An assessment of perfusion deficits in decompression illness using 99Tcm HMPAO SPET and statistical parametric mapping.

AIM

The aim of this study was to use statistical parametric mapping (SPM) to investigate differences in the regional cerebral blood flow (rCBF) of decompression illness (DCI) and non-diving control subjects.

METHODS

Twenty DCI subjects were imaged using 99Tcm hexamethylproplylene amine oxime (HMPAO) single photon emission tomography (SPET) within days of their incident of DCI, and on a second occasion between 2 and 27 months after their DCI event. SPM was used to make a comparison between decompression illness studies and a second group of non-diving control studies for both early and late imaging of DCI. A paired comparison of early and late imaging was also performed testing for correlation between time of imaging and changes in the rCBF pattern.

RESULTS

The comparison between control subjects and early imaging of decompression illness showed a large, significant (P = 0.002), irregularly shaped, multi-focal area of reduced uptake in the left occipito-parieto-temporal region of the brain. Comparisons between control and repeat decompression illness imaging studies showed two areas of reduced uptake. The first was similar to that found in the initial comparison although it was less significant (P = 0.035). The second region was similar but contra-lateral to the first region with significance P < 0.001. An attempt to correlate any changes in rCBF with the time that elapsed between each set of imaging found no areas of significant correlation.

CONCLUSION

99Tcm HMPAO SPET images of decompression illness display areas of reduced perfusion, which persist in the majority of cases.