We investigate common pathophysiology in paediatric and adult multiple sclerosis (MS) by comparison of cerebrospinal fluid (CSF) data. We compared cerebrospinal fluid (CSF) data from eight patient groups with onset of MS at 7 to 29 years (n = 184). A new statistics program allows sensitive detection, quantifies the mean amount of intrathecal Ig synthesis in groups based on the 96% reference range of 4100 non-inflammatory controls, corrects for age-related increase of blood-derived albumin and immunoglobulins in CSF, and presents graphical data interpretation in Reibergrams. Already at onset of MS before puberty (< or =10 years) the frequency of intrathecal IgG synthesis (oligoclonal IgG) was 100% like in adults with 98%, but the amount of intrathecal IgG increases twofold during puberty. Intrathecal IgM synthesis is most frequent before and during puberty (in 57-67% of patients) compared with 41% in adults. The amount of intrathecal IgM synthesis before puberty is only 30% of that in adults. IgG and IgM Index are biased evaluations not suitable for characterizing age-related dynamics. A twofold age-related increase of the albumin quotient, Q(Alb), as a measure of the blood-CSF barrier function, represents normal physiological growth. Cell counts in CSF are low. The pre-puberty gender ratio is about 1:1. Intrathecal antibodies against measles, rubella and/or varicella zoster virus are detected in 73% of patients before puberty compared with 89% of adults. Individual paediatric patients (n = 17), with sequential punctures over 2-5 years, show constant quantities of intrathecal IgM and specific antibodies. In conclusion, paediatric MS already at first clinical manifestation shows the complete, neuroimmunological data pattern in CSF, i.e. inflammatory signs are not gradually evolving. Paediatric and adult MS differ quantitatively but not qualitatively in neuroimmunological patterns which does not allow for discrimination between 'early' and 'late' onset MS. CSF analysis may help to discriminate between acute and mono-symptomatic chronic inflammatory disease already at earliest clinical manifestation.