21st June 2023

A 45-year-old woman attended the Movement Disorders Clinic with a 1-year history of worsening motor symptoms

A 45-year-old woman attended the Movement Disorders Clinic with a 1-year history of worsening motor symptoms. Her initial symptoms included difficulty walking, which progressively worsened and caused her to fall. She started to develop dance-like movements, which included head bobbing and extremity tremors. There was no numbness, urinary incontinence or memory impairment.

Her father was estranged, but she was aware that he had died some years ago, aged 56; however, she does not know the details of this.

On examination, there were mild abnormal movements in her face, arms, and legs. She had asymmetric bradykinesia, which was worse on the left than on the right side. She had symmetrical rigidity. She had a slow, shuffling. She had a negative Romberg sign and no cerebellar signs.

Which of the following options is the most likely cause of her decline?