Vestibular evoked myogenic potentials and video head impulse test in patients with vertigo,dizziness and imbalance

The aim of this study was to compare vestibular evoked myogenic potentials (VEMP) and video head impulse test (vHIT) results in patients presenting with vertigo and dizziness. We retrospectively analyzed data of all patients with the chief complaint of vertigo, dizziness, or imbalance that underwent VEMP and vHIT from January 2015 to January 2016. A total of 117 patients (73 females, mean age 53.92 ± 16.76) fulfilled inclusion criteria: group 1 included patients with the final diagnosis of vestibular neuritis (VN) (N = 31 (16 right and 15 left VN)), group 2 included patients with the final diagnosis of vertigo of central origin (N = 23) and group 3 included patients with the final diagnosis of unspecified dizziness (N = 63). There was significant correlation between oVEMP asymmetry and asymmetry of the lateral canals 60 ms gains on vHIT (r = 0.225, p = 0.026). Significant correlation between oVEMP and vHIT asymmetry was present in VN patients (r = 0.749, p < 0.001), while no correlation was found in the groups 2 and 3. oVEMP and vHIT lateral canals asymmetries were significantly greater in patients with vestibular neuritis. Furthermore, positive correlations of oVEMP amplitudes with 60 ms gain of the lateral semicircular canal and slope of the anterior semicircular canal on vHIT, and cVEMP with slope of the posterior semicircular canal on the vHIT were found. These changes were significantly more pronounced in patients with vestibular neuritis. In conclusion, VEMPs and vHIT data should be used complementarily; asymmetry on both tests strongly supports peripheral vestibular system involvement.     

Bilateral posterior semicircular canal dysfunction: a new finding with video head impulse test

Journal of Neurology - Development of the video head impulse test (vHIT) assessing all three semicircular canals in both labyrinths has uncovered the existence of new vestibular failure patterns...     

Isolated floccular infarction: impaired vestibular responses to horizontal head impulse

Isolated floccular infarction is extremely rare, and impairments of the vestibulo-ocular reflex (VOR) have not been explored in humans with isolated floccular lesions. The purpose of this study was to examine and report selective impairment of VOR in response to high acceleration using head impulse in a patient with isolated floccular infarction. The patient underwent bedside and laboratory evaluation of vestibular function, which included video-oculography, ocular torsion and the subjective visual vertical, cervical and ocular vestibular-evoked myogenic potentials, bithermal caloric irrigation, rotatory chair test, and the head impulse test (HIT) using search coils. A 70-year-old woman with a unilateral floccular infarction presented with an acute vestibular syndrome with spontaneous nystagmus beating to the lesion side, impaired ipsilesional pursuit, contraversive ocular torsion and tilt of the subjective visual vertical. With rotatory chair testing at low frequencies, horizontal VOR gains were increased. However, VOR gains were decreased with the higher-frequency, higher-speed HIT. While HIT is often normal in patients with central vestibular disorders, decreased HIT responses do not exclude an isolated cerebellar lesion as a cause of the acute vestibular syndrome.     

Separating posterior-circulation stroke from vestibular neuritis with quantitative vestibular testing

ObjectiveTo separate vestibular neuritis (VN) from posteriorcirculation stroke (PCS) using quantitative tests of canal and otolith function.MethodsVideo Head-Impulse tests (vHIT) were used to assess all three semicircular canal pairs; vestibulo-ocular reflex (VOR) gain and saccade metrics were examined. Cervical and ocular-Vestibular-Evoked Myogenic Potentials (c- and oVEMP) and Subjective Visual Horizontal (SVH) were used to assess otolith function.ResultsFor controls (n = 40), PCS (n = 22), and VN (n = 22), mean horizontal-canal VOR-gains were 0.96 ± 0.1, 0.85 ± 0.3 and 0.40 ± 0.2, refixation-saccade prevalence was 71.9 ± 41, 90.7 ± 57, 209.2 ± 62 per 100 impulses and cumulative-saccade amplitudes were 0.9 ± 0.4°, 2.4 ± 2.2°, 8.0 ± 3.5°. Abnormality-rates for cVEMP, oVEMP and SVH were 38%, 9%, 72% for PCS, and 43%, 50%, 91% for VN.A gain ≤0.68, refixation-saccade prevalence of ≥135% and cumulative-saccade amplitudes ≥5.3° separated VN from PCS with sensitivities of 95.5%, 95.5%, and 81.8%, and specificities of 68.2%, 86.4% and 95.5%. VOR-gain and saccade prevalence when combined, separated VN from PCS with a sensitivity and specificity of 90.9%. Abnormal oVEMP asymmetry-ratios were of low sensitivity (50%) but high specificity (90.9%) for separating VN from PCS.ConclusionvHIT provided the best separation of VN from PCS. VOR-gain, refixation-saccade prevalence and amplitude were effective discriminators of VN from PCS.SignificancevHIT and oVEMP could assist early identification of the aetiology of Acute Vestibular Syndrome in the Emergency Room.     

