Although light microscopic features of muscle are not pathognomonic in most cases of myasthenia gravis (MG), careful examination of neuromuscular junction by electron microscopy (EM) can reveal important clues for this disease. We report here a case of MG confirmed by EM study to emphasize that tissue diagnosis is still the best adjuvant to confirm the diagnosis. An 18-year-old female visited our hospital complaining of progressive muscle weakness for 3 years. She had difficulty in running, going upstairs and doing routine activities. Symptoms were aggravated with continuous work and resolved after rest. She had weakness of bilateral masseter and facial muscles and proximal portions of extremities without definite diurnal variation. Electromyography showed myopathic changes in proximal muscles of extremities. MG was considered but tensilon test was equivocal. Repetitive nerve stimulation tests revealed 20-30 percent decrease in responses to low and high rate stimulation. Muscle biopsy revealed selective type 2 atrophy. Ultrastructurally, abnormalities of neuromuscular junctions, i.e., wide primary synaptic cleft, and wide and shallow secondary synaptic clefts with mild myopathic features were present. These findings were pathognomonic for MG. Later, her symptoms were improved completely 3 months after thymectomy. The histologic finding of thymus was follicular hyperplasia.
Adolescence ; Biopsy ; Case Report ; Female ; Human ; Microscopy, Electron ; Mitochondria/ultrastructure ; Mitochondria/pathology ; Muscle, Skeletal/ultrastructure ; Muscle, Skeletal/pathology ; Muscle, Skeletal/enzymology ; Myasthenia Gravis/pathology* ; Myofibrils/ultrastructure ; Myofibrils/pathology ; Myosin ATPase/analysis ; Neuromuscular Junction/ultrastructure* ; Neuromuscular Junction/pathology*

Although light microscopic features of muscle are not pathognomonic in most cases of myasthenia gravis (MG), careful examination of neuromuscular junction by electron microscopy (EM) can reveal important clues for this disease. We report here a case of MG confirmed by EM study to emphasize that tissue diagnosis is still the best adjuvant to confirm the diagnosis. An 18-year-old female visited our hospital complaining of progressive muscle weakness for 3 years. She had difficulty in running, going upstairs and doing routine activities. Symptoms were aggravated with continuous work and resolved after rest. She had weakness of bilateral masseter and facial muscles and proximal portions of extremities without definite diurnal variation. Electromyography showed myopathic changes in proximal muscles of extremities. MG was considered but tensilon test was equivocal. Repetitive nerve stimulation tests revealed 20-30 percent decrease in responses to low and high rate stimulation. Muscle biopsy revealed selective type 2 atrophy. Ultrastructurally, abnormalities of neuromuscular junctions, i.e., wide primary synaptic cleft, and wide and shallow secondary synaptic clefts with mild myopathic features were present. These findings were pathognomonic for MG. Later, her symptoms were improved completely 3 months after thymectomy. The histologic finding of thymus was follicular hyperplasia.
Adolescence ; Biopsy ; Case Report ; Female ; Human ; Microscopy, Electron ; Mitochondria/ultrastructure ; Mitochondria/pathology ; Muscle, Skeletal/ultrastructure ; Muscle, Skeletal/pathology ; Muscle, Skeletal/enzymology ; Myasthenia Gravis/pathology* ; Myofibrils/ultrastructure ; Myofibrils/pathology ; Myosin ATPase/analysis ; Neuromuscular Junction/ultrastructure* ; Neuromuscular Junction/pathology*

To verify the postoperative ultrastructural changes of the myotendinous nerve endings of feline extraocular muscles, which are known as proprioceptors. Sixteen recti of four cats were used and divided into three groups. In group A, eight lateral recti were recessed. In group B, four medial recti were resected by 10 mm from insertion to include the myotendinous junction. In group C, four medial recti were resected by 4 mm of muscle bellies only, without disturbing the myotendinous junction. Four weeks after surgery, specimens were examined with electron microscopy. In group A, overall neural structures were well maintained with slight axonal degeneration. In group B, only muscle fibers were observed without any regeneration of neural sprouts. In group C, axonal disintegration and shrinkage were evident. These results indicate that myotendinous nerve endings can be damaged in strabismus surgery, and that resection was more invasive than recession in disrupting myotendinous nerve endings.
Animals ; Cats ; Motor Neurons/ultrastructure ; Nerve Endings/*ultrastructure ; Neuromuscular Junction/*ultrastructure ; Oculomotor Muscles/*innervation/surgery ; Oculomotor Nerve/*ultrastructure ; *Ophthalmologic Surgical Procedures ; Receptors, Sensory/ultrastructure ; Strabismus/surgery ; Tendons/*innervation/ultrastructure

OBJECTIVES: Rodenticide Vacor causes a severe peripheral neuropathy in humans. Electrophysiologic studies on a peripheral motor nerve-skeletal system of Vacor-treated rat showed decreased amplitude of muscle action potential without conduction velocity abnormalities. The ultrastructural studies of the neuromuscular junction were performed to clarify the anatomic site of the Vacor-induced peripheral neuropathy in male Wistar rats. METHODS: After oral administration of a single dose of Vacor, 80 mg/kg of body weight, to the experimental animals, neuromuscular junctions within the interosseous muscles of the hind foot were observed in time. RESULTS: No axon terminal change was noted until 24 hours after the administration of Vacor. Remarkable loss of presynaptic vesicles and swollen endoplasmic reticulum in the axon terminal were developed at 3 days after Vacor treatment. Progressive degenerative changes consisting of marked loss of presynaptic vesicles, focal disruption of membrane in the axon terminal with disappearance of the number of the damaged axon terminal appeared, and flattening of postsynaptic folds was also seen. CONCLUSIONS: These results suggest that degenerative changes in axon terminal at neuromuscular junction may contribute to the peripheral neuropathy developed in the early phase of Vacor poisoning.
Animal ; Diabetic Neuropathies/physiopathology ; Diabetic Neuropathies/pathology* ; Diabetic Neuropathies/chemically induced* ; Human ; Male ; Microscopy, Electron ; Neuromuscular Junction/ultrastructure ; Neuromuscular Junction/physiopathology ; Neuromuscular Junction/drug effects ; Peripheral Nervous System Diseases/physiopathology ; Peripheral Nervous System Diseases/pathology ; Peripheral Nervous System Diseases/chemically induced ; Phenylurea Compounds/toxicity* ; Rats ; Rats, Wistar ; Rodenticides/toxicity*