G. Bryan Young

EEG morphology of partial epileptic seizures

We studied the EEG features of partial seizures in 66 patients. An EEG evolution (morphology and/or frequency change) characterised 79% of attacks: 92% of 48 events with clinical features, but only 44% of 18 subclinical seizures. Aside from attenuation which initiated 7 seizures (11%), 31 (47%) began with sinusoidal waves, 25 (39%) with repetitive epileptiform potentials, and 10 (15%) with both phenomena. Metamorphosis between these forms occurred in about 1/3 of seizures beginning with either form alone. A wave form change occurred in 44% of clinical attacks but only 7% of subclinical seizures. Spikes and sharp waves were the most common repetitive epileptiform potentials encountered. Repetition rate of phenomena at onset usually lay in the theta or delta range except for a few with high frequency sinusoidal waves. Further ictal EEG progression was more likely to occur if a mixed frequency change or frequency increase characterised early evolution.

Detecting Awareness in the Vegetative State: Electroencephalographic Evidence for Attempted Movements to Command

Patients in the Vegetative State (VS) do not produce overt motor behavior to command and are therefore considered to be unaware of themselves and of their environments. However, we recently showed that high-density electroencephalography (EEG) can be used to detect covert command-following in some VS patients. Due to its portability and inexpensiveness, EEG assessments of awareness have the potential to contribute to a standard clinical protocol, thus improving diagnostic accuracy. However, this technique requires refinement and optimization if it is to be used widely as a clinical tool. We asked a patient who had been repeatedly diagnosed as VS for 12-years to try to move his left and right hands, between periods of rest, while EEG was recorded from four scalp electrodes. We identified appropriate and statistically reliable modulations of sensorimotor beta rhythms following commands to try to move, which could be significantly classified at a single-trial level. These reliable effects indicate that the patient attempted to follow the commands, and was therefore aware, but was unable to execute an overtly discernable action. The cognitive demands of this novel task are lower than those used previously and, crucially, allow for awareness to be determined on the basis of a 20-minute EEG recording made with only four electrodes. This approach makes EEG assessments of awareness clinically viable, and therefore has potential for inclusion in a standard assessment of awareness in the VS.

Effects of morphine on the electroencephalograms of neonates: a prospective, observational study

OBJECTIVESnAlthough opiates have been reported to profoundly alter the EEG and cause seizures in full-term and premature newborn babies, no prospective study has systematically studied the effects of morphine on the EEG of normal neonates.nnnMETHODSnA prospective observational study was conducted on 20 neurologically and metabolically normal newborn babies of > or =26 weeks post-conceptional age, with EEG recordings performed while on and off morphine infusions.nnnRESULTSnThe recordings performed while the babies were on morphine were all abnormal; the principal abnormalities consisted of prolonged periods of electrical quiescence (PPEQs) and excessive interictal epileptiform activity. After the morphine was discontinued, the PPEQs resolved and the EEG background rhythms were normal for age, but 5 continued to have excessive sharp transients. All babies did well clinically and did not require anti-epileptic drug therapy.nnnCONCLUSIONSnMorphine produces a profound, largely reversible alteration of all neonatal EEGs at various post-conceptional ages. The study has implications for caution in formulating conclusions regarding the clinical significance of EEGs of critically ill neonates on morphine infusions.

A comparison of subdermal wire electrodes with collodion-applied disk electrodes in long-term EEG recordings in ICU.

OBJECTIVEnTo compare long-term electroencephalographic (EEG) recordings of standard collodion-applied scalp disk electrodes (SDEs) with newly developed subdermal wire electrodes (SWEs) in comatose intensive care unit (ICU) patients.nnnMETHODSnTen comatose ICU patients had simultaneous recordings from 8 active SDEs and 8 active SWE for >24 h. The timing and number of 60 Hz and other electrode artifacts were compared for each set of electrodes by an EEGer who read the recordings in a blinded manner.nnnRESULTSnSixty Hertz artifact was seen in 16 of 80 SDE and one of 80 SWEs within the first 6 h (P=0.0002). Large, persistent artifacts occurred in 30/80 SDE and 8 of 80 SWE (P=0.0001). Motion artifact with chest physiotherapy was more common in SWEs.nnnCONCLUSIONSnSWE are less susceptible to artifacts and are more suitable for the long-term EEG monitoring in ICU.nnnSIGNIFICANCEnThis is the first controlled study that demonstrates the superiority of SWEs compared to SDEs in an ICU population.

