Disturbed frontal regulation of attention in Parkinson's disease.

Parkinson's disease is characterized not only by tremor, akinesia and rigidity, but also by frontal cognitive dysfunction, that can be understood as a disturbance in the 'Supervisory Attentional System' (SAS). This concept refers to a system, located in the frontal cortex, that regulates attentional processes under novel, non-routine conditions. The hypothesis that cognitive dysfunction in Parkinson's disease results from a disturbance in the SAS was investigated by recording 'processing negativity' in 33 parkinsonian patients and 17 controls. Processing negativity is an event-related potential that reflects neuronal activity during selective attention. The contribution of the frontal cortex to selective attention can be studied directly using processing negativity. Parkinsonian patients were also scored for clinical symptoms and subjected to a neuropsychological test battery. Processing negativity was clearly disturbed in the parkinsonian patients. Moreover, parkinsonian patients with the lowest scores on 'frontal' neuropsychological tests such as Stroop, Trail Making and Word Fluency, also had the lowest processing negativity. Our results support the hypothesis that cognitive dysfunction in Parkinson's disease might be understood as a disturbance in the frontal regulation of attentional processes. Degeneration of the dopaminergic mesocortical innervation of the frontal cortex in Parkinson's disease is a possible neurochemical substrate of these frontal attentional disturbances.

Reliability, validity and follow-up of the EEG in senile dementia: sequelae of sequential measurement.

In a longitudinal study, slowing of the EEG in SDAT patients and elderly controls is investigated using both visual and power spectral analyses. For this a reliability study in 20 SDAT patients is performed and results for intra-rater, inter-rater and test-retest reliability (in 24 h) are used in the selection of parameters. Next, the diagnostic efficacy of the chosen parameters for SDAT is confirmed in a validity study in 43 SDAT patients, 41 elderly non-organic psychiatric patients and 51 elderly normals. In the longitudinal study 78 of these subjects could be retested after 20 months. The parameter for visual analysis appeared to be superior in actually showing a progress of slowing of the EEG in 20/21 SDAT patients over time. The parameter for power spectral analysis was superior in measuring the more subtle processes in the normal elderly. Results of these studies are used to discuss some problems in the measurement of EEG in SDAT over time.

Anal sphincter EMG in anorectal disorders.

In 26 patients with different anorectal disorders electromyography was performed in combination with anal manometry. EMG was carried out with a concentric needle electrode as well as with a single fibre electrode. Also the pudendal nerve terminal motor latency (PNTML) was assessed. A relationship was found between maximal squeeze pressure in anal manometry and maximal voluntary contraction pattern in concentric needle EMG. Mean fibre density (FD) was increased while mean PNTML was not increased. However a relationship was found between PNTML and FD. This discrepancy, increased FD with normal PNTML could mean that a myogenic factor plays an important role in our patients.

Biochemical and neurophysiological parameters in hemodialyzed patients with chronic renal failure.

Serum concentrations of accumulated solutes, standard clinical biochemistry, and parameters of clinical neuropathy, were determined in hemodialyzed patients with chronic renal failure. Analyses by high-performance liquid chromatography included creatinine, pseudouridine, urate, p-hydroxyhippuric acid, hippuric acid, indoxylsulfate, tryptophan, tyrosine, 3-indoleacetic acid, and a number of as-yet unidentified solutes. Standard biochemical parameters were measured; aluminium, parathyroid hormone, serum electrolytes and enzymes, hemoglobin, bilirubin, phosphate and urea. Measures of clinical neuropathy were: maximal motor nerve conduction velocities, and Hoffmann reflex latency. Several solutes had higher concentrations when nerve function was impaired. Serum total LDH, and total calcium levels correlated positively with values of the Hoffmann reflex, as did serum hippuric acid concentrations. Concentrations of p-hydroxyhippuric acid and two fluorescent compounds correlated negatively with motor nerve conduction velocities. In principal component analysis a number of 'organic acid-like' substances, like hippuric acid and p-hydroxyhippuric acid, were shown to associate multivariately with the neurophysiological variables while urea, creatinine, urate and phosphate were not.

