I started my career at St Thomas’ Hospital London, where I gained knowledge
and experience of routine EEGs as well as an appreciation of evoked potentials
and nerve conduction studies. Moving to Bristol and working at the Burden
Centre enabled me to consolidate and further my experience and exposure in all
neurophysiology testing, being guided and mentored by Dr Nick Kane. Education
of physiologists has played a large part of my career and I have enjoyed seeing
staff develop and further their careers, and I was Chair of the Association of Neurophysiological Scientists education committee for many years before becoming Chair of this professional body in 2018. Currently I am service manager and clinical lead of the Grey Walter Department of Clinical Neurophysiology at Southmead Hospital, Bristol. But I still manage to make time for clinical work, and I have a keen interest in intraoperative monitoring and now tend to spend the majority of my time involved in neurosurgical monitoring, and this was my thesis for the Higher Specialist Scientific Training doctorate degree. Outside of work I enjoy running, and particularly getting off road for some cross-country runs at the weekends, but I have no intention of running a marathon.

The fundamental function of the nervous system lies in the transmission of impulses, and these can be assessed by time locked averaging of evoked potentials following stimulation of the peripheral nervous system.
Somatosensory evoked potentials (SEPs) following electrical stimulation of the mixed nerve of the median and posterior tibial nerves can assess the conduction through the peripheral nerves, brachial and lumbo-sacral plexus, posterior spinal cord and medial lemniscal pathways of the brainstem, up to the cortex. Brainstem auditory evoked potentials (BAEPs) are far-field potentials which reflect highly synchronous activation of the major ascending auditory centres from the cochlea to the inferior colliculus in the mid-brain. BAEPs can be used to assess the peripheral hearing apparatus in conductive and sensorineural hearing disorders and can assess the brainstem auditory tracts in central nervous system disorders.
SEPs and BAEPs are reliable and objective measures of nervous system function that are sensitive enough to detect abnormalities even when the physical examination is normal. These evoked potential modalities can meet a variety of specific objectives that can be useful to the referring clinician. These include
1) Objective evidence of abnormality when signs or symptoms are equivocal
2) Detection of clinically silent lesions
3) Localisation of the anatomical level of impairment along a pathway
4) Providing evidence about the general category of the pathology
5) Monitoring of objective changes in the patient’s status over time.
Although widely used in the past, the subsequent development of sophisticated imaging techniques has led to the recent decline in the role of SEP and BAEP recordings in the clinical diagnosis of neurological disease. However, the latencies of evoked potentials are quantifiable to 2-3 significant figures and most of the major SEP and BAEP peaks are stable over time (often of identical latencies, wave shape and amplitude in individual patients when re-tested). Also, as they are not overly influenced by the patient’s level of cooperation, they are amenable to parametric statistical analysis as biomarkers for certain disease development, i.e. multiple sclerosis.
The resistance of the somatosensory cortical evoked potential (N20) and BAEPs to sedative drugs enable them to be used for the confirmation of brain death in the ITU setting; and the bilateral absence of the N20 potential following hypoxic brain injury has a high association with an unfavourable prognosis.
The standardisation of the recording techniques used, and the appropriate use of normative data, is important as the role of evoked potentials changes from a primarily diagnostic utilisation to ones that involve longitudinal and cross-sectional monitoring of progressive disease and prognostication of patient outcome.