Biomedical subjects

Natasha M Maurits

Publications and source records attributed to Natasha M Maurits.

8 recordsLinked to original sources

PubMed2006

Coherence analysis differentiates between cortical myoclonic tremor and essential tremor.

Familial cortical myoclonic tremor with epilepsy (FCMTE) is characterized by a distal kinetic tremor, infrequent epileptic attacks, and autosomal dominant inheritance. The tremor is thought to originate from the motor cortex. In our patient group, a premovement cortical spike could not be established on electroencephalogram (EEG) back-averaging. Corticomuscular and intermuscular coherence analysis can demonstrate a cortical common drive to muscles. We carried out coherence analysis of electromyography (EMG) of forearm muscles and EEG of contralateral motor cortex in 7 FCMTE patients, 8 essential tremor (ET) patients, and 7 healthy controls. Results showed strong cortico- and intermuscular coherence in the 8- to 30-Hz range in the FCMTE patients, with EEG preceding EMG. Healthy controls and ET patients showed normal weak coherence around 20 Hz. The ET patients showed some additional coherence at tremor frequency (6 Hz), probably the result of sensory information flowing back to the sensorimotor cortex. These findings point to a pathological cortical drive in FCMTE patients leading to tremulous movements. Coherence analysis is an easy and useful method to differentiate FCMTE from ET. Coherence analysis is helpful when investigating a cortical common drive in cortical tremor and other movement disorders.

Adult↗

PubMed2006

EEG coherence obtained from an auditory oddball task increases with age.

Changes in coherence with aging during cognitive tasks have, until now, not been investigated. However, several fMRI and positron emission tomography studies of cognitive tasks have found increased bilateral activity in elderly subjects. Changes in coherence with aging during a cognitive task were investigated to see if EEG coherence was present in older adults. An auditory oddball task, which is a widely used test for cognitive function, was used. Eleven young adults (27.8 +/- 4.8 years, six females) and 10 older adults (61.3 +/- 4.6 years, six females) were studied, and both interhemispheric and long- and short-range intrahemispheric coherence were considered. Higher interhemispheric coherence was found in the older subjects in the delta band. Short intrahemispheric coherence was also increased in the theta, delta, and alpha bands. Higher coherence, although not significantly different, was also found for all other coherence types and bands, except for long intrahemispheric coherence in the low gamma band. The results presented here provide the first evidence that aging is associated with increased EEG coherence during a relatively easy cognitive task.

Acoustic Stimulation↗

PubMed2005

P300 after head injury: pseudodelay caused by reduced P3A amplitude.

OBJECTIVE: We compared conventional P300 analysis with source analysis in normal subjects and head-injury patients. Based on earlier findings of improved P300 component identification and reduced P3B latency variability with source analysis in normal subjects, our aim was to investigate whether source analysis could improve the distinction between these groups. METHODS: In total, 21 healthy control subjects and 21 patients with mild to moderate head injury were included in this study. A standard auditory 2-tone oddball paradigm was used. Latencies and amplitudes obtained with conventional P300 analysis were compared with source analysis results. RESULTS: With conventional analysis, head-injury patients had delayed P300 latencies and reduced P300 amplitudes in comparison to controls, while source analysis showed no latency differences for both P3A and P3B components. Instead, source analysis indicated absence of P3A components in 43% of patients. CONCLUSIONS: The P300 delay in head-injury patients, observed with conventional analysis, is a pseudodelay caused by decreased P3A amplitudes. Consequently, the unaffected P3B component with its later latency determines conventional P300 latency in these patients. SIGNIFICANCE: Conventional P300 latency cannot be used to conclude that there was delayed early stimulus processing in head-injury patients.

Adult↗

PubMed2005

P300 component identification in auditory oddball and novel paradigms using source analysis techniques: reduced latency variability in the elderly.

P300 latency variability in normal subjects limits its diagnostic applicability as a test for cognitive function. One of the causes of variation is the overlap in P300 (P3A and P3B) components resulting in inaccurate latency determination. Recently, we have shown that identification of P3A and P3B components using source analysis techniques significantly reduces P300 latency variability in healthy younger subjects. Here, we included a novel paradigm to enhance sensitivity and investigated the efficiency of the source analysis technique in reducing the P300 latency variability in healthy older subjects. Data were recorded with a 128-channel EEG system in 28 healthy subjects (aged 53-82 years, 12 males). We used a standard two-tone and a novel three-tone auditory oddball paradigm and an established source analysis technique, and compared the latencies to those obtained with conventional P300 analysis. The source analysis method identified both P3A and P3B components in a substantially larger percentage of subjects (93% versus 32%) than the conventional method. Both for the standard and novel paradigm, the source analysis method yielded a later mean P3B latency (361.4 versus 344.2 milliseconds, P = 0.017, and 374.4 milliseconds versus 354.3 milliseconds, P = 0.014, respectively) with a smaller standard deviation (15.8 versus 26.2 milliseconds, P = 0.013, and 18.9 versus 30.0 milliseconds, P = 0.052, borderline significant, respectively) than the conventional P300 method, for subjects aged 50 to 70 years. When applying the source analysis technique, as in young healthy subjects, a considerable reduction of P300 latency variability was thus found in healthy older subjects aged 50 to 70 years for both paradigms. This may have important consequences for applications of clinical event-related potential research in the early diagnosis of dementia, because the first signs of this disease are mostly observed in this age category.

Acoustic Stimulation↗

PubMed2004

A preliminary study on electromyographic analysis of the paraspinal musculature in idiopathic scoliosis.

