Andrew L. Chesson

Alterations in brain electrical activity caused by magnetic fields: detecting the detection process

Static and 60 Hz magnetic fields, 0.78 gauss, were applied individually and combined to each of 20 human subjects during 2 sec epochs, and the effect on the EEG was determined by comparing the power spectrum obtained during field exposure with that from control epochs. All but one subject exhibited field-induced alterations in the EEG; most subjects exhibited increased EEG activity at 2 or more frequencies within 1-18.5 Hz. The field-induced changes were recorded more often at the central and parietal electrodes than at the occipital electrodes. The responses observed during application of combined static and alternating fields did not differ from the sum of the responses observed when the fields were applied individually, even though the exposure conditions were specifically chosen to favor the hypothesized ion-resonance mechanism of interaction involving Ca2+. The data support the view that detection loci for magnetic fields exist within the nervous system.

Electrical states in the rabbit brain can be altered by light and electromagnetic fields

The effect of low-frequency magnetic fields on the rabbit electroencephalograph (EEG) was studied using a quantitative procedure that permitted statistical evaluation of the response of individual animals. The field conditions used were those predicted by various theories to result in field-animal interactions; light and sham exposure were employed as positive and negative controls, respectively. Sixty-seven percent of the rabbits exhibited changes in the EEG power spectra when light was presented in 2-s epochs; none of the animals responded to sham exposure. When 1 Gauss, 5 Hz, was presented in 2-s epochs, 100% of the animals tested responded to the presence of the field. The rabbits did not respond when the magnetic-field frequency was higher than the physiological range (1-20 Hz) or when it was tuned for resonance of K+. The results showed that an electrical state function may be operationally defined for the rabbit brain, and used to assess the occurrence of an interaction between an animal and external magnetic fields.

Frequency-specific responses in the human brain caused by electromagnetic fields

The effects of 1.5- and 10-Hz electromagnetic fields (EMFs), 0.2-0.4 gauss, on the intrinsic electrical activity of the human brain at these frequencies was studied. Each of 19 subjects exposed for 2-sec epochs exhibited altered brain electrical activity at the frequency of the EMF during the time of stimulation, as determined by spectral analysis of the electroencephalogram. Since brain activity at specific frequencies could be altered by applied EMFs, the results suggest that it may be possible to use EMFs to determine whether particular intrinsic frequencies subserve specific physiological or behavioral responses.

Restless legs syndrome in the older adult: Diagnosis and management

Restless legs syndrome (RLS) is common in the elderly, with an estimated prevalence of 10 to 35% in individuals over 65 years of age. RLS is characterised by paraesthesias and dysaesthesias of the legs, typically occurring in the evening. The symptoms occur at rest and result in motor restlessness; movement often temporarily relieves the symptoms. Patients with poorly controlled RLS may develop related problems including insomnia (due to sleep-onset restlessness or periodic limb movements or related sleep fragmentation) and depression. RLS can be a primary disorder that develops in the young and includes familial cases. Secondary RLS occurs in association with iron-deficiency anaemia, uraemia and polyneuropathies. Typically, RLS is misdiagnosed or undiagnosed for years. In the elderly, both primary and secondary types of the disorder are common.It is thought that RLS represents lower CNS levels of, or reduced responsiveness to, dopamine. The symptoms improve with dopaminergic therapy. Ergotamine dopamine-receptor agonists such as pergolide, and the non-ergotamine dopamine-receptor agonists pramipexole and ropinirole, are becoming more commonly used to treat RLS. The dopamine precursor levodopa, in combination with carbidopa, is another effective therapeutic agent. An advantage of levodopa is lower cost than non-ergotamine and ergotamine dopamine-receptor agonists. However, the adverse effect of symptom augmentation appears to develop more frequently with levodopa than dopamine-receptor agonists; therefore, levodopa may currently be used somewhat less often as first-line therapy. Patients with painful symptoms may respond favourably to the anticonvulsants gabapentin and carbamazepine. Opioids and hypnosedatives are helpful in selected patients; however, these agents may have troubling adverse effects in the elderly. Correction of iron deficiency improves symptoms in patients with low ferritin levels. Lifestyle modification may also be helpful. Therapy is directed at symptoms, and most symptomatic patients benefit from treatment. It is important to consider RLS in the differential diagnosis of any patient with paraesthesias of the limbs.

The link between vitamin D metabolism and sleep medicine.

Vitamin D is a hormone that interacts with intranuclear receptors to effect transcriptional changes in many cell types including those in gut, bone, breast, prostate, brain, skeletal muscle, and the immune system. Inadequacy of vitamin D is widely prevalent, and leads to the classic diseases of bone demineralization as well as to more recently recognized problems such as nonspecific pain and noninflammatory skeletal myopathy, which may disrupt sleep and directly cause daytime impairment. Emerging lines of evidence suggest that low vitamin D levels increase the risk for autoimmune disease, chronic rhinitis, tonsillar hypertrophy, cardiovascular disease, and diabetes. These conditions are mediated by altered immunomodulation, increased propensity to infection, and increased levels of inflammatory substances, including those that regulate sleep, such as tumor necrosis factor alpha (TNF-α), interleukin (IL)-1, and prostaglandin D2 (PD2). Together, the recent reports suggest a role for inadequate vitamin D in the development of symptoms of wake impairment commonly associated with sleep disorders. Persistent inadequacy of vitamin D may also increase the risk for obstructive sleep apnea via promotion of adenotonsillar hypertrophy, airway muscle myopathy, and/or chronic rhinitis. Much remains to be learned concerning the complex relationship between chronically low levels of vitamin D, normal sleep, sleep disruption, and daytime neurocognitive impairment.

