The number of acetylcholine receptors was determined in the neuromuscular junctions of eight patients with typical myasthenia gravis and in five controls, by means of (125)1-labeled alpha-bungarotoxin binding. The junctional acetylcholine receptors were reduced in the myasthenic muscles as compared with the controls. This reduction in receptors may account for the defect in neuromuscular transmission in myasthenia gravis.

Purpose of review: The landscape of genetic diagnostic testing has changed dramatically with the introduction of next-generation clinical exome sequencing (CES), which provides an unbiased analysis of all protein-coding sequences in the roughly 21,000 genes in the human genome. Use of this testing, however, is currently limited in clinical neurologic practice by the lack of a framework for appropriate use and payer coverage. Recent findings: CES can be cost-effective due to its high diagnostic yield in comparison to other genetic tests in current use and should be utilized as a routine diagnostic test in patients with heterogeneous neurologic phenotypes facing a broad genetic differential diagnosis. CES can eliminate the need for escalating sequences of conventional neurodiagnostic tests. Summary: This review discusses the role of clinical exome sequencing in neurologic disease, including its benefits to patients, limitations, appropriate use, and billing. We also provide a reference template policy for payer use when considering testing requests. Neurol Clin Pract 2016;6:164-176

The electrical response of muscle to repetitive nerve stimulation was studied in patients with various myotonic disorders. A decrementing response was common but not invariable finding, and was unrelated to the severity or diagnosis. The decrement either continued throughout the period of stimulation or "leveled off", sometimes being followed by an increment. If it occurred at low rates of stimulation, a greater decrement occurred at higher rates, usually after a shorter latent period. It was not related consistently to the presence of weakness, but in patients with myotonia congenita it was more conspicuous and elicited by lower rates of stimulation when transient weakness was a feature of the history.

We performed behavioral audiometric tests and brainstem auditory evoked potentials in four patients with Friedreich ataxia. None of the patients had symptomatic hearing difficulties. Results of the audiometric tests pointed to a disorder of the eighth nerve. In none of the patients could we elicit normal-appearing waves of the brainstem auditory evoked potentials. These abnormalities could be attributed to degeneration of spiral ganglion neurons. Our patients had useful and functional hearing despite very abnormal brainstem auditory evoked potentials.