GM2 gangliosidosis variant B1

Abstract

Variant B1 is a rare type of GM2 gangliosidosis. Clinically, it shows a wide spectrum of forms ranging from infantile to juvenile. We report the first magnetic resonance imaging (MRI) findings from three patients affected by GM2 gangliosidosis variant B1, two presenting with the infantile form and one with the juvenile form. The MRI appearances of the two patients with the infantile form disease are congruent with those reported for the early-onset type of both Tay-Sachs and Sandhoff diseases, and are characterized by early involvement of the basal ganglia and thalamus with cortical atrophy appearing later. In contrast, the patient with the juvenile form of variant B1 showed progressive cortical and white-matter atrophy of the supratentorial structures and, to a lesser extent, the infratentorial structures. No basal ganglia or thalamic anomalies were observed. Because in the adult forms of both Tay-Sachs and Sandhoff diseases a progressive cerebellar atrophy represents the only abnormality detectable, it appears that an MRI pattern peculiar to GM2 gangliosidosis can be defined. This pattern ranges from the basal ganglia injury associated with the early and severe demyelination process noted in the infantile form of the disease, to cerebellar atrophy with no supratentorial anomalies in the adult form. An "intermediate" MRI picture, with cortical atrophy and mild cerebellar atrophy, but without basal ganglia impairment, can be observed in the juvenile form. In addition, our investigations suggest that MRI abnormalities in GM2 gangliosidosis correlate with the clinical form of the disease rather than with the biochemical variant of the enzymatic defect.

Neuroradiological findings in GM2 gangliosidosis variant B1

“…The MRI studies of patients with GM2 gangliosidosis variant B1 do not differ from those with the Tay-Sachs-variant B and Sandhoff diseases, and they reflect the pathological findings of neuronal cytoplasmic distention, demyelination, and gliosis involving the white matter. [3] However, the process of white-matter demyelination seems to be more rapid and extensive in GM2 gangliosidosis-variant B1, involving the internal, medial, and lateral medullary laminae as seen in our case and reported by Grosso et al . [3] Both in the Tay-Sachs (variants B and B1) and Sandhoff diseases, the thalami demonstrates symmetrical hyperdensity on CT, and hyper/hypo-signal intensity on T1/T2-weighted MR images, respectively.…”

“…[3] However, the process of white-matter demyelination seems to be more rapid and extensive in GM2 gangliosidosis-variant B1, involving the internal, medial, and lateral medullary laminae as seen in our case and reported by Grosso et al . [3] Both in the Tay-Sachs (variants B and B1) and Sandhoff diseases, the thalami demonstrates symmetrical hyperdensity on CT, and hyper/hypo-signal intensity on T1/T2-weighted MR images, respectively. These density/intensity changes in the thalami and mesial temporal lobe gyri probably reflect the accumulation of calcium and GM2 ganglioside.…”

“…[3] However, the proton MR spectroscopy findings are still not known. The MRI studies of patients with GM2 gangliosidosis variant B1 do not differ from those with the Tay-Sachs-variant B and Sandhoff diseases, and they reflect the pathological findings of neuronal cytoplasmic distention, demyelination, and gliosis involving the white matter.…”

“…Furthermore, our imaging findings were also compatible with those reported for the GM2 gangliosidosis variant B1 by Grosso et al . [3]…”

Central ocular motor disorders, including gaze palsy and nystagmus

“…Furthermore, patients present with cerebellar ataxia with postural instability, and extrapyramidal symptoms. Psychiatric disorders, including psychotic episodes, depression, and cognitive decline, may occur as part of the clinical picture [43, 44]. Previous MRI studies have shown cerebellar atrophy as a morphological correlate [43].…”