A. Amantini

Consensus on the use of neurophysiological tests in the intensive care unit (ICU): Electroencephalogram (EEG), evoked potentials (EP), and electroneuromyography (ENMG)

STUDY AIM To provide a consensus of European leading authorities about the optimal use of clinical neurophysiological (CN) tests (electroencephalogram [EEG]; evoked potentials [EP]; electroneuromyography [ENMG]) in the intensive care unit (ICU) and, particularly, about the way to make these tests clinically useful for the management of individual patients. METHODS This study gathered together several European clinical neurophysiologists and neurointensivists whose leading contributions in the adult or paediatric ICU and in continuous neuromonitoring had been peer-acknowledged. It was based on both a literature review and each participants own experience. Given the methodological impossibility to gather studies fulfilling criteria of evidence-based medicine, this article essentially relies on expert opinions that were gained after several rounds, in which each expert was invited to communicate his own contribution to all other experts. A complete consensus has been reached when submitting the manuscript. RESULTS What the group considered as the best classification systems for EEG and EP abnormalities in the ICU is first presented. CN tests are useful for diagnosis (epilepsy, brain death, and neuromuscular disorders), prognosis (anoxic ischemic encephalopathy, head trauma, and neurologic disturbances of metabolic and toxic origin), and follow-up, in the adult, paediatric, and neonatal ICU. Regarding prognosis, a clear distinction is made between these tests whose abnormalities are indicative of an ominous prognosis and those whose relative normalcy is indicative of a good prognosis. The prognostic significance of any test may vary as a function of coma etiology. CONCLUSION CN provides quantitative functional assessment of the nervous system. It can be used in sedated or curarized patients. Therefore, it should play a major role in the individual assessment of ICU patients.

Monitoring of somatosensory evoked potentials during carotid endarterectomy

SummarySomatosensory evoked potentials (SEPs) were monitored in the course of 368 carotid endarterectomies (CEAs) carried out in 312 patients. In an initial group of 26 patients the shunt was used routinely while in a second group, involving 342 CEAs, it was applied selectively on the basis of modifications which the SEP underwent during clamping. The criterion for shunting was the progressive reduction, up to 50%, of the N20-P25 amplitude. New postoperative neurological deficits appeared in 6 patients, all of whom displayed a transitory SEP flattening. The SEPs of 2 of these returned to normal by the time they awoke and both showed a clinical deficit homolateral to the operated side. In only 2 cases did the deficit fail to regress completely and their postoperative CT scans revealed ischaemic lesions. A positive relationship emerged between SEP changes and back pressure values; nonetheless, as many as 75% of the patients with low residual back pressure values (< 25 mm Hg) tolerated the clamping. SEP monitoring appears to provide a reliable basis for selectively applying a shunt when there is a high risk of haemodynamic ischaemia during clamping.

Continuous EEG-SEP monitoring of severely brain injured patients in NICU: methods and feasibility.

AIMS To evaluate the feasibility of a continuous neurophysiologic monitoring (electroencephalography (EEG)-somatosensory evoked potentials (SEPs)) in the neuro-intensive care unit (NICU), taking into account both the technical and medical aspects that are specific of this environment. METHODS We used an extension of the recording software that is routinely used in our unit of clinical neurophysiology. It performs cycles of alternate EEG and SEP recordings. Raw traces and trends are simultaneously displayed. Patient head and stimulator box are placed behind the bed and linked to the ICU monitoring terminal through optic fibers. The NICU staff has been trained to note directly clinical events, main artefacts and therapeutic changes. The hospital local area network (LAN) enables remote monitoring survey. RESULTS Continuous EEG (CEEG)-SEP monitoring was performed in 44 patients. Problems of needle detachment were seldomly encountered, thanks to the use of a sterile plastic dressing, which covers needles. We never had infection or skin lesions due to needles or the electrical stimulator. The frequent administration of sedative at high doses prevented us from having a clinically valuable EEG in several cases but SEPs were always monitorable, independently of the level of EEG suppression. The diagnosis of seizures and non-epileptic status was based on raw EEG, while quantitative EEG (QEEG) was used to quantify ictal activity as a guide to treatment. CONCLUSIONS EEG and EP waveforms collected in NICU were of comparable quality to routine clinical measurements and contained the same clinical information. A continuous SEP monitoring in a comatose and sedated patient in NICU is not technically more difficult and potentially less useful than in operating room. This monitoring appears to be feasible provided the observance of some requirement regarding setting, electrodes, montages, personnel integration, consulting and software.

