Academic journal article South African Journal of Psychiatry

The Clinical Value of Brain Computerised Tomography in a General Hospital Psychiatric Service

Academic journal article South African Journal of Psychiatry

The Clinical Value of Brain Computerised Tomography in a General Hospital Psychiatric Service

Article excerpt

Introduction

When evaluating a patient, a psychiatrist is often faced by the following dilemma regarding neuroimaging: either that no further imaging is warranted or to request further neuroimaging by computerised tomography (CT) scan or magnetic resonance imaging (MRI) scan. The selection criteria for CT scanning eligibility vary among psychiatric units. Published data have also showed varied results at different units. The purpose of this study was to describe the current trends in neuroimaging of mentally ill patients as well as to demonstrate the value of the CT scan as it is currently utilised. The study protocol entailed determining the number of patients imaged by CT scanning and documenting the psychiatric diagnoses made. Key objectives further included identification of the number of patients with abnormal findings on CT scanning and to assess if the CT findings impacted the treatment administered.

In 1992, in a retrospective study, Berk analysed the indications for CT scanning in psychiatric inpatients and concluded that there are specific clinical variables that correlated with scan abnormality. Furthermore these variables, including presence of neurological abnormality, diagnosis of delirium or dementia, organic mental state abnormality and EEG abnormality could be used as clinical guidelines for referral for CT scan. (1) Other relevant clinical factors to consider are older age of patient, history of prior head injury, alcohol abuse and neuropsychological test abnormality.

Emsley et al., in a retrospective study of 100 patients referred for CT scans, reported abnormalities in 61 patients. Of these patients, 23% had focal brain lesions. The conclusion of the study was that certain clinical factors are useful in identifying patients that may warrant CT scanning. (2) This study also highlighted the fact that a too restrictive approach in selection for CT scanning may risk the failure to detect a significant intracranial lesion.

Computerised tomography scanning may be of benefit in psychiatric practice in one of two ways. In the first instance, CT scanning can serve to confirm or exclude the presence of an organic cause for the clinically identified neurological abnormality. On the contrary, some recommend, as an equivalent to baseline blood investigations, the routine use of CT scanning as a screening tool in all psychiatric patients. (3)

Larson et al. in a retrospective review of 123 patients provided an alternative to this latter approach. Of the patients in the study group, 85% were classified as having normal neuroimaging or normal except for cerebral atrophy. All the patients who showed abnormalities on CT scanning manifested with true positive findings on clinical examination. They, therefore, recommended a concept of using a 'rule in' approach advocating the use of CT scanning in those patients who presented with significant focal findings on neurological examination rather than a general 'rule out' approach. (4) This method allows for greater cost effectiveness whilst still maintaining a high level of selectivity and specificity--an approach that would have great benefit to a constrained health care system. Furthermore, according to the authors, over-reliance on CT may lead to failure to diagnose many other treatable medical illnesses that can present as psychiatric illnesses, with potentially hazardous results.

National Institute for Health and Care Excellence (NICE) Guidelines (5) of 2008 recommended that neuroimaging is not to be a routine part of the initial investigations for the management of first-episode psychosis patients. The appraisal committee reviewed evidence supplied by several sources including submissions by patient care groups, manufacturers of CT equipment, professional or specialist groups and commentator organisations. The assessment group concluded that it was not cost-effective to routinely image such patients by CT scanning as this modality resulted in positive findings that would influence clinical management in only 0. …

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