focal immune-mediated endotheliopathy that could account for the patients’ presentations.

Despite this, the authors stand by COVID-19 vaccines’ safety and efficacy, noting that “idiosyncratic neurological reactions after vaccination are rare and tend to be monophasic”.

“These cases highlight the need for careful clinical observation to aid pharmacovigilance efforts and the importance of large epidemiological studies to confirm potential neurological post-vaccination reactions,” they concluded.