November 5, 2007 (Boston) — Near-infrared spectroscopy (NIRS) has potential as a tool for the early diagnosis of hepatic encephalopathy (HE), according to a study presented at the American Association for the Study of Liver Diseases (AASLD) 58th Annual Meeting.
Because the technique has been used to image brain function in psychiatric disorders, researchers thought it might be useful for the diagnosis of HE, said lead author Hiroyuki Nakanishi, MD, of the Musashino Red Cross Hospital, Tokyo, Japan.
Hepatic encephalopathy is a psychiatric decline that accompanies cirrhosis. Some liver disease patients have a mild or subclinical level of HE, but there is no way to diagnosis it. NIRS measures blood hemoglobin concentrations related to brain activity.
Dr. Nakanishi's multidisciplinary team, which included specialists from 3 hospitals, enrolled 45 patients with chronic liver disease and 12 healthy control patients. Sixteen patients had already been diagnosed with HE. Seven patients with chronic liver disease and abnormal electric encephalography (EEG) were defined as minimal HE.
The relative concentrations of oxyhemoglobin (oxy Hb) — the measure of brain function — were measured every 0.1 seconds while researchers conducted a word fluency task. The researchers found that the overt HE patients had smaller and slower oxy Hb increases during the task compared with the healthy patients. The average peak value of oxy Hb was 0.24 ± 0.14 in overt HE patients compared with 0.68 ± 0.41 in patients without HE ( P < .001). The average peak value was small in patients with minimal or overt HE.
The increases of oxy Hb concentration were also smaller and slower during the word fluency task in 18 patients with abnormal EEG than in 31 individuals with normal EEG ( P = .02). The average peak value was significantly smaller in minimal or overt HE. The patients with minimal or overt HE showed smaller increases in oxy Hb concentration than did patients without HE.
Because NIRS showed smaller increases in oxy HB in patients with minimal or overt HE, it could be used as a noninvasive, bedside diagnostic tool, said Dr. Nakanishi.
Kevin D. Mullen, MD, of Case Western Reserve University and MetroHealth Medical Center in Cleveland, Ohio, called the study "kind of neat.... HE does, in many studies, correlate with blood flow."
A lot of patients with cirrhosis have subtle changes in cognitive function, said Arun Sanyal, MD, a member of the AASLD governing board and a researcher at Virginia Commonwealth University in Richmond, so there is a need for an objective measures. At the same time, he said, the NIRS test, although not invasive, might be "cumbersome.... It's a step. It's not the step."
American Association for the Study of Liver Diseases 58th Annual Meeting: Abstract 768. Presented November 4, 2007.
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