Prognostic value of somatosensory evoked potentials in comatose children: a systematic literature review

PurposeTo review the predictive powers of SEPs in comatose children after acute brain injury.MethodsMEDLINE, EMBASE, OVID, ISI Web of Knowledge, BIOMED Central and the Cochrane Library (1981–2007) were searched. First, predictive values were calculated for each primary study. Second, we analysed effects of different factors on the SEP diagnostic odds ratio by meta-regression. Third, we compared SEP predictive values in children and in adults.ResultsWe selected 14 studies covering 732 patients; analysis was conducted in 11, while the other 3 were used for simple qualitative examination. In individual papers, the presence of SEP predicted favourable outcomes as shown by the area under both sROC curves being 0.958. The same value was shown by SEP absence for predicting unfavourable outcomes. All covariates showed no significant effects on diagnostic accuracy, but only a slight non-significant trend. For SEP grading, a simple sub-group analysis showed a high predictive value for non-awakening for absence of SEPs (PPV 97.0%) and a high prognostic power to predict awakening for normal SEPs (PPV 92.2%). Pathological SEPs did not show reliable predictivity. In children, the presence of SEPs showed a high prognostic power similar to that in adults.ConclusionThis study supports the use of SEPs in the integrated process of outcome prediction after acute brain injury in children. Caution is recommended in predicting unfavourable outcomes in patients with an absence of SEPs in both TBI and HIE comas. Future studies are needed to resolve the issue of the effect of aetiology and age on SEPs predictive power.

Anti-ganglioside antibodies and elevated CSF IgG levels in Guillain-Barré syndrome

Anti‐ganglioside antibody production and dysfunction of blood‐cerebrospinal fluid (CSF) barrier (BCB) are frequent findings in dysimmune neuropathy patients, whereas intrathecal synthesis of immunoglobulins is still a matter of debate. We examined the CSF, immunological and electrophysiological characteristics from a cohort of patients with Guillain‐Barré syndrome (GBS) and chronic inflammatory demyelinating polyneuropathy (CIDP), and from patients with other neurological diseases as control. Thirty‐eight percent of GBS patients and 28% of CIDP patients had detectable serum titers of anti‐ganglioside antibodies, which were associated with a high incidence of motor conduction block and increased F wave latencies. In GBS patients, but not in CIDP or control patients, there was an association between anti‐ganglioside antibodies and increased CSF immunoglobulin‐G (IgG) levels as determined by the IgG index. However, none of the GBS patients had CSF oligoclonal bands (OBs) or indications of intrathecal anti‐ganglioside antibody synthesis. The possibility of an abnormal CSF concentration of immunoglobulins from serum through dysfunctional BCB or damaged nerve roots, and the role of serum anti‐ganglioside reactivity in this process are discussed.

Single electroencephalographic patterns as specific and time-dependent indicators of good and poor outcome after cardiac arrest

OBJECTIVE To evaluate the prognostic value of single EEG patterns recorded at various time-frames in postanoxic comatose patients. METHODS This retrospective study included 30-min EEGs, classified according to the definitions of continuity of background activity given by the American Clinical Neurophysiology Society. Isoelectric pattern was distinguished from other suppressed activities. Epileptiform patterns were considered separately. Outcome was dichotomised based on recovery of consciousness as good (Glasgow Outcome Scale [GOS] 3-5) or poor (GOS 1-2). RESULTS We analysed 211 EEGs, categorised according to time since cardiac arrest (within 12h and around 24, 48 and 72h). In each time-frame we observed at least one EEG pattern which was 100% specific to poor or good outcome: at 12h continuous and nearly continuous patterns predicted good outcome and isoelectric pattern poor outcome; at 24h isoelectric and burst-suppression predicted poor outcome; at 48 and 72h isoelectric, burst-suppression and suppression (2-10μV) patterns predicted poor outcome. CONCLUSIONS The prognostic value of single EEG patterns, defined according to continuity and voltage of background activity, changes until 48-72h after cardiac arrest and in each time-frame there is at least one pattern which accurately predicts good or poor outcome. SIGNIFICANCE Standard EEG can provide time-dependent reliable indicators of good and poor outcome throughout the first 48-72h after cardiac arrest.

