Congenital microcephaly with a simplified gyral pattern: associated findings and their significance

Abstract

Background and purpose: Primary microcephaly is an incompletely understood malformation that is often associated with developmental brain anomalies, yet whether the associated anomalies result from the microcephaly itself or from associated developmental/genetic mishaps is not yet understood. This study reviewed and analyzed a large number of MR imaging scans of children with microcephaly to determine the frequency of associated morphologic findings and to assess whether these findings were associated with the severity of the microcephaly.

Materials and methods: MR images of 119 patients with clinically diagnosed microcephaly were retrospectively reviewed, focusing on the degree of microcephaly, simplification of gyri, white matter volume, abnormalities of the corpus callosum, size and structure of posterior fossa contents, and myelination. Associations among the findings were evaluated by using the Spearman correlation coefficient and the Fisher exact test.

Results: Among 7 patients with mild, 42 with moderate, and 70 with extreme microcephaly, a significant correlation was identified between a greater degree of microcephaly and both a greater degree of simplified gyration and decreased white matter volume. The severity of the callosal anomaly showed a lower but still significant correlation with the severity of microcephaly. Degree of hypoplasia of posterior fossa structures, delay in myelination, and abnormality of the basal ganglia did not correlate with the degree of microcephaly.

Conclusions: A strong correlation was found between the degree of microcephaly, the volume of white matter, and the presence of a simplified gyral pattern. These associations should be considered when attempting to use neuroimaging for segregation and classification of patients with microcephaly.

Fig 1.

A 14-year-old boy with microcephaly and developmental delay. A, Sagittal T1-weighted image shows extreme microcephaly. The corpus callosum is fully formed but appears diffusely thin. B, Axial T1-weighted image shows a mildly simplified gyral pattern with normal cortical thickness. C, Coronal T2-weighted image shows a disproportionally large cerebellum.

Fig 2.

A 10-year-old girl with microcephaly. A, Sagittal T1-weighted image shows extreme microcephaly. The corpus callosum is fully formed but diffusely thin. B and C, Axial T2-weighted images show a moderately simplified gyral pattern with too few sulci but normal cortical thickness (measured at <3 mm). Symmetric posterior horn−dominant lateral ventricular enlargement is shown. White matter volume is severely reduced. D, Coronal T2-weighted image shows a disproportionally large cerebellum.

Fig 3.

A 1-month-old girl with microcephaly, global developmental delay, and seizures. A, Sagittal T1-weighted image shows extreme microcephaly. The corpus callosum is partially formed, the rostrum is absent, and other parts (genu, body, and splenium) are diffusely thin. B, Axial T2-weighted image shows a severely simplified gyral pattern; sulci are both too few and too shallow. Although myelination is shown in the posterior limb of the internal capsule, the abnormal high intensity of the white matter is observed diffusely and the volume of the white matter is severely diminished. C, Coronal T2-weighted image shows a disproportionally large cerebellum.

Fig 4.

A 2-week-old boy with profound microcephaly. A, Sagittal T1-weighted image shows extreme microcephaly with absence of the corpus callosum. All structures seem proportionately affected. B, Axial T2-weighted image shows a severely simplified gyral pattern (almost no sulci). The volume of white matter is also extremely reduced proportional to the simplification of the gyral pattern, and the pericerebral spaces are enlarged.