Cortical Thumb Sign

Cortical Thumb Sign

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7-month-old male infant was brought to our attention because of feeding difficulties. In the past 2 months, he had also become more irritable, requiring that he was always held and displaying reduced smiling and interaction with parents. He was born at term via an uncomplicated vaginal delivery, with an adequate weight for gestational age. He had been breastfed for 5 months and had previously shown a normal attainment of developmental milestones. Physical examination revealed axial hypotonia with reduced postural control, spasticity of limbs, and rare spontaneous movements. Hands were kept fisted or open but with persistently clasped thumbs (Figure). Galactocerebrosidase activity in leukocytes was absent (0%). The diagnosis of Krabbe disease, a fatal leukodystrophy resulting from galactosylceramide accumulation in both peripheral and central nervous system myelin sheaths, was confirmed by genetic testing. Adduction and flexion posturing of the thumb (also referred to as “cortical thumb” sign) and fisting are normal findings in term newborns,1 but their persistence beyond 4 months of age, or the presence of a tightly fisted hand that

does not open spontaneously, may be a sign of upper motor neuron injury, as in leukodystrophy or in cerebral palsy, representing essentially an equivalent of a Babinski extensor plantar reflex.2,3 n Federico Poropat, MD Samuele Naviglio, MD Andrea Taddio, MD Giulia Gortani, MD Institute for Maternal and Child Health IRCCS “Burlo Garofolo” University of Trieste Trieste, Italy

References 1. Hua YM, Hung CH, Yuh YS. The occurrence rate and correlation factors of thumb-in-palm posture in newborns. Pediatr Neurol 2000;22:214-9. 2. Jaffe M, Tal Y, Dabbah H, Ganelis L, Cohen A, Even A, et al. Infants with a thumb-in-fist posture. Pediatrics 2000;105:E41. 3. De Vries LS, Dubowitz LM, Dubowitz V, Kaiser A, Lary S, Silverman M, et al. Predictive value of cranial ultrasound in the newborn baby: a reappraisal. Lancet 1985;2:137-40.

Figure. Patient’s hands had persistently clasped thumbs.

J Pediatr 2013;163:605. 0022-3476/$ - see front matter. Copyright ª 2013 Mosby Inc. All rights reserved. http://dx.doi.org/10.1016/j.jpeds.2013.03.020

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