Late sequelae of a non-optimal neonatal neurological condition in ERPs at the age of 11-13 years.

In a longitudinal study a selective attention task was administered to 11-13-year-old children. During this task (employing a combined filter and selective-set paradigm), event-related brain potentials were recorded to study timing and morphology of early and late selection processes. Task performance was prospectively and retrospectively related to neurological optimality at birth and to flash-evoked potential correlates that were registered at the age of five. The results provided evidence that even after 13 years neonatal neurological suboptimality was reflected in task performance, both in reaction time and in electrophysiological data. Task load interacted with group classification according to optimality to the disadvantage of suboptimals. This implied that load demands differentiated between groups. The event-related brain potentials revealed the existence of a negative shift associated with memory load (search-related negativity) at Fz and Cz, and a positive deflection at Pz (P3b) associated with target detection. Cortical activity, expressed in terms of these deflections, appeared to be less pronounced for the suboptimal group.

The external anal sphincter. Relationship between anal manometry and anal electromyography and its clinical relevance.

Anal manometry and anal electromyography (EMG) were performed in 45 patients to evaluate the external anal sphincter. Their symptoms were soiling (N = 6), incontinence (N = 10), and obstipation (N = 19). Clinical diagnoses were previous anal surgery (N = 16), rectal prolapse--partial, total, intussusception (N = 16), puborectalis syndrome (N = 4), neurologic disorders (N = 3), and others (N = 6). The relationship between the maximum squeeze pressure (MSP) measured with anal manometry and the maximum (voluntary) contraction pattern (MCP) and signs of denervation (DEN) measured with anal EMG were examined. The correlation coefficient between MSP and MCP was 0.55 (P less than .001) and between MSP and DEN 0.13 (NS). A normal MSP always showed a normal MCP, a normal MCP showed an abnormal MSP in 43 percent only. In conclusion, the clinical value of anal EMG seems limited. Assessment of an additional anal EMG seems indicated in incontinent patients with previous anal surgery with a low MSP to estimate muscle function, whenever anal surgery is considered. Anal EMG during straining can easily confirm the clinical diagnosis of puborectalis syndrome.

H reflex latency as an adequate predictor of the spinal evoked potential latency.

By stimulation of the posterior tibial nerve, somatosensory responses can be recorded at the level of the popliteal fossa, thoraco-lumbar spinal region and scalp. The thoraco-lumbar spinal potential is frequently difficult to record. Therefore several methods to estimate its latency were used and the results were compared with the real latency of the N24 recorded at spinal level in a group of healthy volunteers. A formula using the Hoffmann reflex latency (H-M interval) proved to be the most adequate for this purpose. By knowing the spinal potential latency, either through direct recording or through estimation by the formula, determination of a central conduction time, the N24-P40 interval, is possible. Normative values for this parameter are given.

Peripheral nerve function in patients with painful diabetic neuropathy treated with continuous subcutaneous insulin infusion.

In order to study the effects of improved metabolic control on painful diabetic polyneuropathy, 15 patients were treated with continuous subcutaneous insulin infusion over a 12 month period. Polyneuropathy was assessed by pain score, neurological examinations, nerve conduction studies and determination of sensory thresholds and cardiovascular reflexes. Improved metabolic control was confirmed by significantly improved levels of glycosylated haemoglobin (11.7 +/- 0.3% at entry to the study, to 8.7 +/- 0.3% after 12 months; mean +/- SEM). Symptomatic relief was confirmed by significantly improved pain scores. Thresholds for thermal cutaneous sensation improved significantly from 6.0 +/- 0.8 degrees C at entry to the study to 2.7 +/- 0.7 degrees C after 12 months (mean +/- SEM). These findings suggest a selective improvement of peripheral small nerve fibre function after continuous subcutaneous insulin infusion. The importance of quantitating thermal cutaneous sensation in longitudinal studies of patients with diabetic neuropathy was confirmed.

