Mechanisms of aluminium neurotoxicity in oxidative stress-induced ...

INTRODUCTION
Resting tremor
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Resting tremor is the most commonly recognized feature of PD and the first
motor symptom at disease onset in approximately 75% of PD patients (Jankovic et al.
1990, Hughes et al. 1993, Schrag et al. 2007). However, 25 % of patients with PD never
develop tremor (Hughes et al. 1993). Rest tremor has a frequency of 4–6 Hz and
classically resembles pill-rolling (descriptive of the rhythmic alternating motion of the
forefinger and thumb). This motor manifestation/symptom is usually a supination-
pronation tremor, asymmetric, and most prominent in the distal upper extremity as
resting foot tremor is much less common than hand tremor as a presenting sign. Tremor
at rest is lost during sleep and markedly decreased or abolished with voluntary
movement (so typically it does not impair activities of daily living). It should be noted
that PD tremor can also be seen to have a postural component. Nevertheless, rest tremor
is worsened by excitement, anxiety, apprehension, contralateral motor activity, and is
most easily seen when the patient is asked to ambulate with arms hanging at their sides.
Observation of the patient during ambulation reveals much about the patient‟s
symptoms, including rigidity and bradykinesia.
Rigidity
Rigidity is the raised resistance appreciated during the passive movement of the
limb about a joint (often of a “lead pipe” quality). A “ratchety” sensation can be noted,
indicating the contraction and relaxation of the muscles underlying the tremor. It can
have a cogwheel quality even without tremor, but is usually more pronounced in the
more tremulous limb. Rigidity is enhanced by contralateral motor activity or mental task
performance. Bradykinesia and rigidity are less common then rest tremor but are still
frequently seen at onset of PD.