Authors' reply.

Sir,

We appreciate the comments made by Radhakrishna[1] and colleagues and would like to clarify few of the concerns raised by them. Childhood multiple sclerosis (MS) was not seen in our series with 15 patients of childhood inflammatory demyelinating disorders (CIDD). We fully agree that there is a need to follow the cases with the diagnosis of clinically isolated syndrome (CIS) for possible evolution into MS. We are following-up these patients every 6 months for possible recurrence of deficits or occurrence of new symptoms. This is one of the advantages of the new consensus definition as it separates Acute disseminated encephalomyelitis (ADEM) from CIS.[2] Previously, both of these were clubbed under ADEM. Patients with a diagnosis of CIS need a close follow-up as these patients, when compared with a diagnosis with ADEM, are at a higher chance of developing MS at follow-up. Although the concept of recurrent ADEM existed earlier, there was a lot of ambiguity in use of terms like recurrent ADEM, relapsing ADEM and multiphasic ADEM. The new consensus definition has cleared the confusion and given clear guidelines to the use of these terms. Uniform use of the consensus definition by all those involved in the treatment of CIDD would help in taking up large follow-up and therapeutic trials in patients with CIDD.

Coming to inclusion of one patient with HIV and ADEM in our series, we agree that progressive multifocal leucoencephalopathy (PML) was a possibility, although the normal premorbid state, short aggressive clinical profile, recent seroconversion of the patient and absence of opportunistic infections made us label it as ADEM. Specific polymerase chain reaction (PCR) tests for JC virus could not be carried out. There are reports of ADEM occurring in primary HIV infection.[34] Because of similar findings, a differentiation of ADEM from PML may be impossible on the basis of magnetic resonance imaging features alone.[5] Clinical and laboratory information is necessary. However, we do admit that in the absence of PCR for JC virus results, the possibility of PML cannot be ruled out in that particular patient, although it appeared unlikely.