The influence of attention on visual evoked potentials in normal adults and dementias.

In normal subjects (n = 58, 22-71 y) the influence of the attention level on the VEP latency is studied, as is done in an additional small group of dementias (n = 14). The motor reaction time test (MRT) was selected to measure the attention level. The MRT was administered simultaneously with the VEP (checkerboard pattern reversal). By comparing VEP in test and non-test situations it proved that administration of MRT during VEP examination does not influence the VEP latencies. In dementias the motor reaction time is delayed but the degree of MRT delay did not correlate with the VEP latencies. This holds true for healthy volunteers as well as for demented patients. It is thus concluded that the latency increase of the late peaks of the VEP in dementias cannot be attributed to attentional deficits.

Anterior temporal focal abnormalities in EEG in normal aged subjects; correlations with psychopathological and CT brain scan findings.

Normal aged subjects (65-83 years) were examined by EEG and CT brain scan; also a Geriatric Mental Scale (GMS) and Neuropsychologic Assessment Battery were administered. Based on the EEG findings 2 subgroups could be distinguished: one with focal abnormalities in the left fronto-temporal region and one without these focal abnormalities. The focal delta subgroup proved to perform poorly on the Fluency Test, a simple quick bedside, but very sensitive, test for word association productivity. Also this subgroup showed more ventricular dilatation than the non-focal group. Therefore slight left-sided antero-temporal abnormalities in normal aged subjects are not irrelevant but an early (subclinical) sign of temporal lobe pathology as expressed in deterioration of language function.

Comparison of Hoffmann reflex with quantitative assessment of cutaneous sensation in diabetic neuropathy.

Neurophysiological studies of diabetic patients may show abnormalities even when clinical examination has revealed no sign of neuropathy. Quantitation of sensory function provides additional information when examining a patient with neuropathy. The value of the Hoffmann (H) reflex was investigated in diabetics who had undergone this examination. H-M intervals of the H-reflex, vibration perception thresholds (VPT's) and thermal discrimination thresholds (TDT's) were determined in 34 diabetics with clinical evidence of neuropathy and 16 diabetics without symptoms or signs of neuropathy. Normal values for VPT and TDT were obtained from the examination of 40 healthy subjects. The values of the H-M interval were significantly correlated with VPT's and not with TDT's. Three patients with clinical evidence of neuropathy and abnormal VPT's and TDT's had normal H-M intervals. For research purposes it is recommended that H-reflex studies are combined with the determination of sensory thresholds, but from a practical point of view determination of the H-M interval proved to be an effective tool for the investigation of neuropathy in diabetic patients.

Visual evoked potentials (VEPs) in senile dementia (Alzheimer type) and in non-organic behavioural disorders in the elderly; comparison with EEG parameters.

Forty-two patients with senile dementia of the Alzheimer type were compared with normal subjects (51) and with elderly patients with nonorganic psychiatric disorders (40). All were examined by EEG (routine visual inspection and power spectrum density analysis) and VEP (pattern reversal) testing. In dementia the late components (N130, P165, N220) of the VEP are delayed, but the EEG was abnormal more often than the VEP.

Somatosensory evoked potentials in healthy volunteers and in patients with dementia.

In 56 healthy volunteers short, middle and long latency somatosensory evoked potentials were recorded bilaterally. The median nerve was electrically stimulated at the wrist. The impact of arm length and age on the peak latencies of the identified SEP components was investigated. Arm length relates to shoulder and neck SEP and to the N20, the primary cortical response. Age relates to all components of the SEP. A pilot study was performed in a small number of patients with senile dementia. A significant delay of the middle and long latency potentials compared to healthy volunteers was shown.