The value of ^99mTc-ECD SPECT early after the onset of subarachnoid hemorrhage in predicting symptomatic vasospasm and clinical outcome

Charalambos Iliadis¹, Dimitris J. Apostolopoulos², Costas Giannakenas², Tryfon Spyridonidis², Greta Wozniak³, Panagiotis Georgoulias³, Fotis Tzirtzidis¹, Theodoros Maraziotis¹, Pavlos J. Vassilakos²

Summary
Aim: Investigating the prognostic value of brain perfusion SPECT, within the first few days after Subarachnoid Haemorrhage (SAH) and predicting subsequent development of symptomatic vasospasm and the clinical outcome were aims of the study.
Material and method: Forty-two patients with SAH, aged 17-80 years, in a relatively good clinical condition (Hunt and Hess grade12) underwent a ^99mTc-ethyl cysteinate dimer (ECD) SPECT, 0-5 days after hospital admission. The perfusion was measured semi-quantitatively using symmetrical regions of interest, automatically drawn over cortical and subcortical structures on consecutive transverse slices. A summed perfusion defect score (SPDS) was used to quantify the brain perfusion. Vasospasm was assumed in patients presenting deterioration of consciousness, increase in body temperature or newly developed neurological deficit at least 3 days after SAH, or at least 48 hours after surgery, that could not be explained otherwise. The outcome was assessed six months after SAH and graded according to the Glasgow outcome scale (GOS).
Results: Twenty-seven patients had abnormal SPECT studies. Perfusion abnormalities were associated with CT findings, but not with patients´ neurological status on admission. Fifteen patients developed clinical vasospasm from day 4 to 13 post SAH, 19 had an uncomplicated course, while in an additional 8 cases the presence of other confounding factors rendered the diagnosis of vasospasm uncertain. SPDS differed significantly between groups with and without symptomatic vasospasm. All patients with vasospasm had abnormal SPECT studies on admission (100% Negative Predictive Value-NPV), while the Positive Predictive Value (PPV) was 75%. Similarly, regarding the clinical outcome 6 months after SAH, among other known predictor variables, SPECT showed the highest NPV (93.3%) for a favourable outcome (GOS 4 or 5). However, its PPV was only 52%.
Conclusion: The implementation of brain perfusion SPECT-ECD early after SAH seems to provide important prognostic information. A normal study is highly predictive of an uncomplicated clinical course and of a favourable outcome. An abnormal SPECT is accompanied with a reasonable PPV for subsequent symptomatic vasospasm, but with a low PPV regarding the clinical outcome.

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