A 65-year-old man comes to the office due to tremors. He was diagnosed with idiopathic Parkinson disease 10 years ago and has since been successfully treated with levodopa/carbidopa. However, over the last several months, he has developed frequent "freezing" episodes characterized by a sudden loss of mobility. More recently, the patient's tremors worsened after he reduced his levodopa dose following the development of excessive body movements. On examination, he has a bilateral resting tremor that is worse on the right, bradykinesia, and cogwheel rigidity. He is interested in discussing surgical options. This patient would most likely benefit from high-frequency deep brain stimulation targeted at suppressing neuronal activity in which of the following brain structures?

Question

A 65-year-old man comes to the office due to tremors.  He was diagnosed with idiopathic Parkinson disease 10 years ago and has since been successfully treated with levodopa/carbidopa.  However, over the last several months, he has developed frequent "freezing" episodes characterized by a sudden loss of mobility.  More recently, the patient's tremors worsened after he reduced his levodopa dose following the development of excessive body movements.  On examination, he has a bilateral resting tremor that is worse on the right, bradykinesia, and cogwheel rigidity.  He is interested in discussing surgical options.  This patient would most likely benefit from high-frequency deep brain stimulation targeted at suppressing neuronal activity in which of the following brain structures?

Quizplus · Accepted Answer

11ec160b_39d8_70ae_9249_457802582d95_MD0001_00 This patient on long-term levodopa treatment for Parkinson disease has likely developed motor fluctuations and dyskinesia, which often occur >5 years after starting therapy. Motor fluctuations can initially correlate with serum drug levels and are characterized by good mobility during "on" periods and increased bradykinesia/rigidity during "off" periods when the drug wears off. Dyskinesia typically occurs when the patient is "on" and is characterized by excessive involuntary movements. Nigrostriatal degeneration in Parkinson disease results in excessive excitation of the globus pallidus internus by the subthalamic nucleus, which in turn causes excessive inhibition of the thalamus. Reduced activity of the thalamus and its projections to the cortex consequently result in rigidity and bradykinesia. Patients with medically intractable symptoms of Parkinson disease may benefit from high-frequency deep brain stimulation of the globus pallidus internus or subthalamic nucleus. High-frequency stimulation inhibits firing of these nuclei. This causes increased activity in the downstream nuclei, resulting in thalamo-cortical disinhibition with improved mobility. (Choices A, B, C, and D) These neural structures are not generally subjected to therapeutic high-frequency deep brain stimulation. (Choice F) High-frequency stimulation of the ventral intermediate nucleus of the thalamus may reduce thalamic excitation and lessen excessive movements in patients with medically intractable essential tremor. Educational objective: Nigrostriatal degeneration in Parkinson disease reduces activity of the thalamus and its projections to the cortex, resulting in bradykinesia and rigidity. Patients with medically intractable symptoms of Parkinson disease may benefit from high-frequency deep brain stimulation of the globus pallidus internus or subthalamic nucleus as it promotes thalamo-cortical disinhibition with improved mobility. __________ References: Deep brain stimulation of the subthalamic nucleus in Parkinson's disease 2003-2013: Where are we another 10 years on? (http://www.ncbi.nlm.nih.gov/pubmed/25619979) Deep brain stimulation for Parkinson disease: an expert consensus and review of key issues. (http://www.ncbi.nlm.nih.gov/pubmed/20937936) History, applications, and mechanisms of deep brain stimulation. (http://www.ncbi.nlm.nih.gov/pubmed/23407652)

A 65-Year-Old Man Comes to the Office Due to Tremors