Short-latency somatosensory evoked potentials in brain death

Summary Simultaneous recording of somatosensory evoked potentials to median nerve stimulation above the upper and lower neck in brain-dead patients revealed that all cervical responses were preserved in 10%, whereas a marked reduction in amplitude or even loss of N 13b at the level of the C2 spinous process was observed in 90%. Of the patients, 55% revealed an additional loss of N 13a, recorded at the level of the C7 spinous process; in 15% all cortical and spinal evoked potentials were missing, but Erb's point waves were still normal. These results suggest two different origins of the main negative waves (N 13a and N 13b), recorded above the upper and lower cervical spinal cord. N 13a (C7) is supposed to arise in the dorsal horn at the C6/7 level, N 13b (C2) in the cervicomedullary junction.     

Short-latency somatosensory evoked potentials in brain-dead patients

Ten adult brain-dead patients were evaluated for the presence of clearly defined median nerve short-latency somatosensory evoked potentials (SSEPs). All met clinical criteria recommended by the President's Commission report (1981), had positive apnea tests, and had electrocerebral silent EEGs. P13-P14 and N20 were absent in all scalp-scalp channels, although 3 patients showed P13-P14 in scalp-non-cephalic channels. Of 6 patients showing N13, 3 lacked P13-P14. Our data suggest a characteristic destruction of N20 and rostral P13-P14 generators, with variable rostral-caudal loss of lower generators. SSEPs can provide valuable information about brain-stem activity in the evaluation of suspected brain-dead patients.     

Short-latency somatosensory evoked potentials in perinatal asphyxia

Ten asphyxiated term newborns were studied in the first 6 months of life with median nerve short-latency somatosensory evoked potentials (SLSEP) and followed subsequently to a mean age of 20 months. Results of SLSEP correlated with subsequent outcome in every patient; normal and abnormal infants at subsequent examination were separable on the basis of prior SLSEP, although the severity of later disability could not be inferred from SLSEP.     

Short-latency somatosensory evoked potentials in myotonic dystrophy: evidence for a conduction disturbance

Short-latency somatosensory evoked potentials were recorded in 13 patients with myotonic dystrophy (MyD). The MyD were compared with age-matched controls. The mean conduction latency between the brachial plexus and dorsal column nuclei (EP-N14) was significantly longer for the MyD. Results suggest an afferent conduction disturbance in MyD.     

Short-latency somatosensory evoked potentials in dystrophia myotonica.

Somatosensory evoked potentials (SEPs) were recorded in a group of 21 patients with dystrophia myotonica and in a group of controls. Those with dystrophia myotonica had longer absolute peak latencies due to slower peripheral conduction. SEP abnormalities revealed peripheral and/or central conduction delays in 33% of the dystrophia myotonica subjects. There was no apparent relationship between the clinical severity of the disease and SEP abnormality.     

Short-latency somatosensory evoked potentials in the management of patients with achondroplasia

Twenty-three patients with achondroplasia were evaluated using short-latency somatosensory evoked potentials (SEPs) of median and peroneal nerves. Abnormal studies were found in 61%. All patients with neurologic signs or symptoms had abnormal SEPs, with good correlation between SEP results and the level of the lesion determined clinically and radiographically. SEPs were abnormal in 44% of neurologically intact achondroplasts, several of whom had CTs confirming significant foramen magnum stenosis. SEPs are an important noninvasive means of evaluating patients with achondroplasia and are particularly valuable in children to document neurologic compromise before significant and perhaps irreversible clinical impairment develops.     

Short-latency somatosensory evoked potentials in degenerative and vascular dementia.

Short-latency somatosensory evoked potentials (SEPs) were recorded from 54 patients with dementia as compared to 32 age-matched controls. SEPs were generally normal in patients with senile dementia of Alzheimer type, while patients with multi-infarct dementia showed a prolonged central conduction time, an increased latency of both N13 and N20 and a reduction of the primary cortical response amplitude. These findings suggest that recording SEPs may be useful in the differential diagnosis between degenerative dementia and multi-infarct dementia.     

Short-latency somatosensory evoked potentials following median nerve stimulation in Down's syndrome

Short-latency somatosensory evoked potentials (SEPs) following median nerve stimulation were recorded in 42 patients with Down's syndrome and in 42 age- and sex-matched normal subjects. There were no significant differences between the 2 groups in the absolute peak latencies of N9, N11 and N13 components. However, interpeak latencies, N9-N11, N11-N13 and N9-N13, were prolonged significantly in Down's syndrome. These findings suggest impaired impulse conduction in the proximal part of the brachial plexus, posterior roots and/or posterior column-medial lemniscal pathway. Interpeak latency N13-N20, representing conduction time from cervical cord to sensory cortex, was not significantly different between the 2 groups. Cortical potentials N20 and P25 in the parietal area and P20 and N25 in the frontal area were of significantly larger amplitude in Down's syndrome. P25 had double peaks in 16 of 42 normal subjects, but these were not apparent in any of the patients.     

Short-latency somatosensory and brainstem auditory evoked potentials in patients with Parkinson's disease

Short-latency somatosensory evoked potentials (SSEPs) and brainstem auditory evoked potentials (BAEPs) were recorded in 44 patients with Parkinson's disease (mean age 67.3 years) and 23 normal subjects (mean age 69.3 years). Patients with Parkinson's disease and normal subjects did not show any significant difference with regard to the interpeak latencies between N13 and N20 central conduction time (CCTs). Likewise, there were no significant differences in CCTs between patients with and without dementia. The interpeak latencies between waves I and V (I-V IPLs) in patients with Parkinson's disease were significantly longer than those of the normal subjects (p less than 0.05). In particular, patients with dementia revealed significant prolongation of I-V IPLs compared to patients without dementia and normal subjects (p less than 0.01, p less than 0.001) although no significant differences were observed between patients without dementia and normal subjects. These results show that auditory brainstem pathways are involved in Parkinson's disease patients with dementia.     

