MKSAP Quiz: Twisting movements of neck, extremities
A 64-year-old man is evaluated for recent emergence of involuntary twisting movements of his neck and extremities. Parkinson disease was diagnosed 8 years ago. Mobility and fatigue improve after each dose of carbidopa-levodopa. Following a physical exam, what is the most appropriate next step in treatment?
A 64-year-old man is evaluated for recent emergence of involuntary twisting movements of his neck and extremities. Parkinson disease was diagnosed 8 years ago. Mobility and fatigue improve after each dose of carbidopa-levodopa. A few months ago, he started to feel excessive slowness and anxiety 1 hour before each dose of medication and was treated with an increased dose of his carbidopa-levodopa. Now, he has developed involuntary nonrhythmic movements that peak after each dose. Current medication is carbidopa-levodopa.
On physical examination, vital signs are normal. He is examined half an hour after taking a dose of levodopa. He exhibits cogwheel rigidity, shuffling of gait, and large-amplitude ballistic and flowing movements of the neck and extremities. Other examination findings are unremarkable.
Which of the following is the most appropriate next step in treatment?
A. Amantadine
B. Deep-brain stimulation
C. Entacapone
D. Ropinirole
E. Selegiline
MKSAP Answer and Critique
The correct answer is A. Amantadine. This content is available to MKSAP 19 subscribers as Question 59 in the Neurology section. More information about MKSAP is available online.
The most appropriate next step in treatment is amantadine (Option A). This patient with Parkinson disease has levodopa-induced dyskinesia. Patients with Parkinson disease may develop medication-related complications after a few years of treatment with levodopa. One example is the "wearing-off" phenomenon before each dose of medication due to progressive loss of the ability to store and release dopamine for extended periods. As a result, motor and nonmotor symptoms recur before the next dose of levodopa. Another complication is emergence of choreiform dyskinesia that peaks after each dose of levodopa and is caused by hypersensitization of dopamine receptors in the brain. Amantadine, a glutamate N-methyl-D-aspartate receptor antagonist, is an efficacious treatment for levodopa-induced dyskinesia and should be offered next. Reducing the levodopa dose is another strategy to improve dyskinesia but would lead to recurrence of the wearing-off problem in this patient, which was previously experienced as end-of-dose slowness and anxiety.
Deep-brain stimulation (Option B) is a surgical therapy that involves the delivery of electrical stimulation to key brain targets, such as the subthalamic nucleus and the globus pallidus interna. This mode of treatment is indicated for patients who continue to benefit from levodopa but experience motor fluctuations or have a refractory tremor. It can be effective for levodopa-induced motor complications that are refractory to medical management. However, in this patient, amantadine should be tried first because it is effective and noninvasive.
Typical strategies to address end-of-dose wearing-off phenomenon include increasing the dose of levodopa or adding a catechol-O-methyltransferase inhibitor (entacapone [Option C]), a dopamine agonist (ropinirole [Option D]), or a monoamine oxidase type B inhibitor (selegiline [Option E]). All of these strategies, however, can aggravate the dyskinesia and should be avoided in this patient.
Key Points
- Amantadine is an efficacious treatment for levodopa-induced dyskinesia.
- Treatments for end-of-dose wearing-off phenomenon include increasing the dose of levodopa or adding a catechol-O-methyltransferase inhibitor, a dopamine agonist, or a monoamine oxidase type B inhibitor.