Maurice Rappaport

Evoked Potentials and Head Injury: 1. Rating of Evoked Potential Abnormality

This paper describes a method for rating the degree of abnormality of auditory, visual and somatosensory evoked potential patterns in head injury (HI) patients. Criteria for judging degree of EP abnormality are presented that allow assessment of the extent and severity of subcortical and cortical dysfunction associated with traumatic brain damage. Interrater reliability data based upon blind ratings of normal and HI patients are presented and shown to be highly significant. Tables of normative values of peak latencies and amplitudes are given and illustrations of EP patterns of different degrees of abnormality are presented.

Evoked Potentials and Head Injury: 2. Clinical Applications:

The method of rating abnormality of evoked brain potential patterns and assessing the extent and severity of cortical and subcortical brain dysfunction in head injury patients described in Part I is applied in a clinical context. Evoked potential abnormality (EPA) scores are found to be significantly correlated both with admission and outcome disability approximately one year after head injury. Correlations increase with the increase in the number of sensory modalities tested. Correlations between EPA scores and clinical disability (measured by the Disability Rating Scale) decrease with time after injury. Significant correlations, however, persist for about 60 days after onset of injury. It was found that EP pattern abnormalities can reflect specific sensory (and at times motor) deficits in noncommunicative patients and thereby contribute significantly to early treatment and rehabilitation planning.

Visual scanning and matching dysfunction in brain-damaged patients with drawing impairment.

Visual matching and visual exploration were examined in 7 normal subjects and 20 brain-damaged patients with drawing impairment measured by the Bender Gestalt Visual-Motor Test. Right brain-damaged patients made significantly more errors of rotation and integration than left brain-damaged patients. Selecteded Bender figures were also used as stimuli for both visual matching and visual exploration tests. The ability to match Bender figures was found to be impaired in right but not left brain-damaged patients. All patients showed eye movement and fixation patterns different from those normals. Patients essentially had more fixations and shorter fixation durations. Significant intercorrelations were found between the total Bender Gestalt score and visual matching and visual exploration scores. These findings indicate that visual matching and visual exploration measures can be used to evaluate perceptual impairment in individuals who do not have adequate motor responses or where impaired motor responses may confound interpretations about visual cognitive impairment.

Intermediate and long latency SEPs in relation to clinical disability in traumatic brain injury patients

Intermediate (0-60 ms) and long latency (0-500 ms) somatosensory evoked potential (SEP) patterns were compared in terms of their relationship to degree of clinical disability in severe traumatic brain injury patients. Long latency (LL) SEP patterns correlated significantly with clinical disability as measured by the Disability Rating scale while intermediate latency (IL) SEP patterns did not. Evoked potential abnormality (EPA) scores based upon LL SEP patterns appear better able to reflect extent and severity of brain dysfunction and overall clinical condition than do IL SEP patterns for severe traumatic brain injury patients.

Somatosensory Evoked Responses to Dermatomal Stimulation in Cervical Spinal Cord Injured and Normal Subjects

This exploratory study investigates dermatomal evoked potential patterns in the upper extremities of normal and spinal cord injured subjects. Fifteen normal subjects without neurologic deficits and twelve patients with partial or complete spinal cord injuries were tested at dermatomal levels C5, C6, C7, C8, and T1, and also at median and ulnar nerve sites. Responses were recorded at the scalp. Analyses of evoked response patterns included measurement and comparison of peak and interpeak latencies and amplitudes as well as blind ratings of the degree of abnormality of evoked potential waveforms. Analyses were also made of relationships between evoked potential data and neurological findings on clinical examination. There appeared to be a fairly consistent SEP response among normals when dermatomes C6 through C8 are stimulated. Less consistent responses are observed when C5 and T1 are stimulated. In general, spinal cord injured subjects as compared to normal subjects had evoked responses with less consistent peaks, more amplitude diminution, and greater diffuseness and overall pattern abnormality even at dermatomal levels that were intact on clinical neurologic examination. There was also a distinct progression of overall SEP abnormality in dermatomes with impaired vibration, light touch, and position sense. There were no consistent differences in interpeak latencies between SEPs of normal and spinal cord injured subjects at intact dermatomes, but there were significant differences in EP abnormalities (EPA scores). Possible reasons for the differences in the SEP responses between normals and spinal cord injured subjects include spinal cord injury not detectable by clinical exam. Difficulty in obtaining objective and accurate sensory reports also contributes to data unreliability. In conclusion, we believe that stimulation of specific sensory dermatomes merits further study, as it has a number of possible clinical uses. These include: (1) surgical monitoring at more specific levels than monitoring with mixed nerve root stimulation, (2) for study of specific nerve root injury, and (3) as an aid in examining the neurological status in acutely injured spinal cord patients who are unable to cooperate adequately during examination, such as the very young or those with lowered levels of awareness associated with head injury. Additional information which could be useful to obtain is cervical dermatomal stimulation with spinal recording sites.

