Isolated and Asymmetric Basal Ganglia Involvement in Early Subacute Sclerosing Panencephalitis

Neuroimaging does not have an obligatory role in the diagnosis of subacute sclerosing panencephalitis (SSPE) but gives important clues in the clinical assessment and differential diagnosis. Magnetic resonance imaging (MRI) findings in SSPE do not correspond to the clinical stages. In the early stages, MRI findings are normal, or cortical/subcortical asymmetrical hyperintense lesions may be observed in the posterior parts of the brain. As the disease progresses, the lesions disappear and new lesions occur symmetrically in the periventricular white matter in association with mild cortical atrophy.[1,2] The basal ganglia involvement is not common and is usually affected later in the disease course after the cortex has already shown signs of disease. In the cases reported earlier, the basal ganglia involvement was bilateral and symmetric along with white matter changes. We here report a case of SSPE who had isolated and asymmetric basal ganglia involvement without cortical or subcortical lesion.

A 12-year-old girl, born of nonconsanguineous parentage, presented with a history of frequent falls with reduced speech output and forgetfulness for the last 1 month, with sudden extension of head without loss of consciousness for the last 15 days. There was no history of measles in childhood and she was vaccinated for measles. On examination, she was alert but had cognitive impairment. She had generalized myoclonic jerks involving the neck and trunk. The cranial nerve functions were normal, and deep tendon reflexes were exaggerated with intermittent generalized dystonia. Electroencephalography (EEG) showed generalized periodic complexes with asymmetrical background activity [Figure 1]. MRI was performed which showed isolated hyperintensities in left lentiform nuclei on T2-weighted/fluid-attenuated inversion recovery sequences [arrows in Figure 2]. The white matter was normal, and there was no cerebral atrophy. Although MRI brain findings were not classic of SSPE, in view of frequent myoclonic jerks and classical EEG features, SSPE was suspected and confirmed by raised cerebrospinal fluid antimeasles antibody titers (1>:625).

Figure 1.

Electroencephalography of the child showing characteristic long-interval generalized periodic epileptiform discharges in the longitudinal montage characteristic of subacute sclerosing panencephalitis

Figure 2.

(a) T1-weighted axial image of the brain at the level of basal ganglia showing left putaminal hypointensity (black arrows). (b and c) T2-weighted and fluid-attenuated inversion recovery axial image of the brain at the level of basal ganglia showing left putaminal hyperintensity, respectively, with normal white matter (black arrows). (d-f) T2-weighted axial image of the brain at the level of centrum semi-ovale, temporal lobes, and upper midbrain, respectively, showing normal white matter and absence of cerebral atrophy

Neuroimaging in SSPE can be used to know the extent of the disease and for differential diagnosis. In SSPE, basal ganglia lesions are not infrequent, but they tend to appear in patients with advanced clinical states, and/or in those with longer disease duration.[2,3] Apart from the classical progression of MR abnormalities in SSPE, many cases have been reported as early involvement of thalamus, basal ganglia, brainstem, and corpus callosum with cortical or subcortical abnormalities. Praveen-Kumar et al. reported basal ganglionic hyperintensities along with cortical/subcortical changes which were seen in 6% of patients.[4] However, in the cases reported, there is bilateral involvement along with cerebral atrophy and white matter changes. Unilateral and isolated basal ganglia involvement as the initial MRI finding has not been reported earlier in the literature.

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