Clinical Neurophysiology of Dementia

Creutzfeldt-Jakob disease and the eye. I. Background and patient management

This article attempts to summarise our current understanding of TSEs as they affect man. Specific aspects relevant to ophthalmological practice, in particular the management of patients in day-to-day clinical practice and with respect to corneal transplantation, have been discussed. In the companion article we discuss the specific ophthalmic and neuro-ophthalmic features of these diseases.

Quantitation of photic driving in dementia with normal EEG

The EEG is frequently normal when early dementia is clinically suspected. The presence or absence of occipital driving with intermittent photic stimulation is not helpful in detecting cerebral pathology, but quantitation of photic driving was shown to distinguish between dementia and depression in geriatric patients. We quantified photic driving in twenty clinically demented patients without diffuse or focal EEG abnormality, and compared this in 20 age-matched normal controls. Intermittent stimulation at odd-numbered frequencies between 1 and 31 Hz was carried out. The product of frequency of stimulation and duration of driving response was determined, and the incidence of absent, subharmonic and supraharmonic photic driving was determined. The quantitative measure of frequency times following duration was significantly greater in the nondemented individuals than in demented patients with normal EEGs. More nondemented individuals demonstrated supraharmonic and subharmonic responses than did demented patients. The range of normal variability in persistence, duration, and symmetry of photic driving is great, and caution in determining abnormality on this basis is appropriate. Subtle but measurable changes in photic driving may occur early in dementing illnesses, however.

Predictive value of electroencephalography for electroconvulsive therapy

The EEG has been a widely-used screening procedure before ECT. Previous studies have correlated seizures and post-ECT slowing with ECT efficacy. We investigated the utility of pre-ECT EEG in predicting therapeutic response and post-ECT confusion. EEGs were normal in 54 of 100 patients undergoing first courses of ECT for refractory depression. Patterns within the normal range, were present in 26/100 while 2/100 had paroxysmal discharges without clinical evidence of epilepsy. Focal and generalized EEG slowing were each present in 9/100 records. Full recovery occurred after ECT in 66.6 per cent of those with normal pre-ECT records, 61.5 per cent with borderline EEGs, 55.5 per cent of patients with diffuse EEG slowing, and 22.2 of cases with focal slow waves. Of those with EEG slowing 22.2 percent had little or no response to ECT as compared to 19.2 per cent with EEGs within normal limits and 9.3 per cent with normal EEGs. Four of 6 patients with prolonged confusion had normal EEGs, while 1 each had focal and generalized slowing. EEG slowing was related to incomplete ECT response, but not to therapeutic failure or post-ECT confusion. The limited predictive power of pre-ECT EEG may reflect the prevalence of normal or nonspecifically abnormal EEGs in psychiatric patients and the general efficacy of ECT. Other neurophysiologic methods may yield more definitive information about the mechanism and use of ECT.

The role of clinical neuropsychology in the neurological diagnosis of Alzheimer's disease

This survey on the early diagnosis of Alzheimer's disease (AD) reinstates the role of clinical neuropsychology in describing the cognitive status of AD and its evolution. The role of clinical neuropsychology is restricted to the clinical diagnosis of organic mental deterioration and its contribution to the diagnosis of AD is separate from that of neurology and neuroradiology. The frequency of a single neuropsychological disturbance in early AD patients is illustrated by our own observations.