A 1-year-old girl was brought in for evaluation of her developmental delay and regression of achieved milestones. Born full-term, she was the first child of a nonconsanguineous couple. The antenatal and perinatal history was unremarkable. She achieved social smile at 4 months and neck control at 6 months. She had just begun to sit with support at 9 months of age, when her parents noticed an exaggerated startle response to noise. Subsequently, she became listless and irritable and lost her sitting ability and neck control. She also developed reduced eye contact. Examination revealed a well, thriving infant with a weight of 9 kg, a length of 75 cm, and a head circumference of 47.5 cm. Facies were normal. Central nervous system examination revealed reduced alertness; absent menace response; reduced tone in all 4 limbs; brisk, deep tendon reflexes; and extensor plantar response bilaterally. Fundus examination showed bilateral cherry-red macular spots. Results of a systemic examination were normal.
Sharma S, Sankhyan N, Kalra V, Garg A. Thalamic Changes in Tay-Sachs' Disease. Arch Neurol. 2008;65(12):1669. doi:10.1001/archneur.65.12.1669