Functional MRI study of the primary somatosensory cortex in comatose survivors of cardiac arrest

It is difficult to assess cerebral function in comatose patients. Because earlier functional neuroimaging studies demonstrate associations between cerebral metabolism and levels of consciousness, fMRI in comatose survivors of cardiac arrest could provide further insight into cerebral function during coma. Using fMRI, cerebral activation to somatosensory stimulation to the palm of the hand was measured in 19 comatose survivors of cardiac arrest and in 10 healthy control subjects and was compared to somatosensory-evoked potential (SSEP) testing of the median nerve. Changes in the blood oxygenation-level dependent signal (BOLD) in the primary somatosensory cortex (S1) contralateral to the stimulated hand were quantified. Clinical outcome was assessed using the Glasgow Outcome Scale (GOS) and the modified Rankin Scale at 3 months post-cardiac arrest. Five out of 19 patients were alive at 3 months. Patients who survived cardiac arrest showed greater BOLD in S1 contralateral to somatosensory stimulation of the hand compared to patients who eventually did not. Greater BOLD was also seen in S1 of patients who retained their SSEP N20 waveforms. There were also positive correlations between BOLD in S1 with both levels of consciousness and measures of outcome at 3 months. In summary, this study demonstrates that BOLD in the S1 contralateral to somatosensory stimulation of the hand varies with clinical measures of the level of consciousness during coma.

A Prospective Observational Study of Seizures After Cardiac Surgery Using Continuous EEG Monitoring

IntroductionRecently, there have been several retrospective reports suggesting an increased frequency in seizures after cardiopulmonary bypass, associated with increased patient morbidity. We sought to prospectively investigate the incidence of electrographic seizures without clear convulsive clinical correlates and subsequent neurologic injury following cardiac surgery.MethodsThis single-center, prospective, observational study used continuous subhairline electroencephalographic (cEEG) monitoring in the intensive care unit following routine cardiac surgery, ranging from coronary bypass surgery to complex aortic arch reconstruction. The primary outcome was the proportion of patients developing postoperative seizures, as confirmed on cEEG monitoring. Secondary outcomes included neurologic injury, post-operative complications, mortality, and ICU and hospital lengths of stay.Results101 consenting patients were included and 3 patients had seizures (2 focal and convulsive, 1 generalized and electrographic). All three patients with seizures were ≥65xa0years old, had “open-chamber” procedures, and had cardiopulmonary bypass times >120xa0min. One of the 3 patients with seizures was exposed to higher doses of tranexamic acid. None of the patients with seizures had permanent neurologic sequelae and all were doing well at 1-year follow-up. There was no increased morbidity or mortality in patients with seizures.ConclusionsElectrographic seizures occur infrequently after cardiac surgery and are generally associated with a good prognosis. Prophylactic cEEG monitoring is unlikely to be cost-effective in this population. (ClinicalTrials.gov Identifier: NCT01291992).

Positive Prognostication from Median-Nerve Somatosensory Evoked Cortical Potentials

BackgroundThe bilateral absence of the cortical N20 median-nerve somatosensory evoked potential (SSEP) is a strong predictor of poor outcome from coma. However, when N20s are present, accurate prognostication is challenging. Here, we investigated the potential for later SSEP components to help disambiguate outcome in these cases.MethodsIn a retrospective review of data from two intensive care units, the amplitudes and latencies of the N20, P25, and N35 components of 28 patients in coma were quantified and related to outcome at discharge from primary care (average 1-month post-injury). Only patients who had survived primary care were included in order to avoid self-fulfilling prophecies, and to focus outcome prediction on those patients with relatively present SSEPs.ResultsThe amplitudes of the N20 and N35 components (averaged across hemispheres) significantly predicted the range of outcomes beyond death. Abnormal amplitudes of the N20 and N35—as derived from a healthy control group—were significantly associated with poor outcome. The relative latencies of the cortical components were not related to outcome.ConclusionsWhile it is well documented that absent SSEPs are highly predictive of poor outcome, the current data indicate that the relative preservation (absolute amplitude) of “present” N20 and N35 SSEP components can also provide predictive value and thereby inform clinicians and families with decision-making in coma. Further prospective study will elucidate the relative contributions of etiology to the predictive power of these SSEP measures.

