Faculty Bibliography

A number of myopathies whose common denominator is abnormal foci of desmin positivity have been described under the rubrics of spheroid body myopathy, cytoplasmic body myopathy, Mallory body myopathy, myopathy with granulofilamentous inclusions, desmin storage myopathy, and intermediate filament myopathy. In this study we reevaluate the light microscopic and ultrastructural features of the myopathy with abnormal foci of desmin positivity. In 10 cases of the disease, ultrastructural analysis reveals 2 major types of lesions: (a) foci of myofibrillar destruction and (b) hyaline structures that appear as spheroidal bodies on electron microscopy. The foci of myofibrillar destruction consist of fiber areas containing disrupted myofilaments, Z-disk-derived bodies, dappled dense structures of Z-disk origin, and streaming Z-disks that are sometimes adjacent to lakes of dense material. The spheroid bodies are composed of compacted and degraded myofibrillar elements. Membrane-bound vacuoles harboring degenerating membranous organelles are a less frequent and probably secondary abnormality. None of the lesions in muscle comprise 8 to 10 nm intermediate filaments. The findings imply that spheroid body myopathy, cytoplasmic body myopathy, Mallory body myopathy, and myopathy with granulofilamentous inclusions are consequences of a single or closely related pathologic processes. Because the common denominator appears to be focal dissolution of the myofibrils followed by accumulation of the products of the degradative process, we propose the term myofibrillar myopathy to cover the observed spectrum of pathologic changes.

Intracellular ionized Ca2+ concentration was measured in clonal mouse anterior pituitary tumor cells with the fluorescent Ca2+ indicator Quin-2. In control physiological solution, free cytoplasmic Ca2+ concentration was found to be 139 +/- 11 nM. Replacement of 50 mM NaCl by 50 mM KCl in the extracellular fluid caused a 29 mV depolarization and a 4.2-fold increase in the concentration of free cytoplasmic Ca2+. Under comparable depolarizing conditions, a specific influx of 2.66 nmole of 45Ca2+ per mg protein was detected 1 min after addition of high K+, accompanied by a marked increase in the initial rate of beta-endorphin secretion. In the absence of external Ca2+, depolarization by K+ produced little or no increase in either intracellular free Ca2+ or hormone release. Incubation of AtT-20/D16-16 cells in the secretagogue norepinephrine led to a depolarization accompanied by an increase in spontaneous action potential frequency and a marked elevation in cytosolic Ca2+ concentration. Exposure of cells to somatostatin, an inhibitor of hormone release, led to only transient decreases in burst frequency and no significant reduction in intracellular Ca2+ levels. These results indicate that in addition to intracellular Ca2+, other factors also control secretory activity in AtT-20/D16-16 anterior pituitary cells.

Left spinal accessory nerve palsy occurred in a young man when he quickly turned his head to the right while his shoulders were pulled down by heavy hand-held objects. Electrophysiologic studies demonstrated partial axonotmesis of the spinal accessory nerve branches innervating the sternocleidomastoid and upper and middle trapezius and complete axonotmesis of spinal accessory branches to the lower trapezius. There was a separate, although functionally minor, cervical plexus innervation of the lower trapezius.

Motor axons supplying lumbrical muscles are less severely affected than axons supplying thenar muscles in the carpal tunnel syndrome; sometimes lumbrical motor fibers are less affected than digit 2 sensory fibers. This pattern is consistent with compression of both the anterior and posterior aspects of the median nerve in the carpal tunnel because nerve fibers responsible for thenar, lumbrical, and digit 2 functions lie in an anterior-posterior gradient within the distal median nerve. Recognition of lumbrical sparing supports the electrodiagnosis of carpal tunnel syndrome when the distal latency to thenar muscles or the palm-to-wrist mixed median nerve conduction velocity is normal.

Cervical root stimulation (CRS) was compared with conventional EMG, nerve conduction, and late response studies in 34 patients with possible cervical radiculopathy. Cervical roots were stimulated by monopolar needles inserted into paraspinal muscles, recording compound muscle action potentials in biceps, triceps, and abductor digiti minimi muscles. In 18 patients with clinical evidence of radiculopathy, EMG was abnormal in 11 (61%), but CRS was abnormal in all 18. Of 16 patients with symptoms but no signs of radiculopathy, EMG was abnormal in 5 (31%) and CRS was abnormal in 9 (56%).

In median nerve lesions of the hand, electrophysiologic evaluation of the second lumbrical muscle can help to differentiate between lesions of the common digital nerves and the proper digital nerves, as illustrated by this case report. Median nerve conduction studies to the second lumbrical muscle can be performed by placing an active recording electrode just radial to the midpoint of the third metacarpal and stimulating the median nerve at the wrist or elbow.

Six patients with periodic leg movements of sleep (PLMS) were studied electrophysiologically. All patients had normal results on routine nerve conduction studies and electromyography. In 5 patients the blink reflex consisted of three components, and in 1 patient it consisted of four components, with two components being normal. The second component of their blink reflex did not habituate. Other abnormalities included long-latency responses in the extremities in 2 patients, release of H-reflexes from flexor hallucis brevis muscle in 2 patients, and an Hmax/Mmax ratio of 98% in 2 patients. One patient's median nerve somatosensory-evoked response had a markedly enlarged P22 wave. These electrophysiological abnormalities suggest a disorder of the central nervous system producing increased excitability of segmental reflexes. To produce increased excitability of both brainstem and spinal cord reflexes, the disorder must be operative at the pontine level or rostral to it. Since long-latency components of blink reflexes occurred in all our patients, this may be a helpful diagnostic test when PLMS is suspected.

A patient with a discrete metastasis in the ventral hypothalamus and optic chiasm is reported, who developed an abnormal daily rhythm of oral temperature without alteration of the 24-h mean temperature. This region, its afferents, and its efferents appear to be important in the neural regulation of human circadian rhythmicity.

A woman with syringobulbia and syringomyelia and her sister with syringomyelia are described. The diagnosis was confirmed radiologically and surgically in the first sister and no other definite abnormalities of her craniocervical junction were found.

We studied a patient with multiple myeloma who had immunologically identified myeloma light chain proteins within neurons projecting beyond the blood-brain barrier, but not within intrinsic neurons of the spinal cord, brain stem, and cerebral cortex. There was a possibility that these myeloma light chain proteins or their immunologically recognizable fragments were transported intra-axonally by human peripheral nerves. Myeloma light chain proteins were also identified within cerebellar Purkinje's neurons. This labeling may have been secondary to transport from cerebrospinal fluid.