Barbara R. Wolgamuth

Association between the Epworth Sleepiness Scale and the Multiple Sleep Latency Test in a Clinical Population

No statistically or clinically significant association was seen between scores on the subjective Epworth Sleepiness Scale and results of the objective mean sleep latency test. These tests may evalu...

Clinical response to varying the stimulus parameters in deep brain stimulation for essential tremor

Deep brain stimulation (DBS) of the ventral intermediate nucleus of the thalamus for essential tremor is sometimes limited by side effects. The mechanisms by which DBS alleviates tremor or causes side effects are unclear; thus, it is difficult to select stimulus parameters that maximize the width of the therapeutic window. The goal of this study was to quantify the impact on side effect intensity (SE), tremor amplitude, and the therapeutic window of varying stimulus parameters. Tremor amplitude and SE were recorded at 40 to 90 combinations of pulse width, frequency, and voltage across 14 thalami. Posterior variable inclusion probabilities indicated that frequency and voltage were the most important predictors of both SE and tremor amplitude. The amount of tremor suppression achieved at frequencies of 90 to 100 Hz was not different from that at 160 to 170 Hz. However, the width of the therapeutic window decreased significantly and power consumption increased as frequency was increased above 90 to 100 Hz. Improved understanding of the relationships between stimulus parameters and clinical responses may lead to improved techniques of stimulus parameter adjustment.

Histopathological Correlates of Epileptogenicity as Expressed by Electrocorticographic Spiking and Seizure Frequency

Summary: Purpose: To study the correlation between histopathology and epileptogenicity, as measured by seizure frequency and electrocorticography (EcoG), in patients with cortical dysplasia (CD) as compared with control patients with gangliogliomas or gliomas.

Probabilistic analysis of activation volumes generated during deep brain stimulation

Deep brain stimulation (DBS) is an established therapy for the treatment of Parkinsons disease (PD) and shows great promise for the treatment of several other disorders. However, while the clinical analysis of DBS has received great attention, a relative paucity of quantitative techniques exists to define the optimal surgical target and most effective stimulation protocol for a given disorder. In this study we describe a methodology that represents an evolutionary addition to the concept of a probabilistic brain atlas, which we call a probabilistic stimulation atlas (PSA). We outline steps to combine quantitative clinical outcome measures with advanced computational models of DBS to identify regions where stimulation-induced activation could provide the best therapeutic improvement on a per-symptom basis. While this methodology is relevant to any form of DBS, we present example results from subthalamic nucleus (STN) DBS for PD. We constructed patient-specific computer models of the volume of tissue activated (VTA) for 163 different stimulation parameter settings which were tested in six patients. We then assigned clinical outcome scores to each VTA and compiled all of the VTAs into a PSA to identify stimulation-induced activation targets that maximized therapeutic response with minimal side effects. The results suggest that selection of both electrode placement and clinical stimulation parameter settings could be tailored to the patients primary symptoms using patient-specific models and PSAs.

Amplitude- and Frequency-Dependent Changes in Neuronal Regularity Parallel Changes in Tremor With Thalamic Deep Brain Stimulation

The mechanisms by which deep brain stimulation (DBS) alleviates tremor remain unclear, but successful treatment can be achieved with properly selected frequency and amplitude. The clinical tremor response to thalamic DBS for essential tremor is dependent on the stimulation frequency and amplitude, and for high frequencies (ges90 Hz), increasing amplitude suppressed tremor, whereas for low frequencies (<60 Hz), increasing amplitude aggravated tremor. We studied the effects of stimulation frequency and amplitude on the output of a population of intrinsically active model neurons to test the hypothesis that regularization of neuronal firing patterns is responsible for the clinical effectiveness of DBS. The firing patterns of model thalamocortical neurons were dependent on stimulation frequency and amplitude in a manner similar to the clinical tremor response. Above a critical frequency, increasing amplitude reduced the coefficient of variation (CV) of the neuronal firing pattern, whereas for low frequencies, increasing the amplitude increased the CV of neuronal activity. The correlation between the changes in tremor and the changes in the C V of neuronal firing supports the hypothesis that regularization of neuronal firing pattern during DBS is one of the mechanisms underlying the suppression of tremor.

