Journal of the Neurological Sciences 167 (1999) 132–136 Long term MRI follow-up of patients with post infectious encephalomyelitis: evidence for a monophasic disease a b b a, * J.I. O’Riordan , B. Gomez-Anson , I.F. Moseley , D.H. Miller a NMR Research Unit, The Institute of Neurology and National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, UK b Lysholm Department of Neuroradiology, The National Hospital of Neurology and Neurosurgery, Queen Square, London WC1N 3BG, UK Received 12 October 1998; received in revised form 25 June 1999; accepted 29 June 1999 Abstract Post infectious encephalomyelitis and multiple sclerosis are both inflammatory demyelinating disorders of the central nervous system. Whereas multiple sclerosis is a multi phasic disease with recurrent episodes disseminated in time and place, post infectious encephalomyelitis is usually considered to be a monophasic illness. This study used serial brain MRI to clarify whether the latter hypothesis holds for the long term. Post infectious encephalomyelitis was defined as the development of a central nervous system white matter disorder occurring in close temporal relationship with a viral, bacterial or other infection. There were eleven patients, mean age at presentation 21 years (4–48), and mean period of follow-up of 8 years (3.5–11). T2-weighted brain MRI was abnormal in all 11 cases during the acute stages of the illness. On follow-up 6 patients had made a complete clinical recovery, 4 patients had mild residual deficits and one severe neurological deficits necessitating ventilatory support. No patient experienced an exacerbation during the follow-up period. MRI revealed complete resolution of abnormalities in 3 and partial resolution in 7; new white matter lesions were seen in only one patient. This long term follow-up study suggests that there is a definable group with post infectious encephalomyelitis who exhibit a monophasic clinical and MRI pattern in the long term.  1999 Elsevier Science B.V. All rights reserved. Keywords: Post infectious encephalomyelitis; Multiple sclerosis 1. Introduction tem. However, whereas post infectious encephalomyelitis is considered a monophasic illness, multiple sclerosis is Post infectious encephalomyelitis is a central nervous not and results in recurrent episodes disseminated in both system inflammatory demyelinating disorder developing time and place. This has obvious prognostic implications acutely or subacutely in close temporal relationship to an for the patient but also therapeutic considerations for the infective illness [1–3]. It has a close resemblance to the physician in view of the development of specific disease encephalomyelitis that rarely follows vaccination. The modifying therapy for multiple sclerosis [6,7]. disease is usually disseminated with a particular predilec- Clinical reports of cases of acute disseminated en- tion to both optic nerves, the spinal cord, brain stem or cephalomyelitis – defined as those patients with en- diffuse symmetrical involvement of the basal ganglia or cephalomyelitis following a vaccination or an infective cerebral and cerebellar hemispheres [3–5]. There are illness and sometimes including those with presentations clinical and pathological similarities between post infecti- considered atypical for multiple sclerosis highlight the ous encephalomyelitis and multiple sclerosis. Both are difficulties in distinguishing it from MS. Follow-up sug- demyelinating diseases affecting the central nervous sys- gests that the majority are indeed monophasic, but that relapsing forms may exist and some may convert to clinically definite multiple sclerosis [1,3]. It is possible that *Corresponding author. Tel.: 144-171-837-3611; fax: 144-171-278- 5616. patients with a disseminated multifocal presentation of 0022-510X / 99 / $ – see front matter  1999 Elsevier Science B.V. All rights reserved. PII: S0022-510X(99)00160-4