Clinical problem-solving: trapped by an incidental finding.
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Diagnosis↗
Biomedical subjects
L H Phillips
Publications and source records attributed to L H Phillips.
The epidemiology of myasthenia gravis in central and western Virginia.
We conducted a study of the epidemiology of myasthenia gravis (MG) in four locations in central and western Virginia from 1970 through 1984. The population surveyed was 555,851 in 1984. A total of 73 new cases of MG occurred during the survey period, producing an overall average annual incidence rate of 9.1 per million. The point prevalence rate in 1980 was 13.4 per 100,000, and in 1984 it was 14.2. Approximately 15% of the population was black, and we found that incidence and prevalence rates for the black population were higher than the corresponding white population. When the population was subdivided into <50 and 50+ age groups, the incidence and prevalence were significantly higher in the older group. The rates we report here are higher than rates reported from any other locality. The reasons for the higher rates include optimal case identification, survey of a population with a higher incidence, and increasing aging of the population.
Adult↗
Trends in the association of Lambert-Eaton myasthenic syndrome with carcinoma.
The Lambert-Eaton myasthenic syndrome (LEMS) is often associated with carcinoma. The exact number of patients with tumor has been reported to be as high as 70%. Recent clinical experience suggests that the actual number of patients with tumor may be substantially lower. We combined data from the clinical experience of the neuromuscular services at West Virginia University and the University of Virginia to determine the rate of occurrence of cancer in this disorder. We identified 28 patients with LEMS, and 14 had cancer. There is a distinct trend for a lower tumor frequency over the past decade, which suggests that the clinical manifestations of the disease may be changing.
Adult↗
Surgeon's foot: a report of sural nerve palsy.
Although compression neuropathies are encountered frequently in neurosurgical practice, involvement of the sural nerve is described rarely. We report a case of bilateral compression neuropathy of the sural nerve with an unusual mechanism of injury. The case is discussed, and the pertinent literature is reviewed.
Follow-Up Studies↗
Electrophysiological findings in localized hypertrophic mononeuropathy.
Localized hypertrophic mononeuropathy (LHM) is a rare foccal neuropathy associated with perineurial cell proliferation due to an undefined stimulus. We report a case of LHM involving the proximal ulnar nerve in a 13-year-old boy. Serial clinical and electrophysiological observations were done, including intraoperative recordings directly from the nerve on two occasions. The evolution of abnormalities, as documented by electrophysiological and immunohistochemical studies, is compatible with a process of progressive thinning of myelin sheaths, culminating in axonal degeneration in later stages. Intraoperative recording of nerve action potentials was used to guide surgical management of the lesion. Ultimately, there was a good clinical and electrophysiological response to resection of the lesion and sural nerve fascicular grafting.
Action Potentials↗
Electrophysiologic mapping of the segmental anatomy of the muscles of the lower extremity.
Our knowledge of the specific root innervation of skeletal muscles is derived from accumulated clinical experience. While performing selective posterior rhizotomy for treatment of spasticity in children with cerebral palsy, we made direct electrophysiologic measurement of the root innervation of the lower extremity. We stimulated ventral roots from L2 to S2 while recording from all muscles simultaneously. The size of the evoked compound muscle action potential was used as an indication of the amount of innervation derived from stimulation of a given spinal root. We found the major root innervation for the 8 muscles studied to be: adductor longus, vastus medialis, and vastus lateralis, L3; tibialis anterior; L4; peroneus longus, L5; and medial gastrocnemius, lateral gastrocnemius, and gluteus maximus, S1. In general, each muscle received innervation from 3 or more roots. Prefixed or postfixed innervation patterns were found in 27.9% of legs examined, and there was asymmetry of innervation in 29.8%. We conclude that the segmental innervation of lower extremity muscles is broader than previously thought. Anomalous innervation occurs so frequently that caution should be used in attributing any pattern of clinical or EMG findings to a specific spinal level.
Cerebral Palsy↗
Myotonia congenita.
There are two types of MC, autosomal dominant and autosomal recessive (also called recessive generalized myotonia), both with the predominant clinical feature of diffuse myotonia. Recessive MC patients have more weakness than patients with dominant MC. MC patients of both types have a normal life span. Ongoing genetic studies have not as yet identified any chromosomal linkage. Electrophysiologically and pathophysiologically, there is no difference between these two types. The major pathophysiologic abnormality is decreased membrane chloride conductance. Treatment of myotonia is not always necessary, but when it is, the most effective medications are those that stabilize the muscle membrane. Phenytoin is frequently the first choice because it has more benign side effect profile than other drugs and a reasonable response rate.
