Rett syndrome is a neurodegenerative disease of unknown etiology that begins early childhood with autism-like behavior and loss of language skills, and progresses with deterioration of the motor system. Autopsy reveals global hypoplasia in both gray and white matter, which suggests developmental arrest. Increased glutamate in the CSF is reported ⁽³⁴⁾. MRI shows cerebral hypoplasia, especially in the frontal lobes, and cerebellar atrophy (Figure 14) ⁽³⁵⁾. MRS shows increased choline and decreased NAA. Increased glucose uptake on FDG PET scans and increased glutamate in the CSF suggest that an excitotoxic mechanism plays an important role in Rett syndrome ⁽³⁶⁾.

Figure 14. A 24-year-old female who has a history of autism, seizures and progression of spastic gait for ten years. Clinically uspected Rett syndrome.

A. T2WI shows cerebral hypoplasia, especially in bilateral frontal lobes, and secondary skull thickening.

B. Sagittal T1WI also shows a thin corpus callosum related to cerebral hypoplasia and skull thickening. Cerebellar atrophy is not prominent in this case.