D.W.K. Collins

Pattern-reversal visual evoked potential

A detailed method of analysis of the pattern-reversal visual evoked potential is presented. This method takes into account a number of parameters in addition to the latency of the major surface-positive component (P2) and has been tested in a group of 50 normal subjects and in 98 patients with established or suspected multiple sclerosis (MS). It was found that this more detailed form of analysis improved the detection rate of abnormal responses in the MS subjects particularly in those classified in the suspected category. The potential value of this form of analysis, particularly in clinical neurophysiology laboratories where the recording of visual evoked potentials is the only technique employed in the investigation of patients with suspected MS, is discussed.

Evoked potentials, saccadic velocities, and computerized tomography in diagnosis of multiple sclerosis.

One hundred and two patients with suspected or established multiple sclerosis (MS) were investigated by one or more of the following techniques: measurement of visual evoked potentials (VEP); measurement of cervical and cortical somatosensory evoked potentials (SEP); measurement of horizontal saccadic eye movement velocities (SV); and computerised axial tomography of the cranium and orbits (CT). Each of the techniques was valuable in detecting abnormalities, some of which were subclinical, in many patients. More abnormalities were found in patients studied by more than one technique, the most being detected in patients who were studied by all five techniques. We conclude that the techniques have a complementary role in investigating suspected MS.

Visual and spinal evoked potentials in diagnosis of multiple sclerosis.

The measurement of cortical evoked potentials generated by pattern reversal is a sensitive technique for detecting demyelinating lesions in the anterior visual pathways.1 2 Similarly changes in the somatosensory evoked potential recorded over the cervical spine3 have been found in many patients with multiple sclerosis (MS).4 We have assessed the relative and complementary values of these two techniques in 68 patients with suspected or established MS.

Effects of induced hyperthermia on visual evoked potentials and saccade parameters in normal subjects and multiple sclerosis patients.

A convenient method for raising body temperature has been developed and used to evaluate temperature effects on visual evoked potentials and saccade reaction time and velocity in five normal subjects and five patients with multiple sclerosis.

On-line electro-oculography

The design and use of an on-line PDP 11/40-based system for quantitative study of ocular kinetics are described. The system can be used in neurophysiological or ophthalmological applications. Two different techniques are presented. In one, horizontal, vertical or oblique eye motion can be studied, in the other horizontal eye motion only. Several parameters of eye motion can be measured including saccadic velocity, eye movement latency and accuracy of refixation. For ophthalmological EOG applications the system allows measurement of the absolute voltage excursion corresponding to a horizontal eye movement of a specific amplitude. The system consists of five software programs and supporting signal processing equipment. The software package runs under the RSX11M executive.

Computerised assessment of cardiac pacemaker performance.

The design and use of a PDP 11/40 based automated on-line cardiac pacemaker assessment system is described. One program has been developed for testing pacemakers on the bench and another for implanted pacemaker tests. Either fixed rate or demand pacemakers can be tested. The on-line system is easy and fast to use and is also highly accurate. Parameters extracted are pulse width, rate and pulse energy. In addition, a graphical representation of the patients ECG and the pacemaker pulse is obtained on a computer graphics terminal.

A versatile averaging system for neurophysiology.

This paper describes a fully developed and versatile PDP 11-based averaging system for the neurophysiology laboratory. Data collection parameters can be varied with ease. A hardware pseudo-random timer is provided to control patient stimulation in cerebral evoked response measurements. Quantitative data analysis programs are provided. EMG contamination in cerebral evoked response measurements is minimised and information on the patients habituation to the stimulus is automatically extracted. To find broad application the basic data collection program has been developed to run under either the disk operating system (DOS) or a real time sharing executive (RSX11D).

SACCADIC VELOCITIES IN DIAGNOSIS OF MYASTHENIA GRAVIS

Horizontal saccadic eye movement velocities have been measured in patients with multiple sclerosis and myasthenia gravis using a computerised electrooculographic technique. The ability to detect subclinical abnormalities of eye movement with this technique indicates that it is of diagnostic value in patients with suspected multiple sclerosis who present with only a single symptomatic lesion in the central nervous system. The technique is also of value in the diagnosis of myasthenia gravis as it provides a means of quantifying the response of the extra-ocular muscles to anticholinesterase preparations.

Vector cardiographic assessment of implanted cardiac pacemakers

The design and use of an on-line PDP 11/40 based vector cardiographic pacemaker assessment system is described. The system has been designed for comprehensive, automated testing of either fixed rate or demand implanted cardiac pacemakers. It is accurate and can be operated by a laboratory assistant without special training. Pacemaker parameters extracted are pulse height, width, rate, energy index and the frontal plane vector length and angle at maximum inspiration and during quiet breathing. In addition, a graphical representation of the patients ECG and the pacemaker pulse is obtained on a computer graphics terminal. Patient data are written to cartridge disk for permanent record following the test. At each subsequent test of the implanted pacemaker, the data on disk are addended with the latest quantitative results. A separate off-line FORTRAN program can interrogate disk files for detailed analysis of patient data and display of parameter trends since implantation.