A C210 ENCOUNTERED SEVERE TURB AT 3800 FT DSNDING. THE ACFT DSNDED TO 1200 FT BEFORE PLT REGAINED CTL.

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MY ACFT WAS ON VOR APCH TO RWY 15; SYRACUSE. I WAS REQUESTED TO DSND TO 2000 FT FROM 5000 FT. PASSING THROUGH APPROX 3800 FT; WE ENCOUNTERED SEVERE TURB. IT OCCURRED A SINGLE TIME; WHICH I THEN RPTED TO ATC. THEN; HOWEVER; IT RETURNED AS WE DSNDED LOWER; BECOMING MORE VIOLENT. BOTH MY WIFE AND I WERE THROWN ABOUT THE CABIN; OUR AUTOPLT WAS DEACTIVATED BY THE TURB; AND OUR AUTO TRIM SHUT DOWN (IT MAY HAVE BEEN STRUCK BY MY HAND). I PULLED THE ACFT UP; USING FULL POWER; BUT CONTINUED DSNDING THROUGH THE BOTTOM LAYER OF CLOUDS (APPROX 2000 FT). BEFORE I COULD BRING THE ACFT BACK; WE HAD DSNDED TO APPROX 1200 TO 1300 FT; WHEN ATC CALLED AND ADVISED WE HAD DSNDED TOO LOW. I ADVISED I WAS AWARE; AS WE WERE TRYING TO REGAIN CTL. ONCE OUTSIDE THE BOTTOM OF THE CLOUD LAYER; WE WERE ABLE TO ASCEND; AND COMPLETE THE LNDG. AFTER FIRST ENCOUNTERING THE SEVERE TURB; I SHOULD HAVE IMMEDIATELY DISCONNECTED THE AUTOPLT; AND APPLIED FULL POWER AT THAT TIME. HOWEVER; WE FELT THE WORST WAS OVER. IT WASN'T AND WE RE-ENTERED AN AREA OF EVEN STRONGER TURB. AT THAT TIME; EVEN WITH MY SEAT BELT ON; I STRUCK MY HEAD ON THE CEILING; KNOCKING OFF MY HEADPHONES AND GLASSES. IN RETROSPECT; OF COURSE MY SEATBELT SHOULD HAVE BEEN TIGHTER IF WE HAD ANTICIPATED SUCH TURB. OTHERWISE; I'M NOT SURE WE HAD FURTHER OPTIONS OTHER THAN THE ABOVE.