A 60-year-old man comes to the physician complaining of shaking of his right hand. This problem began several months ago and has progressed over time. He says it is worse while watching TV, but that he frequently forgets about it while working or doing his regular daily activities. He is an accountant who works at a bank. His past medical history is significant for left hip osteoarthritis for which he occasionally takes naproxen to relieve the pain. His mother has diabetes mellitus. His father died of a heart attack at age 60. His blood pressure is 125/68 mm Hg in both arms and heart rate is 72/min. His BMI is 27 kg/m². Physical examination shows a right hand tremor that diminishes with movement, and involuntary resistance to flexion of the right wrist and right arm. No sensory abnormalities are present. Muscle strength is preserved on both sides. Plantar reflexes are flexor bilaterally.
Which of the following is the most accurate tool that can be used to diagnose this patient's disease?

Question

Quizplus · Accepted Answer

Explanation: Parkinson disease (PD) is a clinical diagnosis that depends on the ability to recognize characteristic symptoms and physical signs. Bradykinesia and tremor or rigidity are essential features for diagnosis; however, these physical findings can have a diagnostic accuracy of only 26% at an initial visit. Bradykinesia is eventually seen in practically all patients, tremor is seen in about 79%-100% of patients, and rigidity occurs in approximately 90% of patients. A significant improvement in symptoms with dopaminergic medications is also highly supportive and improves diagnostic accuracy. Other features that are suggestive of the disease include a unilateral onset and persistent asymmetry of symptoms. Conventional brain MRI is of limited value in making a diagnosis of PD (Choice D). However, it should be performed to evaluate for alternate conditions such as stroke and hydrocephalus. The striatal dopamine transporter scan (DaTSCAN) is a nuclear medicine scan that uses ioflupane -123 (¹²³I), a radioactive isotope with a high affinity for dopamine transporters located in the striatal region of the brain. Low uptake of ¹²³I in the striatal region has a diagnostic accuracy equal to that of physical examination and is typically reserved for patients in which the diagnosis is equivocal. ¹²³ ¹²³ (Choices A, B, and C) Other diagnostic evaluations such as autonomic testing, electroencephalography, and lumbar puncture have a limited role in the diagnosis of PD but can help to exclude other diagnoses. Educational objective: Parkinson disease is a clinical diagnosis that requires the presence of bradykinesia in addition to tremor or rigidity. A brain MRI is usually performed to exclude alternate diagnoses; the striatal dopamine transporter scan can be considered when the diagnosis of Parkinson disease is equivocal. References: Parkinson disease: an update. (http://www.ncbi.nlm.nih.gov/pubmed/23418798)

A 60-Year-Old Man Comes to the Physician Complaining of Shaking