Editors' Note

Editors' Note: In “Hyperbaric oxygen: B-level evidence in mild traumatic brain injury clinical trials,” Drs. Figueroa and Wright reviewed published clinical trials on the effect of hyperbaric oxygen therapy (HBOT) on mild to moderate traumatic brain injury/persistent postconcussion syndrome (mTBI/PPCS) and concluded that HBOT has therapeutic effects on mTBI/PPCS symptoms and can alleviate posttraumatic stress disorder symptoms secondary to a brain injury. Challenging the review, Drs. Hampson and Holm critique the claim that oxygen content of arterial blood plasma (oxygen dissolved in plasma) during hyperbaric exposure correlates with treatment response. They point out that arterial blood plasma oxygen content was not measured in any of the studies reviewed and that the authors presumably estimated the arterial blood partial pressure of oxygen from the calculated alveolar PO₂ using the alveolar gas equation and assumed that the participants had normal metabolism and pulmonary. They also suggest that the authors did not take into consideration the fact that the studies used different treatment times and numbers. Drs. Figueroa and Wright agree that PaO₂ was not measured in the published studies but assumed that study participants had normal metabolism and pulmonary function since they were cleared to be placed inside a pressure vessel. They also address the difference in time to HBOT exposure and stress that pressurized air is a biologically active agent, rendering the conclusions of inactivity or placebo effect in HBOT/TBI studies questionable. In the study “Autopsy validation of ¹²³I-FP-CIT dopaminergic neuroimaging for the diagnosis of DLB,” Thomas et al. showed that ¹²³I-FP-CIT imaging in dementia is a valid and accurate biomarker for dementia with Lewy bodies (DLB) and that the high specificity compared with clinical diagnosis (20% higher) is clinically important. They also concluded that while an abnormal ¹²³I-FP-CIT scan strongly supports Lewy body disease, a normal scan does not exclude DLB with minimal brainstem involvement. Commenting on the study, Professor Abe notes that there are some patients with cognitive and behavioral dysfunction, but without parkinsonism for years. In such situations, he says that he cannot diagnose patients with DLB. In response, Thomas et al. clarify that about 25% of patients with DLB do not show features of parkinsonism. This is recognized in the consensus criteria for DLB, which do not require parkinsonism for diagnosis. They emphasize that DLB can be recognized despite a normal dopaminergic scan if other characteristic symptoms of DLB are present.—Chafic Karam, MD, and Robert C. Griggs, MD