As of 1999:

                              Medical         Doctor 
               Seizure        Updates         Required 
State          Free Period    Required*       to Report 
-------------------------------------------------------- 
Alabama        6 months       every 5 years   no 
Alaska         6 months       DMV             no 
Arizona        3 months       DMV             no 
Arkansas       1 year         DMV             no 
California     3,6,12 months  DMV             yes 
Colorado       no set period  DMV             no 
Connecticut    no set period  DMV             no 
Delaware       no set period  every year      no** 
DC             1 year         anually         no 
Florida        up to doctor   MAB             no 
Georgia        1 year         DMV             no 
Hawaii         1 year         DMV             no 
Idaho          6 months       anually         no 
Illinois       no set period  MAB             no 
Indiana        no set period  MAB             no 
Iowa           6 months       6 months        no 
Kansas         6 months       anually         no 
Kentucky       3 months       at renewal      no 
Louisiana      6 months       DMV             no 
Maine          3 months       DMV             no 
Maryland       3 months       DMV             no 
Massachusettes 6 months       at renewal      no 
Michigan       6 months       MAB             no 
Minnesota      6 months       every 6 months  no 
Mississippi    1 year         MAB             no 
Missouri       6 months       MAB             no 
Montana        no set period  no              no 
Nebraska       3 months       no              no 
Nevada         3 months       anually         yes 
New Hampshire  1 year         no              no 
New Jersey     1 year         every 5 months  yes 
New Mexico     1 year         MAB             no 
New York       1 year         DMV             no 
North Carolina 6-12 months    anually         no 
North Dakota   6 months       anually         no 
Ohio           no set period  (bi)anually     no 
Oklahoma       1 year         DPS             no 
Oregon         6 months       DMV             yes 
Pennsylvania   5 months       MAB             yes 
Puerto Rico    no set period  MAB             no 
Rhode Island   18 months      MAB             no 
South Carolina 6 months       every 6 months  no 
South Dakota   6-12 months    every 6 months  no 
Tennessee      6 months       MAB             no 
Texas          6 months       anually         no 
Utah           3 months       every 6 months  no 
Vermont        no set period  MAB             no 
Virginia       6 months       MAB             no 
Washington     6 months       MAB             no 
West Virginia  1 year         MAB             no 
Wisconsin      3 months       every 6 months  no 
Wyoming        3 months       DMV             no 
 

*
DMV = at the discretion of the DMV or other licensing agent.
MAB = at the discretion of a medical advisory board.
DPS = at the discretion of the Department of Public Safety
(bi)anually = 6 or 12 months at the discretion of the DMV

** the doctor is required to report only if the seizures include a loss of consciousness.