O.B. is a 74-year-old engineer who was referred to a neurology clinic because of gait problems and falling episodes. His motor problems had started 1 year before, when he noticed more rigidity in his right upper and lower limbs and a tendency to fall toward the right. On neurological examination he showed hypophonia, slight loss of facial expression, intermittent resting tremor in his right hand, mild cogwheel rigidity restricted to the right side, mild slowing on finger tapping, hand movements, and leg agility, moderately stooped posture, slow shuffling gait, and mild postural instability. The patient reported that several years before the onset of the motor problems he became more apathetic and lost interest in his everyday activities. At the onset of parkinsonian signs he also developed a depressive mood, and reported feeling sad most of the time, with difficulties in falling asleep, loss of interest in activities of daily living, worrying about minor matters, difficulties in concentration, and loss of energy and libido. […]