Neurophysiological monitoring in adult and pediatric intensive care

Clinical neurophysiology is both an extension of clinical examination and an integration of neuroimaging. It plays a role in diagnosis, prognosis and monitoring in the Intensive Care Unit (ICU). Electroencephalography (EEG) and somatosensory evoked potentials (SEPs) are the most informative neurophysiological tests. Both have a major prognostic role in the hypoxic-ischemic encephalopathy and traumatic brain injury (TBI). In the former the absence of bilateral cortical SEPs has an unfavorable prognostic significance of 100%, whereas bilateral normal SEPs has uncertain prognostic value. In TBI these SEP patterns have high early prognostic value for both bad and good outcome. Continuous EEG monitoring is indicated for diagnosis and treatment of non convulsive seizures and status epilepticus (NCSE), whereas SEPs are more able to indicate the occurrence of neurological deterioration. In our opinion EEG-SEP monitoring is also valuable for interpretation and management of ICP trends, contributing to optimise treatment in a single patient. The EEG seems to have the same prognostic utility in pediatric as in adult ICU. Recent reviews supported the use of SEPs in the integrated process of outcome prediction after acute brain injury in children. However differences in interpretation are needed and the issue is whether it is possible to establish an age limit over which the prediction of SEPs is similar to that in adults. There are only a few studies of seizure prevalence in pediatric ICU. The variability of frequency of NCSE in comatose children is high as in adults and, similar to the adult, remains unclear the impact on outcome.

Continuous EEG-SEP monitoring in severe brain injury

AIMS

To monitor acute brain injury in the neurological intensive care unit (NICU), we used EEG and somatosensory evoked potentials (SEP) in combination to achieve more accuracy in detecting brain function deterioration.

METHODS

Sixty-eight patients (head trauma and intracranial hemorrhage; GCS<9) were monitored with continuous EEG-SEP and intracranial pressure monitoring (ICP).

RESULTS

Fifty-five patients were considered "stable" or improving, considering the GCS and CT scan: in this group, SEP didn't show significant changes. Thirteen patients showed neurological deteriorations and, in all patients, cortical SEP showed significant alterations (amplitude decrease>50% often till complete disappearance). SEP deterioration anticipated ICP increase in 30%, was contemporary in 38%, and followed ICP increase in 23%. Considering SEP and ICP in relation to clinical course, all patients but one with ICP less than 20 mmHg were stable, while the three patients with ICP greater than 40 mmHg all died. Among the 26 patients with ICP of 20-40 mmHg, 17 were stable, while nine showed clinical and neurophysiological deterioration. Thus, there is a range of ICP values (20-40 mmHg) were ICP is scarcely indicative of clinical deterioration, rather it is the SEP changes that identify brain function deterioration. Therefore, SEP have a twofold interest with respect to ICP: their changes can precede an ICP increase and they can constitute a complementary tool to interpret ICP trends. It has been very important to associate SEP and EEG: about 60% of our patients were deeply sedated and, because of their relative insensitivity to anesthetics, only SEP allowed us to monitor brain damage evolution when EEG was scarcely valuable.

CONCLUSIONS

We observed 3% of nonconvulsive status epilepticus compared to 18% of neurological deterioration. If the aim of neurophysiological monitoring is to "detect and protect", it may not be limited to detecting seizures, rather it should be able to identify brain deterioration, so we propose the combined monitoring of EEG with SEP.

Transient post-traumatic locked-in syndrome: a case report and a literature review

INTRODUCTION

Post-traumatic locked-in syndrome may be particularly difficult to recognize, especially when it follows a state of coma and presents the clinical feature of a "total" locked-in syndrome.

PATIENT AND METHODS

A 56-year-old male with a closed head injury was admitted in intensive care unit (ICU) with GCS=4 (V1, M2, E1). Computed tomography (CT) scan disclosed a limited subarachnoid haemorrhage in the sylvian region without any brain oedema or ventricular shift. The GCS did not change until day 6. At the same time EEG showed a reactivity to acoustic stimuli consisting in the paradoxical appearance of a posterior rhythm in alpha range (10-12c/s), blocked by passive eye opening. Early cortical components (N20-P25) of somatosensory evoked potentials were normal on both hemispheres; middle components were also clearly evident. Magnetic resonance imaging of the brain showed both diffuse and midbrain axonal injuries, particularly in a strategic lesion involving both cerebral peduncles. Event related potentials showed N2 and P3 components to stimulation by rare tones.