The paraspinal muscles have been implicated as a major causative factor in the progression of idiopathic scoliosis. Therefore, the objectives of this preliminary study were to measure the electromyographic activity (EMG) of the paraspinal muscles to determine its relationship to progression of the scoliotic curve. Idiopathic scoliotic patients were selected and identified afterwards on curve progression. The EMG activity on both sides of the spine was measured in a set of standardized postures using bipolar surface electrodes at the apex and two end vertebrae of the scoliotic curve. An EMG ratio involving measurements of the EMG activity on the convex and concave sides of the scoliotic curve was used to evaluate the paraspinal muscles. Enhanced EMG ratios at the apex of the scoliotic curve were found in both groups during sitting and standing. The most interesting finding was that children with progression of the curve also showed enhanced EMG ratios at the lower end vertebra of the curve. The EMG ratios between the groups were significantly different from each other at the apex and end vertebrae for several test conditions. Overlap in the EMG-ratio ranges made differentiation difficult for prediction of the progression of the individual scoliosis patient. However, the EMG ratio at the lower end vertebra of the scoliotic curve is significantly higher than 1 in all test conditions in the group of children with subsequent progression of the curve, whereas it is always normal in the non-progressive group. Therefore, EMG of the paraspinal muscles might be of value for prediction of progression in idiopathic scoliosis.

Adolescent↗

PubMed2004

The relation between electromyography and growth velocity of the spine in the evaluation of curve progression in idiopathic scoliosis.

STUDY DESIGN: A prospective study in which patients with idiopathic scoliosis were examined longitudinally by radiographic and electromyographic measurements according to a protocol. OBJECTIVES: To measure the growth velocity of the spine and the electromyographic ratio of the paraspinal muscles to determine their relation to progression of the scoliotic curve. SUMMARY OF BACKGROUND DATA: Several factors have been reported to be involved in the progression of idiopathic scoliosis. Possible factors may be growth disturbances and muscular abnormality. METHODS: Thirty patients with idiopathic scoliosis were examined over periods of 4 to 5 months. The periods were scored for progression, defined as an increase in Cobb angle of >10 degrees. Spinal growth velocity was measured as the length difference of the scoliotic spine between two consecutive radiographs. The electromyographic activity on both sides of the spine expressed as an electromyographic ratio was measured during relaxed upright standing using bipolar surface electrodes. Predictability of progression was evaluated with regression analysis and receiver operating characteristic analysis. RESULTS.: There was an independent association between both spinal growth velocity and electromyographic ratio and progression of the scoliotic curve. An equal sensitivity and specificity of spinal growth velocity for progression of 79.1% was observed at a growth velocity cutoff point of 11 mm/year. Similarly, a cutoff point of 1.25 for the electromyographic ratio could be determined with a predictive value for progression of 68.9%. In the presented nomogram, a spinal growth velocity >15 mm/year combined with an electromyographic ratio >2 gave an 89% probability of progression of the scoliotic deformity. Growth velocities 38 mm/year never resulted in progression. CONCLUSIONS: The combined measurement of spinal growth velocity and electromyographic ratio has significant predictive potential and may be valuable in the evaluation and treatment of idiopathic scoliosis.

Adolescent↗

PubMed2003

Admitting acute ischemic stroke patients to a stroke care monitoring unit versus a conventional stroke unit: a randomized pilot study.

BACKGROUND AND PURPOSE: Pathophysiological considerations and observational studies indicate that elevated body temperature, hypoxia, hypotension, and cardiac arrhythmias in the acute phase of ischemic stroke may aggravate brain damage and worsen outcome. METHODS: Both units were organized with the same standard care and multidisciplinary approach to nursing and rehabilitation. A blinded observer assessed functional outcome at 3 months with the modified Rankin scale (mRS) and Barthel Index (BI). End points were (1) poor outcome, defined as either mRS > or =4 or BI <60 or the need for institutional care and (2) mortality. RESULTS: Fifty-four patients meeting the inclusion criteria were randomized. The groups were well matched for baseline characteristics, stroke subtype, stroke severity, vascular risk factors, and prognostic factors. Poor outcome was seen in 7 (25.9%) patients in the SCMU group and in 13 (48.1%) in the SU group (P=0.16). Mortality was lower in the SCMU group than in the SU group (1 [3.7%] vs 7 [25.9%]; odds ratio, 0.11 [95% CI, 0.02 to 0.96], P=0.05). CONCLUSIONS: This pilot study suggests that admission of acute stroke patients to an SCMU may reduce mortality and poor outcome. A larger trial is required to confirm these findings.

Aged↗

PubMedDate not supplied

Design and evaluation of tiled parallel coordinate visualization of multichannel EEG data.

The field of visualization assists data interpretation in many areas, but does not manage all types of data equally well. This holds, in particular, for time-varying multichannel EEG data. No existing method can successfully visualize simultaneous information from all channels in use at all time steps. To address this problem, a new visualization method is presented based on the parallel coordinate method and making use of a tiled organization. This tiled organization employs a two-dimensional row-column representation, rather than a one-dimensional arrangement in columns as used for classical parallel coordinates. The usefulness of the new method, referred to as tiled parallel coordinates (TPC), is demonstrated by a particular type of EEG data. It can be applied to an arbitrary number of time steps, handling the maximum number of channels currently in use. An extensive user evaluation shows that, for a typical EEG assessment task, data evaluation by the TPC method is faster than by an existing clinical EEG visualization method, without loss of information. The generality of the TPC method makes it widely applicable to other time-varying multivariate data types.

Computer Graphics↗