Pachygyria

Findings

CT (Figure 1) and MR (Figure 2) imaging demonstrate the classic patterns of pachygyria, including:
- Smooth and markedly thickened cortex (Figure 1 and Figure 2)
- Broad, flat gyri with shallow sulci (focal or widespread)
- Vertically-oriented and shallow Sylvian fissures
- “Figure-of-eight” appearance of the brain on axial imaging


Diagnosis: Pachygyria


The findings in this case are consistent with pachygyria, which falls under the classification of an embryologic neuronal migration disorder. With pachygyria (synonymous with incomplete lissencephaly), there are focal areas of broad, flat gyri interrupted by a smooth and markedly thickened cortex. The etiology in some cases is linked to genetic abnormality, including mutations in chromosome 17 or Xq22, while others demonstrate no genetic abnormalities. Alternative etiologies for the development of this disorder include intrauterine insult (ischemic, metabolic, or viral such as CMV) during the 12th to 24th week of embryologic development. This results in damage to the germinal matrix and radial glial cells. Radial glial cells act as mechanical guides by which neurons are transported to the outer cortex during development. Damage to these cells results in subsequent malfunction of neuronal cell migration to the outer cortex.


Clinical findings

Onset and severity of symptoms varies, depending on the amount of cortical involvement. However, muscle spasms, hyperreflexia, refractory epilepsy, developmental delay, and mental retardation are common in children afflicted with the disorder.


Radiographic findings

Although CT is adequate in making the diagnosis, as in this case, MRI is more effective in evaluating and differentiating between neuronal migration disorders.

CT and MR imaging demonstrate the classic patterns of pachygyria, including:
- Smooth and markedly thickened cortex
- Broad, flat gyri with shallow sulci (focal or widespread)
- Vertically oriented and shallow Sylvian fissures
- “Figure-of-eight” appearance of the brain on axial imaging