Diagnosis, Differential↗
Autoantibodies to GABAergic neurons and response to plasmapheresis in stiff-man syndrome.
Stiff-man syndrome is a rare disorder of unknown etiology in which progressive rigidity, spasms, and continuous motor unit activity may be due to dysfunction of GABAergic inhibition of alpha motor neurons. Some patients with this disorder have evidence of autoantibodies reactive with glutamic acid decarboxylase (GAD). We describe a patient with progressive stiff-man syndrome and high titers of GAD-like immunoreactivity in serum but not spinal fluid. Plasmapheresis resulted in lowered antibody titers, decreased exteroceptive reflex responses, reduced motor unit activity, and marked clinical improvement. Immunohistochemistry using patient serum and plasma produced specific labeling of human and experimental animal tissue consistent with GABAergic neurons and terminal fields. This antibody response was not present in samples from more than 200 other patients. These results provide additional evidence of an autoimmune mechanism for stiff-man syndrome and indicate plasmapheresis may be beneficial in some patients.
Adult↗
Somato-somatic referred pain caused by suprasegmental spinal cord tumor.
Tactile stimulation of a coin-sized area in a T-2 dermatome consistently triggered a lancinating pain in the ipsilateral C-8 dermatome in a 38-year-old woman. The SEP and an MRI led to a diagnosis of a tumor at the left cervico-medullary junction, much higher than the clinically suspected level. Surgical exploration revealed an exophytic glioma, and the pain was abolished postoperatively. Ephaptic transmission at the tumor site was suspected as a pathophysiologic mechanism.
Adult↗
Electrophysiological monitoring during lipomyelomeningocele resection.
Surgical resection of a lipomyelomeningocele carries a risk of injury to nerve roots in the cauda equina. We have devised a technique for combined spinal evoked potential and peripheral nerve compound action potential recording for intraoperative monitoring of this surgical procedure. We report the results of six cases where this technique was used. In each case, the monitoring prevented resection of viable neural tissue, and all six patients were neurologically unchanged postoperatively.
Action Potentials↗
Diagnosis of myasthenia gravis in the 1990s.
We have tried to show through this analysis how an understanding of the characteristics of diagnostic tests can lead one to a rational strategy for making clinical decisions. The diagnosis of MG can be made with a high degree of confidence in most situations, but the amount of supporting test information necessary depends on the clinical situation. This analysis does show some general guiding principles. The first is that the results of the edrophonium test should be used to guide further diagnostic assessment in most situations. In the small number of cases in which an objective edrophonium test cannot be done, the pretesting estimate of certainty should be used to guide testing strategy. A second principle is that, if a second diagnostic test is required after edrophonium testing, it should be the acetylcholine receptor antibody assay. This test is less expensive and it has more overall reliability. EMG testing thus serves as a third-line test for MG, and it can be reserved for a small number of clinical situations in which certainty about the diagnostic test is too high to reject the possibility of MG, yet too low to initiate treatment confidently. The greatest attractiveness of this type of analysis is that one may take issue with one or more of the assumptions on which it is based without invalidating the conclusions. The conclusions can be tested by a process called sensitivity analysis, in which one or more of the variables can be changed to study its effect on the outcome of the analysis. For example, one could require that certainty exceed 99% (T1) prior to beginning treatment.(ABSTRACT TRUNCATED AT 250 WORDS)
Edrophonium↗
Neurophysiologic monitoring during surgery of peripheral and cranial nerves, and in selective dorsal rhizotomy.
Physiologic monitoring may warn of impending neural damage and intraoperative assessment may provide critical information used to direct the surgical procedure itself. Intraoperative techniques utilize methods modified from the diagnostic neurophysiologic laboratory. Simultaneous multimodality recording of different signal sources is of particular value for several types of procedures. Intraoperative studies must be tailored to each patient's clinical condition and to the specific surgical risks. Since studies have supported the benefits of intraoperative monitoring for peripheral nerve and cranial nerve surgery, monitoring is not likely to be subjected to the rigors of a randomized controlled study for these procedures.
Action Potentials↗
All that quakes does not necessarily shiver.
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Anesthesia Recovery Period↗
Sarcoidosis and the nervous system.
