Genetic and physiological. Language disorders are highly heritable, and family mem-
bers are more likely to have a history of language impairment.
Differential Diagnosis
Normal variations in language. Language disorder needs to be distinguished from nor-
mal developmental variations, and this distinctio n may be difficult to make before 4 years
of age. Regional, social, or cultural/ethnic va riations of language (e.g., dialects) must be
considered when an individual is being assessed for language impairment.
Hearing or other sensory impairment. Hearing impairment needs to be excluded as the
primary cause of language difficulties. Langua ge deficits may be associated with a hearing
impairment, other sensory deficit, or a speech-motor deficit. When language deficits are in
excess of those usually associ ated with these problems, a di agnosis of language disorder
may be made.
Intellectual disability (intell ectual developmental disorder). Language delay is often the
presenting feature of intellect ual disability, and the definitive diagnosis may not be made
until the child is able to complete standard ized assessments. A separate diagnosis is not
given unless the language deficits are clearl y in excess of the intellectual limitations.
Neurological disorders. Language disorder can be acquired in association with neuro-
logical disorders, including epilepsy (e.g., ac quired aphasia or Landau-Kleffner syndrome).
Language regression. Loss of speech and language in a child younger than 3 years may
be a sign of autism spectrum disorder (with developmental regression) or a specific neuro-
logical condition, such as Landau-Kleffner syndrome. Among children older than 3 years,
language loss may be a symptom of seizures, and a diagnostic assessment is necessary to
exclude the presence of epilepsy (e.g., routine and sleep electroencephalogram).