Shin J. Oh

BASIC SECTION Anatomical & Physiological Basis for Electromyography Studies General Concepts of Electrodiagnostic Studies in Neuromuscular Disease Basic Components of Electromyography Instruments Nerve Conduction Techniques Anatomical Guide for Common nerve Conduction Study Required Tests for Specific Problems Normal Values for Common Nerve Conduction Tests Pediatric Nerve Conduction Studies Artifacts Electrical Safety and Risks in Electrodiagnostic Medicine ADVANCED SECTION Uncommon Nerve Conduction Studies: Techniques and Normal Values Nonphysiological Factors Affecting Nerve Conduction Physiological Factors Affecting Nerve Conduction Anomalous Innervation Near-Nerve Needle Technique in Sensory Nerve Conduction Intraoperative Nerve Conduction Reflex Tests Special Nerve Conduction Techniques Magnetic and Electrical Stimulation Tests Somatosensory Evoked Potentials in Peripheral Nerve Lesions Interpretation of Nerve Conduction Data Nerve Conduction in Focal Neuropathies Nerve Conduction in Polyneuropathies Traumatic Peripheral Nerve Injuries Index

BACKGROUND: Danon disease is due to primary deficiency of lysosome-associated membrane protein-2. OBJECTIVE: To define the clinicopathologic features of Danon disease. METHODS: The features of 20 affected men and 18 affected women in 13 families with genetically confirmed Danon disease were reviewed. RESULTS: All patients had cardiomyopathy, 18 of 20 male patients (90%) and 6 of 18 female patients (33%) had skeletal myopathy, and 14 of 20 male patients (70%) and one of 18 female patients (6%) had mental retardation. Men were affected before age 20 years whereas most affected women developed cardiomyopathy in adulthood. Muscle histology revealed basophilic vacuoles that contain acid phosphatase-positive material within membranes that lack lysosome-associated membrane protein-2. Heart transplantation is the most effective treatment for the otherwise lethal cardiomyopathy. CONCLUSIONS: Danon disease is an X-linked dominant multisystem disorder affecting predominantly cardiac and skeletal muscles.

Myoclonic epilepsy with ragged-red fibers (MERRF) has been associated with an A--G transition at mtDNA nt 8344, within a conserved region of the tRNA(Lys) gene. Although the 8344 mutation is highly prevalent in patients with MERRF, it is not observed in 10%-20% of the cases, suggesting genetic heterogeneity. We have sequenced the tRNA(Lys) gene of five MERRF patients lacking the common 8344 mutation. One of these showed a novel T-->C transition at nucleotide position 8356, disrupting a highly conserved base pair in the T psi C stem. The mutant mtDNA population was essentially homoplasmic in muscle but was heteroplasmic in blood (47%). Neither 20 patients with other mitochondrial diseases nor 25 controls carried this mutation. These findings suggest that tRNA(Lys) alterations may play a specific role in the pathogenesis of MERRF syndrome.