The heterogeneity of Parkinson's disease

Abstract

In 334 patients with idiopathic Parkinson's disease, deterioration in mental status paralleled severity of bradykinesia, postural instability, and gait difficulty. Tremor was relatively independent of the other cardinal signs and was associated with relative preservation of mental status, earlier age at onset, family history of parkinsonism, and more favorable prognosis. There seem to be at least two Parkinson's subgroups: one with postural instability and gait difficulty and another with tremor as the dominant feature.

Morphological differences in Parkinson’s disease with and without rest tremor

“…Two had declined participation and one could not be included due to MR-incompatibility (pacemaker). Fourteen of the 24 (58 %) had classical parkinsonian rest tremor including four who fulfilled criteria of tremordominant PD [36,67] and ten who could be considered "mixed" PD. In the ten remaining PD patients without tremor, rest tremor as well as postural and/or action tremor was firmly excluded.…”

“…The deviating tremor-dominant PD criteria [36,67] may allow the identification of a subgroup of patients with a comparatively benign disease course [27,30,31,33,35,41,48], but the small number of tremor-dominant PD patients in this collective precludes a separate VBM analysis of this subgroup.…”

Item Response Theory as an Efficient Tool to Describe a Heterogeneous Clinical Rating Scale in De Novo Idiopathic Parkinson’s Disease Patients

“…It assumes, therefore, an equal rate of disease progression for the all items of the scale, and thus, a similar degenerative mechanism for the motor, non-motor and tremor symptoms. However, recent analyses of the symptoms have led some to question this hypothesis (7,10,13,(15)(16)(17)(18) .…”

“…Several factor analyses demonstrated that non-motor, motor and tremor symptoms are relatively independent (12,15). When analyzed independently, tremor items have been shown to progress more slowly than all other motor features (9,13,14).…”

Parkinson's disease – pathology, aetiology and diagnosis

“…124 In contrast, the sub-type of tremor dominant PD is generally associated with a younger age at onset, 125 a more benign clinical course and preserved mental status. 119,[120][121][122][123][124][125][126] Conflicting studies report that prominent tremor is associated with older age, 127 dementia 128 and to a lesser extent rapid disease progression. 128 Other data suggest few clinical differences between youngand old-onset PD, 129 although muscular stiffness and sensory symptoms may be a more common presentation in younger patients.…”