A 56 year-old consultant surgeon has recently been diagnosed with idiopathic Parkinson’s disease, and attends clinic for review.
You read the previous clinic letter and see that he presented with tremor affecting mainly the right hand, which forced him to stop operating. On examination he also had some bradykinesia and rigidity of the right hand. He was started on co-beneldopa 100/25, initially one tablet three times daily, with instructions to up-titrate as tolerated.
When you see him today, he is concerned that there has been no improvement in the tremor. This is causing him considerable distress as he hopes to return to clinical work. His motor control is otherwise good, and throughout the day and night he has no difficulty with ‘off’ periods or freezing. He currently takes co-beneldopa 100/25, two tablets three times daily, and reports no complications.
On examination there is a resting tremor of the right hand. There is no discernable rigidity or bradykinesia.
What is the best treatment option?
Increase dose of co-beneldopa
Increase frequency of co-beneldopa
Add procyclidine
Add entacapone
Add selegiline
Tremor-predominant Parkinson’s disease can be highly disabling and tremor may persist despite standard treatment with dopaminergic agents, which primarily improve bradykinesia. First-line treatment is such cases is the addition of an anticholinergic drug such as procyclidine, orphenadrine, or trihexyphenidyl.
The main side-effect which limits the use of anticholinergics in older patients is cognitive dysfunction, and dementia is a relative contra-indication. Other side effects include blurred vision, urinary retention, nausea, constipation, and dry mouth.
Second-line treatments for persistent tremor include amantidine, clozapine, and propranolol. Deep brain stimulation may be used in refractory cases.
Increasing the dose of L-dopa is required when ‘off’ symptoms (bradykinesia, rigidity, freezing) do not respond to the starting dose, however this patient is taking a reasonable dose of L-dopa (600mg) and is not troubled by ‘off’ symptoms.
Increasing the frequency of L-dopa, which has a short half-life, is required when patients become ‘off’ in between doses. As the disease progresses the on period after each dose becomes shorter.
Entacapone and selegiline are used as adjuncts to prolong the ‘on’ period after a dose of L-dopa.