Accuracy of the bedside head impulse test in detecting vestibular hypofunction

Objective

To determine the accuracy of the bedside head impulse test (bHIT) by direct comparison with results from the quantitative head impulse test (qHIT) in the same subjects, and to investigate whether bHIT sensitivity and specificity changes with neuro‐otological training.

Methods

Video clips of horizontal bHIT to both sides were produced in patients with unilateral and bilateral peripheral vestibular deficits (n = 15) and in healthy subjects (n = 9). For qHIT, eye and head movements were recorded with scleral search coils on the right eye and the forehead. Clinicians (neurologists or otolaryngologists) with at least 6 months of neuro‐otological training (“experts”: n = 12) or without this training (“non‐experts”: n = 45) assessed video clips for ocular motor signs of vestibular deficits on either side or of normal vestibular function.

Results

On average, bHIT sensitivity was significantly (t test: p<0.05) lower for experts than for non‐experts (63% vs 72%), while bHIT specificity was significantly higher for experts than non‐experts (78% vs 64%). This outcome was a consequence of the experts'' tendency to accept bHIT with corresponding borderline qHIT values as still being normal. Fitted curves revealed that at the lower normal limit of qHIT, 20% of bHIT were rated as deficient by the experts and 37% by the non‐experts.

Conclusions

When qHIT is used as a reference, bHIT sensitivity is adequate and therefore clinically useful in the hands of both neuro‐otological experts and non‐experts. We advise performing quantitative head impulse testing with search coils or high speed video methods when bHIT is not conclusive.The Halmagyi–Curthoys head impulse test is, at present, the only bedside examination that allows identification of the side of a unilateral hypofunction of the peripheral vestibular system.¹ Head impulses are rapid, passive, unpredictable rotations of the head relative to the trunk. The patient is asked to fix upon a target straight ahead, usually the nose of the examiner, while the examiner turns the patient''s head in the plane of a pair of semicircular canals. The rotations are of low amplitude (10–20°) but of high acceleration (10000°/s²). If the peripheral vestibular system is intact and the vestibulo‐ocular reflex (VOR) operates normally, the patient''s eyes keep their fixations approximately on target (ie, gaze is held relatively stable in space). If not (ie, in the case of a reduced gain of the VOR towards the side of the head impulse), a reflexive saccade back to the examiner''s nose is performed after the end of the head thrust. This corrective saccade indicates a peripheral vestibular hypofunction on the side towards which the preceding head rotation occurred, provided ocular motor function is intact.Head impulses mainly drive the short latency, oligosynaptic VOR pathways from the semicircular canals to the extraocular muscles. Polysynaptic pathways via the cerebellum are less efficient in transmitting such high acceleration vestibular stimuli. The oligosynaptic pathways show distinct non‐linear properties in that the contribution of the signals from the excited semicircular canals to the ocular motor response is greater than the contribution of the signals from the inhibited semicircular canals. This principle, known as Ewald''s second law,² is probably the result of a non‐linear pathway, which during high accelerations is driven into inhibitory cut‐off on the side of inhibited semicircular canals.^3,4 In the case of unilateral peripheral vestibular hypofunction, Ewald''s second law results in an asymmetric gain of the VOR (ie, the gain during high acceleration head rotations towards the lesioned side is lower than towards the healthy side).⁵Halmagyi and Curthoys¹ as well as Foster and colleagues⁶ have shown surpassing accuracy of the bedside head impulse test (bHIT) in patients with complete unilateral vestibular loss. In these patients, both sensitivity and specificity reached 100% with reference to a control group of healthy subjects. In patients with partial vestibular deficits, however, the sensitivity of bHIT is considerably lower, because residual peripheral function results in a smaller gain asymmetry of the VOR. In a general clinical population of patients without and patients with significant asymmetries in caloric testing (canal paresis factor >25%), bHIT sensitivity was approximately 35% and bHIT specificity 95%.^7,8,9 Direct comparison of bHIT with caloric testing, however, is problematic, as head impulses and caloric irrigation probe different frequencies of the VOR. Moreover, central compensation mechanisms in response to a peripheral vestibular deficit are frequency dependent and more often incomplete for higher (head impulses) than for lower frequencies (caloric irrigation).^10,11,12,13Considering these problems of correctly appraising the clinical usefulness of bHIT by caloric testing, we set out to better determine the accuracy of bHIT by comparing it directly with head impulse testing that is assessed quantitatively from simultaneous recordings of eye and head movements with search coils. The result of this quantitative head impulse test (qHIT) was compared with the clinicians'' evaluations of bHIT (presented on video clips) in the same patients. We further asked whether the sensitivities and specificities of bHIT differed depending on the clinicians'' neuro‐otological training.     

