Clinical Reasoning: Juvenile neurocognitive decline: A “snaky” diagnosis

A 13-year-old girl referred from psychiatry had a 3-year history of declining school performance and behavioral change. She was previously a high achiever academically, and was healthy until age 10 years. Over several months, she showed deterioration in schoolwork and became socially withdrawn, culminating in significant intellectual disability requiring resource help and constant supervision. At age 13 years, she presented with a frontally mediated behavior pattern characterized by agitation, poor self-awareness, perseveration of speech and action, impaired working memory, poor sequencing, motor restlessness, and apathy. She also exhibited echolalia, self-mumbling, forgetfulness, and emotional lability. Fine motor skills deteriorated and she was generally clumsy. Medical, birth, and family histories were noncontributory (she had 2 healthy siblings). During examination, she behaved immaturely and was disinhibited and emotionally labile. Examination of outstretched arms revealed subtle myoclonic jerks (video on the Neurology ® Web site at [Neurology.org][1]). Neurologic examination was otherwise normal, including funduscopy. The authors thank Professor S.F. Berkovic, Dr. M. Muona, Dr. Anna-Elina Lehesjoki, and the Helsinki PME group for identification of the SERPINI1 mutation; Dr. Andrew McKeon, Mayo Clinic, Rochester, MN, for paraneoplastic screen; the Neurology team at Temple St. Children's University Hospital, Dublin, Ireland for assistance in management and investigations; and the patient's family for permission to publish this case. [1]: http://neurology.org/lookup/doi/10.1212/WNL.0000000000002180