Neurologic involvement occurs in 5 per cent of patients with sarcoidosis and is a presenting symptom in about half of those affected. The neurologic symptoms are due to a granulomatous process that mirrors that seen in the systemic form. Its diagnosis is usually established by the demonstration of sarcoidosis in other systems and supported by clinical, radiographic, and laboratory evidence. Any and all portions of the nervous system can be involved in either an acute or a chronic fashion. Early acute presentations tend to have excellent outcomes and the overall prognosis for the disease is good. The cranial nerves, especially the facial nerve, are most frequently involved and have a good prognosis. CNS involvement, usually in the form of a meningoencephalitis involving the hypothalamic region, is usually chronic and associated with poor prognosis. Peripheral nerve and muscle involvement is frequently asymptomatic. Although neuropathy or myopathy may present acutely, the usual presentation is subacute or chronic. There have been no controlled studies of therapy in neurosarcoidosis. Early implementation of corticosteroids remains the mainstay of treatment. Evidence for improvement with treatment is anecdotally reported in many cases, but progression of the disease also occurs despite therapy.
Humans↗
Lambert-Eaton myasthenic syndrome: the lack of short-term in vitro effects of serum factors on neuromuscular transmission.
Serum was obtained from 7 patients with the Lambert-Eaton myasthenic syndrome (LES), 3 patients with small-cell carcinoma of the lung (SCCL), and 9 healthy control subjects. Serum samples were applied in vitro to the rat neuromuscular junction (for 1-3 h for control LES sera; 4 h for SCCL sera), following which the pre- and postjunctional physiological effects of serum factors were studied in the presence of 10 mM [Mg2+]o. All sera produced a marked reduction in the frequency of spontaneous miniature end-plate potentials (MEPPs), while causing slight to moderate changes in MEPP amplitude. There were no consistent changes in the quantum content of the impulse-evoked end-plate potentials, though the serum from one LES patient significantly and reversibly inhibited the evoked quantal release. No significant effect was found when a human intercostal muscle was exposed to serum from another LES patient for 2 h. Therefore, when applied in vitro on a short-term basis, the putative LES autoantibodies do not consistently react with voltage-dependent calcium channels in the motor nerve terminal and thus fail to reproduce the physiologic abnormality of the syndrome. We suggest that the pathogenic IgG molecules may require more than 3h of incubation in order to gain access to, and inhibit the function of, the prejunctional Ca2+ channels.
Action Potentials↗
Familial long thoracic nerve palsy: a manifestation of brachial plexus neuropathy.
Long thoracic nerve palsy causes weakness of the serratus anterior muscle and winging of the scapula. It is usually traumatic in origin. Isolated long thoracic nerve palsy has not been recognized as the major manifestation of familial brachial plexus neuropathy, but I have studied the syndrome in four members of three generations of one family. One individual suffered an episode of facial paresis. The inheritance pattern was autosomal dominant.
Adolescent↗
The declining incidence of stroke.
A major decline in the incidence of stroke occurred in the population of Rochester, Minnesota, during the period 1945 to 1974. For every 100 first episodes of stroke that occurred per unit of population during the period 1945--49, only 55 occurred in the period 1970--74. Although the decline was present in both sexes and in all age groups, the reduction in rates was more pronounced in the elderly. There was no major change in age at onset. Analysis of cohorts born during successive five-year periods from 1865 to 1915 confirmed the decreasing incidence rate in all age groups.
Age Factors↗
Sudden death from stroke.
Sudden death is defined as any death that occurs less than 24 hours after the onset of first symptoms. Strokes account for 10 to 20% of all sudden deaths. The records of all residents of Rochester, Minn., who had their first stroke during the period 1955 through 1969 were analyzed. Among 255 deaths caused by the first stroke, 52 were sudden. Twenty-six of the deaths were due to primary intracerebral hemorrhage, and 20 to primary subarachnoid hemorrhage. Only two of the sudden deaths were caused by infarction: one by pontine and cerebellar infarct and the second by a cortical infarct, which resulted in death from status epilepticus. Among the nine patients who died within 2 hours of the onset of symptoms, six had primary subarachnoid hemorrhage. Hypertension was noted in 23 of the 26 patients (88%) who died of primary intracerebral hemorrhage; 8 patients with primary intracerebral hemorrhage were on long-term oral anticoagulant therapy, and all 8 were hypertensive.
Adult↗