What guides decision-making on intravenous thrombolysis in acute vestibular syndrome and suspected ischemic stroke in the posterior circulation?

Journal of Neurology - Intravenous thrombolysis (IVT) is rarely performed in dizzy patients with acute vestibular syndrome (AVS) or acute imbalance (AIS) even if posterior circulation stroke (PCS)...     

Compensatory saccade differences between outward versus inward head impulses in chronic unilateral vestibular hypofunction

The horizontal head impulse test (HIT) is a valuable clinical tool that can help identify peripheral vestibular hypofunction by the refixation (compensatory) saccade that returns the eyes to the target of interest after the head has stopped. We asked if there were differences in the compensatory saccade responses during the HIT when the head was rotated away or toward straight ahead (outward versus inward). We also investigated the influence of a fixation target. Using scleral search-coils, we tested five patients with chronic unilateral vestibular hypofunction (UVH) and three healthy control subjects. In UVH patients, the latencies of both overt and covert saccades were longer when the head was rotated inward from an initially eccentric position, regardless of a visual target. The proportion of HIT with covert saccades was independent of a visual target. In control subjects no compensatory saccades were observed and there were no differences in either angular vestibulo-ocular reflex gain or latency between inward and outward HIT. Our data suggest that inward applied HIT in chronic UVH is more likely to include an overt compensatory saccade based on its lengthened latency. Neither latency nor the occurrence of covert compensatory saccades during HIT depended on a visual target, suggesting they have become a learned behavior in response to chronic UVH.     

Vestibular dysfunction in patients with auditory neuropathy detected by vestibular evoked myogenic potentials

ObjectivesThis study aimed to determine vestibular involvement in patients with auditory neuropathy (AN) using ocular vestibular evoked myogenic potential (oVEMP), cervical vestibular evoked myogenic potential (cVEMP), caloric tests, video Head Impulse Tests (vHIT), and Suppression Head Impulse Paradigm (SHIMP) tests.MethodsTwenty-two patients with AN (study group) and 50 age-and-gender-matched healthy subjects (control group) were enrolled. All patients underwent air-conducted sound oVEMP and cVEMP tests. In the study group, 20 patients underwent a caloric test, 10 patients underwent a video Head Impulse Test (vHIT), and nine patients underwent the Suppression Head Impulse Paradigm (SHIMP) test.ResultsSignificant differences in VEMP abnormalities were found between the two groups. Most AN patients showed no VEMP response, while only a few patients showed VEMP responses with normal parameters. Some AN patients presented abnormal VEMP parameters, including thresholds, latencies, and amplitudes. The abnormal rate (including no response and abnormal parameters) was 91% in the cVEMP test and 86% in the oVEMP test. No significant difference was found between oVEMP and cVEMP abnormalities. AN patients exhibited a 70% abnormal rate in the caloric test. Most AN patients showed normal VOR gains. Most patients showed no overt corrective saccades in vHIT, and exhibited normal anticompensatory saccades in the SHIMP test.ConclusionMany AN patients experience vestibular dysfunction, which may be detected by using a vestibular functional test battery.SignificanceVEMP abnormalities might reflect the status and degree of vestibular involvement in AN.     

