Biomedical subjects
S J Purves
Publications and source records attributed to S J Purves.
MRI in the diagnosis of MS: a prospective study with comparison of clinical evaluation, evoked potentials, oligoclonal banding, and CT.
We compared the diagnostic capabilities of MRI to CT, evoked potentials (EP), and CSF oligoclonal banding analysis in a prospective evaluation of 200 patients with suspected multiple sclerosis (MS). MRI was the best method for demonstrating dissemination in space. An abnormal appropriate EP in monosymptomatic disease was usually supported by MRI and CSF analysis as being predictive of MS as a clinical diagnosis. A normal appropriate EP study was not satisfactory because MRI and CSF analysis often did not support a diagnosis of non-MS. When there is agreement between three of these paraclinical studies, the diagnosis of MS is probably unequivocal. For use in research studies, laboratory-supported definite MS (LSDMS) could be diagnosed in 85 patients of the total 200 (42.5%), in 19/38 (50%) of optic neuritis (ON) patients, and in 24/52 (46%) of chronic progressive myelopathy (CPM) patients. MRI was 100% successful in identifying patients who qualified for LSDMS in the ON and CPM groups. In a short follow-up (less than 1 year), 19/200 (10%) went on to develop clinically definite MS (CDMS), and MRI predicted that diagnosis in 18/19 (95%). Only long-term follow-up will show how well these studies and the category of LSDMS predict the development of CDMS. The clinical diagnosis of MS (CDMS), even though only 95% accurate, must remain the gold standard.
Results of anterior corpus callosum section in 24 patients with medically intractable seizures.
Twenty-four medically refractory seizure patients, who did not qualify for excisional surgery, had anterior two-thirds corpus callosum section. Three to 11 years' postoperative follow-up suggests that this procedure can (1) lateralize a frontal lobe focus, which may lead to subsequent localized excision and (2) significantly reduce seizure frequency and severity in 75% of the patients without giving any permanent neurologic deficits. Patients with an ictal focus confined to one frontal lobe did best (8/8 improved), followed by patients with secondarily generalized seizures and multifocal bilateral foci (5/6 improved). Patients with mental retardation benefited less frequently (5/10 improved), but 4/4 from this group with ictal falls associated with Lennox-Gastaut syndrome did benefit. In this series, the improvements following the anterior partial section were lasting if present at 1 year of follow-up. Anterior corpus callosum section should be considered as a diagnostic (lateralizing) and therapeutic option in appropriately defined medically refractory patients who do not qualify for excisional surgery.
An epileptic syndrome caused by mesial frontal lobe seizure foci.
We describe an epileptic syndrome of bilaterally coordinated limb movements, axial movements, vocalization, and nonmasticatory oral activity. EEG and physiologic evidence indicates the syndrome is caused by ictal discharge in the mesial frontal lobes. Two of 12 patients were not helped by anterior temporal lobectomy, and 3 others improved after section of the anterior two-thirds of the corpus callosum.
Cerebral evoked potentials: a historical review of the marseilles contributions and a preliminary report on a study of the effects of various stimulus parameters on the P90 component of the pattern visual evoked potential.
A preliminary report is given of a study in 10 normal subjects comparing the laterality of the P90 component of the PVEP as elicited by pattern reversal and pattern appearance stimuli delivered monocularly and binocularly in the central and peripheral portions of one-life field. P90 was shown often to appear maximally over the hemisphere ipsilateral to the stimulus field with pattern reversal stimuli in central targets viewed monocularly. Pattern appearance, peripheral targets and binocular stimulation provoked less consistently lateralized and sometimes differently configured responses. It is concluded that while all combinations provoked responses consistent with a dipole generator model similar to that proposed by Blumhardt et al. (1978), these different modes of stimulation cannot be considered to be equivalent.
Identifying academic aptitude in adolescent children by psychological testing and EEG spectral analysis.
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A comparison of visual, brainstem auditory, and somatosensory evoked potentials in multiple sclerosis.
Multimodality evoked potentials testing including PVEPs, SEPs and BAEPs was done in 112 patients who were known or suspected to have multiple sclerosis. The incidence of abnormal evoked potential findings in each of these systems was considered in patients in the different diagnostic categories of M.S. Results were also evaluated with respect to the presence of abnormal clinical visual, somatosensory, or brainstem signs. The PVEP was found to be the most frequently abnormal in even patients without clinical involvement in the visual system (45% of patients with definite, probable, or possible M.S.), the SEP was less frequently abnormal in the absence of clinical signs (35% in patients with M.S.), and the BAEP showed the lowest frequency of abnormalities in patients without brainstem signs (14% in patients with M.S.). Combining the three types of evoked potentials significantly increased the percentage of M.S. patients having abnormal findings, compared to any of these tests alone, with 97% of "definite" M.S. patients, 86% of "probable" M.S. patients and 63% of "possible" M.S. patients having at least one of these EP tests abnormal.
Effects of stimulus shape on visual evoked potentials.
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Proceedings: Visual evoked responses (VERs) to geometric shapes.
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