* Nikkei up 3.58 pct to bounce from 20-mth low, Topix up 4.19 pct
* Energy-related shares boosted by crude oil rebound
By Shinichi Saoshiro
TOKYO, Dec 27 (Reuters) - Japan's Nikkei share average rallied on Thursday, pulling away from a 20-month trough, after spectacular rebound on Wall Street after a dismal start to the week.
The Nikkei was up 3.58 percent at 20,015.11 after sliding to 18,948.58 on Wednesday, its lowest since late April 2017.
The Dow surged more than 1,000 points for the first time overnight, leading a broad Wall Street rebound after a report of robust holiday sales helped mollify concerns about the health of the U.S. economy.
Earlier, Wall Street had suffered its worst-ever Christmas Eve drop on the back of factors including turmoil in the White House.
"Japanese shares may be higher, but with market volatility so high, tomorrow could be an entirely different story," said Soichiro Monji, senior economist at Daiwa SB Investments.
"Equities are moving up and down in holiday-thinned trade, and it would take the return of many investors next year for the market to gather its bearings."
Energy-related shares were boosted as oil surged, posting its strongest daily gain in more than two years in a partial rebound from steep losses that had pushed crude benchmarks to lows not seen since 2017.
Petroleum product majors Inpex Corp and Japan Petroleum Exploration Co rose 4.3 percent and 4.9 percent, respectively. Oil refiner Idemitsu Kosan climbed 10.6 percent and Showa Shell Sekiyu KK advanced 8.9 percent.
Information technology company Cybozu Inc jumped 9.2 percent after it raised its profit outlook for the year through December 2018.
The broader Topix was up 4.19 percent at 1,491.52 following a descent to 1,408.89 on Wednesday, its lowest since November 2016.
All of the Tokyo Stock Exchange's 33 subindexes were in positive territory, led by oil and coal products. (Editing by Shri Navaratnam)