Diagnostic yield of the comprehensive assessment of developmental delay/mental retardation in an institute of child neuropsychiatry

Am J Med Genet. 1999 Jan 1;82(1):60-6.


The Consensus Conference of the American College of Medical Genetics has established guidelines regarding the evaluation of patients with mental retardation (MR) [Curry et al., Am. J. Med. Genet. 72:468-477, 1997]. They emphasized the high diagnostic utility of cytogenetic studies and of neuroimaging in certain clinical settings. However, data on the diagnostic yield of these studies in well-characterized populations of individuals with MR are scant. Majnemer and Shevell [J. Pediatr. 127:193-199, 1995] attained a diagnostic yield of 63%. However, this study included only 60 patients and the classification included pathogenetic and causal groups. The Stella Maris Institute has evaluated systematically patients with developmental delay (DD)/MR and performed various laboratory studies and neuroimaging in almost all patients. We report a retrospective analysis of the diagnostic yield of 120 consecutive patients observed at our Institute during the first 6 months of 1996. There were 77 males and 43 females; 47 were mildly delayed (IQ 70-50), 31 were moderately delayed (IQ 50-35), and 42 were severely delayed (IQ 35-20). Diagnostic studies (history, physical examination, standard cytogenetics, fragile X testing, molecular studies, electroencephalography, electromyography, nerve conduction studies, neuroimaging, and metabolic screening tests) yielded a causal diagnosis in 50 (41.6%) and a pathogenetic diagnosis in 47 (39.2%) of the 120 patients. Causal categories included chromosomal abnormalities (14), Fra(X) syndromes (4), known MCA/MR syndromes (19), fetal environmental syndromes (1), neurometabolic (3) disorders, neurocutaneous (3) disorders, hypoxic-ischemic encephalopathy (3), other encephalopathies (1), and congenital bilateral perisylvian syndrome (2). Pathogenetic categories included idiopathic MCA/MR syndromes (35), epileptic syndromes (10), and isolated lissencephaly sequence (2). Diagnostic yield did not differ across categories and degree of DD. Our results, while confirming the diagnostic utility of cytogenetic/molecular genetic, and neuroimaging studies, suggest the usefulness of accurate electroencephalogram recordings, and stress the importance of a thorough physical examination. Referral to a university child neurology and psychiatry service, where a comprehensive assessment with a selected battery of investigations is possible, yields etiologic findings in a high percentage of DD/MR patients, with important implications for management, prognosis and recurrence risk estimate.

MeSH terms

  • Adolescent
  • Child
  • Child Psychiatry / methods
  • Child Psychiatry / standards*
  • Child, Preschool
  • Chromosome Aberrations / diagnosis
  • Chromosome Disorders
  • Cohort Studies
  • Developmental Disabilities / diagnosis
  • Developmental Disabilities / etiology*
  • Developmental Disabilities / genetics
  • Environmental Exposure
  • Female
  • Fragile X Syndrome / diagnosis
  • Hospitals, Psychiatric
  • Humans
  • Intellectual Disability / diagnosis
  • Intellectual Disability / etiology*
  • Intellectual Disability / genetics
  • Intelligence Tests
  • Male
  • Neurology / methods
  • Neurology / standards*
  • Pregnancy
  • Pregnancy Complications
  • Retrospective Studies
  • Syndrome