|  |  |  | Intelligence Quotient | |||
---|---|---|---|---|---|---|---|
 |  |  |  | Degree of Mental Retardation (%) | |||
Investigator | Year | Number enrolled | Mean Age* | Normal -Borderline | Mild | Moderate | Severe |
Einfelda [47] | 1999 | 46 | 17.7 | 21.6 | 64.9 | 13.5 | 0 |
Gross-Tsurb [51] | 2001 | 18 | 14.3 | 73 | 27 | 0 | 0 |
Deschee-Maeker [52] | 2002 | 55 | 14.1 | 25.4 | 27.3 | 40 | 7.3 |
Whittington [53] | 2004 | 55 | 21.0 | 31 | 41.8 | 27.2 | 0 |
Copet [54] | 2010 | 85 | 24.2 | 7 | 54 | 39 | 0 |
Roof [55] | 2000 | 47 | 23.2 | 24 | 38 | 30 | 8 |