Download Mental Retardation

Mental Retardation
Contents :
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Definition
Prevalence
Classification
Causes
Clinical Evaluation
Investigation
Management
Definition
Mental Retardation is defined statistically as
tested cognitive performance that is two
standard deviation below the mean of the
general population ( roughly below the 3rd
percentile )
The Classical definition comprises 3
components :
1- subaverage intellectual function .
2- that result from an injury , disease or
abnormality before the age of 18 years .
3- resulting in impaired ability to adapt to
the environment .
Prevalence :
Mental retardation is present in about 2 to
3% of the population.
AAMR Classification Scheme
IQ classification:
I.Q.(intelligence quotient) is 100; normal ranges from 90 to 110
1-Border line { IQ 70-80 }
2-mild MR
{ IQ 55-70 }
3-moderate MR{ IQ 40-55 }
4-sever MR
{ IQ 25-40 }
5-profound MR { IQ below 25 }
Etiology
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Unknown “ 30-40 % “
Genetic “ 5% “
Early embryonic ( prenatal ) “ 30% “
Prematurity , IUGR (perinatal) “ 10 % “
Acquired medical condition (trauma ,
infection ..) “ 5% “
Environment “ 5-20% “
Etiology classification :
 Prenatal
 Perinatal
 Postnatal
Prenatal causes :
»Genetic Disorders :
Fragile X syndrome FXS :most common cause .
Klinefelter syndrome :male with extra x chromosome 47,XXY
Down syndrome :
Meabolic disorders: PKU, Tay-sachs, Galactosemia
Skin disorders : neurofibromatosis and Tubererous sclerosis .
Prader-Willi Syndrom :
Endocrine : hypothyroidism
Fragile X syndrome (FXS)
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Is the commonest cause of MR.
The incidence has been estimated at
approximately 1 in 1,500 males and 1 in
2,500 females.
Mutation of a gene on the long arm of the
X chromosome is responsible for FXS and
involves instability of trinucleotide repeat
sequence .
DNA-analysis of the FMR-I gene is the best
way to diagnose which is usually done on
lymphocytes.
Fragile X syndrome (FXS)cont..
C/P: { phenotype } 
Large ears , Large testes (testicular 
volume>30 ml in adults) , Plantar crease ,
Hyperextensible joints , Simian crease,
Broad forehead, Increased hand width, 
Increased hand length , Elongated face,
High arched palate ,
Mitral valve prolapse , Hypotonia , Hernia,
Double jointed thumbs , Scoliosis and Flat
feet
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Fragile X syndrome (FXS)cont..
C/P: {NEUROCOGNITIVE } 
Mental retardation , Hyperactivity , 
Attentional problems , Language delays ,
Hand flapping , Hand biting , Irritability ,
Perseveration , Excessive temper tantrums
Gaze avoidance , Sensory aversion , Selfstimulatory behavior and Autism
»Cranial Malformations :
Anencephaly :
microcephaly :
Hydrocephaly :
»Congenital Factors :
Maternal : Rubella , congent. Syphilis & Rh incompitability
Toxins : drugs , fetal alcohol syndrom ..
Perinatal Causes :
 Low Bwt :
premature , teen pregnancy , poor nutrition ..
21 % with MR
Birth Anoxia :
breech presentation , knotted umbilical cord.
Postnatal Causes :
Child abuse and neglect :
Traumatic brain injury :
Infection : meningitis and encephalitis
Nutritional deficiencies :
Cultural and familial :
Clinical Evaluation
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Complete History :
Examination :
History
»complete and detailed history«
complete systemic review
surgical history : trauma , accidents
medical illnesses : hospitalization , general heath
pregnancy history : maternal age , parity , infections..
birth : type , wt . GA ,complications , apgar score
Postnatal : incubator , ventilator , disease ..
History (cont.)
drugs: mother and child
developmental Hx : mile stones , loss it , speech ..
educational Hx : schooling , IQ tests
behavioral Hx : skills , attention , activity
family Hx : consanguinity , inherited ds ..
social Hx :
Examination
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»complete and detailed examination«
Growth parameters :
Dysmorphic features :
CNS examination :
Other system and skin exam :
IQ tests :
Developmental testing :
Investigations
»» there is no specific investigation for MR
but good hx and physical examination
guide us toward the proper one ««
 DNA analysis: chromosomes
 FISH probes: Prader-willi,wiliams,cri du chat syndrom
 Metabolic labs:plasma a.a. , urine organic a. ,TFT , ck
 Imaging : brain MRI , CT , skeleton films
 Psychological Assesment:
 Electrophysiology : EEG , auditory & visual evoked potentials
When to do the investigations?
Cytogenetic studies if: 
Microcephaly
Multiple (even minor) somatic anomalies
Family history of mental retardation
Family history of fetal loss
IQ <50
Skin pigment anomalies (mosaicism)
Suspected contiguous gene syndromes (e.g.,
)Prader-Willi, Angelman, Smith-Magenis
Metabolic studies if : 
Episodic vomiting or lethargy
Poor growth
Seizures
Unusual body odors
Somatic evidence of storage disease
Loss or plateau of developmental skills
Movement disorder (choreoathetosis, dystonia, ataxia)
Sensory loss (especially retinal abnormality)
Acquired cutaneous disorders
MRI of the brain if : 
Cerebral palsy or motor asymmetry
Abnormal head size or shape
Craniofacial malformation
Loss or plateau of developmental skills
Multiple somatic anomalies
Neurocutaneous findings
Seizures
IQ <50
Management of MR
»» there is no specific Rx for MR ««
»General rules :
-Identify the cause then initiate a
comprehensive plan
-Special educator , Language , behavioral
and occupational therapists
-Special school programs
-Community services