Staring spells in children: Descriptive features distinguishing epileptic and nonepileptic events☆☆☆★

OBJECTIVE To identify questions sensitive and specific for staring spells of epileptic (absence seizures [AS]) or nonepileptic etiology to increase the yield of history taking. STUDY DESIGN A questionnaire was completed by parents of 40 children who presented with staring spells. Results from 17 children with AS and 23 with nonepileptic staring (NES) were compared. RESULTS Features with moderate sensitivity (43% to 56%) but high specificity (87% to 88%) for NES included preserved responsiveness to touch, lack of interruption of playing, and initial identification by a teacher or health professional. These features were more frequent in NES than in AS (P = .013, .016, .030). Body rocking occurred only in NES, but sensitivity was low (13%). Features with high specificity (91% to 100%) for AS included limb twitches, upward eye movements, and urinary incontinence; but sensitivities were low (13% to 35%). CONCLUSION In children with normal interictal electroencephalography findings and without neurologic disease, staring spells are most likely nonepileptic when parents report preserved responsiveness to touch, body rocking, or initial identification by a teacher or health professional without limb twitches, upward eye movements, interruption of play, or urinary incontinence. In these cases a diagnosis of NES may be confidently applied, with confirmation based on long-term follow-up.

Risk Factors for Unsuccessful Testing During the Intracarotid Amobarbital Procedure in Preadolescent Children

Summary: Purpose: Identification of risk factors for unsuccessful testing during intracarotid amobarbital procedure (IAP) in preadolescent children.

A Model Predicting Optimal Parameters for Deep Brain Stimulation in Essential Tremor

Summary: In nine patients with essential tremor (14 thalami), the authors varied frequency, voltage, and pulsewidth of thalamic deep brain stimulation, and quantified postural tremor. Low frequency stimulation aggravated tremor; the effect increased with increasing voltage. High frequency stimulation had a U-shaped relation to voltage, with minimum tremor at an optimal voltage characteristic of the individual thalamus and increases in voltage beyond the optimum reduced tremor suppression. Based on the hypothesis that tremor response to deep brain stimulation resulted from two competing processes, the authors successfully modeled the relationship of tremor to voltage and frequency of stimulation using a mathematical model. The optimum voltage predicted by the model agreed with the empirically measured value. Moreover, the model made accurate predictions at high stimulation frequency based on measurements made at low stimulation frequency. Our results indicate there is an optimal voltage for tremor suppression by thalamic deep brain stimulation in most patients with essential tremor. The optimum varies across patients, and this is related to electrode position. A mathematical model based on “competing processes” successfully predicts optimum voltage in individual patients. This supports a competing processes model of deep brain stimulation effects.

Prevalence of daytime sleepiness in a population of drivers

The prevalence of excessive daytime sleepiness in the general population is generally quoted to be between 0.5 and 5%, but even wider ranges can be found, from 0.3 to 13%.1 This rather wide range is due to the variability in methodologies and populations used. Because “the sleepy driver” is a well-recognized public health hazard,2 we sought to estimate the prevalence of sleepiness at a department of motor vehicles. We administered the Epworth Sleepiness Scale (ESS) to 620 consecutive individuals 16 years or older who presented to the Department of Motor Vehicles in Madison, WI, for various reasons related to driving. The ESS is an 8-item questionnaire where each question is answered with a score from 0 (would never doze) to 3 (high chance of dozing), yielding a total between 0 (minimum) and 24 (maximum sleepiness). Questions inquire into the tendency to fall asleep during the following circumstances: 1) sitting and reading, 2) watching TV, 3) sitting inactive in a …

Bálint-like syndrome as an unusual representation of non-convulsive status epilepticus

The clinical signs of posterior cortex dysfunction are, due to their paucity and subtlety, very often ignored as non-specific during clinical evaluation of non-convulsive status epilepticus. Therefore, focal non-convulsive status epilepticus emerging from the posterior cortex, and especially the parietal lobes, can be fairly under-recognised. We report a 66-year-old patient with focal non-convulsive status epilepticus presenting as isolated Bálint-like syndrome, successfully treated to full clinical and electrophysiological recovery. The diagnostic and pathophysiological features are discussed. Focal non-convulsive status epilepticus can be associated with negative phenomena such as neuropsychological deficits mimicking those detected more often in degenerative and vascular brain diseases.