Clinical neurophysiology of prolonged disorders of consciousness: From diagnostic stimulation to therapeutic neuromodulation

The identification of signs of awareness in patients with prolonged disorders of consciousness (DoC) after severe brain injury is a challenging task for clinicians. Differentiating on behavioural examination the vegetative state (VS) from the minimally conscious state (MCS) can lead to a high misdiagnosis rate. Advanced neuroimaging and neurophysiological techniques can supplement clinical evaluation by providing physiological evidence of brain activity. However, an open issue remains whether these empirical results are directly or indirectly associated with covert consciousness and limitations emerge for their diagnostic application at the single-patient level. On the therapeutic side, the efficacy of both non-invasive and invasive brain stimulation/modulation trials is matter of debate. The present review provides an updated analysis of the diagnostic and prognostic impact that the different neurophysiological techniques of stimulation [including short-latency evoked potentials, long-latency event related potentials (ERPs), transcranial magnetic stimulation (TMS), TMS-EEG co-registration] offer in prolonged DoC. The results of the therapeutic stimulation techniques are also evaluated. It is concluded that TMS-EEG emerges as the most promising tool for differentiating VS from MCS whereas ERPs allow neurophysiologists to probe covert cognitive capacities of each patient. Significant behavioural improvements in prolonged DoC with brain stimulation techniques are still anecdotical and further treatment options are awaited.

Ethical considerations in functional magnetic resonance imaging research in acutely comatose patients

Determining the prognosis of comatose patients is difficult, and yet this information is vital for informing treatment decisions. While fMRI offers promise as a prognostic tool, further research is needed into its use. Weijer et al. provide the first analysis of the ethical issues surrounding such research in comatose patients.

Donation after cardiac death: enter the neurologist

www.thelancet.com/neurology Vol 11 May 2012 385 Donation after cardiac death (DCD) is the process through which donation of solid organs takes place after the heart stops (usually within 5 min of cardiac arrest). Because the permanent cessation of heartbeat satisfi es the dead donor rule, which states that donor transplantation should not kill the patient but rather that the patient be already dead, DCD procedures have been approved in many countries. During the past decade, the disparity between the number of patients waiting for a transplant and the number of organs available has increased. As such, transplantation programmes in many countries have revisited the use of organs from donors after cardiac death. Previously, most programmes relied solely on organs from donors who were brain dead. As a result, DCD has greatly boosted organ donation beyond that which occurred after the declaration of brain death or neurological determination of death. In a study reported in this issue of The Lancet Neurology, Rabinstein and colleagues have tested a neurologicallybased scoring system that should increase the accuracy of donor selection. Successful DCD requires selection of patients whose hearts are likely to stop within 1–2 h after withdrawal of life-sustaining treatment (WLST), to reduce anoxic injury that occurs during the withdrawal process and thus allow the organs to remain viable for transplantation. However, the DCD process needs substantial resources and therefore the ability to predict with reasonable certainty which patients will die within 1–2 h is key. The Wisconsin guidelines were developed by non-neurological intensive-care specialists to provide a measure of the probability of cardiac arrest within 1 h of WLST. The factors used in these guidelines include presence of spontaneous respiration after 10 min off the ventilator, body-mass index, use of vasopressors, age of the patient, use of tracheostomy versus use of endotracheal tube, and oxygen saturation after 10 min. Each of these variables was assigned a value and the aggregate score was used to predict cardiac death within 1 h of WLST. However, subsequent attempts to defi ne risk factors for early death more accurately have suggested that a reliable technique for prediction of time of death after WLST is not avaliable. Most patients who become DCD donors have severe CNS damage but are not brain dead. Although neurologists are at least one step removed from the DCD process, such professionals might be better qualifi ed than other specialists to establish the neurological factors that predict cardiac arrest after WLST in patients who have brain damage. Since the withdrawal process includes the removal of the endotracheal tube in the operating room (and hence most patients die of asphyxic cardiac arrest), the presumption is that patients who are closer to brain death and are either not able to breathe adequately or protect the airway have a higher chance of prompt cardiac arrest. Whether or not health-care providers have qualms or philosophical concerns about DCD, when it is adopted as an accepted practice, as it currently is in many countries, the improvement of the process becomes a priority. Rabinstein and colleagues report a prospective observational study that aimed to validate the use of a neurological scoring system to assess likelihood of death within 60 min after WLST. The scoring system was built on a previous retrospective study by the investigators of patients who had brain injury and underwent WLST for compassionate reasons. Rabinstein and colleagues’ study included 178 patients with heterogenous disorders, but more than 85% of them had structural brain damage (intracranial haemorrhage, ischaemic stroke, or head injury). Borrowing from the FOUR score tabulation of neurological assessment of patients in coma, four factors were statistically associated with death within 1 h of WLST: absent corneal refl exes, absent cough Donation after cardiac death: enter the neurologist