Kevin R. Nelson

Literature review of the usefulness of repetitive nerve stimulation and single fiber EMG in the electrodiagnostic evaluation of patients with suspected myasthenia gravis or Lambert-Eaton myasthenic syndrome

A retrospective literature review of the electrodiagnosis of myasthenia gravis (MG) and Lambert–Eaton myasthenic syndrome (LEMS) through July 1998 was performed for the purpose of generating evidence‐based practice parameters. There were 545 articles identified, of which 13 articles met at least three of the six criteria set previously by the American Association of Electrodiagnostic Medicine (AAEM). An additional 21 articles were identified from review articles or the references of these first 13 articles leading to a total of 34 articles. Results of studies utilizing repetitive nerve stimulation (RNS) showed that a 10% decrement in amplitude from the first to fourth or fifth intravolley waveform while stimulating at 2–5 HZ is valid for the diagnosis of MG. The degree of increment needed for the diagnosis of LEMS is at least 25% but most accurate when greater than 100%. Abnormal jitter or impulse blocking are the appropriate criteria for diagnosis of neuromuscular junction (NMJ) disorders when using single fiber electromyography (SFEMG). SFEMG is more sensitive than RNS for the diagnosis of disorders of neuromuscular transmission, but may be less specific and may not be available. Therefore, RNS remains the preferred initial test for MG and LEMS.

Does the arousal system contribute to near death experience

The neurophysiologic basis of near death experience (NDE) is unknown. Clinical observations suggest that REM state intrusion contributes to NDE. Support for the hypothesis follows five lines of evidence: REM intrusion during wakefulness is a frequent normal occurrence, REM intrusion underlies other clinical conditions, NDE elements can be explained by REM intrusion, cardiorespiratory afferents evoke REM intrusion, and persons with an NDE may have an arousal system predisposing to REM intrusion. To investigate a predisposition to REM intrusion, the life-time prevalence of REM intrusion was studied in 55 NDE subjects and compared with that in age/gender-matched control subjects. Sleep paralysis as well as sleep-related visual and auditory hallucinations were substantially more common in subjects with an NDE. These findings anticipate that under circumstances of peril, an NDE is more likely in those with previous REM intrusion. REM intrusion could promote subjective aspects of NDE and often associated syncope. Suppression of an activated locus ceruleus could be central to an arousal system predisposed to REM intrusion and NDE.

Out-of-body experience and arousal

In a study of more than 13,000 Europeans, 5.8% reported the out-of-body experience (OBE) form of autoscopy.1 Occurring in diverse clinical settings, OBE is also typical of near death experience (NDE). NDE are responses to life-threatening crisis characterized by a combination of dissociation from the physical body, euphoria, and transcendental or mystical elements. Persons with NDE may have an arousal system predisposed to allowing intrusion of REM sleep elements during the transition between wakefulness and sleep.2 The arousal system is comprised of brainstem structures controlling or influencing sleep-wake states, alertness, and attention. REM intrusion manifests as the atonia of sleep paralysis (or cataplexy), as well as visual or auditory hallucinations. Although not considered REM intrusion, OBE and the REM state have an established relationship that is incompletely understood. In the state boundary disorder of narcolepsy, individuals often give accounts of OBE,3,4 which diminish after the narcolepsy is treated.4 In this study, we investigated if OBE in subjects with NDE could be regarded an arousal phenomenon by occurring during sleep transition or corresponding to REM intrusion. Structured interviews were conducted and REM intrusion measured in 55 subjects with NDE, and compared to age- and gender-matched controls as previously described.2 All gave informed consent as approved by the institutional review board. OBE during NDE was determined by the Greyson questionnaire asking if the respondent “Clearly left the body and existed outside it.” For OBE of sleep transition, subjects …

Acoustic nerve conduction abnormalities in Guillain‐Barré syndrome

We recorded brainstem auditory evoked potentials (BAEPs) in two patients with Guillain-Barré syndrome (GBS). One patient was acutely deaf with total absence of BAEP waveforms indicative of acoustic nerve conduction block. Hearing improved during early convalescence, and there were prolonged wave I latencies. Normal BAEPs were recorded on recovery. A second patient had bilaterally prolonged wave I latencies. These BAEP findings suggest that acoustic nerve conduction abnormalities from demyelination may occur in GBS.

Near-death experience: arising from the borderlands of consciousness in crisis

Brain activity explains the essential features of near‐death experience, including the perceptions of envelopment by light, out‐of‐body, and meeting deceased loved ones or spiritual beings. To achieve their fullest expression, such near‐death experiences require a confluence of events and draw upon more than a single physiological or biochemical system, or one anatomical structure. During impaired cerebral blood flow from syncope or cardiac arrest that commonly precedes near‐death, the boundary between consciousness and unconsciousness is often indistinct and a person may enter a borderland and be far more aware than is appreciated by others. Consciousness can also come and go if blood flow rises and falls across a crucial threshold. During crisis the brains prime biologic purpose to keep itself alive lies at the heart of many spiritual experiences and inextricably binds them to the primal brain. Brain ischemia can disrupt the physiological balance between conscious states by leading the brainstem to blend rapid eye movement (REM) and waking into another borderland of consciousness during near‐death. Evidence converges from many points to support this notion, including the observation that the majority of people with a near‐death experience possess brains predisposed to fusing REM and waking consciousness into an unfamiliar reality, and are as likely to have out‐of‐body experience while blending REM and waking consciousness as they are to have out‐of‐body experience during near‐death.

Vignette. Duchenne de Boulogne and the muscle biopsy.

ment was inspired by his experience with &dquo;Mideldorff’s harpoon,&dquo; a device used in Germany to study trichinosis in human muscles, but found by Duchenne to be painful and to retrieve inadequate specimens. Mindful of the complications encountered by Griesinger and Billroth following the first open muscle biopsy (in a case of pseudohypertrophic paralysis), Duchenne wrote: This is why I have designed a little instrument that I called the

Motor unit potential analysis in carnitine palmitoyl transferase deficiency

To the Editor: Carnitine palmitoyl transferase is responsible for the transport of long-chain fatty acids into the mitochondria for 0-oxidation. Normal muscle preferentially metabolizes fatty acids during prolonged exertion or fasting. Under such conditions, muscle fibers with carnitine palmitoyl transferase deficiency accumulate lipid and may undergo rhabdomyolysis, producing electromyographic abnormalities. We studied the motor-unit potential in a fasting patient with carnitine palmitoyl transferase deficiency, at rest and after exercise of insufficient duration to induce rhabdomyolysis, to determine if there are physiologic effects of carnitine palmitoyl transferase deficiency independent of rhabdomyolysis.

Experiencing death: an insider's perspective

For millennia, human beings have wondered what happens after death. What is the first‐person experience of dying and being brought back to life? Technological advances in resuscitation science have now added an intriguing new chapter to the literature of out‐of‐body or near‐death experiences by eliciting detailed and vivid accounts of those who have approached the threshold of death. Steve Paulson, executive producer and host of To the Best of Our Knowledge, moderated a discussion that included neurologist Kevin Nelson, neuropsychiatrist Peter Fenwick, emergency medicine expert Sam Parnia, and orthopedic surgeon and drowning survivor Mary Neal; they share some remarkable stories and discuss how they analyze such experiences in light of their own backgrounds and training. The following is an edited transcript of the discussion from December 11, 2013, 7:00–8:30 PM, at the New York Academy of Sciences in New York City.