Short-latency somatosensory evoked potentials and magnetic resonance imaging in the medial medullary syndrome

A 57-year-old woman was admitted to Kakeyu Hospital complaining of paresis of the left upper and lower extremities which suddenly developed three years ago. Neurological examination revealed spastic paresis of the left upper and lower limbs without facial and lingual paresis. The reflexes were abnormally brisk on both sides but they were more remarkable on the left side, which also showed Babinski's sign. Sensitivity to light touch and vibration was moderately decreased and sensitivity to pinprick and joint position was minimally decreased in the left upper and lower extremities. No cerebellar sign was observed. Needle EMG disclosed large motor units with an amplitude of 4-5 mV and a duration of 8 msec in the light half of the tongue during weak contraction. MRI using a 0.5-T superconducting magnetic resonance unit detected a small, wedge-shaped infarction in the anterior medial portion of the medulla just below the pontomedullary junction. Somatosensory evoked potentials (SEPs) after median nerve stimulation with a non-cephalic reference were recorded. After stimulation of the left side, the scalp-recorded P13 was recognized at the normal latency, but the later components, N16 and N18, were apparently absent. On the other hand, SEPs in another case with thalamic hemorrhage revealed normal N16 potential with absence of N18 on the affected side. From these SEP findings and the reports on SEPs in lesions of the brain stem or thalamus, it was suggested that P13 is abnormal in lower medullary lesions and is preserved in upper medullary lesions, and that N16 is abnormal in brain stem lesions and is preserved or changed a little in thalamic lesions.     

Short latency somatosensory evoked potentials in children with autism

SSEP were recorded in normal volunteer, autism, MBD and MR groups in order to find electrophysiological evidence of a brain lesion. Peak latencies per 1 m body length, P1/H, P2/H and P3/H in MR, and P3/H in autism, were greater than those in normal controls. The values of interpeak latencies per 1 m body length, P1-P3/H and P2-P3/H in autism and MR, were greater than those in normal controls. These in MBD were not different from in normal controls. The cause of the increase in P1/H in MR is unknown. The increases in P1-P3/H and P2-P3/H suggest that in autism and MR there is brainstem dysfunction. It is not clear whether there is a relationship among autism, MBD and MR.     

Short-latency somatosensory evoked potentials to median nerve stimulation in patients with diffuse neurologic disease

Short-latency somatosensory evoked potentials were found to be abnormal in 15 of 28 patients with diffuse neurologic disease of varying etiology and severity. These abnormalities often did not directly correlate with the presence or degree of clinical sensory impairment. They were similar to findings in patients with demyelinating and focal lesions of the nervous system. This suggests that the interpretation of these potentials can be done only in the context of the patient's clinical assessment.     

Short-latency somatosensory evoked potentials (SSEPs) of the tibial nerves in spinal cord injuries.

Stimulations of the tibial nerves of 76 spinal cord injured patients revealed short-latency somatosensory evoked potentials (SSEPs) especially P37 recorded from the scalp. The SSEPs findings can be classified by degrees of impairment into 5 different types as follows: Type 1: Absence of P37. This was found in all patients with complete cord lesions as well as patients with loss of joint sense. Type 2: Decreased amplitude and prolonged latency. This was elicited in patients with moderate to severe central cord lesions. Type 3: Prolonged latency only. Type 4: Decreased amplitude only. Type 5: Normal P37, which was mostly seen in patients with mild central cord lesion. The study demonstrated that SSEPs of the tibial nerves are related to joint sense and seem to relate to the extent of cord damage, especially of central cord and complete cord lesions. It can be done as early as during the first week post injury, particularly in an uncooperative patient suspected of having spinal cord injury, in which case the clinical assessment may be difficult and unreliable.     

Short-latency somatosensory evoked potentials correlate with the severity of the neurological deficit and sensory abnormalities following cerebral ischemia

Short-latency somatosensory evoked potentials (SSEPs) were studied in 49 patients who had suffered hemispheric or thalamic ischemia, including 6 patients with transient ischemic attacks (TIAs) and 3 patients with reversible ischemic neurological deficits (RINDs). SSEPs were abnormal in 30 patients (61%). SSEP abnormalities correlated with the presence of sensory deficit and the degree of neurological deficit. SSEPs were normal following TIA but were abnormal in 2 of 3 patients with RINDs. SSEPs were abnormal in some patients without sensory deficits suggesting that sensory pathways may be affected when clinically inapparent.     

Intraoperative localisation of the lip sensory area by somatosensory evoked potentials.

Accurate localisation of the central sulcus enables maximum tumour resection with minimum morbidity in peri-Rolandic surgery. We investigated intraoperative somatosensory evoked potentials (SSEPs) with combined recording of lower lip and median nerve stimuli during craniotomy in nine patients with peri-Rolandic glioma. Using a custom clip electrode, the lip mucous membrane was stimulated with biphasic pulses with 0.2 ms duration, 10-14 mA intensity and a frequency of 0.7 Hz. Polarity inversion of the SSEP was detected across the central sulcus using median nerve and/or lower lip stimulation in eight of the nine patients in whom the tumour did not infiltrate the lip or hand sensory area. Recording of SSEPs with lower lip stimulation is useful if the resection margin is planned lateral to the hand representation area, if the hand representation area is not exposed by the craniotomy, or if the SSEPs for median nerve stimulation are not clear due to tumour infiltration.