CONCLUSIONS

A comprehensive multimodal neurophysiological approach, using the more informative tests and the proper time of recording, should be included in protocols for patients with severe head trauma, in order to establish the actual patient's clinical state and to avoid that a locked-in syndrome state be mistaken for prolonged coma, vegetative state, minimally conscious state or akinetic mutism. Neurophysiological evaluation before discharge from ICU can be a baseline evaluation useful for the follow-up of low-responsive patients in the neuro-rehabilitation unit.

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.

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.

Anoxic-ischemic alpha coma: prognostic significance of the incomplete variant

The prognostic significance of post-anoxic-ischemic alpha coma (AC) is controversial. We recorded somatosensory evoked potentials (SEPs) and performed serial electroencephalography (EEG) in a 60-year-old woman in coma after cardiac arrest. The first EEG was recorded after 48 hours (GCS=5; E1-V1-M3); brain-stem reflexes were preserved. The EEG pattern showed monotonous alpha frequencies (10-11 Hz) with posterior predominance; acoustic and noxious stimuli evoked EEG reactivity. Early cortical SEPs (72 h) were normal. On the fifth day (GCS=8; E4-V1-M3), the EEG alpha pattern was replaced by a diffuse delta activity; rhythmic theta changes appeared spontaneously or in response to stimuli. The patient regained consciousness on the tenth day and EEG showed posterior theta activity (6-7 c/s) partially reactive to stimuli. At the 6-month follow-up, cognitive evaluation showed mild dementia. Recent studies identified two forms of AC. Patients with complete AC have an outcome that is almost invariably poor. Conversely, incomplete AC (posteriorly accentuated alpha frequency, reactive and with SEPs mostly normal) reflects a less severe degree of anoxic-ischemic encephalopathy. The case we report should be classified, according to the SEPs and EEG features, as incomplete AC. The fact that the patient has regained consciousness, even if with residual cognitive impairment, confirms the need to distinguish this variant from complete AC.

Idiopatic spinal cord herniation: a treatable cause of Brown-Séquard syndrome

We report two cases of thoracic idiopathic spinal cord herniation (ISCH) focusing on the peculiar diagnostic and therapeutic issues posed by this rare disorder. In particular MR evaluation of CSF dynamic with a 2D PC cine-MR technique and demonstration of progressive cord herniation on consecutive MR examinations allowed insight on the differential diagnosis and pathophysiological mechanisms of ISCH.

Assessment of trigeminal small-fiber function: brain and reflex responses evoked by CO2-laser stimulation

Laser pulses selectively excite mechano-thermal nociceptors and evoke brain potentials that may reveal small-fiber dysfunction. We applied CO2-laser pulses to the perioral and supraorbital regions and recorded the scalp laser-evoked potentials (LEPs) and reflex responses in the orbicularis oculi, masticatory, and neck muscles in 30 controls and 10 patients with facial sensory disturbances. Low-intensity pulses readily evoked scalp potentials consisting of a negative component with a latency of 165 ms followed by a positive component at 250 ms. In vertex recordings, the amplitude of LEPs exceeded 30 microV. Although only high-intensity pulses evoked reflex responses, some subjects showed--even to low-intensity pulses--an orbicularis oculi (blink-like) response that markedly contaminated the scalp recording. Scalp LEPs were abnormal in patients with hypalgesia and normal trigeminal reflexes and normal in patients with normal pain sensitivity and abnormal trigeminal reflexes. Possibly because of the high receptor density in this area and the short conduction distance, laser stimulation of the trigeminal territory yields low-threshold and large LEPs, which are useful for detecting dysfunction in peripheral and central pain pathways.

Fatal herpesvirus 6 encephalitis after unrelated bone marrow transplant

A complex pattern of neurological dysfunctions with generalized seizures and visual allucinations, but without focal signs, suddenly arose 20 days after an unrelated bone marrow transplant for chronic myelogenous leukemia (CML) in a 13-year-old girl, accompanied by signs of acute skin graft-versus-host disease (GVHD). Magnetic resonance imaging (MRI) revealed multiple bilateral foci of signal abnormalities, which were exclusively localized in the grey matter, sparing the white. Extensive microbiological and virological assays of cerebrospinal fluid (CSF) allowed the identification of HHV-6, variant A, DNA. Further progression of both neurological alterations and of skin and gut GVHD led to a fatal outcome 2 weeks later. A retrospective analysis of both the recipient and donor mononuclear cell suspensions supported the hypothesis that HHV-6 had been acquired from the donor with the bone marrow graft. This report suggests a pathogenetic role of HHV-6 in viral encephalitis in immunocompromised bone marrow transplant (BMT) recipients, and its possible association with GVHD.

