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Biomedical subjects

R P Lesser

Publications and source records attributed to R P Lesser.

At least 91 records · Page 5Linked to original sources
PubMed1983

Origin of far-field subcortical evoked potentials to posterior tibial and median nerve stimulation. A comparative study.

Posterior tibial nerve (PTN) evoked potentials (EPs) at the lumbar-low thoracic level have waveforms similar to median nerve (MN) EPs at the cervical level. They consist of a short-duration negativity (N18 and N10, respectively), which reflects the afferent volley before it enters the spinal canal, and a longer-duration, later negativity (N20 and N12, respectively), which consists mainly of slow frequencies and most probably is a postsynaptic dorsal cord potential. At the neck-scalp derivation the MN EP consists of two near-field negativities (N10 and N12) that are recorded from the neck electrode and two far-field positivities (P11 and P13) that are recorded from the scalp electrode. The neck-scalp response to PTN stimulation consists of a near field potential N24 that is followed by a far-field potential P27.

Brain↗
PubMed1983

Ineffectiveness of DMSO in treating experimental brain ischemia.

A beneficial effect of dimethyl sulfoxide (DMSO) in the treatment of acute focal cerebral ischemia has not been proven. In the present study, two established experimental models of acute focal cerebral ischemia were treated with DMSO. Twenty adult cats lightly anesthetized with ketamine hydrochloride underwent right middle cerebral artery (MCA) occlusion for 6 hours. Ten cats were not treated and 10 cats received DMSO (2.5 g/kg i.v.) immediately after occlusion. No improvement of EEG findings, erythrocyte transit, regional cerebral blood flow (rCBF), blood-brain barrier permeability, or morphological findings were demonstrated in the DMSO-treated cats. In a second study, 15 conscious adult baboons underwent temporary left MCA occlusion (6 or 12 hours) using an implanted occluding device. Seven baboons were not treated and 8 baboons received continuous intravenous infusions of DMSO for 10 hours beginning 30 minutes after occlusion. Four of the baboons that were treated with DMSO also were treated with pentobarbital coma for 96 hours starting 4 hours after occlusion. Analysis of the neurological scores after 1 week survival indicated that treatment with DMSO alone and DMSO and pentobarbital coma did not improve the outcome. Morphological changes were similar in the 3 groups. The findings of our investigation indicate that DMSO is ineffective in treating acute focal cerebral ischemia.

Animals↗
PubMed1983

Sensory seizure mimicking a psychogenic seizure.

A patient had episodes of bilateral paresthesias with retained consciousness. The attacks were clinically considered to be psychogenic seizures. Electroencephalography indicated that the attacks were epileptic, perhaps originating from the second sensory area. Electroencephalographic recording of a seizure is essential in differentiating epileptic from psychogenic episodes.

Diagnosis, Differential↗
PubMed1983

Brain stem auditory evoked potentials in posterior circulation surgery.

The objectives of this study were to evaluate the use of brain stem auditory evoked potentials (BAEPs) in 10 adult patients with vascular disorders of the posterior circulation that were treated surgically and to compare the BAEPs with the neurological findings. The vascular lesions included basilar artery stenosis in 3 patients, vertebral artery stenosis in 1 patient, brain stem/cerebellar arteriovenous malformation in 2 patients, and basilar artery aneurysm in 4 patients. Measurement of BAEPs were carried out during operation in all cases. Eight patients had BAEPs measured before operation, and 9 patients had BAEPs measured after operation. Repeat postoperative studies were performed in patients with changes in neurological status. In general, BAEP abnormalities correlated with the neurological findings before and after operation. Six patients had normal intraoperative studies. None of them had clinical findings of pontomesencephalic dysfunction after operation. Three patients with significant BAEP abnormalities during operation had neurological findings of pontomedullary ischemia after operation. Transient BAEP changes in 1 patient were thought to be the result of brain stem retraction. The BAEPs were lost in 3 patients who died. The use of BAEP measurement did not lengthen the operative procedures. However, the technique used in this study required 4 to 8 minutes for the accumulation and interpretation of each average, thereby delaying feedback to the surgeon. The results of this study suggest a potential role for BAEP monitoring in identifying brain stem injury during posterior circulation surgery.

