Recommendations for the use of electroencephalography and evoked potentials in comatose patients.

Predicting the outcome of a comatose or poorly responsive patient is a major issue for intensive care unit teams, in order to give the most accurate information to the family and to choose the best therapeutic option. However, determining the level of cortical activity in patients with disorders of consciousness is a real challenge. Reliable criteria are required to help clinicians in the decision-making process, especially in the acute phase of coma.

Neurophysiological assessment of brain dysfunction in critically ill patients: an update.

The aim of this review was to provide up-to-date information about the usefulness of clinical neurophysiology testing in the management of critically ill patients. Evoked potentials (EPs) and electroencephalogram (EEG) are non-invasive clinical neurophysiology tools that allow an objective assessment of the central nervous system's function at the bedside in intensive care unit (ICU). These tests are quite useful in diagnosing cerebral complications, and establishing the vital and functional prognosis in ICU.

Neurophysiological testing in neurocritical care.

Purpose Of Review: To summarize a consensus of European authorities about the applications of clinical neurophysiology in the ICU and, particularly, for a clinically useful management of individual patients.

Recent Findings: Clinical neurophysiology is useful for diagnosis (epilepsy, brain death, and neuromuscular disorders), prognosis (anoxic ischemic encephalopathy, head trauma, and neurological disturbances of metabolic and toxic origin), and follow-up. The prognostic significance of each test varies as a function of coma etiology.

Neurophysiological investigations of hepatic encephalopathy: ISHEN practice guidelines.

By studying neuronal activity through neuronal electrogenesis, neurophysiological investigations provide a functional assessment of the nervous system and, therefore, has been used for quantitative assessment and follow-up of hepatic encephalopathy (HE). The different clinical neurophysiological approaches can be classified depending on the function to explore and their sensitivity to HE. The reliable techniques are those that reflect cortical function, i.

Neurophysiological patterns of vegetative and minimally conscious states.

This paper reviews the possible usefulness of electroencephalogram (EEG) and evoked potential (EP) recording in vegetative and poorly-responsive patients. There is a marked inter-individual EEG and EP variability, which reflects the state heterogeneity. Four clinical applications are described: (1) the identification of primary midbrain dysfunction--and, therefore, a possible reversibility--in post-traumatic states; (2) the identification of the permeability of sensory channels; (3) quantitative follow-up; and (4) individual assessment of cognitive functions and/or consciousness.

Evoked potentials in severe brain injury.

Three-modality evoked potentials (EPs) have been used for several years in association with the electroencephalogram (EEG) as a diagnostic and prognostic tool in acute traumatic or nontraumatic coma. In 1993 we proposed to combine these in two indices: the index of global cortical function (IGCF) and the index of brain-stem conduction (IBSC). Four EP patterns based on both indices emerge at the acute stage of severe head trauma.

Involuntary orientation of attention to unattended deviant nociceptive stimuli is modulated by concomitant visual task difficulty. Evidence from laser evoked potentials.

Objective: Recent laser evoked potential (LEP) studies showed that unattended rare intensity-deviant nociceptive stimuli enhance the LEP vertex positivity P2 ('P400 effect'). It was hypothesized to reflect an involuntary switch of attention to nociceptive events. If true the P400 effect (1) should be produced when attention is focused on a task in another sensory modality (primary task), and (2) should be modulated by the primary task difficulty.

Propofol infusion syndrome associated with short-term large-dose infusion during surgical anesthesia in an adult.

In this case report we describe a case of propofol infusion syndrome in an adult after a short-term infusion of large-dose propofol during a neurosurgical procedure. Large-dose propofol (9 mg.kg(-1).

Bilateral carotid-cavernous fistula following head trauma: Possible worsening of brain injury following balloon catheter occlusion?

A 68-year-old woman developed right pulsatile exophtalmos in the early course of facial and head trauma. Investigations by visual evoked potentials suggested the presence of a bilateral prechiasmatic lesion. Intraocular pressure rapidly increased and a high-flow carotid-cavernous fistula was evident at carotid angiography.

Comparison of clinical, magnetic resonance and evoked potentials data in a case of valproic-acid-related hyperammonemic coma.

