Department of Gastroenterology and Hepatology, Musashino Red Cross Hospital, 1-26-1 Kyonan-cho, Musashino-shi, Tokyo, 180-8610, Japan.
Near infrared spectroscopy (NIRS) is a tool that could noninvasively measure the regional cerebral oxygenated hemoglobin (oxy-Hb) concentration with high time resolution. The aim of the present study is to reveal the time-dependent regional cerebral oxy-Hb concentration change coupled with brain activity during task performance in patients with MHE.
Cerebral oxy-Hb concentration was measured by using NIRS in 29 cirrhotic patients without overt HE. Of those, 16 patients who had abnormal electroencephalography findings were defined as having minimal HE (MHE). Responsive increase in oxy-Hb during a word fluency task was compared between MHE and no-MHE patients.
There was no difference in the maximum value of oxy-Hb increase between patients with and without MHE (0.26±0.12 mM mm vs. 0.32±0.22 mM mm, p=0.37). However, the pattern of the time course changes of oxy-Hb was different between 2 groups. The MHE group was characterized by a gradual increase of oxy-Hb throughout the task compared to steep and repetitive increase in no-MHE. Increase in oxy-Hb concentration at 5 seconds after starting the task was significantly small in MHE compared to no-MHE (0.03±0.05 mM mm vs. 0.11 ± 0.09 mM mm, p=0.006).
The cerebral oxygen concentration is poorly reactive in response to task among cirrhotic patients without overt HE but having abnormal electroencephalography findings. These impaired responses in regional cerebral oxy-Hb concentration may be related to the latent impairment of brain activity seen in MHE.