A 13-year-old previously healthy Iraqi-born unvaccinated immigrant boy presented with a one-year history of worsening vision loss. Over the course of 2 months, he developed myoclonic jerks involving all extremities that increased in frequency over the next few months, occurring every 10 seconds. In addition, he had atonic episodes resulting in him falling to the floor. He had difficulty with fine motor movements, including writing and putting on clothes. Over several months, he progressed to being unable to ambulate independently. He had frequent urinary incontinence. His memory and performance in school began to decline, first gradually and then more rapidly after 6 months. He started to have aggressive outbursts towards his family with behaviors such as hitting and biting. His mother reported a febrile illness associated with a rash as a toddler without confirmation of measles.
Initial exam demonstrated decreased visual acuity in the right eye (20/200) and left eye (20/40) and frequent myoclonic jerks. He had evidence of macular retinopathy on fundoscopic evaluation. On mental status examination, he showed progressive impairment with simple multiplication and difficulty with recall and comprehension. He had difficulty with orientation questions. On cranial nerve examination, he had sluggish poorly reactive pupils to direct light bilaterally with normal reactivity on convergence and an oculomotor apraxia. He had diffuse spasticity of both upper and lower extremities with diffuse hyperreflexia. Coordination exam revealed a progressive resting and action tremor bilaterally and an unsteady, wide-based gait.
EEG showed significant frontal slowing during the awake state as well as recurrent periodic generalized periodic epileptiform discharges with preservation of his posterior basic rhythm (Figure 1) that raised suspicion for a diagnosis of a progressive myoclonic epilepsy included in the differential diagnosis: baltic myoclonic epilepsy, Lafora body disease, Unverricht-Lundborg disease, neuronal ceroid lipofuscinosis, sialidosis, myoclonic epilepsy with ragged red fibers, and SSPE.
Following an extensive negative metabolic and infectious workup of serum and CSF samples, the diagnosis of subacute sclerosing panencephalitis was confirmed by elevated serum measles IgG (22.4) and CSF measles IgG (12.0) titers.