Adult↗
PubMed1983

Cortical somatosensory evoked potentials in response to hand stimulation.

Somatosensory evoked potentials were recorded from chronically implanted subdural electrodes in six patients with intractable seizures. The following conclusions were reached: 1) The initial cortical negativity-positivity (N1 with a latency of about 20 msec and P2 with a latency of about 24 msec) recorded in the postcentral area was an expression of the classical primary surface positivity, but N1 was generated by the posterior pole of an early horizontal dipole in area 3b, and P2 was generated by the positive pole of a slightly delayed vertical dipole in area 1 and 2.2) P2 permitted the most accurate localization of the primary somatosensory area. 3) No potentials were elicited in the primary somatosensory area by stimulation of the ipsilateral hand. 4) No cortical potentials were seen at stimulation intensities below the sensory threshold. The cortical distribution of evoked potentials evoked by weak and strong intensities had significantly different distribution. 5) The recovery function of cortical evoked potentials showed a U-curve with an early period of facilitation (10 to 30 msec) followed by a prolonged period of subnormality which peaked at about 50 msec. The recovery curve at different cortical loci differed.

Cerebral Cortex↗
PubMed1979

Acute generalized polyneuropathy accompanying lithium poisoning.

A woman with typical symptoms of lithium toxicity had, in addition, severe generalized sensorimotor peripheral neuropathy, which cleared completely as the recovered. Electrodiagnostic studies suggested axonal lesions; autopsy ten months later revealed no residual abnormalities. Previous studies have shown that lithium can affect peripheral nerve function, but this is the first reported case of peripheral neuropathy in association with lithium toxicity.

Adolescent↗
PubMed1979

Effect of stimulus intensity on short latency somatosensory evoked potentials.

The peripheral and central potentials evoked by percutaneous electrical stimulation of the median nerve were investigated in a group of neurologically normal subjects. We found: (1) Motor threshold stimulation gave consistently submaximal responses and probably does not represent an optimal intensity for routine use. (2) The sum of motor plus sensory threshold gave potentials which were consistently at, or close to, maximal in amplitude. This intensity was comfortable for all subjects. (3) When stimulating at intensities above motor threshold, the increase in amplitude of peripheral potentials markedly exceeded that of the central potentials. There was evidence suggesting that amplitudes would decline at very high stimulus intensities. (4) The P13 peak latency and the P13--N9 interpeak latency declined and the N17--P13 interpeak latency increased with increasing intensities of stimulation. The N9 and N18 peak latencies remained stable.

Adult↗
PubMed1979

Analysis of the clinical problems in parkinsonism and the complications of long-term levodopa therapy.

We evaluated the current status of 131 patients with idiopathic parkinsonism who were receiving levodopa therapy. The residual parkinsonian symptoms and signs were tabulated, as were the adverse effects from medication. Response to therapy was correlated with duration of the disease and with duration of treatment. Patients with on-off or wearing-off effects were likely to have been treated for 4 years or longer. Patients treated with levodopa for 4 to 8 years were significantly more impaired with parkinsonism than patients treated for 0 to 3 years, even when patients were matched for total duration of disease. These data suggest that the deterioration of responsiveness after several years of levodopa therapy may be due to the therapy itself. Our findings support the concept that utilization of levodopa therapy should be delayed until a patient becomes significantly impaired in occupational or social situations.

Adolescent↗
PubMed1978

Dystonia: a disorder often misdiagnosed as a conversion reaction.

The authors studied the records of 84 patients who had idiopathic torsion dystonia. Thirty-seven cases had originally been misdiagnosed as primarily psychiatric illness. Only 1 patient presented with dystonic movements that were clearly part of a more general psychiatric disorder. The authors believe her to be the first reported patient whose dystonia is undeniably of psychogenic origin.

Adolescent↗