Teaching Case

54-year-old lady presented to our hospital with complaints of altered sensorium and inability to move all four limbs. Prior to developing these symptoms, she had a fever for 5 days which subsided on taking antipyretics. On clinical examination, Glasgow Coma Scale was E2 V1 M1.

Non-contrast CT scan of brain showed subtle confluent hypodensities in dorsal pons and bilateral middle cerebellar peduncles.

Non-contrast MRI of the brain revealed few patchy T2/FLAIR hyperintensities in bilateral periventricular white matter and nearly symmetric T2/FLAIR hyperintensities in bilateral internal capsule, dorsal mid brain, pons and middle cerebellar peduncles. No diffusion restriction or haemorrhage was seen. No imaging features of optic neuritis were seen.

Non-contrast MRI of the cervical spine was done which revealed mild spinal cord expansion with long segment intramedullary T2/STIR hyperintensity involving nearly the entire cross-section of spinal cord from C2 to C7 levels, suggesting longitudinally extensive transverse myelitis.

Imaging findings were suggestive of demyelinating aetiology.

Acute disseminated encephalomyelitis [ADEM] is an immune-mediated demyelinating disorder affecting brain and spine. It usually occurs following viral infection or vaccination [1]. It is mostly monophasic, however multiphasic variant of ADEM similar to multiple sclerosis have been described. Initial signs and symptoms of ADEM usually begin within 2 days to 4 weeks of prior vaccination or viral infection [2].

MRI is the most sensitive investigation and the abnormalities are best seen using T2 weighted and fluid-attenuated inversion recovery [FLAIR] sequences. The acute lesions can show variable post-contrast enhancement and diffusion restriction. White matter lesions associated with ADEM are typically bilateral, asymmetric and poorly marginated involving the subcortical white mater more than periventricular white mater [3]. Involvement of basal ganglia and thalami is common and lesions tend to be symmetrical [4]. Brain stem and spinal cord involvement is also common. Spinal cord lesions usually extend over multiple segments [4]. Sequential MR imaging is sometimes needed to confirm the diagnosis of ADEM, as presence of newer lesions suggests alternative diagnoses like multiple sclerosis.

In our case the laboratory investigations showed positive IgM antibody test for Orientia tsutsugamushi. Cerebrospinal fluid analysis showed elevated CSF protein and lymphocytic pleocytosis. CSF study for aquaporin antibody, oligoclonal bands and myelin oligodendrocyte [MOG] antibody were negative.

Scrub typhus is a gram-negative bacterial disease caused by Orientia tsutsugamushi. It spreads through bites of infected mites. It is endemic in some parts of India and is kept as a differential in cases of pyrexia of unknown origin. Signs and symptoms include fever with chills, headache, eschar at the site of mite bite, lymphadenopathy, encephalopathy to severe multiorgan failure. Acute disseminated encephalomyelitis following scrub typhus infection is a rare manifestation. Only a few cases have been described in literature; Chen et al. described a case of ADEM following scrub typhus infection with extensive periventricular white matter lesions [5].

In our case, lesions involved periventricular white matter, basal ganglia, brain stem, cerebellar peduncles and cervical spinal cord. The clinical signs and symptoms of the patient improved dramatically following treatment with methylprednisolone and doxycycline. Sequential MR imaging could not be done due to financial constraints of the patient.

Written informed patient consent for publication has been obtained.