Mental retardation

  • Mental retardation depends on low intelligence quotient (IQ <70, <2SD from mean) and difficulties in adaptive functioning
  • Mild mental retardation IQ 50-70
  • Moderate/severe mental retardation IQ <50
  • ~ 2% population has MR
  • 1.4 M : 1 F


Measures of intellectual, neurodevelopmental, and behavioural progress

  • Developmental tests:
    • Bayley scales of infant development
      • 2nd edition
        • Mental development index (MDI)
        • Psychomotor development index (PDI)
      • 3rd edition
        • Cognitive, language, and motor scales
      • Standardized for 1-42 months
      • Mean = 100, SD = 15
    • Bayley Infant Neurodevelopmental screen (BINS)
      • Standardized for 3-24 months
    • Denver developmental screening test
      • Standardized for birth to 6 years
      • Inventory tests personal-social, language, fine motor-adaptive, and gross motor
  • Intelligence/cognitive tests:
    • Wechsler intelligence scale for children (WISC-IV)
      • 6-17 years
    • Wechsler preschool and primary scale of intelligence (WPPSI-III)
      • 2.5-7.3 years
    • Standford-Binet Intelligence Scales (SB5)
      • 2-85 years
    • Differential Ability Scales (DAS)
    • Leiter International Performance Scale (Leiter-R)
    • Comprehensive Test of Nonverbal Intelligence (CTONI)
  • Neuropsychological tests:
    • NEPSY (NEuro and PSYchology)
    • Delis-Kaplan Executive Function System (D-KEFS)
  • Indirect functional ratings by parent/caregiver
    • Vineland Adaptive Behaviour Scales (Vineland-II)
    • Infant Development Inventory
    • Child Development Inventory
  • Domain-specific developmental measures:
    • Motor profile:
      • Alberta Infant Motor Scale (AIMS)
      • Peabody Developmental Motor Scale (PDMS)
    • Language skills:
      • Peabody Picture Vocabulary Test (PPVT-R)
    • Behaviour and ADLs:
      • Vineland Adaptive Behaviour Scales (Vineland-II)
      • Pediatric Evaluation of Disability Inventory (PEDI)
      • Pediatric Functional Independent Measure (WeeFIM)


Goodenough Draw-a-Person Test

  • Administered to age 3-15 years
  • Told to draw a man, a woman, and themselves
  • Score = 3 + a/4 where a = each feature recorded in the picture


Genetic causes of mental retardation

  • X-linked disorders:
    • Fragile X syndrome
      • FMR1 gene, CGG repeat expansion
        • >200 copies – Fragile X syndrome
        • 55-200 copies – Fragile X-associated tremor/ataxia syndrome (FXTAS)
      • FMR protein involved in protein translation in dendrites
      • Long, narrow face, large protruding ears, macroorchidism, joint laxity
      • 20% have epilepsy
    • Many other X-linked disorders, including ARX, MECP2
  • Chromosomal disorders:
    • Trisomy 21
    • Prader-Willi syndrome
    • Williams’ syndrome
  • Other single-gene mutations:
    • Rubinstein-Taybi
    • Coffin-Lowry
    • Oligophrenin (ORHN1)
    • FMR2
  • Metabolic disorders:
    • PKU
    • Galactosemia
    • Smith-Lemli-Opitz


Acquired causes of mental retardation

  • Prenatal:
    • Fetal alcohol syndrome, other maternal substance abuse
    • Nutritional (materal PKU, iodine deficiency)
    • Infection (rubella, toxoplasmosis, CMV, HIV)
    • Stroke
  • Perinatal:
    • Birth asphyxia
    • Infection (HSV encephalitis, GBS meningitis)
    • Stroke
    • SGA, prematurity
    • Hypoglycemia, hyperbilirubinemia
  • Postnatal/environmental:
    • Toxins (lead)
    • Infection (H. flu b meningitis, arbovirus encephalitis)
    • Stroke
    • Trauma and NAI
    • Poor nutrition, poverty


High-yield tests if no hints to diagnosis

  • Karyotype with high-resolution banding
  • Fragile X mental retardation (FMR1) testing
  • MRI brain



Cognitive syndromes






     Sensory (Wernicke)



     Motor (Broca’s)


     Conduction aphasia


Phonetic errors, phonemic errors, paraphasias


Decreased production and fluency


Poor repetition, normal fluency


Dominant posterosuperior temporal gyrus


Dominant inferior frontal gyrus


Dominant arcuate fasciculus

Alexia with agraphia


Dominant supramarginal and angular gyri


Impaired discrimination, production, repetition of intonation/melody/phrasing

Nondominant perisylvian cortex











Achromatopsia, visual object agnosia, prosopagnosia




Word deafness, amusia


Extinction, neglect


Bilateral occipitaotemporal visual association cortex


Contralateral parietal cortex


Bilateral temporoparietal cortex


Nondominant parietal cortex









Inability to perform learned motor skills


Inability to copy gestures or use tools



Loss of finger dexterity


Dominant inferior parietal cortex


Contralateral and dominant premotor and supplementary motor cortex


Contralateral motor cortex

Gerstmann’s syndrome

Dysgraphia, dyscalculia, right-left disorientation, finger agnosia

Dominant angular gyrus of parietal lobe


Attention-Deficit-Hyperactivity Disorder


Either “inattention” or “hyperactivity-impulsivity”.

