Evolving unilateral thalamic lesion in Phelan–McDermid syndrome: 7-year follow-up MRI and literature review

Abstract Purpose Phelan–McDermid syndrome is a rare genetic disorder caused by Shank3 protein deficiency, resulting from rearrangements of chromosome 22q13.3 in the region containing the SHANK3 gene. Shank proteins serve as pivotal scaffolding proteins in the postsynaptic density of excitatory synapses in the mammalian brain. Clinical features of Phelan–McDermid syndrome include global developmental delay, hypotonia, impaired language, dysmorphic features, sleep disturbances, and epileptic seizures. Brain magnetic resonance imaging (MRI) findings are typically limited and nonspecific. To our knowledge, no previous report has described an evolving unilateral thalamic focal lesion, its biopsy, and concomitant white matter changes as demonstrated by diffusion tensor imaging (DTI). Methods A 7-year clinical and MRI follow-up was conducted. At age 5, the patient exhibited emerging symptoms, including attention deficit and language impairment, prompting an array-comparative genomic hybridization analysis. MRI examinations included standard morphological sequences as well as advanced techniques such as DTI, spectroscopy, dynamic contrast enhancement, and dynamic susceptibility contrast perfusion imaging. A biopsy of the lesion was performed, and fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) of various brain structures were analyzed. Results Magnetic resonance spectroscopy revealed alterations in the ratios of choline/creatine, myo-inositol/creatine, and N-acetylaspartate/creatine in the evolving right thalamic lesion. Significant differences in DTI parameters were observed only in the right posterior thalamic radiation. Histopathological analysis of the biopsy did not demonstrate any malignant cellular elements. Conclusions In Phelan–McDermid syndrome, a unilateral, evolving focal thalamic lesion has not been previously described. Effective management of this condition necessitates comprehensive data collection to gain unique insights into this complex and rare syndrome.