The clinical significance of sleep apnoea in workers exposed to organic solvents: implications for the diagnosis of organic solvent encephalopathy.

Among 51 patients referred for investigation of possible organic solvent encephalopathy 20 (39%) had pathological sleep apnoea [apnoea index (AI) greater than 5], compared with 5 of 16 house painters exposed to solvents (31%) who were screened for the disorder, and 1 of 18 (6%) age-matched controls. Twelve of the patients with AI greater than 5 were retested after 2 or more weeks without exposure to solvents, and showed a significant drop in AI. Likewise, significantly lower AI was seen in patients who were no longer exposed to solvents, compared with recently exposed patients. The implications of these findings for diagnostic evaluation of solvent encephalopathy and sleep apnoea are discussed.

Neuromonitoring in hypothermia and in hypothermic hypoxia.

Severe accidental hypothermia is often associated with global ischaemia due to cardiac arrest. The purpose of the present study was to evaluate whether rewarming on cardiopulmonary bypass (CPB) should be slow or as fast as possible. Pigs were cooled to 23 degrees C (rectum), subsequently followed by 1 h period of circulatory arrest, whereupon rewarming was started. Pigs were randomly allocated to 3 groups: slowly rewarmed (2 h), rapidly rewarmed (0.5 h) and a control group on CPB maintaining normothermia. EEG was continuously analyzed by means of Anesthesia-Brain-Monitor (ABM-system), which allows simultaneous monitoring of EEG, blood- and intracranial pressures, heart rate and capnogram as trend graphs. The ABM-system thus delivers a continuous on-line printout of all measured variables. Cooling resulted after about 30 min in electrocerebral inactivity (ECI) in all pigs. EEG reappeared in all animals regardless of the considerable long cardiocirculatory arrest, followed by nearly 3 hours of ECI! It would appear tempting to rewarm an accidentally cooled organism as fast as possible. The present study, however, indicate that the brain during rewarming seems to have its own speed for regeneration of the EEG. This speed showed to be slower than the steeply rising temperature during rapid rewarming. Furthermore, a too vigorous rewarming may jeopardize cerebral metabolism; 90 min after the start of rewarming the EEG had reappeared in 5 out of 8 pigs in slow group, but only in 2 out of 7 in rapidly rewarmed animals. In controls the EEG was continuously present throughout the experiments.

Brain-stem auditory evoked potentials in multiple sclerosis: the relation to VEP, SEP and CSF immunoglobulins.

One hundred patients with multiple sclerosis (MS) were analysed retrospectively with respect to investigations of brain-stem auditory evoked potentials (BAEP), pattern reversal visual evoked potentials (VEP), somatosensory evoked potentials (SEP), and cerebrospinal fluid immunoglobulins (CSF-IG). BAEP were abnormal in 42% of those with normal VEP and SEP examinations, and in 38% of patients with normal CSF-IG. The chance of obtaining at least one abnormal EP was lower in patients with normal CSF-IG than in patients with abnormal CSF. When a "dispersion ratio" was included in the criteria for BAEP abnormality, the sensitivity increased compared with conventional BAEP criteria. We recommend that BAEP should still be included in the EP test battery for patients with suspected MS.

Evoked potentials and CSF-immunoglobulins in MS: relationship to disease duration, disability, and functional status.

In 100 MS patients, BAEP and tibial SEP abnormality rates increased significantly with disease duration and clinical disability. VEP correlated non-linearly with disease duration, and median nerve SEP correlated with disability. In multifactorial analysis, however, BAEP correlated significantly only with clinical brainstem and cerebellar signs. These results suggest that evoked potentials correlate more strongly with neurological status of the functional subsystems than either overall disability or disease duration. These findings indirectly suggest that evoked potentials may be useful monitors during large therapeutical trials in MS patients.

Hyperventilation syndrome: clinical, ventilatory, and personality characteristics as observed in neurological practice.