Symptoms present before age of 7 years.

Impairment from symptoms in 2+ settings (school, work, home)

Clear evidence of clinically significant impairment in social, academic, or occupational function.


Inattention – 6+ symptoms persistent >6 months that is maladaptive and inconsistent with developmental level

  • Often fails to give close attention to details or makes careless mistakes in schoolwork, work or other
  • Often has difficulty sustaining attention in tasks or play
  • Often does not seem to listen when spoken to directly
  • Often does not follow through on instructions and fails to finish schoolwork, chores, work duties
  • Often has difficulty organizing tasks or activities
  • Often avoids, dislikes, or is reluctant to engage in tasks that require sustained mental effort
  • Often loses things necessary for tasks or activities
  • Often easily distracted by extraneous stimuli
  • Often forgetful in daily activities


Hyperactivity-impulsivity – 6+ symptoms for >6 months that is maladaptive and inconsistent with dev level

  • Often fidgets with hands or feet or squirms in seat
  • Often leaves seat in classroom or other situation where sitting is expected
  • Often runs about or climbs excessively where inappropriate (or feelings of restlessness or adults)
  • Often has difficulty playing or engaging in leisure activities quietly
  • Often “on the go” or acts as if “driven by a motor”
  • Often talks excessively
  • Often blurts out answers before questions have been completed
  • Often has difficulty awaiting turn
  • Often interrupts or intrudes on others (butts into conversations or games)





Side effects & comments




- Dexedrine






Insomnia, anorexia, depression, psychosis, high HR/BP, FTT, withdrawal effects, rebound phenomena

L&D amphetamine

- Adderall







- Ritalin







Mg pemoline

- Cylert






Rare, serious hepatotoxicity (check LFTs)




- Concerta

- Ritalin LA







L&D amphetamine

- Adderall XR









- Strattera






Mild anorexia, GI symptoms, mild high BP/HR. Jaundice, high LFTs, suicidal thinking

May be helpful with comorbid enuresis, tics, mood disorders


TCAs (imipramine, amitryptyline). SSRIs (fluoxetine, citalopram), Buproprion, Venlafaxine for ADHD and comorbid tics, OCD, mood disorders.


Alpha-agonist (clonidine) for tics, ADHD, aggression, agitation, withdrawal.


Beta-blockers (propranolol) for aggression, agitation, akathisia.


Nonpharmacological therapies include:

  • Mimization of distractions (front row, uncluttered desk, minimal distractions)
  • Structure, organization techniques (checklists, homework assignment pads)
  • Biofeedback, complimentary/alternative therapies

Tic disorders


Transient tic disorder – duration of tics <1 year

Chronic tic disorder – duration of tics >1 year of one type (motor, vocal)


Tourette syndrome – diagnostic criteria

  • Multiple motor and at least one vocal tic
  • Waxing and waning course
  • Onset before age 21 years
  • No precipitating illness or medication


Features of Tourette syndrome

  • 3M : 1F
  • Mean onset 6-7 years
  • Soft neurological signs of coordination and fine motor difficulties, synkinesis, restlessness
  • Often associated with other neuropsychiatric disorders, e.g., OCD, ADHD, depression/anxiety, episodic rage/self-injurious behaviour, academic difficulties, executive dysfunction.


PANDAS – Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal infection

  • Prepubertal onset
  • Tic disorder or obsessive-compulsive disorder
  • Acute fulminant onset
  • Associated with group A beta-hemolytic streptococcal infusion
  • Associated with neurological abnormalities


Nonpharmacological therapies:

  • Behavioural treatments (habit reversal training, support groups, relaxation therapy)
  • Acupuncture


Pharmacological therapies:

  • Tier 1 medications (milder tics)
    • Clonidine
    • Guanfacine
    • Baclofen
    • Clonazepam
    • Others: gabapentin, topiramate, levetiracetam
  • Tier 2 medications (more severe tics)
    • Typical and atypical neuroleptics
    • Pimozide, fluphenazine, risperidone, olanzapine, haloperidol, etc
    • Pergolide, donepezil
    • Botulinum toxin, nicotine patch, delta-9-tetrahydrocannabinol (special cases)
  • Experimental:
    • Transcranial magnetic stimulation
    • Deep brain stimulation


Goal is to minimize tics’ to limit psychosocial effects, not completely rid of tics.


