Alice V. Fann

The P50 midlatency auditory evoked potential in patients with chronic low back pain (CLBP)

OBJECTIVE Patients with Chronic Low Back Pain (CLBP) show arousal, attentional and cognitive disturbances. The sleep state-dependent P50 midlatency auditory evoked potential was used to determine if patients with CLBP [with and without co-morbid depression (DEP)] show quantitative disturbances in the manifestation of the P50 potential. METHODS P50 potential latency, amplitude and habituation to repetitive stimuli at 250, 500 and 1000ms interstimulus intervals (ISIs) was recorded, along with the McGill Pain Questionnaire-Short Form (MPQ-SF). CLBP subjects (n=42) were compared with Controls (n=43), and with subjects with DEP only (n=6). Of the CLBP subjects, 20/42 had clinical depression (CLBP+DEP); 8/20 were taking anti-depressant medication (CLBP+DEP+med), the others were not (CLBP+DEP-med). RESULTS There were no differences (ANOVA) in age, sex or P50 potential latency, although there was a trend towards increased latencies in CLBP groups. P50 potential amplitude was lower in CLBP groups, but not in sub-groups, again indicating a trend. P50 potential habituation was decreased in the DEP only subjects at the 250m ISI, and decreased in CLBP+DEP-med subjects at the 500ms ISI. This difference was not present in CLBP+DEP+med subjects. The MPQ-SF revealed that patients with CLBP and CLBP+DEP-med showed lower pain scores than CLBP+DEP+med patients. CONCLUSIONS There is decreased habituation of the P50 potential habituation in unmedicated patients with CLBP+DEP compared to Controls. SIGNIFICANCE Patients with CLBP+DEP-med may be less able to disregard incoming sensory information, including painful sensations, but anti-depressant medications help correct this deficit. However, their perception of pain may be increased by medication.

The sleep state-dependent midlatency auditory evoked P50 potential in various disorders

The P50 potential is a midlatency auditory evoked response which is sleep state-dependent, habituates rapidly and is blocked by the muscarinic cholinergic antagonist scopolamine. It is thought to be generated, at least in part, by ascending projections of the reticular activating system. The amplitude of the P50 potential can be used as a measure of level of arousal, while the degree of habituation to repetitive stimulation can be used as a measure of sensory gating. We studied these processes in three conditions which show sleep-wake cycle dysregulation and attentional disturbance, but differ greatly in their etiology, depression, Huntington’s disease and rotation-induced motion sickness. Subjects with depression and rotation-induced motion sickness showed significant decreases in the habituation of the second of paired evoked responses, while Huntington’s disease subjects showed decreased amplitude as well as decreases in the habituation of the second P50 potential. This waveform may represent the manifestation of pre-attentional processes, and may become a useful measure for monitoring the severity, progression and/or remission of disorders which affect these processes.

The reliability of postural x-rays in measuring pelvic obliquity

OBJECTIVE To assess the interrater and intrarater reliability of two methods of measurement of postural radiographs for determining the amount of pelvic obliquity. DESIGN Four blinded raters evaluated the amount of pelvic obliquity using two measurement methods. SETTING Physical medicine and rehabilitation outpatient clinic in a VA hospital. PARTICIPANTS Fifty-two randomly chosen radiographs from 36 patients referred to a clinic to evaluate and treat pelvic obliquity. MEASURES Amount of pelvic obliquity was determined by line of eburnation and by the intersulcate line. Pearsons correlation coefficients and percent agreements were calculated for each set of measurements. RESULTS Pearsons correlation coefficients and percent agreements were higher for both interrater and intrarater measurements for the intersulcate line. CONCLUSION Intersulcate line is the more reliable method for determining the amount of pelvic obliquity and will be used in future studies to assess the effectiveness of correcting pelvic obliquity to improve chronic back pain.

Poster 14: Hypertension as the sole indication of posttraumatic hydrocephalus: a case report1

