Improving the Diagnostic Accuracy in Parkinsonism
Improving the Diagnostic Accuracy in Parkinsonism
PD classically presents with an asymmetric rest-tremor, and it is important to document whether a true pill-rolling type (with involvement of the thumb) is present, as this is very supportive of a diagnosis of PD. Pill-rolling tremor does not exclude AP completely, because it can also occur in drug-induced parkinsonism and MSA, although in these two conditions the tremor tends to be more bilateral and symmetrical. So tremor symmetry is a valuable distinguishing feature, next to the nature of the tremor. Again, the separation is not complete, because an asymmetric, pill-rolling rest tremor can occur in patients with DLB and sporadically even in so called PSP-P patients. A jerky tremor, possibly due to polyminimyoclonus, is more suggestive of MSA.
Severe essential tremor, Holmes' tremor and dystonic tremor can present with a profound rest component. Several elements may help in separating these tremor types from parkinsonian tremor. Essential tremor is very symmetrical, and no other gross neurological abnormalities should be present (except for mild gait ataxia). Table 4 lists several characteristics of dystonic tremor. In addition, dystonic tremor more typically presents with thumb extension from the neutral position, while parkinsonian rest tremor usually involves thumb flexion from neutral. Holmes' tremor tends to have a lower frequency (at around 3 Hz) than tremor is PD (generally 4–6 Hz), but reliable frequency-based discrimination between the various tremor aetiologies is difficult, due to considerable overlap in frequencies.
When observing rest tremor it is important to specifically search for the resetting phenomenon (also referred to as re-emergent tremor): the re-emergence of tremor with a latency after a positional change. This latency suggests that a rest tremor has now reappeared in the newly acquired position, and this should not be mistaken for a positional tremor. Absence of this resetting phenomenon might point towards a dystonic tremor (Table 4).
Tremor Characteristics
PD classically presents with an asymmetric rest-tremor, and it is important to document whether a true pill-rolling type (with involvement of the thumb) is present, as this is very supportive of a diagnosis of PD. Pill-rolling tremor does not exclude AP completely, because it can also occur in drug-induced parkinsonism and MSA, although in these two conditions the tremor tends to be more bilateral and symmetrical. So tremor symmetry is a valuable distinguishing feature, next to the nature of the tremor. Again, the separation is not complete, because an asymmetric, pill-rolling rest tremor can occur in patients with DLB and sporadically even in so called PSP-P patients. A jerky tremor, possibly due to polyminimyoclonus, is more suggestive of MSA.
Severe essential tremor, Holmes' tremor and dystonic tremor can present with a profound rest component. Several elements may help in separating these tremor types from parkinsonian tremor. Essential tremor is very symmetrical, and no other gross neurological abnormalities should be present (except for mild gait ataxia). Table 4 lists several characteristics of dystonic tremor. In addition, dystonic tremor more typically presents with thumb extension from the neutral position, while parkinsonian rest tremor usually involves thumb flexion from neutral. Holmes' tremor tends to have a lower frequency (at around 3 Hz) than tremor is PD (generally 4–6 Hz), but reliable frequency-based discrimination between the various tremor aetiologies is difficult, due to considerable overlap in frequencies.
When observing rest tremor it is important to specifically search for the resetting phenomenon (also referred to as re-emergent tremor): the re-emergence of tremor with a latency after a positional change. This latency suggests that a rest tremor has now reappeared in the newly acquired position, and this should not be mistaken for a positional tremor. Absence of this resetting phenomenon might point towards a dystonic tremor (Table 4).
Source...