Clinical History
A 15-month-old female baby was brought to us by her mother with complaints of frequent seizures and muscular hypotonia since birth. She was taken to multiple nearby medical clinics. She was then referred to a tertiary hospital where she was advised to undergo plain CT scan of the brain.
Imaging Findings
Plain CT of the brain revealed smooth thickened cortex (agyria) along with scanty white matter involving temporo-parietal and occipital lobes, associated with band heterotopia (Fig. 1 and 2).
There are widened thickened gyri (pachygyria) noted in frontal lobes with presence of intact white matter (Fig. 2).
These are forming a "hour glass"-shaped cerebral contour (Fig.3).
Ventricles appear dilated and dystrophic (Fig. 3). There is further evidence of hypoplasia of splenium of corpus callosum and pons (Fig 1).
Discussion
DISCUSSION
The lissencephaly-pachygyria spectrum is a rare brain disorders where the whole or parts of the surface of the brain appear smooth, characterised by absent or minimal sulcation [1].
Lissencephaly is caused by defective neuronal migration during embryonic development [4].
Lissencephaly-pachygyria is characterise as:
1. Type I (classic) lissencephaly
2. Type II (cobblestone) lissencephaly
The pattern of inheritance depends on the gene abnormality. The severity gradient in lissencephaly type I predicts whether the affected gene is LIS1 (posterior greater than anterior) or DCX (anterior greater than posterior). [5]
- LIS1 (acquired) accounting for 50% of all cases, with a posterior to anterior gradient of most typical pattern being agyria in the occipital regions transitioning to pachygyria in the frontal regions. [5]
-DCX (X-linked) accounting for 10% of all cases, with an anterior to posterior gradient of agyria in the frontal or midfrontal regions, transitioning to pachygyria in the occipital lobes.
CLINICAL FEATURES
Presentation will vary from patient to patient. [1, 4]
In type I lissencephaly, there is marked hypotonia, seizures and difficulty feeding.
In type II lissencephaly, there is developmental delay, hypotonia and ocular abnormalities.
IMAGING FEATURES
Lissencephaly can be identified on all modalities (antenatal and neonatal ultrasound, CT and MRI). MRI is the modality of choice. [3].
CT demonstrated the main features [3]
(1) a cerebral surface that is agyric or agyric with pachygyric areas.
(2) a cerebral contour that appears as "hour glass" due to lack of or incomplete opercularisation of the brain.
(3) an abnormal gray-white-matter distribution in the cerebral hemispheres (hypomyelination).
Type I (classic) lissencephaly can appear as the classic hour glass or figure-8 appearance or with a few poorly formed gyri (pachygyria) and a smooth outer surface usually associated with band heterotopia.
Type II lissencephaly has a microlobulated surface referred to as a cobblestone complex. Band heterotopia is not evident and the cortex is thinner than in type I. [1]
OUTCOME
Lissencephaly can’t be reversed. Treatment aims to support and comfort affected children. The prognosis depends on the degree of brain malformation. Many will die before the age of 10 years. [4]
TAKE HOME MASSAGE
Lissencephaly is a rare congenital malformation of the brain that has characteristic radiographic features. MRI is the modality of choice while CT scan establishes the diagnosis [2]
Differential Diagnosis List
Type I classical lissencephaly with posterior to anterior gradient.
Polymicrogyria
Lissencephaly Type II
Final Diagnosis
Type I classical lissencephaly with posterior to anterior gradient.