Autistic spectrum disorders

Pervasive developmental disorders

  • Autistic disorder
  • Asperger’s disorder
  • Childhood disintegrative disorder
  • Rett’s disorder


Autistic disorder (DSM-IV criteria)

  • 6+ items
    • Impaired social interaction (2+ of these)
      • Impaired nonverbal behaviors (eye gaze, facial expression, body posture, gestures
      • Failure to develop appropriate peer relationships
      • Lack of spontaneous seeking to share enjoyment, interests, achievements with others
      • Lack of social or emotional reciprocity
    • Impaired communication (1+ of these)
      • Delayed language (including gestures)
      • Impaired ability to initiate or sustain conversation
      • Stereotyped/repetitive language or idiosyncratic language
      • Lack of varied, spontaneous make-believe or appropriate social imitative play
    • Restrictive repetitive and stereotypic patterns of behaviour, interests, activities:
      • Preoccupation with stereotyped or restricted patterns of interest
      • Inflexible adherence to nonfunctional routines/rituals
      • Stereotyped/repetitive motor mannerisms (hand flapping, twisting movements)
      • Preoccupation with parts of objects
  • Delayed/abnormal function in 1+ of these areas before age 3 years:
    • Social interaction
    • Language in social communication
    • Symbolic/imaginative play
  • Not Rett’s or childhood disintegrative disorder


Asperger’s disorder

  • Normal IQ (no language delay), normal self-help skills, curiosity about environment
  • Impairments in social interaction and restrictive/repetitive patterns of behaviour/actiivites
  • Difficulty forming friendships due to naïve, inappropriate, one-sided social interactions, lack of empathy
  • Desire success in interpersonal relationships and are puzzled by the failure
  • Discrepant verbal & nonverbal IQ scores (as opposed to in autism)


Childhood disintegrative disorder

  • Rare
  • Normal early development
  • Neurodevelopmental regression after 24 months, leading to autistic symptoms
  • Onset from 3-10 years (usually 3-4 years)
  • Profound cognitive regression to mental retardation
  • 4M : 1F


Rett’s syndrome

  • X-linked dominant, male lethal – MECP2 – methyl-CpG-binding protein 2 – regulates gene expression
  • Neurodegenerative disorder, usually females, onset after period of normal development
  • Reduced life expectancy (70% survive to 35 years)
  • Must have had:
    • Normal prenatal/perinatal development
    • Normal psychomotor development until 5 months age
    • Normal birth head circumference
  • Onset of these after period of normal development:
    • Decelerated head growth from 5-48 months
    • Loss of purposeful hand skills, development of stereotyped hand movements
    • Loss of social engagement early on (interaction often develops later)
    • Poorly coordinated gait/trunk movements
    • Severely impaired expressive/receptive language, severe psychomotor retardation
  • Symptoms later become relatively static
  • Inconsolable crying, screaming, agitation, food refusal
  • Breathing irregularities
    • Periodic apnea during wakefulness
    • Intermittent hyperventilation
  • Seizures, EEG abnormalities
  • Scoliosis, growth retardation, small feet
  • Atypical Rett syndrome
    • XY – severe epileptic encephalopathy
    • XXY – classic Rett phenotype
    • XY – mental retardation
    • XX – classic autistic disorder


Screening tests for ASD:

  • Checklist for Autism in Toddlers
  • Screening Tool for Autism in Two-year-Olds
  • Pervasive Developmental Disorders Screening Test (PDDST-II)
  • Social Communication Questionnaire


Diagnostic tests for ASD:

  • Childhood Autism Rating Scale (good clinical tool)
  • Autism Diagnostic Interview-Revised (ADI) – gold standard
  • Autism Diagnostic Observation Schedule-General (ADOS) – gold standard


Investigations in ASD:

  • Auditory testing or ABRs
  • Lead level if pica
  • Metabolic testing only if other clinical or physical signs
  • Neuroimaging not needed in autism and macrocephaly


Coexisting medication disorders:

  • Feeding and GI problems
  • Sleep disturbances
  • Epilepsy
  • Mitochondrial disorders
  • PKU
  • Fragile X
  • Tuberous sclerosis complex
  • Neurofibromatosis
  • Prader-Willi syndrome
  • Angelman syndrome
  • Smith-Lemli-Opitz syndrome


Psychiatry and nonorganic disorders


Somatiform disorders

  • Symptoms linked to psychological factors, but not under voluntary control or consciously produced
  • Conversion disorder – psychological factors primary role
  • Somatization disorder – recurrent, multiple complaints over many years, unrelated to physical disorder


Factitious disorder – intentionally produced due to psychological need, often with personality disorder


Malingering – voluntary produced physical symptoms in persuit of a goal, e.g, financial, legal