Recent advances in central acute vestibular syndrome of a vascular cause

Acute vestibular syndrome (AVS) is characterized by acute onset of spontaneous prolonged vertigo (lasting days), spontaneous nystagmus, postural instability, and autonomic symptoms. Peripheral AVS commonly presents as vestibular neuritis, but may also include other disorders such as Meniere's disease. Vertigo in central AVS due to vertebrobasilar ischemic stroke is usually accompanied by other neurological dysfunction. However it can occur in isolation and mimicking peripheral AVS, particularly with cerebellar strokes. Recent large prospective studies have demonstrated that approximately 11% of patients with isolated cerebellar infarction presented with isolated vertigo mimicking peripheral AVS, and the bedside head impulse test is the most useful tool for differentiating central from peripheral AVS. Herein we review the keys to the diagnosis of central AVS of a vascular cause presenting with isolated vertigo or audiovestibular loss.     

血管源性中枢急性前庭综合征及其眼震形式

急性前庭综合征（acute vestibular syndrome,AVS）是以急性持续性眩晕起病,伴有恶心、呕吐,自发眼震,步态不稳,头动不能耐受等症状的临床综合征,持续时间超过24?h,大多为数天或数周。中枢性AVS以血管源性常见,其中大多数为后循环缺血性卒中,尤其部分脑干、小脑梗死常表现为急性孤立性眩晕,这类患者的诊断极具挑战性。随着前庭及眼动生理机制研究的深入,基于前庭、眼动及姿势平衡系统等方面的床旁检查重要性也日益凸显。眩晕患者的床旁检查,除了常规的神经科及耳科查体外,基于前庭-眼反射的各类眼震的评价极有助于快速诊断、识别中枢性AVS。本文对血管源性中枢性AVS的神经血管解剖基础、脑干和小脑卒中所致AVS的眼震特点等进行了综述归纳。     

Three versus seven days to return-to-work after mild traumatic brain injury: a randomized parallel-group trial with neuropsychological assessment

Although most patients with a mild traumatic brain injury (mTBI) recover within days to weeks, some experience persistent physical, cognitive and emotional symptoms, often described as post-concussion syndrome (PCS). The optimal recovery time including return-to-work (RTW) after mTBI is unclear. In this single-centre parallel-group trial, patients assigned three days (3D-group) or seven days (7D-group) sick leave were compared with a comprehensive neuropsychological test battery including the Post-Concussion Symptom Scale (PCSS) within one week, after three and 12 months post-injury. The influence of the effective time until RTW on post-concussional symptoms and cognitive performance was analysed. The 3D-group rated significantly higher mean scores in some PCSS symptoms, tended to fulfil diagnosis criteria of PCS more often and showed better cognitive performance in several neuropsychological test scores than the 7D-group at all three time-points of follow-up. Overall, patients returned to work 11.35 d post-injury, thus distinctly above both recommended sick leaves. There was a trend for longer sick leave in patients randomized into the 3D-group. Further analyses revealed that the group with an absolute RTW within one week showed lower symptom severity in fatigue at 3 and 12 months, less PCS and faster performance in fine motor speed at 12 months than the group with an absolute RTW after one week. Our data underline the heterogeneity of mTBI and show that acute and sub-acute symptoms are not prognostic factors for neuropsychological outcome at one year. Later, ability to work seems to be prognostic for long-term occurrence of PCS.     

