Lissencephaly-pachygyria Masquerading as Leukodystrophy on Magnetic Resonance Imaging Brain.

A 15-month-old male child, 1st born to nonconsanguineous parents, presented with global developmental delay, from the beginning. At the time of presentation, he had wobbly head holding with inability to turn over the abdomen. There was presence of social smile, and he could only produce cooing sounds. There was neither history of seizure nor any vision or hearing-related concerns. Examination revealed microcephaly without any facial dysmorphism or neurocutaneous markers. There was hypotonia (both axial and appendicular) with brisk deep tendon reflexes but no cranial nerve deficit. MRI brain revealed posterior predominant lissencephaly (LIS) – pachygyria [Figure 1] with the typical “tigroid pattern” on axial MRI [Figure 2] marked by symmetric diffuse high-signal intensity on T2-weighted images in the cerebral white matter with radially oriented stripes of low-signal intensity suggesting a leukodystrophy [Figure 1]. Serum creatine phosphokinase levels were within normal limits. In the absence of other associated features, and brisk deep tendon reflexes, the diagnosis of congenital muscular dystrophy, which may be associated with pachygyria, was unlikely. Genetic analysis by exome sequencing revealed homozygous pathogenic frameshift mutation involving LIS1 gene c. 165dupA. The typical “tigroid pattern” on axial MRI or “leopard pattern” on the sagittal view has been classically described in leukodystrophies such as Pelizaeus–Merzbacher disease, Krabbe disease, or Metachromatic leukodystrophy.[1] However, the tigroid pattern has been reported in LIS with cerebellar hypoplasia by Kono et al.[2] and in frontal predominant pachygyria by Roy et al.[3] Malformations of cortical development and myelination abnormalities are not mutually exclusive, and it has been suggested that genes responsible for neuronal migration may also be involved in white matter formation.[2]

Figure 1

Magnetic resonance imaging brain (a) T2-weighted axial image showing lissencephaly posteriorly and pachygyria anteriorly with prominent deep white matter signal changes with radial striping suggesting a leukodystrophy; (b) T2 sagittal and (c) coronal image also show similar appearance in deep white matter, along with lissencephaly-pachygyria pattern

Figure 2

Magnetic resonance imaging brain T1 axial section (a and b) shows tiny hypointensities in hyperintense deep white matter suggesting perivascular sparing of white matter involvement, giving rise to the “tigroid pattern”

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