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Biomedical subjects

O N Markand

Publications and source records attributed to O N Markand.

At least 37 records · Page 2Linked to original sources
PubMed1989

Brain-stem auditory evoked potential abnormalities with unilateral brain-stem lesions demonstrated by magnetic resonance imaging.

We correlated the brain-stem auditory evoked potential (BAEP) abnormalities in 24 patients with discrete unilateral brain-stem lesions demonstrated by magnetic resonance imaging. In 18 patients who had BAEP abnormalities either confined to or more severe on stimulation of one ear, the lesion on magnetic resonance imaging was in the brain stem ipsilateral to the corresponding ear. Mesencephalic lesions produced amplitude abnormalities of the IV/V complex while pontine lesions resulted in abnormalities of earlier components (wave II and/or III). Prolongation of the I-III interpeak latency tended to occur with pontine lesions and of the III-V interpeak latency with mesencephalic lesions. Unilateral brain-stem lesions, particularly at the mesencephalic level, often produced BAEP abnormalities on both ipsilateral and contralateral monaural stimulation.

Adult↗
PubMed1988

HIPDM-SPECT in patients with medically intractable complex partial seizures. Ictal study.

Both interictal and ictal N,N,N'-trimethyl-N'-(2-hydroxy-3-methyl-5-iodobenzyl)-1,3,propanediamine -single photon emission computed tomography (HIPDM-SPECT) were performed in 16 patients with medically intractable complex partial seizures. Ictal HIPDM-SPECT localized epileptic foci in 13 of 14 patients with unilateral temporal focus and provided confirmative evidence of epileptic focus in 11 patients by demonstrating maximally increased regional cerebral perfusion (rCP) in epileptic foci that had shown decreased rCP in a previous interictal study. Ictal HIPDM-SPECT in two patients with bitemporal foci showed more complicated patterns consisting of slightly increased rCP in bilateral multifocal regions. Ictal HIPDM-SPECT was particularly useful for investigating epileptic foci, and correlation with simultaneously recorded ictal electroencephalograms provided further insight for localizing epileptic foci.

Brain↗
PubMed1987

Effects of hypothermia on brainstem auditory evoked potentials in humans.

Ten adult patients who underwent open heart surgery under induced hypothermia had brainstem auditory evoked potentials (BAEPs) recorded at 1 degree- to 2 degrees C-steps as body temperature was lowered from 36 degrees C to 20 degrees C to determine temperature-dependent changes. Hypothermia produced increased latencies of BAEP waves I, III, and V; the prolongation was more severe for the later components with the result that interpeak latencies I-III, III-V, and I-V were also prolonged. The temperature-latency relationship was nonlinear and best expressed by exponential curve. The latencies of waves I, III, V and the interpeak latency I-V increased roughly 7% for each 1 degree C drop; they doubled at a temperature around 26 degrees C. The amplitude of the BAEP components had a quasiparabolic relationship to temperature; the amplitude rose with hypothermia to 28 degrees or 27 degrees C, but decreased linearly with further cooling. All BAEP components were present at temperatures above 23 degrees C and absent below 20 degrees C. With rewarming, the changes reversed and BAEPs returned to initial prehypothermia status.

Acoustic Stimulation↗
PubMed1986

Single photon emission computed tomography (SPECT) brain imaging using N,N,N'-trimethyl-N'-(2 hydroxy-3-methyl-5-123I-iodobenzyl)-1,3-propanediamine 2 HCl (HIPDM): intractable complex partial seizures.

HIPDM-SPECT brain imaging was performed in four patients with intractable complex partial seizures (CPS). Three patients had an epileptogenic focus in one temporal lobe and underwent anterior temporal lobectomy. Interictal HIPDM-SPECT demonstrated decreased regional cerebral perfusion (rCP) in the epileptogenic area in only one patient, but ictal studies showed increased rCP in the epileptic foci of all three patients. In the fourth patient, interictal HIPDM-SPECT showed increased rCP in the area of epileptogenic focus; when antiepileptic medication was taken, rCP decreased. HIPDM-SPECT brain imaging is useful for localizing epileptogenic foci in CPS.

