An unusual case of acute encephalitic syndrome: Is it acute measles encephalitis or subacute sclerosing panencephalitis?

Subacute sclerosing panencephalitis is a late complication of measles infection and develops usually 6 to 15 years after the primary measles infection. Fulminant subacute sclerosing panencephalitis is an infrequently encountered form wherein the disease rapidly progresses to death. A six-year old male child presented with fever, abnormal movements of the left side of body followed by weakness of the left side of the body, and involuntary abnormal movements of right upper and lower limbs. On examination, he was drowsy and was unable to communicate. He had right-sided hemiballismus. He also had left-sided hemiparesis and the left plantar reflex was extensor. Cerebrospinal fluid examination revealed elevated protein and cells. In the serum and cerebrospinal fluid, anti-measles IgG antibodies were found to be positive. No other viral marker was noted in the cerebrospinal fluid. Magnetic resonance imaging of the brain showed extensive damage to the right temporal, parietal, and to a lesser extent, the frontal region as well as subcortical structures of these regions. Electroencephalography revealed generalized slowing of waves. Over a period of the next 3 days, the intensity and frequency of choreiform movements markedly reduced and the patient developed periodic generalized myoclonus, which was predominantly present on the right side. The patient succumbed to his illness and died after one month. Fulminant subacute sclerosing panencephalitis may have unusual clinical manifestations such as hemiballismus. In fulminant subacute sclerosing panencephalitis, neuroimaging may show extensive cortical damage.