The symptoms of the hyperventilation syndrome (HVS) are sometimes diffuse, and HVS may resemble other clinical conditions. A diagnosis of HVS was made in 25 patients referred for neurological assessment because of atypical, shortlasting, episodic complaints. The referral diagnoses varied within a wide range. A need for more indepth knowledge about this group of patients thus arose. During a provocation test with forced respiration, all patients reported symptoms similar to those during attacks. Eight patients described numbness or paraesthesias with unilateral predominance. End-tidal pCO2 levels were monitored prior to and during a forced hyperventilation test. Compared with controls, the patients had significantly decreased end-tidal pCO2 even during symptom free periods. After hyperventilation, hypocapnia followed a protracted course in the patient group. Sensory symptoms may be asymmetric and mimic focal cerebral disease. Strained respiration may be denied during spontaneous attacks. Personality characteristics were evaluated with the Minnesota Multiphasic Personality Inventory (MMPI). A mean group profile very similar to profiles reported on "pseudoepileptic" patients was found. The profile indicates a neurotic pattern where patients tend to respond to psychological stress with somatic symptoms.

Sleep apnoea and organic solvent exposure.

Fifteen patients referred for the evaluation of possible organic solvent encephalopathy were studied by clinical polysomnography. Seven had more than 30 apnoeas per night and an apnoea index of higher than 5, thus fulfilling the commonly used criteria of the sleep apnoea syndrome. Another group of eight workers exposed to trichlorethane, examined without prior knowledge of their individual symptoms, showed a significantly elevated number of sleep apnoeas compared with nine controls. The results indicate that organic solvent exposure can cause sleep apnoea.

A new syndrome: thrombocytopathia, muscle fatigue, asplenia, miosis, migraine, dyslexia and ichthyosis.

A new multifacetted syndrome inherited as an autosomal, dominant trait is described encompassing not only two hitherto undescribed hereditary defects--thrombocytopathia and asplenia--but also muscle contractile defect, migraine-like headache, miosis, dyslexia and ichthyosis. None of these defects has so far been assigned to a specific chromosome or linkage group. Further studies on the various aspects of the syndrome are in progress.

Effects of anaesthesia for caesarean section on the computerized EEG of the neonate.

The effects of anaesthetic techniques and drugs on 18 neonates born after elective Caesarean section were studied, employing computerized EEG. Three different groups, epidural, spinal and general anaesthesia, were compared with each other and with a control group after normal vaginal delivery. A new computerized EEG method, Zero Band Power Rate (ZBPR) analysis, was devised for this study and implemented together with conventional spectral EEG estimates of five frequency bands. ZBPR analysis was found to be much more sensitive than conventional spectral analyses for detecting differences between the study groups. Significant differences occurred between the general anaesthesia group and the epidural and control groups and also between the spinal group and the epidural and control groups. No significant difference was seen between the epidural group and the control group. Significant differences were attributed to the clinical use of two drugs: thiopentone in the general anaesthesia group and ephedrine in the spinal group. The effects of these drugs on the neonatal EEG were reflected in decreased ZBPR values, particularly during sleep.

"Hemicrania continua". An indomethacin responsive headache. II. Autonomic function studies.

Various autonomic parameters have been studied in two patients with "hemicrania continua", a newly described unilateral headache which is aborted by indomethacin. Striking findings were made on pupillometry: In both patients, isocoria was present when untreated. Bilateral instillation of tyramine in the conjunctival sac resulted in a late appearing anisocoria, with the smaller pupil on the symptomatic side. Indomethacin medication corrected this anomaly. These findings add further evidence to our firm belief that "hemicrania continua" differs fundamentally from chronic paroxysmal hemicrania, where such pupillometric changes are not found. There thus seem to be at least two different types of hemicranias with an absolute indomethacin effect.

The influence of click phase and rate upon latencies and latency distributions of the normal brain-stem auditory evoked potentials.

The effect of the phase of the click stimulus and its relation to the stimulus repetition rate on the brain-stem auditory evoked potentials (BAEPs) was investigated in 43 normal subjects, with condensation (C) and rarefaction (R) clicks of 10 and 50 Hz rate, using a piezoelectric headphone . The distribution of C and R latencies for component I seemed to be bimodal, probably reflecting (at least) two subcomponents in I separated by about 0.20 msec. C clicks tended to evoke the first and R clicks the second subcomponent. Condensation clicks gave significantly shorter absolute mean latencies for components I, IN, II, III, IIIN , IV and VI (10 Hz) and components IN, II, III, IIIN and IV (50 Hz). The V/I relative amplitude means were not influenced by phase, but increased with rate. Standard deviations were greatest for component IV latencies and increased only insignificantly with the higher repetition rate. A significantly smaller number of IV components was identified with R as compared to C clicks. Increasing the stimulus rate to 50 Hz detected wave IV in 12 of the 18 records where R clicks failed to identify IV with 10 Hz stimulation. The importance of the stimulus characteristics is discussed and some suggestions for clinical use of BAEP are made.