Evoked potentials in the ICU

Summary The most informative neurophysiological techniques available in the neurosurgical intensive care unit are electroencephalograph and somatosensory evoked potentials. Such tools, which give an evaluation of cerebral function in comatose patients, support clinical evaluation and are complementary to neuroimaging. They serve both diagnostic/prognostic and monitoring purposes. While for the former, discontinuous monitoring is sufficient, for the latter, to obtain increased clinical impact, continuous monitoring is necessary. To perform and interpret these examinations in the neurosurgical intensive care unit, both the technician and the neurophysiologist need specific training in the intensive care field. There is sufficient evidence to show that somatosensory evoked potentials are the best single indicator of early prognosis in traumatic and hypoxic‐ischaemic coma compared to the Glasgow Coma Score, computed tomography scan and electroencephalograph. Indeed, somatosensory evoked potentials should always be combined with clinical examination to determine the prognosis of coma. Despite widespread use of somatosensory evoked potentials and their prognostic utility in acute brain injury, few studies exist on continuous somatosensory evoked potential monitoring in the intensive care unit. We carried out a pilot study of continuous electroencephalograph‐somatosensory evoked potential monitoring in the neurosurgical intensive care unit (traumatic brain injury and intracranial haemorrhage, Glasgow Coma Score <9, intracranial pressure monitoring). All patients stable from a clinical and computed tomography scan point of view showed no significant somatosensory evoked potential modifications, while in the case of clinical deterioration (23%), somatosensory evoked potentials always showed significant modifications. While somatosensory evoked potentials correlated with short‐term outcome, intracranial pressure showed a poor correlation. We believe neurophysiological monitoring is an ideal complement to the other parameters monitored in the neurosurgical intensive care unit. Whereas intracranial pressure is simply a pressure index, electroencephalograph‐somatosensory evoked potential monitoring reflects to what extent cerebral parenchyma still remains metabolically active during acute brain injury.

Neurophysiological prediction of neurological good and poor outcome in post‐anoxic coma

Investigation of the utility of association between electroencephalogram (EEG) and somatosensory‐evoked potentials (SEPs) for the prediction of neurological outcome in comatose patients resuscitated after cardiac arrest (CA) treated with therapeutic hypothermia, according to different recording times after CA.

Electric and CO2 laser SEPs in a patient with asymptomatic syringomyelia

We recorded electrically stimulated somatosensory evoked potentials (electric SEPs) and pain-related SEPs following CO2 laser stimulation (CO2 laser SEPs) from a 17-year-old patient affected by myotonic dystrophy whose MRI disclosed a large syrinx extending from spinal level C2 to S3. Careful clinical and electromyographic examinations revealed no motor or sensory disturbances, apart from myotonia. The only abnormality noted in median and ulnar nerve short-latency electric SEPs (recorded with a non-cephalic reference electrode) was the absence of cervical component N13, the other SEP responses (N9, N10, N11, P14, N20) being normal. The cutaneous pain threshold and CO2 laser SEPs (both obtained by a CO2 laser beam applied to the back of the hand) were normal. Thus cervical component N13 appears to be highly sensitive to the effects of central cord lesions, even when these are asymptomatic.

Fatigue in primary biliary cirrhosis: a possible role of comorbidities.

Background and aims Fatigue is considered to be a specific manifestation of primary biliary cirrhosis (PBC). Recent reports have, however, questioned these findings. Considering the high rate of comorbidities in PBC patients and the fact that fatigue is a multifactorial symptom, we hypothesized that it might also be due to nonhepatic causes. Our aim was to evaluate fatigue in PBC patients and its relationship with comorbidities and depression. Methods We enroled 49 Italian PBC patients (44 women; mean age: 58.9 years, range: 21–73 years) and 30 matched healthy controls, who completed the Fatigue Impact Scale (FIS), Modified FIS (MFIS), Fatigue Severity Score (FSS) and Rand Medical Outcomes Study Depression Screener. Comorbidities and several clinical and biochemical data were investigated. Linear regression, analysis of variance and post-hoc analysis were applied. Results Fatigue was higher in patients than in controls (FIS: 33 vs. 24; MFIS: 24 vs. 14; FSS: 3.3 vs. 1.9). Physical domain was significantly different in all the three questionnaires (FIS: P=0.05; MFIS: P=0.002; FSS: P=0.0002). Comorbidities (38% of patients) were independently associated with higher fatigue scores (FIS: 45; MFIS: 32; FSS: 3.3). Depressed patients (30%) were more fatigued, even if not always significantly (FIS: 43; MFIS: 29; FSS: 3.5), than controls and patients with no depression. Patients without comorbidities or depression (51%) did not have higher fatigue than controls (FIS: 20; MFIS: 17; FSS: 2.4). Conclusions Fatigue in patients with PBC was higher, but not always significantly, than in healthy controls. Comorbidities and depression might have played a role in its pathogenesis. Our data arouse doubts about the specificity of fatigue in PBC and the pathogenetic role of liver impairment.