Abstract Setting: Inpatient rehabilitation ward in pediatric hospital. Patient: A 7-year-old girl with traumatic brain injury. Case Description: The patient was admitted after being hit by a truck while she was walking. She lost consciousness and had an admission Glasgow Coma Scale score of 3. Her initial head computerized axial tomography showed diffuse axonal injury in her left parietal white matter, along with intracerebral, intraventricular, and brainstem hemorrhage. She was admitted to the intensive care unit for increased intracranial pressure (ICP), pneumonia, and multiple fractures, which were managed medically. Her ICP monitoring was eventually discontinued. On transfer to the rehabilitation ward she had a Rancho Los Amigos (RLA) level of 3. She was agitated and confused with a blood pressure of 104/74mm/Hg. A week after transfer, the patient was noted to have hypertension with systolic blood pressure in the 130 range, with occasional readings in the 150 range and diastolic blood pressure in the 90 range. Cardiac work-up was negative. The patient was started on propranolol and showed minimal improvement in blood pressure. Head computed tomography showed interval development of marked ventriculomegaly involving the lateral, third and fourth ventricles, compatible with communicating hydrocephalus. She underwent ventriculoperitoneal shunt placement. Assessment/Results: Within 3 days of the shunt placement, her hypertension improved. Propranolol was switched to atenolol, which was weaned over next 7 days. Her hypertension was alleviated. The patient continued to improve cognitively with a discharge RLA level of 6. Discussion: This is the first reported case, to our knowledge, of minimally elevated blood pressure as a sole sign of posttraumatic hydrocephalus. Conclusions: Physicians should be highly suspicious of hydrocephalus in posttraumatic brain injury cases. A minimally elevated blood pressure may be the only sign of it.

Poster 197: Hypotension in poststroke patients: effects on outcome.1

Abstract Objectives: To evaluate (1) the incidence of orthostatic hypotension and hypotension without documented orthostatic blood pressures in poststroke patients who participate in inpatient rehabilitation, and (2) whether hypotension increases length of stay (LOS) or FIM™ instrument changes compare with stroke patients who do not have hypotension. Design: Retrospective study. Setting: Veterans Affairs inpatient rehabilitation ward. Participants: 75 subjects (74 men, 1 women) with first-time acute cerebrovascular accident admitted to rehabilitation floor. Interventions: Not applicable. Main Outcome Measures: Acute and rehabilitation LOS, admission and discharge FIM scores, FIM change, and FIM efficiency (FIM change/rehabilitation LOS). Results: 25 subjects had hypotension, 7 of 25 subjects had orthostatic hypotension, and 18 of 25 had hypotension (at least >20mmHg decrease in blood pressure from the baseline with or without dizziness) without documented orthostatic blood pressures. 50 subjects had no hypotension. Hypotension subjects had a mean age of 72.0±10.7 years compared with the nonhypotensive subjects, who had a mean age of 66.8±12.0 years ( P P P P Conclusions: There is a high prevalence (33%) of hypotension in our study patients who were admitted to the rehabilitation floor. Hypotension adversely effected the LOS and FIM efficency. Hypotension needs to be aggressively taken into consideration by the rehabilitation team early to improve the efficiency of care.

Poster 113: Sensory-gating deficits in patients with chronic low back pain: a P50 midlatency auditory evoked potential study.1

Abstract Objective: To describe the characteristics of P50 auditory evoked potentials (AEPs) in patients with chronic low back pain (CLBP) with and without depression (DEP). Design: Cross-sectional descriptive. Setting: Outpatient clinic of Veterans Affairs hospital. Participants: 42 subjects (23 women, 19 men) with CLBP. Interventions: Not applicable. Main Outcome Measures: P50 AEP habituation (a measure of sensory gating). Pairs of click stimuli at interstimulus intervals of 250, 500, and 1000ms were presented at a 0.2-Hz rate. Results: Subjects with CLBP were compared with 37 subjects (18 men, 19 women) without CLBP and 6 subjects (all men) with depression. 20 of 42 subjects with CLBP also had depression (CLBP+DEP); 8 of 20 were taking antidepressant medications (CLBP+DEP+med). Statistics were done using analyses of variance. At the 250 interstimulus interval, all control groups had a higher percentage of habituation than the experimental groups. At the 500 interstimulus interval, CLBP+DEP subject habituation was 53%±6% compared with controls at 34%±6% (P=.0312); CLBP+DEP+meds was 43%±8% compared with CLBP+DEP+no meds at 67%±6% (P=.0026); CLBP+DEP+meds compared with depression only at 65%±29% (P=.04). At the 1000 interstimulus interval, CLBP+DEP+no meds was 84%±9% compared with control subjects at 52%±10% (P=.0343), and CLBP+DEP+meds was 54%±9% compared with CLBP+DEP+no meds at 84%±9% (P=.0466). There were no significant differences between those with CLBP only and age- and gender-matched control subjects. Conclusions: There was decreased habituation (inhibition) of the P50 AEP in patients with CLBP+DEP compared with those with CLBP only or controls. Antidepressant medications normalize this decreased habituation, which presumably leads to sensory-gating deficits. Patients with CLBP+DEP may be distractible and less able to disregard incoming sensory information, including painful sensations.