Nerve biopsy in children with severe Guillain-Barré syndrome and inexcitable motor nerves.
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Biopsy↗
Biomedical subjects
M R Swenson
Publications and source records attributed to M R Swenson.
Right frontal lobe slow frequency repetitive transcranial magnetic stimulation (SF r-TMS) is an effective treatment for depression: a case-control pilot study of safety and efficacy.
Major depression may result from decreased left frontal lobe function with respect to the right. Fast frequency repetitive transcranial magnetic stimulation (FF r-TMS) excites the underlying cortex whereas slow frequency repetitive transcranial magnetic stimulation (SF r-TMS) causes cortical inhibition. Left frontal FF r-TMS attenuates major depression whereas the inhibitory effects of right frontal SF r-TMS are unknown. This study tested the hypothesis that right frontal SF r-TMS would treat depressed patients with minimal effect on controls. A psychiatrist administered the Beck depression inventory and Hamilton D depression rating scales to eight depressed patients and six controls before and after the treatment protocol. Eight sessions of 100 right frontal lobe SF r-TMS were given at motor threshold and 0.5 Hz over a 6 week period. No adverse outcomes were noted in either group. A significant antidepressant effect was noted in depressed patients on the Beck and Hamilton D depression rating scales (p<0.05). No change on either scale was noted in the controls. In conclusion right frontal lobe SF r-TMS is a safe, non-invasive treatment for major depression that deserves further investigation.
Adult↗
Is there a "subcortical" profile of attentional dysfunction? A comparison of patients with Huntington's and Parkinson's diseases on a global-local focused attention task.
This study investigated focused attention in two subcortical degenerative disorders by examining the performance of patients with Huntington's disease (HD) and Parkinson's disease (PD) on a task utilizing global-local stimuli. Participants were presented with global-local figures and were instructed to focus their attention on either the global or local level. Stimuli were either "consistent", with the same form at the global and local levels, or "inconsistent", with different forms at the global and local levels. It was found that response times (RTs) of patients with PD were comparable to those of similarly-aged controls regardless of stimulus consistency. In contrast, patients with HD demonstrated disproportionately longer RTs to inconsistent stimuli relative to their age-matched control group. Difference scores between RTs for inconsistent versus consistent stimuli were not correlated with overall level of dementia or disease severity for either the HD or PD group. These results provide further evidence for the heterogeneity of attentional dysfunction among subcortical degenerative illnesses.
Adult↗
Botulinum toxin type B: a double-blind, placebo-controlled, safety and efficacy study in cervical dystonia.
We enrolled and treated 122 patients with idiopathic cervical dystonia in a double-blind, placebo-controlled safety and efficacy study of botulinum toxin type B (BotB). Both A-responsive and A-resistant patients were enrolled. Patients received intramuscular injections of either BotB (2,500 U, 5,000 U, or 10,000 U) or placebo. The primary outcome measure of efficacy was the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS)-Total score at 4 weeks following study drug administration. Secondary measures of efficacy were TWSTRS-Severity, -Disability, and -Pain subscale scores, and Analog Pain Assessment, Investigator Global Assessment, Patient Global Assessment, and Sickness Impact Profile scores. Duration of effect was estimated with an intent-to-treat analysis of responders. Safety measures included clinical parameters, laboratory tests, and adverse events. The primary and most of the secondary analyses indicated a statistically significant treatment effect and a dose response. BotB is safe, well tolerated, and efficacious in the treatment of cervical dystonia at the doses tested.
Adult↗
Diabetic peripheral neuropathy.
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Diabetic Neuropathies↗
Discrimination of cortical from subcortical dementias on the basis of memory and problem-solving tests.
This study compared the discriminative utility of problem-solving and memory tasks in patients with Alzheimer's and Huntington's disease and in age-, education-, and gender-matched normal control subjects. Problem-solving was assessed with a modified version of the Wisconsin Card Sorting Test. Memory was measured with a 10-item, 6-trial version of the Buschke Selective Reminding Test. Receiver Operating Characteristic curves were plotted to determine which measure provided the highest sensitivity (i.e., hit rate) and specificity (i.e., correct rejection rate). Both tests provided excellent detection of dementia (88 to 98% classification accuracy), but were less robust in differentiating between dementia groups. Findings underscore the suitability of both measures to detect mild dementia, but emphasize the importance of specific memory measures to differentiate between cortical and subcortical dementia.
Adult↗
Impaired prepulse inhibition of acoustic and tactile startle response in patients with Huntington's disease.