Diagnostic accuracy of acute vestibular syndrome at the bedside in a stroke unit

Acute vestibular syndrome may be due to vestibular neuritis (VN) or posterior circulation strokes. Bedside ocular motor testing performed by experts is superior to early MRI in excluding strokes. We sought to demonstrate that differentiation of strokes from VN in our stroke unit is reliable. During a prospective study at a tertiary hospital over 1 year, patients with AVS were evaluated in the emergency department (ED) and underwent admission with targeted examination: gait, gaze-holding, horizontal head impulse test (hHIT), testing for skew deviation (SD) and vertical smooth pursuit (vSP). Neuroimaging included CT, transcranial Doppler (TCD) and MRI with MR angiogram (MRA). VN was diagnosed with normal diffusion-weighted images (DWI) and absence of neurological deficits on follow-up. Acute strokes were confirmed with DWI. A total of 24 patients with AVS were enrolled and divided in two groups. In the pure vestibular group (n = 20), all VN (n = 10/10) had positive hHIT and unidirectional nystagmus, but 1 patient had SD and abnormal vertical smooth pursuit (SP). In all the strokes (n = 10/10), one of the following signs suggestive of central lesion was present: negative hHIT, central-type nystagmus, SD or abnormal vSP. Finding one of these was 100% sensitive and 90% specific for stroke. In the cochleovestibular group (n = 4) all had normal DWI, but 3 patients had central ocular motor signs (abnormal vertical SP and SD). Whilst the study is small, classification of AVS in our stroke unit is reliable. The sensitivity and specificity of bedside ocular motor testing are comparable to those previously reported by expert neuro-otologists. Acute cochleovestibular loss and normal DWI may signify a labyrinthine infarct but differentiating between different causes of inner ear dysfunction is not possible with bedside testing.     

The functional head impulse test: preliminary data

The functional head impulse test is a new test of vestibular function based on the ability to recognize the orientation of a Landolt C optotype that briefly appears on a computer screen during passive head impulses imposed by the examiner over a range of head accelerations. Here, we compare its results with those of the video head impulse test on a population of vestibular neuritis patients recorded acutely and after 3 months from symptoms onset. The preliminary results presented here show that while both tests are able to identify the affected labyrinth and to show a recovery of vestibular functionality at 3 months, the two tests are not redundant, but complementary.     

Scopolamine alters rhesus monkey performance on a novel neuropsychological test battery.

Rhesus monkeys (6) were trained on a test battery including cognitive tests adapted from a human neuropsychological assessment battery (CANTAB; CeNeS, Cambridge, UK) as well as a bimanual motor skill task. The complete battery included tests of memory (delayed non-match to sample, DNMS; self-ordered spatial search, SOSS), reaction time (RT), motivation (progressive ratio; PR) and fine motor coordination (bimanual). The animals were trained to asymptotic performance in all tasks and then were administered two of the four CANTAB tasks on alternate weekdays (PR/SWM; DNMS/RT) with the bimanual task being administered on each weekday. The effect of acute administration of scopolamine (3-24 microg/kg, i.m.) on performance was then determined. Although performance on DNMS was impaired there was no interaction of drug treatment with retention interval, suggesting that scopolamine does not increase the rate of forgetting in this task. Scopolamine administration produced a decrement in SOSS performance that was dependent on task difficulty as well as dose. Scopolamine also impaired motor responses, resulting in increased time required to complete the bimanual motor task and increased movement time in the RT task. Performance in the PR task was decreased in a dose-dependent fashion by scopolamine. The results suggest that scopolamine interferes with memory storage and motor responses but not memory retention/retrieval or vigilance. The findings demonstrate that the test battery is useful for distinguishing the effects of neuropharmacological manipulation on various aspects of cognitive performance in monkeys.     

Argatroban anticoagulation in patients with a history of heparin-induced thrombocytopenia