Somatosensory evoked responses as a diagnostic aid in thoracic outlet syndrome. A postoperative study.

In the present study we have recorded evoked responses in the supraclavicular fossa (Erb's point) following stimulation of the median and ulnar nerves separately on both sides, in patients with thoracic outlet syndrome. Nine out of the 13 patients showed abnormal findings in the preoperative recordings when compared to the recordings of the 20 healthy controls. The first postoperative recordings were performed two months after operation and 3 out of 9 patients with the abnormal preoperative recordings showed normalized results and in addition 2 patients, about one to two years after the operation in the second postoperative recordings. It is suggested that the Erb's point recordings may be of value not only in the diagnosis of thoracic outlet syndrome but also that these recordings are possibly suitable for postoperative follow-up of this disorder.

Benign familial myoclonus-like movements, partly of early onset.

A family with benign, myoclonus-like involuntary movements of early onset has previously been described by us (Refsum and Sjaastad, 1972, 1973; Sjaastad, 1981). In the present communication electrographical investigations carried out in the proband and his sister will be reported. Additional information will also be reported regarding onset of the abnormal movements.

Somatosensory evoked responses as a diagnostic aid in thoracic outlet syndrome. A preoperative study.

Responses evoked in the supraclavicular fossa (Erb's point) were recorded after stimulation of the median and ulnar nerves separately in both arms. The recordings were made in 20 healthy controls and 13 patients with unilateral thoracic outlet syndrome. In 12 of the 13 patients subsequent surgery clearly confirmed the diagnosis. Nine of the 13 patients showed abnormalities in the preoperative recordings at Erb's point. In all of these nine patients the relative amplitude difference on the affected side was outside the normal range. In two patients there was also abnormally low conduction velocity. The differences of amplitudes in the Erb's point responses between patients and controls were statistically significant. The suggestion is made that Erb's point responses evoked by stimulation of the median and ulnar nerves may be of diagnostic value in thoracic outlet syndrome and that the method is suitable as a supplement to conventional electroneurography in routine clinical practice.

Somatosensory evoked potentials in diagnostics of cervical spondylosis and herniated disc.

Somatosensory evoked potentials (SEPs) were recorded in 16 healthy controls and 12 patients suffering symptoms typical of cervical spondylosis and/or herniated disc and showing abnormal findings both in clinical and myelographic examinations. SEP recordings were performed at 3 different levels of the nervous system, at Erb's point, over the 7th cervical spine and at the inion, by stimulating the median nerve separately at both wrists. Nine of the 12 patients were chosen for surgical treatment, while 3 patients received physiotherapy. Six out of the 12 patients showed abnormal findings in SEP recordings, while the 3 patients chosen for the physiotherapy group showed normal SEP recordings. In the present study the amplitudes of the responses may seem to reflect nerve lesions caused by spondylotic deformities more than the latencies of responses. The results suggest that the SEP recordings may have value as a diagnostic aid in cervical spondylosis and spinal stenosis, which finding is in agreement with those of some other authors.

Serial measurements of quantitative EEG and cerebral blood flow and circulation time after brain infarction.

The quantitative EEG (QEEG), regional cerebral blood flow (rCBF) and circulation time of 17 patients were examined semisimultaneously thrice during the first 3 months after a cerebral supratentorial infarction. The EEG was quantified according to normalized slope descriptor technique in nine patients and by means of a combined period and amplitude analysis in eight patients. Intravenously injected isotopes 133Xenon and 99TcmO4 were used for blood flow and circulation time measurements. The QEEG-values improved during the whole follow-up period. Cerebral blood flow stayed low for all 3 months and did not alter during this period, while initially prolonged circulation time to some extent improved within 2 weeks remaining, however, prolonged even thereafter. A tendency for a positive correlation between QEEG and rCBF values in the infarcted hemisphere could be seen.