Quality of life in Essential Tremor Questionnaire (QUEST): development and initial validation.
ABSTRACT Essential tremor (ET) can diminish functioning and quality of life (QOL) but generic QOL measures may be relatively insensitive to ET and its therapies. We sought to develop an ET-specific measure that might be more sensitive, acceptable to patients, relatively brief, and easily used.
A sample of 200 patients (average age 70 years, range 30-91; average disease duration 15 years) rated the extent to which tremor impacts a function or state, tremor severity in various body parts, perceived health, and overall QOL. Responses to this initial questionnaire were subjected to principal components analysis (PCA). Inspection of factor coordinates, Eigenvalues, variance accounted for, and correlation matrices were used to select items for confirmatory PCA. Final scale reliability was assessed using Cronbach's alpha. Validity was evaluated by correlations between QOL scales and self-rated tremor severity.
PCA of 65 initial items yielded 11 factors accounting for 71% of variance. Six factors were discarded. Two items were eliminated for not loading on a factor and 33 for perceived redundancy. Confirmatory PCA of the retained 30 items yielded an almost identical factor structure (six factors, 70% of variance accounted for, and similar item loadings). Because two factors had very few items loading on them, these two factors were combined into one scale. The final measure has five scales: Physical, Psychosocial, Communication, Hobbies/Leisure, and Work/Finance. Reliability was excellent for the whole instrument and four scales (> or =0.89), and good for the Work/Finance scale (0.79). Severity of voice and head tremor were the best correlates of Communication (0.70 and 0.35), while the Physical scale was related to right and left upper extremity tremor (0.59 and 0.56). Scales correlated more highly with patients' rating of their overall QOL than their health perception.
A brief, 30-item, ET-specific QOL scale with excellent reliability was developed. Preliminary validity data are encouraging. The Quality of Life in Essential Tremor Questionnaire (QUEST) promises to facilitate QOL measurement in ET.
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ABSTRACT: Background and purpose: Tremor accompanies some poly-neuropathies, but its prevalence and its clinical and electrophysiological manifestations are not well known. The aim of the study was to assess the occurrence and characteristics of hand tremor in patients with polyneuropathy of different origins, as well as relations between the occurrence of tremors and clinical and neurographic findings of polyneuropathy. Material and methods: Eighty-nine patients diagnosed with polyneuropathy of known aetiology, and 50 age- and sex-matched healthy volunteers were included in the study. All subjects were interviewed regarding the occurrence of tremor. Tremor was assessed clinically and objectively using a triaxial accelerometer and electromyographic (EMG) recordings. A load test with a weight of 500 γ was performed in order to differentiate between enhanced physiological tremor (EPT) and essential tremor-like (ET-L) tremor. Results: Tremor was found in 59.5% of patients in clinical assessment and in 74% of patients in objective evaluation, significantly more often than in controls (12%). Tremor was detected in all types of polyneuropathy apart from paraproteinaemic IgM polyneuropathy. Tremor was postural (70%), but resting (51%) or kinetic (32%) tremor was also present. In the majority of cases, the severity of the tremor was mild. Essential tremor-like tremor prevailed in the study group. The occurrence of hand tremor was not related to the axonal or demyelinating type of polyneuropathy, nor to the conduction velocity or other electrophysiological findings of the investigated upper limb nerves. Conclusion: Tremor accompanies 60-70% of patients with polyneuropathy; it is mostly postural, ET-L type with mild severity, and unrelated to other typical clinical and electrophysiological findings of neuropathy.Neurologia i neurochirurgia polska 01/2013; 47(6):525-33. · 0.54 Impact Factor
Conference Paper: Spectrally efficient multiuser space-time modulation[Show abstract] [Hide abstract]
ABSTRACT: To achieve full transmit diversity for a single user with NT antennas the coherence time of the channel has to be at least NT time-slots long. The same minimum number of slots (or dimensions) guarantees full transmit diversity for every user in a "narrowband" multiuser system in which all users communicate simultaneously and occupy the same bandwidth. However, with an increase in the number of users, an increasing signal-to-noise ratio (SNR) is required of each user to achieve the same error probability as in the single-user case. We showed earlier that this SNR penalty can be alleviated, and even eliminated for sufficiently high SNR, with only a marginal increase of the bandwidth and a judicious design of "spreading matrices" that spread a single-user space-time constellation or (block-) code. In other words, such signaling exploits multiuser diversity and ensures that each user enjoys single-user like performance for sufficiently high SNR. For instance, for NT-transmit antennas per user and a single-user space-time constellation that requires only the minimum time-slots NT, no more than NT+1 slots are required for the common signal space of any number of users. We present here simplified design criteria to obtain the spreading sequences/matrices. We also show that the optimum multiuser receiver can be implemented by the (generalized) sphere decoder of Damen et al. (see IEE Electronics Letters, vol.36, no.2, p.166-167, 2000).Information Theory, 2002. Proceedings. 2002 IEEE International Symposium on; 01/2002
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