Adolescent↗
PubMed1986

Multiple sclerosis: magnetic resonance imaging, evoked responses, and spinal fluid electrophoresis.

Magnetic resonance images (MRI), evoked responses (ER), and CSF findings were compared in 39 patients with possible, probable, or definite MS. MRI disclosed multiple lesions (72%) more often than ERs (55%) in the total group of patients. In possible MS, MRI showed multiple lesions in 71%, and ER abnormalities were found in 41%. MRI is the preferred test for patients with suspected MS, but ERs are useful when MRI is normal and in the evaluation of optic nerve or spinal cord lesions.

Adult↗
PubMed1985

Postoperative phrenic nerve palsy in patients with open-heart surgery.

We prospectively studied patients undergoing open-heart surgical procedures to evaluate the role of phrenic nerve palsy in the causation of the high incidence of pulmonary complications reported in these patients. Although atelectasis, or infiltrates, or both developed in the left lower lobe of 98% of the patients (43 of 44) with or without similar changes on the right side, only 5 (11%) of the 44 patients had diaphragmatic dysfunction following operation. In 1, the left phrenic nerve became inexcitable; 2 had paresis of the left hemidiaphragm, and 2 had paresis of the right hemidiaphragm. Although damage to the phrenic nerve can occur during open-heart operations, a relatively low incidence of this complication does not support it as the major cause of postoperative pulmonary complications.

Adult↗
PubMed1985

Electrophysiologic evaluation of phrenic nerves in severe respiratory insufficiency requiring mechanical ventilation.

Diaphragmatic paralysis in patients with respiratory insufficiency compounds the problems in the management. In the presence of lower lobe atelectasis, pleural effusion, or a patient's poor respiratory effort, fluoroscopic examination is often not a reliable way to diagnose diaphragmatic paralysis. We observed that transcutaneous phrenic nerve stimulation in the neck and recording the diaphragmatic potentials from electrodes placed on the lower part of the chest is a simple, reliable, and noninvasive technique to diagnose diaphragmatic dysfunction at the bedside in critically ill patients. In 14 postoperative patients and one with cervical spinal cord injury with respiratory failure, we found ten patients who showed phrenic nerve dysfunction. Besides diagnostic utility, the electrophysiologic evaluation of phrenic-diaphragmatic function provides critical information needed for therapy.

Adult↗
PubMed1984

Familial startle disease (hyperexplexia). Electrophysiologic studies.

Six affected members from a family of 15 patients with familial startle disease (hyperexplexia) underwent extensive electrophysiologic evaluation. The most marked abnormality consisted of prominent C response 60 to 75 ms after median and peroneal nerve stimulation. The somatosensory evoked responses were also relatively high in amplitude. These findings suggest that hyperactive long-loop reflexes may constitute the physiologic basis of startle disease.

Electric Stimulation↗
PubMed1984

Monitoring of somatosensory evoked responses during carotid endarterectomy.

During carotid endarterectomy (CEA), we monitored somatosensory evoked responses (SERs) ipsilaterally over the scalp following stimulation of the contralateral median nerve at the wrist. Thirty-eight CEAs in 36 patients were studied. Of the 10 CEAs performed with patients under general anesthesia, three involved marked changes in SERs, reversed by shunt insertion. The remaining 28 CEAs were done with patients under local anesthesia. The SERs remained stable during an average clamp time of 30 minutes in all except one patient, in whom SER changes developed within a minute of clamping; the changes were reversed by shunt placement. Four of the 38 CEAs required a shunt based on SER changes, although measurement of stump pressure (less than 50 mm Hg) would have indicated the necessity of a shunt in eight additional operations. We concluded that SERs are useful in signaling cerebral ischemia and the need for a shunt during CEA.

