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The accurate assessment of local blood flow by recording the washout of a deposit of radiolabelled 4-iodoantipyrine (4-IAP) requires the use of a stable radiopharmaceutical. This communication shows that it is possible to produce a 125I and 131I-4-IAP compound which fulfills this requirement under simulated conditions of use.

The brainstem auditory-evoked potential (BAEP) is often employed to determine auditory threshold in subjects who are unable to complete traditional behavioural testing. These responses are usually recorded during natural or drug-induced sleep. The effects of sleep on the BAEP threshold have however not been determined. BAEPs were recorded in 8 young adults in wakefulness and during natural sleep. Click stimuli were presented through a hearing aid device at either 0, 5, 10, 20 or 30 dB above the behavioural threshold. The amplitude of wave V decreased and its latency increased with decreases in stimulus intensity. The BAEP waveform was invariant in sleep. The overall mean BAEP threshold was approximately 16 dB above that determined by behavioural methods. This did not significantly vary in the sleeping subject.

This study demonstrates residual mental deficits in patients who have apparently recovered after closed head injury. Twenty closed head injury patients were compared to 20 normal control subjects matched for age, sex, handedness, education, language, and IQ. All received a series of neuropsychological tests. Discriminant function analysis significantly differentiated the two groups. Correct classification of individuals as having suffered a head injury or not was 85%. The head injury patients did have primary impairment on tests of divided attention. Litigation was not a factor. We propose that this impairment of information processing reflects residual brain damage secondary to the closed head injury.

A computer program, developed for peak detection of averaged evoked potential waveforms, is described. The program is able to automatically score up to 200 data files in a single session. The user is asked to define intervals (windows) in which a maximum peak is to be detected. The program can optionally search each EEG channel or a single 'reference' channel from which all other channels will be compared. The mean amplitude of several data points can also be computed within a particular window. When evoked potentials are particularly noisy, it is possible to estimate the 'signal' in the higher frequency background 'noise'. Because the program is written in BASIC, it can be readily transferred to many different computer systems.

The plasma peptide hormone bradykinin is hypothesized to be a major mediator of the multiple-system functional symptomatology of adverse food and other chemical reactions. It is postulated that native foods as organic chemicals could act cumulatively with other stresses to mobilize directly the kinin-forming enzyme system.

The various factors which may be involved in the incorrect measurement of bone-conduction threshold are outlined. One of these factors, airborne radiation from the vibrator, has been investigated for three Radioear vibrators, the B70A, B71 and B72. The results indicate that false bone-conduction threshold values could arise, due to the airborne radiation component, mainly with the B72 vibrator.

Twenty narcoleptic patients and ten age-matched normals were polygraphically monitored for 58 consecutive hours. All subjects were on regimented sleep (hours between 2230 and 0700). Group A (11 patients and 10 normals) had enforced wakefulness during the day whereas Group B (9 patients) were permitted to sleep (mean = 2 1/2 hr.). On day 2, all subjects were permitted to sleep for 15-min periods every 2 hr. In narcoloptics, sleep recordings demonstrated a reduction of sleep latency, an increase of stage 1, and a decrease in stages 3 and 4 compared to normals, but total REM time and percentage of REM sleep were similar. Groups A and B showed no difference in the incidence of nocturnal awakenings. REM cyclic periodicity was larger in narcoleptics who also demonstrated a REM-sleep fragmentation. This fragmentation became more pronounced as time passed, with several shifts from REM to wakefulness and stage 1. Narcoleptics present REM onset sleep period but also show an inability to remain in REM sleep.

Electrostimulation audiometry can provide high-frequency bone-conduction threshold measurements. To evaluate the use of such an audiometer in monitoring hearing, the following areas were investigated. (1) The variability and repeatability of threshold measurements. (2) To see if the instrument could be used on the ward where the patient would have to wear ear plugs to attenuate background noise, the effect of occluding the ears was assessed. (3) The applicability of the instrument to the range of patients in whom monitoring would be appropriate, specifically the relationship between the patient's age and the effective upper frequency limit of the audiometer. The data showed a variability in threshold measurement that is quite comparable with that obtained with conventional audiometry but which became smaller at frequencies of 12 kHz and higher. There was no overall effect on the threshold of occluding the ears, which meant that the instrument can be used to monitor a non-isolated environment such as a ward. The effective cut-off frequency was about 9 kHz for patients aged 55 years, and so the use of an electrostimulation audiometer to monitor high-frequency auditory thresholds is restricted to younger patients.

Four patients treated with tricyclic antidepressants and one patient treated with trazodone all demonstrated marked increases in plasma levels of these drugs after the addition of fluoxetine. Such increases could increase adverse effects.

An experiment was conducted to determine, under different conditions, the capacity of young adult East African goats to eliminate intravenously inoculated [75Se]selenomethionine-labelled Trypanosoma brucei from the bloodstream. Over 80% of labelled trypanosomes, preincubated for 1 h in inactivated normal goat serum, were detectable in the circulation 1 h after inoculation into normal goats. By contrast, after incubation in serum from goats which had been immunised against the homologous trypanosome clone, parasites were largely removed from the bloodstream within 5 min after inoculation. When the goats were necropsied 1 h after the inoculation of radiolabelled trypanosomes, 50% of the injected activity was found in the liver and lungs, the contribution of each organ being dependent to some extent on whether the inoculum was via a mesenteric or the jugular vein. The same result was obtained when labelled parasites were incubated in normal goat serum, and then inoculated into immunised goats; thus, rapid blood clearance occurred, and high activity was detected in the lungs and liver. The results confirm those of previous studies in laboratory mice in which the removal of trypanosomes from the circulation of an immune animal was achieved primarily by uptake of opsonised trypanosomes by elements of the mononuclear phagocytic system.

Techniques used to monitor the function of the seventh and eighth cranial nerves during acoustic neuroma and other posterior fossa surgery are reviewed. The auditory brainstem response (ABR), electrocochleogram (ECochG) and direct recording from the auditory nerve (CNAP) were compared. The best technique is the ECochG, although in many cases, the CNAP should be used as a back-up technique. The CNAP is especially useful for the identification of the auditory nerve. Both can provide real-time feedback on the physiological integrity of the auditory nerve. The ABR may be helpful in monitoring brainstem function. For some procedures, optimal monitoring requires the combined recording of all three techniques. Monopolar constant-voltage intracranial stimulation of the facial nerve is helpful for the identification and preservation of the facial nerve. Audio monitoring of spontaneous electromyographic activity provides real-time feedback on the effect of surgical manipulation of the nerve. Monitoring of ephaptic transmission in the facial nerve during microvascular decompression for hemifacial spasm aids in the identification of the offending vessel.