<prompt> Commonest cause of head banging in children areRaised intracranial tensionMental retardationHeadacheMeningeal irritation  <response>: Ans. b Mental retardation. Ref. Nelson, 18th116HABIT DISORDERSHead bangingNail biting Body rocking Hair pulling trichotillomania Tnumb sucking Teeth grinding bruxismHittingbiting own body Body manipulations Repetitive vocalizationsAerophagia air swallowing Tics Certain habit disorders are more common in children with developmental delays, particularly those with pervasive devel- opmental disorders. Self-injurious habits, such as self-biting or head banging, can occur in up to 25 of normally developing toddlers, but are almost invariably associated with developmental delays in children older than 5 yr.NOTE: Pediatric autoimmune neuropsychiatric disorder associated with streptococcal infection PANDAS is a condition in which antibodies to group A streptococcus cross react with basal ganglia tissue. 