Familial AL-amyloidosis in three Italian siblings

BACKGROUND AND METHODS

Familial occurrence of immunoglobulin-related (AL) amyloidosis has occasionally been reported. In this work we describe the concomitance of systemic amyloidosis and monoclonal gammopathy (one case of Waldenström's macroglobulinemia and two cases without multiple myeloma or related diseases) in three Italian siblings, two males and one female.

RESULTS AND CONCLUSIONS

All of them showed a common pattern of polyneuropathy to different degrees; two presented a sicca syndrome and one also suffered from nephropathy. Two of them showed the same HLA typing with the same light chain type (k), but had different presenting symptoms. Polyneuropathy and a history of peptic disease in two cases was suggestive of type III familial amyloidotic polyneuropathy (FAP) occurring in the setting of a familial monoclonal component. However, immunohistochemical studies on different tissue specimens using anti-apolipoprotein A1 and anti-transthyretin antibodies were negative. Further screening of DNA samples for transthyretin (TTR) gene mutations was also negative. Clinical and laboratory investigations ruled out reactive or senile amyloidosis and immunohistochemical studies with anti-light chain antibodies on amyloidotic tissue specimens were positive. As a consequence, this family represents a new case of familial AL-amyloidosis.

[99mTc HMPAO (technetium 99m-hexamethylpropyleneamine oxime) angioscintigraphy in the diagnosis of brain death]

The diagnosis of brain death has great importance for the social and medical purposes, such as organs transplantation, and is based on clinical examination and EEG records. We report two doubtful cases of brain death in whom the 99mTc HMPAO scintigraphy was used to confirm the complete absence of cerebral perfusion.

"Epilepsia partialis continua" due to multifocal encephalitis: favourable outcome after immunoglobulin treatment

The case of a young woman with EPCK is described in which neoplastic and vascular disorders were excluded. Supported by EEG and PET, EPCK was imputed to multifocal encephalitis notwithstanding serological and CSF negativity. Cerebral biopsy confirmed the inflammatory nature of the affection, although the etiologic agent was not identified. High dose intravenous immunoglobulin therapy was followed by the prompt disappearance of EPCK and the remission of the other neurological deficits.

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.

Monitoring of somatosensory evoked potentials during carotid endarterectomy

Somatosensory 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 (less than 25 mmHg) 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.

Transmission times from cutaneous and mixed nerves of lower limbs

In each of 10 normal subjects, P28 and N31 far-field components as well as the cortical N37 and P40 waves were identified for both Sural (SN) and Posterior Tibial nerve (PTN) stimulation at the ankle. Peripheral conduction velocity along the popliteal fossa-L3 segment and spinal transmission velocity over the L3-Cv2 segment did not differ significantly for the two nerves. The average latencies of N37 and P40 to stimulation of PTN were 2.55 and 3.65 msec shorter than corresponding latencies from SN. If we consider the P28-N37 and P28-P40 intervals as central transmission times, only the former approaches upper limb CCT values closely enough to support the analogy between median nerve N20 and PTN N37. At the intracranial level, the P28-N37 inter-peak latency was significantly shorter for PTN than SN. The P28 component is generally attributed to lemniscal activity. Thus, the discrepancy in afferent transmission times from the leg's mixed and sensory nerves would appear to take place at a level that is supralemniscal but subcortical.

Anesthetic induction with thiopental: its effect on scalp topography of median nerve somatosensory evoked potentials

The effects on median nerve somatosensory evoked potentials (SEPs) of analgesic doses of fentanyl, meperidine or morphine and of sodium thiopental (STP) anesthesia (4 mg/kg) were tested in 36 surgical patients. We also explored changes in SEP components as a function of their scalp location. Before and after medication, responses were recorded from the scalp overlying the parietal cortex (ipsi- and contralateral to the stimulated arm) and the precentral (contralateral) cortex. None of the three opiates affected SEP latencies or amplitudes. The barbiturate increased the amplitudes of subcortical and early cortical components (N18, N20, P22, P25), whose latencies, however, were not significantly modified. The effect of STP on later SEP cortical components depended on their scalp topography: parietal N33 and P45 underwent significant changes in both latency and amplitude, whereas precentral N30 showed a significant amplitude increase only. Thiopental anesthesia produces clearer short-latency SEP recordings, from both parietal (components N20-P25) and precentral (P22, N30) areas.