Survival in Young Children after Drowning: Brain Evoked Potentials as Outcome Predictors

Twenty young children between the ages of 4 and 103 months involved in drownings had brain evoked potential (EP) studies done shortly after the incident (median 2 days) to determine if auditory click and visual flash EP patterns were predictive of outcome. Results were examined in relation to good survival or non/poor (vegatative) level of survival. Results were also compared to selected clinical and laboratory data previously reported as predicting outcome. These preliminary findings indicate that if patients have evoked potential abnormality (EPA) scores greater than 2.7 there is little chance of survival. With EPA scores below 2.7 it was found that there is a good chance of survival. Cortical responses to auditory and visual stimulation were observed to be good predictors of outcome despite their inherent variability in young children and the presence of barbiturate coma. Brainstem responses to auditory stimulation alone were poor predictors. Previously reported clinical and laboratory predictors of outcome did not hold up except for muscle flaccidity which, when present, was associated with non/poor survival.

Assessing the costs and outcomes together: Cost effectiveness of two systems of acute psychiatric care

This paper describes the research findings and methodology used to evaluate the relative cost effectiveness of two systems of acute psychiatric care: system I when only a general hospital unit was available and system 2 when a psychiatric health facility was added to the general hospital service system. The cost analysis methodology is described in detail. Theta, cost-outcome matrices, and data analytic techniques useful in making cost effectiveness judgments and program policy decisions are demonstrated. Problems associated with conducting this type of research in a service delivery system are described and discussed. Clinical outcome in system 1, when only the general hospital unit was available, was consistently better. Per diem costs for system 2, consisting of the general hospital unit and a nonhospital psychiatric health facility, were significantly less. However, the increased length of stay for system 2 patients made episode cost comparisons nearly equal between the two systems of health care. Results suggested the need for modifications in the new service system and the importance of assessing the cost and outcome of treatment simultaneously in making program policy decisions.

Effects of stimulus intensity on posterior tibial nerve somatosensory evoked potentials

Relationships between stimulus intensity and peak latencies and amplitudes in posterior tibial nerve somatosensory evoked potential patterns were evaluated in ten healthy subjects. Eight intermediate latency peaks between 30 and 125 milliseconds (ms) after stimulus onset and seven amplitudes were analyzed. In general, there was a decrease in latency with each increase in stimulus intensity over a five step intensity range between 5 and 19 milliamps (mA) for most peaks. Similarly, increases in amplitudes generally occurred with increases in stimulus intensity for most peaks. Later peaks N105 and P115 as well as amplitudes P90-N105 and N105-P115 were least sensitive to stimulus intensity changes. The greatest changes in peak latency and amplitude occurred as stimulus intensity was increased from 7 to 11 mA. Beyond 11 mA relatively little change was observed in either peak latencies or amplitudes. Under anesthesia, by contrast, there was no stimulus intensity-peak latency interaction and beyond 11 mA there were decreases in amplitudes. Possible reasons for these findings are discussed.

Dermatomal somatosensory evoked potentials in brachial plexus injuries

The dermatomally stimulated somatosensory evoked potential is an essentially painless, noninvasive procedure that can add useful information to the diagnosis of the site and extent of brachial plexus injuries. In this study, 13 patients with unilateral brachial plexus injuries who had previously undergone conventional electromyographic testing underwent somatosensory evoked potential recording with median, ulnar, radial, musculocutaneous nerve and C5, C6, C7, C8 and T1 dermatomal stimulation. There was no significant difference in the peak latencies, interpeak latencies, or amplitudes of the major peaks between the normal values and the values from the affected levels. However, analysis for absence or presence of major peaks from side-to-side was useful in supporting the data from electromyographic and radiologic studies, as well as in providing more specific information as to the level of injury and extent of injury in two of the cases. The accurate diagnosis can provide the information needed to determine patient treatment as well as plan the rehabilitation program of the patient. The dermatomal somatosensory evoked potential can be a useful supplement to the assessment of the patient with a brachial plexus injury.

Effects of Stimulus Intensity on Direct Recordings of Eighth Nerve Auditory Evoked Responses

Effects of auditory stimulus intensity on auditory nerve and brainstem evoked potential patterns recorded simultaneously from the scalp and directly from the eighth nerve were compared for an anesthetized patient undergoing surgery for macrovascular decompression. Replicable robust potentials were readily obtained from a recording electrode on the eighth nerve less than half a second after as few as 15 stimulations. Less robust and less readable evoked potential patterns were obtained from scalp recordings after 30 seconds and about 900 stimulations. It was observed in the direct auditory evoked response (DAER) that there is a systematic decrease in peak latencies with each 10 dB increase in stimulus intensity between 60 and 90 dB nHL. Also, with each 10 dB increase in stimulus intensity there is an increase in amplitude of the DAER action potential between 70 and 90 dB nHL but not between 60 and 70 dB.