Magnetic resonance (MR) multimodality evoked potentials (MEPs) and clinical findings were correlated in a 47-year-old epileptic man in whom parenteral valproic acid (VPA) therapy induced severe comatose hyperammonemic encephalopathy without biological signs of hepatotoxicity (or hepatocytic dysfunction). Although the plasma VPA level remained within a normal therapeutic range, the ammoniemia increased to a toxic peak level at 411 micromol/l 24 h after symptom onset, requiring VPA therapy discontinuation. Brain MR monitoring demonstrated early cytotoxic edema evolving into delayed vasogenic edema and final brain atrophy.

Electroencephalography (EEG) and somatosensory evoked potentials (SEP) to prevent cerebral ischaemia in the operating room.

We review the principal aspects of EEG and SEP to detect and prevent cerebral ischaemia in the operating room during interventions at risk. EEG and SEP are variables that indirectly reflect cerebral blood flow (CBF) provided that anaesthetic regimen, body temperature, and arterial blood pressure of the patient are stable. When CBF decreases and reaches the functional threshold, slowing and/or attenuation of EEG occurs while the amplitude and the latency of cortical SEP are, respectively decreased and lengthened.

Exogenous and endogenous components of ultralate (C-fibre) evoked potentials following CO2 laser stimuli to tiny skin surface areas in healthy subjects.

CO2 laser stimulation of tiny skin surface areas on the hand dorsum generate ultralate laser evoked potentials (LEPs) with a major positivity maximal at the vertex at a latency of about 1 s. These potentials follow selective and direct activation of C-fibres in the superficial layers of the skin. To identify the endogenous P3 component in ultralate LEPs, we used a 2-stimulus oddball paradigm (20% probability of targets).

Nociceptive processing in the human brain of infrequent task-relevant and task-irrelevant noxious stimuli. A study with event-related potentials evoked by CO2 laser radiant heat stimuli.

Laser evoked potentials (LEPs) are nociceptive-related brain responses to activation of cutaneous nociceptors by laser radiant heat stimuli. We previously showed that LEP amplitude during the P2 period (approximately 400 ms) was increased by rare noxious stimuli, inside and outside the focus of spatial attention. It was postulated that this effect reflected a P3a response indexing an involuntary shift of attention.

Electrophysiological correlates of attentional orientation in humans to strong intensity deviant nociceptive stimuli, inside and outside the focus of spatial attention.

Laser evoked potentials (LEPs) are electrical brain responses to nociceptive heat stimuli. In a recent study [Legrain, V., Guérit, J.

Fomepizole therapy for reversal of visual impairment after methanol poisoning: a case documented by visual evoked potentials investigation.

Purpose: To illustrate the safety and efficacy of fomepizole in a case of methanol poisoning with initial visual impairment.

Design: Interventional case report.

Methods: A 60-year-old man was admitted with blurred vision and changes in color perception 18 hours after ingesting 100 ml methanol.

State-of-the-art of neuromonitoring for prevention of immediate and delayed paraplegia in thoracic and thoracoabdominal aorta surgery.

Background: The prevention of immediate and delayed paraplegia after thoracoabdominal aorta surgery relies on hemodynamic maneuvers (aimed at restoration of an adequate spinal cord perfusion pressure) and cytoprotective measures (hypothermia, drugs).

Methods: The indications for implementing these measures can be provided by motor-evoked potential (MEP) or somatosensory-evoked potential (SEP) monitoring.

Results: Intraoperative interactions between the surgeon and the neurophysiologist can be described by algorithms to be applied in the presence or absence of intraoperative MEP or SEP changes.

Attentional modulation of the nociceptive processing into the human brain: selective spatial attention, probability of stimulus occurrence, and target detection effects on laser evoked potentials.

Laser evoked potentials (LEPs) are brain responses to activation of skin nociceptors by laser heat stimuli. LEPs consist of three components: N1, N2, and P2. Previous reports have suggested that in contrast to earlier activities (N1), LEPs responses after 230-250 ms (N2-P2) are modulated by attention to painful laser stimuli.

Predicting spinal cord ischemia before endovascular thoracoabdominal aneurysm repair: monitoring somatosensory evoked potentials.

Purpose: To present a method of predicting spinal cord ischemia before deployment of an endograft in the thoracoabdominal aorta.

Case Report: A 76-year-old high-risk patient presented with an aneurysm of the distal thoracic and proximal abdominal aorta. An endovascular treatment was scheduled, but before deployment of the endograft, occlusion of the aneurysmal segment was monitored for 15 minutes using multilevel somatosensory evoked potentials (SEP).