Pulvinar sign in acute disseminated encephalomyelitis.

Case Report

A 20-year-old lady presented with fever of 5 days duration followed by headache and drowsiness. Over next 2 days, she was noticed to have weakness of both lower limbs and distal upper limbs, tingling in the limbs and trunk below neck and retention of urine requiring catheterization. On examination, she was drowsy, had lower limb weakness of grade 3/5, upper limb distal weakness of grade 4/5, and sensory impairment below D1 (first dorsal spinal cord segment) level. Her deep tendon reflexes were normal in upper limbs and absent in lower limbs and plantar response was extensor bilaterally. She was evaluated with magnetic resonance imaging (MRI) of the brain and spinal cord which showed bilaterally symmetrical hyperintense signal changes on T2-weighted and fluid-attenuated inversion recovery (FLAIR) sequences in medial and posterior thalami without any enhancement on contrast [Figures 1 and 2]. MRI of the spinal cord showed diffuse ill-defined hyperintense signal on T2-weighted image without any cord swelling or contrast enhancement [Figures 3 and 4]. Cerebrospinal fluid analysis showed total 7 cells/mm3 predominantly lymphocytes, protein 76 mg/dl, sugar 61 mg/dl, and no oligoclonal bands. Testing for tubercular bacilli on CSF by acid fast staining and polymerase chain reaction was negative. Serological testing for antinuclear antibody (ANA), anti-Ro antibody, anti-La antibody, and antineuromylitis optica (anti-NMO) antibody was negative. Her erythrocyte sedimentation rate (ESR) was 55 mm in 1st h. Serological testing for human immunodeficiency virus (HIV), hepatitis B virus (HBsAg), and dengue virus (immunoglobulin (Ig)G, IgM, and NS1 antigen) was negative. Other parameters of blood counts and urine examination were within normal limits. The chest X-ray and ultrasonography of the abdomen and pelvis were normal. Based on the clinical picture, imaging findings, and after ruling out other possible etiologies a final diagnosis of acute disseminated encephalomyelitis (ADEM) was made. She was given injection methylprednisolone 1 g daily for 5 days and patient showed good response to that in terms of sensorium, motor functions, sensory symptoms, and bladder dysfunction. Patient at the time of peak neurological deficits was drowsy, quadriparetic, and bed ridden with indwelling catheter. After treatment patient was alert, self-ambulant with minimal imbalance, and had no bladder symptoms. She was put on tapering course of oral prednisolone and was maintaining improvement at 2 week follow-up.

Figure 1

Magnetic resonance imaging (MRI) fluid-attenuated inversion recovery (FLAIR) axial image of the brain showing symmetrical hyperintensity in bilateral pulvinar nuclei of the thalamus

Figure 2

MRI T2-weighted axial image of the brain showing symmetrical hyperintensity in bilateral pulvinar nucluei of the thalamus

Figure 3

MRI T2-weighted sagittal image of the cervical spine showing hyperintense intramedullary cord signal changes throughout the cervical and upper dorsal spinal cord

Figure 4

MRI T2-weighted sagittal image of the dorsolumbar spine showing hyperintense intramedullary cord signal changes throughout the dorsal and lumbar spinal cord

Discussion

Pulvinar nucleus is the largest nucleus in the thalamus and is situated at the caudal extremity of the thalamus. Signal changes in pulvinar on MRI were noted initially in case reports of patients with variant Creutzfeldt-Jakob disease (CJD) and subsequently consistent correlation of this finding prompted the recognition of this abnormality on MRI as pulvinar sign.[1] Pulvinar sign on MRI is considered to be a strong indicator of variant CJD in an appropriate clinical context. For the diagnosis of variant CJD, World Health Organization defined this sign as “a characteristic distribution of symmetrical hyperintensity (relative to the cortical and other deep grey matter nuclei signal intensity) of the pulvinar nucleus (posterior nucleus) of the thalamus seen on axial images”.[2] The possible explanation for the signal change on MRI in CJD is astrocytosis.[1] The pulvinar sign has also been reported in a number of other diseases [Table 1].

Table 1

Conditions in which “pulvinar sign” has been reported in literature

In our case, in addition to pulvinar sign, our patient also had spinal cord signal changes along with clinical features of myelopathy. In view of long segment myelitis, we also considered differentials of neuromyelitis optica (NMO), Sjogren's syndrome, systemic lupus erythematosus, and tubercular myelitis which were ruled out by appropriate investigations. Since our patient had acute onset multifocal CNS involvement with polysymptomatic clinical presentation including encephalopathy and compatible MRI findings; therefore, she met diagnostic criteria for ADEM proposed by international pediatric multiple sclerosis study group.[12] She responded well to the high dose intravenous methylprednisolone as expected in ADEM. In ADEM characteristic lesions seen on MRI appear as patchy areas of increased signal intensity on conventional T2-weighted images and on FLAIR sequence. Though white matter involvement predominates grey matter can also be affected, particularly basal ganglion, thalami, and brainstem.[13]

Pulvinar sign has rarely been reported as a radiographic feature in ADEM.[6] Though the sign is not specific for ADEM, the recognition of pulvinar sign in an MRI of the brain should definitely arouse suspicion of the same apart from other differentials.