INTRODUCTION: Heparin therapy is not recommended for patients with a history of heparin-induced thrombocytopenia (HIT), except in specialized situations, because this treatment can lead to severe reactions including thrombocytopenia and thrombosis. However, the optimal management of patients with a history of HIT requiring acute anticoagulation has not yet been clarified because of the lack of prospective studies. We evaluated the safety and efficacy of argatroban, a direct thrombin inhibitor, as an anticoagulant in patients with a history of HIT needing acute anticoagulation. METHODS: Thirty-six patients with a history of serologically confirmed HIT were treated prospectively with argatroban [median (5th-95th percentile) dose of 2.0 (1.0-4.3) microg/kg/min for 4.0 (0.7-8.4) days]. Prospectively defined endpoints included successful anticoagulation (therapeutic activated partial thromboplastin time), and bleeding, new thromboembolic events, or other adverse effects during therapy or within 30 days following its cessation. RESULTS: All patients required acute anticoagulation with the most common admission diagnoses being deep venous thrombosis or pulmonary embolism (n=13) and chest pain or acute coronary syndrome (n=12). Eleven patients had previously received argatroban therapy for HIT; one patient underwent two treatment courses of argatroban for a history of HIT. The median (5th-95th percentile) time between the past diagnosis of HIT and initiation of argatroban was 7.5 (0.4-114.6) months. All evaluable patients were successfully anticoagulated. No patient had major bleeding, new thromboembolic events, or other adverse effects. There were no adverse events related to reexposure. CONCLUSIONS: Argatroban can provide safe and effective anticoagulation, on initial or repeat exposure, in patients with a history of HIT.     

Effects of parameters of video head impulse testing on visually enhanced vestibulo-ocular reflex and vestibulo-ocular reflex suppression

ObjectiveTo investigate the main effects of some testing and analysis variables on clinically quantified visually enhanced vestibulo-ocular reflex (VVOR) and vestibulo-ocular reflex suppression (VORS) results using video head impulse test.MethodsThis prospective observational clinical study included 19 healthy participants who underwent the VVOR and VORS tests. The effect of demographic variables, head oscillation frequency, rotation direction, visual acuity and analysis time window width and location of the recorded tests on the quantified results of both VVOR and VORS were evaluated. And specifically, for the VORS test the effect of cognitive reinforcement of the participant during testing was evaluated.ResultsA statistically significant difference was observed among the VVOR, non-reinforced VORS, and reinforced VORS tests for mean gain values of 0.91 ± 0.09, 0.6 ± 0.15, and 0.57 ± 0.16, respectively (p < 0.001). The optimized linear mixed-effect model showed a significant influence of frequency on the gain values for the reinforced and non-reinforced VORS tests (p = 0.01 and p = 0.004, respectively). Regarding the gain analysis method, statistically significant differences were found according to the short time interval sample location of the records for the initial location of the VVOR test (p < 0.006) and final location of the reinforced VORS test (p < 0.023).ConclusionSignificant differences were observed in the gain values according to VVOR and VORS testing. Head oscillation frequency is a significant factor that affects the gain values, especially in VORS testing. Moreover, in VORS testing, participant concentration has a significant effect on the test for obtaining suppression gain values. When a short time interval sample is considered for VVOR and VORS testing, intermediate time samples appear the most adequate for both tests.SignificanceThe quantified visually enhanced vestibulo-ocular reflex (VVOR) and vestibulo-ocular reflex suppression (VORS) tests have recently been added to the assortment of available clinical vestibular tests. However, despite the clinical validity of these quantified tests that appear to be of increasing clinical interest, the effects of most of the clinical testing methods and mathematical variables are not well defined.In this research we describe what are the main collecting and analysis variables that could influence to the VVOR and VORS tests. Specially for VORS test, participant concentration on test tasks will have positive effect on the measured vestibulo-ocular reflex (VOR) suppression.     

Reversed Corrective Saccades during Head Impulse Test in Acute Cerebellar Dysfunction

Patients with cerebellar lesions may show horizontal (positive)- or downward (perverted)-corrective saccades during horizontal head impulse test (HIT). However, corrective saccades in the direction of head rotation (reversed corrective saccades) have not been reported during HIT. We present two patients who showed reversed corrective saccades during horizontal HIT as an initial sign of acute cerebellitis. In contrast to the corrective saccades mostly observed in peripheral vestibular paresis, this paradoxical response indicates abnormally increased vestibulo-ocular responses due to cerebellar disinhibition over the vestibulo-ocular reflex. This paradoxical response should be considered an additional bedside cerebellar sign.     