The corpus striatum serves a critical function in inhibiting involuntary, intrusive movements. Striatal degeneration in Huntington's disease results in a loss of motor inhibition, manifested by abnormal involuntary choreiform movements. Sensorimotor inhibition, or "gating", can be measured in humans using the startle reflex: the startle reflex is normally inhibited when the startling stimulus is preceded 30-500 ms earlier by a weak prepulse. In the present study, prepulse inhibition (PPI) was measured in patients with Huntington's disease to quantify and characterise sensorimotor gating. Compared with age matched controls, patients with Huntington's disease exhibit less PPI. Startle gating deficits are evident in patients with Huntington's disease when startle is elicited by either acoustic or tactile stimuli. Even with stimuli that elicit maximal PPI in normal subjects, patients with Huntington's disease exhibit little or no PPI, and their pattern of startle gating does not show the normal modulatory effects usually elicited by changing the prepulse interval or intensity. Startle amplitude and habituation and latency facilitation are largely intact in these patients, although reflex latency is significantly slowed. In patients with Huntington's disease, startle reflex slowing correlates with cognitive impairment measured by the dementia rating scale, and with the performance disruptive effects of interference measured by the Stroop test. These findings document a profound disruption of sensorimotor gating in patients with Huntington's disease and are consistent with preclinical findings that identify the striatum and striatopallidal GABAergic efferent circuitry as critical substrates for sensorimotor gating of the startle reflex.
Acoustic Stimulation↗
Distinct cognitive profiles of cortical and subcortical dementia in advanced illness.
We administered the Mattis Dementia Rating Scale (DRS) to 120 patients to evaluate the effect of dementia severity on distinct cognitive profiles. Sixty patients with Huntington's disease (HD) and 60 patients with Alzheimer's disease (AD) were separated by dementia severity into three groups: mildly demented (DRS mean total = 129), moderately demented (DRS mean total = 117), and severely demented (DRS mean total = 102). At all levels of dementia severity, HD patients demonstrated greater impairment than AD patients on the Initiation/Perseveration subscale, whereas AD patients demonstrated greater impairment than HD patients on the Memory subscale. At moderate and severe levels of dementia, HD patients demonstrated an additional impairment in constructional praxis. These profile differences were independent of dementia severity and continued to differentiate between so-called cortical and subcortical dementias in later stages of dementia severity.
Adult↗
Diabetic peripheral neuropathy.
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Autonomic Nervous System Diseases↗
The effects of induced hypertension and acute graded compression on impulse propagation in the spinal nerve roots of the pig.
Injuries caused by compression of spinal nerve roots are frequently encountered clinically. Experimental studies show that several different factors affect the pathophysiologic changes that occur after these injuries. However, the effect of hypertension in conjunction with graded compression of spinal nerve roots is yet unclear. A previously established porcine model was employed, in which the spinal nerve roots were exposed and compressed by an inflatable balloon. Impulse propagation across the compressed nerve segment was studied by the recording of efferent and afferent nerve action potentials, and nerve conduction velocity. The systemic blood pressure was increased by administration of Neo-Synephrine hydrochloride (phenylephrine HCl) (Winthrop Pharmaceuticals, New York, NY) and elevated 40 +/- 5 mm Hg above the normal (100 +/- 5 mm Hg), and electrophysiologic baseline values were recorded. The spinal nerve roots were then compressed for 2 hours with either 0 (control), 50, 100, or 200 mm Hg. The balloon was deflated and the nerve roots were allowed to recover for 1.5 hours. Impulse propagation was studied every 15 minutes and hypertension was maintained throughout the experiment. The results showed no significant changes of the efferent and afferent nerve action potentials at 0.50 or 100 mm Hg. At 200 mm Hg, efferent and afferent nerve action potentials decreased rapidly and were almost abolished within 20 minutes of compression. Some but not significant recovery was seen of the nerve impulse. Compared to data from normotensive pigs in an earlier experiment, the current study showed that hypertension significantly decreases the susceptibility of the spinal nerve roots to compression at and below 100 mm Hg.(ABSTRACT TRUNCATED AT 250 WORDS)
Action Potentials↗
Effects of local compression on peroneal nerve function in humans.
