Tremor in Parkinson’s disease

Gross C., Guehl D. Effect of deep brain stimulation on amplitude and frequency characteristics of rest tremor in Parkinson s disease. Thalamus Relat Syst, 2001,... 

Disorders of the human cerebellum result in three types of abnormalities. The first is hypotonia or reduced muscle tone. Another includes abnormalities in the execution of voluntary movements or ataxia (defective muscular coordination). The third type of muscular malfunction is intention tremors. These tremors differ from the resting tremors of Parkinson s disease in that they occur during a movement and are most pronounced at the end of the movement when the patient attempts to terminate it. 

Bromocriptine is a dopamine agonist acting by direct stimulation of the dopamine receptors. In Parkinson s disease, it is reserved for use in patients who are intolerant to levodopa or in whom levodopa alone is not sufficient. Orphenadrine is an antimuscarinic indicated in Parkinson s disease. Antimuscarinics tend to be more effective than levodopa in targeting tremor rather than rigidity and bradykinesia. Moclobemide is an antidepressant referred to as a reversible monoamine oxidase inhibitor (RIAAA) type A. 

Co-careldopa is a combination of levodopa and the peripheral dopadecar-boxylase inhibitor. Co-careldopa is indicated in Parkinson s disease to improve bradykinesia and rigidity rather than tremor. Orphenadrine is an antimuscarinic agent indicated in patients with Parkinson s disease where tremor predominates. Trifluoperazine is a piperazine antipsychotic that should be used with caution in patients with Parkinson s disease as its use may exacerbate the condition. 

Despite the lack of controlled studies, there is evidence that cannabinoids are of therapeutic value in the treatment of tics in Tourette syndrome, the reduction of levodopa-induced dyskinesia in Parkinson s disease, and some forms of tremor and dystonia. 

Q8 Acetylcholine is normally in balance with dopamine in the basal ganglia, but in Parkinson s disease dopamine levels are reduced and the effects of acetylcholine become more pronounced. To restore the balance, antimuscarinic agents are used to antagonize the excitatory actions of acetylcholine. They seem to be effective for tremor and reduce the secretion of saliva, digestive juices and sweat. 

In Parkinson s disease, dopamine levels are decreased because of a deficiency in conversion of dopa to dopamine (see Figure 7-12). The common characteristics are tremors, difficulty initiating voluntary movement, a masked face with staring expression, and a shuffling gait. 

Catecholamine neurotransmitters in the central nervous system are synthesized in that location itself because they cannot cross the blood-brain barrier. However, dopa readily crosses the blood-brain barrier, promoting the catecholamine synthesis. Thus, in disorders involving deficiency of catecholamine synthesis, administration of dopa may have beneficial effects. In Parkinson s disease, in which deficiency of dopamine synthesis affects nerve transmission in the substantia nigra of the upper brain stem, administration of dopa leads to some symptomatic relief. Parkinsonism is a chronic, progressive disorder characterized by involuntary tremor, decreased motor power and control, postural instability, and muscular rigidity. 

Parkinson s disease was the first neurological disorder to be associated with deficiency of a specific neurotransmitter. In Parkinson s disease, there is a deficiency of dopamine in the basal nuclei, which leads to overactivity of cholinergic pathways and the characteristic hypokinesia, rigidity and tremor. Drugs used to treat Parkinson s disease aim to replace dopamine stimulate dopamine receptors or the release of remaining dopamine reduce breakdown of dopamine or reduce excessive parasympathetic activity. More recently, attempts have been made to replace dopamine-secreting cells by transplantation of fetal brain tssue. 

Barbeau (1984) reported that the hypokinesia and tremor present in patients suffering from manganism differed from those seen in Parkinson s disease. Caine et al. (1994) noted other characteristics that distinguish manganism from Parkinson s disease psychiatric disturbances early in the disease (in some cases), a cock-walk, a propensity to fall backward when displaced, less frequent resting tremor, more frequent dystonia, and failure to respond to dopaminomimetics (at least in the late stages of the disease). 

All of these neurotransmitters are synthesized from the amino acid tyrosine (Figure 16.6). Dopamine is critical to good health. A deficiency in this neurotransmitter, for example, results in Parkinson s disease, a disorder characterized by tremors, monotonous speech, loss of memory and problem-solving ability, and loss of motor function. In the brain, dopamine is synthesized from L-dopa. It would seem logical to treat Parkinson s disease with dopamine. However, dopamine cannot cross the blood-brain barrier to enter brain cells. Therefore, L-dopa is used to treat this disorder. It is converted to dopamine upon entry into brain cells. 

An important issue is the collective dynamics of neuronal populations. Indeed, synchronization of individual neurons is believed to play the crucial role in the emergence of pathological rhythmic brain activity in Parkinson s disease, essential tremor and in epilepsies the detailed discussion of... 

Uses The uses of botulinum toxin in Parkinson s disease [54" ], anal fissure [55" ], women with chronic pain [56" ], spasticity after stroke in adults [57", 58 ], and urological conditions [59 have been reviewed. The pharmacology and formulations of botuhnum toxins and data from clinical trials, demonstrating their efficacy in dystonia, spasticity, tics, tremor, dysphonia, and autonomic disorders, have been reviewed [60 ]. 

Therapeutic approaches approved by the FDA include spinal cord stimulation for pain, DBS for Parkinson s disease and essential tremor, and vagus nerve stimulation in epilepsy and depression. Techniques stiU at the investigational stj e include DBS for depression, epilepsy, headache, Tourette s syndrome, and pain cortical stimulation in Parkinson s disease, tremor, pain, depression, and stroke rehabilitation and peripheral nerve stimulation for headache and tinnitus. 

Mellor K, Ahmed A, Thomson A. Tramadol hydrochloride use and acute deterioration in Parkinson s disease tremor. Mov Disord 2009 24(4) 622-3. 

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