Whole blood impedance aggregometry detects heparin-induced thrombocytopenia antibodies

Heparin-induced thrombocytopenia (HIT) is a serious complication of heparin use. IgG antibodies to complexes of platelet factor 4 (PF4) and heparin trigger the clinical manifestations of HIT. Only a subset of these antibodies will activate platelets and these can only be identified with platelet aggregation (functional) assays. Heparin-induced platelet aggregation (HIPA) and ¹⁴C-serotonin release (SRA) assays for HIT are time-consuming and complex to perform. We have developed a whole blood impedance (WBI) test using the new Multiplate^® analyser.All samples referred to our laboratory over a 10 month period were screened for heparin-PF4 antibodies by an ELISA method (Zymutest HIA IgG). The 4T's score was used to assess HIT pretest probability.Twenty antibody positive samples were further tested by all three functional assays: light transmission aggregometry (LTA), SRA and WBI. Thirteen out of twenty samples were positive by LTA (10 patients) and 15 by WBI (11 patients). SRA, considered to be the gold standard, was used as a confirmatory test and 11 were found to be positive (10 patients); four discrepant samples were weakly positive by WBI. The prevalence of a positive functional test was strongly correlated with the 4T's clinical risk score, but a small number of low-risk patients had positive functional assays.In this study, the WBI assay detected all SRA positive patients and was positive for two others suggesting greater sensitivity. The rapid and easy to perform assay may be a useful tool for haematology laboratories to detect platelet-activating HIT antibodies.     

Sensitivity to light and sound following minor head injury

9 consecutively referred closed head injury (CHI) patients were assessed for sensitivity to light and sound stimuli, within 7-19 days of injury, on both objective and subjective measures. Patients were matched with controls on age, sex, race, socio-economic status and order of test administration. The mean luminance (1366 lux) tolerated by CHI patients was significantly lower (0.01 level by Student's t-test for related samples) than that tolerated by controls (1783 lux). The mean sound intensity tolerated by CHI patients was also lower (82 db) than for controls (94 db), though this difference was not statistically significant. Subjective ratings of sensitivity made by CHI patients after exposure to intense sound and light stimuli, showed no relationship to objective ratings of tolerance. The results demonstrate an objective basis for complaints of increased sensitivity, at least to light, following CHI. These findings do not support earlier "psychogenic" explanations of post-concussion syndrome (PCS) etiology.     

Clinical evaluation of acute systemic reaction and detection of IgG antibodies against PF4/heparin complexes in hemodialysis patients

Heparin-induced thrombocytopenia (HIT) is a pathophysiological syndrome caused by platelet-activating antibodies that recognize PF4/heparin complexes. The abrupt onset of HIT following intravenous bolus heparin is known as an acute systemic reaction. Clinical features of this type of HIT may be similar to those of common complications during hemodialysis. The aim of the study was to identify whether the clinical features of the acute systemic reaction are caused by HIT or dialytic complications. Twenty-seven dialytic patients who had thrombocytopenia and clinical features of an acute systemic reaction were enrolled out of 202 HIT-suspected patients. Thirteen patients had HIT confirmed due to the presence of positive functional and immunoassays. Eight of the thirteen patients presented with acute systemic reactions due to HIT. The most common symptom of acute systemic reaction was dyspnea. The other nineteen patients, involving both HIT and non-HIT patients, had dialysis-complicated ASR. The major feature of the acute systemic reaction in hemodialysis was hypotension and its relevant symptoms. An immunoassay for the detection of IgG antibodies against PF4/heparin complexes (HIT-IgG) showed the wide-range linearity of the calibration curve by employing three concentrations of recombinant mouse monoclonal antibodies for PF4/heparin complexes. The results are expressed as micrograms of IgG in one milliliter. Significantly high levels in thirteen HIT patients were compared with levels in fourteen non-HIT patients. The highest median of 1,530 μg/ml (IQR: 3,267-813) was obtained in the presence of HIT associated with an acute systemic reaction. In HIT patients who did not show characteristics of an HIT-derived acute systemic reaction, the median was 339 μg/ml (1,178-834). Despite showing a positive ELISA, nine non-HIT patients without any platelet-activating antibodies showed a value of 97 μg/ml (166-56). The lowest median of 8.3 μg/ml (11-6) was in non-HIT patients with a negative ELISA. In conclusion, measurements of HIT-IgG -specific antibodies can facilitate an appropriate estimation in hemodialysis patients of whether the clinical features of an acute systemic reaction are caused by HIT or dialytic complications.