Extrapyramidal movement disorders Flashcards
Is Parkinson’s disease a hyperkinetic or hypokinetic disorder?
[Hypokinetic… the untreated patient feels ‘like a prisoner in their own body’; with the exception of resting tremor, all of those extra movements (dyskinesias) we see in such patients are attributable to the drugs taken to facilitate movement]
What is an ‘extrapyramidal’ disorder?
[the distinction between pyramidal and extrapyramidal is rarely used in research, but is useful clinically as it distinguishes between movement disorder associated with loss of corticospinal tract (e.g., stroke) and movement disorders primarily associated with the basal ganglia and cerebellum]
What is dystonia?
[an often painful condition in which there is commonly co-activation of opposing flexor and extensors, and which can be rhythmic as well. Torticollis (usually targeting sternocleidomastoid, trapezius muscles) is the classic example. Botulism toxin (Botox) is the wonder drug for treatment. More extensive or less focal dystonia can also occur… often associated with pathologic outflow of inner sector of globus pallidus. Dystonia is also common among individuals with cerebral palsy]
Parkinson’s disease is due to a massive loss of which cells?
[dopaminergic cells of the substantia nigra pars compacta. We all lose dopamine cells as we age… interestingly, symptoms do not appear until someone loses > 60-70% of those cells. Two other important points: the cell loss is usually asymmetric, complicating treating the ‘bad’ side with drugs, but is actually useful in diagnosis (i.e., in PD, expression should be dominant on one side over the other). Second, despite the massive cell loss in SNc, the VTA which is ‘next door’ and dopaminergic, is barely touched. Weird!]
What are the signs/symptoms of Parkinson’s disease?
[Clinicians like to describe a triad: bradykinesia, rigidity and tremor; a common 4th is postural instability (triad + one). The tremor is a resting tremor, usually of the extremities, has a freq of 4-6 Hz, and is apparent in ~50% of patients. There are numerous other signs, but these are major. Further, autonomic effects including constipation are common]
Describe the typical Parkinson’s patient?
[stooped posture, shuffling gait, slow movement, tremor, especially in hands when resting, disappears with movement, ‘blank’ facial expression, often soft voice]
Distinguish between Parkinson’s rigidity and spasticity?
[In response to passive movement, the patient is stiff; some patients will reveal a ‘cogwheel’ rigidity, almost as if there is ratcheting involved; spasticity (pyramidal tract) is rigidity that is directional and velocity dependent]
Characterize the Parkinsonian gait?
[Slow, difficult to initiate, narrow base, shuffling with e bloc turning (turning executed by a bunch of tiny steps) and retropulsion (multiple steps taken to regain balance when pushed backwards]
How is Parkinson’s disease treated?
[Increased dopamine efficiency is most common. This is achieved by either prescribing L-dopa, the precursor of dopamine that crosses blood-brain barrier, or using dopamine receptor agonists (especially for D3 receptors). The logic of L-dopa is that the few dopamine cells available will now have more dopamine to release. 15-40% of patients can benefit from deep-brain stimulation (DBS) in which permanent stimulating electrodes are implanted into either the subthalamic nucleus (most popular) or inner sector of globus pallidus. Despite the name, DBS effectively turns off the local activity. In Parkinson’s disease, the activity in these structures does more harm than good (facilitates the indirect pathway), so they are better off without it]
How common is Parkinson’s disease?
[1% of population > 60; considering the population, that’s common. Here’s something scary: 25 years ago, Parkinson’s patients < 50 constituted < 1% of patients. Today that figure is 10%!]
Do Parkinson’s patients get cancer?
[Amazingly, they get cancer at a rate < 10% of the frequency of aged-matched people that do not have Parkinson’s. Nobody really knows why Parkinson’s might afford protection from cancer]
What is MPTP?
[It’s a free-radical that has the remarkable property of efficiently killing dopamine neurons by apparently wiping out the mitochondria of the neuron. It was discovered by accident, from a bad batch of an illicit drug where instead of creating the drug they intended, they made a mistake and made MPTP: the people that took it had full-blown Parkinson’s disease within days. It’s toxicity alerted medicine to the fact that similar compounds found in pesticides were also capable of inflicting similar damage. Whereas 95% of Parkinson’s is idiopathic, these observations fuel the idea that environmental toxins can lead to Parkinson’s explaining the increase in the Parkinson’s patient under 50 years of age]
Identify risk factors of Parkinson’s disease?
[age, obesity, familial history, significant pesticide exposure]
What is Huntington’s Chorea?
[a genetic disease involving significant neuropathy of striatum and pre-frontal cortex, that often is used as both a prototype genetic disease and prototype hyperkinetic disorder. The disease can be traced to a single village in England (Bures) ~400 years ago. The condition is autosomal dominant with complete penetrance meaning offspring have a 50% chance of inheriting the disease. The initial symptoms are significant as they are psychological rather than motor. Typical 1st effects are carefree behavior, e.g., gambling, maxing out on credit cards, marital infidelity (all indicting of pre-frontal issues), followed by onset of motor problems that can include inability to hold a pencil. The chorea (rhythmic jerking movements) appear soon after. They are uncontrollable and can be superimposed on voluntary movements. It is progressive. Woody Guthrie, the famous American songwriter died of complications from the disease. The overall frequency of the disease is low, a small fraction of 1%, although Louisiana has more than most states].
What is tardive dyskinesia?
[An iatrogenic (physician-caused) disorder associated with chronic use of anti-psychotic drugs. Many antipsychotics suppress the efficacy of dopamine in circuits. Whereas these drugs ideally target circuits associated with the VTA and nu accumbens, they lack needed specificity and suppress nigrostriatal circuits as well. Such patients appear similar to Parkinson’s patients with a resting tremor (especially ‘pill-rolling’ behavior) and often exhibit an orofacial dyskinesia (‘lip-smacking’) that is unusual in Parkinson’s disease.]
