Bilateral enlargement of caudate nucleus in a child with polymicrogyria

Introduction:

The caudate nucleus (CN) receives connections from all major ipsi- and contralateral cortical regions. The embryologic development of corticostriatal neurons and of striatal and cortical interneurons is still under investigation. In mice, an interaction between neuron migration to the cortex and striatum has been described in early development [1]. In cats, a CN enlargement has been reported following prenatal cortical lesioning [2]. In humans, corticostriatal connections are thought to be involved, apart from Parkinson and Huntington disease, in autism and psychiatric diseases [3]. A recent study showed striatal histological abnormalities additional to focal cortical dysplasia in children with epilepsy [4].

Case:

We report a 6-year-old girl with an extensive brain malformation including the CN, which presented esotropia, trunk hypotonia and limb dystonia in early life. At the age of 5 years, anticonvulsant treatment with valproic acid was commenced due to suspicion of epilepsy. A long-term video-EEG recording in our institution at the age of 5 years and 8 months finally provided no evidence for epileptic seizures. The brain MRI showed bilateral deep parietooccipital polymicrogyric sulci, subependymal heterotopia as well as shape and volume alterations of the CN. Its head and anterior body was enlarged and the posterior body reduced in volume, without a substantial alteration in its total CN volume. A glucose-PET-CT showed no further abnormalities/asymmetries.

Discussion:

Polymicrogyria is associated with other brain malformations, such as grey matter heterotopia in our patient. This is the first report of a coexisting striatal malformation in form of an enlargement. This can be appreciated as analogous to CN enlargement emerging after cortical lesioning during embryogenesis in cats [2]. The fetal kittens were lesioned in the second trimenon, analogous to the stage of embryogenesis, when polymicrogyria is thought to occur [5]. The increase of CN size may theoretically be due to a decrease in apoptosic signaling or an additional neuron migration to the CN and remains to be clarified.

Fig. 1: axial (left) and coronal (right) T2-weighted images of our patient showing caudate nucleus enlargement and deep polymicrogyric sulci bilaterally

References:

1. Marín O, Rubenstein JL. A long, remarkable journey: Tangential migration in the telencephalon, Nat Rev Neurosci. 2001;2(11):780 – 90

2. Loopuijt LD, Villablanca JR. Increase in size of the caudate nucleus of the cat after a prenatal neocortical lesion, Brain Res Dev Brain Res. 1993;71(1):59 – 68

3. Shepherd GM. Corticostriatal connectivity and its role in disease, Nat Rev Neurosci. 2013;14(4):278 – 91

4. Kaido T. et al. Novel pathological abnormalities of deep brain structures including dysplastic neurons in anterior striatum associated with focal cortical dysplasia in epilepsy, J Neurosurg Pediatr. 2012;10(3):217 – 25.

5. Barkovich AJ et al. Classification system for malformations of cortical development, Neurology. 2001;57(12):2168 – 78