Speech delays in an otherwise normally developing child can sometimes be caused by oral impairments, like problems with the tongue or palate (the roof of the mouth). A short frenulum (the fold beneath the tongue) can limit tongue movement for speech production.
Many kids with speech delays have oral-motor problems, meaning there's inefficient communication in the areas of the brain responsible for speech production. The child encounters difficulty using and coordinating the lips, tongue, and jaw to produce speech sounds, and hence may even experience difficulties with sucking, swallowing, drinking, or eating. A speech delay may also be a part of a more general developmental delay.
Hearing problems are also commonly related to delayed speech, which is why a child's hearing should be tested by an audiologist as a critical first step whenever there's a speech concern. A child who has trouble hearing may have trouble articulating as well as understanding, imitating, and using language.
Ear infections, especially chronic infections, can affect hearing ability. Simple ear infections that have been adequately treated, though, should have no effect on speech. And, as long as there is normal hearing in at least one ear, speech and language will develop normally.
It’s important to realize that a language delay isn’t the same thing as a speech or language impairment. Language delay is a very common developmental problem. With language delay, children’s language is developing in the expected sequence, only at a slower rate. In contrast, speech and language disorder refers to abnormal language development. Distinguishing between the two is most reliably done by a certified speech-language therapist.
Some causes of speech and language disorders include hearing loss, neurological disorders, brain injury, intellectual disabilities such as Down’s Syndrom, Cerebral Palsy or Autism; drug abuse, physical impairments such as cleft lip or palate, and vocal abuse or misuse. Frequently, however, the cause is unknown. In this case, they are referred to as specific speech or language impairments. Most children with specific speech or language impairments are of normal intelligence, but may have other specific learning difficulties such as dyslexia, dyspraxia or ADHD.