A new apparatus was developed to compress the anterior compartment selectively and reproducibly in humans. Thirty-five normal volunteers were studied to determine short-term thresholds of local tissue pressure that produce significant neuromuscular dysfunction. Local tissue fluid pressure adjacent to the deep peroneal nerve was elevated by the compression apparatus and continuously monitored for 2-3 h by the slit catheter technique. Elevation of tissue fluid pressure to within 35-40 mm Hg of diastolic blood pressure (approximately 40 mm Hg of in situ pressure in our subjects) elicited a consistent progression of neuromuscular deterioration including, in order, (a) gradual loss of sensation, as assessed by Semmes-Weinstein monofilaments, (b) subjective complaints, (c) reduced nerve conduction velocity, (d) decreased action potential amplitude of the extensor digitorum brevis muscle, and (e) motor weakness of muscles within the anterior compartment. Generally, higher intracompartmental pressures caused more rapid deterioration of neuromuscular function. In two subjects, when in situ compression levels were 0 and 30 mm Hg, normal neuromuscular function was maintained for 3 h. Threshold pressures for significant dysfunction were not always the same for each functional parameter studied, and the magnitudes of each functional deficit did not always correlate with compression level. This variable tolerance to elevated pressure emphasizes the need to monitor clinical signs and symptoms carefully in the diagnosis of compartment syndromes. The nature of the present studies was short term; longer term compression of myoneural tissues may result in dysfunction at lower pressure thresholds.
Adult↗
Phrenic nerve conduction studies.
To refine the technique of phrenic nerve conduction, we first studied electrode positioning and sources of chest wall artifact. Diaphragmatic compound motor action potentials (DCMAPs) were mapped at close intervals over 4 hemithoraces of two subjects, finding optimum recording sites which were then used to quantitate artifacts due to EKG, chest wall EMG, and configurational thoracic changes of respiration. Based on these findings, 20 normal subjects were studied, showing ease of application and good side-to-side agreement for DCMAP latencies; but, in contrast to prior reports, right-to-left correlation for amplitude and waveform was poor, making the unaffected side an unreliable standard in unilateral partial phrenic nerve lesions.
Action Potentials↗
Effects of magnitude and duration of compression on spinal nerve root conduction.
Spinal nerve root compression occurs commonly in conditions such as herniated nucleus pulposus, spinal stenosis, and trauma. However, the pathophysiology of the symptoms and signs related to spinal nerve root compression is poorly understood. The purpose of the present study was to assess and compare effects of various pressures and durations of acute compression on spinal nerve root conduction in the pig cauda equina. Efferent conduction (compound motor action potentials) and afferent conduction (compound nerve action potentials) were monitored during compression for 2 or 4 hours with compression pressures of 0 (sham), 50, 100, or 200 mm Hg. Recovery from compression was monitored for 1.5 hours. No significant deficits in spinal nerve root conduction were observed with 0 or 50 mm Hg compression, compared to significant conduction deficits induced by 100 and 200 mm Hg compression. Three-way analysis of variance demonstrated significant effects of compression pressure and duration on conduction at the end of compression and recovery, with a significant difference between efferent and afferent conduction at the end of the recovery period. These observations suggest an interaction between biomechanical and microvascular mechanisms in the production of nerve root conduction deficits. Such information may relate to the motor and sensory dysfunction in clinical conditions associated with spinal nerve root compression.
Action Potentials↗
Neurophysiologic studies of the peripheral nervous system in nephropathic cystinosis.
Cystinosis is an autosomal recessive metabolic disorder in which nonprotein cystine accumulates within most body tissues due to a defect in lysosomal cystine transport. Neurologic declarations are only recently being recognized. We studied 13 cystinotic subjects (aged 5 to 21 years old), determining median motor and sensory nerve conduction velocities, F waves, peroneal motor nerve conduction velocities, sural sensory nerve conduction velocities, median sympathetic skin response, electrocardiogram R-to-R variability, and blink reflex analysis. The results were normal. We conclude that neurophysiologic testing suggests relative sparing of the peripheral nervous system in nephropathic cystinosis.
Adolescent↗
Dispersion or block?
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Action Potentials↗
Effects of acute, graded compression on spinal nerve root function and structure. An experimental study of the pig cauda equina.
A well-controlled experimental model for analysis of compression-induced functional changes of the porcine cauda equina is presented. The model allows for electrophysiologic investigation of a variety of neurophysiologic changes induced by nerve root deformation. At an acute pressure threshold of 50-75 mm Hg, changes in both afferent and efferent conduction are induced. With higher compression pressure, a differential recovery in afferent and efferent conduction is seen.
Action Potentials↗
Eales' disease with central nervous system infarction.
Eales' disease is a noninflammatory occlusive disorder of the retinal vasculature that causes recurrent hemorrhages into the retina and vitreous and ischemic changes in the eye. Extraocular manifestations of Eales' disease are rare and limited to the central nervous system. We report the case of a patient with Eales' disease and ischemic stroke, and we review the neurologic manifestations of this primarily ophthalmologic vasculopathy.
Cerebral Infarction↗