Unexplained mental retardation: is brain MRI useful?
BACKGROUND
Mental retardation (MR), defined as an IQ below 70, is a frequent cause of consultation in paediatrics.


OBJECTIVE
To evaluate the yield of brain MRI in the diagnostic work-up of unexplained MR in children.


METHODS
The MRI features and clinical data of 100 patients (age 1-18 years) affected with non-progressive MR of unknown origin were compared to an age-matched control group (n=100). Two radiologists conducted an independent review of the MRI scans.


RESULTS
Univariate and multivariate analyses showed a higher incidence of brain anomalies in the MR group than in the control group (53 vs 17, OR=5.7 [2.9-11.1]), for signal abnormalities within the periventricular white matter (OR=20.3 [2.6-155.3]), lateral ventricular dilatation (OR=15.6 [2.0-124]), mild corpus callosum abnormalities (shortness, atrophy) (OR=6.8 [1.8-25.6]) and subtle cerebellar abnormalities, including fissure enlargement (OR=5.2 [1.1-26.2]). The diagnostic value of MRI abnormalities was considered good in 5% of patients (Alexander disease n=1, diffuse cortical malformation n=1, leukomalacia n=1, vermian agenesis n=1, commissural agenesis n=1), and weak in 48% of patients, in whom non-specific abnormalities did not lead to a diagnosis. Some clinical features resulted in a significantly higher percentage of abnormal MRI scans: abnormal neurological examination (82% vs 47%, P=0.008), abnormal skull circumference (66% vs 49%, P=0.04). Motor delay was associated with cerebellar abnormalities (P=0.01).


CONCLUSIONS
This study confirms the weak diagnostic yield of MRI in mentally retarded children. The use of a control group has enabled us to identify the neuroimaging markers frequently associated with MR. Subgrouping patients according to neuroimaging markers and clinical signs should help identify those who would benefit from molecular studies.
Decobert
Fabrice
F
Department of Radiology, Saint Vincent de Paul Hospital, 82 Avenue Denfert Rochereau, 75674 Paris Cedex 14, France.
Grabar
Sophie
S
Merzoug
Valerie
V
Kalifa
Gabriel
G
Ponsot
Gérard
G
Adamsbaum
Catherine
C
des Portes
Vincent
V
D000293:Adolescent; D001921:Brain / Q000002:abnormalities*; D016022:Case-Control Studies; D016009:Chi-Square Distribution; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D008607:Intellectual Disability / Q000175:diagnosis*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D018709:Statistics, Nonparametric
Epidemiol Rev. 1987;9:194-218
3315717
Eur J Radiol. 1998 May;27(2):139-44
9639139
Neuropediatrics. 2003 Jun;34(5):247-52
14598230
J Child Neurol. 1998 Mar;13(3):120-1
9535237
Pediatr Clin North Am. 1992 Aug;39(4):929-43
1635812
Arch Pediatr. 2002 Jul;9(7):709-25
12162161
J Child Neurol. 2002 Mar;17(3):164-8
12026229
Neuropediatrics. 1998 Dec;29(6):298-301
10029348
Pediatr Radiol. 2003 May;33(5):334-45
12695867
J Neuroradiol. 1991;18(4):291-307
1804933
AJNR Am J Neuroradiol. 1988 May-Jun;9(3):487-91
3132822
Psychiatry Res. 1997 Mar 14;74(1):1-12
10710158
J Radiol. 2000 Aug;81(8):870-3
10916004
Seizure. 2002 Jun;11(4):273-7
12027577
J Pediatr. 1995 Aug;127(2):193-9
7543566
AJNR Am J Neuroradiol. 1994 Feb;15(2):277-81
8192073
Dev Med Child Neurol. 2003 May;45(5):320-4
12729146
J Pediatr. 1996 Feb;128(2):302
8636836
Ital J Neurol Sci. 1989 Jun;10(3):291-300
2767936
AJNR Am J Neuroradiol. 1990 Sep-Oct;11(5):1035-40
1699397
J Pediatr. 2000 May;136(5):593-8
10802489
Pediatr Neurosurg. 1998 Nov;29(5):245-9
9917541
J Pediatr. 2000 Nov;137(5):633-7
11060528
Am J Med Genet. 1997 Nov 12;72 (4):468-77
9375733
Am J Med Genet. 1999 Jan 1;82(1):60-6
9916845
Radiology. 1993 Oct;189(1):53-7
7690491