Aged↗
PubMed1984

Monitoring of multimodality evoked potentials during open heart surgery under hypothermia.

Multimodality evoked responses (ERs) were monitored in 16 adults who had cardiac surgery under cardiopulmonary bypass and moderate hypothermia (19-25 degrees C). Cooling affected all sensory ERs by progressively increasing the latencies of the major components. The effect was more profound on the later than on the earlier ER components. Visual evoked responses (VERs) were most inconsistent and always disappeared at temperatures below 25 degrees C. The later components of the long latency somatosensory evoked responses (SERs) also attenuated or disappeared rather early during hypothermia. On the other hand, short latency SERs were more resistant to the effects of hypothermia. They were always recordable at temperatures of 25 degrees C or above; and usually persisted even at temperatures between 20 and 25 degrees C. Brain-stem auditory evoked responses (BAERs) were consistently present at temperatures above 25 degrees C, wave V was recordable in majority between 20 and 25 degrees C. All sensory ERs disappeared with severe hypothermia (20 degrees C or less) except the components generated more peripherally such as N10 of the short latency SERs. We feel that BAERs and short latency SERs may serve as useful intraoperative monitors of brain function during hypothermia.

Adult↗
PubMed1984

Periodic lateralized EEG abnormality in a case of Neuro-Behcet syndrome.

A thirty-six year old male with a sixteen month history of a progressive neurological disorder had Behcet's disease. His initial electroencephalogram showed periodic lateralizing epileptiform discharges (PLEDs). The electroencephalographic changes in this disorder have not been described in detail in the American literature. The review of world publications in this matter disclosed that there is no specific EEG pattern in this condition, and that electroencephalographic changes are mainly related to the side of the lesion and have no prognostic value.

Adult↗
PubMed1984

Midline spike discharges: clinical and EEG correlates.

Thirty-four tracings in 32 patients had spike discharges recorded at Cz and Pz electrodes. Midline spikes showed strong correlations with clinical seizures; 91% had epileptic seizures of diverse types. Over two-thirds of the patients were neurologically impaired. Midline spikes most probably originate from discharging lesions of the mesial or paramedian region of the cerebral cortex.

Adolescent↗
PubMed1984

Electrophysiologic evaluation of diaphragm by transcutaneous phrenic nerve stimulation.

Phrenic nerve function was evaluated by transcutaneous stimulation in the neck and recording the diaphragmatic potential from surface electrodes placed at the ipsilateral seventh intercostal space (7CS) and the xiphoid process (XP). Simultaneous recordings from 7CS and XP electrodes connected together (XP-7CS) and each connected to a remote reference (knee-7CS and knee-XP) disclosed that the 7CS electrode was always more active and showed electropositive activity, whereas the XP electrode, which was only minimally active, showed electronegative response. Out-of-phase summation of opposite polarity activity at the two electrodes resulted in a higher amplitude response in XP-7CS derivation. Phrenic nerve studies are useful in establishing phrenic nerve injury following cardiothoracic operation. They may also provide evidence of phrenic nerve or diaphragmatic involvement in demyelinative neuropathies, motor neuron disease, and muscular dystrophies.

Adult↗
PubMed1983

Evoked response studies in patients with adrenoleukodystrophy and heterozygous relatives.

Brain-stem auditory evoked responses (BAERs) and somatosensory evoked responses (SERs) were studied in three patients and seven female relatives in three families with adrenoleukodystrophy (ALD). All patients with ALD had abnormal BAERs and SERs, reflecting the central demyelination occurring in ALD. Four of the seven female family members had abnormalities of SERs with or without abnormalities of BAERs, similar to those seen in the patients. We suggest that these abnormalities demonstrate the morphological effects of the ALD gene in the CNS and reflect the physiological alteration in the heterozygous females in families with ALD.

Adolescent↗