An investigation of the potential use of Tc-HMPAO-SPECT scanning in decompression illness.

Evans, Sian Amanda

Abstract

There is concern that divers who experience an episode of decompression illness (DCI) may also sustain occult nervous tissue damage which is undetectable to standard clinical examination. Although unapparent in the acute phase of the disorder, such occult tissue damage could potentially give rise to clinically significant symptoms in later life. The issue raises important questions over the efficacy of current DCI therapy and follow-up procedures, and over the divers’ continued fitness to dive. The reporting of abnormal Tc99-HMPAO-SPECT cerebral perfusion scans in divers who have experienced DCI has been cited in support of the occurrence of occult cerebral damage in these individuals. However, subsequent study has highlighted some of the limitations of SPECT imaging. There is a danger that patients may suffer "over-investigation" with the newest technology before its diagnostic limitations, and the clinical significance of the findings, are fully understood. In the light of these concerns, this clinical study was performed to investigate the use of Tc99-HMPAO-SPECT as a means of detecting nervous tissue damage following an episode of DCI and as a possible predictor of clinically significant sequelae in the longer-term. The study was conducted in two separate but related phases. In the first phase, a blinded comparison of the Tc99-HMPAO-SPECT scan appearances in divers who have suffered DCI, divers who have never suffered DCI and non-divers was performed. A retrospective analysis was carried out to identify any correlation between SPECT scan appearance and diving history or clinical presentation. In the second phase of the study, divers who had previously been investigated by Tc99-HMPAO were followed-up and reviewed by clinical history and examination and by neuropsychological assessment. Following these investigations, the occurrence of abnormalities of Tc99-HMPAO-SPECT uptake in divers who have experienced DCI can not be discounted. However, the use of Tc99-HMPAO-SPECT in the routine clinical investigation for nervous tissue damage arising as a result of DCI is of unproven value. The Tc99-HMPAO-SPECT scan appearance of a diver following DCI does not appear to correlate with subsequent neuropsychological performances as assessed by the neuropsychological test battery used in this study. Thus, the prognostic capabilities of the technique are also unproven. Although not one of the aims of the investigation, this study has highlighted the difficulties experienced by some divers following DCI. This subject requires further investigation.

Citation

EVANS, S.A. 1994. An investigation of the potential use of Tc-HMPAO-SPECT scanning in decompression illness. Robert Gordon University, PhD thesis. Hosted on OpenAIR [online]. Available from: https://doi.org/10.48526/rgu-wt-2807377

• Thesis Type: Thesis
• Deposit Date: Sep 8, 2025
• Publicly Available Date: Sep 8, 2025
• DOI: https://doi.org/10.48526/rgu-wt-2807377
• Public URL: https://rgu-repository.worktribe.com/output/2807377
• Award Date: Feb 28, 1994