PubMed Health⌕ Search

Biomedical subjects

M R Swenson

Publications and source records attributed to M R Swenson.

8 recordsLinked to original sources
PubMed1992

Phrenic nerve conduction studies.

To refine the technique of phrenic nerve conduction, we first studied electrode positioning and sources of chest wall artifact. Diaphragmatic compound motor action potentials (DCMAPs) were mapped at close intervals over 4 hemithoraces of two subjects, finding optimum recording sites which were then used to quantitate artifacts due to EKG, chest wall EMG, and configurational thoracic changes of respiration. Based on these findings, 20 normal subjects were studied, showing ease of application and good side-to-side agreement for DCMAP latencies; but, in contrast to prior reports, right-to-left correlation for amplitude and waveform was poor, making the unaffected side an unreliable standard in unilateral partial phrenic nerve lesions.

Action Potentials↗
PubMed1992

Effects of magnitude and duration of compression on spinal nerve root conduction.

Spinal nerve root compression occurs commonly in conditions such as herniated nucleus pulposus, spinal stenosis, and trauma. However, the pathophysiology of the symptoms and signs related to spinal nerve root compression is poorly understood. The purpose of the present study was to assess and compare effects of various pressures and durations of acute compression on spinal nerve root conduction in the pig cauda equina. Efferent conduction (compound motor action potentials) and afferent conduction (compound nerve action potentials) were monitored during compression for 2 or 4 hours with compression pressures of 0 (sham), 50, 100, or 200 mm Hg. Recovery from compression was monitored for 1.5 hours. No significant deficits in spinal nerve root conduction were observed with 0 or 50 mm Hg compression, compared to significant conduction deficits induced by 100 and 200 mm Hg compression. Three-way analysis of variance demonstrated significant effects of compression pressure and duration on conduction at the end of compression and recovery, with a significant difference between efferent and afferent conduction at the end of the recovery period. These observations suggest an interaction between biomechanical and microvascular mechanisms in the production of nerve root conduction deficits. Such information may relate to the motor and sensory dysfunction in clinical conditions associated with spinal nerve root compression.

Action Potentials↗
PubMed1991

Neurophysiologic studies of the peripheral nervous system in nephropathic cystinosis.

Cystinosis is an autosomal recessive metabolic disorder in which nonprotein cystine accumulates within most body tissues due to a defect in lysosomal cystine transport. Neurologic declarations are only recently being recognized. We studied 13 cystinotic subjects (aged 5 to 21 years old), determining median motor and sensory nerve conduction velocities, F waves, peroneal motor nerve conduction velocities, sural sensory nerve conduction velocities, median sympathetic skin response, electrocardiogram R-to-R variability, and blink reflex analysis. The results were normal. We conclude that neurophysiologic testing suggests relative sparing of the peripheral nervous system in nephropathic cystinosis.

Adolescent↗
PubMed1991

Effects of acute, graded compression on spinal nerve root function and structure. An experimental study of the pig cauda equina.

A well-controlled experimental model for analysis of compression-induced functional changes of the porcine cauda equina is presented. The model allows for electrophysiologic investigation of a variety of neurophysiologic changes induced by nerve root deformation. At an acute pressure threshold of 50-75 mm Hg, changes in both afferent and efferent conduction are induced. With higher compression pressure, a differential recovery in afferent and efferent conduction is seen.

Action Potentials↗
PubMed1991

Eales' disease with central nervous system infarction.

Eales' disease is a noninflammatory occlusive disorder of the retinal vasculature that causes recurrent hemorrhages into the retina and vitreous and ischemic changes in the eye. Extraocular manifestations of Eales' disease are rare and limited to the central nervous system. We report the case of a patient with Eales' disease and ischemic stroke, and we review the neurologic manifestations of this primarily ophthalmologic vasculopathy.

Cerebral Infarction↗
PubMed1990

Photic sneeze reflex in nephropathic cystinosis.

Photic induced sneeze is a reflex that occurs in certain individuals after exposure to bright light. Cystinosis is an autosomal recessive inborn error of metabolism in which nonprotein cystine accumulates within lysosomes. The pathognomonic ocular manifestation of cystinosis is corneal crystal deposition. We observed photic induced sneezes during ophthalmoscopic examination in five of 19 patients with nephropathic cystinosis (26%). We report on this observation and discuss possible pathophysiological mechanisms for photic induced sneezing in cystinosis.

Cystinosis↗
PubMedDate not supplied

Preservation of evoked potentials in a case of anterior spinal artery syndrome.

A case of anterior spinal artery syndrome is presented for which there are neurologic, electrophysiologic, and pathologic correlations. Ten days prior to her death, a 52-year-old hypertensive female developed severe chest pain and lower extremity weakness. A diagnosis of aortic dissection resulting in an anterior spinal artery syndrome was made. Intraoperative posterior tibial somatosensory evoked potentials demonstrated normal morphology and latencies. Autopsy revealed an infarction of the anterior portion of the thoraco-lumbar spinal cord with preservation of the posterior columns. This case demonstrates that severe spinal cord injury can exist in the presence of preserved somatosensory evoked potentials.

Aortic Dissection↗