Low-level EMFs are transduced like other stimuli.

The aims of this study were to test the theory that transduction of low-level electromagnetic fields (EMFs) is mediated like other stimuli, and to determine the false-negative rate of the method used to assess the occurrence of transduction (intra-subject comparison of stimulus and non-stimulus states (ICOS)). A light stimulus was chosen as a basis of comparison because light could be applied and removed at precise time points, similar to the manner in which EMFs were controlled. Subjects exposed to a weak light stimulus during 2-second epochs exhibited alterations in brain electrical activity that were similar to those previously observed in subjects exposed to EMFs. The false-negative rate of the ICOS method was 61%, since it registered an effect in only 39% of the subjects (11/28) whereas all subjects were actually aware of the light. In a second group of subjects that were exposed to 0.8 G (1.5 or 10 Hz), 58% (11/19) exhibited similar alterations in brain activity, as determined using ICOS. Previous measurements in the same subjects using a different method showed that the EMFs actually affected brain electrical activity in all subjects; consequently, the false-negative rate was 42% when an EMF was used as the stimulus. The results suggested that the post-transduction brain electrical processes in human subjects were similar in the cases of EMF and light stimuli, as hypothesized, and that the high negative rate of the ICOS method (here and in previous studies) was composed partly or entirely of false-negative results.

Computer quantitation of saturation impairment time as an index of oxygenation during sleep

The measurement of oxygenation during sleep has become a standard procedure in the assessment of hypoxemia in patients with various disorders. However, an accepted method for quantitating this hypoxemia is not available. This study describes the development of computerized data acquisition and analysis programs to quantitate nocturnal hypoxemia in patients with sleep and breathing disorders. The acquisition program samples the voltage output from pulse oximeters used to measure oxyhemoglobin saturation (SpO2) and stores this on an IBM PC or compatible computer. The analysis program integrates the SpO2 over time below the patients pretest baseline as well as the integral below 90, 80, 70, 60 and 50% saturation. We refer to each integral as Saturation Impairment Time or SIT. In order to compare these integrals between patients or between the same patient but different studies, the integral is divided by the total sleep study time. We refer to each of these integrals, corrected for sleep study time, as the SIT index. Evaluation of the SIT index in 10 consecutive patients referred for various sleep disorders revealed acquisition program detection and deletion of 48 of 57 (86%) oximeter probe artifacts (mean duration of 3 seconds for undetected artifacts). There were no significant artifacts in the analysis program calculation of the SIT index in these same patients. In conclusion, computer programs were developed to measure and quantitate oxygen saturation measured by oximeters. Preliminary results reveal an accuracy of measurement which should prove acceptable in further clinical evaluations.

Aphasia following a right thalamic hemorrhage

A left-handed patient with a right thalamic hemorrhage and disordered speech is described. Sequential examinations and aphasia testing were done during a 1-year follow-up period and the results are reported. This case supports those authors who have described characteristics they feel are helpful in diagnosing disordered speech associated with thalamic lesions. Paucity of speech, reduced voice volume, anomia, some paraphasia, and severe dysgraphia were present, but comprehension and repetition were relatively preserved. She showed modest improvement with time. This case also confirms that thalamic involvement in speech is a dominant, rather than a specifically left hemispheric function.

Brachial neuritis with bilateral diaphragmatic paralysis following herpes zoster: a case report.

We present a case of supine respiratory failure due to a bilateral diaphragmatic paralysis associated with brachial neuritis secondary to thoracic herpes zoster. Fluoroscopy in both the standing and supine positions revealed bilateral diaphragmatic paralysis accentuated in the supine position. To our knowledge, this is the first case of thoracic herpes zoster associated with brachial neuritis and bilateral diaphragmatic paralysis.

Sleep-wake pattern following gunshot suprachiasmatic damage.

BACKGROUND The suprachiasmatic nucleus (SCN) plays a critical role in maintaining melatonin and sleep-wake cycles. METHODS/PATIENT We report a case of 38-year-old woman who, after gunshot wound to the right temple, developed a sleep complaint of multiple nocturnal awakenings and several naps throughout the day. RESULTS Computerized tomography and magnetic resonance imaging revealed bilateral optic nerve and optic chiasm damage. Diagnostic polysomnography and actigraphy revealed an irregular sleep wake rhythm. CONCLUSIONS We speculate concurrent damage of the SCN and optic nerves bilaterally resulted in the posttraumatic irregular sleep-wake rhythm.